全文获取类型
收费全文 | 32661篇 |
免费 | 3408篇 |
国内免费 | 1968篇 |
专业分类
化学 | 2215篇 |
晶体学 | 63篇 |
力学 | 3753篇 |
综合类 | 332篇 |
数学 | 21889篇 |
物理学 | 9785篇 |
出版年
2024年 | 58篇 |
2023年 | 328篇 |
2022年 | 322篇 |
2021年 | 469篇 |
2020年 | 896篇 |
2019年 | 883篇 |
2018年 | 826篇 |
2017年 | 791篇 |
2016年 | 907篇 |
2015年 | 774篇 |
2014年 | 1509篇 |
2013年 | 2812篇 |
2012年 | 1561篇 |
2011年 | 2050篇 |
2010年 | 1925篇 |
2009年 | 2102篇 |
2008年 | 2243篇 |
2007年 | 2203篇 |
2006年 | 1769篇 |
2005年 | 1712篇 |
2004年 | 1457篇 |
2003年 | 1384篇 |
2002年 | 1205篇 |
2001年 | 933篇 |
2000年 | 930篇 |
1999年 | 871篇 |
1998年 | 806篇 |
1997年 | 680篇 |
1996年 | 519篇 |
1995年 | 466篇 |
1994年 | 384篇 |
1993年 | 252篇 |
1992年 | 230篇 |
1991年 | 227篇 |
1990年 | 205篇 |
1989年 | 117篇 |
1988年 | 117篇 |
1987年 | 115篇 |
1986年 | 124篇 |
1985年 | 120篇 |
1984年 | 113篇 |
1983年 | 65篇 |
1982年 | 105篇 |
1981年 | 92篇 |
1980年 | 78篇 |
1979年 | 87篇 |
1978年 | 57篇 |
1977年 | 48篇 |
1976年 | 30篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
本文对具有有限时滞的泛函微分方程建立了关于依照两种测度的实际稳定性的Razumikhin型判定定理,其中未采用通常的辅助函数,且可运用多个含有状态变量x的部分变元的Lyapunov函数,得出部分变远实际稳定性的判定定理,从而改进了已有的结果。 相似文献
72.
In this paper we consider an initial boundary value problem for a reaction-diffusion equation under nonlinear and nonlocal Robin type boundary condition. Assuming the existence of an ordered pair of upper and lower solutions we establish a generalized quasilinearization method for the problem under consideration whose characteristic feature consists in the construction of monotone sequences converging to the unique solution within the interval of upper and lower solutions, and whose convergence rate is quadratic. Thus this method provides an efficient iteration technique that produces not only improved approximations due to the monotonicity of its iterates, but yields also a measure of the convergence rate. 相似文献
73.
In this paper necessary and sufficient conditions of null-controllability and approximate null-controllability are obtained for the wave equation on a half-axis. Controls solving these problems are found explicitly. Moreover, bang-bang controls solving the approximate null-controllability problem are constructed with the aid of solutions of a frequency extinguishing problem in the restricted band (−a,a) for this equation and the Markov power moment problem. 相似文献
74.
This paper gives some global and uniform convergence estimates for a class of subspace correction (based on space decomposition) iterative methods applied to some unconstrained convex optimization problems. Some multigrid and domain decomposition methods are also discussed as special examples for solving some nonlinear elliptic boundary value problems.
75.
76.
77.
We present a Darboux transformation for Tzitzeica equation associated with 3 × 3 matrix spectral problem. The explicit solution of Tzitzeica equation is obtained. 相似文献
78.
An implicit quasi-monotone second-order accurate method is proposed for analyzing the spiral Couette flow of a rarefied gas between coaxial cylinders. The basic advantages of the method over the conventional method of stationry iterations are that the former is conservative with respect to the collision integral, has a simple software implementation for any types of boundary conditions, and applies to a wide range of Knudsen numbers. 相似文献
79.
LIU Hong-Zhun PAN Zu-Liang LI Peng 《理论物理通讯》2006,46(10)
In this article, we will derive an equality, where the Taylor series expansion around ε = 0for any asymptotical analytical solution of the perturbed partial differential equation (PDE) with perturbing parameter ε must be admitted.By making use of the equality, we may obtain a transformation, which directly map the analytical solutions of a given unperturbed PDE to the asymptotical analytical solutions of the corresponding perturbed one. The notion of Lie-B(a)cklund symmetries is introduced in order to obtain more transformations. Hence, we can directly create more transformations in virtue of known Lie-B(a)cklund symmetries and recursion operators of corresponding unperturbed equation. The perturbed Burgers equation and the perturbed Korteweg-de Vries (KdV) equation are used as examples. 相似文献
80.
In this study, the nonlinear dynamic responses of a string are simulated using the Cellular Automata method based on the reflection rule. In the case of nonlinear systems, the velocity of wave propagation is not constant and depends on the amplitude. A new treatment of the dynamic time step is proposed for the Cellular Automata method considering the effect of the propagation velocity. As numerical examples, first, the dynamic responses of a string with linear characteristic are simulated using the Cellular Automata method. A typical resonance curve can be obtained. Second, the dynamic responses of a string with nonlinear characteristic are simulated using the proposed method. Some characteristic types of vibration can be obtained. It is concluded that the linear and nonlinear dynamic responses of a string may be obtained by simulation using the Cellular Automata method. 相似文献