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   426篇
  免费   86篇
  国内免费   140篇
化学   455篇
晶体学   2篇
力学   3篇
综合类   7篇
数学   17篇
物理学   168篇
  2023年   1篇
  2022年   2篇
  2021年   9篇
  2020年   1篇
  2019年   8篇
  2018年   6篇
  2017年   6篇
  2016年   5篇
  2015年   15篇
  2014年   80篇
  2013年   81篇
  2012年   60篇
  2011年   22篇
  2010年   14篇
  2009年   8篇
  2008年   28篇
  2007年   22篇
  2006年   41篇
  2005年   32篇
  2004年   31篇
  2003年   38篇
  2002年   6篇
  2001年   5篇
  2000年   11篇
  1999年   13篇
  1998年   9篇
  1997年   2篇
  1996年   6篇
  1995年   9篇
  1994年   10篇
  1993年   13篇
  1992年   10篇
  1991年   15篇
  1990年   14篇
  1989年   7篇
  1988年   9篇
  1986年   1篇
  1985年   1篇
  1981年   1篇
排序方式: 共有652条查询结果,搜索用时 0 毫秒
51.
由6,6-四亚甲基苯并富烯C9H6C(CH2)4与Ru3(CO)12在二甲苯中加热回流,合成了一个钌配合物[((η5-C9H6)C(C4H7))2Ru2(μ-CO)2(CO)2]。通过元素分析、红外、热重、核磁共振进行了表征及研究。用X射线单晶衍射法测定了[((η5-C9H6)C(C4H7))2Ru2(μ-CO)2(CO)2]的结构,结果表明:晶体属于单斜晶系,P21/c空间群,a=0.757 1(13)nm,b=1.577 7(3)nm,c=1.107 3(19)nm,β=90.07(2)°,V=1.322 6(4)nm3,Dc=1.699 g.cm-3,μ=1.179 mm-1,F(000)=676,Z=2,R1=0.030 5,wR2=0.072 4。  相似文献   
52.
本文选用一种烷氧基取代的金属酞菁化合物,溶解旋涂于玻璃基板上,分别经有机溶剂处理和加热处理,发现都可以使吸收光谱范围向长波方向拓宽。X-射线衍射研究表明:经上述方法处理后都可使染料分子的聚集程度发生变化,堆砌方式由微晶型向晶型结构转变,高分辩率扫描电镜观察进一步证实了上述结果。  相似文献   
53.
将配体[C5Me4HR](R=cyclopentyl,cyclohexyl,nPr)分别与Ru3(CO)12在二甲苯中加热回流,合成了3个新的双核配合物[(η5-C5Me4R)Ru(CO)(μ-CO)]2(R=cyclopentyl(1),cyclohexyl(2),nPr(3))。利用红外光谱、元素分析、核磁共振氢谱对它们的结构进行了表征,用X-射线单晶衍射法测定了12的结构。  相似文献   
54.
配体C9H7R(R=CH2CH2CH3 (1),CH2(CH3)2 (2),C5H9 (3),CH2C6H5 (4),CH2CH=CH2 (5))分别与Ru3(CO)12在二甲苯或庚烷中加热回流,得到了6个双核配合物[(η5-C9H6R)Ru(CO)(μ-CO)]2(R=CH2CH2CH3 (6),CH2(CH3)2 (7),C5H8 (8),CH2C6H5 (9),CH2CH=CH2 (10))和[(η5-C9H6)(H3CH2C)CHCH(CH2CH3)(η5-C9H6)] [Ru(CO)(μ-CO)]2 (11).通过元素分析、红外光谱、核磁共振氢谱对配合物的结构进行了表征,并用X-射线单晶衍射法测定了配合物6,9,1011的结构.  相似文献   
55.
A novel inorganic-organic hybrid compound, {[Co(dien)]4[0aO4)MoV8(wV10.56MoV10.44)4- O33(OH)3]}'nH20 (1, n = 1, dien = diethylenetriamine), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the triclinic system with a = 11.927(2), b = 13.328(3), c = 19.306(4)A, a = 93.76(3), β = 94.14(3), γ = 109.99(3)°, V= 2863.2(12) A3, space group P1 and Z = 2 at 173 K. The final full-matrix least-squares refinement converged to R = 0.049 for 9621 observed reflections with 1 〉 2σ(I) and wR = 0.139 for all data (9871) and S = 1.073. Crystal structure analysis shows that 1 contains a kind of the first reported mixed-valence and molybdenum-tungsten mixed-distributed e-Keggin structural polyanion capped by four Co(dien) fragments with the main group element P occupying the center site. These results were further confirmed by energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Thermogravimetry (TG) and X-ray photoelectron spectroscopy (XPS) analyses.  相似文献   
56.
