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   7853篇
  免费   215篇
各国政治   262篇
工人农民   259篇
世界政治   552篇
外交国际关系   265篇
法律   5152篇
中国政治   48篇
政治理论   1449篇
综合类   81篇
  2020年   103篇
  2019年   117篇
  2018年   134篇
  2017年   167篇
  2016年   172篇
  2015年   119篇
  2014年   167篇
  2013年   757篇
  2012年   184篇
  2011年   196篇
  2010年   168篇
  2009年   171篇
  2008年   206篇
  2007年   233篇
  2006年   244篇
  2005年   205篇
  2004年   203篇
  2003年   219篇
  2002年   187篇
  2001年   323篇
  2000年   304篇
  1999年   231篇
  1998年   107篇
  1997年   82篇
  1996年   87篇
  1995年   82篇
  1994年   85篇
  1993年   74篇
  1992年   152篇
  1991年   159篇
  1990年   151篇
  1989年   171篇
  1988年   150篇
  1987年   167篇
  1986年   143篇
  1985年   166篇
  1984年   131篇
  1983年   156篇
  1982年   104篇
  1981年   103篇
  1980年   78篇
  1979年   105篇
  1978年   79篇
  1977年   71篇
  1976年   61篇
  1975年   53篇
  1974年   61篇
  1973年   65篇
  1971年   53篇
  1970年   49篇
排序方式: 共有8068条查询结果,搜索用时 15 毫秒
991.
992.
Frozen tissues were studied histologically to determine what changes were produced by freezing. Samples of brain, lung, liver, small intestine, and kidney from 20 stray dogs were treated in 3 ways: formalin fixation (control), frozen for 2 days plus formalin fixation, or frozen for 7 days plus formalin fixation. Major histological changes caused by freezing were loss of staining, extracellular fluid accumulation, cell shrinkage, fractures, hemolysis, and hematin formation. Lesser changes included loss of bronchial cilia, prominence of collagen in alveolar septa and meninges, and intracellular vacuolization of epithelial cells. Although these changes were annoying, adequate visualization of the tissues was usually possible.  相似文献   
993.
994.
995.
Ultrasonic determinations were made of facial tissue thicknesses in 50 healthy American caucasoid children, ranging in age from 4 to 15. Twenty measurements were taken at sites along the median, right sagittal, and right lateral planes. A static scanner was used in the B-mode. Three measurements significantly increased with age, the mid-philtrum (rs = 0.43, p less than 0.01) in females, the mental sulcus (rs = 0.30, p less than 0.05) in males, and the frontal eminence (rs = 0.32, p less than 0.05) in both sexes. Moreover, 25% of the measurements, while not statistically significant, decreased with increasing age. These data provide a basis for facial reproductions in caucasoid children.  相似文献   
996.
The Très Haute Vitesse (THV) bullet was introduced to meet the requirements of law enforcement officers, as an alternative to larger calibre fully jacketed bullets, since expanding or exploding bullets are not relevant in Europe. To examine the effect of the THV bullet in tissue, especially the size of the lesion and the degree of overpenetration, 11 recently killed pigs were shot with the weapons used by the Danish Police Force and a 9-mm pistol for reference. The ammunition was THV in the calibres 7.65 mm, 0.38, and 9 mm, using conventional fully jacketed bullets for comparison. The lesions were considerably larger when the THV bullet was used, the entry wound in particular, being roughly twice the diameter in the case of the THV bullet as compared to the fully jacketed bullet of similar calibre. Only one 7.65-mm THV bullet overpenetrated the target when fired against the thorax or abdomen of the pigs and then with only minimal residual energy. All fully jacketed 7.65-mm bullets, all 0.38 bullets, with the exception of one THV bullet, and all 9-mm bullets overpenetrated the target. The 7.65-mm THV bullet produced a lesion which in its extent resembled that of the fully jacketed 9-mm bullet, and should be a suitable alternative for the Danish Police Force.  相似文献   
997.
India, as the largest democracy, second most populous country, ninth largest industrial power and fifteenth poorest nation, has in respect of health care to be considered as a special case among developing countries. Nevertheless, the identification in India, as an alternative to national welfare provision, of opportunities for returning social and economic responsibilities for health care to local communities is important for both developing and developed countries. This article outlines and comments upon recent developments in providing primary health care in rural communities in India. It concludes by examining possible parallels between self-sustaining community health schemes and the search in developed countries for community and personal involvement so as to overcome emergent limitations of professionalized and welfare systems of care.  相似文献   
998.
999.
It is well-known that modelers and policy analysts gain access to policymaking arenas based on what they know. Therefore, critics of models are quick to employ various types of technical standards when evaluating policy models in order to assess validity and reliability of claims to knowledge. This article argues that, in the effort to make models better, overreliance on technical standards misses the important political and policy reasons to model: models call attention to the modelers and to their advice about important policy problems of the day. In this sense, models are used as symbols, as claims to authority, whether or not the underlying knowledge is technically up to snuff. Drawing on the experience of energy policy models, this article explores the problem of models as knowledge versus models as symbols and it examines the muddle that conflicts between them produce.  相似文献   
1000.
The absorption-elution technique with low ionic strength solution (LISS) and papain-treated test cells previously used for bloodstains was employed for the detection of ABO antigens on human hair. Antigen identification was always possible, with good intensity of agglutination, even in those cases where classic techniques had given false-negative results. It was possible to obtain positive results with fragments of human hair as small as 0.2 cm.  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