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   11666篇
  免费   331篇
各国政治   603篇
工人农民   360篇
世界政治   796篇
外交国际关系   401篇
法律   7312篇
中国共产党   2篇
中国政治   48篇
政治理论   2353篇
综合类   122篇
  2020年   122篇
  2019年   147篇
  2018年   203篇
  2017年   233篇
  2016年   248篇
  2015年   202篇
  2014年   203篇
  2013年   1245篇
  2012年   323篇
  2011年   308篇
  2010年   256篇
  2009年   254篇
  2008年   314篇
  2007年   291篇
  2006年   289篇
  2005年   263篇
  2004年   268篇
  2003年   262篇
  2002年   273篇
  2001年   461篇
  2000年   432篇
  1999年   334篇
  1998年   147篇
  1997年   153篇
  1996年   119篇
  1995年   136篇
  1994年   141篇
  1993年   124篇
  1992年   237篇
  1991年   247篇
  1990年   252篇
  1989年   249篇
  1988年   226篇
  1987年   219篇
  1986年   250篇
  1985年   226篇
  1984年   199篇
  1983年   206篇
  1982年   124篇
  1981年   122篇
  1980年   100篇
  1979年   155篇
  1978年   117篇
  1977年   92篇
  1976年   89篇
  1975年   109篇
  1974年   133篇
  1973年   122篇
  1972年   103篇
  1971年   88篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The fingernail ridge patterns of a pair of identical twins were compared to each other, their parents, and an unrelated subject. The patterns of the twins' nails showed regions of strong similarity but were distinguishable from one another. Fewer similarities were found when comparing the nails to those of the parents and the unrelated control. The twins were shown to be monozygotic by means of DNA profiling. This therefore represents the first demonstration of unique fingernail ridge patterns in subjects shown conclusively to be identical twins. When the fingernail ridge patterns were examined with a scanning electron microscope, the backscattered electron (BEI) images were found to have superior contrast when compared to the secondary electron (SEI) images.  相似文献   
72.
Recent British work has focused attention on preventing repeat victimization as part of an overall crime prevention strategy. Because domestic violence victims are among those most likely to suffer multiple victimizations, they are logical candidates for programs targeted at reducing repeat victimization.
This article reports on a joint law enforcement-social services approach to reduce the incidence of repeat domestic violence. The research design randomly assigned households reporting domestic incidents within two public housing police service areas in New York to receive or not receive a follow-up to the initial patrol response. (The follow-up visit was conducted by a police officer and a social worker.) In addition, housing projects in the same area were randomly assigned to receive or not receive public education about domestic violence.
Neither treatment produced a reduction in violence. However, households in projects that had received public education and households that received the follow-up visits were both more likely to report new violence to the police than households that did not receive the treatments. Moreover, the effect of the follow-up visit was most pronounced among households with more serious histories of violence. The results suggest that the interventions increased citizens' confidence in the ability of the police to handle domestic situations.  相似文献   
73.
74.
Quadratic pieces of fleece measuring 16 mm2 were soaked with 10 different blood-samples in the dilution steps of 1:1, 1:10, 1:100, 1:1000, respectively, and were tested in blood group typing and identification tests of forensic serology. The above spezified dilutions correspond with 5 microliters, 0.5 microliter, 0.05 microliter and 0.005 microliter of blood, respectively. The detection limit of the microspectrometric test for blood was the dilution 1:10, of the porphyrine test a dilution above 1:100, whereas the preliminary test for blood (peroxidase) succeeded always up to a dilution of 1:1000 and the species determination by the radial immunodiffusion test in agar gels succeeded in most cases op to a dilution of 1:1000. The detection limit of the anti-human globulin inhibition test was between the dilution steps 1:10 and 1:100 when non-titrated and undiluted anti-human globulin serum was used. Gc- and ABO-grouping were possible up to a dilution of 1:100 and were thus the most sensitive grouping systems. Phenotyping of the enzyme-systems and the Gm/Km-system usually required stains with considerably higher blood concentrations i.e. stains of undiluted blood.  相似文献   
75.
76.
Telecommunications regulation has experienced a fundamentalshift from rate regulation to increased reliance on compelledaccess, perhaps best exemplified by the Telecommunications Actof 1996's imposition of no fewer than four new access requirements.Unfortunately, each access requirement is governed by a separateset of rules for determining both the scope and the price ofaccess. The resulting ad hoc regime has created difficult definitionalproblems and opportunities for regulatory arbitrage. In thisarticle we propose a system inspired by the discipline of mathematicsknown as graph theory that integrates all of the different formsof access into a single analytical framework. This system separatesdifferent access regimes into five categories: (1) retail access,(2) wholesale access, (3) interconnection access, (4) platformaccess, and (5) unbundled access. It also provides insightsinto how each type of access complicates the already difficultproblems of network configuration and management and introducesinefficient biases into decisions about network capacity anddesign. The approach we propose also provides insights intothe transaction cost implications of the different types ofaccess. Drawing on the Coasean theory of the firm, our approachexamines the tradeoffs between internal governance costs andthe external transaction costs of providing access to offera theory of network boundaries. This framework shows how accessregulation distorts networks' natural boundaries and providesa basis for evaluating whether private ordering through marketswould lead to more efficient network design.  相似文献   
77.
Eighteen external quality assessment (proficiency testing) samples were prepared from client specimens collected with the Intercept® oral fluid collection device and by spiking drug-free oral fluid. Samples were circulated in pairs at quarterly intervals to 13 UK and USA based laboratories for analysis by a panel of OraSure micro-plate Intercept® enzyme immunoassay kits and hyphenated mass spectrophotometric techniques. During the survey, there was a single case of non-specificity in a false report for methadone. The major errors were of lack of sensitivity relative to the concentration thresholds specified for the immunoassays. The sensitivity for overall ‘present’/‘not found’ reports calculated as true positives/(true positives + false negatives) were for the amfetamine specific assay 50%, methyl-amfetamines 93%, barbiturates 64%, cannabinoids 73%, cocaine and metabolites 100%, benzodiazepines 69%, methadone 95%, opiates 79% (opiates excluding oxycodone 93%), phencyclidine 93% and human gamma-globulin 97%. A small number of the sensitivity errors were attributable to errors in chromatographic confirmation techniques.  相似文献   
78.
79.
80.
The functional and nutritive circulation in the lungs is connected by anastomoses between the pulmonary and bronchial arteries. The anastomoses have the structure of blocked arteries from which arteriovenous anastomoses proceed to the peribronchial plexus. The pulmonary artery is provided with a flow impulse by the anastomoses, and oxygen-containing blood is admixed with the venous blood, thus forming an "aortalization" in the lungs. By diverting the bloodstream, venous blood can reach the bronchial artery. The peculiarities of the lung circulation are important for vital reactions in the form of macro- and microembolisms. Macroembolisms prove the functionality of the system if branches of the pulmonary artery are closed before the arteries are blocked. A hemorrhagic infarction either arises or does not arise, and the hemorrhagic infarction cannot exceed a certain limit. A microembolism is over and above the anastomoses. If the microembolism is greater, pressure in the arteria pulmonaris can cause blood from the pulmonary artery to overflow into the bronchial artery. Because arteriovenous anastomoses arise from the blocked arteries, microemboli can now reach the systemic circulation. Thus, the system described can explain the passage of microemboli into the systemic circulation, avoiding the capillaries of the lungs; on the other hand, larger microembolisms can prove the functionality of the system.  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