全文获取类型
收费全文 | 559篇 |
免费 | 38篇 |
专业分类
各国政治 | 7篇 |
工人农民 | 6篇 |
世界政治 | 1篇 |
外交国际关系 | 6篇 |
法律 | 256篇 |
中国共产党 | 16篇 |
中国政治 | 87篇 |
政治理论 | 28篇 |
综合类 | 190篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 14篇 |
2014年 | 23篇 |
2013年 | 51篇 |
2012年 | 15篇 |
2011年 | 45篇 |
2010年 | 42篇 |
2009年 | 42篇 |
2008年 | 49篇 |
2007年 | 43篇 |
2006年 | 41篇 |
2005年 | 32篇 |
2004年 | 25篇 |
2003年 | 35篇 |
2002年 | 18篇 |
2001年 | 26篇 |
2000年 | 9篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
排序方式: 共有597条查询结果,搜索用时 15 毫秒
111.
Discrimination of Geographical Origin of Asian Garlic Using Isotopic and Chemical Datasets under Stepwise Principal Component Analysis 下载免费PDF全文
Tsang‐Sen Liu Ph.D. Jhen‐Nan Lin M.S. Tsung‐Ren Peng Ph.D. 《Journal of forensic sciences》2018,63(5):1366-1373
Isotopic compositions of δ2H, δ18O, δ13C, and δ15N and concentrations of 22 trace elements from garlic samples were analyzed and processed with stepwise principal component analysis (PCA) to discriminate garlic's country of origin among Asian regions including South Korea, Vietnam, Taiwan, and China. Results indicate that there is no single trace‐element concentration or isotopic composition that can accomplish the study's purpose and the stepwise PCA approach proposed does allow for discrimination between countries on a regional basis. Sequentially, Step‐1 PCA distinguishes garlic's country of origin among Taiwanese, South Korean, and Vietnamese samples; Step‐2 PCA discriminates Chinese garlic from South Korean garlic; and Step‐3 and Step‐4 PCA, Chinese garlic from Vietnamese garlic. In model tests, countries of origin of all audit samples were correctly discriminated by stepwise PCA. Consequently, this study demonstrates that stepwise PCA as applied is a simple and effective approach to discriminating country of origin among Asian garlics. 相似文献
112.
目的对研制的二乙酰吗啡盐酸盐标准物质进行定值,并评定定值结果的不确定度。方法采用定量核磁共振法和质量平衡法进行定值;采用液质联用法用于有机物杂质的定性分析,采用电感耦合等离子质谱法、离子色谱法、顶空-气质联用法和卡尔费休滴定法测定无机阳离子、阴离子、挥发性有机溶剂残留和水分等杂质的含量。结果定量核磁共振法的纯度为95.6%,不确定度为0.13%;质量平衡法的纯度为95.3%,不确定度为0.93%。结论二乙酰吗啡盐酸盐标准物质的纯度值为95.6%,扩展不确定度为1.2%(k=2)。 相似文献
113.
114.
Fibers are a commonly encountered evidence type and fiber comparisons are routinely conducted. When the characteristics of questioned and known fibers correspond, the probative value is limited because the characteristics compared are determined by their manufacture. It would be valuable to test the hypothesis that questioned fibers originated from a specific carpet. One means of testing this is to analyze fine particles on the fibers. A procedure was developed for removing adhering particles from fibers and preparing them for scanning electron microscopy/ energy dispersive X‐ray spectrometry (SEM/EDS) analysis. The efficacy of several fluids (acetone, ethanol, hexanes, aqueous ethanol, aqueous sodium hexametaphosphate) and agitation methods (sonication and vortexing) for removing particles from fibers was evaluated. The most effective method evaluated was sonication in ethanol for 10 min. The recovered particles were filtered onto a polycarbonate filter and analyzed by automated SEM/EDS analysis to generate data on the particle assemblage. This method makes possible future research to test the within‐item and between‐item variability of particle assemblages on fibers. 相似文献
115.
Diana M. Wright Ph.D. Maureen J. Bradley Ph.D. Andria Hobbs Mehltretter M.S. 《Journal of forensic sciences》2013,58(2):358-364
Comparative analyses of 50 single‐layer white architectural paints were conducted to determine the discrimination power using standard techniques and to provide a basis for assessing significance when paints with limited features are not discriminated. Utilizing Fourier transform infrared spectroscopy (FTIR), 68 undifferentiated pairs resulted, yielding a discrimination of 94.45%. Adding stereomicroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and backscatter electron (BSE) imaging, and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), the overall discrimination was 99.35%. The study included blind verification replicates, which resulted in the only pairs without indications of physical or chemical differences. The remaining groups of undifferentiated samples contained subtle differences by at least one technique, but were considered undifferentiated for the discrimination power evaluations. This study demonstrates a high degree of discrimination of single‐layer white architectural paints using methods of analysis often encountered in forensic science laboratories. 相似文献
116.
