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   1309篇
  免费   52篇
各国政治   50篇
工人农民   163篇
世界政治   88篇
外交国际关系   73篇
法律   622篇
中国政治   10篇
政治理论   337篇
综合类   18篇
  2023年   4篇
  2022年   5篇
  2021年   7篇
  2020年   19篇
  2019年   31篇
  2018年   40篇
  2017年   57篇
  2016年   53篇
  2015年   40篇
  2014年   50篇
  2013年   222篇
  2012年   35篇
  2011年   49篇
  2010年   30篇
  2009年   21篇
  2008年   44篇
  2007年   51篇
  2006年   43篇
  2005年   42篇
  2004年   44篇
  2003年   34篇
  2002年   22篇
  2001年   17篇
  2000年   28篇
  1999年   23篇
  1998年   14篇
  1997年   20篇
  1996年   11篇
  1995年   23篇
  1994年   20篇
  1993年   16篇
  1992年   12篇
  1991年   12篇
  1990年   12篇
  1989年   11篇
  1988年   20篇
  1987年   7篇
  1986年   11篇
  1985年   15篇
  1984年   14篇
  1983年   13篇
  1982年   20篇
  1981年   18篇
  1980年   12篇
  1979年   12篇
  1978年   11篇
  1977年   8篇
  1976年   10篇
  1975年   4篇
  1973年   4篇
排序方式: 共有1361条查询结果,搜索用时 15 毫秒
71.
Specimens from fatal aviation accident victims are submitted to the FAA Civil Aerospace Medical Institute for toxicological analysis. During toxicological evaluations, ethanol analysis is performed on all cases. Care must be taken when interpreting a positive ethanol result due to the potential for postmortem ethanol formation. Several indicators of postmortem ethanol formation exist; however, none are completely reliable. The consumption of ethanol has been shown to alter the concentration of two major serotonin metabolites, 5-hydroxytryptophol (5-HTOL) and 5-hydroxyindole-3-acetic acid (5-HIAA). While the 5-HTOL/5-HIAA ratio is normally very low, previous studies using living subjects have demonstrated that the urinary 5-HTOL/5-HIAA ratio is significantly elevated for 11-19 h after acute ethanol ingestion. Recently, our laboratory developed and validated an analytical method for the simultaneous determination of both 5-HTOL and 5-HIAA in forensic urine samples using a simple liquid/liquid extraction and LC/MS/MS and LC/MS/MS/MS. In this previous work a 15 pmol/nmol serotonin metabolite ratio cutoff was established in postmortem urine, below which it could be conclusively determined that no recent antemortem ethanol consumption had occurred. In the current study this newly validated analytical method was applied to five ethanol-positive aviation fatalities where the origin of the ethanol present could not previously be conclusively determined. In four of the five cases examined the detected ethanol was demonstrated to be present due to postmortem microbial formation, and not consumption, even though some indication of ethanol consumption may have been present.  相似文献   
72.
A collaborative study on Raman spectroscopy was carried out by members of the ENFSI (European Network of Forensic Science Institutes) European Fibres Group (EFG) on three dyed fibers: two red acrylics and one red wool. Raman instruments from six different manufacturers were tested as well as nine different laser wavelengths ranging from blue (lambda = 458 nm) to near infrared-NIR (lambda = 1064 nm). This represents the largest comparison study of Raman analytical parameters carried out on identical fiber samples. For the chosen fiber and dye samples, red lasers (lambda = 633 and 685 nm) gave the poorest spectral quality whereas blue (458 nm), green (514 nm) and near infrared lasers (785, 830 and 1064 nm) provided average results. Blue (488 nm) and green lasers (532 nm) globally gave the best quality spectra. Fluorescence problems were often encountered with some of the excitation wavelengths and therefore a flexible Raman instrument equipped with different lasers can be recommended to measure forensic fiber samples. The instrument should also be equipped with a Raman microscope in order to be able to focus on a single fiber. This study shows that Raman spectroscopy usually enables the identification of the main dye present in a colored fiber; however, minor dye components are much more difficult to detect. SERRS (Surface Enhanced Resonance Raman Scattering) techniques give an improvement of the dye's spectral intensity but no spectral improvement was observed for the two red acrylic and red wool fibers tested.  相似文献   
73.
Bad medicine     
Quinn JB 《Newsweek》2004,144(17):52-53
  相似文献   
74.
75.
76.
77.
78.
Diphenhydramine is an antihistamine available in numerous over-the-counter preparations. Often used for its sedative effects in adults, it can cause paradoxical central nervous system stimulation in children, with effects ranging from excitation to seizures and death. Reports of fatal intoxications in young children are rare. We present five cases of fatal intoxication in infants 6, 8, 9, 12, and 12 weeks old. Postmortem blood diphenhydramine levels in the cases were 1.6, 1.5, 1.6, 1.1 and 1.1 mg/L, respectively. Anatomic findings in each case were normal. In one case the child's father admitted giving the infant diphenhydramine in an attempt to induce the infant to sleep; in another case, a daycare provider admitted putting diphenhydramine in a baby bottle. Two cases remain unsolved; one case remains under investigation. The postmortem drug levels in these cases are lower than seen in adult fatalities. We review the literature on diphenhydramine toxicity, particularly as it pertains to small children, and discuss the rationale for treating these cases as fatal intoxications.  相似文献   
79.
Fighting for air     
Johnson D 《Newsweek》2003,142(12):54
  相似文献   
80.
Adolescents from four schools (one inner-city, two suburban, and one private) were tested two or three times using the Washington University Sentence Completion Test of Ego Development. Testing intervals ranged from 1.5 to 6 years. About half (N=193) the original pool was retested at twelfth grade. Every sample showed a mean rise in ego level; for six of eight samples that rise was statistically significant. Every pair of testings showed a postive correlation between scores; 10 of 14 correlations were significantly different from zero. Thus both test-retest correlations (about 0.5) and change scores support the hypothesized sequence of ego development. Significant correlation between ego level and intelligence occurred in two schools (0.6 at elementary and junior high grades and 0.4 at twelfth grade), but correlation was about zero in the private school.These studies were supported by Grant MH-05115 and Research Scientist Award MH-00657, both from the National Institute of Mental Health, Public Health Service.Received her Ph.D. from Washington University. Main interest is adolescent development.Received her Ph.D. from the University of California, Berkeley. Main interest is theory and measurement of ego development.  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