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新课程理念倡导学生是学习的主体,但在日常课堂教学中,有些学生的主体地位被过分地放大,教师的主导地位却被人为地弱化.在学生学习的过程中,为了更好地发挥教师作为组织者、引导者、合作者的作用,需要适时、适度的介入.笔者阐述搭桥、阻止、追问和点拨的有效介入策略. 相似文献
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合成了[La(Phen)2(NO3)2(H2O)2]ClO4·2Phen·H2O(1,化学式为C48H38ClN10O13La,Mr=1137.24,Phen=邻菲咯啉),经X-射线单晶衍射测定其晶体结构属于三斜晶系,Pī空间群,a=11.250(4),b=13.364(4),c=16.327(5)(。A),α=103.042(6),β=90.327(6),γ=99.567(6)°,V =2355.8(12)(。A)3,Z = 2,Dc =1.603g·cm-3,F(000)=1148,μ=1.042mm-1,R=0.0569,wR= 0.1064.1由 [La(Phen)2(NO3)2(H2O)2]+ 阳离子,ClO-4阴离子,两个共结晶的Phen分子和1个H2O分子构成.内界的中心金属La(III)离子为十配位的变形的双帽四方反棱柱体,其配位环境分别被6个来自两个双齿配位硝基和两个H2O分子的氧原子和4个来自两个Phen配体的氮原子所包围,形成单核+1价阳离子,外界有1个水分子,1个ClO-4阴离子和两个Phen分子构成.整个分子通过分子间氢键形成3D网络结构. 相似文献
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0IntroductionAlthoughtheself-assemblyofchiralsupramolec-ularentitiesiscommoninvivo,itremainsdifficulttorationalizedesignandpreparationofchiralartificialself-assemblingsystems犤1犦.Inrecentyears,chiralmet-al-organicsolidshaveattractedmuchattentionandhavebeenofintensecurrentinterestsduetothepo-tentialapplicationsinawidevarietyoffields犤2~4犦.Thechoiceofchiralaminoacidaseffectivemeanstoobtainhomochiralstructureshaveemergedmanyyears.Morerecently,Chinetal.reportedarationallydesignedaminoacidmetal… 相似文献
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由Co(C lO4)2.6H2O和Sch iff碱吡啶-4-甲醛缩氨基脲反应合成了标题化合物[Co(H4FoPyS)2(H2O)4](C lO4)2.2H2O(1,H4FoPyS为Sch iff碱吡啶-4-甲醛缩氨基脲),其结构经IR,单晶X-射线衍射和元素分析表征。1属三斜晶系,空间群P,īa=6.9015(13),b=10.2030(19),c=11.136(2),α=104.960(3)°,β=90.090(3)°,γ=108.177(4),V=716.9(2)3,Dc=1.613 mg.m-3,Z=1,Mr=696.29,μ=0.868 mm-1和F(000)=359,最终偏差因子分别为R1=0.0857和wR2=0.2361。在1的晶体结构中,Co(Ⅱ)是六配位的稍变形八面体构型,其中2个吡啶氮原子和2个配位水分子占据赤道平面,另外2个配位水分子处于轴向位置。配合物分子通过氢键(N-H┈O和O-H┈O)相连,形成三维超分子网状结构。 相似文献
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IntroductionDuringthepastdecades ,thedevelopmentoftheco ordinationchemistryofmolybdenum(VI)focusedonmet al oxygenclusterscharacterizedbyfascinatingstructural,electrochemical,catalytic ,magnetic ,medicinal,andphotophysicalproperties ,1whichareoffundamentaland… 相似文献
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The reaction of MoO2(acac)2 with 2-amino-6-methyl-pyridine (amp) in the mixed solvent of DMF (N,N-dimethylformamide) and water affords the title complex [H-amp]4- [Mo8O26(DMF)2]·2H2O which was characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis with the following crystallographic data: C30H54Mo8N10O30, Mr = 1802.35, monoclinic, P21/n, a = 8.631(1), b = 24.260(3), c = 13.351(2)A,β= 104.688(3)°, V = 2704.2(7) A3, Z = 2, Dc = 2.213 g/cm3, μ =1.890 mm-1 and F(000) = 1760. The final R = 0.0281 and Wr = 0.0620 for 4935 observed reflections with I > 2σ(I). X-ray structure analysis has confirmed the existence of γ-[Mo8O26]4- anion in the molecule. Eight MoO6 distorted octahedra share edges with short terminal Mo-O bonds from 1.691(3) to 1.749(2)A, medium bonds from 1.868(2) to 1.965(2) A And long bonds from 2.059(2) to 2.450(2) A. In the terminal site there exist two DMF ligands bound to the Mo atom through O atoms with the Mo-ODMF bond length of 2.166(3) A, affording a bond strength of 0.433. A three-dimensional network structure was formed through hydrogen bonds. 相似文献