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排序方式: 共有668条查询结果,搜索用时 15 毫秒
661.
Xiao Yan WANG Yi CHEN* Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2000,11(12)
Precolumn derivatization is the most widely used means to overcome the detection problem in capillary electrophoresis. However most of the adopted reactions in carbohydrate labeling are time-consuming and not very selective, leading to lots of byproducts produced. We have thus tried to explored hydrazino-containing reagents which have been applied to TLC1,2 and HPLC2~5 with quite successfulness. Perez and Colón6 have also reported that dansylhydrazine can be used in CE-LIF of sugars. Th… 相似文献
662.
Guang Yue BAI Hai Ke YAN* Institute of Chemistry the Chinese Academy of Sciences Beijing 《中国化学快报》2000,11(12)
Gemini surfactants, as a new generation of surfactants in 1990's1, are the surfactants with two polar groups and two alkyl chains connected with a spacer. The most widely studied gemini surfactants are as follows: [CmH2m+1N (CH3)2- (CH2)S -N (CH3 )2CmH2m+1] Br2, or Cm-CS-Cm(2Br -where Cs stands for its spacer. Studies on their interesting physico chemical properties2,3 have made much progress, predicting that the repulsive interaction between the two head groups, hydrophobic interactio… 相似文献
663.
采用溶剂热法合成了超小尺寸三氟化镧(LaF3)纳米晶. 利用XRD、TEM等对其进行结构与形貌表征,结果显示制得的纳米颗粒为LaF3纳米晶,且具有高度均一的尺寸分布和良好的结晶度,颗粒尺寸为6±0.4 nm. 通过共掺杂镱铒两种稀土元素,所得材料在近红外光激发下(980 nm)可发射出明亮的绿光;发光光谱显示,在524,544,655 nm等位置有较强的发射峰. 利用聚琥珀酰亚胺高分子(PSI)对油溶性的纳米颗粒表面进行功能化修饰,将其成功转移水相. 利用叶酸对其进行进一步生物标记,可与肝癌细胞表面叶酸受体特异性识别,成功地实现了肝癌细胞上转换绿色发光成像研究. 相似文献
664.
张大方 《微电子学与计算机》1991,8(1):29-32
本文阐述了基于dBASE应用生成系统实现的基本原理,提出了辅助库技术,软件部件构造技术及智能技术,并就其实现原理、结构等进行了讨论。 相似文献
665.
Chang Sheng JIANG You Gui LI Chen JIANG Fang WANG Tian Pa YOU* Department of Chemistry Universtity of Science & Technology of China Hefei 《中国化学快报》2002,13(12)
Catalytic asymmetric cyclopropanation of diazoacetates with olefins has attracted much attention. Those catalysts containing various metals and optically active ligands have been employed for this reaction1,2. The first catalytic asymmetric cyclopropanation reaction was reported in 1966 by Nozaki et al.3. The author used the copper(II) complex 1 bearing a salicyladimine ligand as catalyst though with a low e.e. value of 6%. Aratani and his coworkers designed the copper-(Schiff-base) comp… 相似文献
666.
YE YANQIAN * 《数学年刊B辑(英文版)》1997,(3)
LIMITCYCLESANDBIFURCATIONCURVESFORTHEQUADRATICDIFFERENTIALSYSTEM(II)m=0HAVINGTHREEANTISADDLES(I)YEYANQIANAbstractAsaconti... 相似文献
667.
Yuan Hejin Zhang Yanning Yang Fuzeng* Zhou Tao** Du Zhenhua 《电子科学学刊(英文版)》2008,25(2):246-253
A novel Support Vector Machine (SVM) ensemble approach using clustering analysis is proposed. Firstly, the positive and negative training examples are clustered through subtractive clustering algorithm respectively. Then some representative examples are chosen from each of them to construct SVM components. At last, the outputs of the individual classifiers are fused through majority voting method to obtain the final decision. Comparisons of performance between the proposed method and other popular ensemble approaches, such as Bagging, Adaboost and k-fold cross validation, are carried out on synthetic and UCI datasets. The experimental results show that our method has higher classification accuracy since the example distribution information is considered during ensemble through clustering analysis. It further indicates that our method needs a much smaller size of training subsets than Bagging and Adaboost to obtain satisfactory classification accuracy. 相似文献
668.
Weinan E~* Jianfeng LU~ 《数学年刊B辑(英文版)》2007,28(6):665-676
The authors consider the simplest quantum mechanics model of solids,the tight binding model,and prove that in the continuum limit,the energy of tight binding model converges to that of the continuum elasticity model obtained using Cauchy-Born rule.The technique in this paper is based mainly on spectral perturbation theory for large matrices. 相似文献