全文获取类型
收费全文 | 162篇 |
免费 | 27篇 |
国内免费 | 8篇 |
专业分类
化学 | 2篇 |
力学 | 12篇 |
数学 | 153篇 |
物理学 | 30篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 10篇 |
2013年 | 25篇 |
2012年 | 5篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 19篇 |
2008年 | 19篇 |
2007年 | 18篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1988年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有197条查询结果,搜索用时 15 毫秒
101.
Maria Santos Bruzón Nail H. Ibragimov 《Journal of Mathematical Analysis and Applications》2009,357(1):307-313
In this work we consider a class of fourth-order nonlinear partial differential equation containing several un-specified coefficient functions of the dependent variable which encapsulates various mathematical models used, e.g. for describing the dynamics of thin liquid films. We determine the subclasses of these equations which are self-adjoint. By using a general theorem on conservation laws proved by one of the authors (NHI) we find conservation laws for some of these partial differential equations without classical Lagrangians. 相似文献
102.
In [1], [2], [3], [4], [5], [6] and [7], it is very difficult to deal with initial boundary value conditions. In this paper, we give a new method to deal with boundary value conditions, the main contribution of this paper is to put mixed boundary value conditions into reproducing kernel Hilbert space. The numerical examples are studied to demonstrate the accuracy of the present method. Results obtained by the method indicate the method is simple and effective. 相似文献
103.
A. Doicu T. Trautmann 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(8):464-476
We formulate the adjoint radiative transfer for a pseudo-spherical atmosphere and various retrieval scenarios. The single scattering radiance is computed in a spherical atmosphere by using the source integration technique, while for the multiple scattering radiance we formulate an one-dimensional adjoint radiative transfer equation in a plane-parallel atmosphere. The adjoint solution of the radiative transfer equation is obtained by employing the discrete ordinate method with matrix exponential. We provide an abbreviated derivation of our formalism as well as a discussion of the numerical implementation of the theory. 相似文献
104.
获取声辐射模态伴随系数是基于声辐射模态理论进行主动结构声控制(ASAC)的重要环节。以往PVDF分布式传感器的设计难点是振速展开受边界条件的限制,其设计过程往往是针对特定边界条件展开的。本文在声辐射模态理论和两维分布式传感器的压电方程的基础上,将板表面振速分布用Legendre多项式展开,给出了两维板结构的PVDF传感器形状与边界条件无关的设计方法。这样设计得到的传感器能应用于任意边界条件和任意振速分布的两维板结构,且实时性好,拓宽了其应用范围。本文还分别以固定边界条件板及在该板中任取一小区域两种情况为例,证明了该设计方法的可行性。 相似文献
105.
本文考虑了波驱动通量对磁场位形以及电子密度和温度的空间分布的依赖,应用伴随关系,计算了低混杂波驱动的等离子体电导率的空间分布。结果表明,注入功率谱对电导率空间分布的影响相当敏感,等离子体环外侧的电导率略高于内侧的电导率。但是不论在外侧或内侧,随着离子电荷数增大,波驱动的等离子体电导率降低,而它与斯必泽-亥姆电导率之比却增大。 相似文献
106.
The problem of oceanographic state estimation, by means of an ocean general circulation model (GCM) and a multitude of observations, is described and contrasted with the meteorological process of data assimilation. In practice, all such methods reduce, on the computer, to forms of least-squares. The global oceanographic problem is at the present time focussed primarily on smoothing, rather than forecasting, and the data types are unlike meteorological ones. As formulated in the consortium Estimating the Circulation and Climate of the Ocean (ECCO), an automatic differentiation tool is used to calculate the so-called adjoint code of the GCM, and the method of Lagrange multipliers used to render the problem one of unconstrained least-squares minimization. Major problems today lie less with the numerical algorithms (least-squares problems can be solved by many means) than with the issues of data and model error. Results of ongoing calculations covering the period of the World Ocean Circulation Experiment, and including among other data, satellite altimetry from TOPEX/POSEIDON, Jason-1, ERS- 1/2, ENVISAT, and GFO, a global array of profiling floats from the Argo program, and satellite gravity data from the GRACE mission, suggest that the solutions are now useful for scientific purposes. Both methodology and applications are developing in a number of different directions. 相似文献
107.
David E. Gilsinn 《Nonlinear dynamics》2007,50(1-2):73-92
In this paper, we prove a result that says: Given an approximate solution and frequency to a periodic solution of an autonomous
delay differential equation that satisfies a certain noncriticality condition, there is an exact periodic solution and frequency
in a neighborhood of the approximate solution and frequency and, furthermore, numerical estimates of the size of the neighborhood
are computed. Methods are outlined for estimating the parameters required to compute the errors. An application to a Van der
Pol oscillator with delay in the nonlinear terms is given. 相似文献
108.
Simultaneous determination of source terms in a linear parabolic problem from the final overdetermination: Weak solution approach 总被引:1,自引:0,他引:1
The problem of determining the pair w:={F(x,t);T0(t)} of source terms in the parabolic equation ut=(k(x)ux)x+F(x,t) and Robin boundary condition −k(l)ux(l,t)=v[u(l,t)−T0(t)] from the measured final data μT(x)=u(x,T) is formulated. It is proved that both components of the Fréchet gradient of the cost functional can be found via the same solution of the adjoint parabolic problem. Lipschitz continuity of the gradient is derived. The obtained results permit one to prove existence of a quasi-solution of the considered inverse problem, as well as to construct a monotone iteration scheme based on a gradient method. 相似文献
109.
该文给出由常挠率运动曲线生成曲面上的贝克隆变换,其中运动曲线的曲率满足修正KdV方程,从而得到著名的对于修正KdV方程贝克隆变换的一个几何实现.作为应用,取圆柱面作为种子曲面,构造了一些由周期运动曲线生成的新曲面,其中周期运动曲线在xy平面上的投影是闭曲线. 相似文献
110.