全文获取类型
收费全文 | 2908篇 |
免费 | 96篇 |
国内免费 | 12篇 |
专业分类
化学 | 1793篇 |
晶体学 | 25篇 |
力学 | 109篇 |
数学 | 520篇 |
物理学 | 569篇 |
出版年
2023年 | 22篇 |
2022年 | 97篇 |
2021年 | 102篇 |
2020年 | 68篇 |
2019年 | 90篇 |
2018年 | 62篇 |
2017年 | 47篇 |
2016年 | 120篇 |
2015年 | 111篇 |
2014年 | 91篇 |
2013年 | 159篇 |
2012年 | 220篇 |
2011年 | 233篇 |
2010年 | 118篇 |
2009年 | 102篇 |
2008年 | 160篇 |
2007年 | 185篇 |
2006年 | 166篇 |
2005年 | 147篇 |
2004年 | 139篇 |
2003年 | 116篇 |
2002年 | 83篇 |
2001年 | 25篇 |
2000年 | 24篇 |
1999年 | 27篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1973年 | 4篇 |
1960年 | 5篇 |
1911年 | 2篇 |
排序方式: 共有3016条查询结果,搜索用时 171 毫秒
1.
2.
3.
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
4.
Mauro Picone 《Rendiconti del Circolo Matematico di Palermo》1997,46(1):437-455
[Estratto da una lettera al Prof. G. Bagnera] 相似文献
5.
6.
We consider the generalization of the classical P||Cmax problem (assign n jobs to m identical parallel processors by minimizing the makespan) arising when the number of jobs that can be assigned to each processor cannot exceed a given integer k. The problem is strongly NP-hard for any fixed k > 2. We briefly survey lower and upper bounds from the literature. We introduce greedy heuristics, local search and a scatter search approach. The effectiveness of these approaches is evaluated through extensive computational comparison with a depth-first branch-and-bound algorithm that includes new lower bounds and dominance criteria. 相似文献
7.
Some authors claim that reporting the best result obtained by a stochastic algorithm in a number of runs is more meaningful
than reporting some central statistic. In this short note, we analyze and refute the main argument brought in favor of this
statement. 相似文献
8.
In this paper we study a Ginzburg–Landau model which describes the behaviour of a superconducting material including thermal effects. We extend the traditional formulation of the problem, by introducing the temperature as an additional state variable. Accordingly, together with the Gor’kov–Eliashberg system, we introduce an evolution equation for the absolute temperature. We examine in detail the case which allows only variations of the concentration of superconducting electrons and of the temperature, neglecting the electromagnetic field. For this problem existence and uniqueness of the solution are shown. Finally we analyze the asymptotic behaviour of the solutions, proving that the system possesses a global attractor. 相似文献
9.
Motivated by the work of Crapo and Rota [6] on the lifting of a projective complex, we introduce a class of invariant operations associated to integral-weighted graphs, which we call graphical operations. Such operations generalize the sixth harmonic of a quadranguler set on a projective line. We determine the expansion of the graphical operations in terms of multi-linear bracket polynomials in a Grassmann-Cayley algebra. Reducibility and compositions of such invariant operations are also investigated with a number of examples.Supported by Courant Instructorship, New York University. 相似文献
10.
In this work we show that the energy associated to the linear three-dimensional magneto-elastic system decays polynomially to zero as time goes to infinity, provided the initial data is smooth enough. 相似文献