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   54094篇
  免费   2206篇
  国内免费   30篇
  56330篇
  2020年   641篇
  2019年   788篇
  2018年   1129篇
  2017年   1116篇
  2016年   1188篇
  2015年   803篇
  2014年   971篇
  2013年   4750篇
  2012年   1749篇
  2011年   1894篇
  2010年   1109篇
  2009年   1112篇
  2008年   1726篇
  2007年   1715篇
  2006年   1499篇
  2005年   1363篇
  2004年   1340篇
  2003年   1205篇
  2002年   1248篇
  2001年   1773篇
  2000年   1679篇
  1999年   1291篇
  1998年   687篇
  1997年   587篇
  1996年   536篇
  1995年   543篇
  1994年   517篇
  1993年   529篇
  1992年   1035篇
  1991年   971篇
  1990年   958篇
  1989年   871篇
  1988年   827篇
  1987年   815篇
  1986年   822篇
  1985年   871篇
  1984年   680篇
  1983年   595篇
  1982年   497篇
  1979年   670篇
  1978年   503篇
  1976年   459篇
  1975年   601篇
  1974年   631篇
  1973年   597篇
  1972年   543篇
  1971年   474篇
  1968年   544篇
  1967年   543篇
  1966年   478篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
We prove that there are two involutions defined by monadic terms that characterize Monadic Algebras. We further prove that the variety of Monadic Algebras is the smallest variety of Interior Algebras where these involutions give rise to an interpretation from the variety of Bounded Distributive Lattices into it.Research funded by Fondecyt, project N 764-1987.  相似文献   
162.
We obtain in this paper a representation of the formulae of extensions ofL by generalized quantifiers through functors between categories of first-order structures and partial isomorphisms. The main tool in the proofs is the back-and-forth technique. As a corollary we obtain the Caicedo's version of Fraïssés theorem characterizing elementary equivalence for such languages. We also discuss informally some geometrical interpretations of our results.  相似文献   
163.
164.
The purpose of the present study was to determine whether the sex role orientations of male and female collegiate athletes were more similar in team sports than in individual sports. It was predicted that females in masculine-oriented team sports (basketball and volleyball) would exhibit sex role orientations more similar to those of their male counterparts than would females in individual sports (track/field and swimming). To test this notion the S. L. Bem (The Measurement of Psychological Androgyny, Journal of Consulting and Clinical Psychology, 1974, 42, 155–167) Sex Role Inventory was administered to 381 athletes from 37 National Collegiate Athletic Association institutions. The median-split procedure (S. L. Bem, On the Utility of Alternative Procedures for Assessing Psychology Androgyny, Journal of Consulting and Clinical Psychology, 1977, 45, 196–205) was used to classify subjects as masculine, feminine, androgynous, or undifferentiated. Separate Gender × Sex Role Orientation chi square tests were performed on the frequency data of team and individual sport athletes. The results indicated no significant differences in the sex role orientations of male and female team sport performers, with the greatest proportion (66%) having a masculine (33%) or androgynous (33%) orientation. For individual sports there was a significant difference in the sex role orientations of males and females. The highest proportion of females were classified as feminine (37%) and the lowest proportion were classified as masculine (11%). Individual sport males were somewhat evenly distributed among the four sex role orientation categories, with the highest proportion classified as undifferentiated (36%). It was concluded that sex role orientation of elite female athletes may be associated with the male appropriateness of the sport in which they participate.  相似文献   
165.
In the mind of many people chance and luck act as real but different causes of events. Even in strictly defined situations as casino gambling, people may perceive influences of luck that help to overcome the negative expectancy defined by the rules of chance. Interviews with gamblers in casinos confirmed this idea. In two experiments it was established that the distinction between chance and luck are also made by ordinary subjects in everyday situations. The results revealed that chance is perceived to operate when an event is surprising, an unexpected coincidence. Luck is perceived when an event implies the escape from negative consequences, or the achievement of something that is important and difficult. The distinction between chance and luck can explain why people are trapped by the illusion of control, even when it is clear that they have no influence on the physical causation determining the outcomes of events. They cannot change the outcome of the roulette wheel, but they can employ their luck, which helps them to place their bets on the winning number.  相似文献   
166.
Computerized career information and guidance systems, although now commonplace, have received little psychometric scrutiny. The authors argue for examining these systems in the same way in which paper and pencil instruments are assessed. Consideration is also given to issues related to programming, technical-service problems, and staffing.  相似文献   
167.
Academically talented students scoring in the 95th and 99th percentiles on the 1986 ACTs were compared to each other and to “high average” students scoring in the 80th percentile in terms of their choices for college majors, extracurricular plans, and desires for services. Academically talented students were found to be narrow in their choices of majors but broad in their extracurricular interests. Although uninterested in personal counseling, they are demanding of career counseling, independent study, and honors opportunities.  相似文献   
168.
169.
We investigated longitudinally the effects of a stroke on the social support systems and well-being of the patient's primary support person, both acutely and as the condition stabilized. Individuals who had suffered a first stroke and a primary support person participated in two waves of data collection, carried out in 6-month intervals beginning 7 weeks after the stroke. Our data show that the prevalence of depressive symptoms is from 2 1/2 to 3 1/2 times higher than rates found among representative samples of middle-aged and elderly populations. Mean level of depression did not change over time, although level of optimism declined significantly. Multiple regression analyses showed that levels of depression and perceived burden in support persons are highly related to aspects of the stroke such as its severity, and that demographic variables such as age and income play a relatively minor role in attenuating these relations in the acute adjustment phase. However, from 7 to 9 months after the stroke, well-established demographic variables such as health, income, and age were significant predictors of depression. Individuals who were older and who had good health and higher incomes were least depressed.  相似文献   
170.
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