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   486篇
  免费   17篇
各国政治   34篇
工人农民   26篇
世界政治   34篇
外交国际关系   22篇
法律   264篇
政治理论   111篇
综合类   12篇
  2023年   10篇
  2020年   8篇
  2019年   13篇
  2018年   14篇
  2017年   12篇
  2016年   14篇
  2015年   7篇
  2014年   10篇
  2013年   73篇
  2012年   13篇
  2011年   13篇
  2010年   12篇
  2009年   8篇
  2008年   22篇
  2007年   23篇
  2006年   15篇
  2005年   15篇
  2004年   14篇
  2003年   10篇
  2002年   19篇
  2001年   10篇
  2000年   9篇
  1999年   5篇
  1998年   10篇
  1997年   7篇
  1996年   8篇
  1995年   7篇
  1994年   9篇
  1993年   7篇
  1992年   7篇
  1991年   3篇
  1990年   4篇
  1989年   9篇
  1988年   6篇
  1987年   7篇
  1986年   6篇
  1985年   6篇
  1984年   3篇
  1983年   5篇
  1982年   5篇
  1981年   4篇
  1980年   6篇
  1979年   9篇
  1978年   2篇
  1977年   3篇
  1976年   2篇
  1975年   3篇
  1973年   4篇
  1971年   2篇
  1965年   1篇
排序方式: 共有503条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
56.
57.
58.
Cocaine is known to degrade in vivo and in vitro by several hydrolytic mechanisms. A previous study found that the initial amount of cocaine added to plasma could be accounted for by summing the molar concentrations of cocaine's hydrolysis products and the cocaine remaining after hydrolysis. The present study was undertaken to investigate whether or not relationships might exist between such molar concentration sums for different postmortem bodily fluids. Determinations of cocaine, benzoylecgonine, ecgonine methyl ester, and ecgonine were performed using liquid chromatography/mass spectrometry (LC/MS/MS) with heart blood, femoral blood, vitreous humor (VH), and urine (UR). The results demonstrate a strong correlation between blood and VH concentrations (correlation coefficients of 0.88-0.94), weak correlation between the UR and blood concentrations (correlation coefficients of 0.61-0.64), and weak correlation between UR and VH concentrations (correlation coefficient of 0.59). The results demonstrate that ecgonine is a significant hydrolysate with concentrations on the same order of magnitude as benzoylecgonine. The results are consistent with rapid distribution of the parent drug and its hydrolysates in the blood and VH. The strong correlation between the blood and VH demonstrates that VH is an important medium for toxicology testing when attempting to make a determination of cocaine intoxication.  相似文献   
59.
Child-sized pig carcasses (Sus scrofa) were placed in surface deposit and buried scenarios in a wooded area of Virginia from May 1998 through December 2000, to examine the taphonomic effects of decompositional changes, predator scavenging, and the extent of remains scattering. Changes were observed through on-site examination, charting of remains, and recorded video imaging. Analysis of data revealed that utilization of corpses as food sources by vertebrates was dependent upon invertebrate colonization. Vertebrates avoided feeding on the corpses while invertebrate colonization was active, and would feed before invertebrates successfully colonized a corpse, or would wait until the invertebrate populations migrated away from the corpse. Among vertebrates, there was no apparent succession order for the animals utilizing the remains as a food source. Different vertebrates would feed at different times based upon diurnal or nocturnal predilection. Analysis noted an accidental cooperative relationship between the invertebrates and vertebrates scavenging on the corpses. Certain vertebrates gained access to the internal tissues by utilizing openings in the corpses caused by invertebrate and other vertebrate scavenging. Alternately, carrion-frequenting insects were afforded access to previously inaccessible colonization sites as a result of scavenging vertebrate activities.  相似文献   
60.
Previous work in American state politics shows that an accurate measure of legislative decision-making attributes can be a useful tool for empirical research. Using data from a new survey of state legislators, conducted in 1981, the present analysis includes both an improved survey item and a sophisticated scaling procedure.  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