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   34367篇
  免费   1429篇
  国内免费   10篇
  2020年   349篇
  2019年   478篇
  2018年   614篇
  2017年   645篇
  2016年   642篇
  2015年   469篇
  2014年   585篇
  2013年   2570篇
  2012年   1059篇
  2011年   1133篇
  2010年   677篇
  2009年   669篇
  2008年   967篇
  2007年   962篇
  2006年   902篇
  2005年   813篇
  2004年   787篇
  2003年   720篇
  2002年   759篇
  2001年   1044篇
  2000年   951篇
  1999年   735篇
  1998年   405篇
  1997年   336篇
  1996年   332篇
  1992年   565篇
  1991年   556篇
  1990年   545篇
  1989年   549篇
  1988年   543篇
  1987年   499篇
  1986年   530篇
  1985年   577篇
  1984年   453篇
  1983年   438篇
  1982年   365篇
  1981年   342篇
  1979年   524篇
  1978年   382篇
  1976年   362篇
  1975年   434篇
  1974年   487篇
  1973年   509篇
  1972年   407篇
  1971年   381篇
  1970年   378篇
  1969年   408篇
  1968年   490篇
  1967年   421篇
  1966年   422篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
262.
Helms (1984) presented a model to explain the influence of Black and White racial identity development on counseling interactions. The purpose of this study was to examine her hypothesis that specific combinations of racial identity attitudes contribute to qualitatively different counseling process and outcome or relationship types.  相似文献   
263.
New measures of practical intelligence and personality traits were assessed for their ability to improve the prediction of performance beyond cognitive ability. Measures of practical intelligence from the newly developed Constructive Thinking Inventory and traits measuring emotional stability and expedience were used as independent variables in regression analyses predicting academic performance, training performance and leadership ratings of 86 student leaders. The constructive thinking scales added significantly to the prediction of academic performance, beyond measures of cognitive ability. Constructive thinking also accounted for unique variance predicting training performance and leadership ratings. Personality traits were unrelated to performance or leadership.  相似文献   
264.
Catharine MacKinnon's investigation of the role of sexuality in the subordination of women is a logical culmination of radical feminist thought. If this is correct, the position of her work relative to radical feminism is analogous to the place Parmenides's work occupied in ancient Greek philosophy. Critics of MacKinnon's work have missed their target completely and must engage her work in a different way if feminist theory is to progress past its current stalemated malaise.  相似文献   
265.
I would like to thank the following people for helpful comments and criticisms: Janet Afary, Paul Buhle, Bud Burkhard, Olga Domanski, Nigel Gibson, Peter Hudis, Martin Jay, Douglas Kellner, Andrew Kliman, Pierre Lantz, Heinz Osterle, Jim Thomas, Lou Turner, and Alan Wald.  相似文献   
266.
267.
Neural networks can be used as a tool in the explanation of neuropsychological data. Using the Hebbian Learning Rule and other such principles as competition and modifiable interlevel feedback, researchers have successfully modeled a widely used neuropsychological test, the Wisconsin Card Sorting Test. One of these models is reviewed here and extended to a qualitative analysis of how verbal fluency might be modeled, which demonstrates the importance of accounting for the attentional components of both tests. Difficulties remain in programming sequential cognitive processes within a parallel distributed processing (PDP) framework and integrating exceedingly complex neuropsychological tests such as Proverbs. PDP neural network methodology offers neuropsychologists co-validation procedures within narrowly defined areas of reliability and validity.  相似文献   
268.
Recently, debate about the distribution of scarce organs for transplantation has focused on whether patients should have the right to place themselves on waiting lists at several transplant centers, thereby gaining an advantage over other potential recipients. This article explores the social and ethical issues raised by multiple listing, contrasting policies adopted at the national level with those implemented in New York State. It concludes by examining the implications of the debate for broader questions about entitlement and access to health care.  相似文献   
269.
With increasing momentum for health care reform, attention is shifting to finance reform that will provide for direct methods for controlling health care spending. This article outlines the two principal paths to direct cost control and outlines a national plan that retains our multiple sources of payment, yet also contains a powerful direct cost control technique: a single fund to finance all health care.  相似文献   
270.
Quantification of a chaotic system can be made by calculating the correlation dimension (D2) of the data that the system generates (Packard et al., 1980). The D2 algorithm, however, requires stationarity of the generator, a feature that biological data rarely reflect (Mayer-Kress et al., 1988). So we developed the "point correlation dimension" (PD2), an algorithm that accurately tracks D2 in linked data of different dimensions (Carpeggiani et al., 1991). We now present a mathematical argument that, for stationary data, individual PD2s converge to D2 and we demonstrate that the algorithm rejects contributions made by bursts of noise. Data were obtained from the surface of the olfactory bulb of the conscious rabbit (64 electrodes, 640 Hz each, 1.3 sec epochs) before and after presentation of a novel or habituated odor. D2 could be calculated in only 1 of 10 novel-odor trials, whereas PD2 could be calculated in all. Both algorithms indicated that a novel odor evokes a spatially uniform dimensional increase. The PD2 uniquely exhibited the dimensional decreases that occur during inspiration and the gradients of mean dimension present during the nonstimulated control state. These control gradients remained unchanged without odor experience, but showed spatially specific PD2 increases following odor habituation. It is interpreted that, 1) the PD2 is sensitive, accurate, and appropriate for dimensional assessment of biological data, 2) that during analysis of unfamiliar information a single global process is transiently evoked in the neuropil, and 3) after experience multiple spatially specific processes tonically map the sites of learning.  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