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   16749篇
  免费   1373篇
各国政治   787篇
工人农民   556篇
世界政治   1352篇
外交国际关系   698篇
法律   11101篇
中国共产党   1篇
中国政治   129篇
政治理论   3366篇
综合类   132篇
  2023年   70篇
  2021年   81篇
  2020年   413篇
  2019年   444篇
  2018年   574篇
  2017年   629篇
  2016年   689篇
  2015年   548篇
  2014年   554篇
  2013年   2023篇
  2012年   438篇
  2011年   519篇
  2010年   662篇
  2009年   623篇
  2008年   470篇
  2007年   470篇
  2006年   541篇
  2005年   416篇
  2004年   403篇
  2003年   369篇
  2002年   350篇
  2001年   539篇
  2000年   437篇
  1999年   395篇
  1998年   219篇
  1997年   211篇
  1996年   171篇
  1995年   192篇
  1994年   209篇
  1993年   191篇
  1992年   280篇
  1991年   294篇
  1990年   272篇
  1989年   275篇
  1988年   261篇
  1987年   214篇
  1986年   250篇
  1985年   258篇
  1984年   258篇
  1983年   218篇
  1982年   172篇
  1981年   160篇
  1980年   146篇
  1979年   169篇
  1978年   111篇
  1977年   95篇
  1976年   79篇
  1975年   84篇
  1974年   108篇
  1973年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Gel ink pens have become a common writing instrument in the United States. Questioned document examiners often attempt to optically differentiate gel inks from each other and from other non-ballpoint ink writings (e.g., those from roller-ball pens). Since early formulations were primarily pigment-based, they do not elute when analyzed by thin-layer chromatography. However, recent gel ink formulations (i.e., within the past five years) include dye-based inks that can be easily separated. This study differentiates black gel inks using optical and chemical techniques. The techniques include: microscopy, visible and near infrared reflectance, near infrared luminescence, thin-layer chromatography (TLC), spot tests, and gas chromatography/mass spectrometry (GC/MS). As a result of this study a flow chart has been developed allowing for a systematic determination of a questioned ink. In addition, an analysis of volatile compounds found in gel inks revealed that there are some unique ingredients that may be found in gel inks that are not typically found in other non-ballpoint inks.  相似文献   
972.
The pathomorphology of intoxication of alcohol surrogates is described. A high frequency rate of DIC-syndrome is shown for the condition. A majority of thrombi accumulates at places with the highest concentrations of toxic substances as well as at those places, through which poisoning substances are brought out of the body, i.e. in the liver (since toxic substances are introduced perorally) and kidneys. Thrombi were detected in all internals, including the brain, in lethal intoxication. The immediate toxic effect from methanol and from higher spirits can matter in the genesis of changes, including acute swelling and chromatolysis with subsequent cell death. Exclusively cerebral or coagulopathic-cerebral types of thanatogenesis were registered in studied case of intoxication.  相似文献   
973.
Polymorphism of mDNA D-loop central region (CR), positions 16366-0072) was studied versus hypervariable sections (HVS1), positions 16024-16365, and HVS2, positions 00073-00340, for a sample of 71 residents of the Russian Federation. Ten polymorphic positions with 56 nucleotide substitutions, 55 of which are transitions, were detect in the CR section; no insertions or deletions were found there. It was proven as possible to use the mDNA CR locus as an additional identification marker in the forensic-expert of the mDNA control region. The probability of random coincidence (RC) of haplotypes in joint typing of HVS1, HVS2 and CR made 0.0208, which is 1.4-fold less versus the same parameter for haplotypes HVS1/HVS2 (RC = 0.0284).  相似文献   
974.
A healthy 31-year-old male abstinent from drug abuse during his recent incarceration developed slurred speech, a severe headache, and left-sided hemiparesis prior to his eventual death 9.5 hours after inhalation of methamphetamine. On postmortem examination, inspection of the brain revealed bilateral subarachnoid hemorrhage, with a prominent intralobar hemorrhage centered within the right frontal cerebral hemisphere. No evidence of vasculitis, infarction, intraventricular hemorrhage, or ruptured aneurysm could be observed. While this is not the first report of a methamphetamine-related stroke, this report describes the autopsy findings of an intracerebral hemorrhage secondary to methamphetamine abuse on autopsy and compares the findings and antemortem history to previously reported methamphetamine cerebral vascular deaths.  相似文献   
975.
976.
