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   21977篇
  免费   468篇
  国内免费   3篇
  22448篇
  2020年   245篇
  2019年   276篇
  2018年   374篇
  2017年   357篇
  2016年   393篇
  2015年   314篇
  2014年   375篇
  2013年   1625篇
  2012年   687篇
  2011年   666篇
  2010年   451篇
  2009年   406篇
  2008年   554篇
  2007年   575篇
  2006年   515篇
  2005年   473篇
  2004年   422篇
  2003年   380篇
  2002年   421篇
  2001年   859篇
  2000年   832篇
  1999年   586篇
  1998年   218篇
  1997年   211篇
  1996年   208篇
  1992年   470篇
  1991年   443篇
  1990年   452篇
  1989年   386篇
  1988年   372篇
  1987年   368篇
  1986年   349篇
  1985年   357篇
  1984年   326篇
  1983年   271篇
  1982年   206篇
  1979年   325篇
  1978年   226篇
  1977年   199篇
  1976年   193篇
  1975年   267篇
  1974年   329篇
  1973年   317篇
  1972年   256篇
  1971年   256篇
  1970年   222篇
  1969年   253篇
  1968年   281篇
  1967年   276篇
  1966年   205篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
231.
232.
Male rats that had displayed limbic seizures following a single pair of systemic injections of lithium and pilocarpine were trained 2 months later on an operant schedule that required differential low rates of responding (DRL). The seizured rats never acquired schedules that required either 6-sec. or 12-sec. inhibition of responses following a reward; these rats displayed more perseverative responding and shorter interresponse times than controls. Histomorphology indicated severe brain damage primarily within the entorhinal cortices (and adjacent amygdala) and dorsal thalamus.  相似文献   
233.
The effects of the constancy phenomena in vision seem to be to provide information about the environment which is not solely dependent upon the characteristics of shape or size of the retinal image but which is modified by the brain to appear closer to the idealized characteristics of the real object. There is a regression away from the retinal image towards the actual object's characteristics. A plate viewed from an angle tends to look more like a disc than would be predicted from the geometry of perspective. This ability of the brain to impose conditions on perception is a high-level process which may be adversely affected by the depressive action of alcohol on the nervous system. In this case, objects such as road signs, etc. would tend to look smaller and so more distant than when sober if regression is inhibited. Drivers' reactions may be delayed if hazards are seen smaller and further away, thereby increasing the possibility of accident. This research indicates a reduction in phenomenal regression after ingestion of alcohol. There are implications for accident-rates in driving or in industry.  相似文献   
234.
A group of 107 children with vascular diseases of the nervous system aged 3-14 years have been studied. In 100 children of the study group acute disturbances of the brain blood circulation have been found, out of which 37 children were with transitory ischemic attacks; 29 were found to be with brain ischaemia; 22-with haemorrhages (7 cases with subarchnoidal, 9 cases with intracerebral and 6 cases with subarachnoidal-parenchimatose); 5 children had wenous thromboses; 7 children were with spinal strokes. In other 7 children we found the presence of Sturge-Weber syndrome. Congenital vascular malformations have been found in 32 children (30%), out of which 16 children (15%) with loops and stenosis of the extracranial segments of the internal carotid artery, and another 16 children (15%) with AV-malformations. Congenital and acquired heart diseases are found to be primary cause for the strokes in 12 children (11%). Considerable is the rate of the epileptic seizures in the acute stage of the strokes as well as of the residual epileptic syndromes.  相似文献   
235.
Convergent support is demonstrated for the use of seven empirically derived scales of the Ways of Coping instrument developed by Lazarus and his colleagues. While the instrument is widely used, until now the internal consistency of the coping measures and stability of the factor structure have yet to be shown for a sample of employed adults. While type of job and type of coping incident reported are not dependent, analysis indicates that work and nonwork groups differ across several coping dimensions. Research implications and directions are addressed.  相似文献   
236.
