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   1215篇
  免费   24篇
  国内免费   12篇
教育   790篇
科学研究   221篇
各国文化   23篇
体育   98篇
综合类   5篇
文化理论   6篇
信息传播   108篇
  2023年   8篇
  2022年   8篇
  2021年   26篇
  2020年   30篇
  2019年   41篇
  2018年   47篇
  2017年   72篇
  2016年   45篇
  2015年   36篇
  2014年   49篇
  2013年   180篇
  2012年   48篇
  2011年   47篇
  2010年   50篇
  2009年   37篇
  2008年   44篇
  2007年   38篇
  2006年   29篇
  2005年   33篇
  2004年   19篇
  2003年   25篇
  2002年   25篇
  2001年   26篇
  2000年   24篇
  1999年   28篇
  1998年   5篇
  1997年   7篇
  1996年   11篇
  1995年   11篇
  1994年   8篇
  1992年   12篇
  1991年   13篇
  1990年   8篇
  1989年   5篇
  1987年   10篇
  1986年   8篇
  1985年   17篇
  1984年   12篇
  1983年   12篇
  1982年   10篇
  1981年   5篇
  1980年   7篇
  1979年   5篇
  1978年   7篇
  1977年   4篇
  1975年   10篇
  1974年   6篇
  1973年   7篇
  1971年   7篇
  1970年   4篇
排序方式: 共有1251条查询结果,搜索用时 871 毫秒
71.
Separation and sorting of biological entities (viruses, bacteria, and cells) is a critical step in any microfluidic lab-on-a-chip device. Acoustofluidics platforms have demonstrated their ability to use physical characteristics of cells to perform label-free separation. Bandpass-type sorting methods of medium-sized entities from a mixture have been presented using acoustic techniques; however, they require multiple transducers, lack support for various target populations, can be sensitive to flow variations, or have not been verified for continuous flow sorting of biological cells. To our knowledge, this paper presents the first acoustic bandpass method that overcomes all these limitations and presents an inherently reconfigurable technique with a single transducer pair for stable continuous flow sorting of blood cells. The sorting method is first demonstrated for polystyrene particles of sizes 6, 10, and 14.5 μm in diameter with measured purity and efficiency coefficients above 75 ± 6% and 85 ± 9%, respectively. The sorting strategy was further validated in the separation of red blood cells from white blood cells and 1 μm polystyrene particles with 78 ± 8% efficiency and 74 ± 6% purity, respectively, at a flow rate of at least 1 μl/min, enabling to process finger prick blood samples within minutes.  相似文献   
72.
This paper presents a calibration method for parallel manipulators using a measurement system specially installed on an external fixed frame. The external fixed frame is important as an error reference for calibration in certain operations, such as in the configuration of a parallel manip- ulator functioning as a machine tool where the workpiece is fixed to a worktable. The pose of the end-effector is mea- sured using three digital indicators installed on the external fixed frame. To enable measurement, the end-effector is assumed to be a plane large enough that all digital indicators could touch. The error is defined as the difference between the theoretical and actual readings of the digital indicators. The geometric parameters of the parallel manipulator are optimized to minimize this error. This calibration method is low cost and feasible for compensating geometric parameter errors for a parallel manipulator. Optimal pose selection for the calibration is achieved using a swarm intelligence search algorithm. The method is implemented on a prototype of a six degrees-of-freedom (DOFs) Gough-Stewart platform constructed to function as a machine tool.  相似文献   
73.
Education and Information Technologies - Online collaborative learning (OCL) has received significant attention, but the ultimate goal of adopting OCL is neglected, especially in higher education...  相似文献   
74.
Education and Information Technologies - Advising students through their study plans is one of the essential steps towards academic success. The matching of students’ needs and courses...  相似文献   
75.
To address the need for more clinical anatomy training in residency education, many postgraduate programs have implemented structured anatomy courses into their curriculum. Consensus often does not exist on specific content and level of detail of the content that should be included in such curricula. This article describes the use of the Delphi method to identify clinically relevant content to incorporate in a musculoskeletal anatomy curriculum for Physical Medicine and Rehabilitation (PM&R) residents. A two round modified Delphi involving PM&R experts was used to establish the curricular content. The anatomical structures and clinical conditions presented to the expert group were compiled using multiple sources: clinical musculoskeletal anatomy cases from the PM&R residency program at the University of Toronto; consultation with PM&R experts; and textbooks. In each round, experts rated the importance of each curricular item to PM&R residency education using a five‐point Likert scale. Internal consistency (Cronbach's alpha) was used to determine consensus at the end of each round and agreement scores were used as an outcome measure to determine the content to include in the curriculum. The overall internal consistency in both rounds was 0.99. A total of 37 physiatrists from across Canada participated and the overall response rate over two rounds was 97%. The initial curricular list consisted of 361 items. After the second iteration, the list was reduced by 44%. By using a national consensus method we were able to objectively determine the relevant anatomical structures and clinical musculoskeletal conditions important in daily PM&R practice. Anat Sci Educ 7: 135–143. © 2013 American Association of Anatomists.  相似文献   
76.
77.
78.
79.
The University of Michigan opened a new medical library in July 1980. The five-story structure combines the library with a learning-resources center. Overall, the building has operated smoothly and has been well accepted. The combining of two facilities designed to support the teaching and learning objectives of the health sciences curriculum will ensure long-term cooperation between them.  相似文献   
80.
In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( +/- ) jump performance (64.7 +/- 2.3 cm) increased significantly (P = 0.02) over the course of the jump condition and was significantly higher (P < 0.001) than for the run-up plus jump condition (58.0 +/- 3.2 cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 +/- 0.24 mmol . l(-1)) than in the jump (2.61 +/- 0.26 mmol . l(-1), P = 0.02) and run-up (2.86 +/- 0.18 mmol . l(-1), P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 +/- 6 beats . min(-1), P = 0.05) and run-up condition (33 +/- 4 beats . min(-1), P = 0.02) than in the jump condition (21 +/- 3 beats . min(-1)). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps.  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