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   567篇
  免费   27篇
各国政治   38篇
工人农民   58篇
世界政治   62篇
外交国际关系   39篇
法律   280篇
中国共产党   1篇
中国政治   6篇
政治理论   103篇
综合类   7篇
  2024年   11篇
  2023年   40篇
  2022年   4篇
  2021年   20篇
  2020年   23篇
  2019年   17篇
  2018年   24篇
  2017年   21篇
  2016年   41篇
  2015年   21篇
  2014年   16篇
  2013年   74篇
  2012年   20篇
  2011年   15篇
  2010年   13篇
  2009年   26篇
  2008年   17篇
  2007年   18篇
  2006年   17篇
  2005年   16篇
  2004年   20篇
  2003年   16篇
  2002年   25篇
  2001年   5篇
  2000年   13篇
  1999年   4篇
  1998年   11篇
  1997年   6篇
  1996年   1篇
  1995年   3篇
  1994年   3篇
  1993年   5篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   1篇
  1985年   3篇
  1984年   1篇
  1978年   3篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1970年   3篇
  1967年   1篇
  1966年   2篇
  1957年   1篇
排序方式: 共有594条查询结果,搜索用时 15 毫秒
21.
22.
23.
A sensitive analytical method was developed for quantitative analysis of delta(9)-tetrahydrocannabinol (delta(9)-THC), 11-nor-delta(9)-tetrahydrocannabinol-carboxylic acid (delta(9)-THC-COOH), cannabinol (CBN) and cannabidiol (CBD) in human hair. The identification of delta(9)-THC-COOH in hair would document Cannabis use more effectively than the detection of parent drug (delta(9)-THC) which might have come from environmental exposure. Ketamine was added to hair samples as internal standard for CBN and CBD. Ketoprofen was added to hair samples as internal standard for the other compounds. Samples were hydrolyzed with beta-glucuronidase/arylsulfatase for 2h at 40 degrees C. After cooling, samples were extracted with a liquid-liquid extraction procedure (with chloroform/isopropyl alcohol, after alkalinization, and n-hexane/ethyl acetate, after acidification), which was developed in our laboratory. The extracts were analysed before and after derivatization with pentafluoropropionic anhydride (PFPA) and pentafluoropropanol (PFPOH) using a Hewlett Packard gas chromatographer/mass spectrometer detector, in electron impact mode (GC/MS-EI). Derivatized delta(9)-THC-COOH was also analysed using a Hewlett Packard gas chromatographer/mass spectrometer detector, in negative ion chemical ionization mode (GC/MS-NCI) using methane as the reagent gas. Responses were linear ranging from 0.10 to 5.00 ng/mg hair for delta(9)-THC and CBN, 0.10-10.00 ng/mg hair for CBD, 0.01-5.00 ng/mg for delta(9)-THC-COOH (r(2)>0.99). The intra-assay precisions ranged from <0.01 to 12.40%. Extraction recoveries ranged from 80.9 to 104.0% for delta(9)-THC, 85.9-100.0% for delta(9)-THC-COOH, 76.7-95.8% for CBN and 71.0-94.0% for CBD. The analytical method was applied to 87 human hair samples, obtained from individuals who testified in court of having committed drug related crimes. Quantification of delta(9)-THC-COOH using GC/MS-NCI was found to be more convenient than GC/MS-EI. The latter may give rise to false negatives due to the detection limit.  相似文献   
24.
Behaviors developed in adolescence influence health later in life. The purpose of this study was to investigate the frequency of health care provider's discussion of health behaviors with overweight and non-overweight adolescents and identify demographic and health behaviors related to exercise, hours of television viewing, and weight issues associated with these discussions. A Cross sectional survey of urban adolescents was conducted. Trained interviewers administered surveys over a three month period in 2001 at an urban academic pediatric and adolescent clinic. The 252 adolescents surveyed had a mean age of 15 with 49% categorized as being at risk for overweight/overweight and 51% as normal weight using the CDC percentiles for BMI. While 16% of the adolescents reported that their physician or nurse discussed the amount of television they watched, rates of discussion related to exercise (58%), and weight (54%) were much higher. In multivariate analyses, health care provider discussions with adolescents regarding exercise were more common for overweight (O.R.=2.42, 95% C.I. [1.28–4.57]) and at risk for overweight (O.R.=1.98, 95% C.I. [1.03–3.81]) adolescents, whereas physician discussion of television viewing was not associated with weight. Discussions of weight were more common for female (O.R.=2.18, 95% C.I. [1.21–3.95]), African-American (O.R.=2.53, 95% C.I. [1.40–4.57]), and overweight (O.R.=3.92, 95% C.I. [1.97–7.81]) adolescents. Even after adjusting for weight, race and gender strongly influenced the frequency of discussions about weight in physician offices. Although health care providers frequently address weight and exercise with adolescents, more discussions related to sedentary behaviors such as television viewing may be warranted to address adolescent obesity.Received PhD in Epidemiology from University of California, San Diego. Research interests include smoking prevention and cessation among adolescents and health promotion interventions.Received MD from University of Missouri-Kansas City and MPH from Johns Hopkins University. Research interests include health services research and research in support of measurable, systematic improvements in the quality of medical care.Received medical degree from Christian Medical College, Punjab, India and Master of Public Health from University of Kansas School of Medicine. Research interests include diet and physical activity behaviors, role of the environment in obesity and obesity prevention, especially among children and adolescents.Received MBBS from Allama Iqbal Medical College, Punjab University, Lahore, Pakistan and MPH from University of Kansas Medical Center. Research interests include smoking cessation, database design, implementation, data management and analysis, and use of information technology in health care settings.Director, Cancer Prevention, Control, and Population Sciences, Kansas Cancer Institute. Received MD/MPH from Tulane University and MS from Harvard School of Public Health. Research interests include disparities in healthcare; smoking cessation among underserved populations, specifically African Americans; diet, nutrition, obesity, and physical activity.  相似文献   
25.
