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   55篇
  免费   5篇
  国内免费   11篇
化学   64篇
物理学   7篇
  2023年   1篇
  2022年   1篇
  2021年   6篇
  2020年   2篇
  2019年   2篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2014年   1篇
  2013年   4篇
  2012年   3篇
  2011年   3篇
  2010年   4篇
  2009年   4篇
  2008年   6篇
  2007年   8篇
  2006年   6篇
  2005年   2篇
  2004年   3篇
  2003年   1篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
  1994年   2篇
排序方式: 共有71条查询结果,搜索用时 31 毫秒
41.
A neutral dinuclear compound Cu2[(O=PPh2)2N]2(μ-O2PPh2)2 has been unexpec- tedly prepared from the reaction of [Cu2(dppa)2(MeCN)4](ClO4)2 (dppa = bis(diphenylphosphino)- amine) and Sn(edt)2 (edt = ethane-1,2-dithiolate) in dichloromethane in air. ESR spectrum shows that the original Cu+ ion has been oxidized. The crystal structure determined by an X-ray single diffrac- tometer displays that the concurrence of the redox and hydrolysis of the origin ligand dppa is taken with the formation of two new ligands. The complex crystallizes in triclinic, space group P with a = 9.4269(13), b = 10.7522(13), c = 16.787(2)(A), ( = 92.042(5), β = 104.591(7), γ = 96.167(6)°, V = 1633.6(4)(A)3, C72H60 Cu2N2O8P6, Mr = 1394.12, Z = 1, Dc = 1.419 g/cm3, F(000) = 718, μ = 0.856 mm-1, the final R = 0.0530 and wR = 0.1096 for 4210 observed reflections with I > 2σ(I).  相似文献   
42.
The title compound, [{Na(H2O)3}2{Ru(dmso)3}2(MoO4)3]·3H2O, has been obstructure was determined by single-crystal X-ray diffraction method. The crystal crystallizes in the triclinic system, space group P1 with a = 12.3333(3), b = 12.6289(3), c = 32.0284(14)(A), α =79.873(7), β = 87.549(9), y = 64.500(4)°, V = 4429.5(2) (A)3, Z = 4, Mr = 1358.85, Dc = 2.038g/cm3, F(000) = 2696 and μ = 1.874 mm-1. The compound contains a novel pentanuclear triangle bipyramidal core, [{ Ru(dmso)3 } 2(MoO4)3]2-, which consists of two { Ru(dmso)3 } 2+ fragments and three {μ2-MoO4}2- units. Furthermore, the dmso ligands bridge the pentanuclear [Ru2Mo3] core and two [Na(H2O)3]+ fragments together, forming a neutral heptanuclear ruthenium- and sodiumcontaining polyoxomolybdate.  相似文献   
43.
A new thiostannate,[tmdpH2]Sn3S7 1(tmdp = 4,4'-trimethylenedipiperidine),has been synthesized under solvothermal conditions and characterized by elemental analysis,IR spectroscopy,and single-crystal X-ray diffraction analysis.In 1,the Sn3S4 secondary incomplete cubane-like building units are bridged by μ2-S atoms to form Sn12S12 rings which are then joined parallelly to the [001] plane,giving the final 2D(Sn3S72-)n layer of(6,3) network.The layers are stacked along the c axis so that 24-membered ring channels are generated,in which the organic cations are accommodated.The compound crystallizes in monoclinic,space group C2/c,with a=23.052(3),b=13.4039(12),c=18.412(2),β=120.112(4)°,V=4921.3(9)3,C13H28N2S7Sn3,Mr=792.86,Z=8,Dc=2.140 g/cm3,F(000)=3056,μ=3.619 mm-1,the final R=0.0488 and wR=0.1125 for 4607 observed reflections with I2σ(I).  相似文献   
44.
采用丙烯酰胺为偶合剂,以Fe2+/H2O2为引发剂,将邻甲酚红通过表面接枝聚合固定于交联聚乙烯醇膜表面,制备了一种可用于光化学pH传感器的pH敏感膜。性能测试表明,此膜具有pH响应范围宽(pH7.97~12.26)、响应时间快(<25s)、耐盐性好、可逆重复性及光和贮存稳定性良好,制备方法简单的优点。实验表明,此膜可用于光化学pH传感器。  相似文献   
45.
A chiral salency complex,[Mn(Salency)(H2O)2](PF6)·2H2O 1(Salency =(R,R)-N,N'-bis(salicylidene)-1,2-cyclohexanediamine),has been prepared by the reaction of Mn(CH3COO)3·2H2O with Salency and NH4PF6,and was established by X-ray diffraction techniques.The complex crystallizes in triclinic,space group P1 with a=9.299(8),b=10.012(8),c=13.461(11),α=92.037(15),β=92.974(12),γ=93.530(18)°,V=1248.3(18)3,C20H28F6MnN2O6P,Mr = 592.35,Z=2,Dc=1.038 g/cm3,F(000)=608,μ=0.676 mm-1,the final R=0.0651 and wR=0.1880 for 5260 observed reflections with I 2σ(I).  相似文献   
46.
