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   1933篇
  免费   57篇
各国政治   156篇
工人农民   61篇
世界政治   94篇
外交国际关系   68篇
法律   1308篇
中国政治   14篇
政治理论   274篇
综合类   15篇
  2021年   12篇
  2020年   37篇
  2019年   38篇
  2018年   50篇
  2017年   69篇
  2016年   62篇
  2015年   32篇
  2014年   44篇
  2013年   224篇
  2012年   45篇
  2011年   66篇
  2010年   47篇
  2009年   47篇
  2008年   54篇
  2007年   60篇
  2006年   51篇
  2005年   66篇
  2004年   54篇
  2003年   60篇
  2002年   45篇
  2001年   65篇
  2000年   50篇
  1999年   48篇
  1998年   17篇
  1997年   15篇
  1996年   21篇
  1995年   13篇
  1994年   14篇
  1993年   13篇
  1992年   30篇
  1991年   35篇
  1990年   38篇
  1989年   38篇
  1988年   35篇
  1987年   25篇
  1986年   35篇
  1985年   26篇
  1984年   21篇
  1983年   16篇
  1982年   15篇
  1981年   18篇
  1980年   12篇
  1979年   19篇
  1978年   21篇
  1977年   16篇
  1971年   21篇
  1970年   19篇
  1969年   11篇
  1968年   17篇
  1967年   12篇
排序方式: 共有1990条查询结果,搜索用时 0 毫秒
901.
902.
The three most recent decades provide an outstanding opportunity to study the changing federalist landscape concerning the regulation of speed on the nation's highways. Speed limits were the province of the states until the 1970s when, in an effort to save energy, the central government nationalized the maximum speed at 55 miles per hour. The national standard remained until the 1980s, when a partial devolution transferred some power to set speed limits back to the individual states. At that time, states could increase the maximum speed to 65 miles per hour on (at fewest) four‐lane, controlled access highways in low population density areas. Some states elected to loosen the limits within their borders, while others did not, citing concerns of highway safety as paramount. The 1990s saw the complete devolution of speed limit control to the states, when Congress returned to the states unlimited control. States reacted differently in both of the two latter phases, providing a fruitful landscape for comparative analysis of the effects of the devolution of speed limit control. The focus of this research is to examine which states raised the speed limits at the two stages of devolution, and what the subsequent effects were. I examine the issue of highway safety as a consequence of speed limit change, comparing states to elucidate differences to determine effects. Analysis of highway deaths per mile driven indicates that the nationalization of the 55 miles per hour contributed to an initial greater decline in the former than had been the trend, but the long‐term decreasing trend pattern reemerged following the shock of the change in federal speed limit policy. Additionally, the speed limit devolution and resulting raising of speed limits in certain states did not lead to a statistically significant rise in fatalities per miles driven. Automobile safety features and enforcement emerge as important factors in increasing highway safety; speed limits are far less important.  相似文献   
903.
We propose a political reinforcement hypothesis, suggesting that rising inequality moves party politics on welfare state issues to the right, strengthening rather than modifying the impact of inequality. We model policy platforms by incorporating ideology and opportunism of party members and interests and sympathies of voters. If welfare spending is a normal good within income classes, a majority of voters moves rightward when inequality increases. As a response, the left, in particular, shift their welfare policy platform toward less generosity. We find support for our arguments using data on the welfare policy platforms of political parties in 22 OECD countries.  相似文献   
904.
Discoloration of the skin of the anterior and lateral neck may raise suspicion for blunt force injury, particularly cervical compression, in an unwitnessed death. We present a case of an elderly woman with an unwitnessed death at home which highlights an external examination finding of blue/purple discoloration of the skin of the neck and links this finding with those from internal examination at autopsy. Pertinent negatives include absence of conjunctival and mucosal petechiae, absence of cutaneous abrasions of the neck, and absence of contusions of the anterior neck musculature. This case illustrates a natural disease entity, spontaneous dissection of a thoracic aortic hematoma, masquerading as blunt force injury externally and highlights the importance of having an appropriate index of suspicion when triaging jurisdictional cases for postmortem examination to accurately determine cause and manner of death.  相似文献   
905.
In this work, two methods were developed to determine herbicides paraquat, glyphosate, and aminomethylphosphonic acid (AMPA) in marijuana samples by capillary electrophoresis. For paraquat analysis, sample was extracted with aqueous acetic acid solution and analyzed by capillary zone electrophoresis with direct UV detection. The running electrolyte was 50 mmol/L phosphate buffer (pH 2.50). For glyphosate and AMPA, indirect UV/VIS detection was used, as these substances do not present chromophoric groups. Samples were extracted with 5 mmol/L hydrochloric acid. The running electrolyte was 10 mmol/L gallic acid, 6 mmol/L TRIS, and 0.1 mmol/L CTAB (pH = 4.7). The methods presented good linearity, precision, accuracy, and recovery. Paraquat was detected in 12 samples (n = 130), ranging from 0.01 to 25.1 mg/g. Three samples were positive for glyphosate (0.15–0.75 mg/g), and one sample presented AMPA as well. Experimental studies are suggested to evaluate the risks of these concentrations to marijuana user.  相似文献   
906.
Dextromethorphan (DXM) is abused most commonly among adolescents as a recreational drug to generate a dissociative experience. The objective of the study was to assess driving with and without DXM ingestion. The effects of one‐time maximum daily doses of DXM 120 mg versus a guaifenesin 400 mg dose were compared among 40 healthy subjects using a crossover design. Subjects’ ability to drive was assessed by their performance in a driving simulator (STISIM® Drive driving simulator software) and by conducting a standardized field sobriety test (SFST) administered 1‐h postdrug administration. The one‐time dose of DXM 120 mg did not demonstrate driving impairment on the STISIM® Drive driving simulator or increase SFST failures compared to guaifenesin 400 mg. Doses greater than the currently recommended maximum daily dose of 120 mg are necessary to perturb driving behavior.  相似文献   
907.
908.
Genetic Privacy   总被引:1,自引:0,他引:1  
  相似文献   
909.
Natur und Recht - Nach der Zustimmung des Bundestages zum öffentlich-rechtlichen Vertrag zur Beendigung der Braunkohleverstromung und dessen Unterzeichnung am 10.2.2021 steht der Ausstieg aus...  相似文献   
910.
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