全文获取类型
收费全文 | 2815篇 |
免费 | 580篇 |
国内免费 | 192篇 |
专业分类
化学 | 335篇 |
晶体学 | 20篇 |
力学 | 280篇 |
综合类 | 16篇 |
数学 | 296篇 |
物理学 | 1983篇 |
综合类 | 657篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 28篇 |
2021年 | 32篇 |
2020年 | 36篇 |
2019年 | 39篇 |
2018年 | 47篇 |
2017年 | 67篇 |
2016年 | 89篇 |
2015年 | 89篇 |
2014年 | 134篇 |
2013年 | 216篇 |
2012年 | 168篇 |
2011年 | 204篇 |
2010年 | 179篇 |
2009年 | 206篇 |
2008年 | 221篇 |
2007年 | 218篇 |
2006年 | 181篇 |
2005年 | 181篇 |
2004年 | 121篇 |
2003年 | 135篇 |
2002年 | 122篇 |
2001年 | 96篇 |
2000年 | 94篇 |
1999年 | 82篇 |
1998年 | 77篇 |
1997年 | 62篇 |
1996年 | 59篇 |
1995年 | 62篇 |
1994年 | 53篇 |
1993年 | 41篇 |
1992年 | 33篇 |
1991年 | 32篇 |
1990年 | 31篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有3587条查询结果,搜索用时 15 毫秒
101.
利用电磁场的等效原理,将一个开放微波腔等效于一个闭合边界微波腔(即封闭微波腔)和开放边界(即行波吸收边界)两部分,然后利用等效封闭微波腔的本征模式及其与开放边界的耦合,建立了关于开放微波腔模式(即模式场分布、频率、品质因子)的耦合方程组,其中开放边界为行波吸收边界.以X波段六腔渡越振荡管为例进行分析,将该振荡管等效为封闭微波腔和同轴输出结构两部分,用SUPPERFISH获得封闭腔的各个模式场分布及频率,然后根据封闭微波腔与开放边界的耦合,求得六腔渡越振荡管的工作模频率为9.25GHz,品质因子为115.2,与实验测量结果基本符合. 相似文献
102.
《Optimization》2012,61(3):511-537
We study both the continuous and discrete problems of maximizing the product of two linear functions subject to all variables being between 0 and 1. We first give linear and low-order polynomial algorithms for the solution of the continuous problem. In addition, we describe penalties that help to fix variables in the discrete problem. Extensive computational tests demonstrate the effectiveness of these results. 相似文献
103.
104.
Omar Anza Hafsa Jean-Philippe Mandallena 《Annali di Matematica Pura ed Applicata》2007,186(1):185-196
Consider a plate occupying in a reference configuration a bounded open set Ω ⊂ ℝ
2
, and let
be its stored-energy function. In this paper we are concerned with relaxation of variational problems of type:
, where
with
is the scalar product in ℝ
3
and
is the external loading per unit surface. We take into account the fact that an infinite amount of energy is required to compress
a finite surface of the plate into zero surface, i.e.,
Mathematics Subject Classification (2000) 49J45 相似文献
105.
本文对关于HJB方程的拟变分不等式提出了松弛算法,也给出了基于上述算法的区域分解方法,并建立了相应的收敛性定理。 相似文献
106.
Tijani A. Apalara 《Journal of Mathematical Analysis and Applications》2019,469(2):457-471
In this work we consider a one-dimensional porous-elastic system with memory effects. It is well-known that porous-elastic system with a single dissipation mechanism lacks exponential decay. In contrary, we prove that the unique dissipation given by the memory term is strong enough to exponentially stabilize the system, depending on the kernel of the memory term and the wave speeds of the system. In fact, we prove a general decay result, for which exponential and polynomial decay results are special cases. Our result is new and improves previous results in the literature. 相似文献
107.
In this paper, we prove the existence and uniqueness of relaxation oscillation cycle of a slow–fast modified Leslie–Gower model via the entry–exit function and geometric singular perturbation theory. Numerical simulations are also carried out to illustrate our theoretical result. 相似文献
108.
Tengfei Long Guirong Jiang Zhaosheng Feng 《Journal of Applied Analysis & Computation》2015,5(3):347-362
There exist many types of external excitations that make the damping oscillator with impact have complex dynamics. In this study, both external impulsive excitation and impact are considered to construct a vibro-impact system. The fixed time pulse (impulsive excitation) and the state pulse (impact) lead to the complex and interesting dynamics. The conditions of the existence and stability of four kinds of periodic solutions are investigated, and the bifurcations of period-(1, 0) and period-(1, 1) solutions are analytically studied. Numerical simulations on periodic solutions and bifurcation diagrams are shown by the illustrative example. 相似文献
109.
110.
We give a geometric analysis of relaxation oscillations and canard cycles in a singularly perturbed predator–prey system of Holling and Leslie types. We discuss how the canard cycles are found near the Hopf bifurcation points. The transition from small Hopf-type cycles to large relaxation cycles is also discussed. Moreover, we outline one possibility for the global dynamics. Numerical simulations are also carried out to verify the theoretical results. 相似文献