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   66742篇
  免费   2703篇
  国内免费   20篇
  2020年   614篇
  2019年   786篇
  2018年   1067篇
  2017年   1100篇
  2016年   1149篇
  2015年   857篇
  2014年   1024篇
  2013年   4762篇
  2012年   1948篇
  2011年   1979篇
  2010年   1209篇
  2009年   1169篇
  2008年   1745篇
  2007年   1720篇
  2006年   1564篇
  2005年   1457篇
  2004年   1387篇
  2003年   1268篇
  2002年   1296篇
  2001年   2064篇
  2000年   1925篇
  1999年   1466篇
  1998年   725篇
  1996年   606篇
  1992年   1309篇
  1991年   1232篇
  1990年   1212篇
  1989年   1141篇
  1988年   1145篇
  1987年   1094篇
  1986年   1133篇
  1985年   1231篇
  1984年   952篇
  1983年   902篇
  1982年   687篇
  1981年   654篇
  1979年   1113篇
  1978年   751篇
  1977年   682篇
  1976年   717篇
  1975年   934篇
  1974年   1066篇
  1973年   1129篇
  1972年   954篇
  1971年   878篇
  1970年   879篇
  1969年   894篇
  1968年   1142篇
  1967年   1013篇
  1966年   935篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
891.
892.
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   
893.
894.
895.
896.
897.
The following survey is intended to demonstrate and discuss some principle problems of biomagnetism and the application in clinical fields. The development of special technical parameters especially by the SQUID method is initiating new possibilities of research and completing the neurobiologically determinated basis and conditions of neuropsychiatric disorders. The Magnetoencephalography (MEG) will be represent an important role of a new functional diagnostic method.  相似文献   
898.
We present four cases of Prader-Willi syndrome. Two of them have an abnormality of a chromosome 15, the other both show different chromosomal abnormalities. Translocations or deletions were found recently in the bands 15q11/12 in about 60% of the cases of Prader-Willi syndrome. The consequences for diagnosis, symptomatology and genetic counselling of the syndrome are discussed.  相似文献   
899.
Gender differences across age in motor performance a meta-analysis   总被引:3,自引:0,他引:3  
  相似文献   
900.
Thomas R. Alley 《Synthese》1985,65(3):411-444
The concept of an ecological niche (econiche) has been used in a variety of ways, some of which are incompatible with a relational or functional interpretation of the term. This essay seeks to standardize usage by limiting the concept to functional relations between organisms and their surroundings, and to revise the concept to include epistemic relations. For most organisms, epistemics are a vital aspect of their functional relationships to their surroundings and, hence, a major determinant of their econiche. Rejecting the traditional dualism of organism and environment, an econiche is defined as the reciprocal (dual) of a functionally specified class of organisms (FSTU). From this perspective, an econiche necessarily implies a certain type of organism, and a class of functionally similar organisms implies a special econiche.The econiche concept is also discussed in relation to other ecological terms that reflect the distributional patterns of organisms, such as habitat, and the concept of an empty niche is criticized.Special thanks are due to Michael Turvery for his part in many stimulating discussions of some of the problems and concepts addressed in this paper. I am also grateful to him and to Claudia Carello, Tim Johnston, Bill Mace, Bernard Patten, Ed Reed, Robert E. Shaw, Bill Warren, and an anonymous reviewer for their comments on earlier drafts of this paper.  相似文献   
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