全文获取类型
收费全文 | 27325篇 |
免费 | 751篇 |
国内免费 | 711篇 |
专业分类
化学 | 3980篇 |
晶体学 | 858篇 |
力学 | 526篇 |
综合类 | 71篇 |
数学 | 20485篇 |
物理学 | 2867篇 |
出版年
2023年 | 80篇 |
2022年 | 101篇 |
2021年 | 174篇 |
2020年 | 174篇 |
2019年 | 618篇 |
2018年 | 656篇 |
2017年 | 412篇 |
2016年 | 404篇 |
2015年 | 384篇 |
2014年 | 812篇 |
2013年 | 1525篇 |
2012年 | 837篇 |
2011年 | 1788篇 |
2010年 | 1733篇 |
2009年 | 1963篇 |
2008年 | 2127篇 |
2007年 | 2135篇 |
2006年 | 1580篇 |
2005年 | 1187篇 |
2004年 | 1100篇 |
2003年 | 838篇 |
2002年 | 717篇 |
2001年 | 560篇 |
2000年 | 499篇 |
1999年 | 555篇 |
1998年 | 505篇 |
1997年 | 417篇 |
1996年 | 529篇 |
1995年 | 497篇 |
1994年 | 499篇 |
1993年 | 437篇 |
1992年 | 377篇 |
1991年 | 265篇 |
1990年 | 219篇 |
1989年 | 230篇 |
1988年 | 143篇 |
1987年 | 172篇 |
1986年 | 161篇 |
1985年 | 239篇 |
1984年 | 198篇 |
1983年 | 111篇 |
1982年 | 173篇 |
1981年 | 160篇 |
1980年 | 108篇 |
1979年 | 73篇 |
1978年 | 102篇 |
1977年 | 86篇 |
1976年 | 67篇 |
1975年 | 18篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
991.
We prove a sharp estimate for the k-modulus of smoothness, modelled upon a -Lebesgue space, of a function f in , where Ω is a domain with minimally smooth boundary and finite Lebesgue measure, , and . This sharp estimate is used to establish necessary and sufficient conditions for continuous embeddings of Sobolev-type spaces into generalized Hölder spaces defined by means of the k-modulus of smoothness. General results are illustrated with examples. In particular, we obtain a generalization of the classical Jawerth embeddings. 相似文献
992.
993.
In 1977 the celebrated theorem of B. Dahlberg established that the harmonic measure is absolutely continuous with respect to the Hausdorff measure on a Lipschitz graph of dimension in , and later this result has been extended to more general non-tangentially accessible domains and beyond.In the present paper we prove the first analogue of Dahlberg's theorem in higher co-dimension, on a Lipschitz graph Γ of dimension d in , , with a small Lipschitz constant. We construct a linear degenerate elliptic operator L such that the corresponding harmonic measure is absolutely continuous with respect to the Hausdorff measure on Γ. More generally, we provide sufficient conditions on the matrix of coefficients of L which guarantee the mutual absolute continuity of and the Hausdorff measure. 相似文献
994.
The Kakutani–Bebutov Theorem (1968) states that any compact metric real flow whose fixed point set is homeomorphic to a subset of embeds into the Bebutov flow, the -shift on . An interesting fact is that this universal space is a function space. However, it is not compact, nor locally compact. We construct an explicit countable product of compact subspaces of the Bebutov flow which is a universal space for all compact metric real flows, with no restriction; namely, into which any compact metric real flow embeds. The result is compared to previously known universal spaces. 相似文献
995.
Jing Fan Yaoji Tang Suling Feng 《International journal of environmental analytical chemistry》2013,93(6):361-367
A simple and sensitive kinetic fluorimetric method is reported for the determination of trace amount of formaldehyde. The proposed method is based on the catalytic effect of formaldehyde on the oxidation reaction of rhodamine B with potassium chlorate in sulfuric acid solution. Formaldehyde in the range of 0.020-0.340 µg/mL can be determined with a limit of detection of 5.73 ng/mL. The method has been used to determine trace formaldehyde in fabric and in indoor air. The results thus obtained show good agreement with those determined by acetyl acetone method. 相似文献
996.
This paper presents some new characterizations of Euclidean distance matrices (EDMs) of special structures. More specifically, we discuss multispherical and block-structured EDMs, each of which can be viewed as a generalization of spherical EDM. We focus on a well-known inequality that characterizes spherical EDMs and extend it to the sets of multispherical and block-structured EDMs. Some related results are also presented. 相似文献
997.
Gloria Papi 《Numerical Functional Analysis & Optimization》2013,34(3-4):327-357
The aim of this paper is the shape restoration of a plane object from measurements of its diffracted field at a discrete and finite set of points. The plane sampling lattice is supposed: i) rectangular; ii)periodic. The problem is approached as an interpolation one. A numerical algorithm for practical reconstructions is presented. A-priori limitations on the perimeter of the object and conditions on the samples lead to a-priori bounds able to estimate the precision of the reconstruction. 相似文献
998.
B. Silbermann 《Applicable analysis》2013,92(3):185-197
In order to optimize the stability regions we construct families of k multi-step methods with free parameters and of order k+1. We exhibit parameters for which the real interval of stability is arbitrarly large and using the Flexible Tolerance Method we show how these parameters optimize - under a predefined criterion - the stability region. Computational experience, while limited, has indicated that the procedure is efficient 相似文献
999.
《Quaestiones Mathematicae》2013,36(4):335-341
Abstract Answering to a question formulated by A.F. MONNA, we study the Hahn-Banach extension property and other related topics within the context of A-normed spaces over valued fields. 相似文献
1000.
In this note a representation of the discrete Green's function of a compact discretization of a two point boundary value problem of order n 2 is given which among other things allows a direct proff of the convergence (and divergence) properties. 相似文献