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排序方式: 共有178条查询结果,搜索用时 15 毫秒
31.
用自洽场理论方法计算了星形高分子之间的相互作用势, 并与标度理论的推测以及基于粒子的分子动力学模拟方法的结果进行了比较. 自洽场理论计算得到的星形高分子之间的二体相互作用势与标度理论推测的结果基本一致: 当两个星形高分子核心之间的距离小于其对应的等效软球的半径R时, 二体相互作用势U与星形高分子核心之间的距离d及官能度f之间的关系为U(d)∝-f 3/2 ln(d/R). 当星形高分子核心间距离较小, 相互作用势与星形高分子核心间距离的对数呈线性关系时, 三体相互作用为吸引作用, 但其强度约等于二体作用的10%. 因此, 以二体作用为基础的基于粒子的模拟方法是基本合理的. 相似文献
32.
Wei Yunhe Zhang Changqiao Ma Xiaolong Zhang Guoyu Hou Qi Wang Hongchen Sun Yuansheng 《化学物理学报(中文版)》2004,17(4):443-448
During the hot-dip process of Cu on the surface of the steel,it involves the solidification from liquid to coating. The cooling rate has great influence on the microstructure and the performance. By means of constanttemperature,constant-pressure molecular dynamics simulation technique,the solidification process of the liquid model system made of 500 Cu particles has been studied with the period boundary condition. With the pairs analysis technology and the bond orientational order method,the difference of the structure and energy of the liquid Cu model system between different cooling velocities has been compared. The significant information of microcosmic structural transformation in the solidification process of liquid Cu system has been obtained. The calculation results show that the Finnis-Sinclair(FS)potential works very well in the solidification process of Cu. Cooling slowly the crystal copper layer can be obtained. Cooling quickly the amorphous copper layer can be obtained. 相似文献
33.
34.
近年来,由于激光及微波技术的迅速发展,汤姆逊散射已日益广泛地用于等离子体的诊断,辐射散射理论也日益引起广泛的兴趣。 试探粒子模型用于计算等离子体散射谱时可以引入两个假设:试探粒子在背景粒子作 相似文献
35.
用FS多体势模型模拟金属铜的冷却过程 总被引:1,自引:1,他引:0
采用常温、常压分子动力学模拟方法模拟了在周期性边界条件下由500个原子构成的液态Cu模型系统的凝固过程,考察了不同降温速率下液态Cu的凝固行为.模拟结果很好地重现了实验值.模拟中原子间作用势采用FS势,结构分析采用双体分布函数、对分析技术、内能、均方位移等方法,得到了原子体系微观结构组态变化的重要信息,并利用能量分析的方法对体系微观结构的变化进行了说明. 相似文献
36.
37.
Frédéric Gruy 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(3):240-246
This paper presents a simple method of approximation for calculating the scattering cross section for a random orientated convex particle illuminated by a non polarized electromagnetic wave. This method is proved efficient for sphere and spheroids as the scattering efficiency is smaller than one and as the material is optically either soft or hard. 相似文献
38.
Oxidation represents one of the most important and practical chemical transformations for both organic synthesis, material science and pharmaceutical area. Among the existing strategies, molybdenum/tungsten-based heteropoly salts involved oxidations with low-cost and environmentally benign terminal oxidant and thus have attracted considerable attention in recent years. In this review, we have summarized the recent development of heteropoly salts utilized in oxidations, mainly the peroxomolybdates and peroxotungstates. We wish to highlight the progress made in the past 20 years of this field. Three categories are classified according to the aggregation state of metal oxides. Special attention is paid to the catalytically active peroxometalate species generated during the oxidation process. It is helpful to shed light on the common features that enable highly efficient and selective oxidations. We aim to inspire fellow chemists to explore more functional metalates for catalytic oxidations, especially asymmetric versions. Meanwhile, we attempt to understand the design principles for the discovery of more efficient, selective and economical catalytic systems. 相似文献
39.
Rahul R. Kolhapurkar Preeti K. Patil Dilip H. Dagade Kesharsingh J. Patil 《Journal of solution chemistry》2006,35(10):1357-1376
Experimental measurements of the speed of sound, density and osmotic vapour pressure are reported for binary 18-Crown-6 (18C6) + CH3OH, KBr + CH3OH and ternary KBr + 18C6 + CH3OH solutions at 298.15 K. The density and compressibility data were processed to obtain the apparent molar volume (ø V ) and apparent molar isentropic compressibility ( $\phi _{K_S } Experimental measurements of the speed of sound, density and osmotic vapour pressure are reported for binary 18-Crown-6 (18C6) + CH3OH, KBr + CH3OH and ternary KBr + 18C6 + CH3OH solutions at 298.15 K. The density and compressibility data were processed to obtain the apparent molar volume (?
V
) and apparent molar isentropic compressibility () of the solutes in methanol. Expansivity data were obtained for the 18C6 + CH3OH system from density data at different temperatures and were used for calculation of the isothermal compressibility values at 298.15 K. The isothermal compressibility and expansivity data are further used to obtain the apparent molar isothermal compressibility () and apparent molar expansivity (?
E
) of 18C6 in methanolic solutions and as well as the energy-volume coefficient parameter (∂ U/∂ V)
T
in methanol solutions. The volume and compressibility changes due to complexation of KBr with 18C6 are obtained at infinite dilution for ?
V
and ?
K
. The results are compared with the similar data obtained by us previously for aqueous and CCl4 solutions. The osmotic coefficient data were used to calculate activities and activity coefficients of each component at 298.15 K as a function of the concentration of binary and ternary methanolic solutions containing KBr and 18C6. The activity and activity coefficient data are used to evaluate the pair and triplet interaction parameters by making appropriate use of the McMillan-Meyer theory of solutions. The calculation of the thermodynamic equilibrium constant (K) is made using the pair interaction parameter, g
NE
(non-electrolyte – electrolyte pair interaction), for the complexation equilibria. The nature of interactions present in the CH3OH solutions is discussed. 相似文献
40.
Demetres Christofides 《Discrete Mathematics》2006,306(17):2111-2114
The pair length of a graph G is the maximum positive integer k, such that the vertex set of G can be partitioned into disjoint pairs {x,x′}, such that d(x,x′)?k for every x∈V(G) and x′y′ is an edge of G whenever xy is an edge. Chen asked whether the pair length of the cartesian product of two graphs is equal to the sum of their pair lengths. Our aim in this short note is to prove this result. 相似文献