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   23篇
  免费   2篇
化学   13篇
综合类   3篇
数学   4篇
物理学   5篇
  2022年   2篇
  2021年   1篇
  2017年   2篇
  2016年   1篇
  2015年   1篇
  2013年   2篇
  2011年   2篇
  2009年   2篇
  2008年   1篇
  2007年   1篇
  2005年   1篇
  2004年   1篇
  2003年   5篇
  2000年   1篇
  1998年   1篇
  1981年   1篇
排序方式: 共有25条查询结果,搜索用时 593 毫秒
1.
采用综合指数评价法对SCI、CSTPC收录论文进行定量评价与可比性研究;讨论了采用指数模型以及同一标准的计算方法,克服了指标量纲不同以及不同样本的不可比问题,为多指标系统科技文献绩效定量评价创造了条件,取得满意结果;在绩效定量评价中采用5项评价指标,不仅可以为中国高校发表的科技论文定量评价排序,而且为综合分析创造条件。  相似文献   
2.
A simple and rapid capillary electrophoresis with diode array detection method was developed for sepia ink identification in ancient graphic documents.Separation was performed in a fused-silica capillary (64.5 cm length, 50 μm i.d.). The running buffer was 20 mM sodium tetraborate solution, pH 9.2. The applied potential was 25 kV, temperature 25 °C and detection was at 220 nm. An appropriate extraction procedure was applied for the take and treatment of sample from the reference substances and ancient graphic documents. This method was successfully applied to the collection of drawings and maps from the Royal Chancellery Archives of Granada (Spain).  相似文献   
3.
4.
Calibration of measuring equipment is conducted by following some normative or applicable documents such as standards, manufacturer manuals and instructions, technical orders issued by defense organizations, or scientific papers. An accreditation body provides its recognition to the calibration laboratories by evaluating their technical competence and their compliance with the quality requirements of ISO/IEC 17025. The accreditation body must have defined criteria in order to evaluate different calibration methods which should ensure that the laboratories are performing the calibration in a technically competent manner when they are fully or even only partially based on the relevant reference documents. A discussion with different points of view about choosing the criteria, as well as the Israel Laboratory Accreditation Authority (ISRAC) policy on this issue, are presented.Presented at the 2nd International Conference on Metrology – Trends and Applications in Calibration and Testing Laboratories, November 4–6, 2003, Eilat, Israel.  相似文献   
5.
可擦笔作为一种新型书写工具,具有墨迹可擦除的特点,因此在当前的公安司法工作中,常见不法分子利用可擦笔对文件进行篡改。为保证物证的完整性,亟待建立一种无损,快速的可擦笔油墨检验方法,为寻找书写工具,确定犯罪嫌疑人提供帮助。常见可擦笔油墨可分为成膜油墨类和温变油墨类,本研究利用傅里叶变换红外光谱仪对市场收集的不同品牌、型号和颜色的30支可擦笔油墨进行检验。通过分析4 000~650 cm-1范围内的红外光谱对比不同可擦笔油墨的组成成分及不同褪色机理的可擦笔油墨差异。通过红外光谱信息发现,同品牌、同型号的可擦笔油墨成分相似,可擦笔油墨颜色对红外光谱影响较小。同时,对比擦除前后的可擦笔墨痕的红外光谱信息发现,温变类油墨在擦除后依旧有特殊化学成分残留,具备检验条件,但成膜型可擦油墨在擦除后残留成分较少,很难进行认定,这可能与成膜类油墨的微粒结构有关。此外,本研究利用主成分分析法(PCA)和热图Heatmap对可擦笔油墨650~1 500 cm-1范围内的红外光谱信息进行处理,进而对可擦笔种类进行分类研究,并建立红外光谱信息与主成分载荷(loadings)之间的联系。通过载荷图可知,前两主成分概括了几乎全部的红外光谱信息,累计贡献率在79%以上。为在实际工作中判断可擦笔来源,在30种油墨样本中随机选取5种未知可擦笔样本,与已知样本同时进行PCA分析,并制作散点图,实现对未知可擦笔油墨样品种类的判断,效果较好。实验结果表明,利用傅里叶变换红外光谱结合主成分分析法可对可擦笔油墨较好地进行分类,具有快速、无损、高灵敏度的显著优势,在保证物证的完整性的同时,提高了检验效率,为可擦笔变造文件的检验提供了一种较为理想的分析方法。  相似文献   
6.
