全文获取类型
收费全文 | 5405篇 |
免费 | 581篇 |
国内免费 | 422篇 |
专业分类
化学 | 421篇 |
晶体学 | 20篇 |
力学 | 817篇 |
综合类 | 104篇 |
数学 | 3972篇 |
物理学 | 1074篇 |
出版年
2024年 | 6篇 |
2023年 | 57篇 |
2022年 | 60篇 |
2021年 | 106篇 |
2020年 | 122篇 |
2019年 | 116篇 |
2018年 | 140篇 |
2017年 | 155篇 |
2016年 | 187篇 |
2015年 | 124篇 |
2014年 | 203篇 |
2013年 | 424篇 |
2012年 | 249篇 |
2011年 | 237篇 |
2010年 | 285篇 |
2009年 | 353篇 |
2008年 | 309篇 |
2007年 | 367篇 |
2006年 | 276篇 |
2005年 | 288篇 |
2004年 | 284篇 |
2003年 | 242篇 |
2002年 | 234篇 |
2001年 | 188篇 |
2000年 | 204篇 |
1999年 | 184篇 |
1998年 | 149篇 |
1997年 | 140篇 |
1996年 | 101篇 |
1995年 | 92篇 |
1994年 | 86篇 |
1993年 | 71篇 |
1992年 | 67篇 |
1991年 | 52篇 |
1990年 | 37篇 |
1989年 | 23篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 22篇 |
1984年 | 22篇 |
1983年 | 9篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
排序方式: 共有6408条查询结果,搜索用时 484 毫秒
1.
利用标量化方法建立对称向量拟均衡问题有效解的存在性定理。作为标量化方法的应用,利用这一方法得到向量变分不等式和拟向量变分不等式有效解的存在性定理。 相似文献
2.
《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2021,38(5):1337-1371
In this paper we consider minimizers of the functional where is a bounded open set and where are the first k eigenvalues on Ω of an operator in divergence form with Dirichlet boundary condition and with Hölder continuous coefficients. We prove that the optimal sets have finite perimeter and that their free boundary is composed of a regular part, which is locally the graph of a -regular function, and a singular part, which is empty if , discrete if and of Hausdorff dimension at most if , for some . 相似文献
3.
采用量子统计系综理论,研究了基态NO分子宏观气体摩尔熵、摩尔内能、摩尔热容等热力学性质.首先应用课题组前期建立的变分代数法(variational algebraic method, VAM)计算获得了基态NO分子的完全振动能级,得到的VAM振动能级作为振动部分,结合欧拉-麦克劳林渐进展开公式的转动贡献,应用于经典的热力学与统计物理公式中,从而计算得到了1000-5000 K温度范围内NO宏观气体的摩尔内能、摩尔熵和摩尔热容.将不同方法计算得到的摩尔热容结果分别与实验值进行比较,结果表明基于VAM完全振动能级获得的结果优于其他方法获得的理论结果.振动部分采用谐振子模型对无限能级求和计算热力学性质的方法有一定的局限性,应当使用有限的完全振动能级进行统计求和. 相似文献
4.
5.
Natalia L. Calvo Sebastian O. SimonettiRubén M. Maggio Teodoro S. Kaufman 《Analytica chimica acta》2015
Exposure of cimetidine (CIM) to dry heat (160–180 °C) afforded, upon cooling, a glassy solid containing new and hitherto unknown products. The kinetics of this process was studied by a second order chemometrics-assisted multi-spectroscopic approach. Proton and carbon-13 nuclear magnetic resonance (NMR), as well as ultraviolet and infrared spectroscopic data were jointly used, whereas multivariate curve resolution with alternating least squares (MCR-ALS) was employed as the chemometrics method to extract process information. It was established that drug degradation follows a first order kinetics. 相似文献
6.
Rong Yin Jihui Zhang Xudong Shang 《Mathematical Methods in the Applied Sciences》2020,43(15):8736-8752
This paper is dedicated to studying the following Schrödinger–Poisson system Under some different assumptions on functions V(x), K(x), a(x) and f(u), by using the variational approach, we establish the existence of positive ground state solutions. 相似文献
7.
In this paper, we investigate the evolution of joint invariants under invariant geometric flows using the theory of equivariant moving frames and the induced invariant discrete variational complex. For certain arc length preserving planar curve flows invariant under the special Euclidean group , the special linear group , and the semidirect group , we find that the induced evolution of the discrete curvature satisfies the differential‐difference mKdV, KdV, and Burgers' equations, respectively. These three equations are completely integrable, and we show that a recursion operator can be constructed by precomposing the characteristic operator of the curvature by a certain invariant difference operator. Finally, we derive the constraint for the integrability of the discrete curvature evolution to lift to the evolution of the discrete curve itself. 相似文献
8.
Robert S. Strichartz 《Proceedings of the American Mathematical Society》2002,130(3):805-817
Harmonic mappings from the Sierpinski gasket to the circle are described explicitly in terms of boundary values and topological data. In particular, all such mappings minimize energy within a given homotopy class. Explicit formulas are also given for the energy of the mapping and its normal derivatives at boundary points.
9.
Johannes Elschner Rainer Hinder Gunther Schmidt 《Advances in Computational Mathematics》2002,16(2-3):139-156
This paper is devoted to the numerical study of diffraction by periodic structures of plane waves under oblique incidence. For this situation Maxwell's equations can be reduced to a system of two Helmholtz equations in R
2 coupled via quasiperiodic transmission conditions on the piecewise smooth interfaces between different materials. The numerical analysis is based on a strongly elliptic variational formulation of the differential problem in a bounded periodic cell involving nonlocal boundary operators. We obtain existence and uniqueness results for discrete solutions and provide the corresponding error analysis. 相似文献
10.