全文获取类型
收费全文 | 12682篇 |
免费 | 2642篇 |
国内免费 | 1298篇 |
专业分类
化学 | 3068篇 |
晶体学 | 171篇 |
力学 | 1451篇 |
综合类 | 153篇 |
数学 | 2141篇 |
物理学 | 9638篇 |
出版年
2024年 | 19篇 |
2023年 | 141篇 |
2022年 | 268篇 |
2021年 | 321篇 |
2020年 | 386篇 |
2019年 | 315篇 |
2018年 | 314篇 |
2017年 | 420篇 |
2016年 | 496篇 |
2015年 | 453篇 |
2014年 | 709篇 |
2013年 | 919篇 |
2012年 | 799篇 |
2011年 | 884篇 |
2010年 | 845篇 |
2009年 | 867篇 |
2008年 | 873篇 |
2007年 | 810篇 |
2006年 | 808篇 |
2005年 | 734篇 |
2004年 | 766篇 |
2003年 | 628篇 |
2002年 | 566篇 |
2001年 | 454篇 |
2000年 | 439篇 |
1999年 | 368篇 |
1998年 | 329篇 |
1997年 | 275篇 |
1996年 | 235篇 |
1995年 | 167篇 |
1994年 | 154篇 |
1993年 | 118篇 |
1992年 | 94篇 |
1991年 | 89篇 |
1990年 | 83篇 |
1989年 | 88篇 |
1988年 | 62篇 |
1987年 | 48篇 |
1986年 | 62篇 |
1985年 | 40篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
991.
By using the finite-part integral concepts and limit technique, the hypersingular integrodifferential equations of three-dimensional
(3D) planar interface crack were obtained; then the dominant-part analysis of 2D hypersingular integral was further used to
investigate the stress fields near the crack front theoretically, and the accurate formulae were obtained for the singular
stress fields and the complex stress intensity factors. After that, a numerical method is proposed to solve the hypersingular
integrodifferential equations of 3D planar interface crack, and the problem of elliptical planar crack is then considered
to show the application of the method. The numerical results obtained are satisfactory.
Project supported by the Foundation of Solid Mechanics Open Research Laboratory of State Education Commission at Tongji University
and the National Natural Science Foundation. 相似文献
992.
Both ferrofluidics and genetic algorithms are relatively new fields. Due to complex physical interactions, ferrofluidic topographies and assemblies have only been solved using finite time step, Lattice Boltzmann, and finite-element methods in very simple magnetic field configurations. In this paper, we show that it is possible (and highly advantageous) to employ genetic algorithms to solve for the fluid topographies, which can be extended to include more complex magnetic fields. 相似文献
993.
The dumbbell model with internal viscosity for a dilute polymer solution is investigated based on a balance of viscous drag and restoring Brownian forces.An approximate method is used to obtain the solution of extensional stress in closed form in the case of steady flow.For different internal viscosities,this parametric study shows different asymptotic regimes of the extensional viscosity as a function of strain rate.This analysis may explain the attenuation of pressure drop in strong flows from a phenom... 相似文献
994.
We find the existence conditions for stationary dipole and tripole surface solitons formed at the interface of a nonlocal nonlinear medium and a lattice with linearly modulated frequency. We investigate how the degree of nonlocality, the depth, and the modulation frequency of the optical lattice field affect on the existence of the surface solitons and their dynamics. The relationship between the power and the model parameters is identified. The stability of the surface dipole and tripole solitons is numerically investigated. 相似文献
995.
G. Cilpa M. T. Hyvönen A. Koivuniemi M.‐L. Riekkola 《Journal of computational chemistry》2010,31(8):1670-1680
Chondroitin‐6‐sulfate (C6S) is a glycosaminoglycan (GAG) constituent in the extracellular matrix, which participates actively in crucial biological processes, as well as in various pathological conditions, such as atherosclerosis and cancer. Molecular interactions involving the C6S chain are therefore of considerable interest. A computational model for atomistic simulation was built. This work describes the design and validation of a force field for a C6S dodecasaccharide chain. The results of an extensive molecular dynamics simulation performed with the new force field provide a novel insight into the structure and dynamics of the C6S chain. The intramolecular H‐bonds in the disaccharide linkage region are suggested to play a major role in determining the chain structural dynamics. Moreover, the unravelling of an additional H‐bond involving the sulfate groups in C6S is interesting as changes in sulfation have been claimed to be an important factor in several diseases. The force field will prove useful for future studies of crucial interactions between C6S and various nanoassemblies. It can also be used as a basis for modeling of other GAGs. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
996.
The influences of σ* and Φ mesons,temperature and coupling constants of nucleons on the moment of inertia of the proto neutron star(PNS) are examined in the framework of relativistic mean field theory for the baryon octet {n,p,Λ,Σ+,Σ0,Σ+,Ξ-,Ξ0} system.It is found that,compared with that without considering σ* and Φ mesons,the moment of inertia decreases.It is also found that the higher the temperature,the larger the incompressibility and symmetry energy coeficient,and the larger the moment of inertia of a PNS.The influence of temperature and coupling constants of the nucleons on the moment of inertia of a PNS is larger than that of the σ* and Φ mesons. 相似文献
997.
998.
《Composite Interfaces》2013,20(4):177-196
The modified null field approach to elastic P- and SV-wave scattering (in plane strain) from a partially debonded fiber has been developed. The debonded region on the fiber surface is subjected to traction free boundary conditions, whereas the fiber is assumed to be in welded contact with the host medium elsewhere. Additional null field equations for an elliptical extension of the actual surface of the scatterer are introduced which require additional expansions for the field in the region between the extended mathematical boundary and the actual boundary of the scatterer. The numerical accuracy of the modified null field method has been tested for the case of a perfectly bonded fiber for P- and SV-wave incidence. Scattering cross-section plots are presented for different degrees of debonding. 相似文献
999.
CHEMICAL STRUCTURE DEPENDENCE OF THE INTERNAL ENERGY CONTRIBUTION IN RUBBER ELASTICITY 总被引:2,自引:0,他引:2
Juan Sun Xiao-zhen Yang Polymer Physics Laboratory Center for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》2001,(5):447-449
Conformational elasticity theory recently developed has been used to explore the internal energy contribution tothe elastic force f_e/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1, 4-isoprene). Calculated f_e/f values arein good agreement with those obtained experimentally. Results show that behavior of f_e/f is mainly contributed by chemicalstructure, or intramolecular interaction, supporting the experimental observations, and that the internal energy contribution isstrain dependent. 相似文献
1000.
We design a novel X-ray image detector by lens coupling a Gd2O2S:Tb intensifying screen with a high performance low-light-level (L3,which often means luminescence less than 10-3 Lux) image intensifier.Different coupling effects on imaging performance between zoom lens and fix-focus lens are analyzed theoretically.In experiment,for designing a detector of 15-inch visual field,the system coupled by zoom lens is of 12.25-1p/cm resolution,while the one with fix-focus lens is 10 lp/cm.The superiority of zoom lens is validated.It is concluded that zoom lens preserves the image information better than fix-focus lens and improves the imaging system's performance in this design,which is referential to the design of other optical imaging systems. 相似文献