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   20144篇
  免费   1260篇
各国政治   861篇
工人农民   912篇
世界政治   1342篇
外交国际关系   624篇
法律   14105篇
中国共产党   2篇
中国政治   144篇
政治理论   3302篇
综合类   112篇
  2021年   100篇
  2020年   468篇
  2019年   489篇
  2018年   604篇
  2017年   627篇
  2016年   726篇
  2015年   541篇
  2014年   585篇
  2013年   2017篇
  2012年   550篇
  2011年   583篇
  2010年   572篇
  2009年   603篇
  2008年   580篇
  2007年   563篇
  2006年   586篇
  2005年   505篇
  2004年   524篇
  2003年   440篇
  2002年   484篇
  2001年   829篇
  2000年   738篇
  1999年   581篇
  1998年   280篇
  1997年   193篇
  1996年   206篇
  1995年   212篇
  1994年   192篇
  1993年   197篇
  1992年   361篇
  1991年   366篇
  1990年   368篇
  1989年   350篇
  1988年   381篇
  1987年   325篇
  1986年   377篇
  1985年   366篇
  1984年   275篇
  1983年   263篇
  1982年   198篇
  1981年   188篇
  1980年   156篇
  1979年   245篇
  1978年   136篇
  1977年   114篇
  1976年   93篇
  1975年   121篇
  1974年   150篇
  1973年   105篇
  1972年   109篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
A case of the sudden death of a 14-month-old girl due to massive hemorrhage in a primitive neuroectodermal tumor (PNET) is presented along with a review of the relevant literature. PNET is a rare, malignant brain neoplasm occurring predominantly in children.  相似文献   
82.
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   
83.
84.
An improved method has been developed for the reliable classification of different C1R genetic variant forms from human serum or plasma. The method combines the use of neuraminidase-digested samples followed by monodimensional isoelectric focusing in the pH range 5 to 8 followed by immunoblotting. The method yields a simple pattern, with one major band in homozygote and two major bands in heterozygote cases.  相似文献   
85.
Dilutions of 100 serum samples of various GM phenotypes were dotted onto a nitrocellulose membrane. The serum dot-blots were detected with peroxidase-labeled anti-G3M T monoclonal antibody (anti-G3M T MAb). Up to a 1 : 256 dilution could be G3M T-typed correctly. By use of anti-G3M T MAb and peroxidase-labeled anti-mouse IgG or the biotin-avidin system instead of use of labeled anti-G3M T MAb, up to a 1 : 512 or 1 : 1024, respectively, dilution was typable. As with previous work with G3M G MAb, the dot immunobinding (DIB) method for G3M T typing was found very simple and practical.  相似文献   
86.
A technique was developed for Gm/Km typing of bloodstains and sera in U-bottom microtiter plates. Gm/Km typing of sweat and urine samples was also attempted with limited success.  相似文献   
87.
88.
HIV infection is now perceived as the end stage of a chronic disease that is spreading most rapidly among blacks and Hispanics. The politics of the HIV epidemic in the 1980s were dominated by four interacting factors: fear and fascination; who had the disease and to whom it seemed to be spreading; the endemic problems of United States social policy; and the impact on policy of advances in scientific knowledge. This paper analyzes the political history of each of these factors and describes the dominant policies of the federal government and the states regarding HIV in the areas of surveillance, prevention, research, and financing. Four uncertainties will have a profound influence on the future politics of the HIV epidemic: how the states and the federal government will address the general problems of paying for the care of people with chronic diseases and providing access to care for the uninsured and the underinsured; the number and distribution of the sexual behaviors that transmit infection with HIV and the effectiveness of policies to persuade people to modify these behaviors; precisely who uses addictive drugs and the effectiveness of measures to change their behavior; and the natural history of the virus.  相似文献   
89.
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   
90.
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