全文获取类型
收费全文 | 59326篇 |
免费 | 7277篇 |
国内免费 | 6074篇 |
专业分类
化学 | 13119篇 |
晶体学 | 993篇 |
力学 | 11078篇 |
综合类 | 1041篇 |
数学 | 27478篇 |
物理学 | 18968篇 |
出版年
2024年 | 125篇 |
2023年 | 615篇 |
2022年 | 1132篇 |
2021年 | 1275篇 |
2020年 | 1572篇 |
2019年 | 1421篇 |
2018年 | 1464篇 |
2017年 | 1994篇 |
2016年 | 2249篇 |
2015年 | 1756篇 |
2014年 | 3057篇 |
2013年 | 4138篇 |
2012年 | 3465篇 |
2011年 | 4023篇 |
2010年 | 3443篇 |
2009年 | 3946篇 |
2008年 | 3823篇 |
2007年 | 3920篇 |
2006年 | 3571篇 |
2005年 | 3354篇 |
2004年 | 2806篇 |
2003年 | 2549篇 |
2002年 | 2229篇 |
2001年 | 1929篇 |
2000年 | 1794篇 |
1999年 | 1601篇 |
1998年 | 1467篇 |
1997年 | 1295篇 |
1996年 | 1015篇 |
1995年 | 851篇 |
1994年 | 759篇 |
1993年 | 606篇 |
1992年 | 585篇 |
1991年 | 456篇 |
1990年 | 396篇 |
1989年 | 295篇 |
1988年 | 256篇 |
1987年 | 194篇 |
1986年 | 147篇 |
1985年 | 191篇 |
1984年 | 167篇 |
1983年 | 95篇 |
1982年 | 125篇 |
1981年 | 106篇 |
1980年 | 63篇 |
1979年 | 75篇 |
1978年 | 59篇 |
1977年 | 61篇 |
1976年 | 41篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
S. V. Tyshkevich 《Mathematical Notes》2007,81(5-6):851-853
92.
D.L. Skuratov Yu.L. Ratis I.A. Selezneva J. Pérez P. Fernández de Córdoba J.F. Urchueguía 《Applied Mathematical Modelling》2007
This paper deals with modelling the workpiece temperature field produced during the grinding process. The proposed model is given in terms of a two-dimensional boundary-value problem where the interdependence among the grinding wheel, the workpiece and the coolant is described by two variable functions in the boundary condition. An explicit integral form solution is constructed using the Laplace and Fourier transforms and the Green’s function method. 相似文献
93.
Wilson A. Cañas-Marín Julián D. Ortiz-Arango Uriel E. Guerrero-Aconcha Claudia P. Soto-Tavera 《Fluid Phase Equilibria》2007
The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, aij, and three expressions of the crossed terms of the repulsive parameter, bij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of aij and bij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations. 相似文献
94.
95.
Roderich Tumulka 《Foundations of Physics》2007,37(2):186-197
In a recent paper Conway and Kochen, Found. Phys. 36, 2006, claim to have established that theories of the Ghirardi-Rimini-Weber
(RW) type, i.e., of spontaneous wave function collapse, cannot be made relativistic. On the other hand, relativistic GRW-type
theories have already been presented, in my recent paper, J. Stat. Phys. 125, 2006, and by Dowker and Henson, J. Stat. Phys.
115, 2004. Here, I elucidate why these are not excluded by the arguments of Conway and Kochen.
相似文献
96.
L. Bergamaschi G. Gambolati G. Pini 《Journal of Computational and Applied Mathematics》2007,210(1-2):64-70
Integration of the subsurface flow equation by finite elements (FE) in space and finite differences (FD) in time requires the repeated solution to sparse symmetric positive definite systems of linear equations. Iterative techniques based on preconditioned conjugate gradients (PCG) are one of the most attractive tool to solve the problem on sequential computers. A present challenge is to make PCG attractive in a parallel computing environment as well. To this aim a key factor is the development of an efficient parallel preconditioner. FSAI (factorized sparse approximate inverse) and enlarged FSAI relying on the approximate inverse of the coefficient matrix appears to be a most promising parallel preconditioner. In the present paper PCG using FSAI, diagonal and pARMS (parallel algebraic recursive multilevel solvers) preconditioners is implemented on the IBM SP4/512 and CLX/768 supercomputers with up to 32 processors to solve underground flow problems of a large size. The results show that FSAI may allow for a parallel relative efficiency larger than 50% on the largest problems with p=32 processors. Moreover, FSAI turns out to be significantly less expensive and more robust than pARMS. Finally, it is shown that for p in the upper range may be much improved if PCG–FSAI is implemented on CLX. 相似文献
97.
等腰三角形Mindlin板的自由振动分析 总被引:2,自引:0,他引:2
提出了一种新方法来对基于 Mindlin剪切变形理论的等腰三角形板进行自由振动分析 .此方法采用了一种新的基函数并利用 pb-2 Rayleigh-Ritz边界函数得到了一种新型的 Ritz方法 .这种方法的有效性通过收敛性和对比性分析得到了证实 .数值结果表明此方法相当精确有效 . 相似文献
98.
B. M. Azizur Rahman A. K. M. Saiful Kabir Muttukrishnan Rajarajan Kenneth T. V. Grattan 《Optical and Quantum Electronics》2005,37(1-3):171-183
Modal solutions of planar photonic crystal waveguides with rectangular air-holes are presented by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, power confinements, modal hybridness, beat lengths and group velocity dispersions are shown for the fundamental and higher order modes of the quasi-TE and TM polarizations. 相似文献
99.
Yang Zuosheng 《国际流体数值方法杂志》2005,47(12):1423-1430
A complete boundary integral formulation for compressible Navier–Stokes equations with time discretization by operator splitting is developed using the fundamental solutions of the Helmholtz operator equation with different order. The numerical results for wall pressure and wall skin friction of two‐dimensional compressible laminar viscous flow around airfoils are in good agreement with field numerical methods. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
100.