Outcome research has shown that partner-spouse support can enhance the therapeutic outcome in a number of clinical problems. In the area of premenstrual tension, studies of treatment have apparently overlooked this issue of partners' support. This study was designed to address how men perceive premenstrual changes. 99 undergraduate men were asked whether they believed that women had premenstrual changes reflected on the 18 unipolar scales of the Premenstrual Assessment Form. Responses suggest that young men acknowledge that some women experience dysphoric features like hostility, mood swings, and low self-esteem as well as physical discomfort and behavioural changes. Clinical implications are outlined.  相似文献   
237.
May's model of pairwise preference determination is used to assess the expected likelihood that a subject's pairwise preference comparisons on three alternatives will be transitive. A closed form representation for this expected likelihood is obtained for each situation considered. When the subject is assumed to act precisely according to rankings on attributes with May's model, the computed expected likelihoods the relatively large. When the subject becomes a probabilistic chooser, as defined in a specific manner, expected likelihoods of transitivity decrease significantly from corresponding values with May's model. For a probabilistic Chooser, there is a significant likelihood that the subject might yield transitive pairwise preferences substantially different than the results suggested by May's model.This research was supported by a grant from the General University Research Program and through a fellowship from the Center for Advanced Study, both of the University of Delaware. Very helpful input from John H. Antil, Meryl P. Gardner, and James M. Munch is also acknowledged.  相似文献   
238.
The number of active sweat glands (PSI), heart rate, systolic (SBP) and diastolic blood pressure (DBP) were assessed every 2 minutes in 109 male blood donors. Three measurements were taken at the beginning (adaptation phase), three later but before blood donation (baseline), one during the venous puncture (phase 3), three thereafter but still during donation (phase 4), and four after removal of the cannula (phase 5). Analysis of variance yielded significant differences between phases; PSI and SBP behaved similarly, decreasing from adaptation to baseline, rising during puncture, and decreasing again thereafter. Mean within-subject correlations between variables were significantly above 0. Between-subjects correlations were significantly negative for PSI and DBP. This is best explained by the influence of age on both variables. Correlations of PSI values as determined by three raters had a mean of 0.90. The study shows that the PSI is a very sensitive indicator of stress that is easily accessible also in field studies.  相似文献   
239.
In psychophysiology all procedures used are accompanied with changes of general activation level (GAL) of the subjects. In our study these changes are characterized by self-assessment of the internal state and by the mean heart rate (HR) of each period. On the basis of these data group mean auditory evoked potentials (AEPs) were computed. The influence of the GAL on the N 110- and P 190-amplitudes of the AEPs was analysed. There was no effect on the P 190-amplitude whereas the N 110-amplitude shows distinct responses on changes in GAL. These amplitudes diminished when the subjects reported a change of internal state. The diminishing of N 110-amplitudes took place as well at an increase as at a decrease of the internal state factors. Comparing the HR and the N 110 of the AEPs we found an inverse U-shaped dependence. These results are discussed in comparison to the literature. Furthermore a model which could elucidate the observed findings is presented for a critical discussion.  相似文献   
240.
Language impairment was assessed in 33 patients with Alzheimer's disease (AD), in 52 patients with multi-infarct dementia (MID), and in 86 elderly community residents. The investigation included the D-Test Battery based on the Luria's Neuropsychological Investigation for all subjects. An extended battery of Luria's language items was used for 30 demented patients (11 AD and 19 MID patients) and 86 controls. The changes in language functions in normal subjects could be clearly differentiated from those seen in patients with mild dementia. The patients with different degrees of dementia differed also significantly from each other in regard to language impairment. Moreover, patients with AD and MID appeared to have different patterns of language impairment although the severity of dementia and the levels of orientation, mnestic, and conceptual functions were equal. AD was associated especially with a defect in understanding of grammatical structures and MID with disorders in recognition of words, naming, and repetition. The differential diagnostic capacity of 23 selected language items proved to be 97% between AD, MID, and control subjects. The results indicate that the examination of language functions is valuable in the differential diagnosis of dementia.  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