26.
ABSTRACT

Incremental democratic decline is evident in Bosnia and Herzegovina (BiH), but measures of democracy conceal an uneven subnational distribution of autocratization. So far there has been limited research on the drivers and constraints to subnational autocratization. This paper aims to contribute to the literature on power-sharing by exploring instances of illiberal politics enacted by parties in government at the subnational level in BiH. Evidence is gathered through semi-structured interviews and analysis of three specific cases of illiberal politics. We find that the political contest in BiH is purposefully contained within ethnic and subnational boundaries and constrained through several layers of institutionalized multilevel and ethnic checks and balances. The main drivers of subnational autocratization are opportunities that arise from the institutional framework established during early democratization and postwar structures that blend executive dominance with economic power and informal party networks, and occasionally from an individual actor’s perceptions of threat. Democratization in BiH will need to address subnational politics and deep-rooted power structures if it is to be successful.  相似文献   
27.
ABSTRACT

Democracy is backsliding throughout Southeast Europe but there are no signs of full democratic breakdown. Instead, political parties and their leaders incrementally undermine challenges to governmental authority while keeping electoral contest largely intact. This article introduces a special issue that aims to examine and explain democratic decline by looking at the prevalence of illiberal politics across countries and issues. In order to overcome the limitations of fixed regime classification we adopt a procedural lens and look into governing practices that gradually tilt the electoral playing field. Utilizing the concept of Illiberal politics allows us to examine sets of policies enacted by political parties in government with the aim to remain in power indefinitely. By tracing democratic decline in Serbia, North Macedonia, Montenegro, Bosnia and Herzegovina, Kosovo, Albania, and Croatia we observe different patterns of weakness, but also common causes arising from weak institutions and inherited governance practices that preserve executive dominance, patronage, and informality.  相似文献   
28.
The first aim of this study was to examine the structure of externalizing and internalizing problem behavior during early adolescence. Our second aim was to determine the stability of these problems for boys and for girls over time. A total of 650, 13–14-year-olds filled out (an expanded version of) the Youth Self-Report [YSR; Manual for the Youth Self-Report and 1991 Profile. Department of Psychiatry, University of Vermont, Burlington] 2 times with a 1-year interval. By using confirmatory factor analyses (CFA) to test a series of competing models, a hierarchical model provided the best representation of the structure of problem behavior at both Time 1 and Time 2: externalizing and internalizing problem behavior represent distinct aspects but the model also demonstrates the existence of comorbidity at a higher level. This model appeared to be stable over time for both boys and girls. The relative stability of problem behavior was found to be high for boys and girls. Absolute stability for both externalizing and internalizing problems appeared to be higher for boys scoring in the lower range of problem behavior. Senior Researcher, Utrecht University, The Netherlands. Received PhD in social sciences, University of Amsterdam. Major research interests include problem behavior, family relations, and peer relations during adolescence. Full Professor, Utrecht University, The Netherlands. Received PhD in social sciences: child and family studies, from University of Nijmegen. Major research interests include adolescent social development, problem behavior, and family relations during adolescence. Assistant Professor, University of Amsterdam, The Netherlands. Received PhD in psychology, University of Amsterdam. Major research interests include family influence on childhood illness and problem behavior.  相似文献   
29.
A qualitative and quantitative analytical method was developed and validated for the determination of 49 licit and illicit drugs in oral fluid. Small oral fluid samples, volume 1mL, were collected from volunteers using a modified Omni-Sal device and the analytes were extracted from an oral fluid/buffer mixture using a single Bond Elut Certify solid phase extraction cartridge. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) and gas chromatography-repetitive full scan mass spectrometry (GC-MS) were used in parallel to analyze the extracts for the targeted drugs. Extracts were analyzed by GC-MS in their underivatized form and as their pentafluoropropionyl derivatives. Deuterated internal standards were used for quantification of drugs of abuse by LC-MS-MS to minimize matrix effects. Methadone-d(9) and tumoxetine were used as the internal standards for quantification of non-derivatized and derivatized analytes respectively by GC-MS. Linearity was demonstrated over the range 5-200 ng/mL and limits of detection were less than 4 ng/mL for each drug analyzed. The method demonstrated acceptable recoveries for most of the analytes and good intra- and inter-day precision. Acquisition of data by repetitive full scan GC-MS allows the addition of further analytes to the target menu.  相似文献   
30.
India is the home to five of the eight majestic big cats of the world. The three major big cats namely, lion, tiger, and leopard are listed in the Schedule I of the Indian Wildlife Protection Act, 1972. Apart from the severe loss of the habitat, these are continuously facing the danger of extinction mainly due to poaching and hunting for their body parts, which are being greatly valued by apothecaries marketing traditional Chinese medicines. With the advent of polymerase chain reaction (PCR), DNA-based markers have emerged as major tools in the arena of wildlife forensics. Microsatellites (short tandem repeats, STRs) are markers of choice because of their polymorphic and co-dominant nature. These strictly follow the Mendelian inheritance and are highly reproducible. We have identified a new microsatellite (STR) locus Ple 46, which shows amplification in a species-specific manner (size of STR) in all the members of the family felidae studied here. This PCR-based, non-invasive method opens a new avenue to forensic identification of big cats.  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