全文获取类型
收费全文 | 121篇 |
免费 | 3篇 |
专业分类
教育 | 83篇 |
科学研究 | 14篇 |
各国文化 | 2篇 |
体育 | 12篇 |
文化理论 | 6篇 |
信息传播 | 7篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 15篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 17篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1996年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 296 毫秒
21.
Reduction of water evaporation in polymerase chain reaction microfluidic devices based on oscillating-flow 总被引:1,自引:0,他引:1
Alessandro Polini Elisa Mele Anna Giovanna Sciancalepore Salvatore Girardo Adriana Biasco Andrea Camposeo Roberto Cingolani David A. Weitz Dario Pisignano 《Biomicrofluidics》2010,4(3)
Producing polymeric or hybrid microfluidic devices operating at high temperatures with reduced or no water evaporation is a challenge for many on-chip applications including polymerase chain reaction (PCR). We study sample evaporation in polymeric and hybrid devices, realized by glass microchannels for avoiding water diffusion toward the elastomer used for chip fabrication. The method dramatically reduces water evaporation in PCR devices that are found to exhibit optimal stability and effective operation under oscillating-flow. This approach maintains the flexibility, ease of fabrication, and low cost of disposable chips, and can be extended to other high-temperature microfluidic biochemical reactors. 相似文献
22.
Cristina Martins Coelho Maycon Moura Reboredo Felipe Martins Valle Carla Malaguti Larissa Almeida Campos Lucas Mendes Nascimento 《Journal of sports sciences》2018,36(10):1186-1193
Supervised exercise has shown benefits for subjects with asthma, but little is known about the effectiveness of unsupervised physical activity on this population. We investigated the effects of a 12-week unsupervised pedometer-based physical activity program on daily steps and on clinical and psychological parameters of adults with asthma. Clinically stable adults with moderate to severe asthma were encouraged to take daily 30-minute walks and were randomized to pedometer and control groups. The pedometer group received pedometers and individualized daily step targets. Changes in daily steps (average of steps taken during six consecutive days), six-minute walk test (6MWT), health-related quality of life, asthma control and anxiety and depression levels were assessed 12 weeks after intervention and 24–28 weeks after randomization. Thirty-seven participants were recruited and 30 completed the intervention. At 12 weeks, the groups differed significantly in daily steps (adjusted average difference, 2488 steps; 95% confidence interval [CI], 803 to 4172; p = 0.005) and in the 6MWT (adjusted average difference, 21.9 m; 95% CI, 6.6 to 37.3; p = 0.006). These differences were not significant 24–28 weeks after randomization. The program was effective in increasing daily steps of adults with moderate to severe asthma 12 weeks after intervention. 相似文献
23.
ABSTRACTThis study identified clusters of adolescents who share similar cardiorespiratory fitness levels and analysed the relationships between cardiorespiratory fitness, inhibition, and math fluency in each of the clusters. The subjects were 490 high-school students aged 10–16 years. The mean age was 13.82 years (SD = 1.12). Latent class analysis identified three clusters with high, medium, and low levels of cardiorespiratory fitness. The high-fitness cluster achieved higher scores in inhibition and math fluency than the low-fitness cluster. Path analysis revealed that the influence of cardiorespiratory fitness on inhibition was non-existent in the three clusters. The effect of inhibition on math fluency was positive and significant in all three cardiorespiratory fitness levels. Cardiorespiratory fitness had a direct, positive, and significant effect on math fluency only in the high-fitness cluster. Therefore, a high level of cardiorespiratory fitness is a significant determining factor in the explanation of math fluency. These results indicate that inhibition does not mediate the relationship between cardiorespiratory fitness and math fluency. However, the benefits of cardiorespiratory fitness affect math fluency, which has important implications for the educational environment and the teaching/learning process. 相似文献
24.
25.
