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   2293篇
  免费   38篇
教育   1645篇
科学研究   127篇
各国文化   22篇
体育   349篇
文化理论   50篇
信息传播   138篇
  2023年   21篇
  2022年   40篇
  2021年   44篇
  2020年   96篇
  2019年   155篇
  2018年   201篇
  2017年   178篇
  2016年   161篇
  2015年   127篇
  2014年   95篇
  2013年   498篇
  2012年   92篇
  2011年   57篇
  2010年   48篇
  2009年   38篇
  2008年   42篇
  2007年   42篇
  2006年   43篇
  2005年   28篇
  2004年   21篇
  2003年   31篇
  2002年   13篇
  2001年   27篇
  2000年   18篇
  1999年   8篇
  1998年   10篇
  1997年   9篇
  1996年   14篇
  1995年   19篇
  1994年   15篇
  1993年   8篇
  1992年   9篇
  1990年   8篇
  1989年   11篇
  1988年   3篇
  1987年   6篇
  1986年   5篇
  1985年   7篇
  1981年   3篇
  1980年   3篇
  1979年   4篇
  1978年   4篇
  1977年   4篇
  1976年   8篇
  1974年   8篇
  1972年   6篇
  1956年   4篇
  1872年   4篇
  1871年   2篇
  1870年   4篇
排序方式: 共有2331条查询结果,搜索用时 421 毫秒
91.
Knowledge Management Research & Practice - Nowadays knowledge has become a key asset for firms in order to build a sustainable competitive advantage. The environment changes quickly and...  相似文献   
92.
Microfluidic devices allow for the production of physiologically relevant cellular microenvironments by including biomimetic hydrogels and generating controlled chemical gradients. During transport, the biomolecules interact in distinct ways with the fibrillar networks: as purely diffusive factors in the soluble fluid or bound to the matrix proteins. These two main mechanisms may regulate distinct cell responses in order to guide their directional migration: caused by the substrate-bound chemoattractant gradient (haptotaxis) or by the gradient established within the soluble fluid (chemotaxis). In this work 3D diffusion experiments, in combination with ELISA assays, are performed using microfluidic platforms in order to quantify the distribution of PDGF-BB and TGF-β1 across collagen and fibrin gels. Furthermore, to gain a deeper understanding of the fundamental processes, the experiments are reproduced by computer simulations based on a reaction-diffusion transport model. This model yields an accurate prediction of the experimental results, confirming that diffusion and binding phenomena are established within the microdevice.  相似文献   
93.
This study aimed to analyse the effect of growth during a summer break on biomechanical profile of talented swimmers. Twenty-five young swimmers (12 boys and 13 girls) undertook several anthropometric and biomechanical tests at the end of the 2011–2012 season (pre-test) and 10 weeks later at the beginning of the 2012–2013 season (post-test). Height, arm span, hand surface area, and foot surface area were collected as anthropometric parameters, while stroke frequency, stroke length, stroke index, propelling efficiency, active drag, and active drag coefficient were considered as biomechanical variables. The mean swimming velocity during an all-out 25 m front crawl effort was used as the performance outcome. After the 10-week break, the swimmers were taller with an increased arm span, hand, and foot areas. Increases in stroke length, stroke index, propelling efficiency, and performance were also observed. Conversely, the stroke frequency, active drag, and drag coefficient remained unchanged. When controlling the effect of growth, no significant variation was determined on the biomechanical variables. The performance presented high associations with biomechanical and anthropometric parameters at pre-test and post-test, respectively. The results show that young talented swimmers still present biomechanical improvements after a 10-week break, which are mainly explained by their normal growth.  相似文献   
94.
