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   745篇
  免费   22篇
教育   463篇
科学研究   73篇
各国文化   8篇
体育   132篇
综合类   2篇
文化理论   16篇
信息传播   73篇
  2023年   3篇
  2022年   12篇
  2021年   24篇
  2020年   30篇
  2019年   42篇
  2018年   61篇
  2017年   58篇
  2016年   51篇
  2015年   26篇
  2014年   32篇
  2013年   126篇
  2012年   37篇
  2011年   27篇
  2010年   26篇
  2009年   18篇
  2008年   32篇
  2007年   20篇
  2006年   16篇
  2005年   21篇
  2004年   17篇
  2003年   9篇
  2002年   8篇
  2001年   6篇
  2000年   6篇
  1999年   3篇
  1998年   5篇
  1997年   4篇
  1994年   3篇
  1993年   2篇
  1992年   3篇
  1991年   5篇
  1990年   3篇
  1989年   1篇
  1988年   4篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   3篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
  1973年   2篇
  1972年   2篇
  1962年   1篇
  1935年   1篇
  1903年   1篇
排序方式: 共有767条查询结果,搜索用时 15 毫秒
711.
Abstract

A frequently occurring situation in college and professional football is that of a team catching up through two touchdowns after trailing by 14 points, with the game outcome being determined by the extra-point plays. For leagues allowing two-point converts, an optimal point-after strategy exists under quite reasonable assumptions, and depends upon the relative utility to the team of a win, tie, or loss and the probability of success with a (one-point) kick as opposed to a (two-point) run/pass. We illustrate with reference to the January 1984 Orange Bowl game, where the favored team followed a possibly suboptimal strategy, losing the game and the national championship.  相似文献   
712.
713.
In economics the Research Papers in Economics (RePEc) network has become an essential source for the gathering and the spread of both existing and new economic research. Furthermore, it is currently the largest bibliometric database in economic sciences containing 33 different indicators for more than 30,000 economists. Based on this bibliographic information RePEc calculates well-known rankings for authors and academic institutions. We provide some cautionary remarks concerning the interpretation of some provided bibliometric measures in RePEc. Moreover, we show how individual and aggregated rankings can be biased due to the employed ranking methodology. In order to select key indicators describing and assessing research performance of scientist, we propose to apply principal component analysis in this data-rich environment. This approach allows us to assign weights to each indicator prior to aggregation. We illustrate the approach by providing a new overall ranking of economists based on RePEc data.  相似文献   
714.
Determination of amyloid β (Aβ) isoforms and in particular the proportion of the Aβ 1-42 isoform in cerebrospinal fluid (CSF) of patients suspected of Alzheimer’s disease might help in early diagnosis and treatment of that illness. Due to the low concentration of Aβ peptides in biological fluids, a preconcentration step prior to the detection step is often necessary. This study utilized on-chip immunoprecipitation, known as micro-immunoprecipitation (μIP). The technique uses an immunosorbent (IS) consisting of magnetic beads coated with specific anti-Aβ antibodies organized into an affinity microcolumn by a magnetic field. Our goal was to thoroughly describe the critical steps in developing the IS, such as selecting the proper beads and anti-Aβ antibodies, as well as optimizing the immobilization technique and μIP protocol. The latter includes selecting optimal elution conditions. Furthermore, we demonstrate the efficiency of anti-Aβ IS for μIP and specific capture of 5 Aβ peptides under optimized conditions using various subsequent analytical methods, including matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), capillary electrophoresis, microchip electrophoresis, and immunoblotting. Synthetic Aβ peptides samples prepared in buffer and spiked in human CSF were analyzed. Finally, on-chip immunoprecipitation of Aβ peptides in human CSF sample was performed.  相似文献   
715.
The purpose of this study was to determine the physiological, anthropometric, performance, and nutritional characteristics of the Brazil Canoe Polo National Team. Ten male canoe polo athletes (age 26.7 ± 4.1 years) performed a battery of tests including assessments of anthropometric parameters, upper-body anaerobic power (Wingate), muscular strength, aerobic power, and nutritional profile. In addition, we characterized heart rate and plasma lactate responses and the temporal pattern of the effort/recovery during a simulated canoe polo match. The main results are as follows: body fat, 12.3 ± 4.0%; upper-body peak and mean power, 6.8 ± 0.5 and 4.7 ± 0.4 W · kg(-1), respectively; 1-RM bench press, 99.1 ± 11.7 kg; peak oxygen uptake, 44.3 ± 5.8 mL · kg(-1) · min(-1); total energy intake, 42.8 ± 8.6 kcal · kg(-1); protein, carbohydrate, and fat intakes, 1.9 ± 0.1, 5.0 ± 1.5, and 1.7 ± 0.4 g · kg(-1), respectively; mean heart rate, 146 ± 11 beats · min(-1); plasma lactate, 5.7 ± 3.8 mmol · L(-1) at half-time and 4.6 ± 2.2 mmol · L(-1) at the end of the match; effort time (relative to total match time), 93.1 ± 3.0%; number of sprints, 9.6 ± 4.4. The results of this study will assist coaches, trainers, and nutritionists in developing more adequate training programmes and dietary interventions for canoe polo athletes.  相似文献   
716.
Team leaders are expected to adequately analyse team conflicts. Both content and analytical depth of cognitive processes determine team leaders’ performance and are assumed to differ with level of expertise. A study is reported in which team leaders at four different levels of expertise (novices, semi-experts, experts, mediators) were compared in their analysis of a team conflict presented in a computer-based simulation. Few differences were found between novices and semi-experts, whereas team leaders and mediators differed both in content and in analytical depth of cognitive processes. It is not the amount of practice time itself, which substantially impacts the content and depth of team leaders’ analyses of conflicts. Rather the quality of experience is crucial for developing the ability to conduct an elaborated analysis of team conflicts.  相似文献   
717.
718.
719.
720.
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