Young children, ages 5–6 years, develop first beliefs about science and themselves as science learners, and these beliefs are considered important precursors of children's future motivation to pursue science. Yet, due to a lack of adequate measures, little is known about young children's motivational beliefs about learning science. The present two‐part study explores the motivational beliefs of young children using a new measure—the Young Children's Science Motivation (Y‐CSM) scale. Initial measurement development involved a thorough literature review of existing measures, and an extensive piloting phase until a final instrument was reached. To establish scale reliability, measurement invariance as well construct and criterion validity, the final instrument was administered to a new sample of 277 young children, age 5–6 years, in northern Germany. Results reveal that children's motivational beliefs can be empirically differentiated into their self‐confidence and enjoyment in science at this young age. Older children were more motivated in science, but no significant gender differences were found. Importantly, children in preschools with a science focus reported significantly higher science motivation. This finding stresses the importance of early science education for the development of children's motivational beliefs science. 相似文献
26.
Annarilla Ahtola Anne Haataja Antti Kärnä Elisa Poskiparta Christina Salmivalli 《Teaching and Teacher Education》2012
The effects of an antibullying program, KiVa, on Grade 1–3 teachers' perceptions of bullying were investigated. Data were gathered from 128 teachers in 33 intervention schools and 110 teachers in 29 control schools. Two-level regression models showed that, at the end of the intervention year, self-evaluated competence to tackle bullying was at a higher level in the intervention schools than in the control schools. In addition, in the intervention schools, participation in KiVa activities was associated with teacher perceptions of bullying. The need to take teacher and organization perspectives into consideration in future whole-school intervention studies is discussed. 相似文献
27.
28.
Resilience, defined as positive adaptation and functioning following exposure to significant adversity, is an important topic of investigation in child welfare. The current study used data from the Ontario Looking After Children (OnLAC) project to estimate the prevalence of behavioral resilience (i.e., lower frequency of conduct and emotional problems, higher frequency of prosocial behavior) in 531 5–9 year olds living in out-of-home care, and to determine how behaviorally-resilient children are functioning in other domains (i.e., peer relationships and academic performance). Furthermore, hierarchical linear modeling was used to examine the contribution of four levels of analysis (i.e., child, family, child welfare worker, and child welfare agency) on behaviors and to identify the contribution of predictor variables within each of these levels. Findings indicated that 50–70% of children exhibited resilience on one behavioral outcome while approximately 30% showed resilience on at least two of the outcomes. Also, 8.4–9.6% exhibited resilience on one of the behavioral outcomes in addition to peer relationships and academic performance. The child level accounted for the highest proportion of total explained variance in behavioral outcomes, followed by the family-, child welfare worker-, and child welfare agency-levels. A number of child and foster family variables predicted behavioral functioning. Findings indicate that it is important to inquire about children's functioning across multiple domains to obtain a comprehensive developmental assessment. Also, child and foster family characteristics appear to play considerable roles in the promotion of behavioral resilience. 相似文献
29.
Antonio Mauricio F.L. Miranda de S Danton D. Ferreira Edson W. Dias Eduardo M.A.M. Mendes Leonardo B. Felix 《Journal of The Franklin Institute》2009,346(9):841-853
The present work deals with recent results on the sampling distribution of the magnitude-squared coherence (also called just coherence) estimate between a random (Gaussian) and a periodic signal, in order to obtain analytical critical values, alternative expressions for the probability density function (PDF) as well as the variance and bias of the estimate. A comparison with the more general case of coherence estimation when both signals are Gaussian was also provided. The results indicate that the smaller the true coherence (TC) values the closer both distributions become. The behaviour of variance and bias as a function of the number of data segments and the TC is similar for both coherence estimates. Additionally, the effect of a normalizing function (Fisher's z transform) in the coherence estimated between a random and a periodic signal was also evaluated and normality has been nearly achieved. However, the variance was less equalized in comparison with coherence estimate between two Gaussian signals. 相似文献
30.
Most of the literature on university–industry (U–I) linkages assumes that these linkages are beneficial per se. We question this assumption, suggesting that not all such linkages are equally helpful. In this paper, we explore the factors driving the formation of ‘valuable U–I linkages’, conceived as those linkages between universities and firms that have a higher potential to diffuse knowledge to other firms in their regional economy. Our empirical strategy combines case-study methodology with econometric techniques using data from two wine clusters in Chile and in Italy. The firm's knowledge base is found to be a key driver of ‘valuable’ U–I linkages. We conclude that selectivity should be encouraged among policy makers endeavouring to promote U–I linkages. 相似文献