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   3579篇
  免费   63篇
  国内免费   2篇
教育   2505篇
科学研究   197篇
各国文化   72篇
体育   372篇
综合类   2篇
文化理论   24篇
信息传播   472篇
  2023年   13篇
  2022年   26篇
  2021年   49篇
  2020年   77篇
  2019年   150篇
  2018年   188篇
  2017年   196篇
  2016年   159篇
  2015年   98篇
  2014年   129篇
  2013年   758篇
  2012年   110篇
  2011年   107篇
  2010年   92篇
  2009年   101篇
  2008年   107篇
  2007年   92篇
  2006年   81篇
  2005年   69篇
  2004年   64篇
  2003年   60篇
  2002年   52篇
  2001年   48篇
  2000年   45篇
  1999年   36篇
  1998年   47篇
  1997年   41篇
  1996年   30篇
  1995年   23篇
  1994年   26篇
  1993年   35篇
  1992年   35篇
  1991年   34篇
  1990年   35篇
  1989年   43篇
  1988年   21篇
  1987年   35篇
  1986年   18篇
  1985年   13篇
  1984年   16篇
  1983年   22篇
  1982年   16篇
  1981年   16篇
  1980年   20篇
  1979年   18篇
  1978年   16篇
  1977年   21篇
  1974年   14篇
  1973年   12篇
  1971年   11篇
排序方式: 共有3644条查询结果,搜索用时 78 毫秒
991.
This paper presents research with small- and medium-sized enterprise (SME) owners who have participated in a leadership development programme. The primary focus of this paper is on learning transfer and factors affecting it, arguing that entrepreneurs must engage in ‘action’ in order to ‘learn’ and that under certain conditions they may transfer learning to their firm. This paper draws on data from 19 focus groups undertaken from 2010 to 2012, involving 51 participants in the LEAD Wales programme. It considers the literatures exploring learning transfer and develops a conceptual framework, outlining four areas of focus for entrepreneurial learning. Utilising thematic analysis, it describes and evaluates what (actual facts and information) and how (techniques, styles of learning) participants transfer and what actions they take to improve the business and develop their people. This paper illustrates the complex mechanisms involved in this process and concludes that action learning is a method of facilitating entrepreneurial learning which is able to help address some of the problems of engagement, relevance and value that have been highlighted previously. This paper concludes that the efficacy of an entrepreneurial learning intervention in SMEs may depend on the effectiveness of learning transfer.  相似文献   
992.
Although innovation diffusion is a central topic in policy and strategy, its measurement remains difficult – particularly in cases where the innovation is a complex and possibly ambiguous practice. In this paper, we develop four theoretical mechanisms that may bias diffusion markers by leading to the understatement and/or overstatement of diffusion at different points in time. Employing the case of “green chemistry,” we then compare three different diffusion markers – keywords, database index terms, and domain expert assessments – and we demonstrate how they lead to differing conclusions about the magnitude and timing of diffusion, organizational demography, publication outlets, and collaboration. We also provide suggestive evidence of extensive “greenwashing” by particular organization types and in particular countries. Building on these findings, we point to potential challenges with existing diffusion studies, and we make a case for the incorporation of practitioners in construct measurement and for the integration of comparative metrics in diffusion studies.  相似文献   
993.
We report a fundamental study of how the electropermeabilization of a cell is affected by nearby cells. Previous researchers studying electroporation of dense suspensions of cells have observed, both theoretically and experimentally, that such samples cannot be treated simply as collections of independent cells. However, the complexity of those systems makes quantitative modeling difficult. We studied the change in the minimum applied electric field, the threshold field, required to affect electropermeabilization of a cell due to the presence of a second cell. Experimentally, we used optical tweezers to accurately position two cells in a custom fluidic electroporation device and measured the threshold field for electropermeabilization. We also captured video of the process. In parallel, finite element simulations of the electrostatic potential distributions in our systems were generated using the 3-layer model and the contact resistance methods. Reasonably good agreement with measurements was found assuming a model in which changes in a cell''s threshold field were predicted from the calculated changes in the maximum voltage across the cell''s membrane induced by the presence of a second cell. The threshold field required to electroporate a cell is changed ∼5%–10% by a nearby, nearly touching second cell. Cells aligned parallel to the porating field shield one another. Those oriented perpendicular to the field enhance the applied field''s effect. In addition, we found that the dynamics of the electropermeabilization process are important in explaining observations for even our simple two-cell system.  相似文献   
994.
