全文获取类型
收费全文 | 169篇 |
免费 | 9篇 |
专业分类
化学 | 80篇 |
晶体学 | 2篇 |
力学 | 23篇 |
数学 | 42篇 |
物理学 | 31篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 13篇 |
2011年 | 10篇 |
2010年 | 9篇 |
2009年 | 14篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有178条查询结果,搜索用时 31 毫秒
61.
Michael D. SangidHans J. Maier Huseyin Sehitoglu 《International Journal of Plasticity》2011,27(5):801-821
In this paper, we construct a model for prediction of fatigue crack initiation based on the material’s microstructure. In order to do so, the energy of a persistent slip band (PSB) is monitored and an energy balance approach is taken, in which cracks initiate and the material fails due to stress concentration from a PSB (with respect to dislocation motion). These PSBs are able to traverse low-angle grain boundaries (GB), thus belonging to clusters of grains. As a consequence of the ongoing cyclic slip process, the PSBs evolve and interact with high-angle GBs, the result of which leads to dislocation pile-ups, static extrusions in the form of ledges/steps at the GB, stress concentration, and ultimately crack initiation. Hence, this fatigue model is driven by the microstructure, i.e. grain orientations, widely distributed grain sizes, precipitates, PSB-GB interactions, as well as the affect of neighboring grains. The results predict that cracks initiate near twin boundaries from PSBs spanning a single large grain with a favorable orientation or multiple grains connected by low-angle GBs. Excellent agreement is shown between model predictions and experimental data. 相似文献
62.
Huseyin Onur Mete Yanfang Shen Zelda B. Zabinsky Seksan Kiatsupaibul Robert L. Smith 《Journal of Global Optimization》2011,50(4):597-627
We develop new Markov chain Monte Carlo samplers for neighborhood generation in global optimization algorithms based on Hit-and-Run.
The success of Hit-and-Run as a sampler on continuous domains motivated Discrete Hit-and-Run with random biwalk for discrete
domains. However, the potential for efficiencies in the implementation, which requires a randomization at each move to create
the biwalk, lead us to a different approach that uses fixed patterns in generating the biwalks. We define Sphere and Box Biwalks that are pattern-based and easily implemented for discrete and
mixed continuous/discrete domains. The pattern-based Hit-and-Run Markov chains preserve the convergence properties of Hit-and-Run
to a target distribution. They also converge to continuous Hit-and-Run as the mesh of the discretized variables becomes finer,
approaching a continuum. Moreover, we provide bounds on the finite time performance for the discrete cases of Sphere and Box
Biwalks. We embed our samplers in an Improving Hit-and-Run global optimization algorithm and test their performance on a number
of global optimization test problems. 相似文献
63.
Sibel Kasap Huseyin Tel Sabriye Piskin 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):537-544
A spherical polyacrylonitrile–TiO2 composite adsorbent was prepared and its strontium removal potential was investigated. The Langmuir equation fixed well the
equilibrium data. The value of ∆H° = 8.943 kJ/mol and ∆G° = 6.291 kJ/mol at 298 K indicate that the adsorption of strontium onto TiO2/PAN composite adsorbent is an endothermic and non-spontaneous reaction. The kinetic process was described by a pseudo-second-order
rate model very well. 相似文献
64.
Sibel Kasap Huseyin Tel Sabriye Piskin 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):489-495
The objective of this study is to evaluate the use of titanium dioxide nanoparticles which were prepared by novel sonochemical
method as an ion exchange material for the removal of Sr from aqueous solution. The pH effect on the Sr2+ sorption was investigated. The data obtained have been correlated with Freundlich, Temkin and Dubinin–Radushkevich (D–R)
isotherm models. Thermodynamic parameters fort he sorption system have been determined at four temperatures. Simple kinetic
models have been applied to the rate and isotherm sorption data and the relevant kinetic parameters were determined from the
graphical presentation of these models at 298°K. Results explained that the pseudo second-order sorption mechanism is predominant
and the overall rate constant of sorption process appears to be controlled by chemical sorption process. The value of sorption
energy E = 13 kJ/mol at 298°K and the value of Gibbs free energy ∆G° = 3,222 kJ/mol at 298°K prove that the sorption of strontium on titanium dioxide nanoparticles is an endothermic and non-spontaneous
process. 相似文献
65.
