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   42224篇
  免费   1532篇
  国内免费   20篇
  2019年   446篇
  2018年   669篇
  2017年   718篇
  2016年   742篇
  2015年   528篇
  2014年   631篇
  2013年   3266篇
  2012年   1167篇
  2011年   1246篇
  2010年   766篇
  2009年   716篇
  2008年   1013篇
  2007年   1053篇
  2006年   924篇
  2005年   871篇
  2004年   828篇
  2003年   782篇
  2002年   862篇
  2001年   1379篇
  2000年   1345篇
  1999年   1022篇
  1998年   449篇
  1997年   398篇
  1996年   403篇
  1992年   839篇
  1991年   801篇
  1990年   812篇
  1989年   773篇
  1988年   763篇
  1987年   729篇
  1986年   750篇
  1985年   768篇
  1984年   605篇
  1983年   543篇
  1982年   424篇
  1981年   403篇
  1979年   698篇
  1978年   506篇
  1977年   451篇
  1976年   416篇
  1975年   596篇
  1974年   699篇
  1973年   693篇
  1972年   593篇
  1971年   546篇
  1970年   511篇
  1969年   544篇
  1968年   671篇
  1967年   606篇
  1966年   582篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
The relationship between anxiety and depression was examined in a sample of 106 children and adolescents referred to an outpatient anxiety disorder clinic for children. Twenty-eight percent of patients with DSM-III diagnoses of anxiety disorders displayed a concurrent major depression. Children with anxiety disorders plus major depression were found (1) to be older, (2) to demonstrate more severe anxiety symptomatology, and (3) to be diagnosed with different rates of certain anxiety-disorder subtypes, when compared to anxious patients without major depression. Nondepressed anxious children and adolescents did not differ from a psychopathological control group in severity of either anxiety or depression symptoms.  相似文献   
172.
Force variability in isometric responses   总被引:2,自引:0,他引:2  
In the present study we examined the contribution of different impulse parameters to peak force variability in an isometric task. Five experiments are reported that each held constant a different impulse parameter while allowing the other impulse parameters to vary. The results indicate that change in force level is the parameter that has the greatest effect on peak force variability, although time to peak force and preload also systematically influence response variability. A formula that accommodates the relation between impulse parameters and force variability is proposed. The data suggest that even in isometric tasks, it is the force-time properties of the impulse, rather than discrete parameters such as peak force, that determine the outcome variability.  相似文献   
173.
174.
175.
Differences between a clinical sample of younger (ages 5 to 11) and older (ages 12 to 19) children meeting DSM-III criteria for overanxious disorder (OAD) were examined. Younger and older children were compared in terms of (1) the rates of OAD diagnoses occurring in the two age groups, (2) sociodemographic characteristics, (3) symptom expression, (4) association with other forms of maladjustment, and (5) self-reported anxiety and depression. The prevalence of OAD diagnoses and sociodemographic characteristics did not differ. Although younger and older OAD children showed similar rates of most specific DSM-III OAD symptoms, older children presented with a higher total number of overanxious symptoms than younger children. Older children more frequently exhibited a concurrent major depression or simple phobia, whereas younger OAD children more commonly had coexisting separation anxiety or attention deficit disorders. Older OAD children reported significantly higher levels of anxiety and depression on self-report measures. Findings indicated that the expression of OAD varies by developmental level.  相似文献   
176.
We studied the effect of different postoperative times on the behavioral recovery following brain implants. Adult male rats received cortical tissue grafts 2 weeks after aspiration of the medial frontal cortex. Either 2 (Immediate Group) or 28 (Delay Group) days after grafting, the performance of these rats on a behavioral battery, comprising the Morris water maze task, forepaw use, and grooming, was compared to that of rats with similar lesions and postoperative recovery times but no grafts. Rats tested immediately after receiving implants performed better on the spatial navigation task than rats with similar lesions but no grafts. This improvement, however, was less than that shown by rats with lesions but no grafts permitted to recover for 28 days before testing. In contrast, in the Delay Group, rats with grafts were more greatly impaired than were their operated controls. Neither lesions nor grafts affected grooming although the Immediate Group with grafts were significantly more impaired in using their forepaws during feeding than were any of the other groups. These results lead us to conclude that differing postoperative recovery times and task requirements may account for some of the inconsistent results of the influence of brain grafts on behavioral recovery reported in the literature. We also conclude that cortical tissue implants can have two effects with different time courses and opposite net behavioral effects.  相似文献   
177.
Wistar rats of three age groups were tested in an automated tunnel-maze system of variable geometry to investigate whether changes in spontaneous locomotor activity and in learning and memory develop differentially or in a correlated fashion as a function of age. Senescent (30 months) as well as mature-adult (17 months) rats showed an age-correlated decline of locomotor activity as compared to the mature-young (5 months) group. Both working-memory (measured as within-trial arm discrimination performance) and reference-memory (measured as avoidance of "blind alley" visits) were severely affected in the senescent group, whereas the middle-aged animals suffered only from a working-memory deficit. The findings provide evidence that locomotor deficits do not necessarily interfere in the assessment of age-related changes in cognitive performance. Furthermore the results support the hypothesis that working and reference memory have different underlying physiological correlates and that these neuronal systems are differentially affected by the aging process.  相似文献   
178.
The development of the understanding of affective meaning in music was investigated. Subjects aged 4, 5, 6, and 19 assigned verbal labels to musical segments previously determined by adults to be representative of one of four affects (happy, sad, angry, afraid). Analysis of correct interpretations and errors revealed a pattern of interactions among age, sex, and affect indicating that the ability to verbalize an understanding of affective meaning in music consistent with that of adult subjects is present during the preschool years. Age-related similarities in performance, as well as differences favoring both younger and older subjects, were observed and were discussed in relation to recent research in, and theories of, affective development and communication.The authors thank H. Julia Hannay, Edward Kemery, Shiela MacDonald, and Robert McGrath for their assistance in this research. The conceptual inspiration of Joseph Intrieri is gratefully acknowledged. We also thank Leslie Brody, Robin Hornik, and several anonymous reviewers for their comments on an earlier draft of the paper. Portions of this research were presented at the Southeastern Conference on Human Development, Baltimore, April 1982.  相似文献   
179.
Two experiments replicated Ekman and Friesen's finding of an expression that signals contempt across cultures. The subjects, from West Sumatra, Indonesia, were members of a culture that differs in a number of ways from Western cultures. In one experiment the subjects judged photographs of Japanese and American faces, both males and females, which showed many different emotions. There was very high agreement about which expressions signaled contempt in preference to anger, disgust, happiness, sadness, fear, or surprise. In a second experiment the Indonesian subjects judged expressions shown by members of their own culture, and again there was very high agreement about which expression signals contempt.This study was supported by a grant from the National Institute of Mental Health (MH 41100). Paul Ekman's work is also supported by a Research Scientist Award from the National Institute of Mental Health (MH 06092). Karl G. Heider's work was supported by a grant from the National Institute of Mental Health (MH 38221). We are grateful to Maureen O'Sullivan for her many helpful comments on this report.  相似文献   
180.
A right-handed man suffered a left parieto-occipital cerebral infarction, causing agraphia with Gerstmann's syndrome but without major aphasia, alexia, or apraxia. Oral spelling was superior to written spelling. Experiments were performed involving (1) analysis of errors in writing, (2) tasks of visual imagery, and (3) identifying letters drawn without leaving a visual trace. The results suggest that the agraphia and Gerstmann's syndrome are due to a dissociation of language skills and visuospatial skills caused by a dominant parieto-occipital lesion.  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