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   17762篇
  免费   465篇
各国政治   751篇
工人农民   683篇
世界政治   1480篇
外交国际关系   639篇
法律   10494篇
中国共产党   2篇
中国政治   89篇
政治理论   3906篇
综合类   183篇
  2020年   218篇
  2019年   264篇
  2018年   352篇
  2017年   409篇
  2016年   426篇
  2015年   304篇
  2014年   358篇
  2013年   1757篇
  2012年   423篇
  2011年   441篇
  2010年   357篇
  2009年   402篇
  2008年   459篇
  2007年   486篇
  2006年   456篇
  2005年   403篇
  2004年   411篇
  2003年   428篇
  2002年   398篇
  2001年   689篇
  2000年   638篇
  1999年   523篇
  1998年   296篇
  1997年   261篇
  1996年   214篇
  1995年   215篇
  1994年   253篇
  1993年   227篇
  1992年   346篇
  1991年   376篇
  1990年   336篇
  1989年   350篇
  1988年   324篇
  1987年   345篇
  1986年   345篇
  1985年   340篇
  1984年   290篇
  1983年   322篇
  1982年   260篇
  1981年   245篇
  1980年   186篇
  1979年   255篇
  1978年   169篇
  1977年   149篇
  1976年   133篇
  1975年   128篇
  1974年   140篇
  1973年   122篇
  1972年   113篇
  1971年   98篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
This article examines the portrayal of pregnancy and alcohol in thirty-six national network evening news broadcasts (ABC, CBS, NBC). Early coverage focused on white, middle-class women, as scientific authorities and government officials warned against drinking during pregnancy. After 1987, however, women who drank during pregnancy were depicted as members of minority groups and as a danger to society. The thematic transition began before warning labels appeared on alcoholic beverages and gained strength from official government efforts to prevent fetal alcohol syndrome. The greatest impetus for the revised discourse, however, was the eruption of a "moral panic" over crack cocaine use. By linking fetal harm to substance abuse, the panic suggested it was in the public's interest to control the behavior of pregnant women.  相似文献   
982.
983.
By means of the new method of Streifenlichttopometrie (SLT) it is possible to record the complete body surface of casualties in a practically photorealistic fashion, i.e. three-dimensionally and in colour. In comparison with the classic method of Photogrammetry Streifenlichttopometrie (SLT) is remarkably faster (10,000 points/s instead of 1 point/s) and in addition the colour of every point measured upon the corpse's surface is instantly recorded. Taking into consideration the resolution required and the qualities of the camera system the body surface is recorded in 'patches', i.e., areas of a defined extension (in the present case 500 mmx500 mmx200 mm) which are marked with a body fixed reference frame to grant the exact matching of the data after the recording process. Length, perimeter, square and volume of the body segments and injuries can be determined. Furthermore the natural colour of the wounds can be used for an immediate classification according to the intensity of the impact forces. In addition the 3-D coordinates of the body surface including the wounds can be transferred into an animated computer simulation for the reconstruction of the traumatic events.  相似文献   
984.
DNA typing is often used to determine identity from human remains. The environment to which the material has been exposed, however, is crucial for the success of the investigation. Damp conditions in particular can cause a rapid degradation of DNA, even in bone and teeth, and thus reduce the chances of successful typing. Here, we present the results of investigations performed on four skulls that had been lying in a damp environment for periods ranging from almost 1 year to about 45 years. In none of these cases was DNA typing successful on bone or, where present, on teeth. Where remnants of brain tissue were used, however, complete STR typing was possible in one case, partial STR typing in another, and mtDNA sequencing could be carried out in three cases. These findings suggest that brain tissue is relatively resistant to putrefaction in damp environments and, unlike bone, appears to exhibit a certain degree of protection against DNA degradation.  相似文献   
985.
Pontocerebellar hypoplasia (PCH) is a very rare congenital (autosomal recessive) condition with fetal onset. Only a few cases have been published on the basis of both clinical data (symptoms/neuroradiological imaging) and autopsy results. This paper reports on such a case involving a 1.5-year-old male infant. The child suffered from severe psychomotor delay, extrapyramidal dyskinesia and epileptic seizures, but did not exhibit signs of spinal muscular atrophy as related to PCH type 1. Magnetic resonance imaging (MRI) at the age of 6 months demonstrated olivo-pontine and bilateral cerebellar hypoplasia. The boy was unexpectedly found dead. Autopsy disclosed a severe aspiration of gastric contents as the final cause of death. The neuropathological examination confirmed PCH type 2 (according to Barth [Brain Dev., 15 (1993) 411-422]) with marked microcephaly and olivopontocerebellar hypoplasia. Histologically, decreased density of olivo-pontine neurons, reduction of granular and Purkinje's cell layers of the cerebellum, slight astroglial proliferation and fragmented appearance of the dentate nuclei were observed. The immunohistochemical expression pattern was determined using antibodies against glial fibrillary acidic protein, synaptophysin and neurofilament protein. Summarizing, typical features of PCH type 2 were present and proved by clinical course, MRI and autopsy. Despite severe symptoms due to a natural disease this rare neurogenetic entity can become of forensic interest, when sudden unexpected death occurs.  相似文献   
986.
Between 1997 and 1999 a steady increase in cornea donations was achieved, but the number of transplantations remained stable because many grafts did not pass quality control. Intermediate organ culture of entire bulbi was examined as a possible solution to reduce post-mortem times and increase suitability for transplantation.  相似文献   
987.
This paper describes a collaborative exercise organised under the auspices of the European Network of Forensic Science Institutes (ENFSI). The purpose of this EU (European Union) funded group is to carry out research to enable STR loci to be compared between European laboratories, ultimately leading to the formation of a pan-European database. Accordingly, an exercise was designed to evaluate a prototype STR multiplex system manufactured by Applied Biosystems (ABD). Each laboratory was sent 12 samples to analyse along with a multiplex kit. Of specific interest was the definition of parameters to define the efficiency of the system. Stutter, split allelic peaks (differing by one base), pull-up, heterozygous balance and between locus balance were all objectively measured. Once the important parameters are defined it is possible to directly compare performances of different multiplexes and the different laboratories carrying out the tests. Since the multiplex used was a prototype system, this exercise cannot be regarded as a proficiency test.  相似文献   
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