7.
The possibility of comparing inkjet printing inks by micellar electrokinetic capillary electrophoresis (MECC) with diode array detection was studied. An analytical procedure was designed and successfully applied to discriminate between the electrophoretic profiles of inks (extracted from paper) produced by five well-known manufacturers. The separation process was conducted in a polyimide-coated fused silica capillary (ID 50 μm, 60 cm total/50 cm effective length) with +30 kV high voltage applied. Background electrolyte was used of the following optimum composition: 40 mM sodium borate buffer, 20 mM sodium dodecyl sulphate(IV) (SDS) and 10% (v/v) acetonitrile (pH 9.56). The experimental conditions were adjusted in terms of resolution and analysis time. The best results were obtained at 10 and 25 °C storage and capillary temperature, respectively, using 25 dots (ø 0.8 mm) cut from printouts as the sample and BGE diluted with water (1:99, v/v) as the injecting solution. The MECC separation of main printing ink components by the proposed method showed excellent precision - the RSD value of the migration time calculated for each of the investigated peaks did not exceed 3.3%. The optimized method was applied to group identification and differentiation of: (a) three colours of printing inks, (b) inks from different manufacturers (Hewlett-Packard, Epson, Brother, Lexmark and Canon) and (c) inks from different printer models. In all these cases, inks were successfully differentiated on the basis of position (migration time) and shape of their characteristic peaks.  相似文献   
8.
自然灾害是人地关系最为显性的自然事件.通过检索《中国基本古籍库》及《爱如生数据库·中国方志库》,整理了中国古文献记载中自然灾害导致的"死者万计"事件的发生频次,利用最小二乘法、小波分析和M-K检验等方法,分析其时空特征及发生原因.结果表明:历史时期"死者万计"事件频发,共有217a,主要类型为疫灾、饥灾、飓风、水灾.魏晋南北朝为第1个小活跃期,明清集中了总年数的60.8%,为第2个活跃期,并且秋季和夏季出现次数最多.10a频次呈极显著的波动上升趋势,最大值在1580~1589年,分为频次最少-缓慢上升-频次平缓-快速上升4个阶段,1820年发生增多突变.灾害演化过程中存在26,7和4a共3个周期.空间分布差异明显,以江苏、浙江为主的长江中下游和以河南为主的黄河中下游是2个高频中心,且各省灾害结构不同.气候的寒冷与异常、季节变化、灾害结构、人口规模、社会动荡、朝代更替等是灾害发生的主要原因.  相似文献   
9.
The questions on which judges/prosecutors apply for expertise are mostly about by whom a document was drafted/signed. In this study, a new collective strategy was constructed including a collection method, a modified-silica-based DNA isolation method, and a novel purification method on four contact traces formed on four different paper surface during writing, using PCR with AmpFlSTR®GlobalFiler™ STR kit (after experimental comparison between three different kits) and identification using CE. This collective analysis approach is more sensitive and superior to its equivalents on questioned documents in literature because quantifiable amounts of touch DNA and profiles with high loci percentages (100% on day 1, 72.72% after 1 week) were obtained up to 1 week even after the most challenging conditions of sample forming that a forensic scientist can meet; as washing hands just before drafting and using a very low pressure in a shorter time (simulating a simple contact real conditions while drafting), using no visualizing technique that damages the document. Using the strategy, four most commonly used paper types were compared, to see in which of them DNA could be recovered better. The success of this strategy was shown on the 1-day to 10-year-old real samples from a diary and some archive documents from a law office (including the mix-DNA and different ballpoint pens). Thus, it became possible to show if a person had touched the document, in high success rates up to 1 week as a secondary evidence, when primary evidences are insufficient for the detection of document fraud offenses.  相似文献   
10.
在探讨传统化学文献与网络化学化工信息之间关系的基础上,就快速、便捷地检索化学化工信息源线索,以及获得原始文献的策略与方法进行了翔实总结,为即将加入相关行业的学者与青年学子便捷或免费获取文献提供有价值的方法。  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