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   27377篇
  免费   396篇
  国内免费   5篇
  2024年   16篇
  2023年   95篇
  2022年   127篇
  2021年   167篇
  2020年   206篇
  2019年   216篇
  2018年   3763篇
  2017年   3084篇
  2016年   2506篇
  2015年   389篇
  2014年   320篇
  2013年   1086篇
  2012年   1077篇
  2011年   2855篇
  2010年   2800篇
  2009年   1646篇
  2008年   2084篇
  2007年   2477篇
  2006年   351篇
  2005年   487篇
  2004年   345篇
  2003年   292篇
  2002年   228篇
  2001年   104篇
  2000年   155篇
  1999年   94篇
  1998年   63篇
  1997年   49篇
  1996年   42篇
  1995年   28篇
  1994年   34篇
  1993年   26篇
  1992年   45篇
  1991年   35篇
  1990年   36篇
  1989年   35篇
  1988年   31篇
  1987年   27篇
  1986年   15篇
  1985年   21篇
  1984年   22篇
  1983年   16篇
  1979年   18篇
  1976年   19篇
  1974年   17篇
  1973年   18篇
  1972年   14篇
  1971年   18篇
  1968年   23篇
  1965年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Stig Fhanér 《Psychometrika》1966,31(2):267-269
It is shown that certain correlation measures suggested by information theory are simple functions of the determinants of the correlation matrices involved, if multivariate normality is assumed. This illuminates and in a sense strengthens Rozeboom's point in [3], that information theoretical statistics have classical correlational counterparts.  相似文献   
73.
74.
75.
In the Critique of Judgement, Kant, despite his strong condemnation of rhetoric, introduces the figure of hypotyposis at the very moment he sets out to tackle the philosophical problem of presentation as such. This study holds that this choice of the rhetorical term is not fortuitous. Its connotations of vivid illustration, synopsis, and moral grandeur serve Kant in arguing that, on a transcendental level, presentation secures the mind's life, unity, and self-affection. Although of rhetorical origin, hypotyposis is thus shown to link up with a specifically philosophical meaning of the term in the writings of Aristotle.  相似文献   
76.
This paper describes a possible near-death experience (NDE) among the Mapuche people of Chile. The individual reporting the experience was in a cataleptic-like state for two days, the experience itself occurring at the end of this period. Some common features of NDEs, such as encounters with deceased people and being sent back, are present, together with clear evidence that past and present cultural environment shape in part the content of mental experiences.This work was funded in part by the University of Chile (DTI Project Q-3064).The author thanks Editorial Andrés Bello for permissionto translate the near death account into English.  相似文献   
77.
In this paper a method is outlined for measuring the diversity of the results of applied R&D with the use of IPC (International Patent Classification). The method has been tested in the contexts of the academic physical, engineering, and chemical institutes. The trend of applied research at a given institute increases both at the level of classes and subclasses, and at the IPC level. Inventions developed within specializations at each institute have a greater efficiency than other forms of inventive activity. The objective was to seek the optimal extent of diversification of applied R&D, which would simultaneously ensure the preservation of the scientific specialization of an institute, the high level of scientific research associated with developing innovations, and the high overall efficiency of each institute.  相似文献   
78.
Finland has followed the Scandinavian model of the welfare state in which the level of state activism is high, the economic pressures on the scientific activities are strong, and the left-wing parties and the Center Party have formulated the main ideas. In the 1970s welfare ideology was adopted in science policy by emphasizing the promotion of socially relevant scientific activities and the expansion of the university system as a means of effecting equal opportunity. Currently, the trend is toward a mixed welfare economy. Programs have been prepared in spite of the radical cut in government expenditure, and without a consideration of the long-term consequences.  相似文献   
79.
80.
When an observer views a moving scene binocularly, both motion parallax and binocular disparity provide depth information. In Experiments lA-1C, we measured sensitivity to surface curvature when these depth cues were available either individually or simultaneously. When the depth cues yielded comparable sensitivity to surface curvature, we found that curvature detection was easier with the cues present simultaneously, rather than individually. For 2 of the 6 subjects, this effect was stronger when the component of frontal translation of the surface was vertical, rather than horizontal. No such anisotropy was found for the 4 other subjects. If a moving object is observed binocularly, the patterns of optic flow are different on the left and right retinae. We have suggested elsewhere (Cornilleau-Pérès & Droulez, in press) that this motion disparity might be used as avisual cue for the perception of a 3-D structure. Our model consisted in deriving binocular disparity from the left and right distributions of vertical velocities, rather than from luminous intensities, as has been done in classical studies on stereoscopic vision. The model led to some predictions concerning the detection of surface curvature from motion disparity in the presence or absence of intensity-based disparity (classically termedbinocular disparity). In a second set of experiments, we attempted to test these predictions, and we failed to validate our theoretical scheme from a physiological point of view.  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