全文获取类型
收费全文 | 214950篇 |
免费 | 2515篇 |
国内免费 | 595篇 |
专业分类
化学 | 110496篇 |
晶体学 | 3399篇 |
力学 | 9486篇 |
综合类 | 5篇 |
数学 | 24114篇 |
物理学 | 70560篇 |
出版年
2021年 | 1761篇 |
2020年 | 1979篇 |
2019年 | 2185篇 |
2018年 | 2816篇 |
2017年 | 2716篇 |
2016年 | 4159篇 |
2015年 | 2705篇 |
2014年 | 4049篇 |
2013年 | 9915篇 |
2012年 | 8146篇 |
2011年 | 9542篇 |
2010年 | 6530篇 |
2009年 | 6279篇 |
2008年 | 8676篇 |
2007年 | 8792篇 |
2006年 | 8450篇 |
2005年 | 7539篇 |
2004年 | 6937篇 |
2003年 | 6104篇 |
2002年 | 5879篇 |
2001年 | 6570篇 |
2000年 | 5074篇 |
1999年 | 3885篇 |
1998年 | 3103篇 |
1997年 | 3115篇 |
1996年 | 2896篇 |
1995年 | 2681篇 |
1994年 | 2516篇 |
1993年 | 2417篇 |
1992年 | 2752篇 |
1991年 | 2718篇 |
1990年 | 2646篇 |
1989年 | 2434篇 |
1988年 | 2485篇 |
1987年 | 2486篇 |
1986年 | 2338篇 |
1985年 | 3041篇 |
1984年 | 3282篇 |
1983年 | 2666篇 |
1982年 | 2855篇 |
1981年 | 2824篇 |
1980年 | 2697篇 |
1979年 | 2774篇 |
1978年 | 2872篇 |
1977年 | 2858篇 |
1976年 | 2934篇 |
1975年 | 2698篇 |
1974年 | 2672篇 |
1973年 | 2802篇 |
1972年 | 1773篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
D. V. Georgievskii 《Doklady Physics》2003,48(10):590-593
992.
We consider the target level method for solving linear multi-criterion maximization problems. The method finds an efficient (Pareto-optimal) vector estimate that is closest in the Chebyshev metric to the target level point specified by the decision maker. The proposed method describes (parametrizes and approximates) the efficient set. In the linear case the number of scalar optimization problems needed to describe the set of efficient vector estimates is substantially reduced. A formula is derived which, under certain conditions, can be used to compute efficient vector estimates without solving any optimization problems. An algorithm based on these results is proposed for two-criterion problems. 相似文献
993.
994.
Non-steady-state mass-transfer processes in the electrochemical cells of rectangular cross-section with vertical and horizontal electrodes under the conditions of natural convection are simulated numerically taking into account the diffusion and convection of solely ions discharging at the electrode under limiting-current conditions. The interrelated time variations of the limiting current density at various ratios of the electrode height (length) to the interelectrode distance and the distributions of ion concentration and hydrodynamic velocity over the cell are determined. 相似文献
995.
The purpose of this paper is to review the mechanisms and available theoretical methods for modeling the strength and failure of thin film/substrate systems 相似文献
996.
In this paper, we study the inverse problem of the reconstruction of the right-hand side of special form for a parabolic equation in u in which the coefficients of u t and u depend on u (x,t) , with overdetermination given by the integral of the solution over time. The Fredholm property for this problem and the existence and uniqueness theorems in Sobolev spaces are established. 相似文献
997.
D. A. Lavis 《Foundations of Physics》2004,34(4):669-688
Simple models have played an important role in the discussion of foundational issues in statistical mechanics. Among them the spin-echo system is of particular interest since it can be realized experimentally. This has led to inferences being drawn about approaches to the foundations of statistical mechanics, particularly with respect to the use of coarse-graining. We examine these claims with the help of computer simulations. 相似文献
998.
D. V. Isakov T. R. Volk L. I. Ivleva K. Betzler C. David A. Tunyagi M. Wöhlecke 《JETP Letters》2004,80(4):258-262
Measurements of 90°-scattering of weak laser light are used to investigate pulsed domain switching in ferroelectrics. The studies were performed on strontium-barium niobate (SBN) single crystals. A good agreement of the switching parameters estimated from the optical measurements with those obtained by means of conventional electrical methods proves the validity of the optical method for switching studies. Due to the limited scattering volume in all three spatial dimensions, the method facilitates local probing of the switching within the crystal bulk. In particular, local specialities of the domain density can be detected. Furthermore, the excellent time resolution inherent in optical probing techniques allows for a comprehensive study of the dynamics. 相似文献
999.
It is shown that, at zero temperature, a hole placed in a homogeneous synthetic nucleotide chain with applied electric field demonstrates Bloch oscillations. The oscillations of the hole placed initially on one of the base pairs arise in response to disruption of the initial charge distribution caused by nucleotide vibrations. The finite temperature fluctuations result in degradation of coherent oscillations. The maximum permissible temperature for DNA “Bloch oscillator” occurrence is estimated. 相似文献
1000.
Absorption of cnoidal electromagnetic waves, which are the most general periodic solution to the sine-Gordon equation, by electrons of a one-dimensional quantum semiconductor superlattice in the process of impurity ionization is studied in terms of the semiclassical approximation. The dependence of the absorption coefficient on the electric field of an electromagnetic wave is found to be nonmonotone with a pronounced peak. 相似文献