首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   698篇
  免费   110篇
  国内免费   815篇
化学   1362篇
晶体学   133篇
力学   9篇
综合类   13篇
物理学   106篇
  2024年   4篇
  2023年   10篇
  2022年   19篇
  2021年   28篇
  2020年   27篇
  2019年   38篇
  2018年   43篇
  2017年   43篇
  2016年   48篇
  2015年   51篇
  2014年   103篇
  2013年   160篇
  2012年   86篇
  2011年   140篇
  2010年   126篇
  2009年   113篇
  2008年   107篇
  2007年   88篇
  2006年   81篇
  2005年   70篇
  2004年   53篇
  2003年   64篇
  2002年   28篇
  2001年   26篇
  2000年   8篇
  1999年   11篇
  1998年   15篇
  1997年   1篇
  1996年   14篇
  1995年   6篇
  1994年   2篇
  1993年   2篇
  1992年   4篇
  1991年   2篇
  1988年   1篇
  1986年   1篇
排序方式: 共有1623条查询结果,搜索用时 15 毫秒
991.
ZHUO Xin  XU Ji-Gui  ZHANG LI  LIU Chao 《结构化学》2010,29(11):1743-1748
Two new transition metal compounds, [Mn(dpa)2(tmd)2]n (1, H2dpa = 4-hydroxy-phenyl-acetic acid, tmd = 4,4-trimethylenedipyridine) and [Co4(dpa)6(tmd)4(H2O)4]n·nH2O·nCl2 (2), have been synthesized by hydrothermal synthesis. Compound 1 crystallizes in the monoclinic system, space group P21/n with a = 9.828(3), b = 17.493(5), c = 11.616(4), β = 110.146(6)o, V = 1874.9(10)3, C42H42MnN4O6, Mr = 753.74, Z = 2, Dc = 1.335 g/cm3, μ = 0.406 mm–1, F(000) = 790, the final R = 0.1047 and wR = 0.2021 for 2698 observed reflections (I > 2σ(I)). Compound 2 crystallizes in the monoclinic system, space group P21/c with a = 11.7214(13), b = 17.1582(19), c = 24.625(3), β = 103.055(3)o, V = 4824.4(9)3, C100H104Cl2Co4N8O23, Mr = 2094.55, Z = 2, Dc = 1.443 g/cm3, μ = 0.809 mm–1, F(000) = 2180, the final R = 0.0550 and wR = 0.0673 for 4104 observed reflections (I > 2σ(I)). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. The structural analyses show that the two compounds are both one-dimensional chain structures. However, compounds 1 and 2 form threedimensional supramolecular structures by hydrogen bonds, respectively.  相似文献   
992.
A new organic-inorganic hybrid sandwich-type arsenotungstate[H2dap]2H2[Ni(dap)2] [Ni(dap)2(H2O)2][Ni4(H2O)2(B-α-AsVW9O34)2]·8H2O 1 (dap = 1,2-diaminopropane) has been synthesized by the reaction of Na6[AsIII2W21O69(H2O)]·nH2O, NiCl2·6H2O and dap under hydro- thermal conditions and structurally characterized by elemental analysis, IR spectroscopy, thermo- gravimetric analysis and single-crystal X-ray diffraction. 1 crystallizes in the monoclinic space group P21/n with a = 13.5133(19), b = 19.043(3), c = 17.647(2) , β = 102.585(2)°, V = 4432.0(11) 3, T = 296(2) K, Z = 2, μ = 25.350 mm–1, GOOF = 1.058, R = 0.0353 and wR = 0.0838. The molecular unit of 1 consists of two diprotonated [H2dap]2+ cations, two protons, one four-coordinate [Ni(dap)2]2+ cation, one six-coordinate [Ni(dap)2(H2O)2]2+ cation, one classic tetra-NiII substituted sandwich-type [Ni4(H2O)2(B-α-AsVW9O34)2]10– polyoxoanion and eight lattice water molecules. Furthermore, some reported different types of transition-metal substituted sandwich-type poly- oxoanions are summarized and compared.  相似文献   
993.
《结构化学》2010,29(4):660-660
<正>《结构化学》是由中国科学院主管,中国化学会、中国科学院福建物质结构研究所主办的学术性期刊。1982年由我国著名化学家卢嘉锡院士创办并担任主编,现任主编是著名化学家吴新涛院士。《结构化学》主要报道晶体学,量子化学,药物、材料和催化剂等领域物质性  相似文献   
994.
A novel complex ZnTPPL1·3DMF 1(TPP = tetraphenylporphyrin,L1 = N-(4-(9-carbazolyl) phenyl)-N,N-di(4-pyridyl)amine) was prepared by a hydrothermal method and characterized by elemental analysis,IR,and single-crystal X-ray diffraction analysis.Compound 1 crystallizes in triclinic,space group P1 with a = 13.3082(2),b = 14.3276(2),c = 18.6120(3) ,α = 109.853(1),β = 95.054(1),γ = 98.832(1)°,V = 3260.57(9) 3,Z = 2,Dc = 1.334 g/cm3,C81H69N11O3Zn,Mr = 1309.84,μ(MoKα) = 0.438 mm-1,F(000) = 1372,GOF = 1.159,the final R = 0.0482 and wR = 0.1479 for 12091 observed reflections(Ⅰ 2σ(Ⅰ)).Crystal structure analyses revealed that L1 utilizes one pyridyl N atom to bind Zn via axial coordination,affording a 1:1 complex.The binding constant was estimated to be 1.74(7) × 104 M-1 from electronic spectra measurements.  相似文献   
995.
