共查询到20条相似文献，搜索用时 78 毫秒
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乙醇提取八角茴香油工艺的研究 总被引：18，自引：0，他引：18
研究了用95％乙醇提取八角茴香油的最佳工艺条件，比较了索氏（热回流）提取法与冷浸取法的效果。索氏提取法最佳工艺条件是：料剂比（g/ml）为15：100回流4h；冷浸取法料剂比（g/ml）为5：100，室温浸泡4d，两均不必调pH值。用重量法测蜡和胶体的含量，用傅立叶变换红外光谱仪鉴定其成分。发现索氏提取法周期短，效率较高，产品杂质较少，由此可见，索氏提取法优于冷浸取法。 相似文献
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水飞蓟中总黄酮提取工艺的研究 总被引：1，自引：0，他引：1
研究了热回流法、索氏提取法和超声波提取法的水飞蓟中总黄酮类化合物的提取工艺，并使用正交实验确定了最佳提取条件．结果表明最佳提取条件为：样品量322．8g，试剂用量330mL，浸泡时间27．8h提取温度0℃，提取时间1．13h． 相似文献
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目的:比较醋炙元胡不同提取方法中延胡索乙素的溶出差异.方法:采用连续回流提取、常规水煮、微波提取、渗漉、温浸提取等方法提取醋炙元胡中的生物碱,结合RP-HPLC对其进行含量分析.色谱柱Agilent TC-C18柱(250×4.6mm,5μm),流动相为甲醇:0.3%三乙胺(冰醋酸调p H至6.50)55:45,流速为1.0ml/min,检测波长为280nm,柱温为30℃.结果:结果表明,连续回流提取法提取率最高,提得延胡索乙素0.047%,常规水煮法提取率最低,提得延胡索乙素0.013%.其在10~50μg/ml范围内线性关系良好.结论:不同提取方法对醋炙元胡中延胡索乙素的提取率差异很大,为了使药材得到充分利用,选择连续回流提取法提取效果更好. 相似文献
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比较了“茶叶中咖啡因的提取”实验的三种方法，采用了用恒压滴液漏斗代替索氏提取器，实现平衡状态下的连续萃取，追求最佳萃取效果的新方法，比较了间歇萃取与连续萃取实验结果，总结了本实验的成败关键，从“绿色化学”的角度提出了“茶叶中咖啡因的提取”实验方法的选用条件。 相似文献
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从茶叶中提取咖啡因实验方法及装置的改进 总被引：1，自引：0，他引：1
"从茶叶中提取咖啡因"实验是有机化学中的一个重要实验。作者在教学中对原装置及操作方法进行了改进,用恒压滴液漏斗代替索氏提取器,实现了平衡状态下的连续萃取,提高了提取效率,缩短了实验时间。 相似文献
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研究灵芝益寿胶囊(LZYSJN)的渗漉和水提取方法,优化其生产工艺,为指导生产提供依据。采用正交试验对灵芝益寿胶囊中的灵芝、制何首乌、人参、五味子渗漉工艺和灵芝水提取工艺进行优化。结果表明:(1)灵芝渗漉以灵芝粗粉加6倍量乙醇,浸渍48 h,渗漉速度为5 mL/min为最佳工艺;(2)灵芝水提取以灵芝药渣加水8倍量,提取两次,每次2 h为最佳工艺;(3)制何首乌渗漉以制何首乌粗粉加8倍量乙醇,浸渍48 h,渗漉速度为3 mL/min为最佳工艺;(4)人参渗漉以人参粗粉加8倍量乙醇,浸渍48 h,渗漉速度为5mL/min为最佳工艺;(5)五味子渗漉以五味子粗粉加6倍量乙醇,浸渍48 h,渗漉速度为5mL/min为最佳工艺。灵芝益寿胶囊提取工艺的优化能够降低成本,提高产品质量。 相似文献
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研究荞麦蜂花粉总黄酮类物质的提取工艺,以芦丁为对照品用吸光光度法测定总黄酮含量;比较了索氏提取法、热回流法和冷浸法等提取方法;提出采用水沉法精制粗黄酮浸膏;通过L9(34)正交试验,优选了提取工艺参数。结果表明:索氏提取法测得荞麦蜂花粉总黄酮含量最高,为3.81%;冷浸法提取工艺虽然提取率稍低,但实用价值高。 相似文献
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用直接升华法从茶叶中提取咖啡因 总被引：1，自引：0，他引：1
用直接升华法从茶叶中提取咖啡因杨玉权，孙颖从茶叶中提取咖啡因，是有机实验中唯一一个从天然植物中提取杂环化合物的制备实验，同时也是验证茶叶中含咖啡因的重要方法。但因实验中需用索氏提取器，而我们实验室中又无此仪器，因此我们在多年教学中，摸索出用“直接升华... 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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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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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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《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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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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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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YANGShiguo 《重庆大学学报(英文版)》2004,3(1):86-88
The problem on the geometrc inequalities involving an n-dimensional simplex and its inscribed simplex is studied. Aninequality is established, which reveals that the difference between the squared circumradius of the n-dimensional simplex andthe squared distance between its circumcenter and barycenter times the squared circumradius of its inscribed simplex is not lessthan the 2(n-1)th power of n times its squared inradius, and is equal to when the simplex is regular and its inscribed siplex is atangent point one. Deduction from this inequality reaches a generalization of n-dimensional Euler inequality indicating that thecircumradius of the simplex is not less than the n-fold inradius. Another inequality is derived to present the relationship betweenthe circumradius of the n-dimensional simplex and the circumradius and inradius of its pedal simplex. 相似文献