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   529篇
  免费   14篇
各国政治   27篇
工人农民   19篇
世界政治   59篇
外交国际关系   42篇
法律   212篇
中国政治   4篇
政治理论   172篇
综合类   8篇
  2023年   4篇
  2022年   4篇
  2021年   2篇
  2020年   8篇
  2019年   6篇
  2018年   8篇
  2017年   22篇
  2016年   5篇
  2015年   9篇
  2014年   8篇
  2013年   108篇
  2012年   11篇
  2011年   16篇
  2010年   9篇
  2009年   14篇
  2008年   21篇
  2007年   20篇
  2006年   13篇
  2005年   17篇
  2004年   25篇
  2003年   17篇
  2002年   9篇
  2001年   13篇
  2000年   15篇
  1999年   14篇
  1998年   15篇
  1997年   7篇
  1996年   7篇
  1995年   11篇
  1994年   12篇
  1993年   6篇
  1992年   6篇
  1991年   4篇
  1990年   9篇
  1989年   3篇
  1988年   5篇
  1987年   4篇
  1986年   3篇
  1985年   9篇
  1984年   5篇
  1983年   7篇
  1982年   3篇
  1981年   10篇
  1978年   5篇
  1976年   2篇
  1972年   4篇
  1970年   1篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有543条查询结果,搜索用时 15 毫秒
151.
152.
Identification of 6-acetylmorphine, a specific metabolite of heroin, is considered to be definitive evidence of heroin use. Although 6-acetylmorphine has been identified in oral fluid following controlled heroin administration, no prevalence data is available for oral fluid specimens collected in the workplace. We evaluated the prevalence of positive test results for 6-acetylmorphine in 77,218 oral fluid specimens collected over a 10-month period (January-October 2001) from private workplace testing programs. Specimens were analyzed by Intercept immunoassay (cutoff concentration=30 ng/ml) and confirmed by GC-MS-MS (cutoff concentrations=30 ng/ml for morphine and codeine, and 3 ng/ml for 6-acetylmorphine). Only morphine-positive oral fluid specimens were tested by GC-MS-MS for 6-acetylmorphine. A total of 48 confirmed positive morphine results were identified. An additional 107 specimens were confirmed for codeine only. Of the 48 morphine-positive specimens, 32 (66.7%) specimens were positive for 6-acetylmorphine. Mean concentrations (+/-S.E.M.) of morphine, 6-acetylmorphine and codeine in the 32 specimens were 755+/-201, 416+/-168 and 196+/-36 ng/ml, respectively. Concentrations of 6-acetylmorphine in oral fluid ranged from 3 to 4095 ng/ml. The mean ratio (+/-S.E.M.) of 6-acetylmorphine/morphine was 0.33+/-0.06. It is suggested that, based on controlled dose studies of heroin administration, ratios >1 of 6-acetylmorphine/morphine in oral fluid are consistent with heroin use within the last hour before specimen collection. The confirmation of 6-acetylmorphine in 66.7% of morphine-positive oral fluid specimens indicates that oral fluid testing for opioids may offer advantages over urine in workplace drug testing programs and in testing drugged drivers for recent heroin use.  相似文献   
153.
154.
The detection of human remains that have been deliberately buried to escape detection is a problem for law enforcement. Sometimes the cadaver dog and handler teams are successful, while other times law enforcement and cadaver dog teams are frustrated in their search. Five field trials tested the ability of four cadaver dog and handler teams to detect buried human remains. Human and animal remains were buried in various forested areas during the summer months near Tuscaloosa, Alabama. The remains ranged in decomposition from fresh to skeletonized. Cadaver dogs detected with varying success: buried human remains at different stages of decomposition, buried human remains at different depths, and buried decomposed human and animal remains. The results from these trials showed that some cadaver dogs were able to locate skeletonized remains buried at a significant depth. Fresh and skeletonized remains were found equally by the cadaver dogs along with some caveats. Dog handlers affected the reliability of the cadaver dog results. Observations and videotape of the cadaver dogs during field trials showed that they were reliable in finding buried human remains.  相似文献   
155.
156.
157.
Dougherty  Keith L.  Cain  Michael J.G. 《Public Choice》1997,90(1-4):201-213
Between 1781 and 1789 the American states attempted to share the costs of national, public goods through a system of requisitions. This paper uses a simple public goods analysis to show why rational states would not share costs as intended by the Articles of Confederation. This normative argument illustrates a potential flaw in the constitutional design of the Articles and provides insight into the decline of the American Confederation.  相似文献   
158.
159.
160.
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