首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   117篇
  免费   4篇
教育   86篇
科学研究   3篇
各国文化   11篇
体育   4篇
文化理论   2篇
信息传播   15篇
  2023年   1篇
  2021年   5篇
  2020年   5篇
  2019年   7篇
  2018年   8篇
  2017年   10篇
  2016年   13篇
  2015年   5篇
  2014年   8篇
  2013年   16篇
  2012年   4篇
  2011年   6篇
  2010年   6篇
  2009年   2篇
  2008年   3篇
  2007年   2篇
  2006年   2篇
  2005年   2篇
  2004年   2篇
  2003年   3篇
  2001年   1篇
  2000年   1篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1987年   1篇
排序方式: 共有121条查询结果,搜索用时 30 毫秒
71.
The UK engineering and technology (E&T) sector is male-dominated, with women facing various cultural and structural barriers in entering and developing their careers within it. Existing research in this area has focused on women’s recruitment or retaining women in employment, but little has addressed women’s transition to industry through the higher education (HE) system. This paper therefore explores women’s experiences of HE in E&T, focusing particularly on the gendered help and support women were found to receive, as well as possible causes and consequences of this behaviour. The research adopts a qualitative design, using semi-structured interviews with women E&T students. The gendered help women received is shown to be something of a ‘poisoned chalice’; although there are sometimes short-term benefits, this is likely to hinder women from progressing in their careers at the same rate as their male peers.  相似文献   
72.
A vacuum compatible microfluidic reactor, SALVI (System for Analysis at the Liquid Vacuum Interface), was employed for in situ chemical imaging of live biofilms using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Depth profiling by sputtering materials in sequential layers resulted in live biofilm spatial chemical mapping. Two-dimensional (2D) images were reconstructed to report the first three-dimensional images of hydrated biofilm elucidating spatial and chemical heterogeneity. 2D image principal component analysis was conducted among biofilms at different locations in the microchannel. Our approach directly visualized spatial and chemical heterogeneity within the living biofilm by dynamic liquid ToF-SIMS.Mapping how metabolic pathways are interconnected and controlled at the subcellular scale within dynamic living systems continues to present a grand scientific challenge. Biofilms, consisting of aggregations of bacterial cells and extracellular polymeric substance (EPS), present an important avenue for deciphering complex microbial communities. During biofilm formation, cells assemble in a secreted polymer milieu of polysaccharides, proteins, glycolipids, and DNA.1,2 Microfluidics provides unprecedented control over flow conditions, accessibility to real-time observation, high-throughput testing, and mimics in vivo biological environments.3 An understanding of the mechanism underlying biofilm formation and the design of advanced microfluidic experiments could address challenges such as interpreting microbial community interactions, biofouling, and resistance to antimicrobial chemicals. However, only a handful of biofilm studies used microfluidic approaches that provided hydrated chemical imaging at high spatial resolution.4–7 Most studies utilized confocal microscopy,4 FTIR spectroscopy,5 or other approaches (e.g., high density interdigitated capacitors7) for biofilm monitoring. Imaging mass spectrometry has been demonstrated in biofilm studies.8,9 A coupled microfluidic-imaging mass spectrometry approach would provide the chemical molecular spatial mapping needed to better address the scientific challenge of biofilms.Recently, we developed a portable microfluidic reactor, System for Analysis at the Liquid Vacuum Interface (SALVI),10,11 which overcame the grand challenge of studying liquids with high volatility and liquid interfaces using surface sensitive vacuum instruments. SALVI enables direct imaging of liquid surfaces using electron or ion/molecular based vacuum techniques. Our microfluidic approach used a polydimethylsiloxane (PDMS) microchannel fully enclosed with a thin silicon nitride (SiN) membrane (100 nm thick). For visualization, 2 μm diameter holes were opened in the SiN membrane in vacuo. These detection windows were dynamically drilled using the time-of-flight secondary ion mass spectrometry (ToF-SIMS) primary ion beam (e.g., Bi+).12Unlike liquid sample holders for transmission electron microscopy and scanning transmission electron microscopy, SALVI is self-contained and portable.13 As a result, it can potentially be used in many finely focused analytical tool with minimal adaptation.10 The analytical performance of SALVI has been demonstrated with a variety of analytes ranging from biology to material sciences.14,15 Unlike most microfluidic applications that are only suitable under ambient conditions (e.g., separations, cell and small amount sample manipulation, and thermal flow-sensors),16–18 SALVI is compatible with both in situ ambient and in vacuo spectroscopy analysis and imaging.19 Biofilms have been successfully cultivated inside the microfluidic channel and imaged using correlative confocal laser scanning microscopy (CLSM) and ToF-SIMS.20Our approach opens a new avenue to study biological sample in their natural state. Although ToF-SIMS has been widely used for providing molecular signatures of organic and biological molecules in complex biological systems21,22 or lipid spatial mapping,23 the vacuum-based ToF-SIMS generally requires solid (either dried24 or cryo treated25) samples. Here, we report ToF-SIMS two dimensional (2D) and three dimensional (3D) chemical images of hydrated biofilms. In situ time and space-resolved identifications