Huseyin Halilov 《Applicable analysis》2013,92(1-2):61-71
In this paper the multidimensional mixed problem for the quasilinear pseudoparabolic equation ut-Lxu-εLxut=f(t,x,u) is considered. Lx is a differential operator, which composes (with boundary operator) a self adjoint operator. An existence, uniqueness and also continuous dependense on the small parameter ε>0 of generalized solution is proved. The estimation of the difference of exact and approximate solutions is obtained 相似文献
66.
The Painlevé equations arise as reductions of the soliton equations such as the Korteweg–de Vries equation, the nonlinear Schrödinger equation and so on. In this study, we are concerned with numerical approximation of the asymptotics of solutions of the second Painlevé equation on pole‐free intervals along the real axis. Classical integrators such as high order Runge–Kutta schemes might be expensive to simulate oscillation, decay and blow‐up behaviours depending on initial conditions. However, a lower order functional fitting method catches all kinds of solutions even for relatively large step sizes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
67.
We report a narrow-linewidth, tunable, gain-switched Cr:ZnSe laser operating between 2255 and 2455 nm. The spectral width of the laser was reduced from 125 nm to 0.3 nm by using injection seeding. Seeding was achieved with a second tunable CW Cr:ZnSe laser. The output wavelength was varied by tuning the wavelength of the seed laser. The seeded oscillator produced as high as 157 μJ pulses with 598 μJ incident pump pulse energy at a repetition rate of 1 kHz. The slope efficiency was determined to be 26%. 相似文献
68.
The change in flow characteristics downstream of a circular cylinder (inner cylinder) surrounded by an outer permeable cylinder was investigated in shallow water using particle image velocimetry technique. The diameter of the inner cylinder and the water height were kept constant during the experiments as d?=?50?mm and h w ?=?25?mm, respectively. The depth-averaged free-stream velocity was also kept constant as U?=?170?mm/s which corresponded to a Reynolds number of Red?=?8,500 based on the inner cylinder diameter. In order to examine the effect of diameter and porosity of the outer cylinder on flow characteristics of the inner cylinder, five different outer cylinder diameters (D?=?60, 70, 80, 90 and 100?mm) and four different porosities (???=?0.4, 0.5, 0.6 and 0.7) were used. It was shown that both porosity and outer cylinder diameter had a substantial effect on the flow characteristics downstream of the circular cylinder. Turbulent statistics clearly demonstrated that in comparison with the bare cylinder (natural case), turbulent kinetic energy and Reynolds stresses decreased remarkably when an outer cylinder was placed around the inner cylinder. Thereby, the interaction of shear layers of the inner cylinder has been successfully prevented by the presence of outer cylinder. It was suggested by referring to the results that the outer cylinder having 1.6????D/d????2.0 and 0.4????D/d????0.6 should be preferred to have a better flow control in the near wake since the peak magnitude of turbulent kinetic energy was considerably low in comparison with the natural case and it was nearly constant for these mentioned porosities ??, and outer cylinder to inner cylinder diameter ratios D/d. 相似文献
69.
Gyaneshwar P. Srivastava Huseyin M. T??t??nc?? 《Central European Journal of Physics》2009,7(2):209-219
We present a mini review of progress made towards theoretical modelling of surface phonons. We outline the essential ingredients
of two theoretical methods, viz. an adiabatic bond charge method for semiconductor surfaces and the ab-initio density-functional perturbation method for solid surfaces in general. From the results of theoretical calculations we establish
trends and criteria for the existence of localized phonon modes on group-IV(001) and III-V(110) semiconductor surfaces. We
further obtain signatures of characteristic vibrational modes which develop during dissociative molecular adsorption on Si(001)
surfaces. The results are compared with available experimental measurements. Some remarks are forwarded regarding manipulation
of surface phonon modes for scientific advances and technological applications.
相似文献
70.
Flow behaviors around permeable cylinders were investigated using Particle Image Velocimetry technique in deep water. The height of deep water and free stream velocity were kept constant as hw = 340 mm and U = 156 mm/s. To find out the effect of the permeable cylinders on the flow structure, eight different porosities (β = 0.4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85) were used. The results have indicated that the permeable cylinders are effective on the control of large-scale vortical structures downstream of the permeable cylinder. As the porosity increases, turbulent kinetic energy and Reynolds shear stress decrease. This means that the fluctuations in the wake region are significantly weakened by permeable cylinders. The permeable cylinders having the porosity higher than 0.6 do not pose an obstacle in the flow. Furthermore, for all diameter values of permeable cylinders, it can be concluded that the flow structures downstream of the permeable cylinder show similar trend with each other. 相似文献