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   9220篇
  免费   266篇
各国政治   588篇
工人农民   329篇
世界政治   670篇
外交国际关系   401篇
法律   5604篇
中国共产党   1篇
中国政治   90篇
政治理论   1706篇
综合类   97篇
  2021年   72篇
  2020年   126篇
  2019年   165篇
  2018年   229篇
  2017年   288篇
  2016年   256篇
  2015年   195篇
  2014年   228篇
  2013年   1030篇
  2012年   312篇
  2011年   302篇
  2010年   206篇
  2009年   202篇
  2008年   281篇
  2007年   237篇
  2006年   255篇
  2005年   207篇
  2004年   230篇
  2003年   210篇
  2002年   217篇
  2001年   345篇
  2000年   300篇
  1999年   240篇
  1998年   88篇
  1997年   118篇
  1996年   84篇
  1995年   83篇
  1994年   99篇
  1993年   85篇
  1992年   160篇
  1991年   184篇
  1990年   162篇
  1989年   178篇
  1988年   154篇
  1987年   147篇
  1986年   165篇
  1985年   129篇
  1984年   127篇
  1983年   135篇
  1982年   77篇
  1981年   75篇
  1980年   58篇
  1979年   114篇
  1978年   66篇
  1977年   62篇
  1975年   67篇
  1974年   83篇
  1973年   78篇
  1972年   69篇
  1971年   66篇
排序方式: 共有9486条查询结果,搜索用时 15 毫秒
51.
52.
In this article a practical case is described when gunshot directions and position of a victim's body at the moment of each shot were determined by natural simulation using an LG-78 laser (made in the form of a gun).  相似文献   
53.
This study used data from 299 police officers from 12 municipal police departments across the state of Virginia to determine the relationship between education and police performance. Performance was measured by supervisor evaluations of each officer's overall performance, communication skills, public relations skills, report writing skills, response to new training, decision making ability, and commitment to the police department. Significant correlations were found between education and most measures of performance. Most importantly, the results show a significant correlation between overall performance and education (r=24, p.<001). The only variables not proving to be significantly related to education were objective measures of the volume of arrests, number of times the officer required discipline, and number of accidents. Interestingly, the benefits of a college education do not become apparent until police officers gain experience. In addition, police, officers with only a high school diploma decreased in overall performance after five years of experience.  相似文献   
54.
55.
An analytical method using solid-phase extraction (SPE) and high-performance liquid chromatography–mass spectrometry (LC–MS) has been developed and validated for the confirmation of Δ9-tetrahydrocannabinol (THC) in oral fluid samples. Oral fluid was extracted using Bond Elut LRC-Certify solid-phase extraction columns (10 cm3, 300 mg) and elution performed with n-hexane/ethyl acetate. Quantitation made use of the selected ion-recording mode (SIR) using the most abundant characteristic ion [THC + H+], m/z 315.31 and the fragment ion, m/z 193.13 for confirmation, and m/z 318.00 for the protonated internal standard, [d3-THC + H+]. The method proved to be precise for THC, in terms of both intra-day and inter-day analyses, with coefficients of variation less than 10%, and the calculated extraction efficiencies for THC ranged from 76 to 83%. Calibration standards spiked with THC between 2 and 100 ng/mL showed a linear relationship (r2 = 0.999). The method presented was applied to the oral fluid samples taken from the volunteers during the largest music event in Portugal, named Rock in Rio-Lisboa. Oral fluid was collected from 40 persons by expectoration and with Salivette®. In 55% of the samples obtained by expectorating, THC was detected with concentration ranges from 1033 to 6552 ng/mL and in 45% of cases THC was detected at concentrations between 51 and 937 ng/mL. However, using Salivette® collection, 26 of the 40 cases had an undetectable THC.  相似文献   
56.
57.
58.
The functional and nutritive circulation in the lungs is connected by anastomoses between the pulmonary and bronchial arteries. The anastomoses have the structure of blocked arteries from which arteriovenous anastomoses proceed to the peribronchial plexus. The pulmonary artery is provided with a flow impulse by the anastomoses, and oxygen-containing blood is admixed with the venous blood, thus forming an "aortalization" in the lungs. By diverting the bloodstream, venous blood can reach the bronchial artery. The peculiarities of the lung circulation are important for vital reactions in the form of macro- and microembolisms. Macroembolisms prove the functionality of the system if branches of the pulmonary artery are closed before the arteries are blocked. A hemorrhagic infarction either arises or does not arise, and the hemorrhagic infarction cannot exceed a certain limit. A microembolism is over and above the anastomoses. If the microembolism is greater, pressure in the arteria pulmonaris can cause blood from the pulmonary artery to overflow into the bronchial artery. Because arteriovenous anastomoses arise from the blocked arteries, microemboli can now reach the systemic circulation. Thus, the system described can explain the passage of microemboli into the systemic circulation, avoiding the capillaries of the lungs; on the other hand, larger microembolisms can prove the functionality of the system.  相似文献   
59.
Easterbrook G  Barry J  Thomas R  Clift E  Wingert  Hager M  Cohn B 《Newsweek》1992,120(22):30, 32-34, 36
Lobbyists, entrenched forces in congress and self-interested friends will try to stymie Clinton's efforts. A look at four key arenas of combat.  相似文献   
60.
The author incorporates geographic variables into this study of population dynamics in Michoacan, Mexico, during the eighteenth century.  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