排序方式: 共有514条查询结果,搜索用时 625 毫秒
71.
72.
DANG Dong-Bin JIN Ya-Nan BAI Yan ② PAN Xiao-Jing WANG Jing-Ping ② 《结构化学》2008,27(2):225-229
A dimeric chromium compound has been synthesized by hydrothermal method and characterized by IR, EPR spectra and TG-DTA technique. The title compound [Cr(aea)]2(OH)2 (aea = N-(2-aminoethyl)aspartate) crystallizes in monoclinic, space group P21/c with a = 8.9393(10), b = 6.7198(7), c = 14.6791(16) A, β = 91.0580(10)°, V= 881.63(17) A3, Z= 2, Mr = 486.34, De= 1.832 g/cm3, F(000) = 500,μ = 1.296 mm-1, R = 0.0271 and wR = 0.0756. Single-crystal X-ray structural analysis indicates that the title compound consists of two Cr(aea) units linked by two bridging hydroxyl groups. The geometry around each chromium center is approximately octahedral and completed by two hydroxyls and a quadridentate ligand which is formed when ethylenediamine reacts with maleic acid. 相似文献
73.
提出一种新的降维方法, 加权方差估计(WVE), 它包含了切片平均方差估计(SAVE)作为特例. 并且利用Bootstrap方法从WVE中 选择出最优估计, 给出了维数的选择方法. 该最优估计通常远好于已有方法, 比如切片逆回归(SIR)等. 已有的许多方法, 如SIR, SAVE等, 通常对每个 观测给予相同的权来估计中心子空间(CS). 通过引入权函数, WVE根据观测样本距中心子空间的距离, 对不同观测给予不同权重. 权函数使得WVE在很 一般或复杂的情形下有很好的表现, 比如, 回归变量的分布严重偏离椭圆对称分布. 而椭圆对称分布假设是许多方法 的基本假定, 如SIR, SAVE等. 和已有方法相比, WVE对自变量的分布不敏感. 本文建立了WVE的相合 性. 与其他方法的模拟比较表明了WVE的优点. 相似文献
74.
LI Hao-Honga CHEN Zhi-Ronga② REN Yong-Gang LI Jun-Qiana b HUANG Chang-Canga ZHAO Bina a 《结构化学》2005,(12)
1 INTRODUCTION terested in the unique effects associated with substituents at 4- and 7-positions of the phenan- The coordination chemistry of 1,l0-phenanthroline throline ring. Thus, when phenyl groups are present, and its derivatives has captured the attention of che- the absorptivities of the CT transitions are increased mists for years. The reports on biological importance[1~4], markedly due to the extension of the dipole moment supramolecular chemistry[5], electronic spectra[6], conne… 相似文献
75.
本文考虑本质位置参数分布族中,参数的Fiducial分布与后验分布的等同问题.首先讨论了如何给出Fiducial分布,分析结果表明以分布函数形式给出Fiducial分布要比密度函数形式合理,同时,证明了所给的Fiducial分布具有频率性质.然后,研究在参数受到单侧限制时,Fiducial分布与后验分布等同的问题,给出的充要条件是分布族为指数分布族,此时,先验分布是一个广义先验分布,它不能被Lebesgue测度控制.最后,证明了在参数限制在一个有限区间内时,Fiducial分布与任何先验(包括广义先验分布)下的后验分布不等同. 相似文献
76.
The title compound belongs to monoclinic,space group C2/c with a=5.2694(1),b=12.6659(4),c=19.4108(2) ,β=91.504(2)°,V=1295.06(5) 3,Z=4 and Dc=5.599 g/cm3. The structure of BaGd2(MoO4)4 contains a MoO4 tetrahedron,a distorted GdO8 polyhedron,and Ba2+ ions in a tenfold coordination. The GdO8 polyhedra are linked together through edge-sharing to give a two-dimensional Gd layer. The MoO4 tetrahedra connected to the Gd atoms are capped up and down the Gd layer through common oxygen apices,thus forming a new Gd-Mo layer. Finally,the Gd-Mo layers are held together through bridging BaO10 polyhedra to form a three-dimensional framework. Since the Ba-μ3-O bond has a large average distance of 2.888 ,this structural characteristic will result in a cleavage along the (001) plane. 相似文献
77.
本文考虑本质位置参数分布族中,参数的Fiducial分布与后验分布的等同问题.首先讨论了如何给出Fiducial分布,分析结果表明以分布函数形式给出Fiducial分布要比密度函数形式合理,同时,证明了所给的Fiducial分布具有频率性质.然后,研究在参数受到单侧限制时,Fiducial分布与后验分布等同的问题,给出的充要条件是分布族为指数分布族,此时,先验分布是一个广义先验分布,它不能被Lebesgue测度控制.最后,证明了在参数限制在一个有限区间内时,Fiducial分布与任何先验(包括广义先验分布)下的后验分布不等同. 相似文献
78.
Synthesis and Crystal Structural Characterization of a Thiosemicarbazone Derived from 4-Acylpyrazolone 总被引:1,自引:0,他引:1
LIU Guang-Feia LIU Langa HU Xina JIA Dian-Zenga② YU Kai-Beib a 《结构化学》2006,25(10):1233-1237
1 INTRODUCTION Pyrazol-5-one derivatives form an important class of organic compounds due to their structural che- mistry and biological activities as analgesic, antipy- retic, anti-inflammatory and hyperglycemic agents[1~4]. Even the simplest pyrazol-5-one derivatives like antipyrine and amidopyrine are widely used in anal- gesic medicine[5, 6]. On the other hand, thiosemicar- bazones, especially heterocyclic thiosemicarbazones, have been the subject of extensive investigations be- cause… 相似文献
79.
1 INTRODUCTION The 1,4-dihydropyridines (1,4-DHPs) are biologi- cally interesting compounds and have been developed extensively in pharmacology. 1,4-DHP derivatives are used therapeutically in the treatment of cardio- vascular disorders, especially hypertension and coro- nary heart disease such as angina pectoris, atheros- clerosis, etc. The DHPs have emerged as one of the most important classes of drugs for the treatment of gastrointestinal disease, Raynaud?s disease, pulmonary hyper… 相似文献
80.
1 INTRODUCTION Over the last decade, there has been continuous interest in cyanide-bridged lanthanide-transition me- tal complexes due to their extensive applications in preparing rare earth orthoferrites[1], chemical sensor materials[2], fluorescent ma… 相似文献