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   51229篇
  免费   1991篇
  国内免费   18篇
  53238篇
  2019年   548篇
  2018年   821篇
  2017年   759篇
  2016年   882篇
  2015年   636篇
  2014年   772篇
  2013年   4588篇
  2012年   1372篇
  2011年   1343篇
  2010年   896篇
  2009年   843篇
  2008年   1259篇
  2007年   1204篇
  2006年   1106篇
  2005年   978篇
  2004年   907篇
  2003年   900篇
  2002年   898篇
  2001年   1741篇
  2000年   1685篇
  1999年   1265篇
  1998年   558篇
  1996年   631篇
  1995年   592篇
  1994年   592篇
  1993年   553篇
  1992年   1202篇
  1991年   1118篇
  1990年   1105篇
  1989年   967篇
  1988年   945篇
  1987年   938篇
  1986年   913篇
  1985年   908篇
  1984年   810篇
  1983年   675篇
  1982年   543篇
  1981年   554篇
  1979年   766篇
  1978年   595篇
  1975年   717篇
  1974年   734篇
  1973年   799篇
  1972年   730篇
  1971年   667篇
  1970年   573篇
  1969年   588篇
  1968年   726篇
  1967年   631篇
  1966年   585篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
891.
892.
893.
Aerobic exercise which resulted in a significant improvement in cardiovascular functioning had no more effect on psychological mood states than did the placebo control of participation in nonaerobic recreational games or no exercise and sport at all (N = 430 college students). Beta-endorphin levels with the 41 depressed subjects were not a biochemical link that might explain the possible influence of physical activity on depression.  相似文献   
894.
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   
895.
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   
896.
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   
897.
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   
898.
899.
Subjects seem to react to a word faster than they react to a letter within a word. One interpretation is that words are processed holistically; another is that all visual stimuli are processed in terms of components, but that more stimulus information is available for use when the targets are words than when they are letters within words. The results of three experiments indicate that the word or pattern-level advantage occurs even when the stimulus information in the two situations is equated, but if the perceptual arrays cannot be unitized (e.g., consonant sequences), a pattern-level advantage does not occur. In addition, the experiments provide substantial evidence to indicate that if letter arrays cannot be unitized, then they are processed on a componentby-component basis, rather than holistically. Finally, the appropriate definition ofholistic processing is considered.  相似文献   
900.
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