We examined the effects of concomitant increases in crank rate and power output on incremental arm crank ergometry. Ten healthy males undertook three incremental upper body exercise tests to volitional exhaustion. The first test determined peak minute power. The subsequent tests involved arm cranking at an initial workload of 40% peak minute power with further increases of 10% peak minute power every 2 min. One involved a constant crank rate of 70 rev · min(-1), the other an initial crank rate of 50 rev · min(-1) increasing by 10 rev · min(-1) every 2 min. Fingertip capillary blood samples were analysed for blood lactate at rest and exhaustion. Local (working muscles) and cardiorespiratory ratings of perceived exertion (RPE) were recorded at the end of each exercise stage. Heart rate and expired gas were monitored continuously. No differences were observed in peak physiological responses or peak minute power achieved during either protocol. Blood lactate concentration tended to be greater for the constant crank rate protocol (P = 0.06). Test duration was shorter for the increasing than for the constant crank rate protocol. The relationship between local RPE and heart rate differed between tests. The results of this study show that increasing cadence during incremental arm crank ergometry provides a valid assessment of peak responses over a shorter duration but alters the heart rate-local RPE relationship.  相似文献   
995.
The purpose was to evaluate the traditional method, of visually focusing on the ball, in comparison to focusing on the hole, during the putting stroke. The study design consisted of a pretest, a 4-week practice period, and a posttest. Participants (n = 31, handicap: 18.7 ± 10.4) practised using only one of the two gaze techniques. Testing consisted of having all participants putt using both gaze techniques from both a 1.22 m and a 4 m distance. Five putts were executed for each gaze technique/putt length combination for a total of 20 putts in each testing session per participant. The kinematics of every putting stroke executed during testing (1240 strokes) were captured using a TOMI? system. There was a significant improvement in putting success for both groups following practice (P = 0.001). Practising while visually focusing on the hole, resulted in a statistically significant reduction in putter speed variability in comparison to practising while visually focusing on the ball (P = 0.017). Visually focusing on the hole did not meaningfully (nor statistically) affect the quality of impact as assessed by the variability in face angle, stroke path, and impact spot at the precise moment the putter head contacted the ball.  相似文献   
996.
Previous studies on the kinematics of the golf swing have mainly focused on group analysis of male golfers of a wide ability range. In the present study, we investigated gross body kinematics using a novel method of analysis for golf research for a group of low handicap female golfers to provide an understanding of their swing mechanics in relation to performance. Data were collected for the drive swings of 16 golfers using a 12-camera three-dimensional motion capture system and a stereoscopic launch monitor. Analysis of covariance identified three covariates (increased pelvis-thorax differential at the top of the backswing, increased pelvis translation during the backswing, and a decrease in absolute backswing time) as determinants of the variance in clubhead speed (adjusted r (2) = 0.965, P < 0.05). A significant correlation was found between left-hand grip strength and clubhead speed (r = 0.54, P < 0.05) and between handicap and clubhead speed (r = -0.612, P < 0.05). Flexibility measures showed some correlation with clubhead speed; both sitting flexibility tests gave positive correlations (clockwise: r = 0.522, P < 0.05; counterclockwise: r = 0.711, P < 0.01). The results suggest that there is no common driver swing technique for optimal performance in low handicap female golfers, and therefore consideration should be given to individual swing characteristics in future studies.  相似文献   
997.
