全文获取类型
收费全文 | 444篇 |
免费 | 12篇 |
国内免费 | 18篇 |
专业分类
化学 | 77篇 |
晶体学 | 7篇 |
力学 | 138篇 |
数学 | 31篇 |
物理学 | 221篇 |
出版年
2023年 | 15篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 16篇 |
2014年 | 28篇 |
2013年 | 35篇 |
2012年 | 20篇 |
2011年 | 32篇 |
2010年 | 26篇 |
2009年 | 35篇 |
2008年 | 33篇 |
2007年 | 27篇 |
2006年 | 34篇 |
2005年 | 16篇 |
2004年 | 12篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有474条查询结果,搜索用时 15 毫秒
391.
392.
Polarized UV-visible absorption spectroscopy was used to investigate the inplane orientation of the hemicyanine molecules in Y-type Langmuir-Blodgett(LB) multilayers. We demonstrated for the first time that the dipping-induced molecular alignment was enhanced significantly with increasing the layer number due to the interlayer interactions. Polarized UV nanosecond pulses were used to control the photoinduced reorientation of the hemicyanine molecules. Thermal-isotropic process was accompaniedd by dissocition of the H-aggregate in hemicyanine LB multilayers. 相似文献
393.
K.R. Mangipudi 《Journal of the mechanics and physics of solids》2011,59(7):1437-1461
The fracture strength of metal foams depends sensitively on the properties of the constituent material as well as the cellular architecture. A change in microscopic properties carries over to the macroscopic scale through an alteration of the mesoscopic damage and fracture mechanisms. In this paper we study these dependencies using a modelling framework that takes all these ingredients into account. We have developed a micromechanical model based on a discrete Voronoi representation of cellular metals that incorporates power-law strain hardening and damage development of the cell wall material. The influence of the relative density and material strain hardening on the cell wall damage behavior and overall fracture response is analyzed in detail. The effect of the cellular architecture is studied by varying the cell shape anisotropy and structural randomness. We also simulate the effect of post-processing heat treatments on the solid material plastic and fracture properties and how this affects the overall fracture profile and damage development. Finally, all material and architectural effects are summarized in a strength versus ductility graph, identifying trends for improved design of metallic foams. 相似文献
394.
Sheet metal forming processes generally involve non-proportional strain paths including springback, leading to the Bauschinger effect, transient hardening, and permanent softening behavior, that can be possibly modeled by kinematic hardening laws. In this work, a stress integration procedure based on the backward-Euler method was newly derived for a nonlinear combined isotropic/kinematic hardening model based on the two-yield’s surfaces approach. The backward-Euler method can be combined with general non-quadratic anisotropic yield functions and thus it can predict accurately the behavior of aluminum alloy sheets for sheet metal forming processes. In order to characterize the material coefficients, including the Bauschinger ratio for the kinematic hardening model, one element tension–compression simulations were newly tried based on a polycrystal plasticity approach, which compensates extensive tension and compression experiments. The developed model was applied for a springback prediction of the NUMISHEET’93 2D draw bend benchmark example. 相似文献
395.
Nikolas M. Eleftheriou John D. Brennan 《Journal of Sol-Gel Science and Technology》2009,50(2):184-193
Previous studies from our lab reported on the use of time-resolved fluorescence anisotropy (TRFA) to probe the dynamics of
domains I and II within the model protein, human serum albumin (HSA), in solution and when entrapped into sol–gel derived
silica. In order to further our understanding of the dynamics within this multi-domain protein, TRFA was used to measure the
dynamics of domain III of the protein. For this purpose, the fluorescence ligand dansylsarcosine (DS), which has a 400-fold
higher emission intensity in the bound state relative to the free state and an emission lifetime of >22 ns when bound to Sudlow’s
site II (domain III) in HSA, was selected. This probe is able to accurately report on slow rotational motions (up to 300 ns
correlation time) and the bound form of the probe can be selectively measured at 475 nm, ensuring that the dynamics reflect
only the properly folded form of the protein. The mobility of HSA with bound dansylsarcosine (HSA–DS) was evaluated in solution
and after entrapment in sol–gel derived silica prepared from sodium silicate under varying ionic strength and pH conditions.
