全文获取类型
收费全文 | 8860篇 |
免费 | 1320篇 |
国内免费 | 1031篇 |
专业分类
化学 | 2776篇 |
晶体学 | 66篇 |
力学 | 1726篇 |
综合类 | 102篇 |
数学 | 1863篇 |
物理学 | 4678篇 |
出版年
2024年 | 17篇 |
2023年 | 105篇 |
2022年 | 220篇 |
2021年 | 262篇 |
2020年 | 247篇 |
2019年 | 223篇 |
2018年 | 261篇 |
2017年 | 281篇 |
2016年 | 334篇 |
2015年 | 339篇 |
2014年 | 458篇 |
2013年 | 747篇 |
2012年 | 449篇 |
2011年 | 512篇 |
2010年 | 428篇 |
2009年 | 534篇 |
2008年 | 537篇 |
2007年 | 596篇 |
2006年 | 536篇 |
2005年 | 463篇 |
2004年 | 443篇 |
2003年 | 387篇 |
2002年 | 350篇 |
2001年 | 300篇 |
2000年 | 338篇 |
1999年 | 283篇 |
1998年 | 252篇 |
1997年 | 204篇 |
1996年 | 153篇 |
1995年 | 150篇 |
1994年 | 134篇 |
1993年 | 101篇 |
1992年 | 81篇 |
1991年 | 87篇 |
1990年 | 38篇 |
1989年 | 53篇 |
1988年 | 50篇 |
1987年 | 42篇 |
1986年 | 28篇 |
1985年 | 23篇 |
1984年 | 21篇 |
1983年 | 8篇 |
1982年 | 27篇 |
1981年 | 21篇 |
1980年 | 9篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1973年 | 14篇 |
1972年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Miklós Csörgő 《Periodica Mathematica Hungarica》2005,50(1-2):1-27
Summary This article provides a glimpse of some of the highlights of the joint work of Endre Csáki and Pál Révész since 1979. The topics of this short exploration of the rich stochastic milieu of this inspiring collaboration revolve around Brownian motion, random walks and their long excursions, local times and additive functionals, iterated processes, almost sure local and global central limit theorems, integral functionals of geometric stochastic processes, favourite sites--favourite values and jump sizes for random walk and Brownian motion, random walking in a random scenery, and large void zones and occupation times for coalescing random walks. 相似文献
22.
Hana Macková Daniela Králová Daniel Horák 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5884-5898
The aim of this study was to develop novel thermally responsive polymer microspheres with magnetic properties. Dispersion and inverse emulsion copolymerization of N‐isopropylacrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm) was investigated in the presence of γ‐Fe2O3 nanoparticles. The resulting microspheres were characterized in terms of morphology, size, polydispersity, iron content, and temperature‐dependent swelling using optical microscopy, transmission electron microscopy, scanning electron microscopy, QELS, and AAS. The effects of several variables, such as the concentration of γ‐Fe2O3, MBAAm crosslinking agent, Span 80 surfactant, 2,2′‐azobis(2‐methyloctanenitrile) (AMON) initiator, and polymerization temperature on the properties of the microspheres were studied. Swelling and thermoresponsive behavior of the microspheres containing γ‐Fe2O3 nanoparticles were also investigated. The microspheres contained about 8 wt % of iron. The presence of magnetic nanoparticles and their concentration changes did not have any significant effect on the temperature sensitivity of the composites. The particles gradually shrink into an increasingly collapsed state when the temperature is raised to 40 °C since the increase in temperature weakens the hydration and PNIPAAm chains gradually become more hydrophobic, which leads to the collapse of the particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5884–5898, 2007 相似文献
23.
24.
Settling of a large solid particle in bioconvection flow caused by gyrotactic microorganisms is investigated. The particle is released from the top of the bioconvection chamber; its settling pattern depends on whether it is released in the centre of the bioconvection plume or at its periphery. The Chimera method is utilized; a subgrid is generated around a moving particle. The method suggested by Liu and Wang (Comput. Fluid 2004; 33 :223–255) is further developed to account for the presence of a moving boundary in the streamfunction‐vorticity formulation using the finite‐difference method. A number of cases for different release positions of the particle are computed. It is demonstrated that bioconvection can either accelerate or decelerate settling of the particle depending on the initial position of the particle relative to the plume centre. It is also shown that the particle impacts bioconvection plume by changing its shape and location in the chamber. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
25.
Shu‐Ling Huang Wei‐Kuo Chin W. P. Yang 《Journal of Polymer Science.Polymer Physics》2004,42(18):3476-3486
The tetramethoxysilane (TMOS)/2‐hydroxylethyl methacrylate (HEMA) hybrid gels were synthesized with acid and base catalysts, via the in situ polymerization of HEMA, with and without the cosolvent methanol. With methanol in the TMOS/HEMA sol, the enhanced esterification and depolymerization reactions of the silanols resulted in a slower growth of silica particles. The silica particles that were synthesized with an acid catalyst were less than 40 nm. The thermal resistance of the poly(2‐hydroxyethyl methacrylate) (PHEMA) chains was enhanced by the addition of colloidal silica. The Fourier transform infrared characterizations and the exothermal peaks on the differential scanning calorimetry traces of these hybrid gels indicated chemical hybridization occurring as a result of condensation of the colloid silica and PHEMA at higher temperatures. Hence, the residual weight content of the hybrid gel after its synthesis with the base catalyst was even higher than the content of TMOS in the hybrid sol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3476–3486, 2004 相似文献
26.
K. Kubilius 《Acta Appl Math》2003,78(1-3):233-242
We consider the integral equation driven by a standard Brownian motion and by a fractional Brownian motion. Sufficient conditions under which the equation has a weak solution are obtained. 相似文献
27.
In-time motion adjustment in laser cladding manufacturing process for improving dimensional accuracy and surface finish of the formed part 总被引:2,自引:0,他引:2
This paper presents in-time motion adjustment in laser cladding manufacturing process as a means to improve dimensional accuracy and surface finish of the built part. Defects occurring during laser cladding degrade the part quality such as dimensional accuracy and surface finish. In this paper, in-time motion adjustment strategy was presented to remedy and eliminate defects occurring during laser cladding to improve the dimensional accuracy and surface finish. Based on the relationship between the motion of laser head relative to the growing part and other parameters in effects on clad profile, the laser traverse speed, stand-off distance and laser approach orientation to the existing clad layer were adjusted by instructions from a close-loop control system in real time to remedy and eliminate defects. The results of the experiments verified the effects of in-time motion adjustment on dimensional accuracy and surface finish. 相似文献
28.
29.
We investigate a new interpretation for the Navier-Stokes corrections to the hydrodynamic equation of asymmetric interacting particle systems. We consider a system that starts from a measure associated with a profile that is constant along the drift direction. We show that under diffusive scaling the macroscopic behavior of the process is described by a nonlinear parabolic equation whose diffusion coefficient coincides with the diffusion coefficient of the hydrodynamic equation of the symmetric version of the process. 相似文献
30.
Zhao Xuelei 《数学年刊B辑(英文版)》1997,18(1):47-54
GIRSANOV’STHEOREMONABSTRACTWIENERSPACESZHANGYINNANAbstractLet(E,H,μ)beanabstractWienerspaceinthesenseofL.Gros.Itisprovedth... 相似文献