全文获取类型
收费全文 | 12087篇 |
免费 | 1073篇 |
国内免费 | 1446篇 |
专业分类
化学 | 777篇 |
晶体学 | 17篇 |
力学 | 695篇 |
综合类 | 322篇 |
数学 | 10740篇 |
物理学 | 2055篇 |
出版年
2024年 | 14篇 |
2023年 | 127篇 |
2022年 | 120篇 |
2021年 | 200篇 |
2020年 | 255篇 |
2019年 | 311篇 |
2018年 | 270篇 |
2017年 | 314篇 |
2016年 | 349篇 |
2015年 | 277篇 |
2014年 | 534篇 |
2013年 | 794篇 |
2012年 | 492篇 |
2011年 | 702篇 |
2010年 | 648篇 |
2009年 | 849篇 |
2008年 | 939篇 |
2007年 | 962篇 |
2006年 | 798篇 |
2005年 | 755篇 |
2004年 | 551篇 |
2003年 | 637篇 |
2002年 | 541篇 |
2001年 | 427篇 |
2000年 | 491篇 |
1999年 | 423篇 |
1998年 | 399篇 |
1997年 | 328篇 |
1996年 | 229篇 |
1995年 | 133篇 |
1994年 | 135篇 |
1993年 | 82篇 |
1992年 | 64篇 |
1991年 | 60篇 |
1990年 | 45篇 |
1989年 | 32篇 |
1988年 | 33篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 40篇 |
1984年 | 38篇 |
1983年 | 17篇 |
1982年 | 30篇 |
1981年 | 15篇 |
1980年 | 21篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1976年 | 11篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
941.
In this paper, we shall introduce and characterize simultaneous quasi-Chebyshev (and weakly-Chebyshev) subspaces of normed spaces with respect to a bounded set S by using elements of the dual space. 相似文献
942.
Ljubomir ?iri? Vladimir Rako?evi? 《Journal of Computational and Applied Mathematics》2010,233(11):2966-5789
In this paper, the concept of a pair of non-linear contraction type mappings in a metric space of hyperbolic type is introduced and the conditions guaranteeing the existence of a common fixed point for such non-linear contractions are established. Presented results generalize and improve some of the known results. An example is constructed to show that our theorems are genuine generalizations of the main theorems of Assad, ?iri?, Khan et al., Rhoades and Imdad and Kumar. One of the possible applications of our results is also presented. 相似文献
943.
Oluseye K. Onajole Maya M. Makatini Patrick Govender Thavendran Govender Glenn E. M. Maguire Hendrik G. Kruger 《Magnetic resonance in chemistry : MRC》2010,48(3):249-255
The synthesis and complete NMR elucidation of eight novel pentacycloundecane (PCU) derivatives are reported. These compounds are precursors in the synthesis of PCU‐based anti‐tuberculosis (TB) agents and potential human immunodeficiency virus (HIV) protease inhibitors. Two‐dimensional (2D) NMR techniques were used to assign the NMR spectra for these compounds. Substitution of the cage molecule at (C‐8/11) further complicates the assignment, since some of the substituted alkyl chain groups overlap with the cage proton signals. The side chain heteroatoms also introduce a rare through‐space deshielding effect to some of the carbon atoms of the cage skeleton. Ring strain in the rigid cage skeleton appears to induce drastic electronic changes in some parts of the cage framework. This observation is more dramatic for the C‐4 methylene group of the cage diols and the cage ethers. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
944.
In this paper we study static spaces introduced in Hawking and Ellis (1975) [1], Fischer and Marsden (1975) [3] and Riemannian manifolds possessing solutions to the critical point equation introduced in Besse (1987) [11], Hwang (2000) [12]. In both cases, on the manifolds there is a function satisfying a particular Ricci–Hessian type equation (1.6). With an idea similar to that used in Cao et al. (2012) [15], [16], we have made progress in solving the problem raised in Fischer and Marsden (1975) [3] of classifying vacuum static spaces and in proving the conjecture proposed in Besse (1987) [11] concerning manifolds admitting solutions to the critical point equation in general dimensions. We obtain even stronger results in dimension 3. 相似文献
945.
Shigeru Arimoto Mark Spivakovsky Hiromu Ohno Peter Zizler Keith F. Taylor Tokio Yamabe Paul G. Mezey 《International journal of quantum chemistry》2001,84(4):389-400
The present Part VI of this series of articles provides a mathematical and methodical link between (i) fundamental methodology in the repeat space theory (RST), which is referred to as the approach via the aspect of form and general topology and which has universal unifying power to handle additivity problems of molecules that have many identical moieties, and (ii) frontier electron theory of reactivity indices. Using theoretical tools required to link (i) and (ii), we establish a theorem from which the Generalized Alpha Existence Theorem (a theorem essential in the RST and proved in the previous Part V) directly follows. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 389–400, 2001 相似文献
946.
947.
In this paper we establish characterizations of Asplund spaces in terms of conditions ensuring the metric inequality and intersection formulae. Then we establish chain rules for the limiting Fréchet subdifferentials. Necessary conditions for constrained optimization problems with non-Lipschitz data are derived. 相似文献
948.
We study the connection between equations which approximate an initial abstract linear equation and the adjoint one. We prove that the operator which is adjoint to the approximating one approximates the adjoint operator. As examples we consider adjoint linear integral equations and mutually dual linear programming problems. 相似文献
949.
基于平稳小波和相空间重构的激光混沌预测 总被引:2,自引:2,他引:0
提出了一种激光混沌时间序列预测算法.该算法通过平稳小波分解,将原始数据序列分解为与原序列等长的尺度系数和小波系数,利用坐标延迟理论,重建各级尺度系数和各级小波系数的相空间,再根据混沌吸引子的稳定性和分形性,在相空间中对尺度系数和小波系数进行预测,进而通过平稳小波重构算法,实现了时间序列的非线性预测.该算法对数据可以进行更平滑的处理,比无小波算法预测的时间范围更长.通过仿真试验说明,原始时间数据序列被成功的重建,说明算法能够有效的对非线性动态系统的时间序列进行建模和预测. 相似文献
950.