共查询到20条相似文献，搜索用时 109 毫秒
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对天然产物中有机硒的分析方法进行了简要论述．研究了用原子荧光法（AFS）测定天然产物酸枣中有机硒的方法，选择了最佳仪器工作条件及化学试剂用量．方法检出限为0．57μg／L，线性范围为0—100μg/L，相关系数r=0．9997，回收率为91．75％～110．50％，变异系数小于2.024％． 相似文献
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目的构建L-ficolin突变体的原核表达载体，为研究L-ficolin的糖结合位点奠定基础。方法设计L-ficolin突变体基因上、下游引物，分别引入EcoRⅠ和XhoⅠ酶切位点。以插入L—ficolin M2（Val144Phe）和M6（Glu 307Asp）点突变的完整编码区基因的质粒pCDNA3-L-ficolin为模板，通过PCR扩增获得突变体的基因片段，将其克隆入原核表达载体pGEX—KG．然后通过酶切和序列测定对其进行鉴定；将此表达载体转化入表达菌BL21（DE3）pLvSs诱导表达。并采用SDS—PAGE对表达产物进行鉴定。结果经酶切及序列分析表明．成功地构建了重组原核表达载体pGEX-KG—L—ficolin—M2、pGEX-KG-L-ficolin—M6，SDS—PAGE显示目的蛋白大量表达。结论L—ficolin突变体融合蛋白可以在大肠杆菌中大量表达。为研究L-ficolin的糖结合位点打下基础。 相似文献
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题1 某兴趣小组查阅资料知，二甘醇的化学式为C4H10O3，它具有可燃性．他们对其燃烧产物进行了探究． 相似文献
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PEN合成研究Ⅰ:NDCA与EG酯化反应工艺 总被引：1，自引：0，他引：1
初步探讨了2，6-萘二甲酸(NDCA)与乙二醇(EG)酯化反应合成2，6-萘二甲酸乙二醇酯的工艺因素。筛选出钨酸钠作催化剂较合适，其用量为2％(g/gNDCA)，反应温度为215℃，EG与NDCA摩尔配比为3，反应时间为4h。对NDCA与EG酯化反应产物进行红外光谱分析、核磁共振分析，确定反应产物是目标产物。 相似文献
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张桂芳 《河北北方学院学报(医学版)》1989,(1)
近几年来,洁霉素在临床应用日趋普遍。据统计我院1988年1～6月份门诊处方平均月销售3358支,同用量较大的抗生素青霉素、庆大霉素之比为1:1.3:2。对我院1988年10月份门诊14267张处方进行统计开有洁霉素的处方有269张,为处方总数的1.9％。 相似文献
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设计了一条普利沙星的新合成路线，该合成路线工艺简单，原料易得，操作简便，收率稳定，用^1H、^13C、^19F NMR和IR、Ms对产物结构进行了表征，结果表明产品质量可靠．新合成路线总收率为8．9％，较原合成路线的总收率高出2％，适合工业化生产。 相似文献
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采用一种类似PCR的基因组自我引发PCR(GSP—PCR)法，初步研究了家蚕、野蚕、天蚕、蓖麻蚕和柞蚕的微卫星DNA的体外基因组自我引发PCR扩增的条件。结果发现。浓度为100ng/μl的基因组DNA在100℃变性15min后，与等量的同浓度的未变性的DNA混合作为模板。在80m扩增体系中[含0．2mM dNTPs、50mM KCl、10mM Tris—HCl(pH9．0)、4mM MgCl2、1．25U Tap plymerase]，加入1μl此混合模板，在92℃，1min→55℃，2min→72℃，2min，30→90次循环的扩增条件下，成功地得到了PCR产物。基因组DNA的适宜浓度为1．25ng/μl反应体系；GSP—PCR产物经琼脂糖凝胶电泳后的部分片段经回收后，在同样条件下，30—60个循环可得到同样大小范围的产物。GSP—PCR产物经6％的变性测序胶电泳，得到典型的梯状带，表明为微卫星DNA。 相似文献
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阳离子有机硅香波调理剂的制备及性能研究 总被引：2，自引：0，他引：2
以低含氢硅油、不饱和聚醚、一氯乙酸和二甲胺为原料，制备得阳离子有机硅油。通过红外光谱对产物组成进行了表征，并研究了其在香波中的调理性能。研究表明：加入质量分数为2％的产物湿梳理效果提高了19．3％，干梳理效果提高了10．0％，比普通乳化硅油具有更好的干湿梳理性能。 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