全文获取类型
收费全文 | 200237篇 |
免费 | 4094篇 |
国内免费 | 11326篇 |
专业分类
化学 | 5655篇 |
晶体学 | 166篇 |
力学 | 11281篇 |
综合类 | 727篇 |
数学 | 169060篇 |
物理学 | 28768篇 |
出版年
2023年 | 1228篇 |
2022年 | 1862篇 |
2021年 | 2582篇 |
2020年 | 3186篇 |
2019年 | 2793篇 |
2018年 | 4709篇 |
2017年 | 5088篇 |
2016年 | 4437篇 |
2015年 | 5417篇 |
2014年 | 7818篇 |
2013年 | 16149篇 |
2012年 | 10086篇 |
2011年 | 10440篇 |
2010年 | 10022篇 |
2009年 | 10368篇 |
2008年 | 9639篇 |
2007年 | 9403篇 |
2006年 | 8049篇 |
2005年 | 6549篇 |
2004年 | 5385篇 |
2003年 | 5615篇 |
2002年 | 5241篇 |
2001年 | 4808篇 |
2000年 | 3851篇 |
1999年 | 4168篇 |
1998年 | 3778篇 |
1997年 | 3517篇 |
1996年 | 3315篇 |
1995年 | 2388篇 |
1994年 | 2088篇 |
1993年 | 2004篇 |
1992年 | 1848篇 |
1991年 | 1743篇 |
1990年 | 1625篇 |
1989年 | 1545篇 |
1988年 | 2180篇 |
1987年 | 2647篇 |
1986年 | 2404篇 |
1985年 | 1988篇 |
1984年 | 1959篇 |
1983年 | 1617篇 |
1982年 | 1778篇 |
1981年 | 1588篇 |
1980年 | 1514篇 |
1979年 | 1423篇 |
1978年 | 1387篇 |
1977年 | 1255篇 |
1976年 | 1284篇 |
1975年 | 1115篇 |
1973年 | 1087篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Journal of Non》2006,352(52-54):5633-5641
In this paper, the optical analysis of the As–S thin films prepared under different conditions is performed using three dispersion models for amorphous materials typically employed in practice. The Tauc–Lorentz (TL) model, Urbach–Cody–Lorentz (UCL) model and our model based on the parameterization of the density of electronic states (PDOS model) are namely used to determine the optical parameters of these films. Within the structural model of the As–S films, the existence of the optical constants profiles and overlayers on to the upper boundaries of these films are included. Dispersion and structural models are employed within the analysis based on a combination of variable angle spectroscopic ellipsometry and transmission spectrophotometry in conjunction with multi-sample modification. It is demonstrated that the TL model is not suitable for the optical characterization of the As–S thin films because of the absence of the Urbach tail. Furthermore, it is shown that both the UCL and PDOS models are satisfactory ones for the optical characterization of these films. Moreover, it is also shown that, using the PDOS dispersion model, one can evaluate the material parameters of these As–S films that correspond to the electronic band structure. 相似文献
2.
This paper solves the problem of the duration of the total eclipseof a satellite of a body, provided that (a) the body is sphericalin shape and the mass distribution inside the body is sphericallysymmetrical; (b) the satellite is a very small object; (c) thesatellite's orbit around a body is circular and the satellitecan pass through the centre of its shadow; (d) a source of lightis the source of the conical body's shadow (umbra) and it doesnot change its apparent position in the sky; (e) there are noperturbations on the satellite's orbit. The solution presentedrepresents the general discussion of the problem based on utilizationof some parts of the theory of contraction mappings. 相似文献
3.
《Applied Mathematics Letters》2006,19(1):32-37
A generalized trapezoid rule is derived. Various error bounds for this rule are established. 相似文献
4.
Boguslav Zegarlinski 《Communications in Mathematical Physics》1991,139(2):305-339
The purpose of this paper is to provide a theoretical framework for disordered spin systems on a lattice, similar to that of classical statistical mechanics in the sense of Ruelle [Ru]. We prove the existence of a continuous pressure functional on a large Banach space of random interactions (highly generalizing the classical one) and formulate an analog of the variational principle. 相似文献
5.
Ronggang Wang 《Communications in Mathematical Physics》1991,137(3):587-597
A new type of vortices called Chern-Simons vortices is considered and the existence is established. 相似文献
6.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
7.
The application of the method of multiplier ideal sheaves to effective problems in algebraic geometry is briefly discussed. Then its application to the deformational invariance of plurigenera for general compact algebraic manifolds is presented and discussed. Finally its application to the conjecture of the finite generation of the canonical ring is explored, and the use of complex algebraic geometry in complex Neumann estimates is discussed.
相似文献8.
《Nonlinear Analysis: Theory, Methods & Applications》2005,62(7):1267-1276
In this paper we obtain sufficient conditions for the existence of positive solutions to a nonlocal eigenvalue problem for a class of nonlinear functional dynamic equations on a time scale. We employ a cone theoretic fixed-point theorem to establish our results. 相似文献
9.
《Nonlinear Analysis: Theory, Methods & Applications》2005,60(2):337-347
We present some results on global existence of classical solutions of certain semilinear parabolic systems with homogeneous Dirichlet boundary conditions in bounded domains with a smooth boundary, relaxing the usual monotonicity assumptions on the nonlinearities. 相似文献
10.
N. N. Pustovoitov 《Analysis Mathematica》2003,29(3):201-218
V stat'e izuchayutsya klassy periodicheskikh funktsii mnogikh peremennykh s zadannoi mazhorantoi smeshannykh modulei nepreryvnosti, prichem mazhoranta imeet spetsial'nyi vid. Rassmotreny nailuchshie priblizheniya ukazannykh klassov i vozmozhnost' kharakterizatsii 'etikh klassov cherez nailuchshie priblizheniya. 相似文献