全文获取类型
收费全文 | 3313篇 |
免费 | 811篇 |
国内免费 | 574篇 |
专业分类
化学 | 2006篇 |
晶体学 | 316篇 |
力学 | 124篇 |
综合类 | 11篇 |
数学 | 20篇 |
物理学 | 2221篇 |
出版年
2024年 | 4篇 |
2023年 | 34篇 |
2022年 | 70篇 |
2021年 | 87篇 |
2020年 | 117篇 |
2019年 | 112篇 |
2018年 | 91篇 |
2017年 | 149篇 |
2016年 | 163篇 |
2015年 | 138篇 |
2014年 | 197篇 |
2013年 | 238篇 |
2012年 | 242篇 |
2011年 | 398篇 |
2010年 | 294篇 |
2009年 | 329篇 |
2008年 | 257篇 |
2007年 | 299篇 |
2006年 | 262篇 |
2005年 | 214篇 |
2004年 | 174篇 |
2003年 | 151篇 |
2002年 | 108篇 |
2001年 | 92篇 |
2000年 | 81篇 |
1999年 | 73篇 |
1998年 | 54篇 |
1997年 | 50篇 |
1996年 | 46篇 |
1995年 | 25篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1975年 | 4篇 |
1973年 | 1篇 |
排序方式: 共有4698条查询结果,搜索用时 15 毫秒
971.
We report on how different cluster deposition regimes can be obtained and observed by in situ scanning tunneling microscopy by exploiting deposition parameters in a pulsed laser deposition process. Tungsten clusters were produced by nanosecond pulsed laser ablation in Ar atmosphere at different pressures and deposited on Au(1 1 1) and HOPG surfaces. Deposition regimes including cluster deposition-diffusion-aggregation, cluster melting and coalescence and cluster implantation were observed, depending on background gas pressure and target-to-substrate distance which influence the kinetic energy of the ablated species. These parameters can thus be easily employed for surface modification by cluster bombardment, deposition of supported clusters and growth of films with different morphologies. The variation in cluster mobility on different substrates and its influence on aggregation and growth mechanisms has also been investigated. 相似文献
972.
Alexander Winkler 《Surface science》2006,600(15):3036-3044
The activity of supported Ni catalysts can easily be affected by high temperatures and oxidative atmosphere. In order to study the origin of this behaviour, we performed systematic LEED and XPS investigations on a model system prepared by physical vapour deposition of Ni on a thin epitaxial alumina film on NiAl(1 1 0). Annealing experiments showed that deposited Ni is thermally stable up to ∼370 K. Further annealing seems to lead first to changes in the island structure and then, at temperatures above ∼480 K, to diffusion of Ni through the alumina film. Analysis of the complex oxidation behaviour revealed that there is a competition between oxidation of the Ni deposit and of the NiAl support. The latter process is probably enabled by a solid state reaction at the interface which means that Ni catalyses the further oxidation of the support. While the surface of the deposited Ni clusters is easily oxidised, the further oxidation processes of the Ni particles and the support were found to be diffusion-controlled. 相似文献
973.
The growth mechanisms and surface morphology of colossal magnetoresistance (CMR) La0.67Ca0.33MnO3 films deposited by rf magnetron sputtering on SrTiO3(0 0 1) substrates are investigated. The films are epitaxial, coherently strained and ferromagnetic. It is found that at early growth stages, in nanometric films, a layer-by-layer mechanism dominates, which results in step and terrace surface morphology. Upon further growth, the flat surface becomes unstable when large two-dimensional (2D) islands form. The Erlich-Schwoebel step-edge energy barrier induces an anisotropic adatom kinetics that favors 2D nucleation on top of the islands as it reduces downhill adatom current. As a result, there is an evolution with growth to mound-like structures of increasing height. Critical thickness for mound formation and average mound separation can be tuned by substrate miscut angle and growth temperature. These results provide a detailed understanding of the roughening process in manganites and are relevant for the controlled fabrication of CMR films, in particular for its use in epitaxial heterostructures. 相似文献
974.