of fatty acid (FA) fragments characteristic of Shewanella are illustrated by 3D images reconstructed from the ToF-SIMS depth profile time series. Principal component analysis (PCA) further elucidates biofilm chemical and spatial heterogeneity and shows the key chemical component at different depth and location of the biofilm including the biofilm-surface attachment interface.For all growth experiments, two samples were cultured simultaneously. At days 5 and 6, one sample was harvested for immediate analysis, respectively, using a ToF-SIMS V spectrometer (IONTOF GmbH, Münster, Germany). Similar results were obtained from both samples, because the biofilm-attachment surface was probed. For consistency, only day 6 data are shown here, while additional data are provided in the supplementary material.28 2D and 3D image visualizations were obtained using the IONTOF instrument software. PCA was performed using MATLAB R2012a (MathWorks, Inc., Natick, MA, USA). 2D images of .bif format were converted and integrated into a matrix. Data were pretreated by normalization to total ions, square root transformation, and then mean centering.26 For m/z spectra PCA, unit mass peaks from m/z 199 to m/z 255 were used (see Figure S-228). Unit mass peaks from m/z 1–300 were also used and results are comparable (see Figure S-328). Five characteristic FA peaks (m/z 199, 213, 227, 241, and 255, corresponding to C12, C13, C14, C15, and C16 FAs) were used in image PCA.27 Images representing each PC were reconstructed from the score matrix using the red, green, and blue (RGB) color scale.Using depth profiling, we drilled through the SiN membrane and collected depth-resolved images of the live biofilm (Figure 1(a)). Our analysis of the negative ToF-SIMS spectra after SiN punch-through showed Shewanella FA fragments in the m/z 195–255 range.20 From the depth profile time series, we selected five regions (highlighted as I, II, III IV, and V) within the FA m/z range to visualize 2D spatially resolved images collected for 46 s (1000 scans) before (I), during (II), or after (III, IV, V) SiN membrane punch-through.20 When false color 2D images of FA fragments characteristic of Shewanella biofilms were selected from the dynamic depth profiling data, differences were observed (Figure 1(b)) among the five regions. Furthermore, the biofilm images after SiN membrane punch-through (III, IV, V) displayed variations across the 2 μm diameter surfaces, with C12 (m/z 199) being distributed across regions III, IV, and V and C15 (m/z 241) FAs mostly in region V (see Figure S-4 for additional FA images28). This suggested that depth-resolved chemical heterogeneities were present in the biofilm. To illustrate, we reconstructed the 2D images from depth profiling data within the biofilm region (from the beginning of III through the end of V) and show spatially resolved 3D chemical images within the entire sample (Figure 1(c) and movies S1-S328). The reconstructed 3D images revealed the heterogeneous spatial distribution overlay for C12 (red) and C15 (green) FAs during 302 s biofilm depth profiling from day 5 (Figure S-528) and day 6 (Figure 1(c)).Open in a separate windowFIG. 1.(a) ToF-SIMS depth profiling of the day 6 biofilm attached to the SiN membrane in the microfluidic channel. Five regions representing sample before SiN punch-through (I) during punch-through (II) or within the biofilm region (III, IV, and V) are illustrated. (b) 2D false color images of day 6 biofilm FAs at the five time regions highlighted in (a). (c) Reconstructed 3D day 6 biofilm images showing FA fragment distributions within the entire biofilm region (III–V, 302 s). The time axis represents depth profiling from near the SiN surface into the biofilm. (d) Spectra PCA score plot of day 6 biofilm showing the differences and similarities among selected five regions (m/z 199–255). A 95% confidence limit for each region was defined by an ellipse with the same color to the corresponding region clusters. (e) Loadings of PC1 and PC2 corresponding to (d) and the plot of PC variance contributions.Spectral PCA was used to analyze the m/z spectra. The deepest region (V) into the biofilm was the most different from the other two biofilm regions (III and IV), further confirming the heterogeneities observed in the 2D images (e.g., C12 and C15 FA fragments) contributing most to this spatial difference. In addition, C12 FA fragments played a key role in the biofilms imaged near the SiN membrane attachment surface (III and IV). When inspected individually, C12 FAs were observed throughout the entire biofilm region, suggesting that C12 FA fragments may play a role in biofilm attachment to a surface and they may be main components of EPS throughout the biofilm. In contrast, C15 FAs were more abundant deeper within the biofilm, indicating that they may be more relevant to bacteria cells themselves.Uniform sputtering rate was assumed during depth profiling. To better determine the depth and shape of the SIMS ionization crater, AFM measurements were collected using an agarose sample in the SALVI reactor as a proxy for the biofilms (Figure S-628). The AFM results showed that the 100 nm SiN was drilled through and confirmed that the biofilm interface was probed by ToF-SIMS. Ideally, real-time correlative AFM and ToF-SIMS measurements will be needed due to the self-healing property of biofilms. However, such capability is currently under development.To further analyze chemical differences within biofilms, we performed ToF-SIMS depth profiling at three locations along the microchannel; namely, the inlet, center, and outlet as illustrated in Figure S-1(b).28 At each location, we