全文获取类型
收费全文 | 4167篇 |
免费 | 149篇 |
国内免费 | 28篇 |
专业分类
化学 | 3043篇 |
晶体学 | 13篇 |
力学 | 105篇 |
数学 | 591篇 |
物理学 | 592篇 |
出版年
2024年 | 6篇 |
2023年 | 38篇 |
2022年 | 107篇 |
2021年 | 101篇 |
2020年 | 101篇 |
2019年 | 91篇 |
2018年 | 67篇 |
2017年 | 52篇 |
2016年 | 144篇 |
2015年 | 107篇 |
2014年 | 146篇 |
2013年 | 243篇 |
2012年 | 283篇 |
2011年 | 323篇 |
2010年 | 194篇 |
2009年 | 191篇 |
2008年 | 300篇 |
2007年 | 285篇 |
2006年 | 207篇 |
2005年 | 234篇 |
2004年 | 209篇 |
2003年 | 146篇 |
2002年 | 158篇 |
2001年 | 55篇 |
2000年 | 45篇 |
1999年 | 34篇 |
1998年 | 36篇 |
1997年 | 32篇 |
1996年 | 42篇 |
1995年 | 33篇 |
1994年 | 30篇 |
1993年 | 22篇 |
1992年 | 24篇 |
1991年 | 27篇 |
1990年 | 31篇 |
1989年 | 16篇 |
1988年 | 24篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有4344条查询结果,搜索用时 0 毫秒
1.
J. C. S. Moraes E. M. Telles F. C. Cruz A. Scalabrin D. Pereira C. Garelli N. Ioli A. Moretti F. Strumia 《International Journal of Infrared and Millimeter Waves》1991,12(12):1475-1486
We report the discovery of 57 new fir laser lines from13CD3OH molecule optically pumped by a waveguide CO2 laser of 300 MHz tunability. For all lines, precise frequency offset measurements between the CO2 line center and the center of the absorbing13CD3OH line were performed using the transferred Lamb-Dip technique. We have also measured directly the frequency of seven FIR laser lines by heterodyning with already known laser lines. We present a complete list of all known laser lines (134) and frequency measurements (24) for this molecule.Work supported by CNPq, FAPESP, FAEP-Brasil, and CNR-Italia 相似文献
2.
We give a small functorial algebraic model for the 2-stage Postnikov section of the K-theory spectrum of a Waldhausen category and use our presentation to describe the multiplicative structure with respect to biexact functors. 相似文献
3.
4.
Fernando M. Lanas Janete H. Y. Vilegas Srgio Martins Elaine A. F. Gobato 《Journal of separation science》1994,17(4):237-244
An overview is presented of the analytical approaches developed by our research group over the last ten years for analysis of alternative fuel, both biomass and fossil. The alternative fuels are analyzed successively by PLC-8 (preparative liquid chromatography–group-type) fractionation and high resolution gas chromatography. Some of the possibilities for fractionation and characterization of alternative fuels are herein exemplified with sugar cane bagasse pyrolysis products. 相似文献
5.
M. Trinidad Menarguez Fernando Soria 《Rendiconti del Circolo Matematico di Palermo》1992,41(3):342-352
In this paper we study the behavior of the constants which appear in the weak type (1, 1) inequalities for maximal convolution
operators by means of discrete methods.
One of the first applications of these techniques will give us a very simple proof of the ergodic theorem. We also present
partial results in order to investigate the best constant in the weak type (1, 1) inequality for the Hardy-Littlewood centered
maximal operator in dimension one. In dimension bigger than one we also obtain some lower bounds for that constant. 相似文献
6.
Luiza Amália Moraes Luis Romero Grados 《Journal of Mathematical Analysis and Applications》2003,281(2):575-586
Let Au(BG) be the Banach algebra of all complex valued functions defined on the closed unit ball BG of a complex Banach space G which are uniformly continuous on BG and holomorphic in the interior of BG, endowed with the sup norm. A characterization of the boundaries for Au(BG) is given in case G belongs to a class of Banach spaces that includes the pre-dual of a Lorentz sequence space studied by Gowers in Israel J. Math. 69 (1990) 129-151. The non-existence of the Shilov boundary for Au(BG) is also proved. 相似文献
7.
8.
Eleonora Catsigeras Jean-Marc Gambaudo Fernando Moreira 《Proceedings of the American Mathematical Society》1998,126(1):297-304
We show that, among area contracting embeddings of the 2-disk, infinitely renormalizable maps with a bounded geometry either have positive topological entropy or correspond to a cascade of period doubling.
9.
In this paper we address a two-dimensional (2D) orthogonal packing problem, where a fixed set of small rectangles has to be placed on a larger stock rectangle in such a way that the amount of trim loss is minimized. The algorithm we propose hybridizes a placement procedure with a genetic algorithm based on random keys. The approach is tested on a set of instances taken from the literature and compared with other approaches. The computation results validate the quality of the solutions and the effectiveness of the proposed algorithm. 相似文献
10.
Julio Penin Santos Fernando J.G. Landgraf Geraldo Caixeta Guimarães 《Journal of magnetism and magnetic materials》2006
The paper describes effect of texture on the anisotropy of magnetic properties and shows that an Epstein strip arrangement including strips cut in a direction 45° to the rolling direction gives property values that are closer to the average values than the traditional RD+TD arrangement. 相似文献