全文获取类型
收费全文 | 14129篇 |
免费 | 1159篇 |
国内免费 | 1639篇 |
专业分类
化学 | 1257篇 |
晶体学 | 44篇 |
力学 | 808篇 |
综合类 | 309篇 |
数学 | 11643篇 |
物理学 | 2866篇 |
出版年
2024年 | 21篇 |
2023年 | 160篇 |
2022年 | 173篇 |
2021年 | 253篇 |
2020年 | 275篇 |
2019年 | 344篇 |
2018年 | 310篇 |
2017年 | 376篇 |
2016年 | 376篇 |
2015年 | 318篇 |
2014年 | 595篇 |
2013年 | 1023篇 |
2012年 | 544篇 |
2011年 | 794篇 |
2010年 | 705篇 |
2009年 | 961篇 |
2008年 | 1066篇 |
2007年 | 1125篇 |
2006年 | 917篇 |
2005年 | 855篇 |
2004年 | 649篇 |
2003年 | 736篇 |
2002年 | 646篇 |
2001年 | 496篇 |
2000年 | 543篇 |
1999年 | 513篇 |
1998年 | 495篇 |
1997年 | 379篇 |
1996年 | 268篇 |
1995年 | 153篇 |
1994年 | 154篇 |
1993年 | 94篇 |
1992年 | 81篇 |
1991年 | 70篇 |
1990年 | 50篇 |
1989年 | 40篇 |
1988年 | 41篇 |
1987年 | 27篇 |
1986年 | 20篇 |
1985年 | 42篇 |
1984年 | 41篇 |
1983年 | 16篇 |
1982年 | 36篇 |
1981年 | 19篇 |
1980年 | 26篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 17篇 |
1976年 | 11篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
PURE STATE APPROACH TO C(x)_αZ_nLIBINGREN;LINQING(InstituteofMathematics,AcademiaSinica,Beijing100080,China.Projectsupportedbyth?.. 相似文献
112.
We prove that a locally compact ANR-space X is a Q-manifold if and only if it has the Disjoint Disk Property (DDP), all points of X are homological Z
∞-points and X has the countable-dimensional approximation property (cd-AP), which means that each map f: K → X of a compact polyhedron can be approximated by a map with the countable-dimensional image. As an application we prove that
a space X with DDP and cd-AP is a Q-manifold if some finite power of X is a Q-manifold. If some finite power of a space X with cd-AP is a Q-manifold, then X
2 and X × [0, 1] are Q-manifolds as well. We construct a countable family χ of spaces with DDP and cd-AP such that no space X ∈ χ is homeomorphic to the Hilbert cube Q whereas the product X × Y of any different spaces X, Y ∈ χ is homeomorphic to Q. We also show that no uncountable family χ with such properties exists.
This work was supported by the Slovenian-Ukrainian (Grant No. SLO-UKR 04-06/07) 相似文献
113.
Jim Foster 《Journal of Combinatorial Theory, Series A》2007,114(8):1515-1525
We show that for an n-gon with unit diameter to have maximum area, its diameter graph must contain a cycle, and we derive an isodiametric theorem for such n-gons in terms of the length of the cycle. We then apply this theorem to prove Graham's 1975 conjecture that the diameter graph of a maximal 2m-gon (m?3) must be a cycle of length 2m−1 with one additional edge attached to it. 相似文献
114.
Florence Newberger 《Geometriae Dedicata》2003,97(1):215-249
The goal of this paper is to provide a tool, the Global Measure Formula, that will facilitate the study of the limit set of discrete geometrically finite groups of isometries of the rank one symmetric spaces. We consider the shadow of a ball from a fixed reference point onto the boundary, and prove a formula that describes the measure of the shadow in terms of the center of the shadowed ball, generalizing a result from real hyperbolic geometry. 相似文献
115.
116.
By introducing an imaginary space transform curvature ρs, a complex space called Riemannian space is constructed, in which the light propagating in free space has the trajectory
of straight line while propagating. Moreover, this curvature couples with that of the wave front of the paraxial beam ρw, and therefore a complex curvature ρc is constructed, which can be employed to investigate the behavior of the light transmission and to generalize the ABCD law.
Project supported by the National Hi-Tech Inertial Confinement Fusion Committee, the Guangdong Natural Science Foundation
the Postdoctoral Foundation of Guangdong and National Postdoctoral Foundation of China. 相似文献
117.
A new method of using time-averaged digital speckle pattern interferometry for the quantitative measurement of vibration amplitude was developed. Signal processing techniques especially the Hilbert transformation for quantitative evaluation of the Bessel fringes obtained in time-averaged digital speckle pattern interferometry were explored. The quadrature signal after Hilbert transformation is equivalent to a 90° phase-shifted interferogram for a monotonically increasing or decreasing phase function. An algorithm was developed for Bessel fringe contrast enhancement and phase extraction. The techniques were tested numerically and experimentally. Sub-fringe quantification of the time-averaged vibration fringes is realised with the proposed method. Compared with the commonly used phase shift method which requires a minimum of two images for image processing, this method requires only one fringe pattern for data extraction. 相似文献
118.
本文主要研究了 Banach 空间上交换算子组的张量积以及 Banach 代数的张量积中交换元组的 Taylor 联合谱,推广了 Vasilescu,F.H.及 Wrobel,V.等人结果。 相似文献
119.
Hans C. Fogedby 《Journal of statistical physics》1992,69(1-2):411-425
We elaborate in some detail on a new phase space approach to complexity, due to Y.-C. Zhang. We show in particular that the connection between maximal complexity and power law noise or correlations can be derived from a simple variational principle. For a 1D signal we find 1/f noise, in accordance with Zhang. 相似文献
120.
A multidimensional version of the first Darboux problem is considered for a model second-order degenerating hyperbolic equation. Using the technique of functional spaces with a negative norm, the correct formulation of this problem in the Sobolev weighted space is proved. 相似文献