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   18094篇
  免费   1367篇
各国政治   758篇
工人农民   551篇
世界政治   1262篇
外交国际关系   552篇
法律   12929篇
中国共产党   2篇
中国政治   100篇
政治理论   3148篇
综合类   159篇
  2020年   384篇
  2019年   412篇
  2018年   491篇
  2017年   558篇
  2016年   594篇
  2015年   518篇
  2014年   527篇
  2013年   1872篇
  2012年   455篇
  2011年   526篇
  2010年   657篇
  2009年   609篇
  2008年   456篇
  2007年   402篇
  2006年   509篇
  2005年   373篇
  2004年   363篇
  2003年   363篇
  2002年   347篇
  2001年   688篇
  2000年   590篇
  1999年   485篇
  1998年   217篇
  1997年   225篇
  1996年   176篇
  1995年   206篇
  1994年   226篇
  1993年   191篇
  1992年   357篇
  1991年   388篇
  1990年   348篇
  1989年   377篇
  1988年   335篇
  1987年   306篇
  1986年   350篇
  1985年   339篇
  1984年   332篇
  1983年   306篇
  1982年   218篇
  1981年   200篇
  1980年   180篇
  1979年   249篇
  1978年   152篇
  1977年   134篇
  1976年   120篇
  1975年   132篇
  1974年   147篇
  1973年   131篇
  1972年   116篇
  1971年   110篇
排序方式: 共有10000条查询结果,搜索用时 154 毫秒
941.
Lemonick MD 《Time》2000,156(18):66-70, 73-4
  相似文献   
942.
943.
Index     

Other Index

Index  相似文献   
944.
A 33 year-old Polish field-worker was found by his colleagues kneeling in front of his trailer, with a bloody stab wound in the heart region. In spite of prompt surgical intervention, the man died from his injury a few hours later. Upon examination of the dead man's trailer a blood-smeared vegetable-knife was found in the sink, and on the floor, a pullover with a slit-like cut. On the wall hung a jacket on a hook with a cut in the inner surface of the left breast pocket but not in the outside layer. The examination of the clothes, the autopsy and a reconstruction of the sequence of events led to the following conclusion: The knife had been placed into the breast pocket of the jacket with the tip facing downwards. As the man put down a sack of potatoes, the knife hooked into a pre-existing gap in the sack and was driven into the chest cavity by the pressure weight of the heavy sack.  相似文献   
945.
An intoxication following administration of morphine, tramadol and atracurium in a suicide case is reported. The route of administration and the amount of the particular drug were known from the investigation of the death scene and the findings of the postmortem examination. Tramadol was present in the gastric contents as well as in blood, liver, kidney and brain samples, whereas the drug could not be detected in muscle. All body fluids and tissues investigated contained morphine as well as its 3- and 6-glucuronides with the exception of muscle tissue. The concentrations of morphine and its glucuronide metabolites were determined by LC/MS following solid phase extraction. Interestingly, the concentration of M6G in brain, liver and kidney were close to the concentration of M3G in the particular tissue. This phenomenon might be explained by a preferential hydrolysis of M3G or by a preferential formation of M6G postmortem. Measurement of morphine and M6G in femoral blood and cerebrospinal fluid may be a useful indicator in rapid deaths.  相似文献   
946.
Recent criminal acts in the United Kingdom, United States and other countries have demonstrated the dangers to public safety from the criminal use of improvised explosives on a large scale. Four sets of trials were carried out over four years, partly in collaboration with the United States Federal Bureau of Investigation, involving the firing of large bombs, mostly fertilizer based. The principal objectives of the firings were to measure the physical effects of the explosions upon objects representative of those that would be found at a real bomb scene and to recover any chemical traces deposited on these objects. The results are intended for use as an aid in determining the approximate size and type of an explosive employed in a terrorist attack. This paper describes the background behind the trials, the procedures for preparation of witness materials and charges, and the collection and analysis of physical and chemical evidence.  相似文献   
947.
Cranes are machines used to move heavy objects. Cranes are operated by crane operators, usually working in conjunction with an assistant guiding the movements of the crane from his vantage point outside the crane. Few jurisdictions require that crane operators be either licensed or certified. We conducted a retrospective study of those dying of crane-related injuries in our jurisdiction during the 16 years from 1981 to 1996. All ten decedents were male, and the manner of each death was accidental. Neither ethanol nor drugs of abuse were detected in any case. Eight of the ten decedents died due to blunt force injuries, one due to mechanical asphyxia, and one due to thermal burns. Investigation by the Occupational Safety and Health Administration (OSHA) led to fines ranging from $80 to $2700 in six of the ten cases. Nationwide, electrocution is the most common cause of crane-related death, but no crane-related death in Jefferson County was caused by electrocution in our study. The absence of electrocutions was due to the planned, routine suspension of power to electrical lines in the vicinity of a crane during the crane's operation, a practice saving an estimated seven lives. Nevertheless, human error or lack of planning was still responsible for most of the deaths in our study. In addition to careful planning and adherence to safety standards established by planning, we recommend the mandatory licensure and certification of professional crane operators and the assessment of larger fines by OSHA for safety standard violations.  相似文献   
948.
Population genetics of nine STR loci in two populations from Brazil   总被引:2,自引:0,他引:2  
The Short Tandem Repeats (STRs) D3S1358, HUMvWA31/A, HUMFIBRA/FGA, D8S 1179, D2S11, D18S51, D5S818, D13S317, and D7S820 were studied in two Brazilian populations (from Amazonia and S. Paulo) using the "AmpF1 STR Profiler Plus PCR Amplification Kit." The nine loci showed a combined discrimination power greater than 0.9999999999 and a chance of exclusion of 0.9999.  相似文献   
949.
Our laboratory was asked to help with the rehydration of mummified human fingertips that had been removed from a recently deceased, unidentified female. Using a solution that was found in the archeological literature, we were able to successfully rehydrate dermal tissues to the extent that fingerprints could be taken. We believe that this solution, which until now has not been described in the forensic literature, is effective, affordable, and relatively easy to produce and use.  相似文献   
950.
During fatal aviation accident investigations, biosamples from the victims are submitted to the FAA Civil Aeromedical Institute (CAMI) for drug analysis. In the process of one such analysis by CAMI, an unknown substance was found in a urine sample. Simultaneous screening by thin layer chromatography (TLC) and gas chromatography/FID (GC/FID) suggested the presence of pseudoephedrine. A subsequent routine confirmation analysis of a separate urine aliquot by GC Fourier transform infrared (GC/FTIR) and GC mass spectrometry (GC/MS) indicated that the retention times of the unknown substance matched with those of pseudoephedrine. However, its infrared and mass spectra were different--the -OH and -NH groups were missing, a C-O-C group was present, and the molar mass was 12 atomic mass units (amu) more than that of pseudoephedrine. A subsequent literature search suggested that ephedrine-like amines react with aldehydes to form oxazolidines. Therefore, the 12-amu increase could be accounted for by condensation of pseudoephedrine with formaldehyde. Since this aldehyde is present in various grades of methanol and ethyl acetate, and these solvents were used during the solid-phase extraction, 3,4-dimethyl-5-phenyl-1,3-oxazolidine was synthesized by using (+)-pseudoephedrine HCl and formaldehyde. The analytical findings of the synthesized compound were consistent with those of the unknown interfering substance, confirming that it was the oxazolidine. Aldehyde contaminants in solvents or specimens can transform drugs of interest and may result in misidentification of a compound originally present in specimens. Therefore, chemicals used in analyses should be of the highest available purity, and a multi-analytical approach should be adopted to maintain a high degree of quality assurance.  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