全文获取类型
收费全文 | 4707篇 |
免费 | 240篇 |
国内免费 | 20篇 |
专业分类
化学 | 3495篇 |
晶体学 | 12篇 |
力学 | 187篇 |
数学 | 544篇 |
物理学 | 729篇 |
出版年
2023年 | 45篇 |
2022年 | 46篇 |
2021年 | 99篇 |
2020年 | 105篇 |
2019年 | 108篇 |
2018年 | 88篇 |
2017年 | 66篇 |
2016年 | 140篇 |
2015年 | 122篇 |
2014年 | 176篇 |
2013年 | 204篇 |
2012年 | 350篇 |
2011年 | 413篇 |
2010年 | 192篇 |
2009年 | 179篇 |
2008年 | 345篇 |
2007年 | 301篇 |
2006年 | 298篇 |
2005年 | 285篇 |
2004年 | 257篇 |
2003年 | 165篇 |
2002年 | 173篇 |
2001年 | 51篇 |
2000年 | 36篇 |
1999年 | 36篇 |
1998年 | 26篇 |
1997年 | 34篇 |
1996年 | 39篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 29篇 |
1992年 | 32篇 |
1990年 | 26篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 28篇 |
1984年 | 32篇 |
1983年 | 15篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 21篇 |
1979年 | 20篇 |
1978年 | 24篇 |
1977年 | 26篇 |
1976年 | 14篇 |
1975年 | 24篇 |
1974年 | 18篇 |
1970年 | 11篇 |
排序方式: 共有4967条查询结果,搜索用时 31 毫秒
11.
The general expressions for the compliance , Young's modulus E(h k l) and Poisson's ratio υ(h k l) along an arbitrary direction [h k l] are given for cubic crystals. The representation surfaces, for which the length of the radius vector in the [h k l] direction equals to E(h k l) or υ(h k l), are constructed for seven BCC transition metals Cr, Fe, Mo, Nb, Ta, V and W. Neglecting W, which is isotropic, both representation surfaces of Young's modulus and Poisson's ratio are spherical surfaces. The remaining BCC transition metals may be grouped into two classes. In the first group (Cr, Mo, Nb and V) with negative values of sA, Young's modulus surface has eight depressed corners and six rounded protuberances at the centers of the faces. In the second group (Fe and Ta) with positive values of sA, on the contrary, Young's modulus surface has eight rounded protuberance corners and six depressions at the centers of the faces. The contrary conclusions are obtained for Poisson's ratio. 相似文献
12.
Franck D'Agosto Marie‐Thrse Charreyre Christian Pichot Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2003,41(9):1188-1195
A method is described for synthesizing latex particles with anchored hairs by the grafting of hydrophilic chains, synthesized by reversible addition–fragmentation chain transfer, onto functionalized latex particles. These have the potential to bind biologically active species. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1188–1195, 2003 相似文献
13.
We investigate the combinatorics of a topological space that is generated by the set of edge-weighted finite trees. This space arises by multiplying the weights of edges on paths in trees and is closely connected to tree reconstruction problems involving finite state Markov processes. We show that this space is a contractible finite CW-complex whose face poset can be described via a partial order on semilabelled forests. We then describe some combinatorial properties of this poset, showing that, for example, it is pure, thin and contractible. 相似文献
14.
15.
As pan of a biomimetic approach towards me marine triterpene teurilene (2), the synthesis of the chiral diepoxide 3 is described. Aiming at the synthesis of the squalene tetraepoxide 1, double Sharpless epoxidation led to the intermediate bisglycidic alcohol 7 being subject to a stereochemical analysis. 相似文献
16.
Boris Andreianov Franck Boyer Florence Hubert 《Numerical Methods for Partial Differential Equations》2007,23(1):145-195
Discrete duality finite volume schemes on general meshes, introduced by Hermeline and Domelevo and Omnès for the Laplace equation, are proposed for nonlinear diffusion problems in 2D with nonhomogeneous Dirichlet boundary condition. This approach allows the discretization of non linear fluxes in such a way that the discrete operator inherits the key properties of the continuous one. Furthermore, it is well adapted to very general meshes including the case of nonconformal locally refined meshes. We show that the approximate solution exists and is unique, which is not obvious since the scheme is nonlinear. We prove that, for general W?1,p′(Ω) source term and W1‐(1/p),p(?Ω) boundary data, the approximate solution and its discrete gradient converge strongly towards the exact solution and its gradient, respectively, in appropriate Lebesgue spaces. Finally, error estimates are given in the case where the solution is assumed to be in W2,p(Ω). Numerical examples are given, including those on locally refined meshes. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
17.
18.
19.
Vincent Bailliez 《Tetrahedron》2004,60(5):1079-1085
Polynitrogenated analogues of glucopyranoses were synthesised from levoglucosan. These compounds are useful intermediates for the synthesis of new aminoglycoside mimetics. 相似文献
20.
Christophe Rochais Vincent Lisowski Patrick Dallemagne Sylvain Rault 《Tetrahedron letters》2004,45(33):6353-6355
Novel arylpyrrolo- and pyrazolopyrrolizinones were prepared in three or four steps starting from aminoarylpyrrole and pyrazole carboxylates through the cyclisation of a Vilsmeier-Haack intermediate. This synthesis was enhanced by diverse N-protections of the aza-heterocycle and furnish new series with potential biological interest. 相似文献