查询词典 a chemical element

The less the oxygen content and the more content of N element in the form of pyrrole-N were observed under stronger microwave power radiation. It was affirmed that the desulfurization capability of activated carbon could be greatly increased by microwave modification. According to the analysis on surface physical and chemical characteristics, a mechanism was concluded: Modified by microwave, functional groups begin to dissociate, alkalescency is enhanced, and surface oxygen content is reduced; the amount of active sites produced by dissociation of oxygen-containing groups increased, so did the pyrrole-N groups. Apparently, the activated energy of SO〓 adsorption decreased.

通过比较微波改性活性炭前后的吸附脱硫能力，结合它们的表面物理和化学性质的变化分析，确认微波改性活性炭的脱硫性能有显著提高，其作用机理在于微波处理后，活性炭表面微观形貌发生了较大的变化，化学基团发生分解，碱性特征增强，表面含氧量减少，以CO形式释出的含氧官能团分解后产生的活性部位和吡咯氮官能团数量增加，吸附SO〓的表观活化能降低。

The individual chemical property of the element made it a good catalyst.

这种元素的特殊化学特性使其成为一种好的催化剂。

Lanthanides belong to the sixth cycle of the periodic table Ⅲ B family, are all solid metal, they are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, holmium, erbium, thulium, ytterbium, and lutetium were 15 kinds of metals and their periphery are two layers of electronic 5d16s2, while the peripheral third layer f orbital but never zero to 14, so the external electronic structure of 4f0-145d16s2, and therefore these elements in oxidation number are to 3, very close chemical properties, extraction, when it is difficult to separate them they are mostly multi-element mineral mix, more difficult to increase refining, and their atomic number of 57-71, one by one to increase the number of protons the nucleus, and thus extranuclear electron of gravity is also growing, so that atomic radius decreases with increasing atomic number Z, which makes lanthanides contraction, ionic radius is also reduced, which also makes Zr, Hf, Nb and Ta, Mo and W, the atom and ionic radius very close to each other they also determine a similar nature, resulting in difficult separation, also the tribe Ⅷ of the fifth cycle, ruthenium, rhodium, palladium, and the sixth cycle, osmium, iridium, platinum is very similar in nature, thus The six elements, said platinum group elements.

镧系元素属于周期表第六周期中ⅢB族，全部是固体金属，它们是镧、铈、镨、钕、钷、钐、铕、钆、铽、镝、钬、铒、铥、镱和镥共十五种金属元素，它们的外围两层的电子均是5d16s2，而外围第三层的f轨道电子却从零增加到14个，所以外围电子结构为4f0－145d16s2，而使这些元素氧化数均为＋3，化学性质极为接近，提炼时很难分开，它们的矿石又大多是多种元素混在一起的，更增加提纯难度，它们的原子序数为57－71，核内质子数逐个增加，因而对核外电子引力也不断增强，使原子半径随原子序数Z增加而减小，这就使镧系元素收缩、离子半径也缩小，这也使得Zr和Hf，Nb和Ta、Mo和W等原子和离子半径都很接近、也决定了它们彼此性质类似，以致难以分离、也使第Ⅷ族中第五周期的钌、铑、钯和第六周期的锇、铱、铂在性质上极为相似，因而称这六个元素为铂系元素。

The most parts of thesis as follows:1. Five symmetrical intra-molecular charge transfer oligomeric phenylene vinylene light emitting materials were designed and synthesized using oligomeric phenylene vinylene as a framework.2. The structures of target molecule were characterized by ~1HNMR,~(13)CNMR, IR, MS and element analysis.3. In order to study the influence of the location and numbers of electron-donor and electron-acceptor on their photoelectric performance by changing length of OPV chain, the UV spectra and fluorescence spectra of target compounds has been compared. We have researched into main factors effecting on material emitting red-shift; organic electroluminescence device was prepared using the compound P4. The capability of eletroluminescence was researched.4. The photoelectric properties of P4 was explained by quantum chemical calculation (the Gaussian 98 quantum chemistry program). It is greatly contributed know the whole process of charge transfer to guide the design of red emitters.

