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   21113篇
  免费   646篇
各国政治   924篇
工人农民   832篇
世界政治   1728篇
外交国际关系   698篇
法律   12661篇
中国共产党   3篇
中国政治   104篇
政治理论   4605篇
综合类   204篇
  2020年   261篇
  2019年   308篇
  2018年   404篇
  2017年   479篇
  2016年   504篇
  2015年   371篇
  2014年   410篇
  2013年   2124篇
  2012年   518篇
  2011年   528篇
  2010年   433篇
  2009年   469篇
  2008年   553篇
  2007年   575篇
  2006年   554篇
  2005年   494篇
  2004年   500篇
  2003年   516篇
  2002年   478篇
  2001年   795篇
  2000年   741篇
  1999年   604篇
  1998年   344篇
  1997年   291篇
  1996年   244篇
  1995年   253篇
  1994年   287篇
  1993年   262篇
  1992年   415篇
  1991年   436篇
  1990年   412篇
  1989年   417篇
  1988年   389篇
  1987年   405篇
  1986年   418篇
  1985年   425篇
  1984年   354篇
  1983年   387篇
  1982年   305篇
  1981年   278篇
  1980年   220篇
  1979年   291篇
  1978年   209篇
  1977年   173篇
  1976年   162篇
  1975年   158篇
  1974年   190篇
  1973年   168篇
  1972年   145篇
  1970年   122篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
A 6-month-old girl died suddenly without any previous symptoms of heart failure. Autopsy examination showed cardiomegaly (97 g) with a severely fibrotized myocardium. The left coronary artery was originating from the pulmonary artery. Histologically, the myocardium showed myocardial infarcts of different ages, as well as grossly thickened arterial branches due to increased flow in left-right shunt. We suggest that rare anomalies of the coronary arteries should be considered in the autopsies of suspected sudden infant death syndrome cases.  相似文献   
143.
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   
144.
Washington University v. Catalona revolves around ownership of tissue samples provided by patients for research purposes, raising significant ethical and legal questions concerning patient rights, current human research practices, and the treatment of samples as capital resources by the research institution.  相似文献   
145.
In this study, a new method was developed for the impurity profiling of illicit MDMA tablets. The extraction efficiency, linearity, repeatability and reproducibility of the method were evaluated. Eighty two MDMA tablets coming from presumed unrelated large seizures in 2004 (n >500 tablets) were analyzed by gas chromatography mass spectrometry (GC-MS) in order to assess the discrimination power of the method. The latter was found to be practical, robust, relatively easy to perform, highly discriminative and yielding good chromatography. In addition, some new impurities were detected and identified. Their chemical structures and mass spectra are reported.  相似文献   
146.
147.
In a case of suicidal application of electricity differences between the rectal temperature of the body and the suspected time of death were observed.In order to answer the question whether an electric current from hand to hand over >30 min led to a rise in body temperature FEM-based computer simulations and animal experiments were carried out. Both resulted in a warming of the soft parts in the arm without warming the body core. Thus a temperature-based estimation of the time since death can also be used in cases with electricity as the cause of death. Besides, in the animal experiment we found a spontaneous rise in the body core temperature even without application of electricity which may be a reason for the typical temperature plateau after death.  相似文献   
148.
149.
150.
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