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   22499篇
  免费   348篇
  国内免费   30篇
教育   16193篇
科学研究   1986篇
各国文化   203篇
体育   1713篇
综合类   34篇
文化理论   189篇
信息传播   2559篇
  2022年   133篇
  2021年   229篇
  2020年   363篇
  2019年   492篇
  2018年   699篇
  2017年   773篇
  2016年   716篇
  2015年   429篇
  2014年   576篇
  2013年   4229篇
  2012年   563篇
  2011年   630篇
  2010年   481篇
  2009年   457篇
  2008年   519篇
  2007年   501篇
  2006年   441篇
  2005年   385篇
  2004年   364篇
  2003年   327篇
  2002年   378篇
  2001年   424篇
  2000年   396篇
  1999年   402篇
  1998年   210篇
  1997年   230篇
  1996年   254篇
  1995年   213篇
  1994年   210篇
  1993年   193篇
  1992年   302篇
  1991年   300篇
  1990年   330篇
  1989年   311篇
  1988年   295篇
  1987年   248篇
  1986年   256篇
  1985年   322篇
  1984年   266篇
  1983年   256篇
  1982年   196篇
  1981年   206篇
  1980年   176篇
  1979年   240篇
  1978年   214篇
  1977年   194篇
  1976年   160篇
  1975年   128篇
  1974年   120篇
  1973年   147篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
922.
G.W.A. Dummer's Electronic Inventions: 1745-1976 (Oxford, England: Pergamon Press, 1976—£5.50 or $10.00)

Carl Dreher's Sarnoff: An American Success (New York: Quadrangle/ New York Times Book Co., 1977—$12.50)

George W. Bartlett, ed. NAB Engineering Handbook (Washington: National Association of Broadcasters, 1975—$45.00; $30.00 to NAB and BEA members)

Richard Veith's Talk-Back TV: Two-Way Cable Television (Blue Ridge Summit. Pa.: TAB Books, 1976—$9.95/5.95)

Dan Rather with Mickey Herskowitz' The Camera Never Blinks: Adventures of a TV Journalist (New York: Morros, 1977—$10.00)

F. Gifford's Tape: A Radio News Handbook (New York: Hastings House, 1977—$12.95/6.95)

F. Earle Barcus' Children's Television: An Analysis of Programming and Advertising (New York: Praeger Special Studies, 1977—price not given, but likely around $18.00)

Douglas Davis and Allison Simmons' The New Television: A Public/Private Art (Cambridge, Mass.: MIT Press, 1977—$14.95)

The Videophile's Newsletter (Jim Lowe, 2014 South Magnolia Drive, Tallahassee, Fla. 32301—$7.50 for five issues)

Separations Procedures in the Telephone Industry: The Historical Origins of a Public Policy, by James W. Sichter (January 1977, Publication P-77-2, 146 pp. $23.40, paper)

The Communications Act Policy Toward Competition: The Sound of One Hand Clapping by Hamilton Loeb (March 1977, Working Paper W-77-1, 68 pp., $ 10.90)

Broadcasting: The Next Ten Years (New York: National Broadcasting Co., Department of Corporate Planning, 1977—apparently free on request, paper)

NFLCP Newsletter (P.O. Box 119, Cambridge, Mass. 02142—$7.50 annually, bimonthly; $15.00 to organizations)

Gary Gerani and Paul H. Schulman's Fantastic Television (New York: Harmony Books/Crown Publishers, 1977—$12.95/5.95)  相似文献   
923.
924.
925.
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   
926.
In this paper, decomposition methods for multidimensional data hypercubes of OLAP systems are investigated. Criteria for reducing the computational complexity of the decomposition methods are presented and comparisons are made with the traditional solutions of multidimensional data analysis problems. Examples illustrating the application of these criteria to investigating the dynamics of computational complexity changes for specific types of reduction problems are considered.  相似文献   
927.
In this paper, a survey and critique are presented of the existing concepts of an information society. The concept of a “modern information society” is introduced. The main components of the information society concept are analyzed, i.e., information, information technologies and the IT workforce (specialists). Changes are considered in the main spheres of human activities. A broad definition of the modern information society is formulated.  相似文献   
928.
929.
The purpose of the study was to identify female students' attitudes toward mathematics when studying under four conditions and to assess the impact of school-type and sex of teacher on students' attitudes toward mathematics. An instrument to measure attitude toward mathematics was administered on a stratified random sample of 240 female students drawn from 5 co-educational and 6 all-girls' secondary schools in Plateau State, Nigeria. The findings suggest that the best environment under which females can learn mathematics is in all-girls' secondary schools where mathematics is taught by female teachers.  相似文献   
930.
Handedness has been studied for association with language-related disorders because of its link with language hemispheric dominance. No clear pattern has emerged, possibly because of small samples, publication bias, and heterogeneous criteria across studies. Non-right-handedness (NRH) frequency was assessed in N = 2503 cases with reading and/or language impairment and N = 4316 sex-matched controls identified from 10 distinct cohorts (age range 6–19 years old; European ethnicity) using a priori set criteria. A meta-analysis (Ncases = 1994) showed elevated NRH % in individuals with language/reading impairment compared with controls (OR = 1.21, CI = 1.06–1.39, p = .01). The association between reading/language impairments and NRH could result from shared pathways underlying brain lateralization, handedness, and cognitive functions.  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