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   93902篇
  免费   3777篇
  国内免费   35篇
  97714篇
  2020年   1023篇
  2019年   1310篇
  2018年   1760篇
  2017年   1884篇
  2016年   1958篇
  2015年   1418篇
  2014年   1704篇
  2013年   7502篇
  2012年   3025篇
  2011年   3169篇
  2010年   1971篇
  2009年   1986篇
  2008年   2752篇
  2007年   2839篇
  2006年   2566篇
  2005年   2226篇
  2004年   2116篇
  2003年   1984篇
  2002年   2058篇
  2001年   2840篇
  2000年   2765篇
  1999年   2121篇
  1998年   1066篇
  1997年   946篇
  1996年   934篇
  1995年   859篇
  1993年   868篇
  1992年   1806篇
  1991年   1636篇
  1990年   1661篇
  1989年   1482篇
  1988年   1498篇
  1987年   1439篇
  1986年   1506篇
  1985年   1479篇
  1984年   1314篇
  1983年   1201篇
  1982年   889篇
  1979年   1403篇
  1978年   1017篇
  1975年   1131篇
  1974年   1220篇
  1973年   1339篇
  1972年   1113篇
  1971年   1030篇
  1970年   931篇
  1969年   993篇
  1968年   1227篇
  1967年   1118篇
  1966年   927篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
Five experiments were performed to investigate the effects of social status in groups of female mice on reproduction and on the release or urinary chemosignals that accelerate or delay the onset of sexual maturation in young females. Treatment of young female mice with urine from bottom-ranking mice in groups of 5 adult females resulted in delays in puberty comparable to those produced by treatment with urine pooled from females housed at moderate to high densities. Treatment of young females with urine from top-ranking females from the same groups resulted in ages for puberty not different from those of control females treated with water. There was an interaction between the social rank of a female and the stages of the estrous cycle with respect to the presence in the urine of chemosignals from grouping that delay puberty and estrus that accelerate puberty. Within groups of 5 adult mice, top-ranking females were in estrus more frequently than bottom-ranking females. Individually caged adult females treated with urine from top-ranking females were in estrus more frequently than females treated with urine from bottom-ranking females. When grouped females were separated into individual cages and mated, there was differential reproductive success: More top-ranking females conceived and bore litters than bottom-ranking females. Bottom-ranking females produced more female pups, relative to top- and middle-ranking females.  相似文献   
942.
943.
Sternheim and Boynton’s (1966) continuous judgmental color-naming technique was used to assess the elemental nature of achromatic colors. Results from three subjects indicate that the names “black” and “white” are necessary and sufficient to describe achromatic test lights associated with the name “gray.” On the basis of the criteria that establishes a color as elemental, black and white were confirmed as elemental, whereas gray was not. These findings support the assumption of various opponent processing models that there are only two elemental achromatic sensations. In addition, the results support Hering’s (1920) view that black and white differ from the paired-chromatic opponent colors in that they are not mutually exclusive.  相似文献   
944.
Two experiments investigated infants’ sensitivity to familiar size as information for the distances of objects with which they had had only brief experience. Each experiment had two phases: a familiarization phase and a test phase. During the familiarization phase, the infant played with a pair of different-sized objects for 10 min. During the test phase, a pair of objects, identical to those seen in the familiarization phase but now equal in size, were presented to the infant at a fixed distance under monocular or binocular viewing conditions. In the test phase of Experiment 1, 7-month-old infants viewing the objects monocularly showed a significant preference to reach for the object that resembled the smaller object in the familiarization phase. Seven-month-old infants in the binocular viewing condition reached equally to the two test phase objects. These results indicate that, in the monocular condition, the 7-month-olds used knowledge about the objects’ sizes, acquired during the familiarization phase, to perceive distance from the test objects’ visual angles, and that they reached preferentially for the apparently nearer object. The lack of a reaching preference in the binocular condition rules out interpretations of the results not based on the objects’ perceived distances. The results, therefore, indicate that 7-month-old infants can use memory to mediate spatial perception. The implications of this finding for the debate between direct and indirect theories of visual perception are discussed. In the test phase of Experiment 2,5-month-old infants viewing the objects monocularly showed no reaching preference. These infants, therefore, showed no evidence of sensitivity to familiar size as distance information.  相似文献   
945.
946.
A small informal poll of local colleagues revealed that despite their interest in the subject, many had doubts about the possibility of analyzing persons aged sixty or over successfully. Their specific questions are collated and are offered as a sample of the questions in the minds of many analysts everywhere. Selected material from the ongoing analysis of a sixty-four-year-old patient is presented that bears on some of the questions raised. In addition, changes in the patient are noted. These are discussed in terms of changes in function, which are equated with structural change. The major thrust of the paper is that development continues throughout the life course, and that the criteria for analyzability remain constant. The chronological age of the adult by itself is not an indicator of eligibility or of suitability for psychoanalysis.  相似文献   
947.
948.
949.
950.
Dieting and binging. A causal analysis   总被引:16,自引:0,他引:16  
  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