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   55404篇
  免费   2450篇
  国内免费   28篇
  2020年   626篇
  2019年   697篇
  2018年   1014篇
  2017年   1043篇
  2016年   1112篇
  2015年   832篇
  2014年   942篇
  2013年   4142篇
  2012年   1716篇
  2011年   1745篇
  2010年   1080篇
  2009年   1027篇
  2008年   1473篇
  2007年   1459篇
  2006年   1254篇
  2005年   1131篇
  2004年   1098篇
  2003年   1031篇
  2002年   1014篇
  2001年   1866篇
  2000年   1809篇
  1999年   1277篇
  1998年   570篇
  1997年   506篇
  1996年   473篇
  1992年   1148篇
  1991年   1061篇
  1990年   1093篇
  1989年   985篇
  1988年   973篇
  1987年   917篇
  1986年   972篇
  1985年   1036篇
  1984年   791篇
  1983年   716篇
  1982年   492篇
  1979年   849篇
  1978年   570篇
  1977年   531篇
  1976年   520篇
  1975年   744篇
  1974年   859篇
  1973年   885篇
  1972年   794篇
  1971年   723篇
  1970年   697篇
  1969年   716篇
  1968年   905篇
  1967年   795篇
  1966年   736篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
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   
992.
An experiment was performed with 11 voluntary male subjects to test the effects of moderate doses of alcohol on simple auditory RT in a vigilance setting. Subjects were tested during a 30-min. session, during which signals were presented with an average intersignal interval of 3.75 sec. Subjects responded by pressing a microswitch held in the preferred hand. Analysis indicated that absolute means increased as a function of alcohol dose. With time-on-task alcohol produced a faster increase in RT and especially affected the longest RTs. Number of extreme long reactions (blockings) and mean duration of these reactions increased under alcohol and were directly related to time on task; alcohol produced a much faster increase in number of blockings with time on task. Results were discussed in terms of attentional processes and habituation theory. Some practical implications of the results were pointed out.  相似文献   
993.
Children's perception of parental exercise: influence of sex and age   总被引:1,自引:0,他引:1  
The purpose of the study was to document children's perception of parental exercise, relating these perceptions to (1) the self-reported parents' habits of exercise, and (2) the children's own activity patterns. The subjects were 198 students of both sexes, aged 12 to 14 yr. and enrolled in school Grades 7 to 9. A standard questionnaire assessed their perceptions of parental and personal physical activity. Both parents of each subject also reported their respective levels of habitual physical activity. Congruence between the children's perceptions and the self-reported exercise habits of the opposite-sex parent differed for boys and girls, increasing for boys and decreasing for girls between Grades 7 and 9. No significant associations were observed between the children's perception of parental exercise patterns and their own like habits. This suggests that during adolescence parental influences are minimized by other factors, personal or environmental.  相似文献   
994.
Context-dependent effects on analogical transfer   总被引:1,自引:0,他引:1  
The role of context in facilitating analogical transfer was investigated in two experiments. In both experiments, subjects first read two stories that were analogous to Duncker’s (1945) radiation problem. Later, subjects attempted to solve the radiation problem. In Experiment 1, the radiation problem was presented in a different context than that of the stories, and followed them by 6 min. Transfer was observed in subjects who were prompted to use the earlier stories in solving the problem. However, the solution frequency of subjects not given such prompts did not differ from control levels. In Experiment 2, the radiation problem was presented in the same context as the earlier stories to some subjects, and in a different context to others. The timing of the radiation problem also was varied. When a 6-min interval separated the stories from the radiation problem, transfer was a function of context, with weak transfer being observed in the samecontext condition, and no transfer being observed in the different-context condition. At a 45-sec delay, transfer was again observed in the same~ontext condition, and a nonsignificant trend toward transfer was observed in the different-context condition. The results were interpreted as indicating that context facilitates the retrieval of relevant problem-solving schemas, and as suggesting that the possession of relevant schemas is not sufficient to produce analogical transfer.  相似文献   
995.
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   
996.
997.
Jansen (1984) gave explicit formulas for the computation of the second-order derivatives of the elementary symmetric functions. But they are only applicable to those pairs of items which have unequal parameters. It is shown here that for equal parameters similar explicit formulas do exist, too, facilitating the application of the Newton-Raphson procedure to estimate the parameters in the Rasch model and related models according to the conditional maximum likelihood principle.The author wishes to thank the reviewers for their helpful comments on an earlier draft of this paper.  相似文献   
998.
999.
1000.
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