全文获取类型
收费全文 | 75628篇 |
免费 | 5451篇 |
国内免费 | 6970篇 |
专业分类
化学 | 26516篇 |
晶体学 | 292篇 |
力学 | 6724篇 |
综合类 | 1319篇 |
数学 | 31424篇 |
物理学 | 21774篇 |
出版年
2023年 | 593篇 |
2022年 | 884篇 |
2021年 | 1232篇 |
2020年 | 1391篇 |
2019年 | 1657篇 |
2018年 | 1447篇 |
2017年 | 1698篇 |
2016年 | 1949篇 |
2015年 | 1703篇 |
2014年 | 2586篇 |
2013年 | 4841篇 |
2012年 | 2963篇 |
2011年 | 3344篇 |
2010年 | 2909篇 |
2009年 | 4167篇 |
2008年 | 4696篇 |
2007年 | 4824篇 |
2006年 | 4544篇 |
2005年 | 3876篇 |
2004年 | 3490篇 |
2003年 | 3596篇 |
2002年 | 3294篇 |
2001年 | 2751篇 |
2000年 | 2692篇 |
1999年 | 2453篇 |
1998年 | 2262篇 |
1997年 | 1897篇 |
1996年 | 1648篇 |
1995年 | 1488篇 |
1994年 | 1381篇 |
1993年 | 1165篇 |
1992年 | 1121篇 |
1991年 | 887篇 |
1990年 | 738篇 |
1989年 | 637篇 |
1988年 | 596篇 |
1987年 | 462篇 |
1986年 | 396篇 |
1985年 | 473篇 |
1984年 | 467篇 |
1983年 | 220篇 |
1982年 | 363篇 |
1981年 | 428篇 |
1980年 | 330篇 |
1979年 | 315篇 |
1978年 | 246篇 |
1977年 | 239篇 |
1976年 | 175篇 |
1974年 | 121篇 |
1973年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
71.
Well-Posedness by Perturbations of Variational Problems 总被引:3,自引:0,他引:3
Lemaire B. Ould Ahmed Salem C. Revalski J. P. 《Journal of Optimization Theory and Applications》2002,115(2):345-368
In this paper, we consider the extension of the notion of well-posedness by perturbations, introduced by Zolezzi for optimization problems, to other related variational problems like inclusion problems and fixed-point problems. Then, we study the conditions under which there is equivalence of the well-posedness in the above sense between different problems. Relations with the so-called diagonal well-posedness are also given. Finally, an application to staircase iteration methods is presented. 相似文献
72.
WANG Libin 《数学年刊B辑(英文版)》2002,23(4):439-454
The author gets a blow-up result of C1 solution to the Cauchy problem for a first order quasilinear non-strictly hyperbolic system in one space dimension. 相似文献
73.
G. Dattoli 《Journal of Mathematical Analysis and Applications》2002,269(2):716-725
Bilateral generating functions are those involving products of different types of polynomials. We show that operational methods offer a powerful tool to derive these families of generating functions. We study cases relevant to products of Hermite polynomials with Laguerre, Legendre and other polynomials. We also propose further extensions of the method which we develop here. 相似文献
74.
Filippo Bracci Roberto Tauraso Fabio Vlacci 《Journal of Mathematical Analysis and Applications》2002,270(2):1131-473
Let f,g be two commuting holomorphic self-maps of the unit disc. If f and g agree at the common Wolff point up to a certain order of derivatives (no more than 3 if the Wolff point is on the unit circle), then f≡g. 相似文献
75.
利用Riccati变换求解同谐谐振子的定态薛定谔方程,求得了能谱及态函数
关键词:
同调谐振子
本征值谱
Riccati变换法 相似文献
76.
77.
根据Pegg-Barnett位相定义, 计算了一种新的奇偶非线性相干态的位相概率分布函数, 利用数值计算方法研究了它们的位相统计性质. 数值计算结果表明:新的奇偶非线性相干态的位相特性与通常奇偶相干态的位相特性截然不同. 相似文献
78.
Maria Kordaki Athanasia Balomenou 《International Journal of Computers for Mathematical Learning》2006,11(1):99-135
This study focuses on the constructions in terms of area and perimeter in equivalent triangles developed by students aged 12–15 years-old, using the tools provided by Cabri-Geometry II [Labore (1990). Cabri-Geometry (software), Université de Grenoble]. Twenty-five students participated in a learning experiment where they were asked to construct: (a) pairs of equivalent triangles “in as many ways as possible” and to study their area and their perimeter using any of the tools provided and (b) “any possible sequence of modifications of an original triangle into other equivalent ones”. As regards the concept of area and in contrast to a paper and pencil environment, Cabri provided students with different and potential opportunities in terms of: (a) means of construction, (b) control, (c) variety of representations and (d) linking representations, by exploiting its capability for continuous modifications. By exploiting these opportunities in the context of the given open tasks, students were helped by the tools provided to develop a broader view of the concept of area than the typical view they would construct in a typical paper and pencil environment. 相似文献
79.
P.A. Ramachandran 《Numerical Methods for Partial Differential Equations》2006,22(4):831-846
Time‐dependent differential equations can be solved using the concept of method of lines (MOL) together with the boundary element (BE) representation for the spatial linear part of the equation. The BE method alleviates the need for spatial discretization and casts the problem in an integral format. Hence errors associated with the numerical approximation of the spatial derivatives are totally eliminated. An element level local cubic approximation is used for the variable at each time step to facilitate the time marching and the nonlinear terms are represented in a semi‐implicit manner by a local linearization at each time step. The accuracy of the method has been illustrated on a number of test problems of engineering significance. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006 相似文献
80.
The structural properties of polycrystalline silicon films, prepared by plasma enhanced chemical vapor deposition system, with different flow rates of SiH4/SiF4 mixtures at 300 °C were investigated. This study indicates that the low hydrogen coverage on the growing surface, under optimum fluorine radicals, will be leaded to an improvement of crystallized area as compared with case of high hydrogen coverage surface. Moreover, the studies of the role of SiH4 and SiF4 radicals show that the SiH4 radicals are important in the nucleation and growth of grains. However, SiF4 radicals are effective in the structural change of grain boundaries regions and by this way, in the present system, establish the growth of grains under the dominant 〈1 1 0〉 direction. The stress investigation indicates that addition of high flow rate of SiF4 in amorphous film, results in the nearly stress free films. Finally, we found that the changes in g-value reflect the changes in the intrinsic compressive and tensile stress in the both polycrystalline and amorphous silicon films. 相似文献