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   5546篇
  免费   137篇
  国内免费   224篇
  2023年   15篇
  2022年   21篇
  2021年   40篇
  2020年   39篇
  2019年   42篇
  2018年   156篇
  2017年   163篇
  2016年   238篇
  2015年   141篇
  2014年   76篇
  2013年   156篇
  2012年   336篇
  2011年   334篇
  2010年   106篇
  2009年   105篇
  2008年   112篇
  2007年   135篇
  2006年   133篇
  2005年   1378篇
  2004年   695篇
  2003年   470篇
  2002年   165篇
  2001年   38篇
  2000年   30篇
  1999年   35篇
  1998年   16篇
  1997年   12篇
  1995年   14篇
  1994年   14篇
  1992年   33篇
  1991年   45篇
  1990年   61篇
  1989年   46篇
  1988年   26篇
  1987年   42篇
  1986年   37篇
  1985年   31篇
  1984年   28篇
  1983年   20篇
  1979年   33篇
  1975年   28篇
  1974年   32篇
  1973年   30篇
  1972年   25篇
  1971年   25篇
  1970年   17篇
  1969年   19篇
  1968年   16篇
  1967年   17篇
  1966年   16篇
排序方式: 共有5907条查询结果,搜索用时 15 毫秒
41.
The influence in 8 of our patients with ophthalmic migraine of photic driving with sine-like flashing lights on EEG background activity was checked and the visually evoked potentials following the application of diffused simple light stimuli were analyzed using the recovery cycle technique. The results indicate a slightly increased tonic activity of the structures of the mesencephalic formatio reticularis, such as may be produced by slight functional disturbances. Some vegetative secondary symptoms of migraine attacks and some of the changes in EEG observed in patients with ophthalmic migraine are explicable by such an abnormality.  相似文献   
42.
Twenty six clinically healthy smokers were studied with transient pattern visual-evoked potentials. In comparison with a sample of "normal" subjects we found a difference of some parameters (P less than 0.05): the P2-latency and the interocular difference of latency on average were 6-7 ms respectively 2 ms larger. Thirteen subjects have had a prolonged P2-latency (P less than 0.05) and/or a difference in interocular latencies larger than 5 ms. These findings may suggest on subclinical disturbances of visual system and indicators of an special sensitivity of that person. The findings are possibly related to tobacco-alcohol amblyopia.  相似文献   
43.
Aged rats with extensive prior training on the radial maze retain the capacity for accurate spatial working memory (WM) for at least 3 months without practice. To investigate the temporal limits of this influence of prior experience we compared the reacquisition of spatial WM by a group of experienced 21.5-month-old rats to the original acquisition by naive 3-month-old rats. The aged rats had received 225 radial maze tests between 3 and 11 months of age. Despite 10 months without practice the old rats rapidly reacquired critical performance. Their reacquisition was markedly superior to original learning by the young rats, even when delays as long as 5 h were imposed between the rats' fourth and fifth choices during the daily tests in the eight-arm maze. Additional tests showed that neither young nor old rats employed a response strategy to maintain accurate spatial WM performance. Experience clearly confers long-lived protection against the otherwise deleterious effects of aging on spatial WM, but the mechanism by which this influence arises is unknown.  相似文献   
44.
The ability to think of a previously studied item has often been shown to be impaired when, in one way or another, the extraitem context is changed from study to test. In a series of five experiments, such impairment is induced in a somewhat different way. A fragment (e.g. r-i--rop) of a just-studied word (raindrop) is shown to be less readily completed if it is presented bit by bit (r------p, r----r-p, r-i--r-p, r-i--rop) rather than all at once (Experiments 1, 3, 4, and 5). No such effect is found if the word has not been studied beforehand (Experiments 2, 3, 4, and 5). This pattern of results occurs even when fragments of studied and nonstudied words occur in the same test and under conditions in which subjects cannot tell whether a given fragment is of a studied or nonstudied word (Experiments 4 and 5). In addition, for words that have been studied beforehand, the impairment is shown to increase systematically with the number of steps involved in the presentation of the word fragment (Experiment 3) and also to persist when the time allowed for completion of the final version of the fragment is increased from 4 s to a full minute (Experiment 5).  相似文献   
45.
The somatic and psychosocial development of 80 subjects with manifest affective-phasic psychoses is studied retrospectively and compared with that of an identically sized control group consisting of neuropsychiatrically healthy subjects. Statistically significant differences were found particularly in the answers to questions dealing with social situation and social adaptability. Achievement at school and vocational qualifications were lower among the parents of the patients than among those of the healthy subjects. Characteristic features of the patients' childhood and adolescence were transient depression, often for no apparent cause, and maladaption, and vocational wishes were fulfilled less often than among the controls. The patients experienced greater difficulty in settling in to a new group due to their contact difficulties.  相似文献   
46.
By 48 patients with Wilson's disease the brainstem acoustic evoked potentials were stated. There were 35 pathological findings (73%), 13 were normal (27%). The waves, determined by the middle and upper brainstem (Pons and Mesencephalon) showed most of all pathological changes. Those patients with forms of Wilson's disease called Pseudoskelerose and Pseudoparkinson showed the most pathological findings. But one could watch these findings by about 30% of patients in preclinical stage. This method can possibly be used for early detection of disorders of brainstem functions and in the same way it can be used for control of treatment by patients in preclinical stage.  相似文献   
47.
Facing multiple conflicting goals, consumers may attempt to simultaneously pursue multiple goals by choosing mixed vice–virtue bundles in each consumption episode (mixed approach). Alternatively, they may maximize their pursuit of one goal at a time and sequentially manage multiple goals by alternating between pure-virtue and pure-vice bundles across consumption episodes (extreme approach). The current research proposes that consumer preferences between the two approaches depend on mindset abstraction. Across four experimental studies in the domains of food and financial decision-making, we demonstrate that, relative to an abstract mindset, a concrete mindset increases preference for the extreme approach over the mixed approach. Furthermore, by observing actual food choices over a seven-day period, this research provides a comprehensive picture of how a chronic mindset relates to multigoal management in long-term consumption patterns. The findings have both theoretical implications for the goal literature and managerial implications for marketers and policymakers.  相似文献   
48.
49.
50.
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