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   70756篇
  免费   1304篇
  国内免费   3篇
  72063篇
  2020年   782篇
  2019年   985篇
  2018年   1323篇
  2017年   1313篇
  2016年   1419篇
  2015年   1013篇
  2014年   1257篇
  2013年   5888篇
  2012年   2273篇
  2011年   2308篇
  2010年   1397篇
  2009年   1438篇
  2008年   1990篇
  2007年   1977篇
  2006年   1830篇
  2005年   1526篇
  2004年   1585篇
  2003年   1498篇
  2002年   1432篇
  2001年   2234篇
  2000年   2170篇
  1999年   1582篇
  1998年   785篇
  1997年   669篇
  1996年   745篇
  1995年   674篇
  1994年   666篇
  1993年   638篇
  1992年   1312篇
  1991年   1243篇
  1990年   1232篇
  1989年   1183篇
  1988年   1137篇
  1987年   1047篇
  1986年   1051篇
  1985年   1105篇
  1984年   891篇
  1983年   803篇
  1979年   946篇
  1978年   747篇
  1975年   781篇
  1974年   892篇
  1973年   919篇
  1972年   801篇
  1971年   751篇
  1970年   620篇
  1969年   651篇
  1968年   818篇
  1967年   741篇
  1966年   687篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
Patients with insufficient financial resources place physicians in a conflict of interest between the patients' needs and the financial interests of the physician, other patients, and society. Not only must physicians act ethically, but they must avoid liability for violating their legal duties to their patients. The traditional rules of contract and malpractice law that govern the patient-physician relationship do not provide satisfactory guidelines. Better answers are found in the rules of fiduciary law, but only with regard to direct conflicts between patients and physicians and only at the risk of reducing patient access to care. Certain types of legislative action can resolve these conflicts by altering the traditional legal rules, but care must be taken to preserve patient-physician trust, which the legal rules were designed to enhance.  相似文献   
953.
I offer some reminiscences occasioned by the death of Daniel Levinson, a modern pioneer in the study of the human life cycle. I clarify three controversial aspects of Levinson's theory—its universality, the role of critical life events, and the place of relationships—as well as briefly foreshadow findings from his forthcoming book on women. I show that relationships to people, enterprises, and social institutions are the stuff out of which the individual life structure—Levinson's central concept—is formed. Levinson's dream was of a society in which the developmental needs of adults were better understood and met so that they could more generatively fill their roles in the institutions upon which the young depend. He thought this essential to the evolution of a society that would be both more competent and more humane. In this dream, which was a product of his own difficult mid-life transition and a measure of the success he achieved in integrating its polarities, Levinson united a warm, scientific interest in others with an affectionate curiosity about nature.  相似文献   
954.
955.
956.
Presumptions about the functions of the frontal lobes, and the sensitivity and specificity of certain tests to measure frontal lobe functions, are having a substantial influence on both clinical and research conclusions. In this paper the authors examine the details of the studies that have contributed to these presumptions, and find that the evidence to support these conclusions is weak. A detailed evaluation of the evidence relating to the Wisconsin Card Sorting Test and the Thurstone Word Fluency Test is also presented. Finally, the development of the belief that frontal lobe functions can be specifically measured is reviewed. The authors of this paper conclude that the bewildering array of deficits attributed to frontal lesions still seems to prevail.  相似文献   
957.
The present paper selectively reviews the literature which compares full-term and preterm infants' communication with their mothers in the first year of life. The review is focused not only on what differences are found between full-term and preterm infants, but also why such differences exist. Particular emphasis is placed on the importance of interpreting the findings in the light of the developmental phase of the infants, the heterogeneity of the preterm population and the situation in which communication is studied. Most studies were not designed to consider these issues in any detail. Differences with respect to these factors can be found between studies, however, which may have contributed to the often contradictory findings. Consequently, comparisons between these studies provide clues about the effects of these factors on communicative development. The ultimate goal of this review is to point to important directions for future research on early communication in preterm infants.  相似文献   
958.
This short paper proposes a general computing strategy to compute Kappa coefficients using the SPSS MATRIX routine. The method is based on the following rationale. If the contingency table is considered as a square matrix, then the observed proportions of agreement lie in the main diagonal’s cells, and their sum equals the trace of the matrix, whereas the proportions of agreement expected by chance are the joint product of marginals. The generalization to weighted kappa, which requires an additional square matrix of disagreement weights, both matrices having the same order, becomes possible by the use of the Hadamard product-that is, the elementwise direct product of two matrices.  相似文献   
959.
The study included 17 patients, 12 women and 5 men, with a recurrent symptom complex involving chest pain and dyspnoea characterized by inability to get a full breath. Some attacks had subsided spontaneously. Others had lasted hours or days. When examined by fluoroscopy during an attack, each subject was found to have a nearly maximally contracted (flat) diaphragm. In some of them the attack was promptly interrupted by a small intravenous injection of sodium amytal. In others it could be aborted by a conscious effort at full expiration. The syndrome associated with diaphragmatic spasm is discussed in comparison with other noncardiac sources of chest pain and dyspnoea.  相似文献   
960.
Previous research has shown that a task-irrelevant sudden onset of an object will capture an observer’s visual attention or draw it to that object (e.g., Yantis & Jonides, 1984). However, further research has demonstrated the apparent inability of an object with a task-irrelevant but unique color or luminance to capture attention (Jonides & Yantis, 1988). In the experiments reported here, we reexplore the question of whether task-irrelevant properties other than sudden onset may capture attention. Our results suggest that uniquely colored or luminous objects, as well as salient though irrelevant boundaries, do not appear to capture attention. However, these irrelevant features do appear to serve as landmarks for a top-down search strategy which becomes increasingly likely with larger display set sizes. These findings are described in terms of stimulus-driven and goal-directed aspects of attentional control.  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