defined the five regions described in Figure 1(a), and 2D image PCA analysis was conducted on the biofilm region (from the beginning of III through the end of V) to visualize the chemical distributions on day 6. Figure 2(a) shows the loading plots for the m/z peaks that contribute to each PC image (Figure 2(b)). The first three PCs explained 93.79% of the variance within the data. For PC1, the strongest positive loading fragments were C12 and C15 FAs, which are the bright red areas in three PC1 images. The C12 FAs were the main contributor to the green regions in the PC2 image. The strongest loading for PC3 in blue was C14 FAs. Compared to PC1 and PC2, PC3 played a limited contribution to the overall spatial distribution discrimination. The merged images give a demonstration of chemical spatial distribution of key components of biofilms in the liquid microenvironment.Open in a separate windowFIG. 2.(a) Image PCA loading plots illustrating the contribution of each FA peak in the day 6 biofilm at three locations within the microfluidic channel. The variance contributions of each PC are shown at the bottom. (b) Reconstructed false-color 2D PCA images in RGB corresponding to each PC scores at these locations along the microfluidic channel. The RGB composite images of the three key PCs are depicted in the bottom. Only data within the 2 μm diameter circle were considered in analysis.Our results show that SALVI and liquid ToF-SIMS studies of live biofilms offer dynamic, depth-resolved chemical mapping and produce 2D and 3D visualizations of spatial heterogeneity within a biofilm. Chemical imaging of biofilms near the attachment interface can enhance our understanding of biofilm formation in environmental, medical, and industrial settings. Our approach provides a universal portable platform and enables in situ probing of complex living biological systems potentially across multiple time and space scales. Because of the portability and vacuum compatibility, SALVI offers a valuable linkage with proteomic mass spectrometry via microfluidics and a nondestructive package for integrative in situ analysis of live biological systems in system biology.  相似文献   
73.
Cultured Technology: The Internet and Religious Fundamentalism   总被引:1,自引:0,他引:1  
In this article we identify four principal dimensions of religious fundamentalism as they interact with the Internet: hierarchy, patriarchy, discipline, and seclusion. We also develop the concept of cultured technology, and analyze the ways communities reshape a technology and make it a part of their culture, while at the same time changing their customary ways of life and unwritten laws to adapt to it. Later, we give examples for our theoretical framework through an empirical examination of ultra-Orthodox Jewish communities in Israel. Our empirical study is based on a data set of 686,192 users and 60,346 virtual communities. The results show the complexity of interactions between religious fundamentalism and the Internet, and invite further discussions of cultured technology as a means to understand how the Internet has been culturally constructed, modified, and adapted to the needs of fundamentalist communities and how they in turn have been affected by it.  相似文献   
74.
Intimate partner violence, sexual violence, and stalking are pervasive in the United States, and college women are disproportionately affected by this power‐based personal violence (PBPV). Title IX mandates that colleges and universities offer support services to trauma survivors, and college counselors should be prepared to meet this need. Therefore, this article serves to explore a diverse assortment of trauma‐informed counseling techniques, based in feminist theory, for college counselors working with PBPV survivors.  相似文献   
75.
Learning to integrate multiple information sources is vital for advancing learners’ digital literacy. Previous studies have found that learners’ epistemic metacognitive knowledge about the nature of knowledge and knowing is related to their strategic integration performance. The purpose of this study was to understand how these relations come into play as students learn to integrate divergent information sources. To do so, we examined the contribution of scaffolds addressing the epistemic strategy of integration and epistemic metastrategic knowledge about this strategy. Participants were 99 high-achieving Arab Israeli ninth graders. All participants engaged in writing arguments based on divergent information sources. Students in the control condition received no scaffolds; students in the strategic condition received a strategic scaffold; and students in the metastrategic condition received both strategic and metastrategic scaffolds. Integration performance, epistemic metastrategic knowledge about integration, and absolutist, multiplist, and evaluativist epistemic perspectives were measured before, immediately after, and one month after the intervention. At pre-test, both epistemic metastrategic knowledge about integration and evaluativism were positive predictors of integration performance. The strategic scaffold led to a significant increase in integration performance and epistemic metastrategic knowledge. Adding the metastrategic scaffold led to greater improvement in epistemic metastrategic knowledge, but did not result in additional gains in strategic performance. An immediate decrease in absolutism occurred among all participants but was not sustained over time. A decrease in multiplism occurred only in the experimental groups and was sustained over time. The results suggest that epistemic growth can occur in both bottom-up and top-down directions.  相似文献   
76.