The aim of this study was to examine the effect of playing formation on high-intensity running and technical performance during elite soccer matches. Twenty English FA Premier League games were analysed using a multiple-camera computerized tracking system (n = 153 players). Overall ball possession did not differ (P < 0.05) between 4-4-2, 4-3-3 and 4-5-1 formations (50%, s = 7 vs. 49%, s = 8 vs. 44%, s = 6). No differences were observed in high-intensity running between 4-4-2, 4-3-3 and 4-5-1 formations. Compared with 4-4-2 and 4-3-3 formations, players in a 4-5-1 formation performed less very high-intensity running when their team was in possession (312 m, s = 196 vs. 433 m, s = 261 vs. 410 m, s = 270; P 5 0.05) but more when their team was not in possession (547 m, s = 217 vs. 461 m, s = 156 vs. 459 m, s = 169; P < 0.05). Attackers in a 4-3-3 performed ~30% more (P < 0.05) high-intensity running than attackers in 4-4-2 and 4-5-1 formations. However, the fraction of successful passes was highest in a 4-4-2 (P < 0.05) compared with 4-3-3 and 4-5-1 formations. The results suggest that playing formation does not influence the overall activity profiles of players, except for attackers, but impacts on very high-intensity running activity with and without ball possession and some technical elements of performance.  相似文献   
998.
The manipulation of ribosomal RNA (rRNA) extracted from E. coli cells by dielectrophoresis (DEP) has been demonstrated over the range of 3 kHz-50 MHz using interdigitated microelectrodes. Quantitative measurement using total internal reflection fluorescence microscopy of the time dependent collection indicated a positive DEP response characterized by a plateau between 3 kHz and 1 MHz followed by a decrease in response at higher frequencies. Negative DEP was observed above 9 MHz. The positive DEP response below 1 MHz is described by the Clausius-Mossotti model and corresponds to an induced dipole moment of 3300 D with a polarizability of 7.8×10(-32) F m(2). The negative DEP response above 9 MHz indicates that the rRNA molecules exhibit a net moment of -250 D, to give an effective permittivity value of 78.5 ε(0), close to that of the aqueous suspending medium, and a relatively small surface conductance value of ~0.1 nS. This suggests that our rRNA samples have a fairly open structure accessible to the surrounding water molecules, with counterions strongly bound to the charged phosphate groups in the rRNA backbone. These results are the first demonstration of DEP for fast capture and release of rRNA units, opening new opportunities for rRNA-based biosensing devices.  相似文献   
999.
Many sport and exercise activities require powerful movements of the upper body. Despite their importance, there is a paucity of research examining stretch-shortening cycle (SSC) activities occurring in the upper limbs. The purpose of this study was to examine the effect of fatigue on throwing performance (height of throw) and biomechanical factors of the upper limbs (reactive strength index; hand contact time) using a specially constructed sledge apparatus for the upper body. Ten male subjects aged between 19 and 21 years performed a series of rebound throws (RBT) in a non-fatigued state to obtain a maximal baseline throw score. Subjects then performed a RBT fatiguing protocol on the upper body sledge followed by further RBT, at 15, 45, 120 and 300-seconds post fatigue. Markers on the subjects' limb and the sledge were analysed using Motion Analysis Corporation 3-D kinematic analysis system (200 Hz). Throwing height, contact time and reactive strength index were determined. Mean throwing height and reactive strength index showed significant decreases following fatigue and increases during recovery (p < 0.05). The results confirm the presence ofpost-activation potentiation (PAP) in RBT performance. This finding could be useful when optimising recovery periods in training or implementing complex training methods.  相似文献   
1000.
ABSTRACT:  Computer-based training is increasingly favored by food companies for training workers due to convenience, self-pacing ability, and ease of use. The objectives of this study were to determine if personal hygiene training, offered through a computer-based method, is as effective as a face-to-face method in knowledge acquisition and improved attitude toward food safety. Employees from four food processing facilities ( n = 94) were randomly assigned to a control group, a face-to-face training group, or a computer-based training group. Evaluation instruments consisted of a pretest and a posttest to measure knowledge gain, a step scale to measure attitude after training and retrospectively before training, and a brief set of interview questions. Results for both treatments and the control group indicated increases in knowledge. Analysis of the posttest scores, when controlling for the pretest scores, indicated the difference was significant ( P ≤ 0.05); however, post hoc analysis did not indicate which treatment was superior. There was a significant increase in attitude scores for both groups using paired t -tests, although the difference between groups was not significant when controlling for attitude scores before training. Issues that may limit application of the technology used in this study include low literacy and language barriers among employees, and time constraints within companies. These and other variables should be taken into account in future research studies addressing comparisons of training methods. This study is the first to demonstrate the effectiveness of computer-based training aimed at food handlers who work in food processing establishments.  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