考核模式改革是我校"教学重心转变"工作中教学模式改革的重点和核心内容之一。本文通过对《特殊痕迹检验》课程考核模式的改革与实践,提出了适应本专业学生教学练战一体化的考核模式。 相似文献
117.
道路交通事故的发生是人、车、道路等因素综合作用的结果,碰撞过程中。三者之间在极短的时间内发生了强烈的相互作用,如制动、碰撞、损伤产生等。事故发生后。根据国家GA41—2005《道路交通事故痕迹物证勘验》标准规定。交通事故现场痕迹包括路面痕迹、车体痕迹、人体痕迹、其它痕迹等勘验是确定交通事故责任和成因的主要依据。本文研究中通过对200起车外无防御能力的道路使用者(行人、自行车、三轮车、摩托车)与汽车碰撞事故现场痕迹。如人一车一道路位置。车辆的制动印痕、行驶速度、碰撞痕迹,人体致伤特点等各种客观的信息参数.寻找易于提取、利于计算分析、有助于事故重建的现场痕迹参数特点。以此建立起基于现场痕迹信息综合处理的事故再现参数体系。为后续重建交通事故碰撞过程研究提供参考依据。 相似文献
118.
Elizabeth A. McGaw Ph.D. ; David W. Szymanski Ph.D. ; Ruth Waddell Smith Ph.D. 《Journal of forensic sciences》2009,54(5):1163-1170
Abstract: With improvements in manufacturing procedures, comparing physical characteristics of paper samples may not offer sufficient discrimination among different vendors. In this work, the potential to differentiate paper samples based on trace element concentrations was investigated. Paper samples from two different vendors were microwave-digested and trace element concentrations (Mg, Al, Mn, Fe, Sr, Y, Ba, Ce, and Nd) were determined using inductively coupled plasma–mass spectrometry. Differences in concentration were assessed statistically using two-way ANOVA and Tukey's honestly significant differences test. Elemental concentrations were shown to be consistent across a single sheet as well as within a single ream of paper for each vendor. Reams from vendor A were differentiated based on Al and Ba concentration while reams from vendor B were differentiated based on Mg, Mn, and Sr concentrations. Paper was differentiated according to vendor based on significant differences in Ba, Sr, Ce, and Nd concentrations. 相似文献
119.
Yoshinori Nishiwaki M.S. Seiya Watanabe M.S. Osamu Shimoda B.S. Yasuhiro Saito B.S. Toshio Nakanishi B.S. Yasuko Terada Ph.D. Toshio Ninomiya Ph.D. Izumi Nakai Ph.D. 《Journal of forensic sciences》2009,54(3):564-570
Abstract: High‐energy synchrotron radiation x‐ray fluorescence spectrometry (SR‐XRF) utilizing 116 keV x‐rays was used to characterize titanium dioxide pigments (rutile) and automotive white paint fragments for forensic examination. The technique allowed analysis of K lines of 9 trace elements in 18 titanium dioxide pigments (rutile), and 10 trace elements in finish coat layers of seven automotive white paint fragments. High‐field strength elements (HFSE) were found to strongly reflect the origin of the titanium dioxide (TiO2) pigments, and could be used as effective parameters for discrimination and classification of the pigments and paint fragments. A pairwise comparison of the finish coat layers of seven automotive white paint fragments was performed. The trace elements in the finish coat layers detected by the high‐energy SR‐XRF were especially effective for identification. By introducing the trace element information of primer and electrocoat layers, all the automotive white paint fragments could be discriminated by this technique. 相似文献
120.
Sunlin Hu Ph.D. ; Hui Shen Ph.D. ; Songcai Wang B.S. ; Chao Fang M.D. 《Journal of forensic sciences》2009,54(6):1349-1352
Abstract: A young male was shot to death by a police officer with a Chinese Type 64 7.62 mm pistol when he was dealing with an aggravated assault arising from a traffic accident. By using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX), trace deposits on the discharged bullet and the intermediate target, i.e., a concrete telegraph pole at the scene, were identified to be from each other. The result demonstrated the bullet causing the death ricocheted from the concrete telegraph pole before striking the victim, thus indicating the incident was accidental. The case report illustrates the evidential value of trace materials derived, respectively, from discharged bullets and intermediate targets in bullet–intermediate target interaction for trajectory reconstruction. In addition, it indicates that the SEM/EDX method with its nondestructive nature, compared to other methods, may be more helpful in certain situations in determining the origins of trace evidentially valuable deposits on substrates. 相似文献