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   4544篇
  免费   166篇
各国政治   161篇
工人农民   145篇
世界政治   302篇
外交国际关系   167篇
法律   3101篇
中国共产党   2篇
中国政治   46篇
政治理论   735篇
综合类   51篇
  2023年   26篇
  2021年   33篇
  2020年   73篇
  2019年   73篇
  2018年   100篇
  2017年   115篇
  2016年   113篇
  2015年   90篇
  2014年   108篇
  2013年   379篇
  2012年   124篇
  2011年   147篇
  2010年   116篇
  2009年   115篇
  2008年   142篇
  2007年   107篇
  2006年   132篇
  2005年   128篇
  2004年   130篇
  2003年   123篇
  2002年   116篇
  2001年   209篇
  2000年   158篇
  1999年   114篇
  1998年   54篇
  1997年   50篇
  1996年   42篇
  1995年   58篇
  1994年   48篇
  1993年   57篇
  1992年   83篇
  1991年   88篇
  1990年   81篇
  1989年   70篇
  1988年   89篇
  1987年   83篇
  1986年   106篇
  1985年   109篇
  1984年   87篇
  1983年   85篇
  1982年   40篇
  1981年   37篇
  1979年   35篇
  1978年   34篇
  1975年   31篇
  1974年   49篇
  1972年   29篇
  1971年   31篇
  1970年   30篇
  1968年   32篇
排序方式: 共有4710条查询结果,搜索用时 15 毫秒
811.
812.
The conditions of doxilamine isolation from biological fluids are studied. The method of its extraction with a mixture of organic solvents in pH 9 is proposed. Identification of doxilamine with techniques of thin layer chromatography, UV-, IR-spectroscopy, chromato-mass-spectrometry, densitometry, gas-liquid chromatography is described. UV-spectrometry, gas chromatography and densitometry can be used for quantitation of doxilamine.  相似文献   
813.
814.
We report on the prevalence of self-reported depressive symptoms and associated factors among women employed in a poultry processing plant and a community comparison group of other employed women in northeastern North Carolina in the southern United States. The rural area is poor and sparsely populated with an African American majority. The largest employer of women in the area is a poultry processing plant. The goals of the analyses were 1) to evaluate whether women employed in poultry processing had a higher prevalence of depressive symptoms than other working women from the same geographic area, and 2) to evaluate factors which might be associated with depression among all of these working women, including specific characteristics of their work environment. Recruitment of participants (n=590) and data collection were by community-based staff who were also African American women. Depressive symptoms were measured using the Center for Epidemiologic Studies Depression Scale (CES-D). Work organization factors were measured with the Job Content Questionnaire (JCQ). Log-binomial regression was used to calculate crude and adjusted prevalence ratios. The prevalence of depressive symptoms, based on a CES-D measure of sixteen or more, was 47.8% among the poultry workers and 19.7% among the other working women (prevalence ratio=2.3). After adjusting for socioeconomic variables, health-related quality of life and coping style, the prevalence of depressive symptoms remained 80% higher among the poultry workers. The prevalence of symptoms was also higher among those who perceived low social support at work, hazardous work conditions, job insecurity, and high levels of isometric load. These factors were all more common among the women employed in the poultry plant. The concentration of this low-wage industry in economically depressed rural areas illuminates how class exploitation and racial discrimination may influence disparities in health among working women.  相似文献   
815.
A fatal suicidal ingestion of drugs, together with activated charcoal, is reported. The death occurred 31 hours after the self-administration. The autopsy revealed a large amount of gastric content that appeared to be a compact mass of black color. Toxicologic analyses showed the presence of toxic levels of desalkylflurazepam and trazodone; metamizole and pridinol were also detected. The obtained results supported the hypothesis of a death due to acute intoxication delayed by the self-administration of activated charcoal, which elimination was probably hindered by the action of pridinol.  相似文献   
816.
Abstract: Machinery‐related fatalities are one of the leading causes of traumatic occupational deaths. In our report, we present the case of a 40‐year‐old male who suffered a severe head trauma while working in a cut‐foam industry and died despite an early craniectomy. The radiological reconstruction of the skull based on preoperative computed tomography scans disclosed a large depressed conical fracture of the left parietal bone. The 3D‐reconstruction of the work area, combined with a fit‐matching analysis between the machinery and the depressed skull fracture allowed us to conclude that the head was crushed between the sliding bar of the cutting device and the metallic protuberance on the opposite side. The case underlines the importance of a detailed workplace investigation and of a thorough evaluation of all circumstantial, clinical, radiological, and autopsy data in the reconstruction of machinery‐related fatalities to identify any possible legal responsibilities of the worker and/or the employer.  相似文献   
817.
Abstract: In the present study, ultrastructural analysis of mitochondrial deposits (black dots within mitochondria) as a method for the detection of early acute myocardial infarction (AMI) was evaluated. In 24 patients with AMI and six controls, analysis was performed in the heart of infarcted patients and noninfarcted controls. In the infarction area in lactate dehydrogenase (LDH)‐diagnosed AMI, the percentage of positive mitochondria was significantly higher compared to corresponding heart tissue in control patients and compared to noninfarcted areas within these patients. Also in patients with a clinically diagnosed AMI but no LDH decoloration, a significant higher percentage of positive mitochondria was found in the left ventricle compared to controls and noninfarcted areas. In patients with AMI, an increase in mitochondria with deposits was found in the infarction area compared to controls and noninfarcted tissue within the same patient, suggesting that electron microscopical changes in mitochondria can be used for the diagnosis of AMI less than 3 h old.  相似文献   
818.
Abstract: Several studies have investigated frontal sinus comparison for personal identification. One study addressed the statistical reliability of correct identification using automated digital methods and resulted in a 96% accuracy rate. Missed matches with the digital methods generally involved small, less featured sinuses. This study investigates the hypothesis that human examiners may be able to more accurately identify correct matches than digital methods, even when the comparisons involve small frontal sinuses. Participants were provided two sets of 28 radiographs and were instructed to identify matching radiographs and list the radiographs that did not have a corresponding match. Overall, error rates were low, with correct associations identified at a rate of 0.983. No incorrect associations (“false positives”) were made. Correct association rates were highest among participants “experienced” examining radiographs. Results support previous assertions that frontal sinus radiographs are a reliable means of personal identification even when the frontal sinuses are small.  相似文献   
819.
A new method for the detection of caffeine in blood has been proposed based on the combination of extraction and freezing-out to eliminate the influence of sample matrix. Metrological characteristics of the method are presented. Selectivity of detection is achieved by optimal conditions of analysis by high performance liquid chromatography. The method is technically simple and cost-efficient, it ensures rapid performance of the studies.  相似文献   
820.
Archaeological remains can provide concrete cases, making it possible to develop, refine or validate medico-legal techniques.In the case of the so-called ‘Joan of Arc's relics’ (a group of bone and archaeological remains known as the ‘Bottle of Chinon’), 14 specialists analysed the samples such as a cadaver X of carbonised aspect: forensic anthropologist, medical examiners, pathologists, geneticists, radiologist, biochemists, palynologists, zoologist and archaeologist. Materials, methods and results of this study are presented here.This study aims to offer an exploitable methodology for the modern medico-legal cases of small quantities of human bones of carbonised aspect.  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