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   81445篇
  免费   2574篇
  国内免费   43篇
  2020年   760篇
  2019年   958篇
  2018年   4426篇
  2017年   3805篇
  2016年   3403篇
  2015年   1143篇
  2014年   1275篇
  2013年   5873篇
  2012年   2613篇
  2011年   4463篇
  2010年   3638篇
  2009年   2721篇
  2008年   3583篇
  2007年   3960篇
  2006年   1854篇
  2005年   1893篇
  2004年   1793篇
  2003年   1660篇
  2002年   1639篇
  2001年   1981篇
  2000年   1879篇
  1999年   1459篇
  1998年   845篇
  1997年   765篇
  1996年   680篇
  1995年   658篇
  1994年   626篇
  1993年   633篇
  1992年   1129篇
  1991年   1077篇
  1990年   1059篇
  1989年   942篇
  1988年   887篇
  1987年   890篇
  1986年   912篇
  1985年   997篇
  1984年   802篇
  1983年   698篇
  1982年   574篇
  1981年   543篇
  1980年   543篇
  1979年   743篇
  1978年   581篇
  1976年   537篇
  1975年   674篇
  1974年   710篇
  1973年   670篇
  1972年   589篇
  1968年   561篇
  1967年   564篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
902.
Persistence and its assessment have been studied since the 1920s. One common approach in measuring persistence has been through testing the subject's ability to solve difficult or monotonous problems. Another approach has been through questionnaires. Although persistence is very important in academic achievement and in the general development of personality, no questionnaires have been developed for measuring persistence in children. The present research concerns the development of such a scale. It includes 40 items and was tested on 322 Israeli children aged 7-13. The internal reliability of the scale (Cronbach alpha) was .66, and the test-retest reliability after 6 months was .77. The scale differentiated active gymnasts from non-gymnasts as well as persistent gymnasts from dropout gymnasts. In addition, significant correlations were found between the scale and the need-persistence measure of the Rosenzweig Picture Frustration Study, Locus of Control, and other measures. We discuss these findings along with the significance of persistence in everyday life.  相似文献   
903.
We develop a simple model of switching between the initial links of a concurrent-chain procedure. Behavior is determined by four parameters μ1, μ2, q1, and q2. The first two are the basic rates of switching from Schedule 1 and Schedule 2, respectively. The second two are the probabilities of leaving Schedule 1 and Schedule 2 after the corresponding terminal link has been completed. We show that for fixed values of these four parameters, the relative allocation on the initial links may change as a result of changes in initial-link schedules. The effect can be quite large if the switching rates are low. An implication is that relative allocation is not necessarily a good measure of behavior.  相似文献   
904.
A within-subjects comparison was made of pigeons' performance on two temporal discrimination procedures that were signaled by differently colored keylight samples. During stimulus trials, a peck on the key displaying a slanted line was reinforced following short keylight samples, and a peck on the key displaying a horizontal line was reinforced following long keylight samples, regardless of the location of the stimuli on those two choice keys. During position trials, a peck on the left key was reinforced following short keylight samples and a peck on the right key was reinforced following long keylight samples, regardless of which line stimulus appeared on the correct key. Thus, on stimulus trials, the correct choice key could not be discriminated prior to the presentation of the test stimuli, whereas on position trials, the correct choice key could be discriminated during the presentation of the sample stimulus. During Phase 1, with a 0-s delay between sample and choice stimuli, discrimination learning was faster on position trials than on stimulus trials for all 4 birds. During Phase 2, 0-, 0.5-, and 1.0-s delays produced differential loss of stimulus control under the two tasks for 2 birds. Response patterns during the delay intervals provided some evidence for differential mediation of the two delayed discriminations. These between-task differences suggest that the same processes may not mediate performance in each.  相似文献   
905.
906.
907.
908.
909.
910.
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