全文获取类型
收费全文 | 18579篇 |
免费 | 1941篇 |
国内免费 | 1836篇 |
专业分类
化学 | 3469篇 |
晶体学 | 142篇 |
力学 | 2348篇 |
综合类 | 349篇 |
数学 | 12979篇 |
物理学 | 3069篇 |
出版年
2024年 | 25篇 |
2023年 | 176篇 |
2022年 | 201篇 |
2021年 | 298篇 |
2020年 | 480篇 |
2019年 | 439篇 |
2018年 | 394篇 |
2017年 | 513篇 |
2016年 | 539篇 |
2015年 | 374篇 |
2014年 | 770篇 |
2013年 | 1375篇 |
2012年 | 932篇 |
2011年 | 1132篇 |
2010年 | 1085篇 |
2009年 | 1195篇 |
2008年 | 1282篇 |
2007年 | 1348篇 |
2006年 | 1156篇 |
2005年 | 1063篇 |
2004年 | 950篇 |
2003年 | 960篇 |
2002年 | 820篇 |
2001年 | 631篇 |
2000年 | 605篇 |
1999年 | 524篇 |
1998年 | 459篇 |
1997年 | 397篇 |
1996年 | 333篇 |
1995年 | 329篇 |
1994年 | 251篇 |
1993年 | 194篇 |
1992年 | 181篇 |
1991年 | 132篇 |
1990年 | 119篇 |
1989年 | 88篇 |
1988年 | 74篇 |
1987年 | 51篇 |
1986年 | 58篇 |
1985年 | 57篇 |
1984年 | 56篇 |
1983年 | 27篇 |
1982年 | 62篇 |
1981年 | 37篇 |
1980年 | 34篇 |
1979年 | 32篇 |
1978年 | 27篇 |
1977年 | 22篇 |
1976年 | 14篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Here we propose and analyze a mathematical model that aims to describe the marble sulphation process occurring in a given material. The model accounts for rugosity as well as for damaging effects. This model is characterized by some technical difficulties that seem hard to overcome from a theoretical viewpoint. Therefore, we introduce some physically reasonable modifications in order to establish the existence of a suitable notion of solution on a given time interval. Numerical simulations are presented and discussed, also in view of further research. 相似文献
3.
4.
Baoquan Zhou Daqing Jiang Bingtao Han Tasawar Hayat 《Mathematical Methods in the Applied Sciences》2022,45(1):423-455
Considering the effect of stochasticity including white noise and colored noise, this paper aims to study a hybrid stochastic cholera epidemic model with waning vaccine-induced immunity and nonlinear telegraph perturbations. First, we derive a critical value related to the basic reproduction number of the deterministic model. The key aim of this paper is to generalize the θ-stochastic criterion method proposed by the recent work (Han et al. in Chaos Solit Fract 140:110238, 2020) to eliminate nonlinear telegraph perturbations. Next, via constructing several θ-stochastic Lyapunov functions and using the generalized method, we further prove that the stochastic model have a unique ergodic stationary distribution under . Results show that the prevention and control of cholera epidemic depend on low transmission rate and small telegraph perturbations. Finally, the corresponding numerical simulations are performed to illustrate our analytical results and a practical application on the Somalia cholera outbreak is shown at the end of this paper. 相似文献
5.
利用平面动力系统方法的分支理论,研究了Boussinesq方程,通过对Boussinesq方程进行行波变换,得到了相应行波系统的首次积分和平衡点,给出了不同参数条件下的相图,证实了Boussinesq方程存在孤立波解和周期波解。 相似文献
6.
7.
8.
利用标量化方法建立对称向量拟均衡问题有效解的存在性定理。作为标量化方法的应用,利用这一方法得到向量变分不等式和拟向量变分不等式有效解的存在性定理。 相似文献
9.
10.
Combustion processes in porous media have been used by the petroleum engineering industry to extract heavy oil from reservoirs. This study focuses on a one-dimensional nonlinear hybrid system consisting of reaction–diffusion–convection equations coupled with ordinary differential equations, which models a combustion front moving through a porous medium with parallel layers. The state variables are the temperature and fuel concentration in each layer. Coupling occurs in both the reaction function and differential operator coefficients. We prove the existence of a classical solution, first locally and then globally over time, to an initial and boundary value problem for the corresponding system. The proof uses a new approach for combustion problems in porous media. The local solution is obtained by defining an operator in a set of Hölder continuous functions and using Schauder’s fixed-point theorem to find a fixed point as the desired solution. Using Zorn’s lemma, we extend the local solution to a global solution, proving that the first-order spatial derivative of the temperature in each layer is a bounded function. 相似文献