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   15519篇
  免费   211篇
  国内免费   7篇
教育   11297篇
科学研究   1312篇
各国文化   92篇
体育   1315篇
综合类   7篇
文化理论   94篇
信息传播   1620篇
  2021年   115篇
  2020年   193篇
  2019年   322篇
  2018年   420篇
  2017年   435篇
  2016年   378篇
  2015年   239篇
  2014年   325篇
  2013年   2925篇
  2012年   333篇
  2011年   397篇
  2010年   246篇
  2009年   247篇
  2008年   353篇
  2007年   262篇
  2006年   342篇
  2005年   219篇
  2004年   212篇
  2003年   203篇
  2002年   235篇
  2001年   340篇
  2000年   317篇
  1999年   280篇
  1998年   141篇
  1997年   177篇
  1996年   179篇
  1995年   183篇
  1994年   159篇
  1993年   177篇
  1992年   248篇
  1991年   221篇
  1990年   217篇
  1989年   258篇
  1988年   256篇
  1987年   215篇
  1986年   212篇
  1985年   229篇
  1984年   205篇
  1983年   242篇
  1982年   177篇
  1981年   172篇
  1980年   164篇
  1979年   243篇
  1978年   189篇
  1977年   172篇
  1976年   150篇
  1975年   133篇
  1974年   125篇
  1973年   131篇
  1971年   114篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
With the rise of microfluidics for the past decade, there has come an ever more pressing need for a low-cost and rapid prototyping technology, especially for research and education purposes. In this article, we report a rapid prototyping process of chromed masks for various microfluidic applications. The process takes place out of a clean room, uses a commercially available video-projector, and can be completed in less than half an hour. We quantify the ranges of fields of view and of resolutions accessible through this video-projection system and report the fabrication of critical microfluidic components (junctions, straight channels, and curved channels). To exemplify the process, three common devices are produced using this method: a droplet generation device, a gradient generation device, and a neuro-engineering oriented device. The neuro-engineering oriented device is a compartmentalized microfluidic chip, and therefore, required the production and the precise alignment of two different masks.  相似文献   
82.
Research in Higher Education - Since the turn of the twenty-first century, going to college has become increasingly financially difficult in the United States. Tuition prices continued to rise,...  相似文献   
83.
84.
85.
At the University of Maine, middle and high school teachers observed more than 250 university science, technology, engineering, and mathematics classes and collected information on the nature of instruction, including how clickers were being used. Comparisons of classes taught with (n = 80) and without (n = 184) clickers show that, while instructional behaviors differ, the use of clickers alone does not significantly impact the time instructors spend lecturing. One possible explanation stems from the observation of three distinct modes of clicker use: peer discussion, in which students had the opportunity to talk with one another during clicker questions; individual thinking, in which no peer discussion was observed; and alternative collaboration, in which students had time for discussion, but it was not paired with clicker questions. Investigation of these modes revealed differences in the range of behaviors, the amount of time instructors lecture, and how challenging the clicker questions were to answer. Because instructors can vary their instructional style from one clicker question to the next, we also explored differences in how individual instructors incorporated peer discussion during clicker questions. These findings provide new insights into the range of clicker implementation at a campus-wide level and how such findings can be used to inform targeted professional development for faculty.  相似文献   
86.
87.
The United Kingdom's Department for Education has recently changed the nature of the AS‐level examinations normally taken by students aspiring to enter higher education degree courses one year into their post‐compulsory education. In the face of protests from universities and other institutions that this would both harm students’ progression towards the A‐level qualifications, on which entry to English universities is normally based, and make it difficult for universities determining which of their applicants were best placed to benefit from their degree courses, the Department conducted research which it claimed showed that degree outcome could be predicted as well from the results of GCSE examinations taken one year before AS‐levels as from AS‐levels themselves. This paper critiques those analyses and their conclusions showing, through a re‐analysis and extended interpretation of the Department's data, that AS‐levels provide a more reliable predictor of degree performance in 2011 than GCSEs and that many students who performed better at AS‐level than at GCSE gained a place, and performed well, at a university with high entrance standards.  相似文献   
88.
89.
Research suggests that spatial ability may predict success in complex disciplines including anatomy, where mastery requires a firm understanding of the intricate relationships occurring along the course of veins, arteries, and nerves, as they traverse through and around bones, muscles, and organs. Debate exists on the malleability of spatial ability, and some suggest that spatial ability can be enhanced through training. It is hypothesized that spatial ability can be trained in low-performing individuals through visual guidance. To address this, training was completed through a visual guidance protocol. This protocol was based on eye-movement patterns of high-performing individuals, collected via eye-tracking as they completed an Electronic Mental Rotations Test (EMRT). The effects of guidance were evaluated using 33 individuals with low mental rotation ability, in a counterbalanced crossover design. Individuals were placed in one of two treatment groups (late or early guidance) and completed both a guided, and an unguided EMRT. A third group (no guidance/control) completed two unguided EMRTs. All groups demonstrated an increase in EMRT scores on their second test (P < 0.001); however, an interaction was observed between treatment and test iteration (P = 0.024). The effect of guidance on scores was contingent on when the guidance was applied. When guidance was applied early, scores were significantly greater than expected (P = 0.028). These findings suggest that by guiding individuals with low mental rotation ability “where” to look early in training, better search approaches may be adopted, yielding improvements in spatial reasoning scores. It is proposed that visual guidance may be applied in spatial fields, such as STEMM (science, technology, engineering, mathematics and medicine), surgery, and anatomy to improve student's interpretation of visual content. Anat Sci Educ. © 2018 American Association of Anatomists.  相似文献   
90.
In the article we solve path planning task for an agent being multirotor unmanned aerial vehicle (multicopter). We propose an approach of estimating path geometry constraints based on UAV flight dynamics model and control constraints. Than we introduce a new path finding method which takes into consideration those geometry constraints and study this method both theoretically and empirically.  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