全文获取类型
收费全文 | 12772篇 |
免费 | 899篇 |
国内免费 | 924篇 |
专业分类
化学 | 1346篇 |
晶体学 | 43篇 |
力学 | 659篇 |
综合类 | 150篇 |
数学 | 3421篇 |
物理学 | 2367篇 |
综合类 | 6609篇 |
出版年
2024年 | 25篇 |
2023年 | 89篇 |
2022年 | 167篇 |
2021年 | 182篇 |
2020年 | 232篇 |
2019年 | 260篇 |
2018年 | 227篇 |
2017年 | 277篇 |
2016年 | 322篇 |
2015年 | 320篇 |
2014年 | 556篇 |
2013年 | 748篇 |
2012年 | 667篇 |
2011年 | 755篇 |
2010年 | 602篇 |
2009年 | 698篇 |
2008年 | 706篇 |
2007年 | 838篇 |
2006年 | 796篇 |
2005年 | 731篇 |
2004年 | 632篇 |
2003年 | 594篇 |
2002年 | 525篇 |
2001年 | 420篇 |
2000年 | 410篇 |
1999年 | 340篇 |
1998年 | 331篇 |
1997年 | 340篇 |
1996年 | 239篇 |
1995年 | 235篇 |
1994年 | 223篇 |
1993年 | 182篇 |
1992年 | 153篇 |
1991年 | 157篇 |
1990年 | 114篇 |
1989年 | 93篇 |
1988年 | 95篇 |
1987年 | 62篇 |
1986年 | 42篇 |
1985年 | 44篇 |
1984年 | 31篇 |
1983年 | 6篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
从应用角度出发,系统地研究了Al_(63)Cu_(25)Fe_(12)合金的相变及性能特点,并初步研究了准晶体对传统铝合金表面改性的贡献。结果表明:该合金在450℃~820℃温度区间内晶体相Al_7Cu_2Fe发生同素异构转变形成稳定I相,具有较高的硬度和硬度值变化不大(650~850kgf/mm~2)的特点,可与传统铝合金复合并使其硬度和耐磨性能显著提高。 相似文献
12.
13.
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
14.
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
15.
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
16.
Mathematical Notes - 相似文献
17.
Efficient measurement of the performance index (the distance of a loading parameter from the voltage collapse point) is one of the key problems in power system operations and planning and such an index indicates the severity of a power system with regard to voltage collapse. There exist many interesting methods and ideas to compute this index. However, some successful methods are not yet mathematically justified while other mathematically sound methods are often proposed directly based on the bifurcation theory and they require the initial stationary state to be too close to the unknown turning point to make the underlying methods practical.This paper first gives a survey of several popular methods for estimating the fold bifurcation point including the continuation methods, bifurcation methods and the test function methods (Seydel's direct solution methods, the tangent vector methods and the reduced Jacobian method) and discuss their relative advantages and problems. Test functions are usually based on scaling of the determinant of the Jacobian matrix and it is generally not clear how to determine the behaviour of such functions. As the underlying nonlinear equations are of a particular type, this allows us to do a new analysis of the determinants of the Jacobian and its submatrices in this paper. Following the analysis, we demonstrate how to construct a class of test functions with a predictable analytical behaviour so that a suitable index can be produced. Finally, examples of two test functions from this class are proposed. For several standard IEEE test systems, promising numerical results have been achieved. 相似文献
18.
In this paper we study the Hankel convolution operators on the space of even and entire functions and on Schwartz distribution spaces. We characterize the Hankel convolution operators as those ones that commute with Hankel translations and with a Bessel operator. Also we prove that the Hankel convolution operators are hypercyclic and chaotic on the spaces under consideration. 相似文献
19.
20.