本文研究的内容主要包括以下部分：(1)设计并合成5个对称的以齐聚苯乙烯类为骨架的分子内电荷转移型齐聚苯乙烯类发光材料；(2)通过IR，MS，~1H-NMR，~(13)C-NMR和元素分析对所合成的目标化合物进行表征；(3)通过对目标化合物的紫外光谱和荧光光谱比较分析，研究改变OPV的长度，电子给体和电子受体的位置及数量对其光电性能的影响，探讨材料发射红移的主要因素；选取性能良好的目标化合物P4制备成OELD器件，对其电致发光性能进行研究；(4)运用Gaussian98量子化学程序包，采用量子化学方法对目标化合物P4的光电性能从理论加以解释，进一步认识荷移跃迁的整个过程，为红光材料的设计加以指导。

Forest bridge of Lin Jie of director of clinical poison division emphasizes hospital of buccal ancient Chinese name for Venus, the chemical drug that causes cancer " get together chloridize is aluminous " it is element of noxiousness of a kind of nerve, although noxiousness is not strong, but the contact is too much and absolutely bad,"In the circumstance that harm cranial nerve appears in mouse experiment."

林口长庚医院临床毒物科主任林杰梁强调，致癌的化学药剂&聚氯化铝&是一种神经毒性分子，虽然毒性不强，但接触太多绝对不好，&在小老鼠实验中就出现伤害脑神经的情况。&

X-ray photoelectron spectroscopy was used to investigate the content and chemical valence of chromium element,and the content of compounds in chromate passive film formed on commercial tinplate via a cathodic electrolytical treatment.

用X射线光电子能谱(X-ray photoelectron spectroscopy，XPS)分析的方法，对铬酸盐钝化镀锡钢板的正常表面及缺陷点处铬元素的含量、价态以及由铬元素组成的化合物进行了研究。

A new exothermal model of cement hydration in concrete considering the effects of temperature and concentration of chemical reactant is incorporated into the finite element numerical simulations.

基于考虑温度和化学反应物浓度对化学反应速率影响的混凝土水泥水化反应放热模型，编制二维混凝土水化热温度场有限元分析程序。

By the 1930s, the scientists finally separated "ketohexose" from cabbages and lemon juice, comprehended its chemical structures, and recognized that it was an important element of Vitamin C. Therefore, the people then called lemon a mysterious medicinal fruit.

到了30年代，人们终于从肾上腺皮质、包心菜、柠檬汁中分离出&已糖醛酸&，弄清了它的化学结构，并确定它是抗坏血酸的要素，因此人们称它为&神秘的药果&。

With Yangtze delta tidal flat as an example, through the analysis on the magnetic characteristics of tidal flat sediment and the study on the space distribution of heavy metal elements, this thesis discussed the impact to Shanghai sea bank brought by heavy intensity development, and the interrelation between sediment power effect and heavy metal pollution space distribution. Utilizing the advantage of artificial intelligence neural network, in conjunction with environmental chemical analysis, from the angle of view of sediment magnetic characteristics, it analyzed the connection mechanism between magnetic mines and heavy metal element within tidal sediments, and built a quantitative magnetical diagnosis model, in attempt to calculating the tidal heavy metal pollution status from the magnetic measurement data of sediments and assess it's impact to the environment.

中文题名长江口潮滩重金属污染的磁诊断模型研究副题名外文题名论文作者许羽导师俞立中教授学科专业自然地理学研究领域\研究方向资源与环境信息系统学位级别博士学位授予单位华东师范大学学位授予日期2001 论文页码总数111页关键词长江口潮滩沉积物环境磁学重金属污染馆藏号BSLW /2001 /X145 /11 本文以长江口南岸潮滩为例，通过对潮滩沉积物磁性特征的分析、重金属元素空间分布的研究，探讨了上海滨岸带高强度开发对潮滩环境质量的影响，以及沉积动力作用与重金属污染空间分布格局的联系。

The ICP-MS method has a potential for on-line chemical analysis of aerosol particles containing refractory metal and transuranium element.

ICP-MS在环境气溶胶在线快速分析，尤其是气溶胶粒子中难熔金属和超铀元素超痕量在线环境监测方面具有潜在的应用前景。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。