全文获取类型
收费全文 | 16041篇 |
免费 | 2368篇 |
国内免费 | 1129篇 |
专业分类
化学 | 1575篇 |
晶体学 | 149篇 |
力学 | 2683篇 |
综合类 | 263篇 |
数学 | 9173篇 |
物理学 | 5695篇 |
出版年
2024年 | 24篇 |
2023年 | 131篇 |
2022年 | 235篇 |
2021年 | 242篇 |
2020年 | 369篇 |
2019年 | 341篇 |
2018年 | 307篇 |
2017年 | 444篇 |
2016年 | 496篇 |
2015年 | 360篇 |
2014年 | 633篇 |
2013年 | 1178篇 |
2012年 | 788篇 |
2011年 | 828篇 |
2010年 | 748篇 |
2009年 | 905篇 |
2008年 | 985篇 |
2007年 | 1073篇 |
2006年 | 1021篇 |
2005年 | 943篇 |
2004年 | 818篇 |
2003年 | 846篇 |
2002年 | 758篇 |
2001年 | 667篇 |
2000年 | 618篇 |
1999年 | 593篇 |
1998年 | 466篇 |
1997年 | 411篇 |
1996年 | 326篇 |
1995年 | 245篇 |
1994年 | 205篇 |
1993年 | 208篇 |
1992年 | 154篇 |
1991年 | 130篇 |
1990年 | 124篇 |
1989年 | 71篇 |
1988年 | 95篇 |
1987年 | 77篇 |
1986年 | 65篇 |
1985年 | 94篇 |
1984年 | 82篇 |
1983年 | 40篇 |
1982年 | 62篇 |
1981年 | 63篇 |
1980年 | 42篇 |
1979年 | 52篇 |
1978年 | 50篇 |
1977年 | 45篇 |
1976年 | 28篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
131.
Lokenath Debnath 《Journal of Mathematical Analysis and Applications》2007,333(1):164-190
This paper deals with recent developments of linear and nonlinear Rossby waves in an ocean. Included are also linear Poincaré, Rossby, and Kelvin waves in an ocean. The dispersion diagrams for Poincaré, Kelvin and Rossby waves are presented. Special attention is given to the nonlinear Rossby waves on a β-plane ocean. Based on the perturbation analysis, it is shown that the nonlinear evolution equation for the wave amplitude satisfies a modified nonlinear Schrödinger equation. The solution of this equation represents solitary waves in a dispersive medium. In other words, the envelope of the amplitude of the waves has a soliton structure and these envelope solitons propagate with the group velocity of the Rossby waves. Finally, a nonlinear analytical model is presented for long Rossby waves in a meridional channel with weak shear. A new nonlinear wave equation for the amplitude of large Rossby waves is derived in a region where fluid flows over the recirculation core. It is shown that the governing amplitude equations for the inner and outer zones are both KdV type, where weak nonlinearity is balanced by weak dispersion. In the inner zone, the nonlinear amplitude equation has a new term proportional to the 3/2 power of the difference between the wave amplitude and the critical amplitude, and this term occurs to account for a nonlinearity due to the flow over the vortex core. The solution of the amplitude equations with the linear shear flow represents the solitary waves. The present study deals with the lowest mode (n=1) analysis. An extension of the higher modes (n?2) of this work will be made in a subsequent paper. 相似文献
132.
设Λ={λn}n∞=1为正的实数数列,且当n→∞时,有λn↘0.本文给出了当λn≤Mn-1/2,n=1,2,…,(其中M>0为一正常数)时Müntz系统{xλn}的有理函数在Lp[0,1]空间的逼近速度,主要结论为Rn(f,Λ) Lp≤CMω(f,n-1/2)Lp,1≤p≤∞. 相似文献
133.
Andreas Rößler 《BIT Numerical Mathematics》2006,46(1):97-110
A general class of stochastic Runge–Kutta methods for Itô stochastic differential equation systems w.r.t. a one-dimensional Wiener process is introduced. The colored rooted tree analysis is applied to derive conditions for the coefficients of the stochastic Runge–Kutta method assuring convergence in the weak sense with a prescribed order. Some coefficients for new stochastic Runge–Kutta schemes of order two are calculated explicitly and a simulation study reveals their good performance. 相似文献
134.
By using the averaging technique, we obtain new oscillation criteria for second order delay differential equation with nonlinear neutral term. These results generalize and improve some known results about neutral delay differential equation of second order. 相似文献
135.
In the present paper, we study the rate of convergence in simultaneous approximation for the Bézier variant of the Baskakov-Beta operators by using the decomposition technique of functions of bounded variation. 相似文献
136.
This paper considers the general synchronization dynamics of coupled Van der Pol–Duffing oscillators. The linear and nonlinear stability analysis on the synchronization process is derived through the Whittaker method and the Floquet theory in addition to the multiple time scales method. A stability map displaying different dynamical states of the system is performed. Numerical simulation is carried out to support and to complement the accuracy of the analytical treatment. 相似文献
137.
Xin Tao YE Chong LI 《数学学报(英文版)》2007,23(1):65-76
The BCQ and the Abadie CQ for infinite systems of convex inequalities in Banach spaces are characterized in terms of the upper semi-continuity of the convex cones generated by the subdifferentials of active convex functions. Some relationships with other constraint qualifications such as the CPLV and the Slate condition are also studied. Applications in best approximation theory are provided. 相似文献
138.
Two different problems are proposed as approximations of the usual system modelling natural convection under the Oberbeck-Boussinesq assumptions. The error is evaluated by means of the norm of its gradient in the Hilbert space. The average Nusselt number is also estimated. 相似文献
139.
Andreas Rößler 《BIT Numerical Mathematics》2007,47(3):657-680
The weak approximation of the solution of a system of Stratonovich stochastic differential equations with a m–dimensional Wiener process is studied. Therefore, a new class of stochastic Runge–Kutta methods is introduced. As the main
novelty, the number of stages does not depend on the dimension m of the driving Wiener process which reduces the computational effort significantly. The colored rooted tree analysis due
to the author is applied to determine order conditions for the new stochastic Runge–Kutta methods assuring convergence with
order two in the weak sense. Further, some coefficients for second order stochastic Runge–Kutta schemes are calculated explicitly.
AMS subject classification (2000) 65C30, 65L06, 60H35, 60H10 相似文献
140.
In general, we will use the numerical differentiation when dealing with the differential equations. Thus the differential equations can be transformed into algebraic equations and then we can get the numerical solutions. But as we all have known, the numerical differentiation process is very sensitive to even a small level of errors. In contrast it is expected that on average the numerical integration process is much less sensitive to errors. In this paper, based on the Sinc method we provide a new method using Sinc method incorporated with the double exponential transformation based on the interpolation of the highest derivatives (SIHD) for the differential equations. The error in the approximation of the solution is shown to converge at an exponential rate. The numerical results show that compared with the exiting results, our method is of high accuracy, of good convergence with little computational efforts. It is easy to treat nonhomogeneous mixed boundary condition for our method, which is unlike the traditional Sinc method. 相似文献