A novel supramolecular compound,{[2-(2-pyridyl)benzimidazoleH2]2·[BiCl6]·Cl},was synthesized by the hydrothermal reaction of o-phenylenediamine and α-pyridinecarboxylic acid with BiCl3 in 6.0 mol·L-1 HCl solution,and characterized by elemental analysis,IR,X-ray single-crystal diffraction and photoluminescence spectroscopy.The crystal (C24H22N6Cl7Bi,Mr= 851.61) belongs to the triclinic system,space group P1 with a =7.2887(18),b =9.548(2),c= 12.469(3),α=85.306(4),β=82.814(4),γ=71.349(4)°,Z=1,V=814.9(3)3,Dc=1.735 g/cm3,μ(MoKα)=6.007 mm-1,F(000)=410,R=0.0307 and wR=0.0787.The bismuth ion and six chlorine ions construct a distorted octahedral configuration.The three-dimensional supramolecular network is built from electrostatic attractions,hydrogen bonds and π-π interaction between the BiCl6 anion,Cl anion and [2-(2-pyridyl)benzimidazoleH2] cation.The photoluminescence spectroscopy study shows that the title compound has a blue fluorescent emission at 450 nm in the solid state.  相似文献   
996.
Two new coordination polymers,[Co(BYBA)2(4,4'-bpy)(H2O)2]·H2O (1) and [Zn(BYBA)2(4,4'-bpy)] (2) (4,4'-bpy=4,4'-bipyridine,BYBAH= 2-benzoylbenzoic acid),have been synthesized by hydrothermal conditions and characterized by single-crystal X-ray diffraction,elemental analyses,IR spectra and fluorescence spectrum.Crystal data for 1:C38H32CoN2O9,Mr= 719.59,monoclinic,space group P2/c,a=22.981(2),b=11.4438(11),c=12.9327(12),β=94.642(1)°,V=3390.0(5)3,Z=4,Dc=1.410 g/cm3,F(000)=1492,R=0.0488 and wR=0.1201;and those for 2:C38H26ZnN2O6,Mr=672.00,triclinic,space group P1,a=8.7032(10),b=11.4882(13),c=16.872(2),α=107.146(1),β=99.055(1),γ=90.851(2)°,V=1588.5(3)3,Z= 2,Dc=1.405 g/cm3,F(000)=692,R=0.0409 and wR=0.0894.Complex 1 exhibits 1D polymeric chains which are linked into a 2D sheet by π···π interactions.Complex 2 is composed by 1D zigzag chains connected through C-H···π stacking interactions to generate a 2D layer.  相似文献   
997.
A copper(Ⅱ) coordination polymer, [Cu3(HOA)2(bpp)4]n (1, HnOA = 3,3',4,4'- oxidiphthalic acid, bpp = 1,3-bis(4-pyridyl) propane), has been hydrothermally synthesized. The crystal structure is of monocl...  相似文献   
998.
A new compound,[Cu(mal)(tmdpy)(H2O)]·4H2O(1,H2mal = malonic acid,tmdpy = 4,4'-trimethylenedipyridine) has been synthesized by the hydrothermal synthesis and structurally characterized by X-ray crystallography. It crystallizes in triclinic,space group P1 with a = 9.1662(6),b = 10.6266(7),c = 11.3056(7) ,α = 84.6390(10),β = 72.1030(10),γ = 73.0420(10) o,V = 1002.37(11) 3,C16H26CuN2O9,Mr = 453.93,Z = 2,Dc = 1.504 g/cm3,μ = 1.140 mm-1,F(000) = 474,R = 0.0375 and wR = 0.0975 for 3187 observed reflections(I > 2σ(I)) . In the structure of 1,the tmdpy ligands link the [Cu(mal)(H2O) ] units into an infinite chain,and the water molecules and carboxylate oxygen donors(O(2) and O(4)) from the mal ligands cooperatively built an interesting hydrogen bonding network with unprecedented pseudo water tape substructures.  相似文献   
999.
采用简单的相转化方法合成出直径为20~30 nm、长度为几微米的β-Ni(OH)_2纳米线.利用XRD和FESEM表征了样品的结构和形貌,并采用循环伏安法、恒流充放电和交流阻抗谱等测试了样品的电化学性能.结果表明,在氢氧化钠溶液中,水热时间为30 min时,Paraotwayite型α-Ni(OH)_2纳米线转化为β-Ni(OH)_2纳米线.在不同扫描速率下,电极材料α-Ni(OH)_2和β-Ni(OH)_2纳米线的可逆性和倍率性能均优于β-Ni(OH)_2纳米片.  相似文献   
1000.
以六次甲基四胺、硫酸亚铁、柠檬酸钠为原料,采用水热合成方法制备了三氧化二铁(Fe_2O_3)粉体。以铅离子为水体中的模拟污染物,研究了Fe_2O_3对水体中重金属离子的吸附性能,结果表明,当柠檬酸钠的浓度为0.004 mol/L、水热温度为100℃和水热时间为8 h时,所制备的Fe_2O_3的吸附性能最好,其对铅离子的吸附容量为426.09 mg/g。X射线衍射(XRD)图片和扫描电子显微镜(SEM)照片显示所制备的粉体为低结晶度的分级花状Fe_2O_3微球。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号