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   720篇
  免费   49篇
各国政治   13篇
工人农民   11篇
世界政治   9篇
外交国际关系   25篇
法律   424篇
中国共产党   3篇
中国政治   49篇
政治理论   13篇
综合类   222篇
  2024年   2篇
  2023年   18篇
  2022年   3篇
  2021年   14篇
  2020年   17篇
  2019年   25篇
  2018年   28篇
  2017年   24篇
  2016年   23篇
  2015年   14篇
  2014年   36篇
  2013年   64篇
  2012年   56篇
  2011年   47篇
  2010年   41篇
  2009年   47篇
  2008年   42篇
  2007年   43篇
  2006年   40篇
  2005年   43篇
  2004年   33篇
  2003年   43篇
  2002年   18篇
  2001年   13篇
  2000年   10篇
  1999年   2篇
  1998年   7篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有769条查询结果,搜索用时 0 毫秒
261.
Aminoindanes are a class of novel psychoactive substances (NPSs) that have become more prevalent over the past decade. GC–MS is often utilized for identifying seized drugs and is well regarded for its ability to separate mixtures. However, certain aminoindanes have similar mass spectral data and require specific gas chromatographic stationary phases for separation. Derivatization is an alternative method that can be applied to GC–MS to enhance chromatographic results, providing more selective analysis in seized-drug identification. This study investigates derivatization techniques to provide options for forensic science laboratories in accurately identifying aminoindanes. Three derivatization reagents, N-methyl-bis(trifluoroacetamide) (MBTFA), heptafluorobutyric anhydride (HFBA), and ethyl chloroformate (ECF) were evaluated for the analysis of eight aminoindanes by GC–MS using two common gas chromatographic stationary phases, Rxi®-5Sil MS and Rxi®-1Sil MS. All three derivatization methods successfully isolated eight aminoindanes, including the isomers 4,5-methylenedioxy-2-aminoindane (4,5-MDAI), and 5,6-methylenedioxy-2-aminoindane (5,6-MDAI) that could not be differentiated prior to derivatization. Reduced peak tailing and increased abundance were observed after derivatization for all the compounds, and mass spectra of the derivatives contained individualizing fragment ions that allowed for further characterization of the aminoindanes. This excluded 4,5-MDAI and 5,6-MDAI as they shared the same characteristic ions and were only distinguishable by their retention times. All three derivatization techniques used in this study allow for successful characterization of the aminoindanes and give forensic science laboratories flexibility in their analysis approach when they encounter these compounds.  相似文献   
262.
The evolving opioid epidemic in the United States, fueled by illicit fentanyl, has greatly increased deaths from illicit drug use. These nonnatural deaths require formal death investigation. The National Association of Medical Examiners states in its Forensic Autopsy Performance Standards that autopsy remains a necessary component for proper investigation of suspected acute overdose deaths. If a death investigation office lacks adequate resources to investigate all deaths under its jurisdiction while meeting expected standards, then that office may be forced to consider altering its protocols for investigation by changing the types of deaths investigated or the extent of its investigations. Drug death investigations take longer to complete because novel illicit drugs and mixtures of drugs complicate toxicological analyses, prolonging a family's wait for completion of a death certificate and autopsy report. Public health agencies must also wait for results, but some agencies have developed mechanisms for rapid notification of preliminary results to allow timely deployment of public health resources. The increased deaths have strained the resources of medicolegal death investigation systems throughout the United States. Given the significant workforce shortage of forensic pathologists, newly trained forensic pathologists are too few to meet the demand. Nevertheless, forensic pathologists (and all pathologists) must make time to present their work and themselves to medical students and pathology trainees to encourage an understanding of the importance of quality medicolegal death investigation and autopsy pathology and to provide a model that can encourage interest in a career in forensic pathology.  相似文献   
263.
Caffeine is the most widely consumed psychoactive agent worldwide and has the potential for abuse, but studies monitoring caffeine abuse in China are scarce. This study aims to estimate the prevalence of caffeine abuse in northwest China and investigate the correlation between caffeine and other drugs in hair and nails using an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Fingernail clippings were collected from 376 participants in northwest China to detect caffeine and 13 other illicit psychoactive drugs and their metabolites. Paired hair and nail samples were collected from 39 participants to investigate the correlation between caffeine and other drugs in hair and nails. The samples were decontaminated, pulverized, and extracted by a high-throughput nail sample preparation method and analyzed by UPLC-MS/MS. The results showed a risk of caffeine abuse in northwest China, with concentrations ranging from 0.43 to 10.6 ng/mg for healthy volunteers, 0.49–246 ng/mg for caffeine abusers, and 0.25–363 ng/mg for drug addicts in community rehabilitation centers. Caffeine was detected together with other illicit psychoactive drugs and their metabolites. Furthermore, positive detection correlations were found between hair and nail samples. This study provides a current perspective on caffeine abuse in northwest China and demonstrates the practical use of UPLC-MS/MS for the simultaneous detection of caffeine and 13 illicit psychoactive drugs and their metabolites in hair and nails. The results highlight the potential of nails as a supplementary matrix when hair samples are unavailable and emphasize the need for handling caffeine carefully given its potential for abuse.  相似文献   
264.
