全文获取类型
收费全文 | 19594篇 |
免费 | 721篇 |
国内免费 | 534篇 |
学科分类
数理化 | 20849篇 |
出版年
2024年 | 31篇 |
2023年 | 168篇 |
2022年 | 261篇 |
2021年 | 263篇 |
2020年 | 419篇 |
2019年 | 511篇 |
2018年 | 474篇 |
2017年 | 382篇 |
2016年 | 362篇 |
2015年 | 387篇 |
2014年 | 764篇 |
2013年 | 1044篇 |
2012年 | 608篇 |
2011年 | 1573篇 |
2010年 | 1114篇 |
2009年 | 1321篇 |
2008年 | 1509篇 |
2007年 | 1360篇 |
2006年 | 1076篇 |
2005年 | 891篇 |
2004年 | 743篇 |
2003年 | 598篇 |
2002年 | 599篇 |
2001年 | 353篇 |
2000年 | 379篇 |
1999年 | 406篇 |
1998年 | 317篇 |
1997年 | 281篇 |
1996年 | 305篇 |
1995年 | 285篇 |
1994年 | 296篇 |
1993年 | 249篇 |
1992年 | 217篇 |
1991年 | 143篇 |
1990年 | 123篇 |
1989年 | 119篇 |
1988年 | 88篇 |
1987年 | 87篇 |
1986年 | 80篇 |
1985年 | 118篇 |
1984年 | 88篇 |
1983年 | 56篇 |
1982年 | 91篇 |
1981年 | 68篇 |
1980年 | 53篇 |
1979年 | 41篇 |
1978年 | 43篇 |
1977年 | 35篇 |
1976年 | 37篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
A New Triterpene from the Orchid Pholidota yunnanensis 总被引:2,自引:0,他引:2
ZhiMingBI ZhengTaoWANG LuoShanXU 《中国化学快报》2004,15(10):1179-1181
A new triterpene, 25-methylenecyclopholidonyl p-hydroxy-trans-cinnamate, was isolated from a orchid Pholidota yunnanensis. The structure elucidation and ^1H, ^13C-NMR assignments were achieved by spectral and chemical method. 相似文献
32.
Walter Benz 《Monatshefte für Mathematik》2004,141(1):1-10
The lines of euclidean and hyperbolic geometries are characterized as metric lines in the sense of Blumenthal–Menger, and the lines of spherical and elliptic geometry as periodic ones. In euclidean geometries there do not exist periodic lines. 相似文献
33.
Murad Özaydin 《Journal of Functional Analysis》2004,215(1):241-252
We classify all functions on a locally compact, abelian group giving equality in an entropy inequality generalizing the Heisenberg Uncertainty Principle. In particular, for functions on a real line, we proof a conjecture of Hirschman published in 1957. 相似文献
34.
B. Amaziane M. Goncharenko L. Pankratov 《Mathematical Methods in the Applied Sciences》2005,28(15):1847-1865
We study the asymptotic behaviour of the solution of a stationary quasilinear elliptic problem posed in a domain Ω(ε) of asymptotically degenerating measure, i.e. meas Ω(ε) → 0 as ε → 0, where ε is the parameter that characterizes the scale of the microstructure. We obtain the convergence of the solution and the homogenized model of the problem is constructed using the notion of convergence in domains of degenerating measure. Proofs are given using the method of local characteristics of the medium Ω(ε) associated with our problem in a variational form. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
35.
Dorina Mitrea Marius Mitrea Jill Pipher 《Journal of Fourier Analysis and Applications》1997,3(2):131-192
We study boundary value problems for the time-harmonic form of the Maxwell equations, as well as for other related systems
of equations, on arbitrary Lipschitz domains in the three-dimensional Euclidean space. The main goal is to develop the corresponding
theory for Lp-integrable bounday data for optimal values of p's. We also discuss a number of relevant applications in electromagnetic scattering. 相似文献
36.
37.
38.
Summary In this paper, we develop a framework suitable for performing a multiresolution analysis using univariate spline spaces of arbitrary degree and with non-uniform knot-sequences. To this end, we show, among other things, the existence of compactly supported prewavelets and of prewavelets that are globally supported, but decay exponentially. In each case we obtain a decomposition of a fine spline space as a sum of a coarse spline space plus a spline space spanned by prewavelets. 相似文献
39.
In this paper we generalize to coisotropic actions of compact Lie groups a theorem of Guillemin on deformations of Hamiltonian
structures on compact symplectic manifolds. We show how one can reconstruct from the moment polytope the symplectic form on
the manifold.
Received: 21 March 2006 相似文献
40.
The main results of the paper are as follows: covering characterizations of wQN-spaces, covering characterizations of QN-spaces and a theorem saying that Cp(X) has the Arkhangel'ski?ˇ property (α1) provided that X is a QN-space. The latter statement solves a problem posed by M. Scheepers [M. Scheepers, Cp(X) and Arhangel'ski?ˇ's αi-spaces, Topology Appl. 89 (1998) 265-275] and for Tychonoff spaces was independently proved by M. Sakai [M. Sakai, The sequence selection properties of Cp(X), Preprint, April 25, 2006]. As the most interesting result we consider the equivalence that a normal topological space X is a wQN-space if and only if X has the property S1(Γshr,Γ). Moreover we show that X is a QN-space if and only if Cp(X) has the property (α0), and for perfectly normal spaces, if and only if X has the covering property (β3). 相似文献