全文获取类型
收费全文 | 3698篇 |
免费 | 588篇 |
国内免费 | 664篇 |
专业分类
化学 | 2240篇 |
晶体学 | 39篇 |
力学 | 440篇 |
综合类 | 57篇 |
数学 | 601篇 |
物理学 | 1573篇 |
出版年
2024年 | 14篇 |
2023年 | 41篇 |
2022年 | 121篇 |
2021年 | 161篇 |
2020年 | 214篇 |
2019年 | 145篇 |
2018年 | 149篇 |
2017年 | 147篇 |
2016年 | 203篇 |
2015年 | 155篇 |
2014年 | 218篇 |
2013年 | 302篇 |
2012年 | 234篇 |
2011年 | 244篇 |
2010年 | 163篇 |
2009年 | 258篇 |
2008年 | 216篇 |
2007年 | 235篇 |
2006年 | 239篇 |
2005年 | 186篇 |
2004年 | 188篇 |
2003年 | 145篇 |
2002年 | 127篇 |
2001年 | 129篇 |
2000年 | 101篇 |
1999年 | 97篇 |
1998年 | 80篇 |
1997年 | 64篇 |
1996年 | 62篇 |
1995年 | 54篇 |
1994年 | 45篇 |
1993年 | 33篇 |
1992年 | 22篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1971年 | 3篇 |
1957年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有4950条查询结果,搜索用时 203 毫秒
1.
Giorgia Scetta Jianzhu Ju Nathan Selles Patrick Heuillet Matteo Ciccotti Costantino Creton 《Journal of polymer science. Part A, Polymer chemistry》2021,59(8):685-696
We investigate the cyclic mechanical behavior in uniaxial tension of three different commercial thermoplastic polyurethane elastomers (TPU) often considered as a sustainable replacement for common filled elastomers. All TPU have similar hard segment contents and linear moduli but sensibly different large strain properties as shown by X-ray analysis. Despite these differences, we found a stiffening effect after conditioning in step cyclic loading which greatly differs from the common softening (also referred as Mullins effect) observed in chemically crosslinked filled rubbers. We propose that this self-reinforcement is related to the fragmentation of hard domains, naturally present in TPU, in smaller but more numerous sub-units that may act as new physical crosslinking points. The proposed stiffening mechanism is not dissimilar to the strain-induced crystallization observed in stretched natural rubber, but it presents a persistent nature. In particular, it may cause a local reinforcement where an inhomogeneous strain field is present, as is the case of a crack propagating in cyclic fatigue, providing a potential explanation for the well-known toughness and wear resistance of TPU. 相似文献
2.
Lithium-sulfur batteries (LSBs) with high energy density and low cost have been recognized as one of the most promising next-generation energy storage systems. Although it has taken decades of development, the practical application of LSBs has been hindered by several inherent obstacles, particularly the severe shuttle effect and sluggish reaction kinetics in the sulfur cathode. Various strategies have been proposed to address these problems via rational design of electrode materials and configurations. Freestanding sulfur cathode could be a promising strategy to improve the sulfur mass loading at the cathode level and energy density of LSBs. This minireview will briefly summary the recent advances in freestanding cathodes for LSBs. The advantages and disadvantages of various freestanding cathodes are discussed and the prospects for the development of flexible cathodes are envisioned. 相似文献
3.
Quinones are electroactive species that have shown great promise for redox flow batteries due to the ability to tune their properties and to act as both negative and positive electrolytes. The following review outlines highlights of work in the last couple of years working to provide materials with higher stability, solubility, and performance. Developments toward stable negolytes have provided opportunities for potential commercial opportunities when paired with alternate chemistries. However, the stability of quinones in high potential electrolytes is still not sufficient and the number of potential quinones limited. 相似文献
4.
5.
6.
给出2005年全国部分高校研究生数学建模竞赛D题的研究背景,对参赛论文作了简要评注,并提供了一种参考解答. 相似文献
7.
8.
9.
A.J.?Lpez-Moreno 《Acta Mathematica Hungarica》2005,106(4):343-354
Summary We obtain preservation inequalities for Lipschitz constants of higher order in simultaneous approximation processes by Bernstein type operators. From such inequalities we derive the preservation of the corresponding Lipschitz spaces. 相似文献
10.
In this paper, we use weighted modules ω(?)(f,t)w to study the pointwise approximation on Szasz-type operators, and obtain the direct and converse theorem, as well as characterizations of the pointwise approximation of Jacobi-weighted Szasz-type operators. 相似文献