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   14918篇
  免费   200篇
  国内免费   12篇
教育   10192篇
科学研究   1318篇
各国文化   161篇
体育   1534篇
综合类   24篇
文化理论   106篇
信息传播   1795篇
  2021年   109篇
  2020年   213篇
  2019年   302篇
  2018年   351篇
  2017年   422篇
  2016年   374篇
  2015年   242篇
  2014年   328篇
  2013年   2724篇
  2012年   287篇
  2011年   324篇
  2010年   258篇
  2009年   289篇
  2008年   283篇
  2007年   272篇
  2006年   252篇
  2005年   230篇
  2004年   474篇
  2003年   368篇
  2002年   388篇
  2001年   249篇
  2000年   266篇
  1999年   209篇
  1998年   106篇
  1997年   129篇
  1996年   160篇
  1995年   149篇
  1994年   134篇
  1993年   132篇
  1992年   185篇
  1991年   188篇
  1990年   169篇
  1989年   217篇
  1988年   182篇
  1987年   210篇
  1986年   181篇
  1985年   236篇
  1984年   198篇
  1983年   179篇
  1982年   159篇
  1981年   138篇
  1980年   114篇
  1979年   177篇
  1978年   140篇
  1977年   124篇
  1976年   142篇
  1975年   103篇
  1974年   121篇
  1973年   98篇
  1971年   110篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
143.
144.
ABSTRACT

Participation in youth sport is positively associated with physical fitness and performance. The purpose of the current study was to examine if physical fitness measures during childhood and early adolescence predicted high school sport participation. Participants included youth in the Michigan State University Motor Performance Study. Measures consisted of the endurance shuttle run, Wells sit-and-reach, jump and reach, standing long jump, agility shuttle run and 30-yard dash. Individual, generalized estimating equation models were used to estimate the association between each measure and the odds of participating in high school sport. For both sexes, the endurance shuttle run and agility shuttle run were related to sport participation. For boys only, the long jump and 30-yard dash were also associated with sport participation. Better physical fitness and performance across several dimensions in childhood, including those related to motor skills, enhanced the likelihood of sport participation in high school.  相似文献   
145.
146.
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   
147.
148.
149.
ABSTRACT

The length of telomeres is an objective measure of biologic ageing. This study evaluated the extent minutes of walking per week are associated with leukocyte telomere length (LTL) in a random sample of 5,823 U.S. adults. The investigation was cross-sectional and data were obtained from the National Health and Nutrition Examination Survey (NHANES). LTL was measured by the quantitative polymerase chain reaction method. Walking minutes was calculated from walking frequency and duration measures. Results showed that for each year of chronological age, telomeres were 15.6 base pairs shorter (P < 0.0001). With walking minutes and LTL treated as continuous variables, the relationship was quadratic, not linear (F = 11.2, P = 0.0023). With walking time divided into three categories, adults who performed ≥ 150 minutes of walking per week had longer telomeres than those who did no regular walking, and those who did some, but less than the recommendation (F = 5.0, P = 0.0137). Regular walkers were estimated to have a biologic ageing advantage associated with 6.5–7.6 years less biologic ageing compared to non-walkers, after adjusting for covariates. Additional investigations designed to study causality and the mechanisms associated with the walking and LTL relationship are needed.  相似文献   
150.
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