Two lead(ll) compounds, [Pb(qlc)(phen)2(NO3)]e-H20 (1) and [Pb(qlc)z(phen)]-3H20 (2) (Hqlc = quinoline-3-carboxylic acid, phen = 1,10-phenanthroline), were synthesized and charac- terized by elemental analysis, single-crystal X-ray diffraction, IR and thermogravimetric analysis. Crystal 1 is of monoclinic, space group C2/c with a = 25.246(5), b = 12.543(3), c = 18.917(4) A, β = 105.77(3)°, V= 5765(2) A3, Z = 4, C68H46N12OllPb2, Mr = 1621.53, Dc = 1.886 g.cm-3,/.t(MoKa) = 5.912 mm-1, F(000) = 3152, GOOF = 1.080, the final R = 0.022 and wR = 0.0571 for 4822 observed reflections (1 〉 2a(/)). Crystal 2 is oftriclinic, space group Pi with a = 8.7883(10), b = 11.7031 (13), c = 15.9320(17) A, a = 69.9400(10), fl = 78.9780(10), 7 = 79.1650(10)°, V = 1497.4(3) A3, Z = 2, C32H26NaO7Pb, Mr. = 785.71, Dc = 1.729 g.cm-s, p(MoKa) = 5.688 mm-1, F(000) = 756, GOOF = 1.106, the final R = 0.0313 and wR = 0.088 for 59i5 observed reflections (1 〉 2σ(I)). Single-crystal X-ray diffraction analysis reveals that 1 exhibits a two-dimensional (2D) layer based on π-π stacking interactions between phen. Simultaneously, the adjacent 2D layers are assembled via π-π stacking interactions between phen and quinoline tings into a 3D supramolecular structure. The zero- dimensional structure of 2 is also further extended by π-π interactions to form a 2D supramolecular layer. Furthermore, these two compounds exhibit photoluminescence at room temperature in the solid state and their photocatalytic activities have been studied by degradation methylene blue.  相似文献   
57.
A new sandwiched polyoxometalate [HK11Cd4Cl2(PW9034)2]·18H2O (1), incor- porating a unique hybrid tetranuclear cadmium cluster (abbreviated to {Cd4}) with two trivacant polyanions [B-α-PW9O34]9-, has been hydrothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, UV-vis, and single-crystal X-ray diffraction analysis. Crystal data for 1: monoclinic, space group C2/c, a = 19.2997(4), b = 13.8014(3), c = 31.9819(8) A, β = 102.764(2)°, V= 8308.3(3) A3, Z = 4, P2O86Cl2K11Cd4W18H37, Mr = 5735.13, Dc = 4.584 mg-mm-3, F(000) = 10084, μ = 26.579 mm-1, the final R = 0.0378 and wR = 0.0989 for 6558 observed reflections (I〉 2σ(I)). X-ray crystallographic study shows that the molecular structure of 1 contains four cadmium atoms. Two CdO6 distorted octahedra and two CdOsC1 distorted octahedra combine with each other in turn via edge-sharing, resulting in a regular rhomb-like cluster sandwiched between two {B-a-PW9034} units. Further, the sandwich-type polyoxoanions were connected by K+ ions to form a complicated 3-D open-framework through connecting with each terminal O atom of the [Cd4C12(PW9O34)2]12- polyoxoanions. In addition, compound 1 exhibits photoluminescence property at room temperature and the band gap can be assessed at 3.25 eV.  相似文献   
58.
A pair of E/Z-isomers of 2-phenyl-6,7-dihydrobenzofuran-4(5H)-one O-cyanomethyl oxime,C16H14N2O2,as potential drugs for treating peptic ulcer and other acid-related diseases have been synthesized and characterized by IR,MS and NMR spectra.Meanwhile,the crystal of IIIa was obtained and determined by X-ray single-crystal diffraction.Crystal data: monoclinic system,space group P21 /c,a = 8.423(8),b = 19.596(16),c = 8.770(8),β = 107.750(12)°,V = 1379(2)3,Z = 4,F(000) = 560,Dc = 1.283 g/cm3,μ = 0.086 mm 1,R = 0.0681 and wR = 0.2029 for 14472 independent reflections(Rint = 0.0782) and 2428 observed ones(I 2σ(I)).  相似文献   
59.
Three isomeric metal-organic frameworks,[Cd2(X)(btc)(DMA)3]n(X = Cl(1),Br(2),I(3),H3btc =1,3,5-benzenetricarboxylic acid and DMA = N,Nˊ-dimethylacetamide),have been synthesized and characterized by elemental analysis,infrared spectra(IR),thermogravimetric(TG) analyses and single-crystal X-ray diffraction.Single-crystal X-ray analysis reveals that compounds 1–3 crystallize in the orthorhombic P212121 space group,and feature a three-dimensional(3D) extended framework containing dinuclear [Cd2(COO)3] units as the secondary building units(SBUs).Topological analysis reveals that compounds 1–3 can be simplified into a 3-connected srs topological network.  相似文献   
60.
A new compound [CpCo(Se2C2BIoH9)CH2C(O)C4H30] has been synthesized and characterized by elemental analysis, IR spectroscopy, NMR, MS and single-crystal X-ray diffraction. The complex crystallizes in the monoclinic system, space group P21/c with a = 10.9481(10), b = 24.6600(12), c = 25.7430(14) A, β = 100.863(3)°, C42H57B30Co306Se6"CH2C12"0.25H20, Mr = 1722.16, V = 6825.6(8) A3, Dc= 1.676 g/cm3, Z = 1 and F(000) = 3346. The molecular structure shows a 1:1 ratio product of the two reactants of 16e half-sandwich complex CpCo(Se2C2B10H10) and alkyne 1-(2-furyl)-2-propyn-l-one. The hydrogen atom in the B(3) position of CpCo(Se2C2B10HIo) has been activated and migrated to the terminal carbon of 1-(2-furyl)- 2-propyn-l-one to form the B-CH2 unit. The title compound molecules are linked and extended further into a one-dimensional chain through atypical hydrogen bonds.  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