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   4987篇
  免费   222篇
  国内免费   1篇
  2023年   47篇
  2022年   38篇
  2021年   59篇
  2020年   94篇
  2019年   121篇
  2018年   158篇
  2017年   164篇
  2016年   177篇
  2015年   143篇
  2014年   138篇
  2013年   555篇
  2012年   266篇
  2011年   234篇
  2010年   143篇
  2009年   121篇
  2008年   196篇
  2007年   192篇
  2006年   148篇
  2005年   181篇
  2004年   166篇
  2003年   157篇
  2002年   136篇
  2001年   89篇
  2000年   79篇
  1999年   63篇
  1998年   56篇
  1997年   50篇
  1996年   60篇
  1995年   54篇
  1994年   40篇
  1993年   45篇
  1992年   48篇
  1991年   50篇
  1990年   58篇
  1989年   44篇
  1988年   43篇
  1987年   43篇
  1986年   44篇
  1985年   50篇
  1984年   57篇
  1983年   51篇
  1982年   44篇
  1981年   31篇
  1980年   41篇
  1979年   42篇
  1978年   40篇
  1977年   52篇
  1976年   47篇
  1974年   48篇
  1973年   33篇
排序方式: 共有5210条查询结果,搜索用时 31 毫秒
91.
This paper addresses some critical issues in the applicability of quantitative performance measures (including bibliometric, economic, and co-occurrence measures) to the assessment of basic research. The strengths and weaknesses of metrics applied as research performance measures are examined. It is concluded that metrics have a useful role to play in the evaluation of research. Each metric employed, whether bibliometric, economic, co-occurrence, or others, brings a new dimension of potential insight to the complex problem of research assessment. However, when used in a stand-alone mode, metrics can be easily misinterpreted and result in misleading conclusions. Metrics should be an integral part of a more comprehensive approach to research evaluation, in which the leading role is assumed by expert peer review. Under this structure, the reviewers must be broadly constituted, so that the technical correctness of the research approaches being taken (doing the job right) can be evaluated by technical experts and the correctness of the research target (doing the right job) can be evaluated as well. This comprehensive approach insures quality in the implementation of existing research paradigms and allows the introduction of revolutionary new research paradigms as well. The views contained in this paper are solely those of the author and do not represent the views of the Department of the Navy. Ronald Kostoff received a Ph.D. from Princeton University, performed technical and economic research at Bell Laboratories, managed energy programs at U.S. Department of Energy, was Director of Technical Assessment at the Office of Naval Research for many years and presently manages the Navy’s In-House Laboratory Independent Research Program.  相似文献   
92.
There are many conditions in which identification proceeds faster for the global form of a hierarchical pattern than for its local parts. Since the global form usually contains more lower spatial frequencies than do the local forms, it has frequently been suggested that the higher transmission rate of low spatial frequencies is responsible for the global advantage. There are also functional hemispheric differences. While the right hemisphere is better at processing global information, the left hemisphere has an advantage with respect to local information. In accordance with the spatial-frequency hypothesis, it has been speculated that this difference is due to a differential capacity of the hemispheres for processing low and high spatial frequencies. To test whether low spatial frequencies were responsible for the global advantage and/or for the observed hemispheric differences, two experiments were carried out with unfiltered and highpass-filtered compound-letter stimuli presented at the left, right, or center visual field. The first experiment, in which the target level was randomized in each trial block, revealed that low spatial frequencies were not necessary for either global advantage or for hemispheric differences. Highpass filtering merely increased the response times. In the second experiment, the target level was held constant in each block. This generally increased the speed of responding and produced interactions between filtering and global-local processing. It was concluded that both sensory and attentional or control mechanisms were responsible for global precedence and that the hemispheres differed with respect to the latter.  相似文献   
93.
