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   79215篇
  免费   3097篇
  国内免费   27篇
  82339篇
  2020年   759篇
  2019年   970篇
  2018年   1314篇
  2017年   1378篇
  2016年   1437篇
  2015年   1022篇
  2014年   1237篇
  2013年   5969篇
  2012年   2290篇
  2011年   2516篇
  2010年   1569篇
  2009年   1539篇
  2008年   2203篇
  2007年   2213篇
  2006年   2020篇
  2005年   1788篇
  2004年   1665篇
  2003年   1587篇
  2002年   1744篇
  2001年   2517篇
  2000年   2498篇
  1999年   1889篇
  1998年   919篇
  1997年   806篇
  1996年   791篇
  1992年   1593篇
  1991年   1472篇
  1990年   1481篇
  1989年   1378篇
  1988年   1341篇
  1987年   1282篇
  1986年   1377篇
  1985年   1393篇
  1984年   1167篇
  1983年   1062篇
  1982年   780篇
  1981年   760篇
  1979年   1242篇
  1978年   898篇
  1977年   747篇
  1975年   1072篇
  1974年   1129篇
  1973年   1191篇
  1972年   1024篇
  1971年   948篇
  1970年   870篇
  1969年   939篇
  1968年   1142篇
  1967年   1041篇
  1966年   935篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
Keeping juvenile delinquents in school: a prediction model   总被引:1,自引:0,他引:1  
The purpose of this study was to test an empirically based prediction model of school dropout on a sample of 137 juvenile delinquents, some who have dropped out and some who have remained in school. The specific factors among the many found in previous research that are salient for predicting whether delinquent youths will drop out or remain in school were determined. An important finding of this study is that it required only four factors to yield a high level of prediction: misbehavior in school, disliking school, the negative influence of peers with respect to dropping out and getting into trouble, and a marginal or weak relationship with parents. The four factors identified create a model that is directly applicable to prevention strategies and is extremely parsimonious.  相似文献   
982.
983.
The Extended Objective Measure of Ego Identity Status (EOM-EIS) was examined for reliability and validity among early/middle adolescent subjects. The EOM-EIS represents a combination of the Objective Measure of Ego Identity Status and a structured interview of identity status. The instrument was designed to measure ego identity with regard to occupational, religious, political, philosophical, and social contexts along ideological and interpersonal dimensions. A total of 467 students aged 12 to 18 (median = 15.73) responded to the instrument. In general the results from the analyses of reliability, validity, demographic characteristics, and psychosocial maturity yielded results which parallel the theoretical framework and the results from college-aged subjects.  相似文献   
984.
Why do some pregnant teenagers decide to carry to term while others terminate their pregnancy? This study examined the influence of family relationships and support, religion, and education on the decision to carry or to abort. A nonrandom sample of 43 pregnant Puerto Rican teenagers (21 who carried and 22 who aborted) were interviewed in 1982 using a 34-item interview schedule. It was found that girls in the carry group were more significantly influenced and supported by family and friends than were those in the abort group. Fathers were the least influential persons in both carry and abort groups, while mothers were the most influential in the carry group, and sisters in the abort group. Brothers, boyfriends, and best friends were more influential for carry girls than for abort girls. Contrary to expectations, girls in the abort group reported a greater degree of religiosity than did those in the carry group. Further, girls who received strong support from family and friends reported a higher degree of satisfaction with their decision than did those who received less support. Finally, girls in the abort group were more likely to continue their education than were those in the carry group. Overall, the findings of this study have immediate implications for research and counseling services. Practitioners should focus on the girls in conjunction with their families in order to achieve better results in both treatment and preventive services.  相似文献   
985.
Using a backward-masking paradigm with a bias-free and ceiling-free psychophysical task, we tested hypnotized and control subjects for speed of visual information processing. Approximately half of each group received visual imagery suggestions in an attempt to influence attention. Imagery produced no significant differential effect. Although an absence of a hypnotizability-performance relationship was in keeping with findings of a previous study, those subjects in the present study who performed under hypnosis were, as a group, significantly superior to the other subjects in speed of information processing.  相似文献   
986.