The opioid epidemic, impacted from the proliferation of fentanyl, has added impetus to the need to detect fentanyl, sources of fentanyl, and places where fentanyl and drugs adulterated with fentanyl are available. Many darknet marketplaces (DNMs) have rules that ban fentanyl. However, it is unclear how these affect the fentanyl market. Using the AlphaBay DNM as a case study, we conducted mixed methods qualitative research. We scraped and analyzed data from the AlphaBay I2P website using, among other methods, content and social network analysis, to uncover hidden fentanyl networks. Our research highlights the next evolution of darknet marketplaces – the migration of DNMs from Tor to I2P and the methods that can be used identify fentanyl networks, irrespective of where sites are: I2P, Tor, or multihomed on I2P and Tor. Despite its ban in the Global AlphaBay Rules, our research revealed the sale of fentanyl on the AlphaBay DNM. Unlike previous studies, our findings predominantly revealed the covert sale of fentanyl on AlphaBay and predatory vendors selling illicit drugs, which unbeknownst to buyers, contained fentanyl. To a lesser extent, our findings identified the overt sale of fentanyl patches on AlphaBay. Although we examined only one DNM, the prevalence of the covert sale of fentanyl and the presence of predatory vendors underscores the importance of research that decodes the language of vendors who surreptitiously sell fentanyl or drugs adulterated with fentanyl or other illicit substances. The results of our research can inform strategies aimed at disrupting and dismantling DNM fentanyl networks.  相似文献   
265.
The rise of fentanyl and fentanyl analogs in the drug supply pose serious threats to public health. Much of these compounds enter the United States through shipping routes. Here we provide a method for fentanyl screening and analysis that utilizes pressure-sensitive adhesive (PSA) lined paper to recover drug residues from parcel-related surfaces. The paper used is commercially available repositionable notes (also called post-it or sticky notes). From this paper, mass spectra were obtained by paper spray-mass spectrometry (PS-MS), where PSA paper served as both a sampling and analysis substrate. Seven fentanyl-related compounds were analyzed: fentanyl, 4-anilino-N-phenethylpiperidine (4-ANPP), N,1-diphenethyl-N-phenylpiperidin-4-amine (phenethyl-4-ANPP), valerylfentanyl, 4-fluoroisobutyrylfentanyl (4-FIBF), carfentanil, and p-fluorofentanyl. These compounds were recovered by PSA paper and identified by PS-MS from packaging tape and plastic at 50 ng and from cardboard and shipping labels at 100 ng. The impact of cutting agents on PS-MS analysis of fentanyl analogs was explored. No trends of analyte suppression were found at high concentrations of the cutting agents caffeine, diphenhydramine, and lidocaine when recovered from surfaces. A cartridge that required no precise cutting of PSA paper prior to sampling or analysis was evaluated for use in PS-MS for fentanyl screening. Recovery and detection of fentanyl from plastic sheeting was demonstrated with this cut-free cartridge. The cut-free cartridge showed somewhat less consistency and lower analyte signal than the standard cartridge, but performance was suitable for potential screening applications. In combining PSA surface sampling with PS-MS for drug screening, both sampling and detection of fentanyl-related compounds is simple, rapid, and low-cost.  相似文献   
266.
20世纪80年代末,海峡两岸开启互通交流之门后,大陆与台湾的毒品犯罪进入了相互渗透、相互影响的状态,尤其在两岸分别加入WTO以及开放“小三通”之后,毒品犯罪伴随着更为频繁的经贸往来和文化交流呈现增长加剧之势,给两岸的社会稳定和治安带来更大的威胁。海峡两岸警方为打击跨境毒品犯罪网络积极寻求合作的途径与方式,并取得了一定的合作成果,但由于缺少直接快速的合作通道和可循的长期合作机制,共同打击毒品犯罪行动面临困境。  相似文献   
267.
当前,海峡两岸主要通过"FT913"警务合作平台、对口联络制度、双向遣返犯罪嫌疑人和学术交流等途径对毒品犯罪进行侦査协作,使得毒品犯罪快速蔓延的趋势得到遏制,破案数量不断增加,但还面临不少困境,应建立基层毒品犯罪侦査直接协作机制,适时开展联合侦查办案,搭建情报交流平台,加强两岸警务部门高层联络等方式,以提高两岸对毒品犯罪侦查协作水平。  相似文献   
268.
TRIPS协议第39.3条首次在国际层面规定了数据保护的义务。我国是否履行了该义务的入世承诺,是中美之间重要的争议。为缓解相关的国际压力,需要构建合理的数据保护制度,梳理世界各国如何实施第39.3条具有重要的借鉴意义。从数据保护的属性来看,包括禁止占用(商业秘密)、数据专有权和市场专有权等立法模式。在具体制度上,依据TRIPS协议第39.3条,各国详细规定药品数据受保护的条件,重点界定新型化学成分与新药的关系及其范围,明确数据保护的权利内容和保护期限,构建保障公共健康的数据保护限制制度。我国应借鉴这些规定,修订《药品管理法》以完善药品数据的保护。  相似文献   
269.
Cleistanthus collinus is an extremely toxic plant poison. We report a case of suicidal ingestion of boiled water decoction of C. collinus where the patient presented with abdominal pain and giddiness. There was persistent metabolic acidosis and fluctuation in the level of serum potassium. The ECG changes indicated a probable myocardial injury with conduction abnormality. At autopsy, the viscera were found to be congested. The toxins were detected in the viscera and blood by TLC and HPLC. Cleistanthin A and B, collinusin, and diphyllin are the principal toxic constituents of the plant. Consumption of a boiled decoction of leaves is highly toxic and, medical management of patients is mainly supportive because the molecular mechanisms of toxin action are unknown. In the recent years, C. collinus has created a considerable amount of interest because of its complex metabolites and their cytotoxic activities. Through this study, the authors have tried to highlight different properties pertaining to C. collinus.  相似文献   
270.
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