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   692篇
  免费   243篇
  国内免费   51篇
  2024年   3篇
  2023年   16篇
  2022年   9篇
  2021年   20篇
  2020年   26篇
  2019年   34篇
  2018年   42篇
  2017年   35篇
  2016年   37篇
  2015年   15篇
  2014年   26篇
  2013年   83篇
  2012年   17篇
  2011年   26篇
  2010年   17篇
  2009年   18篇
  2008年   22篇
  2007年   23篇
  2006年   30篇
  2005年   20篇
  2004年   23篇
  2003年   21篇
  2002年   16篇
  2001年   22篇
  2000年   10篇
  1999年   12篇
  1998年   11篇
  1997年   11篇
  1996年   14篇
  1995年   11篇
  1994年   16篇
  1993年   19篇
  1992年   18篇
  1991年   15篇
  1990年   12篇
  1989年   7篇
  1988年   10篇
  1987年   7篇
  1986年   19篇
  1985年   12篇
  1984年   13篇
  1983年   10篇
  1982年   14篇
  1981年   18篇
  1980年   15篇
  1979年   17篇
  1978年   29篇
  1977年   25篇
  1976年   29篇
  1975年   11篇
排序方式: 共有986条查询结果,搜索用时 23 毫秒
921.
The U.S. National Assessment of Educational Progress (NAEP), the Third International Mathematics and Science Study (TIMSS), and the U.S. Adult Literacy Survey collect probability samples of students (or adults) who are administered brief examinations in subject areas such as mathematics and reading (cognitive variables), along with background demographic (primary) and educational environment (secondary) questions. The demographic questions are used in the primary reporting, while the numerous explanatory secondary variables, or covariates, are only directly utilized in subsequent secondary analyses. The covariates are also used indirectly to create the plausible values (multiple imputations) that are an integral part of analyses because of the use of sparse matrix sampling of cognitive items. The improvement in the precision of the primary reporting due to the inclusion of the covariates is assessed here and contrasted with the precision of reporting using plausible values created using only the primary demographic variables.The results demonstrate that the improvement in precision depends on the matrix sampling designs for the cognitive assessments. The improvements range from essentially none for the most common designs, to moderate for some less common designs. Consequently, two potential changes in the reporting procedures that could improve the statistical and operational efficiency of primary reporting are (a) eliminate or reduce the collection of covariates and increase the number of cognitive items, (b) to avoid delays, eliminate the covariates from the creation of plausible values used for the primary reports, but include them later when creating public-use files for secondary analyses. The potential improvements in statistical and operational efficiency must be weighed against the intrinsic interest in the covariates, and the potential for small discrepancies in the primary and secondary reporting.Thanks to Donald Rubin, Robert Mislevy, and John Barnard for their helpful comments and computing assistance. This work was supported by NCES Grant 84.902B980011.  相似文献   
922.
We systematically manipulated social proximity to examine its influence on multiple topographies of aggression. Aggression occurred at high levels during close-proximity sessions and at low levels during distant-proximity sessions even though social contact was presented continuously during both conditions. Topographies of aggression emerged sequentially across the close-proximity sessions, and all topographies were reduced to zero following extended sessions of this condition.  相似文献   
923.
对<系辞>等传中论及人性及其与天道之关系的文字,古今学者的理解各有心得.作者认为,行<系辞>论性语义为一阴一阳的运行变化称之为道,人从天道变化中得到了善,人性使天道赋予人的这种善得到了完成和显现.并且认为,<易传>、<中庸>、<孟子>实际都是认为"性自命出,命从天降"的,都是在人性与天道有一致性的意义上肯定人性善的,故否定<易传>有性善论,以为<易>、<庸>、<孟>的人性说致思路数不同的观点,都是不合实际的.作者又认为,将天道赋予人道正义的意义又返而以支撑人道原则,自<易传>已然,宋儒的天道性命学说与此是一脉相承的,故否定理学与先秦儒学的联系也是不合事实的.作者还认为,中国古代思想家宣扬性善论的主题是弘扬理性,强化人们对人道的自觉与自信,其中凝聚的积极善良的正气,乃是我们民族文化的元神.  相似文献   
924.
