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   16969篇
  免费   1380篇
各国政治   848篇
工人农民   517篇
世界政治   1421篇
外交国际关系   630篇
法律   11099篇
中国共产党   1篇
中国政治   114篇
政治理论   3574篇
综合类   145篇
  2020年   403篇
  2019年   425篇
  2018年   502篇
  2017年   572篇
  2016年   608篇
  2015年   515篇
  2014年   548篇
  2013年   2051篇
  2012年   400篇
  2011年   506篇
  2010年   646篇
  2009年   603篇
  2008年   449篇
  2007年   490篇
  2006年   524篇
  2005年   400篇
  2004年   411篇
  2003年   403篇
  2002年   377篇
  2001年   540篇
  2000年   456篇
  1999年   380篇
  1998年   260篇
  1997年   221篇
  1996年   202篇
  1995年   207篇
  1994年   204篇
  1993年   197篇
  1992年   279篇
  1991年   313篇
  1990年   286篇
  1989年   288篇
  1988年   279篇
  1987年   261篇
  1986年   289篇
  1985年   271篇
  1984年   280篇
  1983年   247篇
  1982年   208篇
  1981年   176篇
  1980年   170篇
  1979年   189篇
  1978年   135篇
  1977年   124篇
  1976年   90篇
  1975年   94篇
  1974年   101篇
  1973年   96篇
  1972年   78篇
  1968年   67篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
981.
This paper describes a collaborative exercise organised under the auspices of the European Network of Forensic Science Institutes (ENFSI). The purpose of this EU (European Union) funded group is to carry out research to enable STR loci to be compared between European laboratories, ultimately leading to the formation of a pan-European database. Accordingly, an exercise was designed to evaluate a prototype STR multiplex system manufactured by Applied Biosystems (ABD). Each laboratory was sent 12 samples to analyse along with a multiplex kit. Of specific interest was the definition of parameters to define the efficiency of the system. Stutter, split allelic peaks (differing by one base), pull-up, heterozygous balance and between locus balance were all objectively measured. Once the important parameters are defined it is possible to directly compare performances of different multiplexes and the different laboratories carrying out the tests. Since the multiplex used was a prototype system, this exercise cannot be regarded as a proficiency test.  相似文献   
982.
The binding of charged substances from external aqueous media to hair has been investigated through the use of fluorescence microscopy. Eleven hair samples, reflecting various ethnic groups and cosmetic treatments, were tested. Rhodamine 6G, a cationic dye representative of drugs such as cocaine and opiates, showed incorporation throughout the hair of all samples except one. In contrast, fluorescein, an anionic dye representative of drugs such as THC carboxylic acid, was not readily incorporated. The incorporation of rhodamine 6G was faster for chemically 'straightened' and bleached African-American female hair than for untreated hair. Incorporation of rhodamine 6G followed a pH dependence, but an ionic strength dependence could not be established. These studies support three postulates: (1) electrostatic interactions explain the preferential binding of cationic drugs of abuse to hair; (2) the hair matrix, or the non-helical portion of hair, is accessible to external solutions and thus subject to contamination; and (3) cosmetic treatments may alter the helical portion of hair thereby increasing its accessibility to external contamination.  相似文献   
983.
984.
Household survey data on age at first use of alcohol, tobacco, marijuana,and hard drugs can be biased due to sample selection and inaccuraterecall. One potential concern is attrition, whereby individuals who getinvolved with substance use at an early age become increasingly less likelyto be surveyed in successive years. A comparison of data from the NationalHousehold Survey on Drug Abuse (NHSDA) with data from a longitudinal studysuggested that attrition might have caused substantially less bias thandid forward telescoping, the inflating of age at first useover time. The evidence of forward telescoping was particularly pronouncedwith respect to age at first use of alcohol. This paper presents a procedurefor correcting the distribution of age at first use for forward telescoping(but not attrition) by viewing a portion of the NHSDA data collected insuccessive years as constituting a cohort study. Results are presented fromapplying this procedure with NHSDA data collected from 1982 to 1995 forrespondents born 1968–1973. The findings suggest that preventionprograms need to be introduced at an earlier age than would be indicatedby uncorrected retrospective data. Other implications are alsohighlighted.  相似文献   
985.
986.
987.
The HIV/AIDS epidemic continues to be a leading public health issue in the United States. During the past decade, the epidemic has shifted away from the gay community, although gay and bisexual men continue to be the largest single HIV exposure category. Now, HIV increasingly affects low-income people of colour in urban areas, as well as women. As AIDS becomes more and more a minority, inner-city disease, public focus on the epidemic as a significant social and political issue is waning. While a full survey of current issues in US law is beyond the scope of this article, the focus here is on current issues that are highly relevant to the direction the epidemic appears to be taking.  相似文献   
988.
Managed care entities face numerous liability issues in today's changing healthcare environment. This Article provides the plaintiff with a comprehensive road map for navigating the many avenues of managed care liability. The author describes ERISA pre-emption provisions and suggests ways plaintiffs' attorneys can strive to narrow the pre-emption. The Article also provides in-depth analysis of each theory of managed care liability that has been litigated against managed care entities to date, and then goes on to explore state laws imposing liability on managed care entities, and how HMO liability is being reformed through legislative action. For plaintiffs' attorneys seeking the full spectrum of theories of managed care liability, or for defendants' attorneys wanting to remain updated on all potential claims to defend, this Article constitutes an extensive primer on the current issues.  相似文献   
989.
990.
Bibliography     
SIMPSON  D. H. 《African affairs》1960,59(237):359-361
This Bibliography, covering items noticed between May and August1960, has been compiled wish the co-operation of Miss Ruth Jones(International African Institute) and Professor T. Heyse (latelyof the Belgian Ministry of Colonies).  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