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   1286篇
  免费   113篇
各国政治   15篇
工人农民   33篇
世界政治   15篇
外交国际关系   42篇
法律   700篇
中国共产党   97篇
中国政治   120篇
政治理论   42篇
综合类   335篇
  2024年   5篇
  2023年   27篇
  2022年   13篇
  2021年   16篇
  2020年   53篇
  2019年   42篇
  2018年   36篇
  2017年   37篇
  2016年   50篇
  2015年   42篇
  2014年   144篇
  2013年   171篇
  2012年   101篇
  2011年   102篇
  2010年   84篇
  2009年   91篇
  2008年   70篇
  2007年   59篇
  2006年   49篇
  2005年   48篇
  2004年   23篇
  2003年   42篇
  2002年   25篇
  2001年   27篇
  2000年   9篇
  1999年   7篇
  1998年   3篇
  1997年   2篇
  1995年   3篇
  1994年   3篇
  1992年   1篇
  1991年   1篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   2篇
  1985年   1篇
  1984年   3篇
排序方式: 共有1399条查询结果,搜索用时 15 毫秒
961.
This study involved the comparative analysis and discrimination of 90 electrical tape adhesives. The objectives included the evaluation of the ability of individual techniques to discriminate samples and the assessment of the ability of the techniques combined to distinguish samples. The techniques utilized were stereomicroscopy, Fourier transform infrared spectroscopy (FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). Stereomicroscopy, to assess adhesive colors of black, clear/colorless, and clear adhesives with brown tint, resulted in a discrimination of 53%. FTIR analysis yielded eight distinct groups with a discrimination of 67%. Py-GC/MS analysis resulted in 16 groups with a discrimination of 83%. These analyses confirmed and further subdivided the FTIR groups. SEM/EDS resulted in five separate groups at 17% discrimination, increasing the overall discrimination to above 85%.  相似文献   
962.
The organic peroxide explosive triacetone triperoxide (TATP) is regularly encountered by law enforcement agents in various stages of its production. This study utilizes solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) to examine sulfuric acid-, hydrochloric acid-, and nitric acid-catalyzed TATP syntheses during the initial 24 h of these reactions at low temperatures (5-9°C). Additionally, aging of the reaction mixtures was examined at both low and ambient temperatures (19-21°C) for a further 9 days. For each experiment, TATP could be readily identified in the headspace above the reaction mixture 1 h subsequent to the combination of reagents; at 24 h, TATP and diacetone diperoxide (DADP) were prominent. TATP degraded more rapidly than DADP. Additionally, chlorinated acetones chloroacetone and 1,1,-dichloroacetone were identified in the headspace above the hydrochloric acid-catalyzed TATP reaction mixture. These were not present when the catalyst was sulfuric acid or nitric acid.  相似文献   
963.
Abstract: A 15‐year‐old male orally consumed an unknown but fatal amount of sustained release hydromorphone. He was naïve to opioid use. No other drugs or alcohol were involved. The cause of death was acute aspiration‐related bronchopneumonia, secondary to hydromorphone ingestion; the manner of death was accidental. Hydromorphone and hydromorphone‐3‐glucuronide were quantified in postmortem fluids by tandem liquid chromatography–mass spectrometry. The hydromorphone concentrations in the peripheral blood, urine, and vitreous humor were 57, 4460, and 31 ng/mL, respectively. The hydromorphone‐3‐glucuronide concentrations in the corresponding three fluids were 459, 36,400, and 40 ng/mL. Hydromorphone‐3‐glucuronide accumulation probably did not contribute significantly to the opiate toxicity. The proposed minimum lethal hydromorphone blood concentration in the nontolerant user is in the vicinity of 60 ng/mL.  相似文献   
964.
This article describes the synthesis and identification of urinary metabolites of 4-iodo-2,5-dimethoxyphenethylamine (2C-I), a new psychoactive drug. 2C-I hydrochloride was administered orally to male Sprague-Dawley rats, and the urinary extracts were analyzed by gas chromatography/mass spectrometry (GC/MS), then five putative 2C-I metabolites were synthesized in our laboratory. In the synthetic process of the 2C-I metabolites, iodination of the aromatic ring was successfully carried out using iodine and orthoperiodic acid as the iodination reagent, and selective debenzylation of aryl benzyl ether was accomplished by the acid hydrolysis method using trifluoroacetic acid and thioanisole. The synthesized metabolites were well separated and detected by GC/MS after valeryl derivatization. The results showed that 2C-I underwent O-demethylation, N-acetylation, and deamination, followed by oxidation to the corresponding carboxylic acid in rats. The data presented in this study will be very useful for the analysis of 2C-I and its metabolites in forensic samples.  相似文献   
965.
