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   43014篇
  免费   673篇
  国内免费   45篇
教育   30958篇
科学研究   3683篇
各国文化   447篇
体育   3501篇
综合类   41篇
文化理论   383篇
信息传播   4719篇
  2021年   428篇
  2020年   683篇
  2019年   956篇
  2018年   1325篇
  2017年   1366篇
  2016年   1294篇
  2015年   770篇
  2014年   1037篇
  2013年   8028篇
  2012年   975篇
  2011年   1085篇
  2010年   825篇
  2009年   826篇
  2008年   929篇
  2007年   875篇
  2006年   802篇
  2005年   706篇
  2004年   711篇
  2003年   607篇
  2002年   656篇
  2001年   784篇
  2000年   829篇
  1999年   763篇
  1998年   445篇
  1997年   444篇
  1996年   536篇
  1995年   430篇
  1994年   451篇
  1993年   398篇
  1992年   604篇
  1991年   611篇
  1990年   613篇
  1989年   622篇
  1988年   567篇
  1987年   536篇
  1986年   542篇
  1985年   634篇
  1984年   515篇
  1983年   521篇
  1982年   415篇
  1981年   424篇
  1980年   409篇
  1979年   548篇
  1978年   445篇
  1977年   404篇
  1976年   340篇
  1975年   287篇
  1974年   279篇
  1973年   308篇
  1971年   259篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
The immediate circumstances of the new Broadcasting Act are discussed. The impact of this legislation on schools broadcasting is then considered in relation to the history of earlier legislation in the UK, and the early responses to the Television Act of 1954. The importance of the personnel involved in television production and their commitment to the values of public service is stressed, and placed against the gloomier forebodings of the pessimists of the past‐‐and of today. The article concludes with the assertion that it is the people in the television industry itself, and the values they hold, that will ensure the continued survival of good schools television.  相似文献   
133.
Time series analysis was used to investigate the hypothesis that during acquisition of a motor skill, knowledge of results (KR) information is used to generate a stable internal referent about which response errors are randomly distributed. Sixteen subjects completed 50 acquisition trials of each of three movements whose spatial-temporal characteristics differed. Acquisition trials were either blocked, with each movement being presented in series, or randomized, with the presentation of movements occurring in random order. Analysis of movement time data indicated the contextual interference effect reported in previous studies was replicated in the present experiment. Time series analysis of the acquisition trial data revealed the majority of individual subject response patterns during blocked trials were best described by a model with a temporarily stationary, internal reference of the criterion and systematic, trial-to-trial variation of response errors. During random trial conditions, response patterns were usually best described by a "White-noise" model. This model predicts a permanently stationary, internal reference associated with randomly distributed response errors that are unaffected by KR information. These results are not consistent with previous work using time series analysis to describe motor behavior (Spray & Newell, 1986).  相似文献   
134.
135.
The American Hospital Association (AHA) Resource Center indexes journals for the Health Planning and Administration (HEALTH) database and Hospital Literature Index (HLI). These journals, designated special list health journals, are selected to provide access to a wide and balanced coverage of hospital and health care administration and health policy literature. This article provides background information on HEALTH and HLI and describes special list health journals in detail (including historical information, information sources, and broad subject divisions). It also discusses AHA policies relating to journal and article selection and current subject distribution of special list health journals.  相似文献   
136.
137.
Efforts to represent knowledge effectively have been central to progress in various aspects of medical informatics. These efforts range from relatively simple "electronic textbooks" to fairly sophisticated knowledge-based systems, which function as well as, or even better than, human experts faced with similar problems. Knowledge bases have been developed in many fields, but the relatively limited domains and structured language of medicine, as well as the importance of information in the provision of good medical care, have made research in medical knowledge representation an area of intense activity. This paper reviews representative knowledge bases and knowledge-based systems in medicine: electronic textbooks such as PDQ and the Hepatitis Knowledge Base (HKB), rule-based systems such as MYCIN, causal models (e.g., CASNET), and hypothesis- or frame-based systems, exemplified by PIP and INTERNIST-1. The paper describes the relationships among divergent approaches and provides a sense of current and future trends. It examines problems in knowledge-based systems, particularly in knowledge representation and acquisition, and the responses to these challenges. The latter include the use of domain-independent software shells for constructing knowledge bases, the adaptation and use of previously existing knowledge bases, and multiple uses of the same knowledge base for different purposes.  相似文献   
138.
139.
Serials, one of the more complicated areas of library technical endeavors, has lacked the benefit of standards for a long time. Even now, with standards beginning to be available, the majority of institutions are not working within standard serials formats. A survey to determine the use of serials standards in libraries was conducted in 1988 by the American Library Association, Resources and Technical Services Division, Serials Section, Committee to Study Serials Standards. In the spring of 1988 a survey was sent to a group encompassing the Association of Research Libraries members, CONSER participants, United States Newspaper Program participants, Microform Project libraries, and some vendors and librarians who attended the Committee meetings on a regular basis. The survey questionnaire assessed the current level of serials standards awareness of librarians and vendors. Topics included the type of serials systems used, standards relevant to serials control and union listing and whether or not they are implemented, types and levels of training staff received in the application of standards, benefits of the standards, and areas where standards are most needed.  相似文献   
140.
As a gatekeeper to medical literature and a critical link in the delivery of information to physicians, the librarian's role raises the issue of the librarian's professional liability. The paper suggests several ways in which liability may attach to the librarian or the librarian's employers. Although the librarian's personal risk is negligible, the physician's exposure due to ineffective library work is substantial since the courts have held that a physician must keep abreast of progress in his field. Librarians can also become associated with professional liability actions as part of a case against a physician or hospital through the legal doctrine of vicarious liability. The paper concludes by suggesting several proactive steps for health sciences librarians to pursue to insulate themselves from professional liability and to insulate physicians and institutions from vicarious liability.  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