共查询到20条相似文献，搜索用时 437 毫秒
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以乙酰乙酸乙酯为原料,经肟化、溴化、环合反应制得（Z）-2（2-氨基-4噻唑）-2羟亚胺基乙酸乙酯（去甲氨噻肟酸乙酯）.经实验确定了最佳反应条件：5℃以下肟化、40℃溴化、25℃以下环合,各步中间体经萃取分液,收率可达54%. 相似文献
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袁先友 《零陵师范高等专科学校学报》2001,22(3):4-6
研究了以1－十八醇和丙二酸二乙酯为原料合成二正十八烷基丙二酸二乙酯，然后用LiAlH4还原得到2，2－二正十八烷基－1，3－丙二醇，再对甲苯磺酸催化与β-溴丙醛缩合得5，5－二正十八烷基－2－－（2－溴乙基）－1，30－二氧六环，并对产物的重结晶条件进行了研究，产物经元素分析，IR和1HNMR光谱表征。 相似文献
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抗肿瘤药物——甲砜霉素同型物的合成(Ⅴ) 总被引：2，自引：0，他引：2
选用l-β-对-甲砜基苯丝氨酸乙酯为载体与植物生长控制剂作用合成了6个新的化合物:l-α-(2,3,5-三氯苯甲酰氨基)-β-(对-甲砜基苯基)丙酸乙酯(Ⅰ),l-α(α’-萘乙酰氨基)-β-(对-甲砜基苯基)丙酸乙酯(Ⅱ),l-α-(β’-萘氧乙酰氨基∫-β-(对-甲砜基苯基)丙酸乙酯(Ⅲ),l-α-(4-氯苯氧乙酰氨基)-β-(对-甲砜基苯基)丙酸乙酯(Ⅳ),l-α-(2,4-二氯苯氧乙酰氨基)-β-(对-甲砜基苯基)丙酸乙酯(Ⅴ)和l-α-(2,4,5-三氯苯氧乙酰氨基)-β-(对-甲砜基苯基)丙酸乙酯(Ⅵ)。试验表明:化合物(浓度100μg/ml)对体外培养的人体子宫颈癌细胞(HeLa细胞)的抑制率,Ⅲ为53.9％,Ⅵ为70.5％,其余不明显。 相似文献
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王玉环 《石家庄职业技术学院学报》2009,21(2):33-35
头孢他啶侧链酸在碱性条件下与DM缩合生成头孢他啶侧链酸活性硫酯时,用价格低廉的亚磷酸三乙酯代替价格昂贵的三苯基膦,通过设计正交实验优选出的较佳反应条件为：固定头孢他啶侧链酸19．8g,反应物料n（头孢他啶侧链酸）：n（DM）：n（亚磷酸三乙酯）：n（三乙胺）=1：1．2：1．2：1．2,反应溶剂乙腈150mL,于5℃反应5h,收率86．8％． 相似文献
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袁先友 《湖南科技学院学报》2001,22(3):4-6
研究了以1-十八醇和丙二酸二乙酯为原料合成二正十八烷基丙二酸二乙酯,然后用LiAlH4还原得到2,2-二正十八烷基-1,3-丙二醇,再在对甲苯磺酸催化下与β-溴丙醛缩合得5,5-二正十八烷基-2-(2-溴乙基)-1,3-二氧六环.并对产物的重结晶条件进行了研究,产物经元素分析、IR和1HNMR光谱表征. 相似文献
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以9-芴酮和乙二醇苯醚为原料,以浓硫酸为催化剂、β-巯基丙酸为助催化剂合成了9,9-二[4-（2-羟乙氧基）苯基]芴（BHEPF）,并对其结构进行了表征和确认。探讨了合成过程中反应温度、9-芴酮和乙二醇苯醚的摩尔比、反应时间、催化剂浓硫酸的用量及助催化剂β-巯基丙酸的用量对BHEPF收率的影响,得出了其最适宜的工艺条件,在该条件下,BHEPF的收率为75%。 相似文献
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苯乙酸乙酯与金属钠反应所生成的碳负离子与碳酸二乙酯反应生成苯基丙二酸二乙酯,经四氢化铝锂还原、酸化得到2-苯基-1,3-丙二醇.通过四溴化碳/三苯基膦、硫代乙酸钾的羟基官能团转化反应,合成2-苯基-1,3-二溴丙烷和2-苯基-1,3-丙二硫醇乙酸酯,最后用肼还原硫醇乙酸酯,合成了目标产物2-苯基-1,3-丙二硫醇.所有中间产物和目标产物经核磁共振氢谱或红处光谱表征. 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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陈美曦 《山东教育学院学报》2008,23(2):103-107
Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language. 相似文献
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Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献