In this study, δ13C values of six cocaine samples were identified and classified using a single quadrupole mass spectrometer and an isotope ratio mass spectrometry (IRMS) as simultaneous gas chromatography detectors. Our instrument modification is simple to use and is useful (i) when the sample is of limited size or can only be injected once, (ii) to help identify peaks in a complicated IRMS chromatogram, and (iii) to help differentiate very simple systems when impurity profiling is not possible. The EI-MS confirmed the identity of cocaine in each sample. The IRMS data distinguished 12 of the 15 possible pair-wise comparisons at the 95% CL. Three samples could not be differentiated by their δ13C ratios for cocaine. ANOVA demonstrated that the measurement variance was consistently larger than the sample variance. As the δ13C values clearly show, this technique enables the exclusion of a potential common source even when two samples have otherwise identical chemical and physical properties.  相似文献   
966.
Successful DNA-based identification of mass disaster victims depends on acquiring tissues that are not highly degraded. In this study, multiple protocols for field preservation of tissues for later DNA analysis were tested. Skin and muscle samples were collected from decaying pig carcasses. Tissues were preserved using cold storage, desiccation, or room temperature storage in preservative solutions for up to 6 months. DNA quality was assessed through amplification of successively larger segments of nuclear DNA. Solution-based storage, including a DMSO/NaCl/EDTA mixture, alcohols, and RNAlater preserved DNA of the highest quality, refrigeration was intermediate, and desiccation was least effective. Tissue type and extent of decomposition significantly affected stored DNA quality. Overall, the results indicate that any tissue preservation attempt is far superior to delaying or forgoing preservation efforts, and that simple, inexpensive methods can be highly effective in preserving DNA, thus should be initiated as quickly as possible.  相似文献   
967.
中国共产党成立90年来,带领中华民族不断从胜利走向胜利,取得了举世瞩目的成绩。这得益于党的领导集体在中国革命和社会主义事业建设实践中,始终坚持创造性地运用马克思列宁主义,走理论与实践相结合的正确道路。其中,毛泽东领导思想及其实践,为党的领导事业奠定了深厚的基础。文章深入研究了毛泽东的领导路线、领导职责、领导作风及领导方法,这对于提高新形势下党的执政能力和领导水平具有重要指导和借鉴作用。  相似文献   
968.
Designer psychostimulants are known by recreational drug users to produce a complex array of adrenergic and hallucinogenic effects. Many of these drugs are not targeted during routine toxicology testing and as a consequence, they are rarely reported. The purpose of this study was to develop a procedure for the detection of 15 psychostimulants in urine using liquid chromatography–tandem mass spectrometry (LC‐MS/MS), specifically 2,5‐dimethoxy‐4‐bromophenethylamine (2C‐B), 2,5‐dimethoxy‐4‐chlorophenethylamine (2C‐C), 2,5‐dimethoxy‐4‐methylphenethylamine (2C‐D), 2,5‐dimethoxy‐4‐ethylphenethylamine (2C‐E), 2,5‐dimethoxyphenethylamine (2C‐H), 2,5‐dimethoxy‐4‐iodophenethylamine (2C‐I), 2,5‐dimethoxy‐4‐ethylthiophenethylamine (2C‐T‐2), 2,5‐dimethoxy‐4‐isopropylthiophenethylamine (2C‐T‐4), 2,5‐dimethoxy‐4‐propylthiophenethylamine (2C‐T‐7), 2,5‐dimethoxy‐4‐bromoamphetamine (DOB), 2,5‐dimethoxy‐4‐chloroamphetamine (DOC), 2,5‐dimethoxy‐4‐ethylamphetamine (DOET), 2,5‐dimethoxy‐4‐iodoamphetamine (DOI), 2,5‐dimethoxy‐4‐methylamphetamine (DOM), and 4‐methylthioamphetamine (4‐MTA). Analytical recoveries using solid‐phase extraction were 64–92% and the limit of detection was 0.5 ng/mL for all drugs except 2C‐B (1 ng/mL). The assay was evaluated in terms of analytical recovery, precision, accuracy, linearity, matrix effect, and interferences. The technique allows for the simultaneous detection of 15 psychostimulants at sub‐ng/mL concentrations.  相似文献   
969.
A retrospective study was carried out on postmortem examination data of 131 sharp force‐related casualties recorded by the Brescia Institute of Forensic Medicine between 1982 and 2012. The objective was to identify relevant parameters that may be used to distinguish the manner of deaths between homicide, suicide, and accident. The following variables were considered: manner of death; demographic data; scene; type of sharp object; location and numbers of wounds; the presence of hesitation marks/defense wounds; toxicological findings; psychiatric history. There were 92 homicides, 28 suicides, and 11 accidents. Most victims were male, with an average age of 43. Injuries in isolation were present in 9.8% of homicides, in 35.7% of suicides, and in 54.5% of accidents. Most injuries involved the left anterior chest in homicides and the forearms in suicides. This study underlines the importance of a meticulous postmortem examination of injuries on the body and their relationship with other results from the death scene investigation.  相似文献   
970.
This article explains how and why armed, non-state actors collaborate with states to inflict massive levels of violence. Regime type and state capacity interact to provide state elites a menu of repertoires for implementing violence, some emphasizing direct state action, others emphasizing cooperation and alliance between state and armed, non-state actors. Rather than struggling in vain to build strong states to eliminate armed non-state actors and establish a monopoly over the use of force, averting genocide might necessitate recruiting and strengthening the power of indigenous, armed non-state actors.  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