选择性的

The selectivity to benzene and naphthalene in liquid products showed different tendency with the deactivation of catalyst.

在973K下，液体产品中苯的选择性与萘的选择性随着催化剂的失活呈现不同的变化趋势。

The Pictet-Spengler reaction of D-tryptophan methyl ester hydrochloride II-42 with piperonal II-34 in various solvents was extensively studied. The best stereoselectivity (cis/trans=99:1) was obtained using nitromethane or acetonitrile as the solvent.

我们研究了在不同溶剂中，D-色氨酸甲酯盐酸盐II-42和胡椒醛II-34发生的Pictet-Spengler反应的立体选择性，发现当分别用硝基甲烷和乙腈做溶剂时反应的立体选择性达到最高， cis：trans的比例为99： 1。

The common building block of them was synthesized by firstly glycosylation of an appropriately protected glucose with diosgenin, then introduction of a rhamnosyl residue to the 2-OH at Glu, finally freeing the 4-OH at Glu by selectively benzoylation of 6-OH.

我们先将适当保护的葡萄糖接在薯蓣甙元上，然后选择性地保护葡萄糖的 3 位羟基，在 2 位上引入一个鼠李糖，接下来选择性地保护葡萄糖的 6 位羟基，得到了上面三个皂甙的共同合成子。

The common building block of them was synthesized by firstly glycosylationof an appropriately protected glucose with diosgenin, then introduction of a rhamnosyl residue to the 2-OH at Glu, finally freeing the 4-OH at Glu by selectively benzoylation of 6-OH.

我们先将适当保护的葡萄糖接在薯蓣甙元上，然后选择性地保护葡萄糖的3位羟基，在2位上引入一个鼠李糖，接下来选择性地保护葡萄糖的6位羟基，得到了上面三个皂甙的共同合成子。

For bulk lamella-forming diblock copolymers, perpendicular lamellae and concentric lamellae spontaneously form under the neutral and strongly preferential surface, respectively. When the surface preference is relatively weak, novel structures such as parallel lamellae, helices and catenarian structures are observed.

对体相形成层状相的双嵌段共聚物，我们发现在中性孔壁下共聚物自组装形成垂直于孔壁的垂直层结构，在强选择性孔壁下形成一系列的同心层结构，而在弱选择性孔壁下形成平行于孔轴的平行层、螺旋和链节等新奇结构。

As a part of this key program from China Natural Science Foundation, this research focuses on the electrochemical reactions and oxidization products on the surfaces of jamesonite and marmatite, and on the change of their interfacial structures and their electrochemical mechanisms by various methods of thermodynamic, electrochemistry (such as Tafel, constant potential step, cycle voltammetry, AC impedance) and IR, UV spectra when the collectors, adjusting reagents act with the sulfide minerals in the flotation system so that the electrochemical conditions to float selectively the minerals can be decided.

本研究作为该国家自然科学重点基金项目的一部分，采用热力学、电化学(Tafel、循环伏安、恒电位阶跃和交流阻抗法)以及光谱等多种研究手段，集中研究了浮选体系中脆硫锑铅矿、铁闪锌矿表面的电化学反应及氧化产物，研究这两种矿物与捕收剂、调整剂相互作用时的界面结构变化及电化学机理，阐明了使药剂选择性捕收或选择性抑制这些硫化矿物的电化学条件。

Influences of reaction temperature, catalyst concentration, molar ratio of methanol to propylene oxide and reaction time on conversion of propylene oxide, yield and selectivity of propylene glycol monomethyl ether were studied.

在反应温度为120～130℃、催化剂用量为0.20%～0.30%、甲醇与环氧丙烷摩尔比为3/1～5/1的反应条件下，环氧丙烷的转化率在98％以上，丙二醇甲醚的选择性达95％，收率达93％，产品中伯醚的选择性为92％～93％。

The catalytic performance of the synthesized molecular sieves, modified by Pd or Pt, for isomerization and dehydroisomerization of n butane was investigated. Pd/SAPO 11 catalyst showed the highest selectivity in...

结果表明，载 0 3%Pd的SAPO 11分子筛催化剂具有最高的丁烷异构化选择性，而在丁烷一步异构脱氢反应中，含金属杂原子的催化剂具有更高的异丁烯选择性。

Triphenylmethyl chloride can react selectively with the 30-hydroxil group of glycyrrhetol under the catalyzing effects of three ethyl amine and dimethyl amino-pyridine.This condition of the reaction has an important value for the selective protection of 30-hydroxil group of glycyrrhetol.

三苯氯甲烷在三乙胺和二甲氨基吡啶等碱性催化下与甘草萜醇的C30-位羟基进行选择性缩合反应，此反应产率较与C3-位羟基化反应的要高，此种反应条件在甘草萜醇C30-位羟基的选择性保护中具有重要的价值。

Catalytic techniques for deep desulfurization, denitrogenation and dearomatization in production of clean gasoline and diesel fuels were reviewed, especially those for producing low-sulfur and extra-low-sulfur gasoline and diesel oil, among which technologies arousing most attention are sulfur-reducing FCC catalyst and additives, selective hydrogenation catalysts and technology, adsorptive desul-f urization of gasoline and diesel oil, biologically catalytic desulf urization of diesel oil, and selective oxid...

为面对新世纪清洁燃料生产的新机遇和新挑战，各种生产清洁燃料的催化技术正在竞相开发之中，尤其是生产低硫、超低硫汽油与柴油技术。其中，催化裂化降硫催化剂和助剂、选择性加氢处理新催化剂及工艺、汽柴油吸附脱硫、柴油生物催化脱硫和选择性氧化脱硫等新技术尤其引人注目。我国应加快清洁燃料生产催化新技术的开发研究，为生产更清洁的汽油和柴油燃料提供技术储备。

In the negative and interrogative forms, of course, this is identical to the non-emphatic forms.

。但是，在否定句或疑问句里，这种带有"do"的方法表达的效果却没有什么强调的意思。

Go down on one's knees;kneel down

屈膝跪下。。。下跪祈祷