全文获取类型
收费全文 | 10718篇 |
免费 | 368篇 |
国内免费 | 488篇 |
专业分类
化学 | 689篇 |
晶体学 | 42篇 |
力学 | 782篇 |
综合类 | 51篇 |
数学 | 7524篇 |
物理学 | 2486篇 |
出版年
2024年 | 10篇 |
2023年 | 103篇 |
2022年 | 108篇 |
2021年 | 154篇 |
2020年 | 189篇 |
2019年 | 208篇 |
2018年 | 203篇 |
2017年 | 216篇 |
2016年 | 240篇 |
2015年 | 222篇 |
2014年 | 530篇 |
2013年 | 940篇 |
2012年 | 479篇 |
2011年 | 701篇 |
2010年 | 570篇 |
2009年 | 688篇 |
2008年 | 738篇 |
2007年 | 756篇 |
2006年 | 489篇 |
2005年 | 389篇 |
2004年 | 342篇 |
2003年 | 353篇 |
2002年 | 308篇 |
2001年 | 266篇 |
2000年 | 279篇 |
1999年 | 273篇 |
1998年 | 222篇 |
1997年 | 210篇 |
1996年 | 174篇 |
1995年 | 180篇 |
1994年 | 154篇 |
1993年 | 89篇 |
1992年 | 78篇 |
1991年 | 67篇 |
1990年 | 54篇 |
1989年 | 44篇 |
1988年 | 40篇 |
1987年 | 38篇 |
1986年 | 48篇 |
1985年 | 64篇 |
1984年 | 49篇 |
1983年 | 41篇 |
1982年 | 41篇 |
1981年 | 33篇 |
1980年 | 44篇 |
1979年 | 54篇 |
1978年 | 29篇 |
1977年 | 34篇 |
1976年 | 13篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
81.
A model proposed in the literature for fish schools of relatively large size is studied for mathematical and qualitative properties. Existence, uniqueness and positivity of solutions are established and bifurcation properties relative to diffusion and alignment parameters are studied. 相似文献
82.
A. Aghajani 《Journal of Mathematical Analysis and Applications》2007,326(2):1076-1089
We consider the nonlinear Euler differential equation t2x″+g(x)=0. Here g(x) satisfies xg(x)>0 for x≠0, but is not assumed to be sublinear or superlinear. We present implicit necessary and sufficient condition for all nontrivial solutions of this system to be oscillatory or nonoscillatory. Also we prove that solutions of this system are all oscillatory or all nonoscillatory and cannot be both. We derive explicit conditions and improve the results presented in the previous literature. We extend our results to the extended equation t2x″+a(t)g(x)=0. 相似文献
83.
84.
This study provides a stability theory for the nonlinear least-squares formulation of estimating the diffusion coefficient in a two-point boundary-value problem from an error-corrupted observation of the state variable. It is based on analysing the projection of the observation on the nonconvex attainable set.This research was started while G. Chavent visited the Technical University of Graz. Support through the Steiermaerkische Landesregierung is gratefully acknowledged. 相似文献
85.
In this paper, we consider a queueing system in which there are two exponential servers, each having his own queue, and arriving
customers will join the shorter queue. Based on the results given in Flatto and McKean, we rewrite the formula for the probability
that there are exactlyk customers in each queue, wherek = 0, 1,…. This enables us to present an algorithm for computing these probabilities and then to find the joint distribution
of the queue lengths in the system. A program and numerical examples are given. 相似文献
86.
A. Gerasimov 《Journal of statistical physics》1993,70(3-4):939-948
The analysis is carried out of the response of the center of gravity (dipole moment) of the distribution of noninteracting thermalized nonlinear oscillators to a sinusoidal driving force. Heat bath coupling is modeled by damping and noise. The driving is weak, but the frequency is resonant, so that there is a nonlinear resonance in the phase space. The response has a linear part that can be obtained from the perturbation analysis and a small nonlinear correction that is specific for the resonant structure. 相似文献
87.
OSCILLATION OF A FORCED SECOND ORDER NONLINEAR EQUATION ¥KONGQINGKAI;ZHANGBINGGENAbstract:Thispapergivesseveralcriteriaontheo... 相似文献
88.
马意海 《高校应用数学学报(A辑)》1998,13(2):197-202
本文对一类重要的混合单调算子证明了不动点的存在、唯一与逼近定理,并应用于研究动态规划中泛函方程的正解问题. 相似文献
89.
关于非齐次m阶马氏信源的渐近均分割性 总被引:4,自引:0,他引:4
本文研究非齐次m阶马氏信源的渐近均分割性,首先我们得到关于此种信源m 1元函数的一类强极限定理,作为推论,得到关于任意非齐次m阶马氏信源状态和熵密度的几个极限定理,最后得到一类非齐次m阶马氏信源的渐近均分割性。 相似文献
90.
Esa Nummelin 《Journal of Theoretical Probability》1994,7(4):739-756
The paper is concerned with characterization results for distributional regeneration. It is shown that distributional regeneration is equivalent to renewal representation of the associated (shift) Markov operator. A sufficient condition for the distributional regeneration of the transfer operator in terms of variation is also formulated. Finally, a minorization condition is formulated and proved to be sufficient for recurrent co-Feller operators. 相似文献