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91.
92.
Doris Pospiech Hartmut Komber Dieter Voigt Dieter Jehnichen Liane Häußler Antje Gottwald Wolfram Kollig Kathrin Eckstein Angela Baier Karina Grundke 《Macromolecular Symposia》2003,199(1):173-186
The goal of the investigation presented here was to evaluate the influence of semifluorinated side chains on the bulk structure and the surface properties of polysulfones with different chain structure. Thus, segmented block copolymers consisting of polysulfone and semifluorinated aromatic polyester segments as well as polysulfones having semifluorinated side chains randomly distributed over the polymer backbone were synthesized and characterized. Oxydecylperfluorodecyl side chains were used because of their strong tendency for self-organization. The influence of the chain architecture on the self-organization as well as on the surface properties, particularly the wetting behavior, was examined. It could be shown that despite of the higher self-organizing tendency of block copolymers the surface properties of both polymer types are comparable and depend only on the concentration of side chains. 相似文献
93.
Glass Formation and Properties of Chalcogenide Systems. IX. On the Structure of GeS/GeS2 and GeSe/GeSe2 Glasses Mole volume, glass transition temperature, and coefficient of thermal expansion were measured on glasses prepared by standardized conditions. Near the composition Ge2S3 and Ge2Se3 the properties show a singularity or point of inflexion, respectively. Random models of structure are inconsistent with such a behaviour. A model of higher chemical order is proposed which can explain the observed dependence of the glass properties on composition and is in accordance with radial distribution studies. 相似文献
94.
By X-ray analysis of the hydroiodide of the 22,26-epimino-5α-cholestan-3β,20-diol (1), the constitution and configuration has been established and the side chain stereochemistry determined as 20R : 22S : 25S. The final discrepancy R was 0·167. 相似文献
95.
M. Malanin K.-J. EichhornA. Lederer P. TreppeG. Adam D. FischerD. Voigt 《Journal of chromatography. A》2009,1216(51):8939-8946
Qualitative and quantitative comparison between liquid chromatography (LC) and LC coupled with Fourier transform infrared spectroscopy (LC-FTIR) to evaluate preferential solvation phenomenon of polymers in a mixed solvent has been performed. These studies show that LC-FTIR technique leads to detailed structural information without the requirement for determination of additional parameters for quantitative analysis except calibration. Appropriate experimental conditions for preferential solvation study have been established by variation of polymer concentration, molar mass and eluent content. 相似文献
96.
"Scaffolded DNA origami" has been proven to be a powerful and efficient approach to construct two-dimensional or three-dimensional objects with great complexity. Multilayer DNA origami has been demonstrated with helices packing along either honeycomb-lattice geometry or square-lattice geometry. Here we report successful folding of multilayer DNA origami with helices arranged on a close-packed hexagonal lattice. This arrangement yields a higher density of helical packing and therefore higher resolution of spatial addressing than has been shown previously. We also demonstrate hybrid multilayer DNA origami with honeycomb-lattice, square-lattice, and hexagonal-lattice packing of helices all in one design. The availability of hexagonal close-packing of helices extends our ability to build complex structures using DNA nanotechnology. 相似文献
97.
Aldol additions of unprotected carbohydrates to 1.3-dicarbonyl compounds have been described. This transformation is based on a dual activation by tertiary amines and 2-hydroxypyridine. 相似文献
98.
Chr. Balarew S. Tepavitcharova D. Rabadjieva W. Voigt 《Journal of solution chemistry》2001,30(9):815-823
The system MgCl2–MgSO4–H2O has been investigated experimentally and modeled thermodynamically according to the Pitzer method at 50 and 75°C. It was found that, even when seemingly all requirements for reaching the stable thermodynamic equilibrium are fulfilled, the crystallization of higher hydrates as metastable phases is possible, and cannot be avoided in each crystallization field of a stable lower hydrate of magnesium sulfate. Crystallization of MgSO4 · x H2O (x = 1, 4, 6) and MgCl2 · 6 H2O at 50°C and of MgSO4 · H2O and MgCl2 · 6 H2O at 75°C as stable phases has been observed. Three metastable crystallization fields of MgSO4 · x H2O (x = 4, 6, 7) have been detected at 50°C and two of MgSO4 · x H2O (x = 4, 6) at 75°C. The results obtained and the contradictions existing in the literature with respect to the solubility and the crystallizing solid phases are discussed in terms of the crystal structures. 相似文献
99.
I. Voigt F. Simon H. Komber H.-J. Jacobasch S. Spange 《Colloid and polymer science》2000,278(1):48-56
The chemical synthesis and the physicochemical properties of stable poly(vinyl formamide-co-vinyl amine)/silica hybrid particles are presented. Copolymers of poly(vinyl formamide) (PVFA) and poly(vinyl amine) (PVAm)
and their protonated forms were adsorbed onto silica from aqueous solutions. The influences of the pH strength and the ion
concentration of the aqueous solution as well as the copolymer composition (degree of hydrolyzation of PVFA), and the molecular
mass on the adsorption process were investigated by electrokinetic measurements, potentiometric titration, and quantitative
elemental analyses. Silica surface-charge neutralization is achieved at a pH strength above 10 for highly hydrolyzed (95%)
PVFA polymers. Decreasing the amino content in the PVAm chain shifts successively both the point of zero charge and the isoelectric
point to lower pH values. PVFA-co-PVAm layers onto silica are adsorbed weakly. To fix these layers irreversibly, cross-linking reactions with (4,4′-diisocyanate)diphenyl
methane were carried out on the surface of solid PVFA-co-PVAm/silica hybrid particles suspended in acetone. The cross-linking reaction, which is connected with the conversion of
amino groups, is also a tool to control the surface charge of the PVFA-co-PVAm/silica hybrids. X-ray photoelectron spectroscopy and solid-state 13C cross-polarization magic-angle spinning NMR spectroscopy were used to obtain information on the number of and the structure
of the functionalized polyelectrolyte layers on silica. The success of cross-linking was also shown by the results of these
spectroscopic methods.
Received: 28 June 1999 /Accepted: 27 August 1999 相似文献
100.
用分子动力学方法和不同参数的指数 6势函数计算了T =30 4K的高密度氦的等温压缩线和能量分布 .给出了能精确描述高密度氦原子间相互作用的指数 6势函数优化参数 .并用优化的势函数计算了高密度氦T =30 0K和T =2 98K的等温压缩线 ,计算结果和实验值非常吻合 .进一步用优化的势函数模拟了高温高密度氦的状态方程及其结构 ,发现当把 ρ限定为 1 .6 0g /cm3 时 ,其径向分布函数的第 2个峰将在 2 0 0 0~ 30 40K区间消失 ,表明此时发生了固 液相变过程 . 相似文献