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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《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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《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
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献