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   29142篇
  免费   1292篇
  国内免费   17篇
  2022年   221篇
  2021年   315篇
  2020年   477篇
  2019年   492篇
  2018年   823篇
  2017年   717篇
  2016年   726篇
  2015年   474篇
  2014年   632篇
  2013年   2539篇
  2012年   1194篇
  2011年   1226篇
  2010年   691篇
  2009年   682篇
  2008年   1005篇
  2007年   941篇
  2006年   842篇
  2005年   747篇
  2004年   638篇
  2003年   622篇
  2002年   572篇
  2001年   870篇
  2000年   886篇
  1999年   647篇
  1998年   279篇
  1997年   238篇
  1996年   222篇
  1992年   520篇
  1991年   443篇
  1990年   510篇
  1989年   434篇
  1988年   408篇
  1987年   385篇
  1986年   395篇
  1985年   453篇
  1984年   357篇
  1983年   299篇
  1982年   238篇
  1979年   338篇
  1978年   267篇
  1975年   306篇
  1974年   354篇
  1973年   365篇
  1972年   283篇
  1971年   259篇
  1970年   216篇
  1969年   237篇
  1968年   308篇
  1967年   257篇
  1966年   285篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
Two experiments are reported which investigated how subject gender and time-of-day influenced the estimation of duration and the perception of task-related mental workload. In the first experiment, 24 subjects performed a filled time-estimation task in a constant blacked-out, noise-reduced environment at 0800h, 1200h, 1600h, and 2000h, respectively. In the second experiment, 12 different subjects performed an unfilled time estimation task in similar conditions at 0900h, 1400h, and 1900h. At the termination of all experimental sessions, participants completed the NASA Task Load Index workload assessment questionnaire as a measure of perceived mental workload. Results indicated that physiological response, reflected in body temperature change, followed an expected pattern of sequential increase with time-of-day. However, estimates of duration and the perception of mental workload showed no significant effects for time-of-day. In each of the experiments there were significant differences in time estimation and mental workload response contingent on the gender of the participant. These results are interpreted in light of the previous positive findings for circadian fluctuation in performance efficiency and the equivocal findings of a gender difference in time estimation. A unifying account of these collective results is given based on gender by time-of-day interactional effects. An earlier version of this paper was presented at the 32nd Annual Meeting of the Human Factors Society, Anaheim, CA, October, 1988.  相似文献   
232.
Evidence for central nervous system, and more particularly cortical, etiology of anorexia nervosa is reviewed. Topics covered are neuropsychiatric comorbidity, inheritance patterns, the neurobiology of body-image disturbance and of the eating function, perinatal and alcoholic insult to the brain, neurochemical and neuroelectric disturbance, anatomic and metabolic brain imaging, and neuropsychological impairment. It is concluded that there is indeed an important neuropsychological etiological dimension to anorexia nervosa. The profile most frequently associated with anorexia nervosa is right posterior hypometabolism, followed by right anterior hypermetabolism, both associated with right-sided abnormal electroencephalogram spiking. It is also proposed that bulimia consists of a positive neurological subtype and that restricting anorexia represents a negative neurological subtype. Priorities for further research into anorexia nervosa are specified to include twin adoption studies, brain electrical topography studies, postmortem histological studies, and experimentally inspired neuropsychological studies.  相似文献   
233.
234.
A number of investigators have suggested that affective states influence the focus of attention. One recent proposal is that negative moods increase self-focus. This review considers the evidence that bears on this hypothesis. Conceptual issues pertaining to the construct of self-focus are discussed first. Next, the various parameters that influence attentional focus are presented in order to provide a way of organizing the mood/selffocus literature. Studies that have used state measures of mood and self-focus are considered in this context. Methodological limitations of existing studies are discussed and directions for future work provided.  相似文献   
235.
On 25 September, 1923, two days before his 74th birthday, Ivan Petrovich Pavlov stood before a class of medical students assembled in the auditorium of his Alma Mater, the Military Medical Academy in Leningrad. Pavlov, the recipient of the Nobel prize in medicine in 1904 for his work in physiology, was about to address his first class of the new academic year, and, as was his custom, he had prepared his first lecture on a general theme. This was an especially significant address, however, for in it Pavlov reviewed the impressions he had gathered during his travels in Western Europe and the United States in the summer of 1923, and he criticised the prevailing ideology of Soviet communism by attacking the ideas of Nikolai Ivanovich Bukharin, then the leading expositor of Bolshevik Marxism. An English translation of the lecture is printed below.  相似文献   
236.
237.
238.
Abibliography on subjective contours and a brief summary of trends in research-on-thin problem are presented. The bibliography covers the years 1900–1990 and contains 445 entries, each briefly annotated with a code that indicates the general content and theoretical orientation of the item.  相似文献   
239.
A new method for determining the minimum number of observations per subject needed to achieve a specific generalizability coefficient is presented. This method, which consists of a branch-and-bound algorithm, allows for the employment of constraints specified by the investigator.  相似文献   
240.
This paper studies a class of infinite-valued predicate logics. A sufficient condition for axiomatizability of logics from that class is given.To the memory of Jerzy Supecki  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