全文获取类型
收费全文 | 5479篇 |
免费 | 359篇 |
国内免费 | 220篇 |
专业分类
化学 | 485篇 |
晶体学 | 9篇 |
力学 | 905篇 |
综合类 | 38篇 |
数学 | 1611篇 |
物理学 | 3010篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 67篇 |
2021年 | 107篇 |
2020年 | 112篇 |
2019年 | 109篇 |
2018年 | 92篇 |
2017年 | 154篇 |
2016年 | 181篇 |
2015年 | 181篇 |
2014年 | 415篇 |
2013年 | 413篇 |
2012年 | 224篇 |
2011年 | 286篇 |
2010年 | 222篇 |
2009年 | 307篇 |
2008年 | 321篇 |
2007年 | 363篇 |
2006年 | 290篇 |
2005年 | 229篇 |
2004年 | 215篇 |
2003年 | 203篇 |
2002年 | 166篇 |
2001年 | 165篇 |
2000年 | 192篇 |
1999年 | 153篇 |
1998年 | 135篇 |
1997年 | 116篇 |
1996年 | 78篇 |
1995年 | 70篇 |
1994年 | 54篇 |
1993年 | 58篇 |
1992年 | 51篇 |
1991年 | 43篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 29篇 |
1987年 | 29篇 |
1986年 | 19篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1977年 | 8篇 |
1973年 | 12篇 |
1972年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有6058条查询结果,搜索用时 15 毫秒
41.
42.
Stéphane Roux 《Journal of statistical physics》1987,48(1-2):201-213
We introduce a family of stochastic processes which are a natural extension of Brownian motion to a tensor form. This allows us to solve a Dirichlet problem of linear elasticity obeying Lamé's equation, [1–(d– 1)]2V(x)+ [·V(x)]=0. 相似文献
43.
44.
In the present study, aluminium and mechanically alloyed (36 h) Fe/B (50 wt%) are mixed. Al+20 (wt%) Fe/B mixture has been studied by differential thermal analysis to determine the aluminium quantity that is supposed to melt and afterwards does not solidify as it reacts with Fe/B powder. The different areas between endothermic reaction (melting peak) and exothermic reaction (solidification peak) allow in knowing the quantity of aluminium that reacts with Fe/B and the amount of intermetallic phases formed at high temperature. In order to follow the process, compacts were sintered at different temperatures (700, 800, 900, 1000 and 1200 °C), in N2/10H2/0.1CH4 atmosphere. Microstructure was evaluated by image analysis and the results obtained by both techniques are compared. 相似文献
45.
Andrea Posilicano 《Potential Analysis》1996,5(3):241-271
We prove a convergence theorem for sequences of Diffusion Processes corresponding to Dirichlet Forms of the kind
.We obtain convergence in total variation norm of the corresponding probability measures on the path space C(+;d) under hypotheses which, for example, are satisfied in the case of H
loc
1
(
d
)-convergence of the 's, but we can allow more singular situations as regards the approximating sequences. We use then these results to give a criterion of convergence for generalized Schrödinger operators in which the potential function should not necessarily exists as a measurable function. We obtain convergence not only in strong resolvent sense, but we also obtain convergence in the uniform operator topology up to sets of arbitrarily small Lebesgue measure. Applications to the problem of the approximation of ordinary Schrödinger operators by generalized ones corresponding to zero-range interactions are given. 相似文献
46.
LetX be a Brownian motion defined on the line (withX(0)=0) and letY be an independent Brownian motion defined on the nonnegative real numbers. For allt0, we define theiterated Brownian motion (IBM),Z, by setting
. In this paper we determine the exact uniform modulus of continuity of the process Z.Research supported by NSF grant DMS-9122242. 相似文献
47.
Laurent Serlet 《Journal of Theoretical Probability》1996,9(3):561-578
We study super-Brownian motion inR
d
starting from a nontrivial finite measure and conditioned to nonextinction as defined by Evans. If (Y
t
)
t0
denotes this process, we provide a new approach to the immortal particle representation of (Y
t
)
t0
. We then show that the measureZ onR
d
defined byZ(B)=
o
1
Y
t
(B) dt is almost surely finite on compact sets whend5 and almost surely infinite on every ball whend4. 相似文献
48.
本文研究了 PVDF-P(VDF-HFE)以及 PVDF-P(VDF-TFE)共混体系的压电、介电、力学松弛谱。其松弛转变过程基本与 PVDF 的相似。α,β,γ压电松弛峰分别位于40~120℃,-40℃,-85℃附近。实验结果表明后一体系的压电性大于前一体系的。同时,PVDF-P(VDF-TFE)的压电性也大于PVDF-PMMA 共混体系的。选择第二组分时,以介电常数高,模量小而本身又具有压电性的,更有助于共混薄膜压电性的提高。在同样的极化条件下,经拉伸的 P(VDF-TFE)薄膜,其压电性大于未经拉伸的薄膜,这表明分子的取向对薄膜的压电性也有影响。TSC 表明,42℃的松弛峰与晶区表面捕获的空间电荷有关,对压电性也有一定的贡献。 相似文献
49.
50.
Ch. Linga Raju K.V. Narasimhulu N.O. Gopal J.L. Rao B.C.V. Reddy 《Journal of Molecular Structure》2005,754(1-3):100-105
Electron paramagnetic resonance (EPR) studies have been carried out on VO2+ ions doped in single crystals of ferroelectric material, potassium thiourea bromide (PTB) at room temperature and in the temperature range 103–343 K on X-band MW frequency. An isotropic octet spectrum characteristic of VO2+ ion was obtained due to the fast re-orientation of the VO2+ in PTB lattice, which exhibits glassy nature at certain range around room temperature. The temperature dependant EPR spectra of VO2+ ions in this host lattice has been attributed to the occurrence of multiple phase transitions due to the combined environment effects of KBr and thiourea materials in the single crystal. From the optical absorption spectrum, the crystal field splitting parameter Dq, tetragonal parameters Ds and Dt have been evaluated and discussed. 相似文献