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   9002篇
  免费   269篇
各国政治   317篇
工人农民   370篇
世界政治   611篇
外交国际关系   290篇
法律   5977篇
中国共产党   9篇
中国政治   98篇
政治理论   1510篇
综合类   89篇
  2020年   120篇
  2019年   152篇
  2018年   172篇
  2017年   207篇
  2016年   218篇
  2015年   158篇
  2014年   200篇
  2013年   855篇
  2012年   234篇
  2011年   248篇
  2010年   214篇
  2009年   208篇
  2008年   267篇
  2007年   272篇
  2006年   286篇
  2005年   233篇
  2004年   251篇
  2003年   254篇
  2002年   218篇
  2001年   415篇
  2000年   363篇
  1999年   295篇
  1998年   124篇
  1997年   83篇
  1996年   91篇
  1995年   85篇
  1994年   91篇
  1993年   76篇
  1992年   167篇
  1991年   173篇
  1990年   184篇
  1989年   189篇
  1988年   169篇
  1987年   176篇
  1986年   152篇
  1985年   171篇
  1984年   134篇
  1983年   149篇
  1982年   109篇
  1981年   105篇
  1980年   79篇
  1979年   109篇
  1978年   84篇
  1977年   70篇
  1976年   63篇
  1975年   48篇
  1974年   58篇
  1973年   61篇
  1971年   54篇
  1970年   49篇
排序方式: 共有9271条查询结果,搜索用时 15 毫秒
991.
This study investigated the postmortem molecular changes that articular cartilage undergoes following burial. Fresh pig trotters were interred in 30‐cm‐deep graves at two distinct locations exhibiting dissimilar soil environments for up to 42 days. Extracts of the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joint cartilage from trotters disinterred weekly over 6 weeks were analyzed by Western blot against the monoclonal antibody 2‐B‐6 to assess aggrecan degradation. In both soil conditions, aggrecan degradation by‐products of decreasing molecular size and complexity were observed up to 21 days postmortem. Degradation products were undetected after this time and coincided with MCP/MTP joint exposure to the soil environment. These results show that cartilage proteoglycans undergo an ordered molecular breakdown, the analysis of which may have forensic applications. This model may prove useful for use as a human model and for forensic investigations concerning crimes against animals and the mortality of endangered species.  相似文献   
992.
Computer methods have been developed for mathematically interpreting mixed and low‐template DNA. The genotype modeling approach computationally separates out the contributors to a mixture, with uncertainty represented through probability. Comparison of inferred genotypes calculates a likelihood ratio (LR), which measures identification information. This study statistically examined the genotype modeling performance of Cybergenetics TrueAllele® computer system. High‐ and low‐template DNA mixtures of known randomized composition containing 2, 3, 4, and 5 contributors were tested. Sensitivity, specificity, and reproducibility were established through LR quantification in each of these eight groups. Covariance analysis found LR behavior to be relatively invariant to DNA amount or contributor number. Analysis of variance found that consistent solutions were produced, once a sufficient number of contributors were considered. This study demonstrates the reliability of TrueAllele interpretation on complex DNA mixtures of representative casework composition. The results can help predict an information outcome for a DNA mixture analysis.  相似文献   
993.
Four fluorescent fingerprint powders (RedWop?, GreenWop?, Basic Yellow?, and Yellow Powder?) were evaluated as a marker for blow fly larvae. Administration methods included ingestion (high vs. low concentration) or topical. Ingestion of high concentrations of Basic Yellow? and RedWop? caused higher larval mortality. Basic Yellow? delayed development and adult emergence while RedWop? and Yellow Powder? had a significant effect on particular stages of development, however, emergence time was not altered. Optimal administration is through ingestion at low concentration levels (<10%) or topically, with GreenWop? demonstrating minimal adverse effects. Optimum wavelength for discrimination between powders was 450 nm. This research can aid in investigative training to increase visibility of larval and pupal blow flies. It can also be used in entomological studies to differentiate between larval blow flies (or other dipteran) species or individuals to further understand complex interactions and behavior during larval development.  相似文献   
994.
995.
996.
The Covenant of Mayors (CM) is the mainstream European movement involving local authorities who voluntarily commit to increase energy efficiency and the use of renewable energy sources within their territories with the aim of reducing CO2 emissions and meet the European Union objectives by 2020. One country that has a greater number of signatories of this agreement is Spain. This article analyzes which factors influence the decision of Spanish local authorities to join the ever‐growing movement. An empirical model is formulated to describe the behavior of Spanish local governments, this being a binary choice model which is a function of various political, economic, and technical factors. Among the prominent factors that influence this decision are population, availability of renewable energy, fiscal and environmental stress, citizens’ political preference, the contagion effect of neighboring municipalities, the existence of covenant coordinators, and finally, economic motivations.  相似文献   
997.
998.
999.
Elevated levels of carbon monoxide and cyanide serve as evidence of intravital burning in fire victims. Hydrogen cyanide is released by combustion of nitrogen-containing organic material such as plastics and wool. We present a case of a man who died of haemopneumothorax caused by a stab wound. According to several eye witnesses the body was wrapped in a plastic sheet and burned 2 days after death with the aid of gasoline. No coal pigment was observed in the mucosa of the upper airways at autopsy. The blood sample taken from the pulmonary vessels 6 days after death disclosed a level of blood carboxyhaemoglobin of 4% and of blood cyanide of 10 mg/l. The low carboxy-haemoglobin level was consistent with the smoking habits of the victim. The thoracic cavity had been opened by burning of the intercostal soft tissue. This allowed hydrogen cyanide gas to enter the thoracic cavity and diffuse into the blood probably causing the high blood-cyanide level.  相似文献   
1000.
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