全文获取类型
收费全文 | 554篇 |
免费 | 57篇 |
国内免费 | 86篇 |
专业分类
化学 | 300篇 |
晶体学 | 4篇 |
力学 | 58篇 |
数学 | 203篇 |
物理学 | 132篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 18篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 27篇 |
2018年 | 23篇 |
2017年 | 12篇 |
2016年 | 25篇 |
2015年 | 20篇 |
2014年 | 21篇 |
2013年 | 23篇 |
2012年 | 37篇 |
2011年 | 42篇 |
2010年 | 34篇 |
2009年 | 31篇 |
2008年 | 43篇 |
2007年 | 41篇 |
2006年 | 35篇 |
2005年 | 27篇 |
2004年 | 14篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 19篇 |
1996年 | 27篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有697条查询结果,搜索用时 15 毫秒
31.
32.
Peng Zhao Juping Yang Yuming Shang Li Wang Mou Fang Jianlong Wang Xiangming He 《天然气化学杂志》2015,(2):138-144
Surface chemical modification of polyolefin separators for lithium ion batteries is attempted to reduce the thermal shrinkage, which is important for the battery energy density. In this study, we grafted organic/inorganic hybrid crosslinked networks on the separators, simply by grafting polymerization and condensation reaction. The considerable silicon-oxygen crosslinked heat-resistance networks are responsible for the reduced thermal shrinkage. The strong chemical bonds between networks and separators promise enough mechanical support even at high temperature. The shrinkage at 150 C for 30 min in the mechanical direction was 38.6% and 4.6% for the pristine and present graft-modified separators, respectively. Meanwhile, the grafting organic-inorganic hybrid crosslink networks mainly occupied part of void in the internal pores of the separators, so the thicknesses of the graft-modified separators were similar with the pristine one. The half cells prepared with the modified separators exhibited almost identical electrochemical properties to those with the commercial separators, thus proving that, in order to enhance the thermal stability of lithium ion battery, this kind of grafting-modified separators may be a better alternative to conventional silica nanoparticle layers-coated polyolefin separators. 相似文献
33.
34.
Yuming Liu 《Proceedings of the American Mathematical Society》2003,131(9):2657-2662
In this paper, we assume that algebras are finite dimensional algebras with 1 over a fixed field and modules over an algebra are finitely generated left unitary modules. Let and be two algebras (where is a splitting field for and ) with no semisimple summands. If two bimodules and induce a stable equivalence of Morita type between and , and if maps any simple -module to a simple -module, then is a Morita equivalence. This conclusion generalizes Linckelmann's result for selfinjective algebras. Our proof here is based on the construction of almost split sequences.
35.
Xie Wen Xiong Caidong Wang Xiangru Wang Zhigang Liu Yuming 《International Journal of Infrared and Millimeter Waves》2008,29(4):406-415
In this paper, a new type of gain guiding fiber is presented, with a parabolic-profile for both the gain and index guiding.
Theoretical investigation shows that the core diameter of such fiber may be up to 200 μm while propagating with single-mode. 相似文献
36.
A large size and high optical quality Nd:GdCOB crystal was obtained by CZ pulling method. The crystals were cut in two sample with the same dimension of 3×3×8mm3. 相似文献
37.
In this article, the authors study some basic properties of the so-called quasilinear- additive functions, and some applications to the special functions of quasiconformal analysis are specified. 相似文献
38.
39.
This paper is concerned with eigenvalues of perturbed second-order vector discrete Sturm–Liouville problems. By some variational properties of eigenvalues of discrete Sturm–Liouville problems, error estimates of eigenvalues of perturbed problems, sufficiently close to a given Sturm–Liouville problem, are given under a certain non-singularity condition. Perturbations of the coefficient functions of the difference equation, the weight function, and the coefficients of the boundary condition are all considered. This, together with higher-dimension involved, results in a certain complexity of the problem and difficulty of study. As a direct consequence, continuous dependence of eigenvalues on problems is obtained under the non-singularity condition. In addition, an example is presented to illustrate the necessity of the non-singularity condition. 相似文献
40.
讨论了n 元指数平均和对数平均的凸性、S - 凸性、几何凸性及S - 几何凸性, 证明了:(1) n 元指数平均是S - 凹的和S - 几何凸的; (2) n 元第一对数平均是S - 凹的; (3) n 元第二对数平均是凹的和几何凸的. 最后提出了二个悬而未决的问题. 相似文献