77.
Background and purpose: Attentional focus cues have been shown to impact motor performance of adults and children. Specifically, an external focus of attention results in improved motor learning and performance as compared to adopting an internal focus of attention. The purpose of this study was to determine the effects of an internal and external attentional focus cue on children’s object control skill performance during a commonly used motor skill assessment.

Methods: Using a within-participant design, a total of 44 children (Mage?=?7.7 years, 20 boys and 24 girls) completed all three attentional focus conditions. The object control subscale of the Test of Gross Motor Development-2nd Edition (TGMD-2; Ulrich, 2000. Test of Gross Motor Development-2. Austin: Pro-Ed.) served as the motor skill assessment in present study. The TGMD-2 is a normed and criteria-referenced assessment frequently used to assess fundamental motor skill competence in children. The object control subtest of the TGMD-2 assesses a child’s ability to complete six fundamental motor skills – striking a stationary ball, stationary dribble, catch, kick, overhand throw, and underhand roll. All participants completed the object control subtest of the TGMD-2 under three different attentional focus conditions: baseline (i.e. neutral focus), internal, and external. The internal cue focused on movement performance and the external cue focused on movement outcome. In all three conditions, a video demonstration of proper skill performance was used to ensure no difference in visual demonstration, but the overlaying audio was changed to encompass each attentional focus condition. Children’s motor performance was recorded and later coded by a single researcher blinded to the study. A repeated-measures analysis of variance was used to determine if children’s motor scores changed among the three conditions.

Results: Findings demonstrated that children’s performance differed among the three conditions (F(2,43)?=?3.5, p?Post hoc analysis revealed that children scored significantly better in the external cue condition compared to the baseline (difference?=?1.98, p?Conclusion: Children performed better when given a verbal instruction to focus their attention externally rather than a verbal instruction with no attentional focus cue. No significant differences exist between the internal and external focus condition or between the neutral and internal condition. Our findings align with the literature and support that external attentional focus cues have a positive effect on motor performance. From a teaching and learning standpoint, using consistent instructions appears to be essential for young learners. Slight changes in verbal cues can have a significant effect on how well children execute fundamental motor skills.  相似文献   
78.
Objective:An innovative funding scheme for health care librarians to attend an intensive short course in teaching evidence-based practice was established in the West of England in 2016. This evaluation aims to understand the value of the scheme and the impact of the training opportunity for the librarians, establish an evidence base for continuing with the funding scheme, and inform the development of plans to build additional capacity among health care librarians to provide critical appraisal training.Methods:Seven librarians working in health care system settings were funded by the scheme between 2016 and 2018. Post-course feedback forms gathered initial views on course content and delivery, which informed the development of questions for the qualitative phase of the evaluation. All seven librarians participated in group discussions and individual interviews.Results:The course boosted confidence, provided valuable new skills, and positively impacted careers of the librarians through access to new opportunities. It inspired the development of new approaches to critical appraisal training. An important need was identified among the librarians for more education in teaching. Librarians funded by the scheme have successfully cascaded the training to their colleagues.Conclusion:This evaluation supports the continuation of the funding scheme to further build capacity among health care librarians to teach evidence-based practice. It suggests additional investment in this type of specialist training, as well as in education in teaching skills, would be beneficial for health care librarians. Evidence from this evaluation is informing new plans to support these professionals with the vital service they provide, which contributes to the evidence-based culture of their organizations and to patient outcomes.  相似文献   
79.
80.
About half of 2,581 low-income mothers reported reading daily to their children. At 14 months, the odds of reading daily increased by the child being firstborn or female. At 24 and 36 months, these odds increased by maternal verbal ability or education and by the child being firstborn or of Early Head Start status. White mothers read more than did Hispanic or African American mothers. For English-speaking children, concurrent reading was associated with vocabulary and comprehension at 14 months, and with vocabulary and cognitive development at 24 months. A pattern of daily reading over the 3 data points for English-speaking children and daily reading at any 1 data point for Spanish-speaking children predicted children's language and cognition at 36 months. Path analyses suggest reciprocal and snowballing relations between maternal bookreading and children's vocabulary.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号