Based upon perceptual studies, the present hypothesis was that different ranges of spatial-frequency information constitute different sources of information for recognition memory. In Experiment 1, 40 subjects were tested with sets of focused and unfocused pictures as inspection and test stimuli. In addition to reporting whether each test picture was believed to be a member of the inspection set or a novel picture, each subject was allowed to adjust the contrast of the stimulus until such a judgment could be made. In Experiment 2, subjects made similar judgments when inspection or test stimuli were flickered (perceptually enhancing low spatial frequencies) or unflickered. Results from both studies were consistent with the experimental hypothesis. Other studies were reviewed, which, together with the present data, lend converging evidence to the spatial-frequency hypothesis.  相似文献   
987.
During October and November of 1983, three subsamples were selected from three schools in Mesa, Arizona: 34 students in 6th grade, 34 students in 8th grade, and 34 students in 10th grade. A battery of Piagetian-type tasks were individually and randomly administered to each subject. Seven tasks examined projective spatial conceptual abilities, and three tasks examined Euclidean abilities. The same battery of tasks was again administered to the same subjects during November and December of 1984 when all the subjects were in the next grade, that is, 7th, 9th, and 11th. Because of attrition, the number of students tested during the second year were 33, 30, and 28, respectively. To test for significant differences between grade levels, a chi-square one-sample procedure was used. Out of a possible 50 tasks, significant differences were detected in 36 (72%). Those findings, along with an examination of the percentage of students passing each task, support the notion of sequential development of spatial conceptual abilities.  相似文献   
988.
In the context of an annual fundraising drive for the American Society, two field experiments were conducted to test the relative effectiveness of suggesting either small or large contributions. In experiment 1, as part of a door-to-door campaign 300 people were randomly assigned to: (a) a standard request for contributions (control); (b) the standard request plus the words, “even a penny will help”; or (c) the standard request plus the words, “a generous contribution would really help.” As hypothesized, asking for a generous contribution significantly decreased the percentage of people who donated and failed to increase the average size of contribution by those who gave. Inconsistent with previous findings, the even-a-penny condition did not increase donating. In the second experiment conceptually similar requests were made in a mail-out campaign: 6,000 requests were made—2,000 suggested relatively small amounts (options beginning at $5); 2,000 suggested large amounts (options beginning at $5); and 2,000 were unspecified with regard to recommended amount (control). As expected, compared to the control condition, asking for small amounts increased the proportion of donors to nondonors without decreasing the average size of contributions, while asking for large amounts decreased the proportion of donors to nondonors without increasing the size of contributions. It is suggested that the findings have important implications for charitable fundraising.  相似文献   
989.
990.
This study examined the effects of academic stress upon components of Type A behavior and cardiovascular reactivity. In a longitudinal design, heart rate and blood pressure responses to the Type A Structured Interview (SI) and additional laboratory challenges were measured in medical students at three points during an academic semester. Sessions 1 and 3 were scheduled during vacation periods; Session 2 took place during an intensive examination week. Results indicated that three “stylistic” components of Pattern A derived from the SI—loud and explosive speech, short response latency, and potential for hostility—increased significantly during the exam period. Similar increases achieved marginal significance for another stylistic component, rapid and accelerated speech. By contrast, global Type A assessments did not increase with academic demands. Cardiovascular reactivity was significantly but only moderately stable across the three sessions, showing less consistency than has been reported in previous research. In addition, there was little evidence in this study that cardiovascular reactivity was potentiated by academic stress or by Type A behavior. These results demonstrate the influence of naturalistic environmental factors on overt behavioral components that have recently been suggested as coronary risk factors. Therefore, it is advisable for future experimental and epidemiological research to examine the social and environmental context in which these behaviors occur.  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