全文获取类型
收费全文 | 450篇 |
免费 | 10篇 |
国内免费 | 10篇 |
专业分类
化学 | 136篇 |
晶体学 | 2篇 |
力学 | 110篇 |
综合类 | 2篇 |
数学 | 26篇 |
物理学 | 194篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 14篇 |
2013年 | 22篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 28篇 |
2008年 | 30篇 |
2007年 | 36篇 |
2006年 | 29篇 |
2005年 | 19篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 22篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1998年 | 16篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有470条查询结果,搜索用时 15 毫秒
241.
General analytical solutions are obtained for the planar orientation structure of rigid ellipsoid of revolutions subjected to an arbitrary homogeneous flow in a Newtonian fluid. Both finite and infinite aspect ratio particles are considered. The orientation structure is described in terms of two-dimensional, time-dependent tensors that are commonly employed in constitutive equations for anisotropic fluids such as fiber suspensions. The effect of particle aspect ratio on the evolution of orientation structure is studied in simple shear and planar elongational flows. With the availability of analytical solutions, accuracies of quadratic closure approximations used for nonhomogeneous flows are analyzed, avoiding numerical integration of orientation distribution function. In general, fourth-order orientation evolution equations with sixth-order quadratic closure approximations yield more accurate representations compared to the commonly used second-order evolution equations with fourth-order quadratic closure approximations. However, quadratic closure approximations of any order are found to give correct maximum orientation angle (i.e., preferred direction) results for all particle aspect ratios and flow cases. 相似文献
242.
243.
Hierarchical modeling in multibody dynamics 总被引:1,自引:0,他引:1
Summary In this paper a hierarchical approach using several mechanical models with different complexities and modeling depths to
describe a single engineering system is presented. The mechanical models are derived from (but not limited to) multibody dynamics. The computer
power available and improvements in theoretical understanding allow today not only to perform analyses but also to attack
the problem of multimodel synthesis. Therefore, hierarchical modeling is used as a basis to analyze simultaneously models
with different complexities and different excitations, and to optimize the performance with the most appropriate model for
an investigated mechanical effect.
Since only one single engineering system is investigated, its different models must be coupled by shared parameters, and the
different criteria have to be combined with multicriteria optimization algorithms in order to obtain a single feasible design.
An example taken from vehicle dynamics demonstrates the application of the approach.
Received 14 January 1997; accepted for publication 11 September 1997 相似文献
244.
M.F. El-Sayed 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):391-403
A linear analysis of the combined effect of viscosity, finite ion Larmor radius and suspended particles on Kelvin-Helmholtz
instability of two superposed incompressible fluids in the presence of a uniform magnetic field is carried out. The magnetic
field is assumed to be transverse to the direction of streaming. A general dispersion relation for such a configuration has
been obtained using appropriate boundary conditions. The stability analysis is discussed analytically, and the obtained results
are numerically confirmed. Some special cases are recovered and corrected. The limiting cases of absence of suspended particles
(or fluid velocities) and finite Larmor radius, absence of suspended particles are discussed in detail. In both cases, all
other physical parameters are found to have stabilizing as well as destabilizing effects on the considered system. In the
former case, the kinematic viscosity is found to has a stabilizing effect, while in the later case, the finite Larmor radius
is found to has a stabilizing influence for a vortex sheet. It is shown also that both finite Larmor radius and kinematic
viscosity stabilizations for interchange perturbations are similar to the stabilization effect due to a magnetic field for
non-interchange perturbations.
Received 13 January 2003 Published online 24 April 2003
RID="a"
ID="a"Also at: Department of Mathematics, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt. e-mail: m.elsayed@uaeu.ac.ae 相似文献
245.
Manipulation of particles using dielectrophoresis 总被引:2,自引:0,他引:2
A numerical scheme based on the distributed Lagrange multiplier method (DLM) is used to study the motion of particles of electrorheological suspensions subjected to non-uniform electric fields. At small Reynolds number, the time taken by the particles to collect at the minimums or maximums of the electric field is primarily determined by a parameter defined to be the ratio of the dielectrophoretic and viscous forces. Simulations show that in non-uniform electric fields the collection time is also influenced by a parameter defined by the ratio of the electrostatic particle–particle interaction and dielectrophoretic forces. The collection time decreases as this parameter decreases because when this parameter is less than one, particles move to the regions of high or low electric field regions individually. However, when this parameter is greater than one, particles regroup into chains which then move toward the electric field maximums or minimums without breaking. It is also shown that when the real part of the Clausius–Mosotti factor (β) is negative the positions of the local minimums of the electric field, and thus also the locations where particles collect, can be modified by changing the electric potential boundary conditions. 相似文献
246.
