全文获取类型
收费全文 | 3333篇 |
免费 | 762篇 |
国内免费 | 206篇 |
专业分类
化学 | 84篇 |
力学 | 392篇 |
综合类 | 83篇 |
数学 | 2648篇 |
物理学 | 1094篇 |
出版年
2024年 | 16篇 |
2023年 | 47篇 |
2022年 | 61篇 |
2021年 | 74篇 |
2020年 | 157篇 |
2019年 | 126篇 |
2018年 | 114篇 |
2017年 | 169篇 |
2016年 | 171篇 |
2015年 | 110篇 |
2014年 | 235篇 |
2013年 | 315篇 |
2012年 | 216篇 |
2011年 | 254篇 |
2010年 | 235篇 |
2009年 | 251篇 |
2008年 | 228篇 |
2007年 | 218篇 |
2006年 | 171篇 |
2005年 | 160篇 |
2004年 | 129篇 |
2003年 | 151篇 |
2002年 | 125篇 |
2001年 | 92篇 |
2000年 | 75篇 |
1999年 | 91篇 |
1998年 | 63篇 |
1997年 | 46篇 |
1996年 | 33篇 |
1995年 | 30篇 |
1994年 | 30篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1959年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有4301条查询结果,搜索用时 0 毫秒
991.
In this paper we study mono-stable traveling wave solutions for a Lotka-Volterra reaction-diffusion competition model with time delay. By constructing upper and lower solutions, we obtain the precise minimum wave speed of traveling waves under certain conditions. Our results also extend the known results on the minimum wave speed for Lotka-Volterra competition model without delay. 相似文献
992.
《Mathematical Methods in the Applied Sciences》2018,41(9):3509-3520
In this paper, we obtain a new oscillation result for delay difference equations of the form under the assumption that corresponding homogenous equation is nonoscillatory, where τn≤n+1. It is observed that the oscillation behaviormay be altered due to presence of the delay. Extensions to forced Emden‐Fowler–type delay difference equations in the sublinear (0<α<1) and the superlinear (1<α) cases are also discussed. 相似文献
993.
《Mathematical Methods in the Applied Sciences》2018,41(10):3547-3557
In this article, we study the analyticity properties of solutions of the nonlocal Kuramoto‐Sivashinsky equations, defined on 2π‐periodic intervals, where ν is a positive constant; μ is a nonnegative constant; p is an arbitrary but fixed real number in the interval [3,4); and is an operator defined by its symbol in Fourier space, with be the Hilbert transform. We establish spatial analyticity in a strip around the real axis for the solutions of such equations, which possess universal attractors. Also, a lower bound for the width of the strip of analyticity is obtained. 相似文献
994.
995.
This paper is concerned with the stability of traveling wavefronts for a population dynamics model with time delay. Combining the weighted energy method and the comparison principle, the global exponential stability of noncritical traveling wavefronts(waves with speeds c c_*, where c = c~* is the minimal speed) is established, when the initial perturbations around the wavefront decays to zero exponentially in space as x →-∞, but it can be allowed arbitrary large in other locations, which improves the results in [9, 18, 21]. 相似文献
996.
A three-dimensional enterprise competitive model with time delay is considered. Where the delay is regarded as bifurcation parameters. By analyzing the corresponding characteristic equation of positive equilibrium,the local stability of positive equilibrium is regarded. By using the normal form method and center manifold theorem, we give the formula for determining the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions. Numerical simulations are shown to illustrate the obtained results. 相似文献
997.
Tongqian Zhan Xinzhu Meng Tonghua Zhang 《Journal of Applied Analysis & Computation》2016,6(2):479-491
In this paper, we propose a new SIV epidemic model with time delay, which also involves both direct and environmental transmissions. For such model, we first introduce the basic reproduction number $\mathscr{R}$ by using the next generation matrix. And then global stability of the equilibria is discussed by means of Lyapunov
functionals and LaSalle''s invariance principle for delay differential equations, which shows that the infection-free equilibrium of the system is globally asymptotically stable if $\mathscr{R}<1$ and the epidemic equilibrium of the system is globally asymptotically stable for $\m 相似文献
998.
作为红外标准光源,要求30℃~420℃黑体能快速升温到设定温度点,并保持温度稳定。针对其升降温功率差别大、滞后大等特点,用开关控制冲击响应自整定方法,得到黑体温升超调量、最大升降温速率等参数,采用复合智能温控策略,实现了30℃~420℃黑体温升前期快,接近设置温度时改以渐进方式达到并稳定在设定温度点。实验结果表明,实现了30℃~420℃黑体无超调地到达设定温度点,且稳定性为±0.03℃/min,该指标达到了国际同类产品水平。 相似文献
999.
基于改进型Bessel-Legendre不等式方法,探讨了电力系统时滞相关鲁棒稳定性问题.首先构建了含有时滞环节的电力系统数学模型表达式,并推广出其含有不确定参数的模型表达式,通过应用时滞系统理论分析方法,有效地处理了泛函导数中的积分项,从而推导出了一个具有更小保守性的电力系统时滞相关鲁棒稳定新判据.通过三个数值实例对... 相似文献
1000.
高阶中立型时滞差分方程解的振动性 总被引:9,自引:0,他引:9
研究了一类具有变系数的高阶中立型时滞差分方程解的振动性,给出了其有界解振动的两个充分条件。 相似文献