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   48695篇
  免费   1937篇
  国内免费   19篇
  50651篇
  2020年   540篇
  2019年   691篇
  2018年   934篇
  2017年   1022篇
  2016年   1030篇
  2015年   729篇
  2014年   919篇
  2013年   4220篇
  2012年   1643篇
  2011年   1677篇
  2010年   1084篇
  2009年   1054篇
  2008年   1546篇
  2007年   1529篇
  2006年   1393篇
  2005年   1279篇
  2004年   1228篇
  2003年   1164篇
  2002年   1207篇
  2001年   1360篇
  2000年   1268篇
  1999年   1045篇
  1998年   572篇
  1997年   561篇
  1996年   486篇
  1995年   506篇
  1994年   490篇
  1993年   495篇
  1992年   881篇
  1991年   768篇
  1990年   830篇
  1989年   709篇
  1988年   737篇
  1987年   715篇
  1986年   706篇
  1985年   674篇
  1984年   673篇
  1983年   647篇
  1982年   513篇
  1981年   477篇
  1979年   688篇
  1978年   554篇
  1977年   482篇
  1976年   465篇
  1975年   574篇
  1974年   629篇
  1973年   627篇
  1972年   468篇
  1968年   535篇
  1967年   478篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
251.
Tests of central auditory function and measures of receptive and expressive language abilities were administered to 10 children suspected of having central auditory processing disorders. Eight of the 10 subjects displayed expressive language difficulties, suggesting a need to examine more closely the relationship between expressive language and central auditory processing.  相似文献   
252.
This investigation was conducted to examine whether older adults would improve their performance when given statements intended to make them feel important to a research study as well as statements concerning their over-all well-being. Women (n = 14) and men (n = 15) with mean ages of 76.0 yr. and 75.1 yr., respectively, were randomly assigned into a control group, a positive reinforcement group, and a group given statements of personal importance. Dependent measures on a rotary pursuit task, screw-and-nut assembly task, and an interest questionnaire were obtained during three separate visits. Data were analyzed with a 3 x 3 (Groups x Days) analysis of variance. While no significant group effects were found on any measure, a significant main effect was obtained for days, indicative of learning.  相似文献   
253.
The purpose of this study was to investigate differences in function of the tactile sensory system between groups of normal-speaking children and children with articulation problems. This task was accomplished by studying possible tactile threshold shifts occurring during magnitude-estimation scaling of vibratory stimuli presented to the dorsal surface of the tongue. 10 normal-speaking children (M age = 7.8 yr.) and 9 children with articulation problems (M age = 7.5 yr.) participated. The normal-speaking children and articulatory defective children performed differently on the magnitude-estimation scaling task in which threshold was allowed to return to baseline after each stimulus presentation. These two groups of children also showed dissimilar threshold shifts for the suprathreshold intensities employed in the magnitude-estimation scaling.  相似文献   
254.
This paper suggests a method to supplant missing categorical data by reasonable replacements. These replacements will maximize the consistency of the completed data as measured by Guttman's squared correlation ratio. The text outlines a solution of the optimization problem, describes relationships with the relevant psychometric theory, and studies some properties of the method in detail. The main result is that the average correlation should be at least 0.50 before the method becomes practical. At that point, the technique gives reasonable results up to 10–15% missing data.We thank Anneke Bloemhoff of NIPG-TNO for compiling and making the Dutch Life Style Survey data available to use, and Chantal Houée and Thérèse Bardaine, IUT, Vannes, France, exchange students under the COMETT program of the EC, for computational assistance. We also thank Donald Rubin, the Editors and several anonymous reviewers for constructive suggestions.  相似文献   
255.
John Pais 《Studia Logica》1992,51(2):279-316
The properties of belief revision operators are known to have an informal semantics which relates them to the axioms of conditional logic. The purpose of this paper is to make this connection precise via the model theory of conditional logic. A semantics for conditional logic is presented, which is expressed in terms of algebraic models constructed ultimately out of revision operators. In addition, it is shown that each algebraic model determines both a revision operator and a logic, that are related by virtue of the stable Ramsey test.The author is grateful for a correction and several other valuable suggestions of two anonymous referees. This work was supported by the McDonnell Douglas Independent Research and Development program.  相似文献   
256.