Radical activist organizations face the complex task of managing their identity so as to draw political attention but also to appear legitimate and thus gain public support. In this article we develop a picture of the identities of Sea Shepherd Conservation Society (SSCS) members, a group mostly known for their direct action against whaling, via a thematic analysis of material from the SSCS website and interviews with SSCS members. In online commentary, founder Captain Paul Watson establishes several deliberately paradoxical notions of who the Sea Shepherds are. We relate these identity statements to interviews with core activists to examine how they manage the identity conflicts resulting from the group identity, such as being seen as “pirates” and “hard lined vegans.” We found that SSCS positions themselves as a diverse and unstructured organization, yet distinctively passionate and willing to take action where others will not. The implications of this research are discussed in relation to the importance of understanding the constraints and conflicts around political activist identities.  相似文献   
925.
The deformation and failure of the pristine PBX 9501 high explosive are studied experimentally by combining Brazilian disk compression with the digital image correlation (DIC) technique. The Brazilian disk specimen was loaded by a pair of compressive forces across the diameter. The full-field deformation on the surface of the disk, during the loading process, was obtained using DIC on a series of random speckle images acquired during the test. In this series of experiments, we focused on the effect of temperature while keeping the loading speed quasi-static. Tests were conducted under three different temperatures, ?15°C, 23°C, and 50°C. For all testing conditions, it was observed that as the applied load reaches maximum, localized deformation starts at the two regions near the loading points. The localized deformation then proceeds along an irregular path toward the center of the specimen and coalesces. Finally, deformation of the Brazilian disk subjected to cyclic compressive load at ambient temperature was also measured and studied.  相似文献   
926.
Experimental measurements of stress drops and band strains in type-B Portevin–Le Chatelier (PLC) bands were carried out for 5xxx series Al–Mg sheets with Mg content between 1.8 and 4.5?wt%. While the stress drops increase with global strain, the band strain values in all the samples follow a common linear relationship with global strain. The results indicate that the type-B PLC band strain is independent of solute content at given strain rate.  相似文献   
927.
Three experiments tested the effect of an attitude towards an object on the memory judgement of whether this object co-occurred with positive versus negative stimuli. We induced positive or negative attitudes towards novel male stimuli, and paired each man with an equal number of positive and negative animals. In a memory test, participants reported more co-occurrences of same-valence man/animal pairs than opposite-valence pairs. This valence-compatibility effect occurred even when attitudes were induced after the pairing (Experiment 1), when participants knew that each man occurred with an equal number of positive and negative animals (Experiment 2), and in reports of clear memory of pairs that did not co-occur (Experiment 3). The present findings suggest that evaluation causes illusory correlation even when the co-occurring stimuli are not traits or behaviours attributed to the attitude object. The results question the validity of co-occurrence memory judgements as measures of co-occurrence awareness in evaluative conditioning (EC) research.  相似文献   
928.
Research on multiple relationships by practicing psychologists has typically presumed the presence of a professional relationship and focused on the ethicality of subsequent, nonprofessional relationships. Instead, this study focused on the question of what, exactly, constitutes the professional relationship in the first place. Practicing psychologists and undergraduates responded to vignettes portraying various early stages of interaction between a therapist and a prospective client. Participants' responses indicated that determinations of professional relationship establishment, and the ethicality of subsequent nonprofessional relationships, depended upon the degree of engagement. Some differences emerged between perceptions by professionals and nonprofessionals. Ethical and professional implications are discussed.  相似文献   
929.
In this paper, we study corporate social responsibility (CSR) in China through the prism of investments. We work with large stocks and assess their CSR performance from agency CSR data. We formulate Chinese CSR by a multiple objective extension of a traditional portfolio selection model and analytically solve the extension. We also solve the extension by a genetic algorithm and directly evaluate the algorithm's performance against the analytical solution. The multiple objective formulation is tested by randomly choosing nondominated portfolios with out‐of‐sample data to identify nondominated portfolios that outperform the 1/n portfolio (equally weighted portfolio). Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
930.
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