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   45783篇
  免费   2037篇
  国内免费   32篇
  2020年   536篇
  2019年   635篇
  2018年   917篇
  2017年   869篇
  2016年   967篇
  2015年   688篇
  2014年   794篇
  2013年   3577篇
  2012年   1494篇
  2011年   1567篇
  2010年   916篇
  2009年   964篇
  2008年   1258篇
  2007年   1249篇
  2006年   1108篇
  2005年   964篇
  2004年   945篇
  2003年   877篇
  2002年   889篇
  2001年   1627篇
  2000年   1613篇
  1999年   1145篇
  1998年   478篇
  1997年   456篇
  1995年   426篇
  1992年   933篇
  1991年   857篇
  1990年   857篇
  1989年   817篇
  1988年   806篇
  1987年   728篇
  1986年   750篇
  1985年   790篇
  1984年   635篇
  1983年   571篇
  1982年   421篇
  1979年   633篇
  1978年   471篇
  1977年   423篇
  1976年   427篇
  1975年   532篇
  1974年   652篇
  1973年   633篇
  1972年   583篇
  1971年   491篇
  1970年   452篇
  1969年   513篇
  1968年   602篇
  1967年   510篇
  1966年   515篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
This study examined the influence of various group diversity dimensions on collaborative creativity related to the healthcare system. Research findings on the association between diversity and brainstorming performance has been mixed. Diversity that increases cognitive stimulation or promotes elaboration has been shown to increase group performance. Participants exchanged ideas, replied, and elaborated using an electronic discussion board in an asynchronous fashion in groups of five over a period of 4 weeks. The groups varied in diversity of ethnicity, gender, age, and political orientation, but participants were not made aware of this diversity. Age and gender diversity were related to lower levels of replying to ideas and lower idea novelty but political diversity was related to increased replies and novelty. If a topic engages people with different perspectives to actively respond to others’ ideas, this can increase the creative potential of idea sharing in groups. Political or value-based diversity has the potential for creative solutions if the other participants’ political or value-based identities are not made salient.  相似文献   
24.
25.
Most studies of suicide in younger patients have demonstrated significant alterations in the serotonin system. Although a high percentage of completed suicides occur in late-life, to date very few studies of the biology of suicide have focused on this age group. This chapter describes age-related changes in the central nervous system pertinent to the biology of suicide, then reviews post-mortem biological studies of the brains of suicides and suicide attempters. As suicide attempts in the elderly are characterized by the use of violent means, biologic studies of impulsive violence are discussed. Finally we describe data on the effect of degenerative diseases on the serotonin system and the possible link to increased suicidal behavior in affected patients. This review underscores the need for further study of the biology of suicide in the geriatric age group.  相似文献   
26.
27.
28.
Brain mapping studies using dynamic imaging methods demonstrate areas regional cerebral blood flow (rCBF) decreases, as well as areas where increases, during performance of various experimental tasks. Task holds for both sets of cerebral blood flow changes (CBF), providing the opportunity to investigate areas that become and “activated” in the experimental condition relative to control state. Such data yield the intriguing observation that in areas in emotional processing, such as the amygdala, the posteromedial cortex, and the ventral anterior cingulate cortex, although flow as expected during specific emotion-related tasks, flow decreases performance of some attentionally demanding, cognitive tasks. Conversely, in some of the areas that appear to subserve cognitive functions, as the dorsal anterior cingulate and the dorsolateral prefrontal cortices, increases while performing attentionally demanding cognitive tasks, but during some experimentally induced and pathological emotional Although the specific nature of such reciprocal patterns of regional remains unclear, they may reflect an important cross-modal interaction during mental operations. The possibility that neural activity is less in areas required in emotional processing during some higher cognitive processes holds implications for the mechanisms underlying interactions cognition and emotion. Furthermore, the possibility that neural in some cognitive-processing areas is suppressed during intense states suggests mechanisms by which extreme fear or severe may interfere with cognitive performance.  相似文献   
29.
30.
It is widely assumed that reinforcers are biologically relevant stimuli, or stimuli that have been associated with biologically relevant stimuli. However, brief, arbitrary stimuli have also been reported to have reinforcement-like effects, despite being unrelated to biologically relevant stimuli like food. The present study explored the potential reinforcement-like effects of brief stimuli across 5 experiments. In Experiments 1 through 4, pigeon subjects responded for food reinforcement and brief stimulus presentations in a 2-component multiple schedule. Neither baseline response rates nor resistance to change during disruption tests were systematically greater in a component with versus without brief stimulus presentations. Increasing the rate and duration of brief stimulus presentations in Experiment 4 did not reveal reinforcement-like effects when compared directly with food. In Experiment 5, pigeons chose between independent terminal links in a concurrent-chains procedure. Across conditions, varying the location, duration, and rate of brief stimulus presentations in the terminal links had no systematic effects on preference. In contrast, varying rates of food reinforcers resulted in large and reliable shifts in preference. Therefore, the present study found no systematic evidence that brief stimuli unrelated to food reliably increase response rates, resistance to change, or preference. These data demonstrate the value of systematic replication, and a behavioral momentum approach to assessing potential reinforcement-like effects.  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