全文获取类型
收费全文 | 10615篇 |
免费 | 1597篇 |
国内免费 | 1744篇 |
专业分类
化学 | 2405篇 |
晶体学 | 127篇 |
力学 | 669篇 |
综合类 | 145篇 |
数学 | 4591篇 |
物理学 | 6019篇 |
出版年
2024年 | 19篇 |
2023年 | 87篇 |
2022年 | 196篇 |
2021年 | 235篇 |
2020年 | 229篇 |
2019年 | 249篇 |
2018年 | 241篇 |
2017年 | 339篇 |
2016年 | 348篇 |
2015年 | 301篇 |
2014年 | 521篇 |
2013年 | 813篇 |
2012年 | 555篇 |
2011年 | 553篇 |
2010年 | 534篇 |
2009年 | 686篇 |
2008年 | 801篇 |
2007年 | 790篇 |
2006年 | 754篇 |
2005年 | 691篇 |
2004年 | 555篇 |
2003年 | 551篇 |
2002年 | 508篇 |
2001年 | 437篇 |
2000年 | 416篇 |
1999年 | 398篇 |
1998年 | 316篇 |
1997年 | 329篇 |
1996年 | 256篇 |
1995年 | 183篇 |
1994年 | 160篇 |
1993年 | 114篇 |
1992年 | 129篇 |
1991年 | 107篇 |
1990年 | 77篇 |
1989年 | 76篇 |
1988年 | 67篇 |
1987年 | 49篇 |
1986年 | 32篇 |
1985年 | 39篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 24篇 |
1978年 | 14篇 |
1977年 | 16篇 |
1974年 | 11篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Mathematical Notes - 相似文献
92.
93.
94.
F.O. Borges G.H. Cavalcanti A.G. Trigueiros 《Journal of Quantitative Spectroscopy & Radiative Transfer》2003,78(1):119-129
The weighted oscillator strengths (gf) and the lifetimes presented in this work were carried out in a multi configuration Hartree-Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work, we presented all the experimentally known electric dipole S IX and S X spectral lines. 相似文献
95.
考虑到量子相干效应和界面散射效应 ,利用 L ambert理论模型 ,计算正常金属 /绝缘层 /超导 /绝缘层 /正常金属双垒隧道结中的准粒子输运系数和隧道谱。研究表明 :( 1)所有的准粒子输运系数和电导谱在超导能隙之上都随能量作周期性振荡 ,其振荡周期依赖于超导层的厚度 ;( 2 )在超导能隙之上 Andreev反射系数随能量呈现周期性消失现象 ;( 3)在绝缘层势垒强度取很大的隧道极限下 ,超导层中会形成一系列的准粒子束缚态 ,其位置由量子化条件决定 ;( 4)界面散射效应不仅能压低各子能隙电导峰 ,还能使子能隙电导峰劈裂为两个峰。 相似文献
96.
In this article we use classical formulas involving the K–Bessel function in two variables to express the Poisson kernel on a Riemannian manifold in terms of the heat kernel. We then use the small time asymptotics of the heat kernel on certain Riemannian manifolds to obtain a meromorphic continuation of the associated Poisson kernel to all values of complex time with identifiable singularities. This result reproves in a different setting by different means a well–known theorem due to Duistermaat and Guillemin [DG 75]. Also, we develop analytic expressions for the heat kernel beyond asymptotic expansions. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
97.
Alan L. Andrew 《BIT Numerical Mathematics》2003,43(3):485-503
The asymptotic correction technique of Paine, de Hoog and Anderssen can dramatically improve the accuracy of finite difference or finite element eigenvalues at negligible extra cost if closed form expressions are available for the errors in a simpler related problem. This paper gives closed form expressions for the errors in the eigenvalues of certain Sturm–Liouville problems obtained by various methods, thereby increasing the range of problems for which asymptotic correction can achieve maximum efficiency. It also investigates implementation of the method for more general problems. 相似文献
98.
On the basis of the hydrodynamic equations for nonlinear elastic-gravity waves beneath a solid ice cover and their Hamiltonian representation, a three-wave kinetic equation for the time evolution of the wave spectrum is formulated. The properties of the kernel of the kinetic integral describing the nonlinear interactions between wave triplets are investigated. An algorithm for numerically calculating the kinetic integral is developed. The rate of nonlinear energy transfer over the wave spectrum is estimated quantitatively and its most important characteristics are found. 相似文献
99.
Asymptotic methods for contact problems are expounded. Some typical integral equations are considered 相似文献
100.
Rolando Cavazos-Cadena 《Annals of Operations Research》1991,28(1):169-184
We consider a class of Markov decision processes withfinite state and action spaces which, essentially, is determined by the following condition: The state space isirreducible under the action of any stationary policy. However, except by this restriction, the transition law iscompletely unknown to the controller. In this context, we find a set of policies under which thefrequency estimators of the transition law are strongly consistent and then, this result is applied to constructadaptive asymptotically discount-optimal policies.Dedicated to Professor Truman O. Lewis, on the occasion of his sixtieth birthdayThis research was supported in part by the Third World Academy of Sciences (TWAS) under Grant TWAS RG MP 898-152, and in part by the Consejo Nacional de Ciencia y Tecnología (CONACYT) under Grant A128CCOEO550 (MT-2). 相似文献