全文获取类型
收费全文 | 309394篇 |
免费 | 2945篇 |
国内免费 | 1021篇 |
专业分类
化学 | 161895篇 |
晶体学 | 5042篇 |
力学 | 13586篇 |
综合类 | 10篇 |
数学 | 33884篇 |
物理学 | 98943篇 |
出版年
2020年 | 2395篇 |
2019年 | 2554篇 |
2018年 | 3251篇 |
2017年 | 3102篇 |
2016年 | 4896篇 |
2015年 | 3193篇 |
2014年 | 4768篇 |
2013年 | 13248篇 |
2012年 | 10104篇 |
2011年 | 12371篇 |
2010年 | 8321篇 |
2009年 | 8032篇 |
2008年 | 11175篇 |
2007年 | 11327篇 |
2006年 | 11028篇 |
2005年 | 10102篇 |
2004年 | 9270篇 |
2003年 | 8251篇 |
2002年 | 8013篇 |
2001年 | 9099篇 |
2000年 | 7057篇 |
1999年 | 5531篇 |
1998年 | 4561篇 |
1997年 | 4562篇 |
1996年 | 4310篇 |
1995年 | 4100篇 |
1994年 | 3739篇 |
1993年 | 3652篇 |
1992年 | 4137篇 |
1991年 | 4077篇 |
1990年 | 3982篇 |
1989年 | 3790篇 |
1988年 | 3843篇 |
1987年 | 3837篇 |
1986年 | 3595篇 |
1985年 | 4778篇 |
1984年 | 5080篇 |
1983年 | 4219篇 |
1982年 | 4627篇 |
1981年 | 4445篇 |
1980年 | 4358篇 |
1979年 | 4457篇 |
1978年 | 4629篇 |
1977年 | 4583篇 |
1976年 | 4677篇 |
1975年 | 4396篇 |
1974年 | 4257篇 |
1973年 | 4535篇 |
1972年 | 2877篇 |
1971年 | 2219篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
An interconnection strategy with built-in adaptive controllersis presented which achieves synchronization of scalar linearsystems: the closed-loop network forces all outputs to followthe same signal asymptotically while maintaining the open-loopcharacteristics. In the design of the output feedback controllers,no knowledge of system parameters is assumed, but each systemmust have the same poles and be high-gain-stable. The proofof the main theorem relies critically on derived systems-theoreticresults and the special system topology as a network of interconnectedsystems. The topology is explained by first solving the simplerproblem of signal synchronization. 相似文献
82.
A formulation of an implicit characteristic-flux-averaging method for the unsteady Euler equations with real gas effects is presented. Incorporation of a real gas into a general equation of state is achieved by considering the pressure as a function of density and specific internal energy. The Ricmann solver as well as the flux-split algorithm are modified by introducing the pressure derivatives with respect to density and internal energy. Expressions for calculating the values of the flow variables for a real gas at the cell faces are derived. The Jacobian matrices and the eigenvectors are defined for a general equation of state. The solution of the system of equations is obtained by using a mesh-sequencing method for acceleration of the convergence. Finally, a test case for a simple form of equation of state displays the differences from the corresponding solution for an ideal gas. 相似文献
83.
Frank W. Schmidt 《Linear and Multilinear Algebra》1991,30(3):229-230
This section appears from time to time. Contributions are invited, and should be submitted to R. C. Thompson, Mathematics Department, University of California, Santa Barbara, CA 93106. 相似文献
84.
85.
86.
Sanzhizhapov D. B. Tonevitskii Yu. V. Mognonov D. M. Doroshenko Yu. E. 《Russian Journal of Applied Chemistry》2003,76(4):619-622
New polyimidates were prepared from bisphenols and mono- and dicarboxylic acid imidoyl chlorides. The structures of the polymers were determined, and their physicochemical, chemical, and thermal properties were studied. The possibility of preparing film and compression materials with good mechanical characteristics from these polymers was examined. 相似文献
87.
Numerical studies were conducted to investigate the natural convection heat transfer around a uniformly heated thin plate
with arbitrary inclination in an infinite space. The numerical approach was based on the finite volume technique with a nonstaggered
grid arrangement. For handling the pressure–velocity coupling the SIMPLE-algorithm was used. QUICK scheme and first order
upwind scheme were employed for discretization of the momentum and energy convective terms respectively. Plate width and heating
rate were used to vary the modified Rayleigh number over the range of 4.8×106 to 1.87×108. Local and average heat transfer characteristics were compared with regarding to the inclination angle. The empirical expressions
for local and average Nusselt number were correlated. It has been found that for inclination angle less than 10∘, the flow and heat transfer characteristics are complicated and the average Nusselt number can not be correlated by one equation
while for inclination angle larger than 10∘, the average Nusselt number can be correlated into an elegant correlation.
Received on 18 April 2001 / Published online: 29 November 2001 相似文献
88.
D. Shakin 《Journal of Mathematical Sciences》2007,142(4):2302-2366
In this paper, we study the numeric characteristics (the Hilbert function and graded Betti numbers) of monomial ideals in
the polynomial ring and in the exterior algebra.
__________
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 30, Algebra,
2005. 相似文献
89.
W. G. Habashi G. Baruzzi M. F. Peeters M. M. Hafez 《Numerical Methods for Partial Differential Equations》1991,7(2):193-207
Finite element solutions of the Euler and Navier-Stokes equations are presented, using a simple dissipation model. The discretization is based on the weak-Galerkin weighted residual method and equal interpolation functions for all the unknowns are permitted. The nonlinearity is iterated upon using a Newton method and at each iteration the linear algebraic system is solved by a direct solver with all unknowns fully coupled. Results are presented for two-dimensional transonic inviscid flows and two- and three-dimensional incompressible viscous flows. Convergence of the algorithm is shown to be quadratic, reaching machine accuracy in very few iterations. The inviscid results demonstrate the existence of nonunique numerical solutions to the steady Euler equations. 相似文献
90.