Ice hockey requires rapid transitions between skating trajectories to effectively navigate about the ice surface. Player performance relates in large part to effective change-of-direction manoeuvres, but little is known about how those skills are performed mechanically and the effect of equipment design on them. The purpose of this study was to observe the kinetics involved in those manoeuvres as well as to compare whether kinetic differences may result between two skate models of varying ankle mobility. Eight subjects with competitive ice hockey playing experience performed rapid lateral (90°) left and right change-of-direction manoeuvres. Kinetic data were collected using force strain gauge transducers on the blade holders of the skates. Significantly greater forces were applied by the outside skate (50–70% body weight, %BW) in comparison to the inside skate (12–24%BW, p < 0.05). Skate model and turn direction had no main effect, though significant mixed interactions between leg side (inside/outside) with skate model or turn direction (p < 0.05) were observed, with a trend for left-turn dominance. This study demonstrates the asymmetric dynamic behaviour inherent in skating change-of-direction tasks.  相似文献   
95.
Abstract

The aim was to examine the injuries sustained by Spanish football players in the First Division and to compare injury-related variables in the context of both competition and training. The injury data were prospectively collected from 16 teams (427 players) using a specific web-based survey during the 2008/2009 season. A total of 1293 injuries were identified (145 were recurring injuries). The overall injury incidence was 5.65 injuries per 1000 h of exposure. Injuries were much more common during competition than during training (43.53 vs. 3.55 injuries per 1000 h of exposure, P < 0.05). Most of the injuries (89.6%) involved the lower extremities, and overuse (65.7%) was the main cause. Muscle and tendon injuries were the most common types of injury (53.8%) among the players. The incidence of training injuries was greater during the pre-season and tended to decrease throughout the season, while the incidence of competition injuries increased throughout the season (all P < 0.05). In conclusion, the results of this study suggest the need for injury prevention protocols in the First Division of the Spanish Football League to reduce the number of overuse injuries in the muscles and tendons in the lower extremities. In addition, special attention should be paid during the pre-season and the competitive phase II (the last four months of the season) in order to prevent training and competition injuries, respectively.  相似文献   
96.
97.
In the time between its founding and the fall of the wall in November 1989, more than three million people left the German Democratic Republic, many of them illegally and under dangerous circumstances. The party leadership perceived this mass exodus of its citizens as one of the major threats for the real socialist regime.1?1. Bispinck Bispinck, Henrick. “Republikflucht. Flucht und Ausreise als Problem der DDR-Führung.” Vor dem Mauerbau. Politik und Gesellschaft der DDR in den Fünfziger Jahren, edited by MichaelSchwartz and Hermann Wentker, 285309. München: Oldenbourg Wissenschaftsverlag, 2003. [Google Scholar], “Republikflucht.”‘Republikflucht’, as this move from East to West was called by the party leadership, was the reason for the two most important hiatuses in Eastern German history: the first result was that the SED leadership built the wall in August 1961. Many years later, in the fall of 1989, the situation culminated, when a flood of desperate refugees tried to escape to the Federal Republic of Germany via Hungary, Poland and Czechoslovakia, thus effectively hurrying along the regime's demise. The world of sports, too, was considerably affected by this phenomenon. The following essay shall offer a short historical summary of the different reasons and routes Eastern German top athletes chose for their escape. Examples from various decades show that in spite of individual circumstances certain similarities in pattern can be made out, especially in respect to the way the government dealt with these cases of ‘treason’.  相似文献   
98.
99.
In this study the origin and evolution of the meanings of the concepts 'amount of substance' and 'mole' are described. Serious disagreements about these concepts amongst chemistry teachers and the recommendations of the international scientific community are identified. Attention is also drawn to the didactic implications that these epistemological difficulties may have for the teaching of chemistry.  相似文献   
100.
Recent research has demonstrated that slight increases of inter-letter spacing have a positive impact on skilled readers' recognition of visually presented words. In the present study, we examined whether this effect generalises to young normal readers and readers with developmental dyslexia, and whether increased inter-letter spacing affects the reading times and comprehension of a short text. To that end, we conducted a series of lexical decision and continuous reading experiments in which words were presented with the default settings or with a small increase in inter-letter spacing. Increased spacing produced shorter word identification times not only with adult skilled readers (Experiment 1), but also with young normal readers (Grade 2 and Grade 4 children; Experiment 2) and, even to a larger degree, with readers with dyslexia (Experiments 3 and 4). These experiments suggest that slight increases in inter-letter spacing would improve the readability of texts aimed at children, especially those with dyslexia.  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