The results here show that (1) the 43 ns global rotational correlation time of HSA in buffered solution can be accurately
measured via labeling with DS with no interference from faster local or segmental motions; (2) the global motion of HSA in
silica is greatly hindered immediately after encapsulation, with no correlation time faster than 300 ns discernable, indicative
of strong templating of the silica around domain III of the native protein; and (3) the addition of salt and variation of
pH have essentially no effect on HSA mobility, ruling out electrostatics as the primary interaction restricting HSA motion.
The results from this study are compared to past studies using intrinsic tryptophan fluorescence (domain II) or fluorescein-labeled
HSA (domain I), and demonstrate that motion observed using such probes likely reflects differential mobility of the three
domains, consistent with domain III of HSA adsorbing to or templating with silica upon entrapment while the other domains
protrude into the pore. Restricted motion of domain III of HSA was also observed in silica materials derived from diglycerylsilane
or tetraethylorthosilicate, showing that templating is not dependent on the silica precursor or processing conditions. 相似文献
396.
N.A. Morley M.R.J. Gibbs E Ahmad I Will Y.B. Xu 《Journal of magnetism and magnetic materials》2006,300(2):436-444
This paper presents a quantitative method used to determine the magnetocrystalline anisotropy constants of thin magnetic films from normalized magnetization data measured on a magneto-optic Kerr effect (MOKE) magnetometer. The method is based on a total magnetic energy density model, and incorporates higher order effects in the detected signal. By way of illustration, the method is used to determine the magnetocrystalline anisotropy constants of epitaxial thin Fe films on GaAs substrates, which have different overlayers. It is shown that a Cr overlayer on a 30 ML thick Fe film reduces the uniaxial contribution to the magnetic anisotropy compared with an Au overlayer. 相似文献
397.
Turbulence modelling is a crucial question in the application of CFD to flows over buildings. The impinging flow and anisotropic nature of the turbulence present severe challenges. This paper presents a comparison of CFD against full-scale results. It differs from previous work which has concentrated on the wind-tunnel scale. In order to better account for the production of turbulent kinetic energy and the anisotropic nature of the turbulence a non-linear k– model is implemented. The results are discussed for different turbulence models and for the comparison of computed results with the measurements from full-scale. 相似文献
398.
B. Beschoten J. Keller P. Miltnyi G. Güntherodt 《Journal of magnetism and magnetic materials》2002,240(1-3):248-250
The thickness dependence of different diluted antiferromagnetic Co1−yO layers on the exchange bias (EB) in ferro/antiferromagnetic Co/Co1−yO bilayers is investigated. For undiluted samples the EB decreases above a layer thickness of 5 nm whereas it increases and saturates for AFM layers thicker than 20 nm for diluted samples. These findings support the domain state model for EB. 相似文献
399.
Recent experiments and models on giant magnetoimpedance 总被引:1,自引:0,他引:1
An overview of the giant magnetoimpedance phenomenon is given in this work. The effect, that consists of drastic changes of the complex impedance of soft magnetic materials upon the application of an external magnetic field, has attracted attention owing to the increasing perspectives of applications on magnetic and stress sensor technology. In particular, asymmetric response is specially indicated for specific applications, and many experimental and theoretical results have been developed so far. A novel approach to investigate the GMI, based on the Fourier analysis of the time derivative of magnetization, will be discussed in further detail. 相似文献
400.
A theoretical study of the magnetic properties of the CoPt and FePt ordered alloys has been performed. The calculation is done as a function of the spin-quantization axis by means of both the local spin density and the generalized-gradient approximations in conjunction with the full-potential linear muffin–tin orbital method. Both approximations produced similar results for the FePt and CoPt compounds. The band structure and the total density of states have been calculated and it was confirmed that all electronic states contribute to the magneto-crystalline anisotropy energy; the magnetization axis is along the [0 0 1] direction. The Fe and Co orbital magnetic moments decrease with respect to the angle γ between the [0 0 1] axis and the spin quantization axis, but for the [1 0 0] axis the orbital moment is comparable to the [0 0 1] moment. The Pt orbital moments are of the same order of magnitude as those of Fe and Co moments due to the large spin–orbit splitting parameter of Pt and show a similar behavior with the angle γ. 相似文献