The aim of this study was to determine whether the Self-Appraisal Questionnaire (SAQ), a tool that was found to be reliable and valid for assessing violent and nonviolent recidivism and institutional adjustment for Canadian offenders, would also be valid for the same purposes with a demographically different population of North Carolina offenders. The internal consistency alphas and SAQ total and subscale scores' correlations were high. Offenders with high SAQ total scores had significantly more violent offenses, had more total number of past offenses, had higher numbers of past arrests, and had more institutional infractions than those with low SAQ scores. There were no significant differences between the responses of the African American and Caucasian offenders on the SAQ scales. These results support previous findings regarding the reliability and validity of the SAQ for assessing recidivism and institutional adjustment and suggest that the SAQ could be used with diverse populations.  相似文献   
977.
Wisconsin officials during the 1990s seemed poised to enact innovative and comprehensive health care reform. During that era, an ambitious, popular, and reform-minded governor led the state. The state had an unusually professional legislature. The state's economy was strong. Even with these advantages, however, the report card on the state's efforts is mixed. The state enacted a fairly modest set of reforms that were financed largely by the federal government and subject to extensive federal oversight. The Wisconsin story thus seems to be about the politics of incrementalism. But while critics of incrementalist politics point out that the number of uninsured continues to grow, the catalytic federalism witnessed in Wisconsin in the 1990s may well be the best model for implementing health care reform.  相似文献   
978.
A total of 137 urine samples and 46 serum samples, corresponding to 154 self-confessed designer drugs consumers in Ibiza island, were analyzed for the presence of designer drugs: amphetamine and amphetamine derivatives (methamphetamine, methylenedioxymethamphetamine (MDMA), methylenedioxyethylamphetamine (MDEA), methylenedioxyamphetamine (MDA), p-methoxymethylamphetamine (PMMA), p-methoxyamphetamine (PMA), etc.), ketamine and gamma-hydroxybutyric acid. Among this population, coming both from the forensic clinic and from the emergency room of a hospital, a total of 99 cases were found positive for some designer drug. This study shows the prevalence of methylenedioxymethamphetamine (MDMA) among designer drug users, sole or in association with other drugs. Also, the mixture of MDMA with other designer drugs, ethanol and/or cocaine is shown to be more likely to produce toxic symptoms requiring clinical attendance in a hospital emergency room. These findings along with the consumption history, the concentrations of drugs and metabolites in urine and serum and the toxicological significance for the interpretation of some MDMA metabolites such as 4-hydroxy-3-methoxymethamphetamine (HMMA) are discussed in this study.  相似文献   
979.
Value of fetal autopsy after medical termination of pregnancy   总被引:2,自引:0,他引:2  
We carried out a retrospective study of 352 medical terminations of pregnancy (MTP) carried out in a large French administrative region over two consecutive years. We analysed the indications for MTP and then compared the prenatal ultrasound diagnosis with fetal autopsy findings in order to demonstrate the value of pathological examination of the fetus in prenatal diagnosis and genetic counselling as well as the need to check by autopsy the quality of ultrasound screening. Preliminary analysis of the indication for these MTP showed that in 69.9% ultrasound screening had been carried out, revealing mainly brain abnormalities (22.2%) and heart defects generally associated with chromosomal abnormalities (32.1%). Prenatal findings were in agreement with autopsy results, showing no false-positive prenatal diagnoses. However, in 7.9% of cases in which brain abnormalities were detected, confirmation was not possible at autopsy because of tissue autolysis, showing the need for optimal conditions of expulsion. In 35.8% of cases, confirmation of the diagnosis by autopsy was not useful for management but still added to medical knowledge and demonstrated to the mother the reality of the defects. In 50.9%, the autopsy findings were decisive for genetic counselling.  相似文献   
980.
In this study, we analyzed allelic sequences of 10 novel Y-specific STR loci, DYS454, DYS510, DYS513, DYS520, DYS542, DYS544, DYS552, DYS561, DYS587 and DYS593, surveyed the distribution of haplotypes in a Chinese Han population. Extracted DNA was amplified with PCR, followed by a horizontal non-denaturing polyacrylamide gel electrophoresis with discontinuous buffer system. Purified alleles were sequenced on DNA sequencer (ABI Model 377) to verify the number of motif repeats. The number of alleles observed at each locus ranged from 3 to 8, yielding 102 haplotypes in 103 unrelated males samples. The allele diversity values for each locus ranged from 0.2099 (DYS544) to 0.7523 (DYS552). The haplotype diversity using all these loci was 0.9998. Our study revealed that they were valuable Y-specific markers for forensic applications.  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