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   77177篇
  免费   3130篇
  国内免费   27篇
  80334篇
  2020年   723篇
  2019年   959篇
  2018年   1299篇
  2017年   1376篇
  2016年   1465篇
  2015年   1054篇
  2014年   1230篇
  2013年   5875篇
  2012年   2263篇
  2011年   2436篇
  2010年   1526篇
  2009年   1502篇
  2008年   2105篇
  2007年   2168篇
  2006年   1955篇
  2005年   1739篇
  2004年   1640篇
  2003年   1551篇
  2002年   1663篇
  2001年   2480篇
  2000年   2426篇
  1999年   1855篇
  1998年   867篇
  1997年   773篇
  1996年   804篇
  1995年   701篇
  1992年   1576篇
  1991年   1478篇
  1990年   1448篇
  1989年   1323篇
  1988年   1324篇
  1987年   1248篇
  1986年   1317篇
  1985年   1356篇
  1984年   1121篇
  1983年   1030篇
  1982年   737篇
  1981年   735篇
  1979年   1207篇
  1978年   868篇
  1975年   986篇
  1974年   1103篇
  1973年   1216篇
  1972年   997篇
  1971年   952篇
  1970年   875篇
  1969年   866篇
  1968年   1127篇
  1967年   1023篇
  1966年   873篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
891.
Handling time and choice in pigeons   总被引:2,自引:1,他引:1       下载免费PDF全文
According to optimal foraging theory, animals should prefer food items with the highest ratios of energy intake to handling time. When single items have negligible handling times, one large item should be preferred to a collection of small ones of equivalent total weight. However, when pigeons were offered such a choice on equal concurrent variable-interval schedules in a shuttlebox, they preferred the side offering many small items per reinforcement to that offering one or a few relatively large items. This preference was still evident on concurrent fixed-cumulative-duration schedules in which choosing the alternative with longer handling time substantially lowered the rate of food intake.  相似文献   
892.
893.
Scores on the Beck Depression Inventory (BDI) were periodically obtained from the roommates of college students who exhibited a persistent mild depression over a 3-month period. For comparative purposes, BDI scores were also obtained from roommates of individuals who were transiently depressed and from subjects with nondepressed roommates. In comparison with control subjects, the roommates of persistently depressed persons displayed a progressive increase in BDI score over the course of the study.  相似文献   
894.
895.
896.
The foot is a highly cathected appendage that is commonly singled out as the brunt of humorous or derisive remarks, as if it embodies repugnance and disgust. Attitudes toward the foot are overdetermined, bearing the imprint of man's early linguistic patterns and individual dynamics. This article suggests that feet are symbolic because they bear the feelings derived from earlier separations, good and bad object representations, collective memories, and genital representations. The foot's role as symbol of both the male and female genitals, repository of badness, symbol of passivity, initiator of movement, and site of self-mutilation have been briefly reviewed. As Fats Waller rhapsodizes that the "feet's too big," he finds a convenient way to displace his symbiotic and erotic anxieties vis-à-vis women. Similarly, patients who come for psychiatric treatment and psychotherapy frequently make references to their feet or use them in specific ways. An understanding of this type of communication can often provide insight into individual dynamics and enhance treatment. The weight placed on these communications depends, of course, on the vicissitudes of the previous therapeutic work as well as on the particular problems of the patient.  相似文献   
897.
898.
Gender differences across age in motor performance a meta-analysis   总被引:3,自引:0,他引:3  
  相似文献   
899.
Thirty preschool children, 10 each at the 3-,4-, and 5-year-old levels, participated in two structured tasks designed to assess both comprehension and production of a full range of directive forms. In contrast to previous reports, the results indicated no significant differences in directive comprehension or production as a function of age; children in all age groups demonstrated the ability to understand and verbally encode the intent of most types of directive forms. However, the two most implicit forms, Question Directives and Hints, were complied with significantly less frequently than the more explicit forms, and were uused less often in the production task. The present findings indicate the importance of analyzing directive forms along a continuum of explicitness rather than dichotomizing them as direct versus indirect. Finally, the results are interpreted as providing indirect support for the general notion that mastery of some implicit forms may be achieved later than the acquisition of more explicit forms.  相似文献   
900.
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