全文获取类型
收费全文 | 43900篇 |
免费 | 7096篇 |
国内免费 | 3491篇 |
专业分类
化学 | 11176篇 |
晶体学 | 288篇 |
力学 | 6225篇 |
综合类 | 656篇 |
数学 | 12656篇 |
物理学 | 23486篇 |
出版年
2024年 | 99篇 |
2023年 | 471篇 |
2022年 | 1139篇 |
2021年 | 1192篇 |
2020年 | 1383篇 |
2019年 | 1207篇 |
2018年 | 1176篇 |
2017年 | 1574篇 |
2016年 | 1831篇 |
2015年 | 1483篇 |
2014年 | 2312篇 |
2013年 | 3384篇 |
2012年 | 2601篇 |
2011年 | 2882篇 |
2010年 | 2515篇 |
2009年 | 2878篇 |
2008年 | 2729篇 |
2007年 | 2797篇 |
2006年 | 2466篇 |
2005年 | 2245篇 |
2004年 | 2119篇 |
2003年 | 1818篇 |
2002年 | 1675篇 |
2001年 | 1385篇 |
2000年 | 1319篇 |
1999年 | 1165篇 |
1998年 | 1024篇 |
1997年 | 782篇 |
1996年 | 690篇 |
1995年 | 583篇 |
1994年 | 521篇 |
1993年 | 434篇 |
1992年 | 374篇 |
1991年 | 302篇 |
1990年 | 262篇 |
1989年 | 228篇 |
1988年 | 191篇 |
1987年 | 178篇 |
1986年 | 165篇 |
1985年 | 171篇 |
1984年 | 160篇 |
1983年 | 85篇 |
1982年 | 118篇 |
1981年 | 78篇 |
1980年 | 43篇 |
1979年 | 51篇 |
1978年 | 42篇 |
1977年 | 37篇 |
1976年 | 22篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
给出2005年全国部分高校研究生数学建模竞赛D题的研究背景,对参赛论文作了简要评注,并提供了一种参考解答. 相似文献
42.
具有模糊数的模糊多目标群体决策优选模型与方法 总被引:5,自引:0,他引:5
多目标群体决策问题是运筹学的一个重要研究领域,目前已经提出了一些有效的决策方法。但对目标值和权重均为模糊数的模糊多目标群体决策问题却研究不多,本对此类模糊多目标群体决策问题进行了探讨,利用相对正理想方案与相对负理想方案概念定义了相对差异距离,进而建立了模糊多目标群体决策优选模型与方法,并通过战役决心方案的评价说明了该方法是可行、有效的,可作为军事决策与决策支持系统的备选方法。 相似文献
43.
By use of the 2-m Mcmath-Pierce telescope at Kitt Peak, the high-quality spectra of a plage with moderate brightness near the center of solar disk were obtained. The data include seven spectral lines, which are Hα, Hβ, CaII H and K lines and the infrared triplet. With the consideration of fine structures of solar plages, a two-component atmospheric model is constructed by keeping the cool component to be the quiet atmosphere. Three cases of the hot component are given for different filling factors where the temperature and density distribution are adjusted in order to reproduce the seven observed spectral profiles. We also briefly discuss the influence of the column density at the base of the corona, m0, and the macro-turbulent velocity on the required filling factor and computed profiles. The two-component model is compared with precious one-component semi-empirical models. The limitation of the model is pointed out and further improvement is indicated. 相似文献
44.
A Dirac picture perturbation theory is developed for the time evolution operator in classical dynamics in the spirit of the Schwinger–Feynman–Dyson perturbation expansion and detailed rules are derived for computations. Complexification formalisms are given for the time evolution operator suitable for phase space analyses, and then extended to a two-dimensional setting for a study of the geometrical Berry phase as an example. Finally a direct integration of Hamilton's equations is shown to lead naturally to a path integral expression, as a resolution of the identity, as applied to arbitrary functions of generalized coordinates and momenta. 相似文献
45.
Fundamental processes in long air gap discharges 总被引:2,自引:0,他引:2
I. Gallimberti G. Bacchiega Anne Bondiou-Clergerie Philippe Lalande 《Comptes Rendus Physique》2002,3(10):854
The development of atmospheric lightning is initiated and sustained by the formation in virgin air of ‘streamer corona’ and ‘leader’ discharges, very similar to those observed in laboratory long sparks. Therefore, the experimental and theoretical investigations of these laboratory discharges have become of large interest to improve the physical knowledge of the lightning process and to develop self-consistent models that could be applied to new protection concepts.In the present paper the fundamental processes of the subsequent phases of long air gap discharges are analyzed, from the first corona inception and development to the leader channel formation and propagation. For all these processes simulations models are discussed that have been essentially derived and simplified by the authors, in order to develop sequential time-dependent simulation of the laboratory breakdown, with both positive and negative voltages. The possibility of extending these models to the case of natural lightning is discussed in the companion paper, presented in this same volume. To cite this article: I. Gallimberti et al., C. R. Physique 3 (2002) 1335–1359. 相似文献
46.
The spin-1 Ising model, which is equivalent to the three-component lattice gas model, is used to study wetting transitions in three-component surfactant systems consisting of an oil, water, and a nonionic surfactant. Phase equilibria, interfacial profiles, and interfacial tensions for three-phase equilibrium are determined in mean field approximation, for a wide range of temperature and interaction parameters. Surfactant interaction parameters are found to strongly influence interfacial tensions, reducing them in some cases to ultralow values. Interfacial tensions are used to determine whether the middle phase, rich in surfactant, wets or does not wet the interface between the oil-rich and water-rich phases. By varying temperature and interaction parameters, a wetting transition is located and found to be of the first order. Comparison is made with recent experimental results on wetting transitions in ternary surfactant systems.This paper is dedicated to J. K. Percus in honor of his 65th birthday. 相似文献
47.
通过分析计算,设计了一种大口径宽视场折射式红外相机光学系统。该系统设计用于超长线阵扫描红外相机的地面演示成像,它能同时对短波2μm—3μm、中波3μm—4.5μm双波段成像,且同时具有24°的大视场和150mm的宽口径,成像质量接近衍射极限。该系统在航天遥感领域应用广泛。 相似文献
48.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
49.
50.
中国证券市场股指波动的条件异方差特性分析 总被引:6,自引:0,他引:6
股指的波动具有持续性、集聚性 ,如何进行判别 ?本文用 Garch模型理论探讨沪深股指的这种条件异方差特征 ,进一步分析波动是否影响股指未来变化 ,以及股市对利好、利空的消息是否存在不对称的反映。同时 ,比较不同类型的股指的共性及差异 ,并对上述现象作了解释和说明。 相似文献