We introduce two new belief revision axioms: partial monotonicity and consequence correctness. We show that partial monotonicity is consistent with but independent of the full set of axioms for a Gärdenfors belief revision sytem. In contrast to the Gärdenfors inconsistency results for certain monotonicity principles, we use partial monotonicity to inform a consistent formalization of the Ramsey test within a belief revision system extended by a conditional operator. We take this to be a technical dissolution of the well-known Gärdenfors dilemma.In addition, we present the consequential correctness axiom as a new measure of minimal revision in terms of the deductive core of a proposition whose support we wish to excise. We survey several syntactic and semantic belief revision systems and evaluate them according to both the Gärdenfors axioms and our new axioms. Furthermore, our algebraic characterization of semantic revision systems provides a useful technical device for analysis and comparison, which we illustrate with several new proofs.Finally, we have a new inconsistency result, which is dual to the Gärdenfors inconsistency results. Any elementary belief revision system that is consequentially correct must violate the Gärdenfors axiom of strong boundedness (K*8), which we characterize as yet another monotonicity condition.This work was supported by the McDonnell Douglas Independent Research and Development program.  相似文献   
257.
258.
Twenty male subjects (Ss) were repeatedly confronted for five seconds to pictures with positive, negative and neutral valence. During the picture presentation facial EMG-reactions of five mimic muscles (m. frontalis lateralis, m. corrugator supercilii, m. orbicularis oculi, m. zygomaticus major on the right and left side of the face) were recorded. In addition, heart rate was measured. It could be shown that during repeated presentation of pictures with positive valence the m. orbicularis oculi and the m. zygomaticus major on both sides of the face yielded enhanced average EMG-reactions as compared to the repeated presentation of pictures with negative and neutral valence. During presentation of pictures with negative valence the m. frontalis lateralis and the m. corrugator supercilii revealed enhanced EMG-reactions as compared to the repeated presentation of pictures with positive valence. Furthermore, it could be shown that during the repeated presentation of pictures with positive valence those facial muscles which mainly react during confrontation with pictures of positive valence showed a continuous decrease of EMG-activity. Facial muscles which mainly react during the presentation of pictures with negative valence do not show a continuous decrease in EMG-activity during the course of the repeated presentation of pictures with negative valence. Additionally, the EMG-activity of the m. zygomaticus major on the right and lift side of the face do not differ with respect to the mean activity and the time course during confrontation of pictures with positive valence. The m. orbicularis oculi yielded enhanced EMG-reactions during the presentation of pictures with positive valence as compared to both m. zygomaticus major muscles. The present results are discussed with respect to psychobiological theories concerning facial expression.  相似文献   
259.
A series of experiments investigated whether people could integrate nonspatial information about an object with their knowledge of the object's location in space. In Experiments 1 and 3, subjects learned the locations of cities on a fictitious road map; in Experiments 2, 4, and 5, subjects were already familiar with the locations of buildings on a campus. The subjects then learned facts about the cities on the maps or the buildings on the campus. The question of interest was whether or not these nonspatial facts would be integrated in memory with the spatial knowledge. After learning the facts, subjects were given a location-judgment test in which they had to decide whether an object was in one region of the space or another. Knowledge integration was assessed by comparing levels of performance in two conditions: (a) when a city or a building name was primed by a fact about a neighboring city or building, and (b) when a city or a building name was primed by a fact about a distant city or building. Results showed that responses in Condition a were faster or more accurate, or both faster and more accurate, than responses in Condition b. These results indicate that the spatial and nonspatial information were encoded in a common memory representation.  相似文献   
260.
During the 1990-1991 Persian Gulf conflict an experiment was conducted with Australian university students (N = 200) to investigate whether the social stereotyping of Americans varied with social contextual manipulations related to the hostilities. The study, conducted in two phases at the start and end of the conflict, examined how the assignment of standard stereotypical traits to Americans was affected (a) by the large-scale social change constituted by the war and (b) by variation in the frame of reference provided by relevant comparison groups. The elicited stereotypes were sensitive to both of these contextual variables, demonstrating significant variation and fluidity. Overall, stereotypes of Americans were relatively negative. They were significantly more negative (a) at the end of the war than at the beginning in the restricted frame (when Australia and Britain were comparison groups) and (b) in the first phase of the conflict when the frame was extended to include Iraq as a comparison group. The findings were in line with expectations derived from self-categorization theory (Turner, 1985) that the social categorization of self and other into ingroup and outgroup is inherently variable, comparative and context-dependent. They question the long-held view of stereotypes as fixed, rigid and resistant to change.  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