选择反应

Solvent effect on the Diels-Alder reaction was analyzed with four different kinds of solvents: benzyl alcohol, cyclohexanone, toluent and decalin. The results show that the rate of the Diels-Alder reaction increased in more polar solvents and stereoselectivity of TCPD decreased.

在模拟计算基础之上，选择苯甲醇、环己酮、甲苯及十氢萘四种溶剂进行Diels-Alder反应的溶剂效应研究，考察温度、压力变化对反应速度、产物立体选择性的影响。

The Gemini phosphate surfactant was synthesized with decyl digomeric glycol and phosphatizing agent P205 by phosphatizing.

实验选择苄基三乙基氯化铵为催化剂，用量为4%，投料比为2：1，反应温度为60℃，反应时间为6时，最终产率为78.3%。

According to the structure and property of feather fibre fabric and the sizing ingredients,choosing the biological catalyst-enzyme which has high catalysis efficiency and undivided reactivity,to desize the feather fibre fabric ,the paste would be removed quickly and efficiently.

在羽毛纤维织物结构性能基础上，结合织物上所含浆料的组成，选择催化效率高、反应专一的生物催化剂酶对羽毛纤维织物进行退浆处理，可以快速、高效退除织物上的浆料，同时酶退浆时反应条件温和，不需要高温、高压、强酸、强碱的作用条件；采用超声波对羽毛纤维织物进行退浆可以缩短处理时间、降低处理温度，减少药剂用量，而处理效果优于常规法退浆。

In order to investigate the mechanism for this reac-tion, methyl α-bromoacetate or ethyl α-bromoacetate as starting material was added to the solution of phenyl selenoamide in ethanol in 1∶1 or 2∶1 molar ratio under the neutral condition at room temperature. The results indicated that the same product bis or bis diselenide was formed. Byproduct ethyl benzoate was also separated.

为了研究该反应机理，选择α-溴代乙酸甲酯或α-溴代乙酸乙酯在无催化剂、中性条件下，乙醇溶液中与苯基硒代酰胺室温下反应，投料比为1∶1和2∶1，结果也都生成了同一类产物二甲氧羰基甲基二硒醚或二乙氧羰基甲基二硒醚，同时还分离得到了相应的副产物苯甲酸乙酯。

In order to investigate the mechanism for this reaction, methyl α-bromoacetate or ethyl α-bromoacetate as starting material was added to the solution of phenyl selenoamide in ethanol in 1:1 or 2:1 molar ratio under the neutral condition at room temperature. The results indicated that the same product bis or bis diselenide was formed. Byproduct ethyl benzoate was also separated.

为了研究该反应机理，选择α-溴代乙酸甲酯或α-溴代乙酸乙酯在无催化剂、中性条件下，乙醇溶液中与苯基硒代酰胺室温下反应，投料比为1：1和2：1，结果也都生成了同一类产物二甲氧羰基甲基二硒醚或二乙氧羰基甲基二硒醚，同时还分离得到了相应的副产物苯甲酸乙酯。

Methods 55 patients were treated with pelvic cavity fourfold radiography and conventional check before iodic allergic experiment.

方法选择门诊患者55例，均行四重造影检查，检查前常规行碘过敏试验阴性52例，用复方泛影葡胺为造影剂；用非离子型碘造影剂碘海醇为造影剂，观察造影过程中患者过敏反应，分析碘过敏反应的机制。

Using the chemical reaction route selection method proposed by the authors, a reaction route of using commercial methylglyoxal as the starting material to produce Furaneol was chosen.

今采用作者提出的化学反应路径选择因子对呋喃酮的合成方法进行计算比较，确定了以丙酮醛为原料，通过偶联反应合成中间体苏式3，4-二羟基-2，5-己二酮，再由成环反应制备产物呋喃酮的合成路线。

In this paper, adopted augmenting culture in nitrite bacteria culture media and the method of silica gel plate isolation,31 strains of bacteria were isolated from vegetable garden soil of our school. The color reaction test was carried out with Griess reagent and culture fluid, which was regarded as the index to determine producing NO2- or not. 13 strains which color were deep were obtained and they were further rescreened by doing nitrite test. A strain N4(coded N4,the same to the following)with higher rate of nitrosification was picked up after rescreened; A strain B08( coded B08 ,the same to the following) with higher rate of denitrification was obtained after isolated and rejuvenated from our lab conserving mixed denitrifying bacteria culture.

本研究采用亚硝化细菌富集培养基选择培养和硅胶平板分离法，从本校农场菜园土中分离到31株细菌，以格利斯试剂对培养液的反应颜色深浅作为指标衡量其产NO_2~-的多少，经初筛从分离株中筛选出13株格利斯试剂反应颜色较深的菌株，再对这13株菌作亚硝化试验，最终选出一株亚硝化速率较高的菌株(编号为N_4，下同)；另外，通过对本实验室保存的反硝化细菌混合菌液进行分离复壮，筛选出一株反硝化速率高的菌株编号为B_

Olefine, electrophilic or nucleophilic substitution of arenes, nucleophilic addition of carbonyl compounds stereochemistry in elimination reaction of double bond forming and the choosing of oxidants and reducing agents in redox system.

在化学反应方面重点是烯烃的亲电加成，芳香烃的亲电，亲核取代，羰基化合物的亲核加成，消除反应的双键定位和立体化学，氧化，还原反应中氧化还原剂的选择。

Secondly, some problems can be found while analyzing commuters' commute psychology, such as information oversaturation, commuter overreaction and concentration, which are discussed in detail.

其次，对交通信息诱导系统中交通信息对出行选择的影响进行分析，认为在诱导出行者的出行时，存在信息过剩、过激反应和集聚反应等问题。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。