共查询到20条相似文献，搜索用时 640 毫秒
1.
槟榔嚼块（betel quid）是一种由槟榔果和多种添加物组成的混合物,含有槟榔碱、槟榔次碱、去甲槟榔次碱等多种生物碱,对中枢和外周神经系统均产生明显的药理作用,具有一定的滥用潜力和依赖性。 相似文献
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题目 （2005年盐城市中考题）有由氯化钾和盐A组成的固体混合物，其中A的质量分数为69％．现取10g该固体混合物，加入50g质量分数为7．3％的盐酸，它们可恰好完全反应，得无色溶液， 相似文献
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张传新 《商丘师范学院学报》1995,(Z2)
以正辛醇和氢溴酸为原料，以浓Ｈ２ＳＯ４为催化剂，以９８％的高收率合成溴代正辛烷，反应具有条件温和，配比合理、操作方便和后处理简单等优点，十分适宜于工业生产． 相似文献
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例1为恰好中和某一强碱溶液，需用加g溶质质量分数为a％的盐酸．若改用加g溶质质量分数仍为a％的硫酸，并在反应后向所得溶液中滴入石蕊试液，则所得溶液显（ ） 相似文献
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用３７％的盐酸，把粉丝浆液调至ＰＨ为４．２－４．５，在３１８Ｋ凝聚３０－５０分钟，分离，加碱调至ＰＨ为６．８－７．０，在３３３Ｋ，真空度５８０ｍｍＨｇ下，真空脱水干燥６０－９０分钟，得优质蛋白，可用作蛋白饲料或制绿豆蛋白食品。 相似文献
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郑雪凌 《山东商业职业技术学院学报》2006,6(4):90-92
利用二道生理记录仪记录大鼠离体子宫平滑肌的运动，观察不同浓度的槟榔碱对子宫平滑肌条的作用，以及M-受体、a-受体、组胺H1受体、L-型钙通道和前列腺素合成酶分别被阻断或抑制后，这种作用受到的影响，以探讨槟榔碱对大鼠离体子宫平滑肌的作用和机制。结果表明：槟榔碱可促进离体子宫平滑肌的收缩，对收缩波的频率、振幅、收缩波面积作用显著，且呈显著正相剂量效应关系，而对收缩波的持续时间影响很小。槟榔碱的这种作用可被阿托品阻断，即证明该作用可能是通过M-受体发挥作用，与a-受体、组胺Hl受体、L-型钙通道及前列腺素合成酶的释放无关。 相似文献
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以二辛胺为原料,硫酸二甲酯为烷基化试剂,CaO为缚酸剂,通过非均相的液—固反应,常压下合成了二辛基二甲基氢氧化铵,二辛胺能定量转化。将二辛基二甲基氢氧化铵与盐酸或氢溴酸中和得到二辛基二甲基季铵盐。此方法反应时间短,反应产率高,一般可达98.2％,所得产品纯度高。 相似文献
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茶树中茶多糖含量测定及提取研究 总被引：6，自引：0，他引：6
考察了温度、酸碱盐介质及微波提取对茶多糖提取的影响，实验表明，用氯仿、乙酸乙酯将茶叶、茶树枝梢、茶树根粉末进行回流提取之后，再用质量分数2％的碳酸钠溶液在微波提取器中浸提3次，可将茶多糖及其它有效成分充分提取出来，其中茶树根多糖提取率高达7．25％，茶树枝梢可达6．34％，粗老叶子可达6．07％。 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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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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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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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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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