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   1858篇
  免费   48篇
  1906篇
  2019年   29篇
  2018年   37篇
  2017年   33篇
  2016年   40篇
  2015年   22篇
  2014年   42篇
  2013年   227篇
  2012年   73篇
  2011年   65篇
  2010年   41篇
  2009年   35篇
  2008年   54篇
  2007年   61篇
  2006年   55篇
  2005年   49篇
  2004年   41篇
  2003年   47篇
  2002年   47篇
  2001年   64篇
  2000年   64篇
  1999年   55篇
  1998年   28篇
  1997年   21篇
  1995年   18篇
  1993年   19篇
  1992年   18篇
  1991年   32篇
  1990年   34篇
  1989年   20篇
  1988年   17篇
  1987年   21篇
  1986年   27篇
  1985年   24篇
  1984年   13篇
  1983年   22篇
  1982年   21篇
  1980年   13篇
  1979年   20篇
  1978年   19篇
  1977年   13篇
  1976年   23篇
  1975年   20篇
  1974年   21篇
  1973年   25篇
  1972年   15篇
  1970年   19篇
  1969年   14篇
  1968年   19篇
  1967年   15篇
  1966年   12篇
排序方式: 共有1906条查询结果,搜索用时 15 毫秒
271.
272.
A field experiment was conducted in which a single male, a single female, or a male-female couple attempted to hitch rides at four different traffic locations, under conditions in which the hitchhikers either stared at or looked away from oncoming drivers. It was found that staring increased the probability of a driver stopping from .03 to .067 (z = 2.96, p = .003). The female was a more successful hitchhiker than either the male or the couple, (z = 2.215, p = .026; z = 1.861, p .063, respectively).  相似文献   
273.
A demonstration of cell-specific patterns of development in the immature CNS is provided by examples of characteristic, cellspecific time-courses of enzyme development in different classes of brain cells isolated in highly purified form by bulk-separation from the cerebral and cerebellar cortex of the growing rat. The enzymatic analysis was carried out at the level of the nerve and glial cell lysosomes and mitochondria, two subcellular organelles crucial to the economy of all cells. The findings reveal rather similar developmental patterns for the lysosomal hydrolase N-acetyl-β-D-glucosaminidase in neurons and glial cells of the cerebral cortex as well as in two different cerebellar nerve cell types, the Purkinje and the granule cell. However, significant differences in the post-natal chronology of development of the mitochondrial enzyme α-glycerophosphate dehydrogenase were noted between cortical nerve and glial cells, the glial enzyme exhibiting 6-fold higher levels of activity than the neuronal one throughout the first month of postnatal life. The findings emphasize the feasibility as well as the necessity of studies aimed at the elucidation of the cell-specific aspects of the biochemistry of developing nerve and glial cells.  相似文献   
274.
Data in the literature indicate that conditioned responses (CRs) generated by repeated pairing of conditional stimulus (CS) with administration of a neurotropic drug may resemble its unconditional effects or they may be opposite in direction; furthermore, the CRs may change as such pairings are continued. In explanation, it is hypothesized that as in conditioning of physiological reflexes, a CS repeatedly paired with administration of a neurotropic drug eventually comes to activate central“processing” events that are evoked by the“stimulus” properties of the drug,i.e., the effects of the drug at receptor sites inside or outside the pia mater which lie in the afferent arms of“reflex” neural circuits; or, the CS comes to activate central processing events that are evoked by centripetal feedback responses to the effects of the drug at receptor sites in the processing or efferent arms of reflex neural circuits. Depending on the receptor site action of the drug, the conditioned autonomic and/or neuromuscular responses that are observed may be in the same direction as, or opposite in direction to the unconditioned effects of the drug. With continued pairings of CS and drug, the unconditioned processing events evoked by the stimulus properties of the drug, and hence the CRs also, change in consequence of compensatory (sometimes“overshooting”) biochemical alterations proximal to the receptor site of action of the drug, induced by negative or positive neuronal feedback mechanisms. These concepts are utilized in a theory of opiate addiction and relapse.  相似文献   
275.
The continuum of solutions constituting the bargaining set for n-person games in characteristic function form (n ≥ 4) reflects various degrees of determinateness to form a coalition, different requirements of stability, or different levels of competition among the players. At one end of this continuum is the kernel solution. A new solution, called the competitive bargaining set, constitutes the other extreme. It incorporates the concept of a multiobjection, which is based on the idea that threats may be perceived and considered simultaneously even though their simultaneous implementation is impossible.For the simple homogeneous majority games [n ? 2, 1, 1, …, 1] the competitive bargaining set (1) yields unique outcomes for each coalition structure, (2) coincides with von Neumann and Morgenstern's main simple solution for certain coalition structures, and (3) converges to Shapley value as n → ∞ when the grand coalition forms.Mathematical and experimental implications of the new solution are discussed briefly.  相似文献   
276.
The purpose of this research was to determine the specific behaviors and cues which 104 assessors perceived as indicating the presence of psychological variables shown to be related to competent job behavior. The cue systems utilized were found to be reminiscent of theory Y conceptions of effective job behavior. Implications of the lack of correlation of cue utilization with assessor characteristics are discussed.  相似文献   
277.
278.
279.
In spite of a clear increment in absolute thresholds as an effect of self-adaptation, the electrically provoked taste sensation does not show a reduction in subjective intensity during the protracted stimulation time. Chemical cross-adaptation effects on the threshold and suprathreshold levels of electrical taste are observed only when the adapting solutions are electrolytes regardless of their taste qualities. It seems that the stability of perceived intensity during current flow is principally due to some irritation of the sensitive tissue of the tongue, whereas cross-adaptation effects may be attributed to the potential changes across the excitable membranes caused by electrical properties of adapting electrolytic solutions.  相似文献   
280.
Attentional control is thought to play a critical role in determining the amount of information that can be stored and retrieved from visual working memory (VWM). We tested whether and how task-irrelevant feature-based salience, known to affect the control of visual attention, affects VWM performance. Our results show that features of a task-irrelevant color singleton are more likely to be recalled from VWM than non-singleton items and that this increased memorability comes at a cost to the other items in the display. Furthermore, the singleton effect in VWM was negatively correlated with an individual’s baseline VWM capacity. Taken together, these results suggest that individual differences in VWM storage capacity may be partially attributable to the ability to ignore differences in task-irrelevant physical salience.  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