全文获取类型
收费全文 | 19727篇 |
免费 | 2162篇 |
国内免费 | 732篇 |
专业分类
化学 | 8337篇 |
晶体学 | 45篇 |
力学 | 894篇 |
综合类 | 98篇 |
数学 | 6643篇 |
物理学 | 6604篇 |
出版年
2024年 | 27篇 |
2023年 | 177篇 |
2022年 | 275篇 |
2021年 | 455篇 |
2020年 | 508篇 |
2019年 | 514篇 |
2018年 | 398篇 |
2017年 | 466篇 |
2016年 | 696篇 |
2015年 | 601篇 |
2014年 | 852篇 |
2013年 | 1536篇 |
2012年 | 1004篇 |
2011年 | 966篇 |
2010年 | 833篇 |
2009年 | 1123篇 |
2008年 | 1299篇 |
2007年 | 1384篇 |
2006年 | 1155篇 |
2005年 | 917篇 |
2004年 | 790篇 |
2003年 | 812篇 |
2002年 | 771篇 |
2001年 | 624篇 |
2000年 | 635篇 |
1999年 | 551篇 |
1998年 | 499篇 |
1997年 | 357篇 |
1996年 | 311篇 |
1995年 | 253篇 |
1994年 | 240篇 |
1993年 | 222篇 |
1992年 | 194篇 |
1991年 | 133篇 |
1990年 | 112篇 |
1989年 | 110篇 |
1988年 | 116篇 |
1987年 | 77篇 |
1986年 | 73篇 |
1985年 | 112篇 |
1984年 | 85篇 |
1983年 | 25篇 |
1982年 | 51篇 |
1981年 | 48篇 |
1980年 | 48篇 |
1979年 | 40篇 |
1978年 | 33篇 |
1977年 | 37篇 |
1976年 | 30篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
131.
汪巍 《数学的实践与认识》2004,34(3):103-109
首先引入了差分系统基于两种度量的极端稳定性概念 ,然后建立了一些关于差分系统 ( h0 ,h)极端稳定性 (极端一致稳定性 ,极端渐近稳定性 ,极端一致渐近稳定性 )的判定准则 .在所得到的定理中 ,对△ V的限制较弱 ,特别地 ,△V甚至可以恒为正 ,从而便于实际应用 . 相似文献
132.
133.
Piotr Biler 《Reports on Mathematical Physics》2003,52(2):205-225
We study asymptotic properties of solutions to an extension to arbitrary dimensions of the astrophysical model proposed by Chavanis et al. to explain phenomena of gravitational collapse in clouds of self-gravitating particles. In particular, we show that in the two-dimensional case the solutions can be continued to global ones, while in three space dimensions large data of negative energy blow up in a finite time. Relations between isothermal, Streater's energy-transport and the present models are also studied. 相似文献
134.
This paper presents some properties of two restricted classes of multi-degree-of-freedom potential systems subjected to Gaussian white-noise excitations. Specifically, potential systems which exhibit damping terms with energy-dependent polynomial form are referred to. In this context, first systems with coupled stiffness terms and damping terms depending on the total energy are investigated. Then, systems with uncoupled stiffness terms and damping terms depending on the total energy in each degree-of-freedom are considered. For these two classes, it is found that algebraic relations among the stationary statistical moments of the energy functions can be derived by applying standard tools of Itô calculus. Further, it is noted that these relations are very useful within the framework of an equivalent statistical non-linearization technique to build approximate solutions for arbitrary non-linear systems. 相似文献
135.
Iasson Karafyllis 《Journal of Mathematical Analysis and Applications》2007,328(2):876-899
A system-theoretic framework is proposed, which allows the study of hybrid uncertain systems, which do not satisfy the so-called “semigroup property.” Characterizations of the notion of robust global asymptotic output stability (RGAOS) are given. Based on the provided characterizations, the qualitative behavior of hybrid systems obtained by time-discretization of systems of ordinary differential equations with a globally asymptotically stable equilibrium point, is studied. 相似文献
136.
A Liouville type theorem for polyharmonic elliptic systems 总被引:1,自引:0,他引:1
Yajing Zhang 《Journal of Mathematical Analysis and Applications》2007,326(1):677-690
In this paper, we consider the polyharmonic system m(−Δ)U=Vq,m(−Δ)V=Up in RN, for m>1, N>2m, with p?1, q?1, but not both equal to 1, where m(−Δ) is the polyharmonic operator. Set α=2m(q+1)/(pq−1), β=2m(p+1)/(pq−1), for α,β∈[(N−2)/2,N−2m), we prove the nonexistence of positive solutions. 相似文献
137.
R. Percacci A. Vespignani 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):411-414
Measurements and data analysis have proved very effective in the study of the Internet's physical fabric and have shown heterogeneities
and statistical fluctuations extending over several orders of magnitude. Here we focus on the relationship between the Round-Trip-Time
(RTT) and the geographical distance. We define dimensionless variables that contain information on the quality of Internet
connections finding that their probability distributions are characterized by a slow power-law decay signalling the presence
of scale-free features. These results point out the extreme heterogeneity of Internet delay since the transmission speed between
different points of the network exhibits very large fluctuations. The associated scaling exponents appear to have fairly stable
values in different data sets and thus define an invariant characteristic of the Internet that might be used in the future
as a benchmark of the overall state of “health” of the Internet.
Received 25 January 2003 Published online 7 May 2003 相似文献
138.
J. Seke 《Il Nuovo Cimento D》1993,15(7):1031-1034
Summary By using a self-consistent projection-operator method, developed recently by the present author, a gauge-invariant Markovian
treatment of the spontaneous decay of an unstable atomic state is presented. Without ignoring retardation and electron-spin
effects a gauge-invariant result for the probability amplitude of finding the atom in the unstable state is obtained. 相似文献
139.
Details are given of a new method allowing an exact calculation of the spontaneous magnetization in the corner as well as along the edge at an arbitrary distance of the corner for a rectangular planar Ising ferromagnet. 相似文献
140.