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   145907篇
  免费   2259篇
  国内免费   757篇
教育   99661篇
科学研究   16825篇
各国文化   2032篇
体育   11546篇
综合类   1284篇
文化理论   1184篇
信息传播   16391篇
  2022年   810篇
  2021年   1563篇
  2020年   2084篇
  2019年   2836篇
  2018年   3442篇
  2017年   3728篇
  2016年   3722篇
  2015年   2993篇
  2014年   4100篇
  2013年   28511篇
  2012年   3913篇
  2011年   4447篇
  2010年   3812篇
  2009年   3937篇
  2008年   3745篇
  2007年   3602篇
  2006年   3809篇
  2005年   3597篇
  2004年   3721篇
  2003年   3014篇
  2002年   2859篇
  2001年   2790篇
  2000年   2238篇
  1999年   1966篇
  1998年   1642篇
  1997年   1648篇
  1996年   1807篇
  1995年   1507篇
  1994年   1520篇
  1993年   1525篇
  1992年   1667篇
  1991年   1562篇
  1990年   1567篇
  1989年   1486篇
  1988年   1314篇
  1987年   1270篇
  1986年   1279篇
  1985年   1548篇
  1984年   1388篇
  1983年   1373篇
  1982年   1290篇
  1981年   1221篇
  1980年   1201篇
  1979年   1364篇
  1978年   1261篇
  1977年   1152篇
  1976年   1051篇
  1975年   862篇
  1974年   861篇
  1973年   836篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Self‐efficacy is a universal construct, but few validated measures exist for researchers in developing countries to use in assessing youths’ perceptions of their ability to achieve academic success. This study examined the cross‐cultural suitability and psychometric properties of an academic self‐efficacy scale (ASES) adapted for the Ghanaian context. ASES construct validity was assessed with a sample of 4,289 Ghanaian junior high‐school students and exploratory and confirmatory factor analysis. Invariance testing assessed the scale's measurement equivalence by gender and temporal stability of gender equivalence. The ASES is a valid, reliable one‐dimensional scale for assessing young Ghanaians’ perceptions of their academic capabilities, and it works equally well across genders. As adapted, ASES is a valid scale with utility for researchers examining predictors and effects of academic self‐efficacy. The ASES has important implications for decisions regarding investment in programs aimed at improving academic self‐efficacy of youth, both in sub‐Saharan Africa and the increasingly diverse American public schools.  相似文献   
992.
993.
994.
995.
996.
997.
998.
Circulating tumor cells (CTCs) shed from the primary tumor undergo significant fragmentation in the microvasculature, and very few escape to instigate metastases. Inspired by this in vivo behavior of CTCs, we report a microfluidic method to phenotype cancer cells based on their ability to arrest and fragment at a micropillar-based bifurcation. We find that in addition to cancer cell size, mechanical properties determine fragmentability. We observe that highly metastatic prostate cancer cells are more resistant to fragmentation than weakly metastatic cells, providing the first indication that metastatic CTCs can escape rupture and potentially initiate secondary tumors. Our method may thus be useful in identifying phenotypes that succumb to or escape mechanical trauma in microcirculation.  相似文献   
999.
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   
1000.
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