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   39735篇
  免费   1475篇
  国内免费   18篇
  2020年   388篇
  2019年   406篇
  2018年   548篇
  2017年   557篇
  2016年   637篇
  2015年   493篇
  2014年   568篇
  2013年   2832篇
  2012年   1063篇
  2011年   1045篇
  2010年   692篇
  2009年   679篇
  2008年   963篇
  2007年   937篇
  2006年   832篇
  2005年   812篇
  2004年   735篇
  2003年   696篇
  2002年   742篇
  2001年   1267篇
  2000年   1247篇
  1999年   883篇
  1998年   401篇
  1997年   384篇
  1992年   791篇
  1991年   754篇
  1990年   775篇
  1989年   727篇
  1988年   669篇
  1987年   669篇
  1986年   681篇
  1985年   714篇
  1984年   623篇
  1983年   557篇
  1982年   415篇
  1981年   435篇
  1979年   628篇
  1978年   480篇
  1977年   415篇
  1976年   396篇
  1975年   583篇
  1974年   672篇
  1973年   694篇
  1972年   573篇
  1971年   557篇
  1970年   513篇
  1969年   550篇
  1968年   680篇
  1967年   652篇
  1966年   591篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
A cost-benefit analysis of demand for food.   总被引:20,自引:17,他引:3       下载免费PDF全文
Laboratory studies of consumer demand theory require assumptions regarding the definition of price in the absence of a medium of exchange (money). In this study we test the proposition that the fundamental dimension of price is a cost-benefit ratio expressed as the effort expended per unit of food value consumed. Using rats as subjects, we tested the generality of this "unit price" concept by varying four dimensions of price: fixed-ratio schedule, number of food pellets per fixed-ratio completion, probability of reinforcement, and response lever weight or effort. Two levels of the last three factors were combined in a 2 x 2 x 2 design giving eight groups. Each group was studied under a series of six FR schedules. Using the nominal values of all factors to determine unit price, we found that grams of food consumed plotted as a function of unit price followed a single demand curve. Similarly, total work output (responses x effort) conformed to a single function when plotted in terms of unit price. These observations provided a template for interpreting the effects of biological factors, such as brain lesions or drugs, that might alter the cost-benefit ratio.  相似文献   
153.
Two experiments investigated the effects of successive reinforcement contexts on choice. In the first, concurrent variable-interval schedules of primary reinforcement operated during the initial links of concurrent chains. The rate of this reinforcement arranged by the concurrent schedules was decreased across conditions: When it was higher than the terminal-link rate, preference for the higher frequency initial-link schedule increased relative to baseline. (During baseline, a standard concurrent-schedule procedure was in effect). When the initial-link reinforcement rate was lower than the terminal-link rate, preference converged toward indifference. In the second experiment, a chain schedule was available on a third key while a concurrent schedule was in effect on the side keys. When the terminal link of the chain schedule was produced, the side keys became inoperative. Availability of the chain schedule did not affect choice between the concurrent schedules. These results show that only when successive reinforcement contexts are produced by choice responding do those successive contexts affect choice in concurrent schedules.  相似文献   
154.
In a study of air traffic controllers, religious differences are found in the way Type A behavior is associated with several health status indicators. Associations between the Jenkins Activity Survey (JAS) and physical illness incidence, health-promotive behavior, diastolic and systolic blood pressure, subjective distress and impulse control problems, and alcohol consumption are examined by religious attendance, religious affiliation, and change in affiliation. Findings confirm that Type A does not vary significantly by religion. However, there are several significant findings between Type A and various health indicators. Type A is associated with illness incidence, overall and more strongly in several religion, subgroups. Type A and alcohol consumption are related positively in Protestants and converts, and negatively in churchgoing Catholics. Type A is related to impulse control problems in churchgoing Protestants and to subjective distress in churchgoing Catholics. Finally, in individuals with weak or no religious ties, Type A is associated with lower blood pressure. This last finding suggests that in some people (for example, the irreligious or unchurched), the coronary-prone behavior pattern may have cardiovascular effects which are salutary in at least one respect.The authors wish to thank Dr. Kyriakos S. Markides and Laura A. Ray for their assistance with this study. Address requests for reprints to Dr. Levin at the Institute of Gerontology, 300 North Ingalls, Ann Arbor, MI 48109.  相似文献   
155.
156.
157.
This report examines two methodologic concerns pertaining to use of the cloze procedure in studying the predictability of schizophrenic speech, scoring criteria and raters' education (at or below college level). We find that two strategies for scoring the predictions of raters, one requiring the exact word, the other permitting a reasonable synonym, do not appear to differ in distinguishing groups of patients. The accuracy of raters' guessing is, however, correlated with raters' education: the more educated the rater, the more accurate the guessing. Thought-disordered schizophrenic speech is significantly less predictable than that of nonthought-disordered schizophrenics and normal controls when scored by less educated raters. These differences diminish when more highly educated raters are used. We conclude that raters' education can influence the sensitivity of cloze analysis.  相似文献   
158.
Individuals with stronger sex-role identities may be expected to show greater conformity to sex-typed behaviors. Proceeding from this assumption, the sex-role status and sex of students using different styles of carrying books were compared. This study also examined whether over-all hand preference or age were related to carrying styles or sex-role status. Subjects completed a questionnaire comprised of the 24-item Personal Attributes Questionnaire of Spence and Helmreich, a 6-item scale of hand preference and a self-rating of sex-role identity. Afterwards, each subject's carrying style was covertly observed and recorded. Most subjects carried their materials in a sex-typical way or in book bags (for which no sex-typed carrying styles were discovered). As in previous studies, men in this study scored higher than women on masculinity and androgyny and lower on femininity. Hand preference was not related to sex-role status. Carrying style was not significantly correlated with any of the predictor variables for men, perhaps because almost no variance in carrying style was observed among them. Women who used masculine carrying styles tended to be older, have greater instrumentality, and a more masculine identity.  相似文献   
159.
This essay reports a program of research as the occupational and personal stress experienced by contemporary American clergy. Three studies are reported. In the first survey a group of largely Roman Catholic religious reported less stress than the general population. In a replication of this investigation on over 510 Protestant clergy this impression of less experienced stress and greater personal resources was confirmed. In the most recent study of clergy in Southern California, a mixed picture was observed. Although the impression of less overall stress was confirmed, great differences in layclery role expectations were observed.He is the coauthorof Clergy Malpractice: How to Care Carefully (Westminster Press, 1986) and is engaged in a variety of ministerial studies.Paper presented at the meeting of the International Council of Psychologists, Mexico City, September, 1984.  相似文献   
160.
Of 1240 first-time consultations in the neuropsychiatric clinic of the Gondar College of Medical Sciences in an eleven-month period during 1985 and 1986, 152 patients came seeking relief from seizures. This paper deals with the origins and background of diagnostic, differential diagnostic, and therapeutic problems, and with problems of social rehabilitation. While in such a tradition-bound society certain hypotheses continue to have an unfavorable effect, there are unmistakable signs of positive change against a background of rapid social change. Conclusions are drawn for the better management of epileptic patients in developing countries.  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