共查询到20条相似文献，搜索用时 265 毫秒
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通过溶液法培养了2-吡嗪甲酸的单晶,利用单晶X-射线衍射法测定了其晶体结构,同时利用元素分析、红外光谱对其进行了表征。晶体学数据：正交晶系,Pnma空间群,α=11．3557（18）A,b=6．4573（10）A,c=7．3674（12）A,α=90°,β=90°,γ=90°,V=540．23（15）A3,Z=4,pcalc=1．455g·cm^-3,R1=0．0400,wR2=0．1099。结构分析表明2-吡嗪甲酸分子通过氢键作用连接成一维链状超分子结构。 相似文献
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利用4,6-tBu2-1-(HO)C6H2CH2Br与甲基咪唑反应合成了芳氧功能化的氮杂环卡宾前体[HO-4,6-tBu2-C6H2-2-CH2{CH(NCHCHN)CH3}]Br.然后,在60℃条件下以CH2Cl2作溶剂,将该前体与Ag2O反应合成了新的芳氧功能化的氮杂环卡宾银配合物Ag[O-4,6tBu-C6H2-2-CH2{CH(NCHCHN)CH3}].配合物进行红外光谱表征. 相似文献
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根据文献合成4,6-^tBu2-1-（HO）C6H2CH2Cl;利用亲核取代反应合成了一种芳氧功能化的咪唑[HO-4,6-di—C（CH3）3-C6H2-2-CH2{（NCHCHN）CH2}]。芳氧功能化的咪唑通过元素分析,核磁和单晶衍射表征。晶体结构表明其晶体属单斜晶系,空间群为P2 1／e,化学式为C18H26N2O,晶胞参数为a=18．694（3）A,b=10．2501（15）A,c=9．1536（15）A,α（deg）=90deg,β（deg）=103．006（4）deg,γ（deg）=90deg,V（A^3）=1708．9（5）A^3,Z=4,最终R1=0．1160,wR2=0．2263． 相似文献
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通过使用混合配体得到氢键连接的二维超分子配位化合物[Ni（mal）（tpm）（H2O）].2H2O（mal=丙二酸,tpm=三吡唑甲烷）,并对其进行了X射线晶体衍射、元素分析、红外光谱、电子光谱表征.该配合物的晶体属正交晶系,Pca21空间群,晶胞参数a=1.5421（3）nm,b=0.90629（19）nm,c=1.2822（3）nm,α=90°,β=90°,γ=90°,V=1.7920（7）nm3,Z=4.中心Ni（Ⅱ）离子为六配位,处于扭曲的八面体配位环境中.晶格水与配位水形成较强的氢键将配合物连接成二维超分子结构. 相似文献
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根据文献合成4,6-^tBu2-1-（HO）C6H2CH2Cl;利用亲核取代反应合成了一种芳氧功能化的咪唑[HO-4,6-di—C（CH3）3-C6H2-2-CH2{（NCHCHN）CH2}]。芳氧功能化的咪唑通过元素分析,核磁和单晶衍射表征。晶体结构表明其晶体属单斜晶系,空间群为P2 1／e,化学式为C18H26N2O,晶胞参数为a=18．694（3）A,b=10．2501（15）A,c=9．1536（15）A,α（deg）=90deg,β（deg）=103．006（4）deg,γ（deg）=90deg,V（A^3）=1708．9（5）A^3,Z=4,最终R1=0．1160,wR2=0．2263． 相似文献
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题目如图1,在△ABC中,已知∠BAC=45°,若AD⊥BC于点D,且BD=3,CD=2,则S△ABC=____．文[1]、文[2]、文[3]给出了这道竞赛题的四种解法,文[1]、文[2]的解法较为复杂,文[3]的解法虽然简便,但当∠BAC=30°,60°,…时无法求解．能否找到更实用且相对简便的解法呢？笔者给出三种解法以飨读者． 相似文献
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5-叔丁基-1,3-间苯二甲酸、1,3-双吡啶丙烷与醋酸镍以1：1：1的摩尔比在纯水溶剂中反应合成了镍的配合物{[Ni2（L）2（1,3-dpp）2（H2O）]·H2L}n（H2L=5-tert-butylisophthalic acid,1,3-dpp=1,3-di（4-pyridyl）propane）．通过红外以及X-衍射分析,确认了其化学结构．Mr=1112．02,晶体属单斜晶系,C2／m空间群,晶胞参数：a=35．166（4）A,b=20．051（2）A,c=17．115（2）A,β=95．003（2）°,V=12022（3）A^3,Z=8,Dc=1．229mg／m^3,最终偏差因子R1=0．0720,wR2=0．1901[I〉2σ（I）]． 相似文献
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5-氯-3-甲基-1-苯基-4-吡唑甲醛的合成和晶体结构 总被引：1，自引：0，他引：1
合成了吡唑类化合物5-氯-3-甲基-1-苯基-4-吡唑甲醛,用X-单晶衍射测定了晶体结构。结果表明,晶体属单斜晶系,P2（1）／C空间群,晶胞参数a=0．6345（7）nm,b=0．68432（7）nm,c=2．2331（2）nm,α=90°,β=93．816（2）°,γ=90°;晶胞体积V=1．02685（19）nm^3;晶体密度Dm=1．427Mg／m^3,Z=4,吸收系数μ=0．344mm^-1,F（000）=456．分子间依靠C（8）-H（8B）…0（1）和C（2）-H（2）…0（1）#1氢键形成晶体结构堆积。 相似文献
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例1如图1,已知AD与BC相交于点0,AB∥CD,如果∠B=40°,∠D=30°,则∠AOC的大小为（ ）．A．60°B．70°C．80°D．120° 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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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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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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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