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   50742篇
  免费   2011篇
  国内免费   25篇
  52778篇
  2020年   514篇
  2019年   585篇
  2018年   870篇
  2017年   825篇
  2016年   898篇
  2015年   665篇
  2014年   781篇
  2013年   4584篇
  2012年   1378篇
  2011年   1473篇
  2010年   910篇
  2009年   867篇
  2008年   1276篇
  2007年   1165篇
  2006年   1064篇
  2005年   896篇
  2004年   882篇
  2003年   891篇
  2002年   866篇
  2001年   1730篇
  2000年   1661篇
  1999年   1233篇
  1998年   532篇
  1996年   608篇
  1995年   581篇
  1994年   555篇
  1993年   547篇
  1992年   1188篇
  1991年   1060篇
  1990年   1091篇
  1989年   984篇
  1988年   963篇
  1987年   929篇
  1986年   938篇
  1985年   921篇
  1984年   806篇
  1983年   668篇
  1981年   522篇
  1979年   722篇
  1978年   565篇
  1975年   683篇
  1974年   726篇
  1973年   743篇
  1972年   726篇
  1971年   635篇
  1970年   569篇
  1969年   594篇
  1968年   704篇
  1967年   596篇
  1966年   586篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
The purpose of this study was to gather evidence on the validity of the Vando R-A Scale, a paper-and-pencil measure of perceptual reactance. The Vando R-A Scale and Petrie's kinesthetic aftereffect measure of perceptual reactance were administered to 46 participants drawn from university undergraduates. The Vando R-A Scale was not a valid measure of perceptual reactance. The continued use of the Vando R-A Scale as an alternate measure of perceptual reactance is contraindicated.  相似文献   
902.
For 40 males who smoked 20 cigarettes a day titratable acidity of the urine was significantly correlated with nicotine/cotinine excretion at several sample intervals, as was urinary pH, but not urinary acidity and daily cigarette consumption or serum COHB.  相似文献   
903.
A general fear of crime victimization led to modified activities in the community and feelings of relative safety in their own area for 132 elderly respondents on a 24-item questionnaire. They held sympathetic views of crime perpetrators as disadvantaged victims of society themselves, but came to the unlikely conclusions that more police control and harsher prison sentences are needed.  相似文献   
904.
Electroencephalographically oriented research on vigilance needs valid measures for assessing the level of vigilance between wakefulness and sleep. When studying different psychologically, psychopathologically, and pharmacologically induced states, special attention has to be paid to minor alterations of the level of vigilance which are reflected, essentially, in topographical changes of alpha-activity (Stage A). Since vigilance is a dynamic process, brief fluctuations in the range of a few seconds must also be recorded. In our opinion existing methods of quantification do not fully meet these demands. We have, therefore, developed a relatively simple procedure which can be characterized as an attempt quantitatively to reconstruct visually, i.e., spatiotemporally defined patterns of vigilance. The usefulness of this method, which also has certain limitations, has been demonstrated in psychopharmacological studies.  相似文献   
905.
9 stutterers and 9 nonstutterers were administered a dichotic digits test under conditions of free recall and directed attention. Analysis indicated right-ear preference for both groups and no differences between the free recall and directed listening conditions. Results are discussed in relation to previous studies in which dichotic digit-stimuli were presented to stutterers.  相似文献   
906.
The parallel-lines illusion provides a prototypical example of visual-size assimilation, where the size of a test element is phenomenally skewed towards (or "averaged with") that of a context element. Most assimilation theories predict that distortion should decrease with spatial separation between context and test lengths. However, there is some disagreement about the nature of the function relating sizes of context and test elements and magnitude of assimilation. The present study tests the limits of assimilation in the parallel-lines configurations by observing the effects of a wide range of context/test size ratios, repeated over two disparate levels of spatial separation. The results replicate and extend 1979 findings by Brigell and Uhlarik, confirming that assimilation rises to a peak at midrange size ratios, only to decrease continuously as the ratios become more extreme. The functions were nonmonotonic and similar in shape for both levels of spatial separation, with an over-all decrease in distortion for configurations with the larger separation.  相似文献   
907.
6 adult subjects (3 men, 3 women) produced highly similar spontaneous speech utterances in quiet and with 90-dB SPL white noise. The frequency of occurrence of perceptual judgments of primary stressing in an utterance was not affected by the masking noise. This finding supplements our previous report that variability for stress production of fundamental frequency (fo) during spontaneous speech was preserved under short-term auditory disruption. Also, it adds further support to the contention that fo is under open-loop regulation.  相似文献   
908.
909.
In this paper, we shall confine ourselves to the study of sentential constants in the system R of relevant implication.In dealing with the behaviour of the sentential constants in R, we shall think of R itself as presented in three stages, depending on the level of truth-functional involvement.  相似文献   
910.
Intermediate prepositional logics we consider here describe the setI() of regular informational types introduced by Yu. T. Medvedev [7]. He showed thatI() is a Heyting algebra. This algebra gives rise to the logic of infinite problems from [13] denoted here asLM 1. Some other definitions of negation inI() lead to logicsLM n (n ). We study inclusions between these and other systems, proveLM n to be non-finitely axiomatizable (n ) and recursively axiomatizable (n < ). We also show that formulas in one variable do not separateLM from Heyting's logicH, andLM n (n < ) from Scott's logic (H+S).  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