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   7434篇
  免费   226篇
各国政治   357篇
工人农民   298篇
世界政治   585篇
外交国际关系   260篇
法律   4333篇
中国政治   52篇
政治理论   1693篇
综合类   82篇
  2020年   85篇
  2019年   109篇
  2018年   156篇
  2017年   144篇
  2016年   159篇
  2015年   117篇
  2014年   125篇
  2013年   818篇
  2012年   171篇
  2011年   183篇
  2010年   172篇
  2009年   160篇
  2008年   188篇
  2007年   188篇
  2006年   211篇
  2005年   197篇
  2004年   179篇
  2003年   184篇
  2002年   181篇
  2001年   230篇
  2000年   193篇
  1999年   167篇
  1998年   109篇
  1997年   96篇
  1996年   73篇
  1995年   85篇
  1994年   84篇
  1993年   91篇
  1992年   128篇
  1991年   164篇
  1990年   142篇
  1989年   151篇
  1988年   149篇
  1987年   162篇
  1986年   150篇
  1985年   154篇
  1984年   138篇
  1983年   141篇
  1982年   107篇
  1981年   99篇
  1980年   95篇
  1979年   100篇
  1978年   80篇
  1977年   62篇
  1976年   70篇
  1975年   67篇
  1974年   72篇
  1973年   69篇
  1972年   56篇
  1969年   57篇
排序方式: 共有7660条查询结果,搜索用时 15 毫秒
891.
892.
Histopathological changes in selenium-exposed fish   总被引:1,自引:0,他引:1  
Redear sunfish (Lepomis microlophus) were collected from Martin Lake in east Texas. For at least 8 months, 1 year earlier, aqueous selenium-laden effluent from man-made sources was released into this 5,000-acre reservoir (unpublished data). Redear sunfish from a reference lake, 8 km upstream, were collected for comparison to Martin Lake fish. The hepatopancreas (i.e., liver and associated, disseminated exocrine pancrease), mesonephros (i.e., kidney), gonads, heart, spleen, stomach, and gill arches were preserved for histopathological examination using optical and/or transmission electron microscopy. Livers from Martin Lake redear sunfish (which had accumulated approximately 20 ppm selenium in the liver) showed central necrosis, reduced quantities of rough endoplasmic reticulum and glycogen particles, and increased numbers of lysosome-like structures. Kidneys showed proliferative glomerulonephritis, and exocrine pancreas showed marked hypertrophy at the optical level. Ultrastructurally, architectural disorganization, reduced rough endoplasmic reticulum, increased cisternal space, and proliferation of smooth endoplasmic reticulum were evident. The stomach, spleen, gill, heart, and gonads showed no abnormalities.  相似文献   
893.
894.
895.
896.
897.
The Consumer Price Index (CPI) is widely used to adjust wages and federal benefits as an offset to inflation, but the index contains substantial sources of bias as used for such purposes. For instance, these sources of bias, such as changes in the real cost of petroleum, the cost of environmental protection, and an inappropriate method for measuring homeownership costs, accounted for nearly half of the CPI increase in the year from November 1978 to November 1979. Because of the nature of the index, such biases will always be present, creating the risk that the CPI may be adding to the inflation that it is only supposed to measure. Therefore, a new index or indexes that are more appropriate for adjusting wages and benefits for inflation should be developed.  相似文献   
898.
899.
900.
The techniques of thin-layer chromatography, gas chromatography with electron capture detection, and gas chromatography/mass spectrometry were used to analyze hand swab extracts for the presence of nitroglycerine. Both the amount of nitroglycerine transferred to the hands after handling commercial explosives and its persistence were measured. Gas chromatography-electron capture detection was found to be the most accurate and sensitive technique for making such determinations, especially if the extract was partially purified by thin-layer chromatography prior to analysis. The lowest limit of detection was 10 ng of nitroglycerine, and residues could be detected over 20 h after handling the raw explosive.  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