Hua-Shu Dou Boo Cheong Khoo Nhan Phan-Thien Khoon Seng Yeo Rong Zheng 《Rheologica Acta》2007,46(4):427-447
The simulation of fibre orientation in dilute suspension with front moving is carried out using the projection and level-set
methods. The motion of fibres is described using the Jeffery equation, and the contribution of fibres to the flow is accounted
for by the configuration-field method. The dilute suspension of short fibres in Newtonian fluids is considered. The governing
Navier–Stokes equation for the fluid flow is solved using the projection method with finite difference scheme, while the fibre-related
equations are directly solved with the Runge–Kutta method. In the present study for fibres in dilute suspension flow for injection
molding, the effects of various flow and material parameters on the fibre orientation, the velocity distributions and the
shapes of the leading flow front are found and discussed. Our findings indicate that the presence of fibre motion has little
influence on the front shape in the ranges of fibre parameters studied at the fixed Reynolds number. Influence of changing
fibre parameters only causes variation of front shape in the region near the wall, and the front shape in the central core
area does not vary much with the fibre parameters. On the other hand, the fibre motion has strong influence on the distributions
of the streamwise and transverse velocities in the fountain flow. Fibre motion produces strong normal stress near the wall
which leads to the reduction of transversal velocity as compared to the Newtonian flow without fibres, which in turn, leads
to the increased streamwise velocity near the wall. Thus, the fibre addition to the flow weakens the strength of the fountain
flow. The Reynolds number has also displayed significant influence on the distribution of the streamwise velocity behind the
flow front for a given fibre concentration. It is also found that the fibre orientation is not always along the direction
of the velocity vector in the process of mold filling. In the region of the fountain flow, the fibre near the centreline is
more oriented across the streamwise direction compared to that in the region far behind the flow front. This leads to the
fact that the fibre near the centreline in the region of fountain flow is more extended along the transverse direction. As
the fibre orientation in the suspension flow and the shape of the flow front have great bearing on the quality of the product
made from injection molding, this study has much implications for engineering applications. These results can also be useful
in other fields dealing with fibre suspensions. 相似文献
247.
248.
In this paper we investigate the stability of some viscometric flows for a concentrated suspension model which allows for the effects of shear-induced migration, including plane and circular Couette and Poiseulle flows, and unbounded and bounded torsional flows. In the bounded torsional flow, where its radial outer boundary is assumed frictionless, an exact closeform solution is given. With the exception of torsional flows, we find that a limit point for all the steady-state solutions can exist for certain range in the parameter values. In all cases, disturbances can persist for a long time, O (H
2/a
2), where H is a dimension of the flow field, and a is the particles' radius. 相似文献
249.
悬浮颗粒运动的格子Boltzmann数值模拟 总被引:7,自引:0,他引:7
将固体颗粒的牛顿力学和格子Boltzmann方法相结合,研究不规则形状悬浮颗粒在流场中的运动。通过受力分析,精确求得其所受合力、合力矩、合力作用中心等。提出了跟随颗粒运动的动网格计算域技术和模拟悬浮颗粒转动运动的局部数组方法及Euler-Lagrange两套坐标技术。通过对椭圆颗粒运动的数值模拟和对照他人对矩形颗粒的研究,分析了其复杂运动规律,并提供了合理的物理解释。结果表明:运用格子Boltzmann方法和上述特殊技术可以得到与有限元方法相同的模拟精度,且具有计算速度快、对复杂形状边界处理方便灵活、程序简单及特别适合大规模并行计算等优点。 相似文献
250.
The shear rheological properties of suspensions of gelled agar fibres in a low viscosity Newtonian matrix fluid were investigated.
Two classes of fibres, low aspect ratio fibres and high aspect ratio fibres with an aspect ratio of the order of 10 and 100
respectively were included in the investigations. For all fibre phase volumes investigated, from as low as 0.01 upwards, the
flow curves are characterised by an apparent yield stress followed by shear-thinning which was independent of the fibre aspect
ratio. Based on our analysis of the flow curves, we conclude that the high aspect ratio fibres behave like flexible threads
in contrast to the low aspect ratio fibres whose high shear relative viscosity is successfully described by a relation for
long rigid rods. These findings are supported by flow visualisation using an optical shearing stage coupled to a light microscope. 相似文献