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   16932篇
  免费   565篇
  国内免费   5篇
各国政治   687篇
工人农民   760篇
世界政治   1179篇
外交国际关系   580篇
法律   10835篇
中国共产党   6篇
中国政治   156篇
政治理论   3125篇
综合类   174篇
  2020年   233篇
  2019年   293篇
  2018年   361篇
  2017年   423篇
  2016年   424篇
  2015年   311篇
  2014年   315篇
  2013年   1592篇
  2012年   464篇
  2011年   499篇
  2010年   402篇
  2009年   422篇
  2008年   515篇
  2007年   555篇
  2006年   539篇
  2005年   485篇
  2004年   465篇
  2003年   504篇
  2002年   439篇
  2001年   677篇
  2000年   551篇
  1999年   484篇
  1998年   258篇
  1997年   178篇
  1996年   206篇
  1995年   178篇
  1994年   202篇
  1993年   203篇
  1992年   330篇
  1991年   356篇
  1990年   342篇
  1989年   285篇
  1988年   321篇
  1987年   274篇
  1986年   321篇
  1985年   284篇
  1984年   233篇
  1983年   221篇
  1982年   187篇
  1981年   195篇
  1980年   131篇
  1979年   174篇
  1978年   127篇
  1977年   110篇
  1976年   100篇
  1975年   123篇
  1974年   133篇
  1973年   104篇
  1972年   101篇
  1969年   98篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
A total of 36 ancient human remains from 12 individuals (three tooth/bone samples each) and one sample each of three individuals from the newest time was typed in a blind study using the amelogenin sex test. Prior to this molecular sex determination the sex of the individual was determined morphologically. The success rate of the amelogenin amplifications was >90%. For every individual an unambiguous molecular sex typing result was obtained. Furthermore, the morphological and molecular sex determinations were in accordance with each other, giving evidence for the authenticity and ancient origin of the polymerase chain reaction (PCR) amplifications.  相似文献   
982.
A number of DNA polymorphisms have been found to be associated with the pathophysiology of some common disease. If the LDLR polymorphism is directly or indirectly related to some fatal disease, the distribution of the polymorphism may vary with age. We therefore investigated the aging-associated distribution of the LDLR polymorphism. Blood samples were collected from Japanese cadavers (aged 0-91) at autopsy. The LDLR polymorphism was detected using a AmpliType PM PCR Typing kit. When the LDLR genotype was examined in cadavers divided according to age into 0-29 year group, 30-59 year group, and 60-91 year group, there were significant differences in genotype among the three age groups and between the 0-29 year group and 60-91 year group. The LDLR-A genotype tended to be lower in the older cadavers. The present study revealed that there were aging-dependent differences in the distribution of the LDLR polymorphism in autopsy samples, suggesting that a common mutation involved in the occurrence of fatal diseases may be present near the LDLR-A polymorphism locus.  相似文献   
983.
Papillary fibroelastoma is a rare benign tumor, occasionally causing angina or sudden death. We report an autopsy case of an aortic valve papillary fibroelastoma with coronary artery embolism. The patient was a 68-year-old Japanese man who had collapsed suddenly in his house. He was a heavy drinker and had a history of liver disease but no notable cardiac event. The autopsy revealed extensive transmural infarction of the inferior wall of the left and right cardiac ventricles. The distal portion of the right coronary artery (segment 4, NYHA) was completely occluded by tumor emboli of the fibroelastoma. At the site of closure of the aortic non-coronary cusp, there was a typical papillary fibroelastoma, which was considered to have originated the coronary embolization.  相似文献   
984.
985.
The binding of charged substances from external aqueous media to hair has been investigated through the use of fluorescence microscopy. Eleven hair samples, reflecting various ethnic groups and cosmetic treatments, were tested. Rhodamine 6G, a cationic dye representative of drugs such as cocaine and opiates, showed incorporation throughout the hair of all samples except one. In contrast, fluorescein, an anionic dye representative of drugs such as THC carboxylic acid, was not readily incorporated. The incorporation of rhodamine 6G was faster for chemically 'straightened' and bleached African-American female hair than for untreated hair. Incorporation of rhodamine 6G followed a pH dependence, but an ionic strength dependence could not be established. These studies support three postulates: (1) electrostatic interactions explain the preferential binding of cationic drugs of abuse to hair; (2) the hair matrix, or the non-helical portion of hair, is accessible to external solutions and thus subject to contamination; and (3) cosmetic treatments may alter the helical portion of hair thereby increasing its accessibility to external contamination.  相似文献   
986.
987.
988.
989.
990.
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