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   62171篇
  免费   2492篇
  国内免费   18篇
  2020年   603篇
  2019年   782篇
  2018年   1081篇
  2017年   1096篇
  2016年   1153篇
  2015年   835篇
  2014年   975篇
  2013年   4570篇
  2012年   1827篇
  2011年   1982篇
  2010年   1227篇
  2009年   1231篇
  2008年   1746篇
  2007年   1771篇
  2006年   1607篇
  2005年   1423篇
  2004年   1320篇
  2003年   1224篇
  2002年   1339篇
  2001年   2049篇
  2000年   2006篇
  1999年   1517篇
  1998年   705篇
  1997年   633篇
  1996年   639篇
  1993年   583篇
  1992年   1281篇
  1991年   1182篇
  1990年   1161篇
  1989年   1065篇
  1988年   1056篇
  1987年   1008篇
  1986年   1067篇
  1985年   1083篇
  1984年   916篇
  1983年   830篇
  1982年   604篇
  1981年   586篇
  1979年   978篇
  1978年   710篇
  1975年   807篇
  1974年   863篇
  1973年   950篇
  1972年   812篇
  1971年   763篇
  1970年   669篇
  1969年   699篇
  1968年   894篇
  1967年   815篇
  1966年   684篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
321.
Aging has previously been shown to produce a generalized proportional slowing of all cognitive operations. In contrast, the present results suggested that Alzheimer's disease produces a disproportionate reduction in the speed with which patients carry out one or more mental operations. The tasks that demented patients found particularly difficult involved either a self-directed search of their lexicon or the use of familiarity information.  相似文献   
322.
I investigated adult age differences in the efficiency of feature-extraction processes during visual word recognition. Participants were 24 young adults (M age = 21.0 years) and 24 older adults (M age = 66.5 years). On each trial, subjects made a word/nonword discrimination (i.e., lexical decision) regarding a target letter-string that was presented as the final item of a sentence context. The target was presented either intact or degraded visually (by the presence of asterisks between adjacent letters). Age differences in lexical decisions speed were greater for degraded targets than for intact targets, suggesting an age-related slowing in the extraction of feature-level information. For degraded word targets, however, the amount of performance benefit provided by the sentence context was greater for older adults than for young adults. It thus appears that an age-related deficiency at an early stage of word recognition is accompanied by an increased contribution from semantic context.  相似文献   
323.
In this research we examined race, sex, and age differences in the factorial structure of Liang's (1985) model of subjective well-being that integrates the Affect Balance Scale and the Life Satisfaction Index A. In particular, we viewed the covariance structure of the items as a function of several parameter matrices. We analyzed the factorial invariance by testing hypotheses involving the equivalence constraints of one or more parameter matrices with regard to the following: White and Black subsamples, men and women, and the young-old and the old-old. Data for the research came from the 1974 Harris National Council on Aging Survey, Myths and Reality of Aging in America. Analysis of covariance structures, or LISREL, was used to assess the factorial invariance. Replicated race differences were found in the factorial structure, but sex and age differences were not found. Consistent race differences were found for the second-order factor loadings for negative affect.  相似文献   
324.
Relaxation therapy for tension headache in the elderly: a prospective study   总被引:1,自引:0,他引:1  
We evaluated the effects of an 8-week progressive muscle-relaxation therapy regimen on the headache activity of 10 elderly tension-headache subjects. Posttreatment assessment at 3 months revealed significant decreases in overall headache activity (50% or greater) in 7 subjects. Significant clinical or statistical prepost differences, or both, were also found for the number of headache-free days, peak headache activity, and medication index. This is the first prospective study of tension headache in an elderly population, and, unlike previous retrospective studies, it suggests that relaxation therapy may be an effective intervention in the treatment of such headaches.  相似文献   
325.
Although stress and anxiety have long been assumed to play an exacerbatory role in asthma, no study has systematically documented that daily exacerbations of asthma symptoms are related to stress and/or anxiety. In this study, 24 airways obstruction patients (12 asthmatics and 12 chronic obstructive pulmonary disease patients) were instructed to monitor the severity of daily respiratory symptoms. In addition, subjects recorded their daily anxiety level and the number and perceived impact of daily stressors. The results showed that although there were differences between high- and low-stress days for both groups, there were no differences between groups on symptom severity or between high- and low-anxiety days, as measured by the State-Trait Anxiety Inventory (STAI). Thus, although the number and impact of daily stressors were found to be directly associated with the severity of asthma symptoms, anxiety does not appear to have a direct role in the exacerbation of asthma. The findings failed to support the anxiety theory of asthma but provided an explanation for the poor results obtained in previous treatment studies which employed anxiety management with asthmatics.  相似文献   
326.
Two multidimensional mood-state inventories, the Profile of Mood States (POMS) and the Eight State Questionnaire (8SQ), were administered to 289 Australian college undergraduates. Intercorrelations for the combined 14 subscales were subjected to a higher-order factor analysis in order to elucidate the central clinical states within the mood-state sphere. Results suggested four major state dimensions pertaining to Neuroticism, Hostility/Anger, Vigor, and a combined Extroversion/Arousal-Fatigue entity. Both three- and five-factor solutions were taken out for comparative purposes. Furthermore, separate higher-order factorings of the POMS on normative samples of 350 male and 650 female psychiatric outpatients were conducted, corroborating three of the four central state dimensions, at least in the case of females. The implications of these findings for behavioral assessment are discussed.This study was supported by a Research Development Grant awarded to the author by the University of Melbourne.  相似文献   
327.
A comparison study is an experiment whose primary purpose is to compare directly (regardless of experimental design) at least two different procedures for changing behavior or two or more components of such a procedure. This paper argues that, in spite of their popularity, such studies typically lead to inappropriate inferences with poor generality based on improper evidence gathered in support of the wrong question, thus wasting the limited experimental resources. The discussion considers problems concerning the functions of comparison studies, the nature of the comparisons that are attempted, the generality of their findings, and the limited role that they can play in technological research.  相似文献   
328.
329.
330.
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