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   4978篇
  免费   218篇
各国政治   289篇
工人农民   126篇
世界政治   503篇
外交国际关系   314篇
法律   2193篇
中国政治   27篇
政治理论   1684篇
综合类   60篇
  2021年   26篇
  2020年   54篇
  2019年   62篇
  2018年   108篇
  2017年   135篇
  2016年   170篇
  2015年   107篇
  2014年   92篇
  2013年   768篇
  2012年   137篇
  2011年   125篇
  2010年   131篇
  2009年   147篇
  2008年   142篇
  2007年   157篇
  2006年   167篇
  2005年   162篇
  2004年   153篇
  2003年   154篇
  2002年   145篇
  2001年   85篇
  2000年   103篇
  1999年   92篇
  1998年   108篇
  1997年   91篇
  1996年   57篇
  1995年   85篇
  1994年   77篇
  1993年   80篇
  1992年   82篇
  1991年   65篇
  1990年   59篇
  1989年   74篇
  1988年   74篇
  1987年   85篇
  1986年   77篇
  1985年   80篇
  1984年   68篇
  1983年   59篇
  1982年   61篇
  1981年   60篇
  1980年   43篇
  1979年   48篇
  1978年   42篇
  1977年   39篇
  1976年   28篇
  1975年   28篇
  1974年   27篇
  1973年   26篇
  1969年   23篇
排序方式: 共有5196条查询结果,搜索用时 15 毫秒
281.
The concentrations of ten elements in 209 unrelated glass specimens received as evidence were used to assess the frequencies of errors of false association (Type II errors) using several comparison criteria at specified significance levels (Type I errors). Pairwise comparisons of the samples using either the equal-variance t-test or Welch's modification (unequal variances) result in a small number of errors of false association, even when adjusting the significance level (Bonferroni correction) for multivariate comparisons. At the 95% confidence level (overall Type I error of 0.05, or individual element comparison error of 0.005), only two Type II errors are made in 21736 comparisons (0.009%) when using the equal-variance t-test for comparison of sample means. In this study, the range overlap test using three replicate measurements per specimen results in no errors of false association. Most specimen pairs in this data set are readily discriminated either by differences in the concentrations of several elements or by an extremely large difference in the concentrations of one or more element.  相似文献   
282.
Ketosis occurs in ketoacidosis or malnourishment. When either is suspected in relation to a death, it may be important to analyze for ketosis at autopsy. We encountered a case where starvation was suspected in a deceased nursing home resident, where the body had been embalmed prior to autopsy. Gas chromatography (GC) was unable to separate acetone from formaldehyde, a component of embalming fluid. The Acetest is a simple test that can detect acetone and acetoacetate in body fluids. We validated the Acetest with GC on vitreous. The Acetest and GC were consistent except at very low levels of acetone or acetoacetate. The sensitivity of the Acetest for acetoacetate in vitreous was 10 mg/dL, consistent with early starvation. Significant interference from embalming fluid did not occur. The Acetest was negative in the described case. The Acetest is a simple and useful test for the detection of ketosis in embalmed autopsies.  相似文献   
283.
Six ninhydrin analogues containing oxygen, sulfur, and selenium substituents at the C-5 position, 5-(4-nitrophenyl)ninhydrin, and benzo[f]furoninhydrin were evaluated as fingerprint development reagents. The analogues all showed good fingerprint color development but were not superior to ninhydrin in this respect. The benzo[f]furoninhydrin complex was strongly luminescent at room temperature following zinc complexation, while the remaining analogues required cooling to -196 degrees C to produce optimum luminescence. The benzo[f]furo, nitrophenyl, and methyl selenide analogues showed the best potential as fingerprint reagents with the benzo[f]furo analogue comparing favorably with DFO.  相似文献   
284.
285.
286.
287.
288.
289.
China's rapidly growing motor vehicle fleet is changing the makeup of its urban atmosphere. While the two major problem pollutants historically have been particulates and sulfur dioxide, the growth in the number of automobiles has generated substantially increased levels of nitrogen dioxide (NO2). This paper examines and values the mortality health effects (reduced premature deaths) from cleaning up these three pollutants. Findings indicate that valued gains from reduced air pollution mortality can average 3% of a city's GDP. Moreover, the growing auto fleet may generate a ten-fold increase in NO2-based mortality costs and offset other, ongoing cleanup efforts in many Chinese cities. Specifically, the paper explores how the increasing number of automobiles might diminish or offset environmental cleanup activities focused upon particulate and sulfur dioxide pollution.  相似文献   
290.
Robert S. Ross 《当代中国》2006,15(48):443-458
Taiwan is a revisionist power. Its independence movement challenges a vital status-quo interest of mainland China's opposition to a de jure Taiwan declaration of independence and maintaining, however ambiguously, Taiwan's commitment to the ‘one-China’ formulation. Why is it that a small and vulnerable island off the coast of a great power has continued to challenge the vital interest of that great power and risk war? Adopting a ‘levels of analysis’ approach to Taiwan's mainland policy, this paper addresses this question by examining four prevalent explanations for Taiwan's revisionist diplomacy: (1) the mainland deterrent is ineffective, reflecting Taiwan doubts about either mainland capabilities or mainland resolve to wage a retaliatory war; (2) in an example of the security dilemma in alliance politics, US commitment to Taiwan, although aimed at deterring PRC use of force, encourages Taiwan to challenge the status quo because the Taiwan leadership is confident of US intervention and US ability to defend Taiwan; (3) because of the development of a ‘Taiwan identity’ and of corresponding domestic political pressures, the Democratic Progressive Party has been compelled to adopt a pro-independence policy; (4) Chen Shui-bian has a personal commitment to Taiwan independence and has been willing to challenge the mainland's interest in one-China, despite risk of heightened conflict and regardless of domestic political considerations.  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