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   21849篇
  免费   911篇
  国内免费   13篇
  2020年   251篇
  2019年   243篇
  2018年   418篇
  2017年   361篇
  2016年   387篇
  2015年   245篇
  2014年   359篇
  2013年   1568篇
  2012年   633篇
  2011年   674篇
  2010年   352篇
  2009年   442篇
  2008年   596篇
  2007年   593篇
  2006年   547篇
  2005年   480篇
  2004年   462篇
  2003年   454篇
  2002年   417篇
  2001年   813篇
  2000年   798篇
  1999年   594篇
  1998年   239篇
  1997年   226篇
  1993年   196篇
  1992年   488篇
  1991年   429篇
  1990年   491篇
  1989年   412篇
  1988年   394篇
  1987年   369篇
  1986年   393篇
  1985年   442篇
  1984年   346篇
  1983年   285篇
  1982年   220篇
  1979年   328篇
  1978年   261篇
  1977年   205篇
  1976年   201篇
  1975年   301篇
  1974年   346篇
  1973年   350篇
  1972年   277篇
  1971年   247篇
  1970年   211篇
  1969年   230篇
  1968年   289篇
  1967年   256篇
  1966年   275篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
In this paper, we propose a theory of coalition formation in simple games. The process of coalition formation is modeled as an abstract game. Two solutions of abstract games, the core and the dynamic solution, are used as the predictions of our model. Two classical theories of coalitions in sociology due to Caplow and Gamson are reformulated in a more general and mathematical setting. These theories are then analyzed using the techniques of our theory.  相似文献   
942.
943.
944.
945.
946.
The significance of a helicopter patrol procedure directed toward prevention of home burglaries was evaluated from experimental and cost-benefit perspectives. The helicopter patrolled one city zone from 9 a.m. to 5 p.m. for two 12-day periods. Each 12-day period was separated by a baseline period in which only normal patrol-car levels were maintained. Significantly reduced burglary levels during the intervention periods, compared to baseline periods, documented the experimental significance of the helicopter procedure. The cash costs of implementing the patrol procedure were compared to two estimates of the resulting cash benefits. This latter cost-benefit analysis was supplemented by a discussion of the intangible costs and benefits of the helicopter procedure. Taken together, these analyses documented that the marginal costs of the helicopter intervention were exceeded by all estimates of benefits.  相似文献   
947.
Two recent published reviews of research on behavioral marriage therapy stimulated us to supplement these accounts with additional relevant data. First, we place research on behavioral couples therapy in the broader context of outcome research on nonbehavioral marital therapy. We then summarize the results of 23 studies of behavioral couples therapy not included in these previous reviews and conclude that these additional data on controlled and comparative studies do little to enhance the current empirical status of the efficacy of behavioral marriage therapy and in no case do they establish the superiority of social learning approaches. It is concluded that an open mind to all sources of data on the efficacy of marital therapy is needed if the field is to make meaningful advances.  相似文献   
948.
Intracranial microinjections of 6-hydroxydopamine or 5,6-dihydroxytryptamine into six ascending monoamine pathways produced the expected patterns of depletion of telencephalic serotonin, dopamine, and norepinephrine. Serotonin level was specifically lowered after dorsal or median raphe lesions but not after mesolimbic or nigrostriatal system lesions which lowered both norepinephrine and dopamine. Lesions in the locus coeruleus or ventral nor-adrenergic bundle lowered only norepinephrine, and locus coeruleus lesions elevated serotonin level. Behavior was examined in an open field, one-way active avoidance, and two passive avoidance tasks, and measures were taken of water consumption and body weight. Dorsal raphe lesions had no effect on any of the measures; the other five lesion groups exhibited deficient acquisition of the one-way active avoidance task. In the appetitive passive avoidance task, only the substantia nigra lesion group exhibited a deficiency. In the step-through passive avoidance task, both the substantia nigra and the median raphe groups exhibited a deficit, with the median raphe group exhibiting hyperactivity in the start box during testing. Water consumption was decreased by lesions in the ventral noradrenergic bundle during the first postoperative week and was increased in the median raphe group by the fourth postoperative week. Lastly, lesions in the locus coeruleus dramatically decreased activity in the open field. The results are discussed in regard to the search for specificity of behavioral functions of the distinct ascending monoamine pathways.  相似文献   
949.
Five related experiments investigating stimulus generalization following go/no-go discrimination training of educable retarded children are reported. Experiment 1 employed an Extradimensional paradigm in which generalization testing was on the hue dimension following training on an independent (orientation) dimension. Following True discrimination training only 25% of children showed a decremental stimulus generalization gradient on the hue dimension, though all children exhibited flat gradients in Pseudodiscrimination and S+ only control groups. An increase in difficulty of the orientation discrimination in Experiment 2 did not increase the number of decremental gradients. In Experiment 3, children who exhibited decremental gradients in Experiments 1 and 2 underwent further generalization testing with modified stimuli to establish a symmetrical gradient peaked at a hue S+ to be employed in Experiments 4 and 5. In these experiments an Intradimensional paradigm was employed with S+ and S? stimuli drawn from the hue dimension. Excitatory control by S+ and inhibitory control by S? were demonstrated, as were inhibitory consequences of S? such as peak and area shift.  相似文献   
950.
The early stages of recovery from lateral hypothalamic lesions were analyzed in 30 adult cats. In addition to aphagia and adipsia, neurological examination revealed deficits suggestive of deficient endogenous arousal, including somnolence, catalepsy, akinesia, and sensory neglect. Manipulations (tail pinch and injection of amphetamine) that counteracted these deficits also restored feeding. During recovery from aphagia, feeding gradually became activated by sensory stimuli (sight, feel, and smell) associated with food. These data suggest that activation is an important component in the control of normal feeding.  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