全文获取类型
收费全文 | 33886篇 |
免费 | 5696篇 |
国内免费 | 3911篇 |
专业分类
化学 | 24346篇 |
晶体学 | 365篇 |
力学 | 1910篇 |
综合类 | 190篇 |
数学 | 4233篇 |
物理学 | 12449篇 |
出版年
2024年 | 89篇 |
2023年 | 693篇 |
2022年 | 953篇 |
2021年 | 1140篇 |
2020年 | 1431篇 |
2019年 | 1341篇 |
2018年 | 1205篇 |
2017年 | 1092篇 |
2016年 | 1648篇 |
2015年 | 1618篇 |
2014年 | 1955篇 |
2013年 | 2554篇 |
2012年 | 2987篇 |
2011年 | 3170篇 |
2010年 | 2232篇 |
2009年 | 1969篇 |
2008年 | 2235篇 |
2007年 | 2006篇 |
2006年 | 1790篇 |
2005年 | 1576篇 |
2004年 | 1227篇 |
2003年 | 1044篇 |
2002年 | 1081篇 |
2001年 | 830篇 |
2000年 | 730篇 |
1999年 | 673篇 |
1998年 | 558篇 |
1997年 | 496篇 |
1996年 | 508篇 |
1995年 | 431篇 |
1994年 | 412篇 |
1993年 | 290篇 |
1992年 | 286篇 |
1991年 | 254篇 |
1990年 | 212篇 |
1989年 | 178篇 |
1988年 | 99篇 |
1987年 | 86篇 |
1986年 | 103篇 |
1985年 | 76篇 |
1984年 | 52篇 |
1983年 | 37篇 |
1982年 | 30篇 |
1981年 | 18篇 |
1980年 | 21篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
101.
Harnack inequality for some classes of Markov processes 总被引:3,自引:0,他引:3
In this paper we establish a Harnack inequality for nonnegative harmonic functions of some classes of Markov processes with jumps.
Mathematics Subject Classification (2000): Primary 60J45, 60J75, Secondary 60J25.This work was completed while the authors were in the Research in Pairs program at the Mathematisches Forschungsinstitut Oberwolfach. We thank the Institute for the hospitality.The research of this author is supported in part by NSF Grant DMS-9803240.The research of this author is supported in part by MZT grant 0037107 of the Republic of Croatia. 相似文献
102.
L. E. Payne P. W. Schaefer J. C. Song 《Mathematical Methods in the Applied Sciences》2004,27(17):2045-2053
Energy bounds are derived for Dirichlet type boundary value problems for the Navier–Stokes and Stokes equations when a combination of the solution values initially and at a later time is prescribed. The bounds are obtained by means of a differential inequality and imply uniqueness and continuous data dependence of the solutions for a range of values of the parameter in the non‐standard auxiliary condition. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
103.
In this paper, we consider Girsanov transforms of pure jump type for discontinuous Markov processes. We show that, under some quite natural conditions, the Green functions of the Girsanov transformed process are comparable to those of the original process. As an application of the general results, the drift transform of symmetric stable processes is studied in detail. In particular, we show that the relativistic α-stable process in a bounded C1,1-smooth open set D can be obtained from symmetric α-stable process in D through a combination of a pure jump Girsanov transform and a Feynman-Kac transform. From this, we deduce that the Green functions for these two processes in D are comparable. 相似文献
104.
S. P. Savin L. M. Zelenyi E. Amata J. Buechner J. Blecki S. I. Klimov B. Nikutowski J. L. Rauch S. A. Romanov A. A. Skalsky V. N. Smirnov P. Song K. Stasiewicz 《JETP Letters》2004,79(8):368-371
The study of the interaction between collisionless plasma flow and stagnant plasma revealed the presence of an outer boundary layer at the border of a geomagnetic trap, where the super-Alfvén subsonic laminar flow changes over to the dynamic regime characterized by the formation of accelerated magnetosonic jets and decelerated Alfvén flows with characteristic relaxation times of 10–20 min. The nonlinear interaction of fluctuations in the initial flow with the waves reflected from an obstacle explains the observed flow chaotization. The Cherenkov resonance of the magnetosonic jet with the fluctuation beats between the boundary layer and the incoming flow is the possible mechanism of its formation. In the flow reference system, the incoming particles are accelerated by the electric fields at the border of boundary layer that arise self-consistently as a result of the preceding wave-particle interactions; the inertial drift of the incoming ions in a transverse electric field increasing toward the border explains quantitatively the observed ion acceleration. The magnetosonic jets may carry away downstream up to a half of the unperturbed flow momentum, and their dynamic pressure is an order of magnitude higher than the magnetic pressure at the obstacle border. The appearance of nonequilibrium jets and the boundary-layer fluctuations are synchronized by the magnetosonic oscillations of the incoming flow at frequencies of 1–2 mHz. 相似文献
105.
微模塑法制备PMMA/SiO2二氧化硅杂化材料微结构 总被引:1,自引:0,他引:1
以摩尔比为 1∶1的甲基丙烯酸甲酯 (MMA)、甲基丙烯酸 (3 三乙氧基硅烷基 )丙酯 (ESMA)单体、0 .2 %(单体总量的质量分数 )的偶氮二异丁腈AIBN引发剂和四氢呋喃 (THF)溶剂 ,及 2 0 % (总质量分数 )的正硅酸乙酯TEOS合成出PMMA/SiO2 有机 无机杂化的杂化溶胶 .将溶胶在洗净的普通光学玻璃基片表面甩膜 .利用软刻蚀中的微模塑法 ,把有机硅弹性印章复制有精细图纹一面轻放在杂化溶胶膜上进行微模塑 ,外加 1N压力于12 0℃下处理 2h使溶胶凝胶化 .印章剥离后在基片表面就形成了PMMA/SiO2 有机 无机杂化材料的微图纹结构 .从微图纹的光学显微镜照片可以看出微模塑方法制备杂化材料复制的图纹精细度高 ,操作简单易行 ,是一类比较理想的微细图纹结构加工的方法 . 相似文献
106.
107.
108.
Song Jiang 《Mathematische Nachrichten》1998,190(1):169-183
We consider initial boundary value problems for the equations of the one-dimensional motion of a viscous, heat-conducting gas with density-dependent viscosity that decreases (to zero) with decreasing density. We prove that if the viscosity does not decrease to zero too rapidly, then smooth solutions exist globally in time. 相似文献
109.
关于具有给定Sylow子群正规化子的有限群Ⅱ 总被引:1,自引:0,他引:1
本文在有限可解群中解决了:任意m-秩≤2的子群闭的局部群系具有性质:“如果群G的非单位Sylow子群的正规化子属于,则群G也属于的一个充分必要条件. 相似文献
110.