全文获取类型
收费全文 | 21638篇 |
免费 | 2281篇 |
国内免费 | 2382篇 |
专业分类
化学 | 5617篇 |
晶体学 | 105篇 |
力学 | 2482篇 |
综合类 | 319篇 |
数学 | 14161篇 |
物理学 | 3617篇 |
出版年
2024年 | 49篇 |
2023年 | 246篇 |
2022年 | 375篇 |
2021年 | 500篇 |
2020年 | 660篇 |
2019年 | 634篇 |
2018年 | 601篇 |
2017年 | 715篇 |
2016年 | 806篇 |
2015年 | 589篇 |
2014年 | 999篇 |
2013年 | 1867篇 |
2012年 | 1089篇 |
2011年 | 1192篇 |
2010年 | 1067篇 |
2009年 | 1314篇 |
2008年 | 1466篇 |
2007年 | 1500篇 |
2006年 | 1247篇 |
2005年 | 1129篇 |
2004年 | 965篇 |
2003年 | 914篇 |
2002年 | 831篇 |
2001年 | 696篇 |
2000年 | 655篇 |
1999年 | 651篇 |
1998年 | 546篇 |
1997年 | 496篇 |
1996年 | 389篇 |
1995年 | 325篇 |
1994年 | 261篇 |
1993年 | 225篇 |
1992年 | 171篇 |
1991年 | 175篇 |
1990年 | 117篇 |
1989年 | 99篇 |
1988年 | 86篇 |
1987年 | 66篇 |
1986年 | 68篇 |
1985年 | 87篇 |
1984年 | 72篇 |
1983年 | 43篇 |
1982年 | 53篇 |
1981年 | 55篇 |
1980年 | 41篇 |
1979年 | 49篇 |
1978年 | 31篇 |
1977年 | 32篇 |
1976年 | 23篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
In the pursuit to enlarge the library of polyimide materials for energy applications, new polyimide/MWCNTs composite films have been developed by MWCNTs-assisted polycondensation reaction of a hydroxyl and triphenylmethane-containing diamine with benzophenone tetracarboxylic dianhydride targeting to highlight their electrical storage capability as flexible electrodes in micro-supercapacitors (mSCs). The Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, UV–vis, fluorescence, and Raman spectroscopies were used to demonstrate the evolution of interfacial interactions between MWCNTs and the precursors (diamine monomer and intermediate polyamidic acid) and polyimide matrix that proved to be the origin of MWCNTs homogeneous dispersion. Thus, composite films incorporating 1, 3, 5, and 10 w.t.% MWCNTs were obtained and thoroughly investigated with regard to their morphology, mechanical behavior, thermal stability, and electrical conductivity. The electrochemical performance of these composites was first analyzed in a classical three-electrode cell by cyclic voltammetry and galvanostatic charge-discharge in both aqueous and organic electrolyte systems. By far, the best electrical storage capacity was obtained with the composite polyimide film containing 10% MWCNTs that was further used as both active material and current collector in a flexible symmetric mSC realized by a straightforward and low-cost procedure. In the attempt to better exploit the advantages of this composite film, it was layered with a graphite-containing paint and tested as an electrode in a flexible mSC, which provided satisfactory results. To our knowledge, this is the first report on the electrical charge storage capability of a polyimide/MWCNTs free-standing film as a flexible electrode in mSCs, which do not require time- and resource-consuming processing steps. 相似文献
4.
《Indagationes Mathematicae》2021,32(1):55-85
We show that the differential structure of the orbit space of a proper action of a Lie group on a smooth manifold is weakly reflexive. This implies that the orbit space is a differentiable space in the sense of Smith, which ensures that the orbit space has an exterior algebra of differential forms, that satisfies Smith’s version of de Rham’s theorem. Because the orbit space is a locally closed subcartesian space, it has vector fields and their flows. 相似文献
5.
A finite support product of clones of Jensen's minimal singleton forcing is used to define a model in which any non-empty analytically definable set of reals contains an analytically definable real (the full basis theorem), but there is no analytically definable wellordering of the reals. 相似文献
6.
7.
8.
Liang Zhao 《Journal of Differential Equations》2019,266(9):5615-5624
In this paper, let be n-dimensional noncompact metric measure space which satisfies Poincaré inequality with some Ricci curvature condition. We obtain a Liouville theorem for positive weak solutions to weighted p-Lichnerowicz equation where are real constants. 相似文献
9.
10.