全文获取类型
收费全文 | 15185篇 |
免费 | 1150篇 |
国内免费 | 832篇 |
专业分类
化学 | 251篇 |
晶体学 | 7篇 |
力学 | 1489篇 |
综合类 | 196篇 |
数学 | 13840篇 |
物理学 | 1384篇 |
出版年
2024年 | 22篇 |
2023年 | 147篇 |
2022年 | 183篇 |
2021年 | 219篇 |
2020年 | 340篇 |
2019年 | 337篇 |
2018年 | 400篇 |
2017年 | 416篇 |
2016年 | 402篇 |
2015年 | 301篇 |
2014年 | 673篇 |
2013年 | 1211篇 |
2012年 | 705篇 |
2011年 | 814篇 |
2010年 | 723篇 |
2009年 | 1009篇 |
2008年 | 1046篇 |
2007年 | 1099篇 |
2006年 | 941篇 |
2005年 | 740篇 |
2004年 | 630篇 |
2003年 | 708篇 |
2002年 | 591篇 |
2001年 | 445篇 |
2000年 | 433篇 |
1999年 | 388篇 |
1998年 | 367篇 |
1997年 | 328篇 |
1996年 | 253篇 |
1995年 | 208篇 |
1994年 | 145篇 |
1993年 | 126篇 |
1992年 | 128篇 |
1991年 | 110篇 |
1990年 | 83篇 |
1989年 | 42篇 |
1988年 | 47篇 |
1987年 | 41篇 |
1986年 | 50篇 |
1985年 | 68篇 |
1984年 | 58篇 |
1983年 | 29篇 |
1982年 | 32篇 |
1981年 | 33篇 |
1980年 | 18篇 |
1979年 | 25篇 |
1978年 | 15篇 |
1977年 | 16篇 |
1976年 | 9篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
81.
82.
Andreas Kirsch 《Applicable analysis》2017,96(1):70-84
In this paper, we compare the far-field operators for the full nonlinear inverse scattering problem with the Born approximation as its linearization. The Factorization Method shows that both operators share the same behavior with respect to illposedness of the inverse problem. The results are derived for acoustic and electromagnetic scattering problems and the corresponding problem in electrical impedance tomography. 相似文献
83.
This paper is concerned with the problem of heat conduction from an inclusion in a heat transfer layered medium. Making use of the boundary integral equation method, the well-posedness of the forward problem is established by the Fredholm theory. Then an inverse boundary value problem, i.e. identifying the inclusion from the measurements of the temperature and heat flux on the accessible exterior boundary of the medium is considered in the framework of the linear sampling method. Based on a careful analysis of the Dirichlet-to-Neumann map, the mathematical fundamentals of the linear sampling method for reconstructing the inclusion are proved rigorously. 相似文献
84.
85.
86.
87.
Mihajlo Cekić 《偏微分方程通讯》2017,42(11):1781-1836
In this paper, we consider the problem of identifying a connection ? on a vector bundle up to gauge equivalence from the Dirichlet-to-Neumann map of the connection Laplacian ?*? over conformally transversally anisotropic (CTA) manifolds. This was proved in [9] for line bundles in the case of the transversal manifold being simple—we generalize this result to the case where the transversal manifold only has an injective ray transform. Moreover, the construction of suitable Gaussian beam solutions on vector bundles is given for the case of the connection Laplacian and a potential, following the works of [11]. This in turn enables us to construct the Complex Geometrical Optics (CGO) solutions and prove our main uniqueness result. We also reduce the problem to a new non-abelian X-ray transform for the case of simple transversal manifolds and higher rank vector bundles. Finally, we prove the recovery of a flat connection in general from the DN map, up to gauge equivalence, using an argument relating the Cauchy data of the connection Laplacian and the holonomy. 相似文献
88.
89.
We consider a transmission problem consisting of two semilinear parabolic equations involving fractional diffusion operators of different orders in a general non-smooth setting with emphasis on Lipschitz interfaces and transmission conditions along the interface. We give a unified framework for the existence and uniqueness of strong and mild solutions, and their global regularity properties. 相似文献
90.
Jørgen Bang‐Jensen Tilde My Christiansen Alessandro Maddaloni 《Journal of Graph Theory》2017,85(2):545-567
The k‐linkage problem is as follows: given a digraph and a collection of k terminal pairs such that all these vertices are distinct; decide whether D has a collection of vertex disjoint paths such that is from to for . A digraph is k‐linked if it has a k‐linkage for every choice of 2k distinct vertices and every choice of k pairs as above. The k‐linkage problem is NP‐complete already for [11] and there exists no function such that every ‐strong digraph has a k‐linkage for every choice of 2k distinct vertices of D [17]. Recently, Chudnovsky et al. [9] gave a polynomial algorithm for the k‐linkage problem for any fixed k in (a generalization of) semicomplete multipartite digraphs. In this article, we use their result as well as the classical polynomial algorithm for the case of acyclic digraphs by Fortune et al. [11] to develop polynomial algorithms for the k‐linkage problem in locally semicomplete digraphs and several classes of decomposable digraphs, including quasi‐transitive digraphs and directed cographs. We also prove that the necessary condition of being ‐strong is also sufficient for round‐decomposable digraphs to be k‐linked, obtaining thus a best possible bound that improves a previous one of . Finally we settle a conjecture from [3] by proving that every 5‐strong locally semicomplete digraph is 2‐linked. This bound is also best possible (already for tournaments) [1]. 相似文献