查询词典 asymmetric

New methods for asymmetric synthesis of pinacol are reviewed, the catalytic effects and stereo- selectivity with various catalytic systems are discussed in this paper.

综述了近年来不同催化体系的不对称合成呐醇的方法，并总结了不同的催化效率和对映选择性的差异

That is one of the best results in asymmetric catalyzed pinacol coupling reaction, which indicates that the tetradentate chiral Schiff-bases with C〓 symmetry and rigid structure may be developed into practical applications.

这说明，具有C〓对称性且其核心结构具有刚性的四齿Schiff--Base是最有希望获得有实用价值的新的手性化合物。

Starting from chiral proline, pipecolinic acid, piperazine-2-carboxylic acid and 1,2-diphenyl amino alcohol, a series of structurally simple and easily prepared amides were developed as highly effective Lewis basic organocatalysts for the asymmetric reduction of imines with trichlorosilane as the reducing agent, which promoted the reduction of N-aryl imines with high yields and excellent enantioselectivities with an unprecedented substrate spectrum.

本文分别由手性脯氨酸、哌啶酸、哌嗪酸以及氨基醇出发，设计和合成了一系列结构新颖、合成简便、性能优良的酰胺类有机小分子路易斯碱催化剂，以廉价的三氯氢硅为氢源，用这些催化剂催化亚胺不对称还原，得到了非常优良的收率、对映选择性和前所未有的底物普适性。

Preparation of polyvinylidene fluoride asymmetric hollow fiber membranes was studied by introducing small molecular additives, which include nonsolvents (water, ethanol and 1-propanol) and inorganic salt.

制备聚偏氟乙烯的不对称中空纤维膜的研究，通过引入小分子添加剂，其中包括nonsolvents （水，乙醇和1 -丙醇）和无机盐。

Because of the complexity of the analysis and the ponderance damadge afterearthquake,the asymmetric-plan structures are more and more focused by the scholorsin home and abroad.

偏心结构由于其结构受力的复杂性以及震害的严重性，因此越来越受到国内外学者的关注。

Finally, our analysis can be extended in several directions, they may be: to build a model to incorporate a learning process; to introduce asymmetric predecision information for connecting decision-making with low-lowered incentives; most importantly, to examine the relation between various managerial accounting issues and low-powered incentives.

关于前者，我们认为，在管理控制会计系统的设计中，必须考虑不同的信息对不同层级人员业绩计量与评价的影响；系统设计的核心是建立一个有效的业绩计量与评价制度；对员工的激励制度的设计必须充分考虑柔性信息的作用。

Moreover, the dependencies of isotope effect on asymmetric fission and fissioning system size are also studied within the framework of a statistical model modified to include the effects of dissipation in fission by systematically investigating prescission particle evaporation of a light In isotope chain and a medium heavy Er isotope chain.

表明断前粒子发射存在一个同位素效应。进而在一个考虑了裂变过程中摩擦效应的统计模型的框架内，在In和Er这两个元素的同位素链中，考察了同位素效应与裂变碎片质量不对称性和裂变系统尺度的关系。

The asymmetric alkynylation of carbonyls is proved to be one of the most powerful procedures for organic synthetic chemistry,where the formation of one carbon-carbon bond and one chiral center of propargylic alcohol can be achieved in one step,and has attracted organic chemists\' most attentions.Plenty of works have been reported in recent years.

由于催化末端炔对羰基化合物的不对称加成在制备手性炔丙醇的同时，能够构建一个碳碳键和一个手性中心，因而该领域的研究受到了研究者的广泛关注，有大量的研究工作见报道。

This thesis mainly focuses on overcoming the substrates limition of the present catalytic systems,low catalytic efficiency,and application in total synthesis.1.Conveniently synthesized sulfonamide alcohol titanium complex has been used to catalyze the asymmetric addtition of methyl propiolate to various aromatic and aliphatic aldehydes with high enantioselectivity.

本论文即针对现有催化体系的底物局限性、催化效率低、应用研究少等展开研究：1、我们将简便合成的磺酰胺基醇配体-钛催化体系应用于催化丙炔酸甲酯对各类芳香醛及脂肪醛的不对称加成取得了理想的结果。

The sites headache were lateral or bilateral lunwem114frontotemporal and parietal, features of pain were blunt and pulsative,last for 15～30 minutes. All the patients had abnormal TCD, 11 cases had increased asymmetric cranial blood flow, 4 cases had decreased brain blood flow.

头痛主要为单侧或双侧额颞、头顶部钝痛或搏动性痛，持续15～30 min.15例患儿TCD检测全部有异常，11例颅内血管呈不对称性血流速度增快，4例血流速度减慢。

As she looked at Warrington's manly face, and dark, melancholy eyes, she had settled in her mind that he must have been the victim of an unhappy attachment.

每逢看到沃林顿那刚毅的脸，那乌黑、忧郁的眼睛，她便会相信，他一定作过不幸的爱情的受害者。

Maybe they'll disappear into a pothole.

也许他们将在壶穴里消失