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   1079篇
  免费   294篇
  国内免费   656篇
化学   1400篇
晶体学   50篇
力学   8篇
综合类   16篇
数学   77篇
物理学   478篇
  2024年   6篇
  2023年   24篇
  2022年   83篇
  2021年   74篇
  2020年   63篇
  2019年   29篇
  2018年   42篇
  2017年   83篇
  2016年   75篇
  2015年   91篇
  2014年   131篇
  2013年   170篇
  2012年   198篇
  2011年   172篇
  2010年   98篇
  2009年   71篇
  2008年   89篇
  2007年   116篇
  2006年   30篇
  2005年   68篇
  2004年   73篇
  2003年   35篇
  2002年   25篇
  2001年   19篇
  2000年   28篇
  1999年   18篇
  1998年   23篇
  1997年   16篇
  1996年   21篇
  1995年   5篇
  1994年   8篇
  1993年   7篇
  1992年   6篇
  1991年   5篇
  1990年   6篇
  1989年   7篇
  1988年   4篇
  1987年   2篇
  1985年   7篇
  1983年   1篇
排序方式: 共有2029条查询结果,搜索用时 15 毫秒
11.
1 INTRODUCTION The tris(ethylenediamine) cobalt (Ⅲ) complex in which there are L and D configurations is one of the very interest cations due to the chirality among research complexes and the characterization of reaction on the ion-pair charge-transfer transitions. It has been mentioned in a lot of examples on the chirality and the structure, such as [L-Co(en)3]- [?Co(edta)]2Cl?0H2O[1], [(+)DCo(en)3]Cl3稨2O[2], [(+)-Co(en)3?-)-Cr(en)3]Cl?.1H2O[3], [()-Co(en)3] (SCN)3[4], [(+)D…  相似文献   
12.
A new dinuclear copper complex, [Cu(C9H11N3)Cl2]2 (C18H22Cl4Cu2N6), has been synthe- sized and characterized by X-ray structure determination. It crystallizes in the triclinic P1 space group with a = 7.526(3), b = 9.473(4), c = 9.535(3) , α = 117.214(10), β = 108.251(9), γ = 91.560(6)o, V = 562.3(4) 3, Z = 1, Mr = 591.30, F(000) = 298, Dc = 1.746 g/cm3, μ(MoKα) = 2.385 mm-1, the final R = 0.0577 and wR = 0.1248 for 2188 unique reflections with 1629 observed ones (I > 2σ(I)). In the title complex, each copper(II) atom is located at the center of a distorted trigonal bipyramid of five coordination atoms (two nitrogen and three chlorine atoms). Two copper(II) atoms were bridged by two chlorine anions (Cl(2) and Cl(2a)) to form a Cu(II)-Cu(II) binuclear entity with the distance between two copper(II) atoms of 3.398 .  相似文献   
13.
乐学义  童明良 《无机化学学报》2002,18(10):1023-1027
The complex [Cu(L-met)(phen)(H2O)]NO3·H2O has been synthesized and investigated by elemental analysis, molar conductivity, spectroscopic and X-ray diffraction methods, where phen=1,10-phenanthroline and L-met=L-methioninate group. The complex crystallized in the monoclinic space group P21 with a=12.053(2)?, b=6.886(1)?, c=13.385(3)?, β=113.59(3)°, V=1018.1(3)?3, Z=2,Dc=1.598g·cm-3, μ=1.223mm-1, F(000)=506, R1=0.0306, and wR2=0.0742. The copper(Ⅱ) atom is ligated in a distorted square-pyramidal geometry by two nitrogen atoms of one phen and the amino nitrogen atom , one carboxylate oxygen atom of L-met in the base plane, and an aqua at the apical position. A one-dimensional chain configuration formed by the hydrogen-bonding and weak Cu-O (the uncoordinated carboxyl oxygen atom) coordination interactions be-tween neighboring [Cu(L-met)(phen)(H2O)]+ cations. CCDC: 183368.  相似文献   
14.
A new 1,3,4 thiadiazole-derivative ligand 2,5-(s-acetic acid) dimercapto-1,3,4 thiadiazole (H2ADTZ) and its one-dimensional manganese polymer Mn(ADTZ)·4H2O had been synthesized and structurally characterized by X-ray single crystal diffraction in this paper. The Mn(Ⅱ) ion is coordinated with a distorted octahedron by two oxygen atoms from neighboring two deprotonated ligands ADTZ2- and other four oxygen atoms from four coordinated water molecules. The structural feature of the title compound is the formation of one-dimensional manganese chains polymer through the bridging of dioxygen O-O units. In the solid state structure of the complex, one-dimensional manganese chains are joined together by the weak intermolecular hydrogen bonds and vander Waals interactions forming a two-dimensional supramolecular compound. Furthermore, the UV spectra and electro-chemical properties of the title compound were also investigated. CCDC: 260532.  相似文献   
15.
