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   16965篇
  免费   454篇
各国政治   807篇
工人农民   661篇
世界政治   1116篇
外交国际关系   543篇
法律   10540篇
中国政治   103篇
政治理论   3513篇
综合类   136篇
  2020年   170篇
  2019年   233篇
  2018年   297篇
  2017年   347篇
  2016年   351篇
  2015年   261篇
  2014年   308篇
  2013年   1651篇
  2012年   349篇
  2011年   404篇
  2010年   345篇
  2009年   391篇
  2008年   419篇
  2007年   439篇
  2006年   432篇
  2005年   384篇
  2004年   363篇
  2003年   393篇
  2002年   358篇
  2001年   657篇
  2000年   567篇
  1999年   483篇
  1998年   247篇
  1997年   198篇
  1996年   200篇
  1995年   192篇
  1994年   202篇
  1993年   197篇
  1992年   334篇
  1991年   382篇
  1990年   367篇
  1989年   372篇
  1988年   360篇
  1987年   366篇
  1986年   402篇
  1985年   387篇
  1984年   345篇
  1983年   321篇
  1982年   219篇
  1981年   211篇
  1980年   176篇
  1979年   262篇
  1978年   169篇
  1977年   174篇
  1976年   146篇
  1975年   145篇
  1974年   170篇
  1973年   159篇
  1972年   128篇
  1971年   116篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.
Deoxyribonucleic acid (DNA) typing of ribosomal ribonucleic acid (rRNA) genes was performed with a polymerase chain reaction (PCR) assay for species identification. A variable region of the 28S ribosomal RNA gene was amplified with primers complementary to flanking sequences phylogenetically well conserved. The products of twelve animal DNAs (human, Japanese monkey, dog, cattle, pig, cat, rabbit, mouse, rat, chicken, frog, and fish) were separated by polyacrylamide gel electrophoresis, each revealing a few bands ranging from 150 to 100 base pairs. The band patterns obtained from each DNA sample differed in number and size, which indicates the applicability of the method to species identification. Samples containing either as little as 1 pg of DNA or degraded DNA of 0.2 to 0.5 kb in length were able to give detectable bands. Postmortem human tissue DNAs were tested as an example. They showed a pattern identical to the human control one, which was distinct from those of the other animals examined.  相似文献   
114.
Policy analysis for the Congress is a timely subject. Several policy initiatives have emerged recently from the “first branch.” Others have demonstrated an independent capacity for analysis that is impressive by historical standards. This article introduces a practitioner symposium of three related works on policy analysis for Congress, with appropriate commentary by a distinguished veteran. It argues that because timing is crucial in the congressional policy process, anticipation and advance preparation are central to the effective use of analysis. The other articles illustrate the stages of advance preparation—of the policy analyst, the congressional environment, and the Member for voting—in the form of case studies.  相似文献   
115.
The authors examine the characteristics of threatening and otherwise inappropriate communications sent to members of the U.S. Congress by a sample of 86 subjects, 20 of whom threatened assassination. We quote excerpts from these letters and provide quantitative data on such variables as the volume, duration, form, and appearance of such communications; the enclosures; the subjects' perceived relationships to the recipients; the thematic content of the communications; and the messages and threats communicated. Comparisons between 43 subjects who pursued encounters with members of Congress and 43 who did not revealed 17 factors associated with such pursuit. In this population, threateners were significantly less likely to pursue an encounter than inappropriate letter writers who did not threaten, regardless of the type of threat or the harm threatened. Inappropriate letters to members of Congress are compared with those directed to Hollywood celebrities. Mentally disordered persons writing to public figures often mention and sometimes threaten public figures other than those to whom the letters are addressed, which raises important issues regarding notification of endangered third parties and the sharing of information among protective agencies.  相似文献   
116.
Bioaerosol data is often used in cases of building mold infestation alleging damage or adverse health effects upon occupants, despite the lack of consistent sampling and analytical protocols and numerical health-based standards. The most fundamental problem in these scenarios is defining a “significant” difference between a suspect indoor environment and the reference environment, regardless of the type of sampling and analysis utilized. Data interpretation focused upon differences in absolute numerical concentrations of fungi is subject to wide differences in expert opinion. On the other hand, an objective quantification of differences can be expressed in terms of probability and better meets criteria established in evidentiary rules.  相似文献   
117.
Der Begriff der Landeskultur umfasst alle Maßnahmen zur Verbesserung der land- und forstwirtschaftlichen Nutzung des Bodens einschließlich der Erhaltung der Kulturlandschaft. Landeskultur ist somit alles Planen und Handeln mit dem Ziel, die Umwelt als gegebenes Naturraumpotential, insbesondere Wasser, Boden, Luft und die dazugehörigen Natur-, Kultur- und Sachgüter optimal zu erhalten, gestalten und rationell zu nutzen sowie dieses Potential mit bestmöglicher Qualität als natürliche und kulturelle Lebensgrundlage für die Allgemeinheit nachhaltig zu sichern. Landeskultur dient somit auch der Belebung und Werterhöhung der gebauten und gepflanzten Umwelt. Dies schließt auch und gerade die kulturelle Seite einschließlich Kulturlandschaften mit ein. Dabei ist es bis zur Überprüfung durch das BVerfG noch hinnehmbar, dass der Begriff „Landeskultur“ in Art. 89 Abs. 3 GG wegen der Mischkompetenz von Bund und Land vom BVerwG enger ausgelegt wird als in anderen Rechtsvorschriften.  相似文献   
118.
Toxicologic findings in the USS Iowa disaster.   总被引:5,自引:0,他引:5  
The toxicologic results from the 47 victims of the explosion on the USS Iowa are presented. Good correlation between carboxyhemoglobin saturations and cause of death was found. There were no correlations between blood cyanide concentrations and causes of death. Volatile analysis suggested postmortem ethanol production rather than antemortem ethanol ingestion. No drugs except nicotine were detected in any of the victims.  相似文献   
119.
120.
The impact of high temperatures (24 to 39 degrees C) and low to moderately high humidities (20 to 70%) on the applicability of TLC systems for drug identification was studied during a 6 month climatologic cycle in Burkina Faso (West Africa). In general, the Rf values as observed on the plates were found to be substantially affected as compared with values obtained at temperate climates. Some TLC systems were more affected than others and the largest deviations of up to 30 Rf units were at low humidities. Tropical conditions also had a negative effect on the reproducibility of Rf values. However, when an Rf-correction procedure was applied, using reference mixtures of known drugs on each plate, accuracy as well as reproducibility of the resulting Rfc values were drastically improved and data thus corrected were found to be compatible with existing TLC data bases developed under moderate climatological conditions. The impact of high to extremely high humidities (70 to 100%) remains to be investigated.  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