全文获取类型
收费全文 | 14232篇 |
免费 | 1258篇 |
国内免费 | 1181篇 |
专业分类
化学 | 2551篇 |
晶体学 | 30篇 |
力学 | 1291篇 |
综合类 | 239篇 |
数学 | 9659篇 |
物理学 | 2901篇 |
出版年
2024年 | 23篇 |
2023年 | 165篇 |
2022年 | 171篇 |
2021年 | 225篇 |
2020年 | 322篇 |
2019年 | 356篇 |
2018年 | 366篇 |
2017年 | 399篇 |
2016年 | 424篇 |
2015年 | 340篇 |
2014年 | 582篇 |
2013年 | 946篇 |
2012年 | 541篇 |
2011年 | 686篇 |
2010年 | 662篇 |
2009年 | 830篇 |
2008年 | 915篇 |
2007年 | 956篇 |
2006年 | 869篇 |
2005年 | 806篇 |
2004年 | 636篇 |
2003年 | 607篇 |
2002年 | 701篇 |
2001年 | 500篇 |
2000年 | 475篇 |
1999年 | 414篇 |
1998年 | 419篇 |
1997年 | 339篇 |
1996年 | 312篇 |
1995年 | 243篇 |
1994年 | 198篇 |
1993年 | 160篇 |
1992年 | 138篇 |
1991年 | 113篇 |
1990年 | 86篇 |
1989年 | 73篇 |
1988年 | 75篇 |
1987年 | 68篇 |
1986年 | 69篇 |
1985年 | 68篇 |
1984年 | 53篇 |
1983年 | 29篇 |
1982年 | 60篇 |
1981年 | 57篇 |
1980年 | 45篇 |
1979年 | 42篇 |
1978年 | 38篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
82.
Onofrio Mario Di Vincenzo Plamen Koshlukov Roberto La Scala 《Advances in Applied Mathematics》2006,37(4):541
In this paper we describe completely the involutions of the first kind of the algebra UTn(F) of n×n upper triangular matrices. Every such involution can be extended uniquely to an involution on the full matrix algebra. We describe the equivalence classes of involutions on the upper triangular matrices. There are two distinct classes for UTn(F) when n is even and a single class in the odd case.Furthermore we consider the algebra UT2(F) of the 2×2 upper triangular matrices over an infinite field F of characteristic different from 2. For every involution *, we describe the *-polynomial identities for this algebra. We exhibit bases of the corresponding ideals of identities with involution, and compute the Hilbert (or Poincaré) series and the codimension sequences of the respective relatively free algebras.Then we consider the *-polynomial identities for the algebra UT3(F) over a field of characteristic zero. We describe a finite generating set of the ideal of *-identities for this algebra. These generators are quite a few, and their degrees are relatively large. It seems to us that the problem of describing the *-identities for the algebra UTn(F) of the n×n upper triangular matrices may be much more complicated than in the case of ordinary polynomial identities. 相似文献
83.
We present integral-type Darboux transformation for the mKdV hierarchy and for the mKdV hierarchy withself-consistent sources. In contrast with the normal Darboux transformation, the integral-type Darboux transformationscan offer non-auto-Backlund transformation between two (2n 1)-th mKdV equations with self-consistent sources withdifferent degrees. This kind of Darboux transformation enables us to construct the N-soliton solution for the mKdVhierarchy with self-consistent sources. We also propose the formulas for the m times repeated integral-type Darbouxtransformations for both mKdV hierarchy and mKdV hierarchy with self-consistent sources. 相似文献
84.
利用Ditzian-Totik光滑模,研究了推广的Kantorovich算子在Ba空间中的逼近,得到逼近的正定理与等价定理.所得结果改进、推广和统一了一些作者的结果. 相似文献
85.
对于任意秩有限总体,在二次损失下,有关文献已给出了线性可预测变量在齐次线性预测类中的唯一线性Minimax预测.本文在正态假设下,证明了这个线性Minimax预测也是线性可预测变量在一切预测类中的唯一Minimax预测. 相似文献
86.
Frank Morgan 《Annals of Global Analysis and Geometry》2006,30(1):73-79
In a product M
1 × M
2 of Riemannian manifolds, the least perimeter required to enclose given volume among general regions is at least 1/√ 2 times that among regions of product form, assuming that the isoperimetric profiles of M
1 and M
2 are concave. This result sharpens earlier work of Grigor'yan, generalizes results of Bollobás and Leader and of Barthe, and yields a lower bound on the Cheeger isoperimetric constant of a product. 相似文献
87.
本文提出等效远场的可变孔径方法,由测量光纤远场累积分布求得模场半径。并且利用Petermann关于模场半径的新定义,推出了一种对非高斯模场分布也适用的求模场半径的方法。实验表明,这种测量方法简便可靠,在不同的制备端面下,重复测量的标准误差小于0.04μm。 相似文献
88.
R.S. Kraußhar 《Journal of Mathematical Analysis and Applications》2007,325(1):359-376
In this paper we study Clifford and harmonic analysis on some examples of conformal flat manifolds that have a spinor structure, or more generally, at least a pin structure. The examples treated here are manifolds that can be parametrized by U/Γ where U is a subdomain of either Sn or Rn and Γ is a Kleinian group acting discontinuously on U. The examples studied here include RPn and the Hopf manifolds S1×Sn−1. Also some hyperbolic manifolds will be treated. Special kinds of Clifford-analytic automorphic forms associated to the different choices of Γ are used to construct explicit Cauchy kernels, Cauchy integral formulas, Green's kernels and formulas together with Hardy spaces and Plemelj projection operators for Lp spaces of hypersurfaces lying in these manifolds. 相似文献
89.
In this paper, the possibility of using the gradients of the temperature and of the internal parameters as additional state variables in Continuum Thermodynamics is considered. The expressions of the two principles are discussed and Clausius–Duhem inequality is derived under an appropriate statement of the internal entropy production. Several formulations are proposed and compared to existing results in the literature. To cite this article: P. Ireman, Q.S. Nguyen, C. R. Mecanique 332 (2004). 相似文献
90.