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   13494篇
  免费   131篇
各国政治   703篇
工人农民   542篇
世界政治   829篇
外交国际关系   612篇
法律   8349篇
中国政治   68篇
政治理论   2442篇
综合类   80篇
  2020年   174篇
  2019年   210篇
  2018年   258篇
  2017年   294篇
  2016年   317篇
  2015年   203篇
  2014年   269篇
  2013年   1331篇
  2012年   295篇
  2011年   339篇
  2010年   274篇
  2009年   288篇
  2008年   335篇
  2007年   346篇
  2006年   350篇
  2005年   280篇
  2004年   291篇
  2003年   321篇
  2002年   262篇
  2001年   511篇
  2000年   456篇
  1999年   397篇
  1998年   174篇
  1997年   150篇
  1996年   142篇
  1995年   128篇
  1994年   147篇
  1993年   133篇
  1992年   252篇
  1991年   273篇
  1990年   302篇
  1989年   277篇
  1988年   296篇
  1987年   294篇
  1986年   279篇
  1985年   270篇
  1984年   221篇
  1983年   197篇
  1982年   138篇
  1981年   151篇
  1980年   116篇
  1979年   195篇
  1978年   135篇
  1977年   110篇
  1976年   91篇
  1975年   116篇
  1974年   136篇
  1973年   119篇
  1972年   91篇
  1971年   96篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
In January of 1981 DHHS released its revised regulations for the protection of human subjects. These new regulations established five categories of federally funded research--primarily in the educational, social and behavioral sciences--which, at local Institutional Review Board (IRB) US ISSN (0193-7758) 1168 option, could be made exempt from mandated peer review. A survey of the 562 member IRB system was conducted to determine, among other things, what policies individual review boards had established with regard to these optionally exempted categories. 341 (61%) of the IRBs responded to the survey. Results indicate that the IRBs have overwhelmingly opted to maintain review procedures at some level in each of the "exempted" categories and that these procedures, as well as the other DHHS standards, are being applied almost universally to all research regardless of funding source. This article presents data on IRBs and their implications for the educational, social and behavioral sciences.  相似文献   
62.
63.
Morganthau T  Coppola V  Carey J  Cooper N 《Newsweek》1983,102(6):30-6, 39-40
  相似文献   
64.
65.
66.
Deoxyribonucleic acid (DNA) was isolated from a number of spongy and compact human bone tissue specimens, and the yield was estimated on a "per milligram of starting tissue" basis. DNA was, in addition, isolated from a number of corresponding blood and bone tissue specimens. Spectrophotofluorometry and ethidium bromide visualization on minigels were used to estimate the quantity and degree of degradation of DNA. The DNA from several blood-bone pairs is shown to give concordant restriction fragment length polymorphism (RFLP) typing results by two different typing protocols with five different single-locus probes. DNA from several additional blood-bone pairs is shown to give concordant results for human leucocyte antigen (HLA)-DQ alpha phenotypes following polymerase chain reaction (PCR) amplification and hybridization to specific allele-specific oligonucleotide (ASO) probes, and for the variable numbers of tandem repeats (VNTR) length polymorphisms 3' to the human apolipoprotein B (APOB) gene following PCR amplification with specific primers and analysis of the products by electrophoresis and ethidium bromide visualization.  相似文献   
67.
Narcotics "body packing" can be detected in abdominal X-rays by the ring shadow caused by air trapped in the packs. In a series of 82 cases admitted for abdominal X-ray in Helsinki, Finland, in 1982 through 1988, we encountered 9 (11.0%) true positives, 3 (3.6%) false positives, and 1 (1.2%) false negative. The false positives were due to the constipation often associated with the narcotics abuse. The false negative X-ray diagnosis was attributable to an inexperienced radiologist. False negatives may also be associated with packets containing marijuana, packs with few wrappings, aluminum-foil coated packs, and machine-packed narcotics. Searching for trapped air in radiographs, repeated X-raying by an experienced radiologist, use of computed tomography, or combined urinary drug screening may be applied to diminish false findings and to avoid unnecessary arrest for the purpose of fecal screening over several days.  相似文献   
68.
69.
70.
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