全文获取类型
收费全文 | 89篇 |
免费 | 0篇 |
专业分类
化学 | 69篇 |
数学 | 3篇 |
物理学 | 17篇 |
出版年
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2013年 | 1篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 1篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有89条查询结果,搜索用时 671 毫秒
81.
82.
83.
84.
85.
86.
Abbasi A Risberg ED Eriksson L Mink J Persson I Sandström M Sidorov YV Skripkin MY Ullström AS 《Inorganic chemistry》2007,46(19):7731-7741
The octakis(DMSO) (DMSO = dimethylsulfoxide) neodymium(III), samarium(III), gadolinium(III), dysprosium(III), erbium(III), and lutetium(III) iodides crystallize in the monoclinic space group P21/n (No. 14) with Z = 4, while the octakis(DMSO) iodides of the larger lanthanum(III), cerium(III), and praseodymium(III) ions crystallize in the orthorhombic space group Pbca (No. 61), Z = 8. In all [Ln(OS(Me2)8]I3 compounds the lanthanoid(III) ions coordinate eight DMSO oxygen atoms in a distorted square antiprism. Up to three of the DMSO ligands were found to be disordered and were described by two alternative configurations related by a twist around the metal-oxygen (Ln-O) bond. To resolve the atomic positions and achieve reliable Ln-O bond distances, complete semirigid DMSO molecules with restrained geometry and partial occupancy were refined for the alternative sites. This disorder model was also applied on previously collected data for the monoclinic octakis(DMSO)yttrium(III) iodide. At ambient temperature, the eight Ln-O bond distances are distributed over a range of about 0.1 A. The average value increases from Ln-O 2.30, 2.34, 2.34, 2.36, 2.38, 2.40 to 2.43 A (Ln = Lu, Er, Y, Dy, Gd, Sm, and Nd) for the monoclinic [Ln(OSMe2)8]I3 structures, and from 2.44, 2.47 to 2.49 A (Ln = Pr, Ce, and La) for the orthorhombic structures, respectively. The average of the La-O and Nd-O bond distances remained unchanged at 100 K, 2.49 and 2.43 A, respectively. Despite longer bond distances and larger Ln-O-S angles, the cell volumes are smaller for the orthorhombic structures (Ln = Pr, Ce, and La) than for the monoclinic structure with Ln = Nd, showing a more efficient packing arrangement. Raman and IR absorption spectra for the [Ln(OS(CH3)2)8]I3 (Ln = La, Ce, Pr, Nd, Gd, Tb, Dy, Er, Lu, and Y) compounds, also deuterated for La and Y, have been recorded and analyzed by means of normal coordinate methods. The force constants for the Ln-O and S-O stretching modes in the complexes increase with decreasing Ln-O bond distance and show increasing polarization of the bonds for the smaller and heavier lanthanoid(III) ions. 相似文献
87.
The solubility in the CuBr2-NR4Br-H2O (R = Me, Et, n-Bu) ternary systems at 25°C was determined by the isothermal saturation method. Comparative analysis of the phase equilibria diagrams was done. The results obtained were interpreted in terms of the competition of two processes, association of tetraalkylammonium salts and copper(II) complex formation in water-salt systems. 相似文献
88.
W Hu S Bouaziz E Skripkin A Kettani 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,139(1):181-185
A novel 1H-13C correlated two-dimensional experiment, CT-HMQC-J, for the measurement of three-bond proton-phosphorus coupling constants in 13C-labeled DNA is described. The experiment is based on the intensity difference of 1H-13C cross peaks in the presence and absence of the proton-phosphorus coupling interaction during the constant-time period in HMQC experiment. The 3J(H, P) coupling constants can be easily extracted from the intensity ratios of the two experiments. The method has been applied to a uniformly 13C, 15N-labeled d(GGAGGAT) 7-mer DNA sample. The proton-phosphorus coupling constants determined from CT-HMQC-J, together with the other three-bond coupling constants, are used to determine beta and epsilon torsion angles. The introduction of beta and epsilon restraints has improved the convergence as well as the quality of d(GGAGGAT) structure. 相似文献
89.
Liubov V. Stepakova Mikhail Yu. Skripkin Lyudmila V. Chernykh Galina L. Starova Lszl Hajba Jnos Mink Magnus Sandstrm 《Journal of Raman spectroscopy : JRS》2008,39(1):16-31
Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching CuII X modes in the equatorial plane, were found in the ranges 247–288 cm−1 for X = Cl, and 173–189 cm−1 for X = Br, while the low‐wavenumber stretching modes for the weaker axial Cu X interactions varied considerably. The tetrahedral coordination for Cs2CuCl4 and Cs2CuBr4 leads to somewhat lower Cu X symmetric stretching wavenumbers, 295 and 173 cm−1, respectively. The assignments of the copper–ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged Cu X stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn–Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer‐sphere cations. Force constant ratios for terminal and bridging metal–halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M2X6 species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr3 (K2Cu2Br6), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu2Br6]2− complexes held together by weak axial Cu Br interactions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献