全文获取类型
收费全文 | 3519篇 |
免费 | 258篇 |
国内免费 | 852篇 |
专业分类
化学 | 2288篇 |
晶体学 | 40篇 |
力学 | 192篇 |
综合类 | 46篇 |
数学 | 1597篇 |
物理学 | 466篇 |
出版年
2024年 | 8篇 |
2023年 | 52篇 |
2022年 | 77篇 |
2021年 | 93篇 |
2020年 | 154篇 |
2019年 | 140篇 |
2018年 | 104篇 |
2017年 | 170篇 |
2016年 | 165篇 |
2015年 | 122篇 |
2014年 | 209篇 |
2013年 | 288篇 |
2012年 | 291篇 |
2011年 | 220篇 |
2010年 | 171篇 |
2009年 | 239篇 |
2008年 | 239篇 |
2007年 | 225篇 |
2006年 | 187篇 |
2005年 | 179篇 |
2004年 | 193篇 |
2003年 | 141篇 |
2002年 | 112篇 |
2001年 | 89篇 |
2000年 | 95篇 |
1999年 | 98篇 |
1998年 | 68篇 |
1997年 | 83篇 |
1996年 | 80篇 |
1995年 | 67篇 |
1994年 | 44篇 |
1993年 | 36篇 |
1992年 | 43篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1959年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有4629条查询结果,搜索用时 15 毫秒
51.
In this paper, we investigate with a time fractional-order derivative in a three-species predator-prey model with the presence of prey social behavior. A new approximation for predator-prey interaction in the presence of prey social behavior has been considered. For the model analysis, the study has been divided into two principal parts. First of all, we study the local stability of the equilibria and the existence of Hopf bifurcation. Then, for the numerical analysis, the Caputo fractional derivative operator is utilized to approximate the numerical solution of the model. An excellent agreement is seen between the numerical results and the theoretical predictions. 相似文献
52.
53.
Sunil Kumar Surath Ghosh Bessem Samet Emile Franc Doungmo Goufo 《Mathematical Methods in the Applied Sciences》2020,43(9):6062-6080
The heat equation is parabolic partial differential equation and occurs in the characterization of diffusion progress. In the present work, a new fractional operator based on the Rabotnov fractional-exponential kernel is considered. Next, we conferred some fascinating and original properties of nominated new fractional derivative with some integral transform operators where all results are significant. The fundamental target of the proposed work is to solve the multidimensional heat equations of arbitrary order by using analytical approach homotopy perturbation transform method and residual power series method, where new fractional operator has been taken in new Yang-Abdel-Aty-Cattani (YAC) sense. The obtained results indicate that solution converges to the original solution in language of generalized Mittag-Leffler function. Three numerical examples are discussed to draw an effective attention to reveal the proficiency and adaptability of the recommended methods on new YAC operator. 相似文献
54.
Junying Cao & Zhenning Cai 《高等学校计算数学学报(英文版)》2021,14(1):71-112
We introduce a high-order numerical scheme for fractional ordinary differential equations with the Caputo derivative. The method is developed by dividing
the domain into a number of subintervals, and applying the quadratic interpolation
on each subinterval. The method is shown to be unconditionally stable, and for general nonlinear equations, the uniform sharp numerical order 3 − $ν$ can be rigorously
proven for sufficiently smooth solutions at all time steps. The proof provides a general guide for proving the sharp order for higher-order schemes in the nonlinear
case. Some numerical examples are given to validate our theoretical results. 相似文献
55.
T. Håvie 《BIT Numerical Mathematics》1970,10(3):277-294
Some quadrature formulae using the derivatives of the integrand are discussed. As special cases are obtained generalizations of both the ordinary and the modified Romberg algorithms. In all cases the error terms are expressed in terms of Bernoulli polynomials and functions. 相似文献
57.
本文将文献[9]中给出的一维广义函数的集值导数的某些结果,推广到n维情形,并给出一些与优化有关的其他结果. 相似文献
58.
Subdifferential representation of homogeneous functions and extension of smoothness in Banach spaces
In this paper, we mainly consider proximal subdifferentials of lower semicontinuous functions defined on real Hilbert space and Clarke's subdifferentials of locally Lipschitzian functions defined on Banach space respectively, and obtain the generalized Euler identity of homogenous functions. Then, by introducing a multifunction F, we extend the smoothness of sphere and differentiability of norm function in Banach space. 相似文献
59.
本文研究了近似连续C-可积函数的原函数问题.利用近似连续C-积分的有关性质,得到了函数近似C-可积的一个充分必要条件,推广了B.Bongiorno等人的工作. 相似文献
60.
Devendra Kumar Jagdev Singh Dumitru Baleanu 《Mathematical Methods in the Applied Sciences》2020,43(1):443-457
The present article deals with a fractional extension of the vibration equation for very large membranes with distinct special cases. The fractional derivative is considered in Atangana-Baleanu sense. A numerical algorithm based on homotopic technique is employed to examine the fractional vibration equation. The stability analysis is conducted for the suggested scheme. The maple software package is utilized for numerical simulation. In order to illustrate the effects of space, time, and order of Atangana-Baleanu derivative on the displacement, the outcomes of this study are demonstrated graphically. The results revel that the Atangana-Baleanu fractional derivative is very efficient in describing vibrations in large membranes. 相似文献