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   56551篇
  免费   2386篇
  国内免费   21篇
  58958篇
  2020年   704篇
  2019年   815篇
  2018年   1167篇
  2017年   1188篇
  2016年   1234篇
  2015年   877篇
  2014年   1066篇
  2013年   4915篇
  2012年   1968篇
  2011年   1963篇
  2010年   1176篇
  2009年   1209篇
  2008年   1697篇
  2007年   1656篇
  2006年   1507篇
  2005年   1257篇
  2004年   1301篇
  2003年   1250篇
  2002年   1177篇
  2001年   1929篇
  2000年   1803篇
  1999年   1346篇
  1998年   623篇
  1997年   534篇
  1996年   613篇
  1995年   557篇
  1994年   547篇
  1993年   532篇
  1992年   1116篇
  1991年   1031篇
  1990年   1003篇
  1989年   962篇
  1988年   941篇
  1987年   873篇
  1986年   863篇
  1985年   911篇
  1984年   737篇
  1983年   633篇
  1979年   760篇
  1978年   566篇
  1975年   603篇
  1974年   687篇
  1973年   705篇
  1972年   606篇
  1971年   562篇
  1970年   485篇
  1969年   480篇
  1968年   613篇
  1967年   532篇
  1966年   508篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Although the typicality effect has been much studied in the semantic memory literature, typicality ratings exist for exemplars from only a very limited number of categories. This lack of ratings frequently limits the range of stimuli that can be used in investigations of the typicality effect. As an aid in stimulus construction, this paper reports typicality ratings of 893 exemplars from 93 different categories.  相似文献   
912.
An electronic device for detecting movement in small animals is described. The principle involves assessing changes in resistance between pairs of grid bars in a cage. The device is inexpensive, sensitive to movement, easy to calibrate and install, reliable across different activity arenas, and indifferent to animal size.  相似文献   
913.
The concepts of informed consent and surveillance of human research designed to protect human subjects is commendable. The regulations of the Institutional Review Board (IRB) are having a major impact on clinical cancer research. There is greater administrative time needed of the investigator, the mechanisms of patient care have become cumbersome and some patients reject optional medical management that could be life saving. IRB regulations must be flexible to meet the needs of human subjects as well as those of the clinical investigator.  相似文献   
914.
A radiotelemetry system for continuous monitoring of the temperature and/or location of small animals is described. All the functions of system control are carried out by an on-line microcomputer (TRS-80 Model III), resulting in a versatile system capable of alternating recording the temperature/location of multiple subjects with other behavioral or physiological events, such as activity level. We describe the use of this system in monitoring body temperature in hamsters and in recording the incubation pattern of breeding ring doves.  相似文献   
915.
Prior surgical implantation of a venous catheter sensitized rats to coldimmobilization stress. Three of six catheterized females succumbed during the stress. The remaining rats fell into two groups in terms of their core temperature at the end of the stress period: Male uncatheterized rats had higher temperatures than rats in the other three groups. No relation was found between catheter patency and magnitude of hypothermia. Degree of gastric disease paralleled the core temperature findings in that the male uncatheterized rats had significantly fewer gastric erosions than the rats in the other three groups. Additionally, a robust effect of gender was found with uncatheterized females showing more hypothermia and more gastric disease than uncatheterized males. A subsequent experiment was conducted to evaluate whether anesthesia or wearing the protective spring was responsible in part for the sensitization seen. Here, the gender difference was less although females consistently averaged lower core temperatures after stress than did males. Despite similar core temperatures after stress, females that were prepared with the protective spring apparatus developed more gastric disease than female controls or similarly treated males. Thus, the additional sensitization exhibited by females in the first experiment may relate to the fact that both catheterization and the taping procedure were sensitizers while only catheterization was a sensitizer for males.  相似文献   
916.
917.
The present study examined some previously reported relationships between drug use by adolescents and perceived attitudes and behaviors of their parents. An anonymous questionnaire was administered to the student body of an inner-city secondary school for difficult students. Relationships between parental use of drugs and adolescent use of the same drugs were moderate and roughly equivalent across drugs. However, parental use of marijuana was strongly related to the adolescent's use of other, harder drugs such as opiates, cocaine, amphetamines, and barbiturates. This finding is explained within the framework of Kandel's postulated stages of drug initiation. It points to a need for further study of parental influences, which may be increasingly problematic as more individuals who have grown up in our marijuana-accepting society become parents of adolescents.  相似文献   
918.
The relationship between the availability of visual information and attention demands during the production of a discrete motor act was examined. Subjects were required to move a linear slide a distance of 15 cm in both 150 and 600 msec conditions under three light manipulations, viz., light always on; light always terminated as movement began; or, subject was unsure as to whether light would stay on or terminate. A simple key press by the index finger of the opposite hand to a tone was used as a secondary task and a measure of attention demands. The light manipulation influenced attention demands on the rapid 150 msec movement such that more attention was demanded when the subject knew the light would terminate. No such attentional strategy differences were found with the slow 600 msec movement. These findings suggest that task constraints in the form of kinematic criteria, together with the perceived availability of visual information, contribute to determining attentional strategy in movement production.  相似文献   
919.
This study tested aspects of Super's self-concept theory of career development with a sample of British schoolchildren. Findings suggested that self-concepts and concepts of occupational preferences do have a role in career development, though there were some indications that the theory is more applicable to more able youngsters and to those high in self-esteem, than to others. Agreement between ideal-self-concepts and occupational preference concepts was significantly greater than that between actual-self-concepts and occupational preference concepts. This finding was interpreted as reflecting the youngsters' greater concern for the future and the possible, rather than the present and the given, and it suggested that refinements are needed in Super's theory.  相似文献   
920.
This paper considers the end phase of analysis. Beginning with a brief review of the literature on termination, specifically the indicators for initiating the termination process, we identify the structural attainments necessary for the patient to successfully complete the analysis and to maintain smooth post-analytic functioning. We stress in this regard the significance of self-analytic functions and the relative immutability of the transference neurosis. These points are illustrated with clinical examples. Our paper concludes with a discussion of the tasks and contributions of the analyst during the termination process. We make special reference to countertransference vulnerability resulting from the analyst's own termination experiences.  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