全文获取类型
收费全文 | 6896篇 |
免费 | 653篇 |
国内免费 | 566篇 |
专业分类
化学 | 832篇 |
晶体学 | 22篇 |
力学 | 502篇 |
综合类 | 180篇 |
数学 | 3827篇 |
物理学 | 2752篇 |
出版年
2024年 | 11篇 |
2023年 | 95篇 |
2022年 | 121篇 |
2021年 | 182篇 |
2020年 | 162篇 |
2019年 | 168篇 |
2018年 | 156篇 |
2017年 | 228篇 |
2016年 | 271篇 |
2015年 | 214篇 |
2014年 | 360篇 |
2013年 | 485篇 |
2012年 | 338篇 |
2011年 | 379篇 |
2010年 | 298篇 |
2009年 | 441篇 |
2008年 | 490篇 |
2007年 | 442篇 |
2006年 | 428篇 |
2005年 | 346篇 |
2004年 | 300篇 |
2003年 | 271篇 |
2002年 | 309篇 |
2001年 | 251篇 |
2000年 | 251篇 |
1999年 | 179篇 |
1998年 | 173篇 |
1997年 | 148篇 |
1996年 | 107篇 |
1995年 | 52篇 |
1994年 | 77篇 |
1993年 | 43篇 |
1992年 | 47篇 |
1991年 | 38篇 |
1990年 | 25篇 |
1989年 | 36篇 |
1988年 | 28篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 21篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1975年 | 7篇 |
排序方式: 共有8115条查询结果,搜索用时 62 毫秒
11.
Formalization for problems of multicriteria decision making under uncertainty is constructed in terms of guaranteed and weak
estimates. A relevant definition of the vector maximinimax value is given. Parameterization and approximation of maximum,
minimax, and maximinimax values based on the inverse logical convolution are suggested. An application for multicommodity
networks is considered.
Received: December 13, 2000 / Accepted: August 21, 2001?Published online May 8, 2002 相似文献
12.
第五讲新型光纤水听器和矢量水听器 总被引:2,自引:0,他引:2
光纤水听器和矢量水听器作为当前水声研究领域最具有代表性的两大技术倍受业界关注。光纤水听器的重要贡献在于,从一个全新的角度出发,试图解决传统的水声传感和声纳数据传输一体化设计和实现的一系列问题,这有助于改善声纳系统的可靠性,并且有可能降低其制造、使用和维护的总成本。矢量水听器则由于其特有的指向性和矢量一相位处理方法,在低频和甚低频水声微弱目标探测方面具有潜在的优势.经过不懈的努力,光纤水听器和矢量水听器系统已经从实验室逐渐进入到工程应用阶段.这些对未来声纳系统的发展会产生相当重要的影响.文章尝试从声纳设计的角度对这两者的技术现状进行简要综述,包括它们各自的物理基础、工作原理、关键技术和应用领域. 相似文献
13.
Mathematical economics has a long history and covers many interdisciplinary areas between mathematics and economics. At its center lies the theory of market equilibrium. The purpose of this expository article is to introduce mathematicians to price decentralization in general equilibrium theory. In particular, it concentrates on the role of positivity in the theory of convex economic analysis and the role of normal cones in the theory of non-convex economies. 相似文献
14.
Matroid bundles, introduced by MacPherson, are combinatorial analogues of real vector bundles. This paper sets up the foundations
of matroid bundles. It defines a natural transformation from isomorphism classes of real vector bundles to isomorphism classes
of matroid bundles. It then gives a transformation from matroid bundles to spherical quasifibrations, by showing that the
geometric realization of a matroid bundle is a spherical quasifibration. The poset of oriented matroids of a fixed rank classifies
matroid bundles, and the above transformations give a splitting from topology to combinatorics back to topology. A consequence
is that the mod 2 cohomology of the poset of rank k oriented matroids (this poset classifies matroid bundles) contains the free polynomial ring on the first k Stiefel-Whitney classes. 相似文献
15.
用能量法求多自由度振动系统的角频率 总被引:2,自引:1,他引:1
利用简谐振动能量方程,通过分析振幅矢量的关系,用能量法求多自由度振动系统的角频率或简正振动频率。 相似文献
16.
17.
18.
O. Castaños 《Journal of Molecular Spectroscopy》2007,241(1):51-60
A simple algebraic approach to calculate general Franck-Condon overlaps is extended to evaluate non-Condon factors for two one-dimensional harmonic oscillators. The method is based on the use of eigenstates of the harmonic oscillator annihilation operator which allows to obtain in terms of a multi-dimensional Hermite polynomial the overlap of harmonic oscillator functions associated with different Born-Oppenheimer potentials. The presented approach is self-contained, only basic concepts of quantum mechanics associated with the harmonic oscillator system are needed. The obtained expression for the Franck-Condon overlaps is similar to the Ansbacher’s formula and equivalent to the one calculated by Malkin and Man’ko. However our final expression has the advantages that only real numbers are involved and it is straightforward to get the limit case of equal frequencies. Concerning the non-Condon factors two approaches leading to different formulas are considered, both of which reduce to triple sums of products of three Hermite polynomials. 相似文献
19.
The vibrational dynamics of protein folding is analyzed in the framework of Tsallis statistics. We employ exact expressions
for classical harmonic oscillators by considering the unnormalized constraints. As q→1, we show that these approximations agree with the result of Gaussian network model. 相似文献
20.
In this paper we continue to study the spectral norms and their completions ([4]) in the case of the algebraic closure $ \overline {\mathbb Q} $ of ? in ?. Let $ \widetilde{\overline{\mathbb{Q}}} $ be the completion of $ \overline {\mathbb Q} $ relative to the spectral norm. We prove that $ \widetilde{\overline{\mathbb{Q}}} $ can be identified with the R‐subalgebra of all symmetric functions of C(G), where C(G) denotes the ?‐Banach algebra of all continuous functions defined on the absolute Galois group G = Gal$ {\overline {\mathbb Q}} / {\mathbb Q} $. We prove that any compact, closed to conjugation subset of ? is the pseudo‐orbit of a suitable element of $ \widetilde{\overline{\mathbb{Q}}} $. We also prove that the topological closure of any algebraic number field in $ \widetilde{\overline{\mathbb{Q}}} $ is of the form $\widetilde{\mathbb{Q}[x]}$ with x in $ \widetilde{\overline{\mathbb{Q}}} $. 相似文献