全文获取类型
收费全文 | 10855篇 |
免费 | 2495篇 |
国内免费 | 670篇 |
专业分类
化学 | 1637篇 |
晶体学 | 56篇 |
力学 | 2774篇 |
综合类 | 143篇 |
数学 | 2479篇 |
物理学 | 6931篇 |
出版年
2024年 | 19篇 |
2023年 | 111篇 |
2022年 | 171篇 |
2021年 | 221篇 |
2020年 | 323篇 |
2019年 | 282篇 |
2018年 | 277篇 |
2017年 | 356篇 |
2016年 | 385篇 |
2015年 | 321篇 |
2014年 | 595篇 |
2013年 | 695篇 |
2012年 | 687篇 |
2011年 | 803篇 |
2010年 | 641篇 |
2009年 | 662篇 |
2008年 | 736篇 |
2007年 | 725篇 |
2006年 | 678篇 |
2005年 | 656篇 |
2004年 | 617篇 |
2003年 | 575篇 |
2002年 | 453篇 |
2001年 | 437篇 |
2000年 | 356篇 |
1999年 | 281篇 |
1998年 | 262篇 |
1997年 | 230篇 |
1996年 | 179篇 |
1995年 | 197篇 |
1994年 | 147篇 |
1993年 | 148篇 |
1992年 | 127篇 |
1991年 | 133篇 |
1990年 | 87篇 |
1989年 | 101篇 |
1988年 | 80篇 |
1987年 | 56篇 |
1986年 | 30篇 |
1985年 | 30篇 |
1984年 | 33篇 |
1983年 | 15篇 |
1982年 | 28篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 4篇 |
1973年 | 6篇 |
1971年 | 6篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
91.
92.
In this paper, we firstly establish the existence theorem of the global weak solutions of the Cauchy problem for the shallow water wave model of moderate amplitude, then following the idea in Xin and Zhang’s work (see Xin and Zhang, 2002), we prove the uniqueness of global weak solutions using the localization analysis in the transport equation theory. Finally, several travelling wave solutions are derived. 相似文献
93.
A waveguide occupies infinite strip with one or several narrows on a two-dimensional (2D) plane and is governed by the Helmholtz equation with Dirichlet boundary condition. On the waveguide continuous spectrum, which coincides with a half-axis, a scattering matrix is defined. At each point of the continuous spectrum this matrix has finite size, which changes at thresholds. The thresholds form a sequence of positive numbers increasing to infinity. Approximate calculation of the scattering matrix in a threshold vicinity requires special treatment. We discuss and compare two methods of numerical approximation to the scattering matrix near a threshold. 相似文献
94.
We construct analytical solutions for a system composed of a reaction–diffusion equation coupled with a purely diffusive equation. The question is to know if the traveling wave solutions of the reaction–diffusion equation can generate a traveling wave for the diffusion equation. Our motivation comes from the calcic wave, generated after fertilization within the egg cell endoplasmic reticulum, and propagating within the egg cell. We consider both the monostable (Fisher–KPP type) and bistable cases. We use a piecewise linear reaction term so as to build explicit solutions, which leads us to compute exponential tails whose exponents are roots of second-, third-, or fourth-order polynomials. These raise conditions on the coefficients for existence of a traveling wave of the diffusion equation. The question of positivity and monotonicity is only partially answered. 相似文献
95.
Le Thi Phuong Ngoc Nguyen Anh Triet Alain Pham Ngoc Dinh 《Numerical Functional Analysis & Optimization》2017,38(9):1173-1207
In this paper, we consider a wave equation with integral nonlocal boundary conditions of memory type. First, we establish two local existence theorems by using Faedo–Galerkin method and standard arguments of density. Next, we give a su?cient condition to guarantee the global existence and exponential decay of weak solutions. Finally, we present numerical results. 相似文献
96.
General decay of solutions of a wave equation with memory term and acoustic boundary condition 下载免费PDF全文
In this paper, the global solvability to the mixed problem involving the wave equation with memory term and acoustic boundary conditions for non‐locally reacting boundary is considered. Moreover, the general decay of the energy functionality is established by the techniques of Messaoudi. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
97.
On the decay and blow‐up of solution for coupled nonlinear wave equations with nonlinear damping and source terms 下载免费PDF全文
In this work, we consider a nonlinear coupled wave equations with initial‐boundary value conditions and nonlinear damping and source terms. Under suitable assumptions on the damping terms and source terms and initial data in the stable set, we obtain that the decay estimates of the energy function is exponential or polynomial by using Nakao's method. By using the energy method, we obtain the blow‐up result of solution with some positive or nonpositive initial energy. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
98.
Ivan C. Christov Christo I. Christov 《Mathematical Methods in the Applied Sciences》2017,40(12):4481-4492
We investigate the propagation of infinitesimal harmonic mechanical waves emitted from a boundary with variable velocity and arriving at a stationary observer. In the classical Doppler effect, Xs(t)=vt is the location of the source with constant velocity v. In the present work, however, we consider a source co‐located with a moving boundary x=Xs(t), where Xs(t) can have an arbitrary functional form. For ‘slowly moving’ boundaries (i.e., ones for which the timescale set by the mechanical motion is large in comparison to the inverse of the frequency of the emitted wave), we present a multiple‐scale asymptotic analysis of the moving boundary problem for the linear wave equation. We obtain a closed‐form leading‐order (with respect to the latter small parameter) solution and show that the variable velocity of the boundary results not only in frequency modulation but also in amplitude modulation of the received signal. Consequently, our results extend the applicability of two basic tenets of the theory of a moving source on a stationary domain, specifically that (i) for non‐uniform boundary motion can be inserted in place of the constant velocity v in the classical Doppler formula and (ii) that the non‐uniform boundary motion introduces variability in the amplitude of the wave. The specific examples of decelerating and oscillatory boundary motion are worked out and illustrated. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
99.
Exact boundary controllability for 1‐D quasilinear wave equations with dynamical boundary conditions 下载免费PDF全文
Yue Wang Günter Leugering Tatsien Li 《Mathematical Methods in the Applied Sciences》2017,40(10):3808-3820
By equivalently replacing the dynamical boundary condition by a kind of nonlocal boundary conditions, and noting a hidden regularity of solution on the boundary with a dynamical boundary condition, a constructive method with modular structure is used to get the local exact boundary controllability for 1‐D quasilinear wave equations with dynamical boundary conditions. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
100.
In this paper, we consider an abstract wave equation in the presence of memory. The viscoelastic kernel g(t) is subject to a general assumption , where the function H(·)∈C1(R+) is positive, increasing and convex with H(0)=0. We give the decay result as a solution to a given nonlinear dissipative ODE governed by the function H(s). Copyright © 2017 John Wiley & Sons, Ltd. 相似文献