电子回旋共振等离子分解CH19Si2N-N2混合气体,采用溅射共混、气相液相共混沉积技术,制备四元素SiCNB膜,由XPS分析了膜的成份及生成的键结构,发现溅射共混、气液共混沉积过程中聚合成了C-N、C-B、N-B、Si-C化合物。 相似文献
975.
Wax deposition from a waxy crude oil is modelled in turbulent flow in a pipeline. Molecular diffusion in a thin boundary layer
near the pipe wall is taken as the only mechanism responsible for deposition. The model takes into account the ablation, which
is a flow-related phenomenon that limits the growth of the deposit. The effect of desaturation of the oil is analyzed as well.
Two field cases are presented in which the numerical implementation of the model is in agreement with the experimental data.
Work performed in the framework of the cooperation between EniTecnologie (Milan) and I2T3 (Florence). 相似文献
976.
Weitian Wang Zhenhong Dai Yuming Sun Yuanping Sun Dongyi Guan 《Applied Surface Science》2005,250(1-4):268-272
Well-crystallized Ba0.5Sr0.5TiO3 thin films with good surface morphology were prepared on MgO(1 0 0) substrates by pulsed laser deposition technique at a deposition temperature of 800 °C under the oxygen pressure of 2 × 10−3 Pa. X-ray diffraction and atomic force microscopy were used to characterize the films. The full width at half maximum of the (0 0 2) Ba0.5Sr0.5TiO3 rocking curve and the root-mean-square surface roughness within the 5 μm × 5 μm area were 0.542° and 0.555 nm, respectively. The nonlinear optical properties of the films were determined by a single beam Z-scan method at a wavelength of 532 nm with laser duration of 55 ps. The results show that Ba0.5Sr0.5TiO3 thin films exhibit a fast third-order nonlinear optical response with the nonlinear refractive index and nonlinear absorption coefficient being n2 = 5.04 × 10−6 cm2/kW and β = 3.59 × 10−6 (m/W), respectively. 相似文献
977.
Deposition features of Ni on self-assembled microtubule template from biolipid by electroless method 总被引:1,自引:0,他引:1
FU Yubin ZHANG Lide ZHENG Jiyong FU Shangang & ZHU Mingwei . Institute of Solid State Physics Chinese Academy of Sciences Hefei China . Luoyang Ship Material Research Institute Luoyang China . College of Life Science Henan Normal University Xinxiang China 《中国科学B辑(英文版)》2004,47(3):228-234
The self-assembly of lipid molecules is in close relationship with the structure and function of a cell membrane. A cell membrane has a variety of lipid molecules. Lipid molecules have their amphiphile na-tures, and their self-assembly can form a variety of thermodynamically stable microstructures, such as single-bilayer or multi-bilayer spherical and ellipsoidal liposome, microcylindrical and microtubular struc-tures[1]. These microstructures exhibit different bio-logical functions in living … 相似文献
978.
Carbon Dioxide (CO2) laser-induced decomposition of ethoxy(trimethyl)germane (ETG) results in a substantial stripping of organic substituents from germanium and leads to deposition of organogermanium films, the composition of which is dependent on the mode of laser irradiation. Direct absorption of laser radiation in ETG affords material rich in Germanium, while a sulfur hexafluoride (SF6)-photosensitized process produces a deposit composed of Germanium, Carbon, Hydrogen and Oxygen. The deposited materials can be modified by chemical reactions with acetic anhydride and atmospheric moisture. 相似文献
979.
一、引言 射频离子源素有结构简单。维护运行方便,质子比高等优点;并且造价低,在大规模工业应用上与其他源型相比,具有优越的竞争能力。 目前,仅限于单孔引出,射频离子源最大引出质子流强,均在5mA以下,且没有开发这种离子源型的应用。我们研制的毫安级射频离子源,其特点是低能、大束斑。它除了应用 相似文献
980.
G.D.Chen 《Chinese Journal of Lasers》1998,7(1):41-45
ExcitationIntensityDependenceofFre┐excitonTransitionsinGaNGrownbyLow┐presureMetalorganicChemicalVaporDepositionG.D.Chen(Depar... 相似文献