In this study, we have developed two new L-tryptophan based contrast agents [Gd(Try-TTDA)(H(2)O)](2-) and [Gd(Try-ac-DOTA)(H(2)O)](-). Upon addition of Cu(II) to [Gd(Try-TTDA)(H(2)O)](2-), significant increases in the relaxivity (r(1)) and hydration number of [Gd(Try-TTDA)(H(2)O)](2-) were observed. However, it only induced a minute increase in the relaxivity (r(1)) in the case of [Gd(Try-ac-DOTA)(H(2)O)](-). Furthermore, the interaction of Cu(II) with the indole ring of Gd(III) complexes was explored by measuring the intrinsic fluorescence of the tryptophan of the Gd(III) complex. With the addition of one equivalent of Cu(II) to [Gd(Try-TTDA)(H(2)O)](2-) the indole fluorescence was completely quenched. Moreover, the [Gd(Try-TTDA)(H(2)O)](2-) complex shows excellent selectivity towards Cu(II) over other metal ions (Cu(II) > La(III) > Mg(II)). Importantly, the significant signal intensity (2073 ± 67) for in vitro MR imaging using [Gd(Try-TTDA)(H(2)O)](2-) in the presence of Cu(II) implicates that this new smart contrast agent ([Gd(Try-TTDA)(H(2)O)](2-)) can serve as a Cu(II) sensor for MR imaging.  相似文献   
47.
Two one-dimensional chain-like cyanide-bridged compounds, [Fe(Phen)2(CN)2Ni(Cyclam)](ClO4)2·DMF-2H2O 1 (Cyclam = 1,4,8,11-tetraaza-cyclotetradecane, Phen = 1,10-phenanthroline, and DMF = N,N-dimethylformamide) and [Fe(Phen)2(CN)2Zn(Cyclam)](PF6)2·CH3CN 2, were prepared by the reaction of [Fe(Phen)2(CN)2]·2H2O with M(Cyclam)^2+ (M = Ni, Zn). In complexes 1 and 2, the metal atoms are connected alternatively with CN groups. X-ray structure and IR analyses for 1 and 2 were performed. Structure analysis revealed that both complexes are centrosymmetric and the geometry around each metal atom is an octahedron. The two complexes crystallize in triclinic with space group of P^1-. For 1, a = 10.439(4), b = 14.976(7), c = 15.914(8)A,α = 83.168(15), β = 74.338(15), γ = 78.023(15)°, V = 2338.3(18)A^3, Z = 2, Mr = 1035.37, Dc = 1.471 g/cm^3, F(000) = 1076,μ = 0.895 mm^-1, the final R = 0.0616 and wR = 0.1414 for 5849 observed reflections (1 〉 2σ(I)). For 2, a = 9.656(6), b = 15.404(9), c = 15.822(10)A, α = 78.68(2), β= 78.917(19), γ = 77.15(2)°, V = 2223(2)A^3, Z = 2, Mr = 1064.87, Dc = 1.587 g/cm^3, F(000) = 1078,μ = 1.032 mm^-1, the final R = 0.0672 and wR = 0.1595 for 6819 observed reflections (I 〉 2σ(I)).  相似文献   
48.
In this study we demonstrate that electrospray-assisted laser desorption ionization (ELDI) mass spectrometry (MS) can be used to rapidly characterize major chemical components on the surfaces of different solids under ambient conditions. The major chemical components in (a) dried milks with different fat contents, (b) different color-regions of a painting, (c) the thin coating on a compact disc, (d) drug tablets, and (e) porcine brain tissue were rapidly characterized as protonated molecules [M+H](+) or sodiated molecules [M+Na](+) by ELDI-MS with minimum sample pretreatment. The ionized ions of synthetic polymer and dye standards were detected directly from dried sample solutions using either positive or negative ion mode. Further structural information for the FD&C Red dye was obtained through tandem mass spectrometric (MS/MS) analysis using an ion trap mass analyzer attached to the ELDI source.  相似文献   
49.
Yang GD  Dai JC  Lian YX  Wu WS  Lin JM  Hu SM  Sheng TL  Fu ZY  Wu XT 《Inorganic chemistry》2007,46(19):7910-7916
Two new compounds, [Ph3PCH2Ph]2[Zn3(tp)3Cl2] (1) and Ni3(tma)2(H2O)8 (2) (tp = terephthalate, tma = trimesate), are metal-polycarboxylate coordination polymers prepared by similar hydrothermal synthesis techniques. X-ray single-crystal structural analysis shows that both compounds crystallize in the 2D claylike lamellar architectures, in which 1 possesses the interlayer [Ph3PCH2Ph]+ exchangeable cation and has been confirmed by PXRD patterns. 1 (C74H56Cl2O12P2Zn3) belongs to monoclinic P21/c, Z = 2 (a = 18.956(1) A, b = 10.2697(5) A, c = 17.067(1) A, beta = 99.486(4) degrees ). 2 (C18H22O20Ni3) is attributed to triclinic P, Z = 1 (a = 6.6643(8) A, b = 9.622(1) A, c = 10.089(1) A, alpha = 112.675(2) degrees , beta = 94.007(1) degrees, gamma = 106.411(2) degrees ). Linear metal trinuclear clusters bridged by rigid linear tp ligands for 1 and trigonal tma ligands for 2 give rise to a novel 2D 6-linked (3,6) topological anionic network in 1 and an interesting 2D 3,6-linked molybdenite topological neutral network in 2, respectively. Both compounds exhibit intense fluorescent emission bands at 410 nm (lambda(exc) = 355 nm) for 1 and 398 nm (lambda(exc) = 300 nm) for 2 in the solid state at room temperature.  相似文献   
50.
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