共查询到20条相似文献，搜索用时 62 毫秒
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众所周知,器官移植是当代医学和生物学的热门话题,当今世界各国都将此作为衡量一个国家综合医学水平的标准.器官移植中的最大难题是排异反应或异体排斥.人体天然存在着一种排斥外来组织的倾向——“不是我身上的东西,我坚决不要它”.如果外来(供体)的器官组织与自身(受体)的器官组织不匹配,也就是它们的细胞表面抗原特征不相同,那么受体的免疫系统就会对移植来的供体器官发动猛烈攻击,直至置于死地,从而造成器官移植的失败.事实上,除了孪生子,其他人体之间的器官移植都要发生排异反应(血缘关系 相似文献
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维生素C对人体有益与有害作用剖析 总被引：3，自引：0，他引：3
刘旺喜 《江西教育学院学报》2000,21(6):42-44
维生素C（又名抗坏血酸）是人与动物生命活动中必需的物质,参与组织细胞内许多物质的氧化还原反应,可以捕捉自由基,对人体起保护作用,但是人体如果过量地摄取维生素C,则会产生一系列有害作用。 相似文献
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生活中当某些物质进入人体后,会对组织器官发生生物化学或生物物理学作用,如果这些作用损害了人体健康,便可引起人体的中毒反应,严重时可导致死亡。因此有必要了解常见中毒以及相关的急救知识。 相似文献
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水热法制备氧化锆超细粉体工艺研究 总被引：1，自引：0，他引：1
文章以价格低廉氧氯化锆、氢氧化钠等无机盐为原料,利用水热法制备生物陶瓷用超细氧化锆粉体,通过对pH值、反应时间、反应的温度、矿化剂的用量等因素进行实验研究。结果表明：适宜的工艺条件为水热反应温度180℃、反应时间5 h、控制溶液的pH＝10、适宜的矿化剂浓度为0．1mol／L。 相似文献
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教学活动是师生双方的互动行为.在教学过程中,师生间的交流除有声语言外,还可以运用人体语言进行信息的交流.人体语言在教学中的作用明显它有助于教师组织课堂教学;有助于提高教学效果;有助于对学生的了解和教育.概之,如果我们能正确运用人体语言,必将对教学产生重要影响. 相似文献
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黎桦 《湖北第二师范学院学报》2014,(9)
“脱离说”与“意志说”对人体组织法律性质的界定均无法解决遗体组织捐献过程中存在的法律困境。应对人格权进行适度扩张,规定只有在满足如下构成要件的情况下,人体组织才构成物,否则均属于人格权载体：首先,该人体组织需处于已经脱离人身的状态中。其次,自然人有放弃该人体组织作为人身组成部分的明确意思表示,但在该自然人仍然存活,且人体组织对该自然人已不具有任何人身或财产价值的情况下,不具有该意思表示亦可。最后,自然人为无民事行为能力人时得违背第二构成要件,不需要有明确意思表示,但该人体组织对该自然人必须已不具有任何人身或财产价值,同时其直系亲属类监护人须一致同意放弃该人体组织作为人身组成部分。这一构成要件的界定明确了遗体组织捐献时自然人行使人格权和物权处分的界限,亦明确了合法行为与非法行为的界限。 相似文献
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氨气与氯化氢的反应体现了氨的重要化学性质.在实验过程中,该反应存在以下问题:浓氨水、浓盐酸的挥发污染环境,危害人体健康;反应产物是烟还是雾,无法进行验证;反应一次性进行,无法重复演示.为解决这些问题,笔者特设计了一套进行氨气和氯化氢反应的微型化装置,它不仅适合于教师多次重复演示,而且适合于学生实验.该装置设计简单,易于操作,无污染,实验效果良好,可以验证产物是烟还是雾. 相似文献
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以自制硅酸钙（CaSiO3）和羟基磷灰石（HAP）超细粉体为原料,按照不同的比例混合、成型、煅烧制得CaSiO3-HAP复合生物陶瓷。采用X-射线衍射仪（XRD）和扫描电镜（SEM）对粉体及陶瓷样品进行物相成分和显微结构分析,并对复合生物陶瓷的收缩率、抗弯强度、断裂韧性和硬度等性能进行测定。研究结果表明：在HAP中添加一定量的CaSiO3,可以减小HAP陶瓷的收缩,并能提高其力学性能,CaSiO3含量为30wt％的CaSiO3-HAP复合生物陶瓷综合性能最佳,其抗弯强度和断裂韧性分别达到156．7MPa和2．32MPa·m^1/2,维氏硬度值达到6．5GPa,比纯HAP陶瓷的性能均有了较大的提高。 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