在HF和MP2水平用全电子(AE)和相对论有效芯势(RECP)方法研究了Ⅰa、Ⅰb、Ⅱa和Ⅱb族金属离子与β D 核糖(RI)的相互作用. 结果表明, RECP能可靠地用于重金属离子;二价金属离子(M2+)比一价金属离子(M+)更易使β D 核糖(RI)变形;二价金属离子络合物(RI M2+)比一价金属离子络合物(RI M+)稳定. 电荷布居分析的结果支持上述结论.  相似文献   
16.
黄雪峰  钱坤 《无机化学学报》2005,21(9):1437-1438
Compound [Zn(phen)3][BDA] (1) (BDA=6,6′-dibromo-2,2′-dimethoxy-1,1′-binaphthylene-4,4′-disulfonate, phen= 1,10-phenanthroline) composes of the anion part (racemic-(R,S)-6,6′-dibromo-2,2′-dimethoxy-1,1′-binaphthylene-4,4′-disulfonate ) and the cation part which consists of a racemic octahedrally coordinated zinc center defined six nitrogen atoms from three phen rings to form an inorganic chirality that can be resolution by chiral organic ligand, the 3D framework was formed through the strong H-bonding interaction between sulfonate and water. CCDC: 277924.  相似文献   
17.
Two novel complexes {[Co(A-glu)(Im)2]·0.5H2O}n (1) and [Cd(A-glu)(Im)3]n (2) (H2A-glu=N-acetyl-L-glutamic acid, Im=imidazole) have been synthesized from the reaction of H2A-glu with Co(CH3COO)2·4H2O or Cd(CH3COO)2·2H2O in the presence of Im. Both of the complexes display different coordination environment and similar one-dimensional chain structure. The magnetic susceptibility measurements for 1 show a weak antiferromagnetic interaction between two cobalt(Ⅱ) ions bridged by A-glu ligand. The complex 2 exhibits an intense fluorescent emission in solid state at room temperature.  相似文献   
18.
钒的氨基酸配合物具有重要的生物和医学意义。VO(Ⅱ)-组氨酸配合物及VO(Ⅱ)-π受体二元配合物的ESR研究已有报道。但是VO(Ⅱ)-氨基酸-π受体三元配合物的结构及其ESR研究至今未见报道。本文考察了VOSO_4与组氨酸(His)和邻菲啰啉(Phen)及α,α′-联吡啶(bipy)三元体系在不同酸度(pH=1~14)的乙二醇/水(1:1)溶液中低温(173K)ESR波谱,获得了不同pH条件下配合情况的详细信息。  相似文献   
19.
二(芳氧基)稀土(Ⅱ)配合物催化ε-己内酯开环聚合   总被引:2,自引:0,他引:2  
系统地研究了二(2,6 二叔丁基 4 甲基酚基)钐[(ArO)2Sm(THF)4]催化ε 己内酯的开环聚合,发现它具有很高的催化活性并显示“活性”聚合的特点,在甲苯中,当[M]/[I]=2000(摩尔比),60℃,1h,转化率可达98%.并比较了不同的两价稀土化合物的催化活性.通过核磁分析末端基结构的方法,研究了(ArO)2Sm催化己内酯开环聚合的引发机理,发现催化剂首先与己内酯反应,生成三价烯醇式稀土化合物,后者引发己内酯聚合.  相似文献   
20.
WANG Yu-Fang  WANG Li-Ya 《结构化学》2007,26(12):1461-1465
A new copper(Ⅱ) compound with imino nitroxide radicals [Cu(IM-MeImz)2]·(SCN)2 (IM-meImz =2-(5-methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl) has been synthesized and characterized structurally and magnetically. It crystallizes in monoclinic, space group P21/c with a = 9.3604(7), b = 10.3012(7), c = 16.6684(12) (A), β = 105.0290(10)°, V = 1552.25(19)(A)3, C24H34CuN10O2S2, Mr = 622.27, Z = 2, Dc = 1.331 g/cm3, μ(MoKα) = 0.876 mm-1, F(000) =650, the final R = 0.0374 and wR = 0.1079. X-ray analysis demonstrates that the IM-MeImz ligand is coordinated to the copper(Ⅱ) ion as an unusual didentate chelate with a κ2 N(MeImz),O(IM) mode in the complex. The square-planar coordination sites at Cu(Ⅱ) are occupied by two O and two N atoms from the imino nitroxide radicals. The complex molecules are connected as a onedimensional polymer structure by intermolecular interactions. Magnetic measurements show that there are intramolecular antiferromagnetic interactions between the Cu(Ⅱ) ion and radicals.  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