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   558篇
  免费   25篇
各国政治   37篇
工人农民   52篇
世界政治   70篇
外交国际关系   32篇
法律   269篇
中国政治   4篇
政治理论   118篇
综合类   1篇
  2023年   5篇
  2022年   3篇
  2021年   7篇
  2020年   16篇
  2019年   17篇
  2018年   17篇
  2017年   19篇
  2016年   31篇
  2015年   15篇
  2014年   9篇
  2013年   81篇
  2012年   20篇
  2011年   16篇
  2010年   13篇
  2009年   12篇
  2008年   15篇
  2007年   21篇
  2006年   19篇
  2005年   15篇
  2004年   15篇
  2003年   22篇
  2002年   24篇
  2001年   14篇
  2000年   18篇
  1999年   15篇
  1998年   18篇
  1997年   10篇
  1996年   5篇
  1995年   9篇
  1994年   6篇
  1993年   4篇
  1992年   8篇
  1991年   5篇
  1989年   10篇
  1988年   3篇
  1987年   3篇
  1986年   6篇
  1985年   9篇
  1984年   1篇
  1982年   5篇
  1981年   2篇
  1980年   2篇
  1979年   3篇
  1978年   6篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1970年   2篇
排序方式: 共有583条查询结果,搜索用时 31 毫秒
31.
Ketosis occurs in ketoacidosis or malnourishment. When either is suspected in relation to a death, it may be important to analyze for ketosis at autopsy. We encountered a case where starvation was suspected in a deceased nursing home resident, where the body had been embalmed prior to autopsy. Gas chromatography (GC) was unable to separate acetone from formaldehyde, a component of embalming fluid. The Acetest is a simple test that can detect acetone and acetoacetate in body fluids. We validated the Acetest with GC on vitreous. The Acetest and GC were consistent except at very low levels of acetone or acetoacetate. The sensitivity of the Acetest for acetoacetate in vitreous was 10 mg/dL, consistent with early starvation. Significant interference from embalming fluid did not occur. The Acetest was negative in the described case. The Acetest is a simple and useful test for the detection of ketosis in embalmed autopsies.  相似文献   
32.
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   
33.
Hair samples are useful as a matrix for drug testing because drugs can be detected in hair for longer periods than in blood or urine. The authors report a prospective comparison of the detection of cocaine and cocaethylene in routine postmortem biologic specimens to the detection of cocaine and cocaethylene in hair. The authors collected hair samples from various areas of the head in 53 autopsy cases, prepared them, and analyzed them by gas chromatography/mass spectrometry (GC/MS) for cocaine and cocaethylene. The authors compared the results of hair analysis with the results of toxicologic analysis performed on routine postmortem samples by enzyme multiplied immunoassay technique and GC/MS. Cocaine was found in either biologic fluids or in hair in 16 of 53 samples tested. Nine samples were positive for cocaine in both biologic fluids and hair. Five samples contained cocaine only in biologic fluids, and two contained cocaine only in hair. Cocaethylene was present in two cases. Drug screening of hair provides additional information in some autopsy cases, but the authors have not made hair analysis a routine practice. It may prove useful to save hair samples in all cases for later analysis if warranted by additional history or autopsy findings.  相似文献   
34.
The purpose of this article is to use the ideas of path dependency to understand why policies implemented by governments for health care in England were and are suboptimal in terms of the control of total costs, the equitable distribution of hospital services, and efficiency in delivery. We do this by relating the economic logic of achieving these objectives to the political logic of a state-hierarchical system in which ministers are accountable for the effects of policies and doctors largely decide the supply and demand of health care. The initial policy path of the National Health Service (NHS) controlled costs but lacked systems to achieve equity and efficiency in the funding of hospitals. Policies were introduced to achieve equity, but not efficiency, in the 1970s. The Thatcher government sought efficiency through a budgetary squeeze in the 1980s, which culminated in the NHS funding crisis of 1987 - 1988. The result was the policies of the NHS internal market, which promised efficiency by introducing a purchaser-provider split and a system of provider competition in which money would follow the patient. These promises justified an injection of extra funds for three years, but only a pallid model of the internal market was implemented. The Blair government abandoned the rhetoric of competition but maintained the purchaser-provider split and continued to constrain total NHS costs, which resulted in the funding crisis of 1998 - 1999. Current policies are to substantially increase spending on health care and reintroduce a system of provider competition in which money will follow the patient.  相似文献   
35.
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   
36.
This article addresses the potential role of business leadership in diverse efforts to reform health care financing: exploring managers efforts to alter health care markets in their role as large purchasers of health insurance, their potential contributions to future national policy proposals, and their involvement with community-level activities to control local health costs and quality. I argue that managers' leadership in market restructuring and community health initiatives will be difficult to reproduce in the realm of major national health policy initiatives due to constraints related to ideas, interests, and organization.  相似文献   
37.
A 29-year old female with a history of depression was found dead in a hotel room. The death scene investigation found empty pill bottles and an empty liter bottle of wine. Metaxalone, a centrally acting muscle relaxant, along with citalopram, ethanol, and chlorpheniramine were identified in the postmortem samples and quantitated by gas chromatography-mass spectrometry. The concentration of metaxalone in femoral vein blood was 39 mg/L. The heart blood concentration was 54 mg/L. Femoral vein blood concentrations of citalopram and chlorpheniramine were 0.77 mg/L and 0.04 mg/L, respectively. Ethanol levels were 0.13 g/dL in vitreous and 0.08 g/dL in heart blood. Other tissue samples were also analyzed. The authors consider the metaxalone concentrations toxic and potentially fatal. The citalopram concentrations were lower than those reported in fatal cases for this drug alone. Death was ascribed to polydrug abuse/overdose with metaxalone a major contributor. This represents the first reported case to our knowledge in which a metaxalone overdose significantly contributed to death.  相似文献   
38.
39.
40.
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