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   12442篇
  免费   678篇
各国政治   558篇
工人农民   448篇
世界政治   1017篇
外交国际关系   408篇
法律   7991篇
中国共产党   1篇
中国政治   65篇
政治理论   2575篇
综合类   57篇
  2021年   79篇
  2020年   231篇
  2019年   285篇
  2018年   299篇
  2017年   374篇
  2016年   364篇
  2015年   295篇
  2014年   341篇
  2013年   1301篇
  2012年   305篇
  2011年   393篇
  2010年   340篇
  2009年   374篇
  2008年   348篇
  2007年   335篇
  2006年   349篇
  2005年   329篇
  2004年   319篇
  2003年   313篇
  2002年   309篇
  2001年   503篇
  2000年   459篇
  1999年   326篇
  1998年   218篇
  1997年   180篇
  1996年   149篇
  1995年   150篇
  1994年   173篇
  1993年   150篇
  1992年   214篇
  1991年   232篇
  1990年   224篇
  1989年   226篇
  1988年   227篇
  1987年   205篇
  1986年   239篇
  1985年   223篇
  1984年   174篇
  1983年   179篇
  1982年   118篇
  1981年   129篇
  1980年   95篇
  1979年   136篇
  1978年   79篇
  1977年   76篇
  1976年   76篇
  1974年   76篇
  1973年   70篇
  1972年   68篇
  1970年   49篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A new solid-phase extraction procedure for the determination of cocaine and benzoylecgonine in amniotic fluid, using high flow co-polymeric sorbents is reported. The recoveries of cocaine and benzoylecgonine within the range 0.1-1 mg/l were 95.7% and 50.3%, respectively. The use of high-flow sorbents allowed the easy extraction of amniotic fluid regardless of sample viscosity or physical nature. The use of these solid-phase columns provided many advantages over the more commonly used solvent extraction, including an increase in extraction speed and efficiency, reduced operator time, reduced solvent use and disposal volumes and exceptional extract quality. Further, the determination of amniotic fluid obtained from pregnant cocaine users may provide important information about handling of cocaine by the fetus at various gestational ages. The procedure was successfully applied to amniotic fluid from suspected cocaine abusers.  相似文献   
52.
The polymerase chain reaction (PCR) method of specific gene amplification was used in casework to synthesize millions of copies of the polymorphic second exon of the human leukocyte antigen (HLA)-DQ alpha (or DQA1) locus from a variety of evidence samples. The HLA-DQ alpha allelic variants in the amplified deoxyribonucleic acid (DNA) were determined in a rapid non-radioactive test by hybridization to sequence-specific oligonucleotide probes in both the dot-blot and reverse dot-blot formats. This genetic typing system has been subjected to blind proficiency testing; the performance of this test in the analysis of experimentally mixed samples was also evaluated. As of August 1990, over 250 cases have been tested and more than 2000 individual evidence (bloodstains, semen stains, individual hairs, bone fragments, and tissue sections) and reference samples have been analyzed. The first 198 of these cases are summarized in this paper; in 65% of the cases with conclusive results a suspect was included, and in 35%, all suspects were excluded. Individual cases as well as some of the general issues relating to forensic science analysis and this genetic typing system are discussed. The high rate of exclusion reported here combined with the ability of PCR to type old evidence samples suggests the relevance of this genetic test for postconviction review; two cases in which the convicted suspect was excluded are discussed.  相似文献   
53.
Postmortem changes in sulfide concentrations in body tissues were examined in autopsied rats exposed to hydrogen sulfide concentrations of 550 to 650 ppm, and in nonexposed rats and humans. Analyses were made by gas chromatography, following an extractive alkylation. Sulfide concentrations in the blood, liver, and kidneys of rats increased in both the exposed and nonexposed groups, depending on the lapse of time after death. On the other hand, the lung, brain, and muscle showed little or no change in sulfide concentration with elapse of time after death. The data obtained from human tissues were almost the same as those for rats, except data for blood, in which no or little increase of sulfide was observed.  相似文献   
54.
A 22-year-old Korean soldier, who had received blows to the neck and epigastrium from an officer 10 h earlier, suddenly died after massive hematemesis. He had been in relatively good health except for episodes of blood-tinged vomiting approximately 5 and 7 months prior to this event. Postmortem examination revealed angiodysplasia involving the gastroesophageal junction, and the stomach was distended with blood. No abnormal findings were present around the whole viscera, and the duodenum was free of blood. The pathologic significance of upper gastrointestinal angiodysplasia as a potential source of bleeding and a chronologic correlation between the trauma and bleeding are discussed.  相似文献   
55.
56.
While the beneficial aspects of a public accounting office's activity are not disputed here, it is argued in this article that four major distortions are produced: the concern with administrative rationality overlooks costs elsewhere (Section 2); budgetary aspects are overvalued compared to other issues (Section 3); incentives-oriented behavior is suppressed (Section 4); and the evaluation is biased by concentrating on minor, instead of major, aspects of inefficiency (Section 5). Section 6 considers alternatives to public accounting offices and makes some suggestions for new institutional arrangements particularly for constitutional rules.  相似文献   
57.
The primary aim of this paper is to review the literature on preadolescent friendships in order to examine the relationship between preadolescent friendships and social support in adulthood. Social supports are important to health, both directly and as a stress buffer. Few studies, however, have specifically examined adult social supports from the perspective of their developmental precursors and critical developmental periods. Some data indicate that the preadolescent period may be of particular importance to the development of adult social skills and ties. Observational and empirical studies of preadolescent peer relationships, and in particular best friendships, suggest unique and critical contributions to adult social relatedness. Present research is suggestive but is insufficient to validate preadolescence as a critical period in adult social relatedness. Our review has implications for better understanding the mechanisms by which preadolescent friendships effect adult social support—an important mediator of the effects of stress on health. Further longitudinal study is needed.Received Ph.D. from University of Maryland. Research interests are social supports and psychological responses to trauma and disaster.Received M.D. from Yale University. Research interests are social supports and traumatic stress.  相似文献   
58.
Presented in this paper are the initial results involving the use of the nose or outer ear as temperature measurement sites to determine the postmortem period of the human corpse. Simple mathematical models for both sites are developed based on cooling curves of five corpses. Analysis of errors between actual and calculated postmortem intervals suggest that in its present form, the described methods would not be suitable for use in accurately determining the time since death of human corpses.  相似文献   
59.
60.
Rethinking the Meaning of Public Health   总被引:1,自引:0,他引:1  
  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