共查询到20条相似文献，搜索用时 313 毫秒
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曹保鹏 《商丘师范学院学报》1997,(Z2)
以填B4C固体粉末（粒径约1mm）的高纯石墨棒为阳极，以高纯石墨捧为阴极，在He气氛下，用直流电弧法制备出了超细B4C的粉末，扫描电镜（SEM）研究表明，该超细B4C粉末的形状有三种：球及合有空洞的球、树枝状的棒或管、细小的颗粒，这些球及颗粒的粒径分布在数十纳米到数十微米范围内．这为粉碎莫氏硬度为9.28的B4C固体找到了新的、简便、可行的方法． 相似文献
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采用反相悬浮聚合法合成了聚丙烯酰胺（PAM）高分子微凝胶,以其为模板,在室温条件下,以硒代硫酸钠（Na2SeSO3）作为硒源,制备得到了Se—PAM无机-有机复合微球材料,利用扫描电子显微镜（SEM）、X射线衍射（XRD）等手段对复合微球的形貌、无机物硒晶形结构等进行了表征。 相似文献
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白殿罡 《鞍山师范学院学报》2008,10(6):45-47
利用模板合成[（Butyl-）4N]4SiW12O40微米棒．利用扫描电子显微镜（SEM）、红外光谱（IR）和X射线粉末衍射（XRD）等测试手段对其形貌和组成进行了表征．通过对长、宽和厚度的对比,讨论了微米棒的形成机理． 相似文献
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白殿罡 《鞍山师范学院学报》2008,10(6)
利用模板合成[（Butyl-）4N]4SiW12O40微米棒．利用扫描电子显微镜（SEM）、红外光谱（IR）和X射线粉末衍射（XRD）等测试手段对其形貌和组成进行了表征．通过对长、宽和厚度的对比,讨论了微米棒的形成机理． 相似文献
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孔德成 《中学物理教学参考》1997,(3)
一道有趣的物理习题孔德成（江苏省常熟中学，２１５５００）题目：摆绳长Ｌ的下方挂一质量为ｍ的小球，现将小球用轻棒与一质量为Ｍ的球相连，Ｍ球悬挂的绳子无限长（如图１）．现使Ｍ、ｍ两球在水平面内摆动，求摆动周期．图１有学生认为：绳长为Ｌ、质量为ｍ的小球可以... 相似文献
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采用反相悬浮聚合法合成了聚丙烯酰胺(PAM)高分子微凝胶,以其为模板,在室温条件下,以硒代硫酸钠(Na2SeSO3)作为硒源,制备得到了Se-PAM无机-有机复合微球材料,利用扫描电子显微镜(SEM)、X射线衍射(XRD)等手段对复合微球的形貌、无机物硒晶形结构等进行了表征。 相似文献
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２０００年安徽省春季高考物理最后一题，是以两个小球相对运动为题型的纯力学题，它与以往试题所不同的是已知条件少（仅知一个球初速度和后一个阶段的时间）看起来难以求解，这正是该题的新颖之处． ［题目］相隔一定距离的Ａ、Ｂ两球，质量相等，假定它们之间存在恒定的斥力作用．原来两球被按住，处在静止状态．现突然松开两球，同时给Ａ球以速度 ０，使之沿两球连线射向Ｂ球，Ｂ球初速为零．若两球间的距离从最小值（两球未接触）到刚恢复到原始值所经历的时间为ｔ０，求Ｂ球在斥力作用下的加速度． 因为该题有多种解法，几乎涉及到全… 相似文献
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采用硒（Ⅳ）-KI-结晶紫显色体系,在酸性条件下,硒（Ⅳ）-KI-结晶紫体系发色快,显色灵敏度高,线形范围宽。显色体系反应机理为硒（Ⅳ）在酸性介质中定量的与I^-作用,得到体积较大的I3^-离子再与结晶紫大阳离子形成有色缔合物。在一定硒浓度范围内,缔合物吸光度与硒浓度成正比,由此可定量测定硒。 相似文献
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分别采用湿法消解和微波消解处理了7月、9月和11月3个收获时期鬼针草样品,以电感耦合等离子体发射光谱仪（ICP—AES）检测样品中硒的含量．结果表明：鬼针草的硒含量分别为1．312mg／kg,1．999mg／kg,0．187mg／kg,随季节有所变化,以9月份硒含量最高．ICP—AES测定硒元素的相对标准偏差（RSD）为0．15％-1．76％,回收率在98．23％～101．2％． 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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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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《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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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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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