全文获取类型
收费全文 | 297篇 |
免费 | 86篇 |
专业分类
外交国际关系 | 9篇 |
法律 | 277篇 |
中国政治 | 1篇 |
综合类 | 96篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2017年 | 13篇 |
2016年 | 12篇 |
2015年 | 20篇 |
2014年 | 19篇 |
2013年 | 25篇 |
2012年 | 30篇 |
2011年 | 25篇 |
2010年 | 19篇 |
2009年 | 12篇 |
2008年 | 24篇 |
2007年 | 26篇 |
2006年 | 18篇 |
2005年 | 17篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
排序方式: 共有383条查询结果,搜索用时 78 毫秒
101.
目的:提取并测定芦根中甾族化合物的成分和相对含量。方法:采用气相色谱.飞行时间质谱法进行测定分析。结果:芦根提取物中含有4种甾体化合物。结论:该鉴定方法对药物成分的结构分析和临床用药具有指导意义。 相似文献
102.
103.
目的建立液相微萃取与气相色谱联用技术快速分析尿液中三唑仑的方法。方法本方法考察了萃取溶剂、体积、萃取时间、萃取振荡速度等条件对液相微萃取的影响,优化的实验条件为:萃取溶剂为0.5ml三氯甲烷,萃取时间25min,振荡速度200r/min。结果采用本文所建立的方法,三唑仑回收率为88.0%~90.5%。结论实验结果表明该方法简便、快速、灵敏、消耗有机溶剂少,是尿液中三唑仑检测的一种有效方法。 相似文献
104.
105.
Forensic Investigation of Formaldehyde in Illicit Products for Hair Treatment by DAD‐HPLC: A Case Study
下载免费PDF全文
![点击此处可从《Journal of forensic sciences》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Erica N. Oiye M.S. Maria Fernanda M. Ribeiro M.S. Leonardo L. Okumura Ph.D. Adelir A. Saczk Ph.D. Pietro Ciancaglini Ph.D. Marcelo F. de Oliveira Ph.D. 《Journal of forensic sciences》2016,61(4):1122-1125
The illegal use of formalin (commercial formaldehyde) in cosmetic products harms the health of individuals exposed to this substance. Over the last years, the commercial availability of these products, especially those containing irregular dosage of formaldehyde, has increased in Brazil. This work analyzes some products for hair treatment available in the Brazilian market and verifies their safety. The adopted analytical methodology involved sample derivatization with 2,4‐dinitrophenylhydrazine, followed by high‐performance liquid chromatography with ultraviolet detection (UV–VIS) at λ = 365 nm. The limit of quantification is 2.5 × 10?3% w/w, and the recovery tests were around 93%. Some of the samples contained high and illegal formaldehyde levels ranging from 9% to 19% (w/w) and others presented suitable concentrations of the analyte. On the basis of the results, this work discusses the efficiency and practicality of this analytical method for forensic purposes. 相似文献
106.
Inhalant abuse is a serious and ever-evolving problem for our society. Inhalants are abused more commonly by teenagers and adolescents. Inhalants such as glue, paint thinners, correction fluid, and nail paint remover are easily available in the market which makes them readily abused. Out of various methods of abuse, huffing (placing a piece of cloth soaked with inhalant is placed in the mouth), bagging (placing head in a polythene bag containing inhalant), and ballooning (balloons filled with inhalant are used for inhaling vapors through the mouth) are most common. Inhalant abuse results in multiple target organ dysfunction with neuritis and brain damage due to the dissolution of the myelin sheath. In acute poisoning cases, it might cause death due to asphyxia and sudden sniffing syndrome. In such cases, various articles containing traces of inhalants could be retrieved from the scene of incidence and to detect these traces become an important facet of the investigation. However, it might be difficult due to the rapid evaporation of inhalants and the formation of reaction product species. In the present study, an attempt has been made to study the effect of three substrates (balloon, cloth, polythene) on component profiles of four paint thinners and four nail paint removers. The study suggests that although some components are retained, there is the formation of a large number of reaction product species and these must be taken into consideration before furnishing the opinion. These reaction product species might also be inhalant specific which must be further explored. 相似文献
107.
Amber R. Rose MSFS Monica Joshi PhD Marianne E. Staretz PhD Matthew Wood PhD Thomas A. Brettell PhD 《Journal of forensic sciences》2023,68(4):1148-1161
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
108.
Hongwei Qiao PhD Litao Shao BS Jie Chen PhD Shan Jiang MS Mengxiang Su PhD Peipei Liu MS Bin Di PhD 《Journal of forensic sciences》2023,68(4):1277-1285
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
109.
110.
David A. DeTata M.F.Sc. Peter A. Collins B.Sc. Allan J. McKinley Ph.D. 《Journal of forensic sciences》2013,58(2):500-507
The use of an organic solvent to extract explosive residues from hand swabs and postblast debris inevitably leads to the coextraction of unwanted materials, usually in far greater quantities than any explosive residue. In this study, the extraction efficiency of a number of solvent cleanup procedures including solid‐phase extraction (SPE), adsorbent resins such as Chromosorb‐104, and traditional materials such as silica and Florisil was calculated using a quantitative liquid chromatography–ultraviolet (LC‐UV) detection procedure. The Oasis® HLB cartridge outperformed other cleanup procedures, with analyte recoveries approaching 95%, while the Amberlite XAD‐7 procedure returned the lowest overall recoveries. The matrix rejection ability of each method was then determined using a simulated highly contaminated matrix, with the adsorbent resins showing a higher degree of matrix rejection, which is seen as a reduction in background noise in the UV chromatogram using 210 nm detection. 相似文献