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   58682篇
  免费   1592篇
  国内免费   14篇
  2020年   360篇
  2019年   423篇
  2018年   3929篇
  2017年   3257篇
  2016年   2807篇
  2015年   677篇
  2014年   630篇
  2013年   2686篇
  2012年   1627篇
  2011年   3360篇
  2010年   3093篇
  2009年   2063篇
  2008年   2586篇
  2007年   3052篇
  2006年   840篇
  2005年   1007篇
  2004年   905篇
  2003年   783篇
  2002年   756篇
  2001年   1303篇
  2000年   1277篇
  1999年   906篇
  1998年   423篇
  1997年   358篇
  1992年   869篇
  1991年   810篇
  1990年   834篇
  1989年   718篇
  1988年   714篇
  1987年   685篇
  1986年   716篇
  1985年   790篇
  1984年   592篇
  1983年   554篇
  1982年   370篇
  1981年   359篇
  1979年   690篇
  1978年   430篇
  1977年   423篇
  1976年   420篇
  1975年   588篇
  1974年   672篇
  1973年   718篇
  1972年   619篇
  1971年   579篇
  1970年   578篇
  1969年   564篇
  1968年   753篇
  1967年   670篇
  1966年   593篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The ability of two species of tits to remember the location and/or features of an object was tested in a delayed-matching-to-sample procedure. Three values of retention interval between presentation of the sample stimulus and the choice--30 sec, 5 min, and 15 min--were used. Both species performed at above-chance level at all retention intervals, and there was no significant decline in accuracy with increasing interval. A pool of 100 stimulus objects was used, but the results of control trials indicated that the birds responded primarily to location rather than stimulus features of the object itseif. Although the food-storing marsh tit tended to perform at a higher level than the non-storing great tit, the only significant difference between the species was in the first 50 trials of the first treatment, when the birds were acquiring the task. The results are discussed in relation to the hypothesized special memory capacity of food-storing birds.  相似文献   
22.
As the complexity of the challenges presented by our interactions with our planet continues to grow, we must develop new modes of knowledge production. In these modes, distinctions between multidisciplinary and inter-disciplinary activities and processes have renewed importance. There are at least two distinct types of interdisciplinary activities distinguished by the disciplinary breadth they attempt to bridge. In the narrow case, reductionist processes reveal a common underlying principle or process which can serve as a Rosetta stone. In the broad case, no such common arbiter exists. Investigators must develop integrating vocabulary in the context of the full breadth of their work. His primary activities are the fostering of university-wide interdisciplinary research and curriculum programs focused on global change with the goal of developing Columbia into a world leader in issues related to global stewardship.  相似文献   
23.
24.
25.
26.
27.
Subjects in five experiments read nine-digit memory lists from a cathode ray tube for immediate recall. Reading aloud always produced a localized and reliable advantage for the last item, compared to reading silently. Two experiments on whispered and mouthed lists, with or without simultaneous broadband noise, falsified expectations derived from the theory of precategorical acoustic storage. Three additional experiments showed no enhancement of recency in the silent conditions when the digits were drawn or spelled gradually on the screen, a result that is inconsistent with the changing-state hypothesis. The classic auditory-visual modality effect is large and reliable, but still poorly understood.  相似文献   
28.
29.
30.
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