Molecular sequence data, made available in the last 15 years or so, have led to the classification of living cells into three phylogenetic domains: Bacteria, Archaea, and Eucarya. All the organisms that have been tested belonging to either domain were capable of mounting a stress response with essentially the same characteristics, regardless of the stressor. The protagonists in the cell's stress response are the stress genes and their protein products. Some of the latter are molecular chaperones. Under physiological conditions, these chaperones aid other cellular proteins to fold properly and achieve a native -functional- configuration, and to translocate from the place of synthesis to the cell's locale in which they will operate. In a stressed cell, the stress proteins that are chaperones protect other molecules from denaturation and help those partially damaged to regain a functional configuration. Thus, cell death is avoided and recovery is enhanced. The study of stress genes and proteins has progressed considerably in organisms belonging to the domains Bacteria and Eucarya. Less is known about the archaeal stress genes. Here, research with an organism from the Archaea is discussed, focusing on the stress genes of the hsp70 (dnaK) locus. Future perspectives for basic and applied research within the health sciences and biotechnology industries are presented.  相似文献   
94.
95.
This study evaluated the hypothesis that shyness is uniquely associated with delayed development of personal resources for dealing with career tasks during the college years. In addition to shyness, the set of relevant personality factors included academic self-esteem and dysphoria. Canonical correlation and semipartial analysis were used to assess the mutual and unique variance associated with these three personality factors and a set of career development variables pertinent to college students in late adolescence. Results revealed that shyness was uniquely related with vocational self-concept crystallization and aspects of vocational maturity (e.g., attitudes toward planning), but unrelated with indexes of self and environmental exploration. Academic self-esteem was only related to vocational self-concept, while dysphoria evidenced no unique association with any career variables. Implications of the expected and unexpected findings are discussed.  相似文献   
96.
The origins of fear and phobia of blood, injury, and injections were investigated in a sample of 128 fearful university students. Based on Mutilation Questionnaire scores, subjects were designated as common fear, high fear, or phobic. Ss reports of their onset experiences obtained from structured interviews were categorized into one or more acquisition pathways of conditioning, vicarious observation, and information. Of the 73% of Ss who recalled one or more onset experiences, 76% reported conditioning-like events as the primary pathway with the majority reporting fear-related UCSs. Vicarious experiences were reported as primary by 20% and 3% reported information as being primary in their fear onset. Severity of fear was unrelated to the pathway by which it was acquired, to whether the onset was recalled, and if recalled, whether it was due to a single or to multiple traumatic events. Results are discussed in terms of methodological problems of memory issues and means by which data are collected.  相似文献   
97.
Book Reviews     
G rünbaum , A dolf . Validation in the Clinical Theory of Psychoanalysis: A Study in the Philosophy of Psychoanalysis
H ollis , J ames . The Middle Passage: From Misery to Meaning in Midlife
B ertoia , J udi . Drawings from a Dying Child: Insights into Death from a Jungian Perspective
H olt , D avid . The Psychology of Carl Jung: Essays in Application and Deconstruction  相似文献   
98.
W. M. de Muynck 《Synthese》1995,102(2):293-318
The axiomatic approaches of quantum mechanics and relativity theory are compared with approaches in which the theories are thought to describe readings of certain measurement operations. The usual axioms are shown to correspond with classes of ideal measurements. The necessity is discussed of generalizing the formalisms of both quantum mechanics and relativity theory so as to encompass more realistic nonideal measurements. It is argued that this generalization favours an empiricist interpretation of the mathematical formalisms over a realist one.  相似文献   
99.
A DEVELOPMENTAL DEFICIT IN LOCALIZING OBJECTS FROM VISION   总被引:3,自引:0,他引:3  
Abstract— We describe a college student, A. H., with a developmental deficit in determining the location of objects from vision. The deficit is selective in that (a) localization from auditory or tactile information is intact, (b) A H reports the identity of mislocalized objects accurately, (c) visual localization errors preserve certain parameters of the target location, and (d) visual localization is severely impaired under certain stimulus conditions, but nearly intact under other conditions. These results bear on the representation and processing of location information in the visual system, and also have implications for understanding developmental dyslexia.  相似文献   
100.
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