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   55880篇
  免费   2333篇
  国内免费   21篇
  58234篇
  2020年   676篇
  2019年   795篇
  2018年   1131篇
  2017年   1141篇
  2016年   1194篇
  2015年   854篇
  2014年   1036篇
  2013年   4833篇
  2012年   1931篇
  2011年   1931篇
  2010年   1160篇
  2009年   1183篇
  2008年   1666篇
  2007年   1631篇
  2006年   1494篇
  2005年   1237篇
  2004年   1284篇
  2003年   1228篇
  2002年   1164篇
  2001年   1926篇
  2000年   1802篇
  1999年   1343篇
  1998年   617篇
  1997年   530篇
  1996年   606篇
  1995年   552篇
  1994年   543篇
  1993年   530篇
  1992年   1109篇
  1991年   1019篇
  1990年   1000篇
  1989年   962篇
  1988年   938篇
  1987年   867篇
  1986年   858篇
  1985年   903篇
  1984年   730篇
  1983年   631篇
  1979年   763篇
  1978年   565篇
  1975年   602篇
  1974年   679篇
  1973年   701篇
  1972年   606篇
  1971年   562篇
  1970年   483篇
  1969年   479篇
  1968年   610篇
  1967年   530篇
  1966年   506篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
931.
Learned helplessness theory predicts that animals exposed to inescapable shock acquire an expectancy of response-reinforcer independence, which proactively interferes with learning of response-reinforcer dependence. The theory also predicts that this expectancy can increase sensitivity to subsequent instances of response-reinforcer independence. These experiments test the latter prediction in a paradigm that minimizes the confounding effects of shock-induced activity deficits. Rats were trained to respond for food, then given either escapable, inescapable, or no shock. Subsequently, they received two sessions of response-contingent food followed by sessions of noncontingent food deliveries. During this phase, inescapably shocked animals decreased responding faster than did controls. Experiment 2 replicated this finding with a different schedule of food delivery and a procedure that more directly minimized the possibility that the outcome is due to either direct or indirect shock-induced activity changes. These results support the prediction that uncontrollable aversive events can increase an animal's sensitivity to noncontingent response-reinforcer relationships.  相似文献   
932.
933.
934.
Mixed hyperactive/reading-disabled children, selected from a large sample of hyperactive children, were compared to pure hyperactive children on demographic, behavioral, and neuropsychological measures. Children in the Mixed group were reading-disabled relative to age and IQ; those in the Pure group had achievement scores that were average relative to age and IQ. The Mixed group was significantly older than the Pure group; there were no differences in gender, race, or socioeconomic status. Behaviorally, the groups did not differ significantly on teacher ratings or on psychiatric ratings of aggression. The Mixed group had a significantly higher Performance IQ, whereas the Pure group had a significantly higher Verbal IQ and performed better on measures of cognitive impulsivity. Several other measures failed to distinguish the groups. The data give minimal support to the notion that pure hyperactive and mixed hyperative/reading-disabled children constitute distinct subgroups of Attention Deficit Disorder with Hyperactivity.This research was supported in part by Mental Health Clinical Research Grant MH-30906 and by U. S. Public Health Service Grant MH-18579.  相似文献   
935.
The empirical research pertaining to the effectiveness of telephone counseling and referral systems personnel was critically reviewed. The assessment was organized according to several evaluation strategies that researchers have utilized to evaluate effectiveness. These strategies included, for example, client self-reports, client "shows" versus "no-shows" following referral, data pertaining to suicide rates, counselor ratings of personal effectiveness, and phone workers' ability to offer empathy to clients. It was concluded that discussions of effectiveness should be constrained by a careful consideration of the specific index of efficacy chosen by investigators as well as methodological issues associated with current research in this area. There is reason to believe that the availability of telephone crisis services may be related to reduced suicide rates among young white females. Also, there is a significant need to empirically associate counseling technique and indices of effectiveness with substantive measures of client outcome in future research. Additional topics reviewed include the probable differential effectiveness of lay workers with various presenting problems of clients, and the role that training and maturity seem to play in successful interventions. Guidelines for the use of evaluation techniques which coincide with service goals are also offered.  相似文献   
936.
937.
938.
939.
Exposure to electric shock produces an analgesic reaction (SIA) that is reversed by opiate antagonists ("opioid" SIA) under some conditions but not under other conditions ("nonopioid" SIA). A number of studies using tail-flick to radiant heat as the measure of pain sensitivity have found that a small number of shocks lead to nonopioid SIA, while a large number of shocks produce opioid SIA. In contrast, a small number of shocks have been reported to produce opioid SIA when the Formalin test was used to measure pain reactivity. However, the Formalin test involves administering a chronic pain stimulus (injection of Formalin into the paw) for an extended period before the shocks. Here it is reported that this "preexperimental" stress is sufficient to convert the SIA after a small number of shocks measured by tail-flick to the opioid form.  相似文献   
940.
The purpose of this study was to examine whether apraxic-aphasic patients with parietal lesions had difficulty learning lists of gestures and whether the performance deficits they displayed resulted from an inability either to consolidate this information in memory or to retrieve the information once stored. The findings indicate that apraxic-aphasic patients do have difficulty acquiring lists of gestures. This inability to reproduce gestural information was not associated with a retrieval disorder, but instead the apraxic-aphasic subjects could not consolidate the information in memory.  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