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   391篇
  免费   7篇
各国政治   33篇
工人农民   39篇
世界政治   29篇
外交国际关系   23篇
法律   180篇
中国政治   8篇
政治理论   84篇
综合类   2篇
  2023年   3篇
  2021年   6篇
  2020年   4篇
  2019年   16篇
  2018年   13篇
  2017年   23篇
  2016年   15篇
  2015年   7篇
  2014年   14篇
  2013年   81篇
  2012年   13篇
  2011年   11篇
  2010年   12篇
  2009年   9篇
  2008年   9篇
  2007年   5篇
  2006年   13篇
  2005年   13篇
  2004年   10篇
  2003年   12篇
  2002年   11篇
  2001年   6篇
  2000年   6篇
  1999年   5篇
  1998年   5篇
  1997年   3篇
  1996年   6篇
  1995年   5篇
  1994年   3篇
  1993年   4篇
  1992年   4篇
  1991年   7篇
  1990年   7篇
  1989年   5篇
  1988年   4篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   4篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1973年   3篇
  1966年   2篇
排序方式: 共有398条查询结果,搜索用时 15 毫秒
211.
212.
213.
214.
215.
216.
217.
The detection and identification of traces of inorganic ions and sugars can play a major role in the forensic investigation of an explosives related incident. This survey investigated the background levels of these substances in the general environment. Six sampling locations were selected from around the mainland of the United Kingdom, representing urban and rural sites. Swab and vacuum samples were collected from different locations within each site including motor vehicles, private houses, hotels, the exterior of buildings, road surfaces, and street signs. Sampling was carried out in summer and winter to investigate changes in the levels of the target species due to seasonal factors such as road treatments or weather. The samples were extracted with water and analyzed for a range of inorganic anions, cations, and sugars using ion chromatography. Most of the target anions were found to be common to all locations. Chloride, sulphate, nitrate, and phosphate were found to be the most common and the most abundant. Chlorate was found at a low level in some external samples. Perchlorate and thiocyanate were not detected in any samples. There was a marked increase in the quantity of sodium and chloride detected in samples collected during the winter. Sodium and calcium were detected in most samples. Potassium and magnesium were detected in approximately half of the samples. Ammonium was less common but detected at significant levels in wall samples. Glucose, fructose, and sucrose were detected in the vacuum samples from the interior surfaces of houses, hotels, and cars.  相似文献   
218.

North Carolina offers its residents the opportunity to cast early in-person (EIP) ballots prior to Election Day, a practice known locally as “One-Stop” voting. Following a successful legal challenge to the state’s controversial 2013 Voter Information and Verification Act, North Carolina’s 100 counties were given wide discretion over the hours and locations of EIP voting for the 2016 General Election. This discretion yielded a patchwork of election practices across the state, providing us with a set of natural experiments to study the effect of changes in early voting hours on voter turnout. Drawing on individual-level voting records from the North Carolina State Board of Elections, our research design matches voters on race, party, and geography. We find little evidence that changes to early opportunities in North Carolina had uniform effects on voter turnout. Nonetheless, we do identify areas in the presidential battleground state where voters appear to have reacted to local changes in early voting availability, albeit not always in directions consistent with the existing literature. We suspect that effects of changes to early voting rules are conditional on local conditions, and future research on the effects of election law changes on turnout should explore these conditions in detail.

  相似文献   
219.
This paper highlights important lessons gained from the research program of Elinor Ostrom, and demonstrates the close connection between public choice and the work on collective management of the commons for which Lin was honored by the Nobel Prize committee. Although our primary focus is on Lin’s research on self-governance and the “commons,” an overarching goal is to capture the intellectual journey of participants in the Ostrom Workshop, who continue to be guided by the inspiring examples set by Lin and Vincent Ostrom.  相似文献   
220.
With its extraction and assay setup modules, the QIAsymphony® provides a highly flexible solution for processing forensic samples in a medium- to high-throughput scale. We tested the sensitivity of extraction, precision of sample processing, and accuracy of automated assay setup of this integrated system. Results attest to QIAsymphony's ability to isolate DNA from a spectrum of common forensic samples and process these samples without cross-contamination. Furthermore, accurate assay setup for downstream applications, like PCR, make this system highly suited for enhancing laboratory workflow.  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