全文获取类型
收费全文 | 774篇 |
免费 | 36篇 |
国内免费 | 29篇 |
专业分类
化学 | 40篇 |
晶体学 | 2篇 |
力学 | 457篇 |
数学 | 102篇 |
物理学 | 238篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 42篇 |
2012年 | 15篇 |
2011年 | 37篇 |
2010年 | 13篇 |
2009年 | 73篇 |
2008年 | 43篇 |
2007年 | 60篇 |
2006年 | 43篇 |
2005年 | 32篇 |
2004年 | 19篇 |
2003年 | 48篇 |
2002年 | 26篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 25篇 |
1998年 | 27篇 |
1997年 | 24篇 |
1996年 | 28篇 |
1995年 | 18篇 |
1994年 | 20篇 |
1993年 | 8篇 |
1992年 | 18篇 |
1991年 | 26篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有839条查询结果,搜索用时 187 毫秒
91.
A device has been produced which can detect the contamination of the test gas by the driver gas in a reflected shock tunnel. This device monitors the static pressure in a converging duct. The duct is designed to choke at a predetermined contamination level due to the change in the specific heat ratio produced by the contaminants. Experimental results are given for a freestream enthalpy of nominally 6 MJ/kg. 相似文献
92.
Single shot spatially and spectrally resolved laser induced predissociation fluorescence measurements in a shock layer around a cylinder in a pulsed supersonic free stream are presented. Fluoresence signals were produced using the tuned output of an argon fluoride excimer laser to excite a mixture of rovibrational transitions in molecular oxygen. The signals produced along a line inside the shock layer were focussed onto a two dimensional detector coupled to a spectrometer, thus allowing spectral and spatial resolution of the fluoresence. In this way, it was possible to detect two fluoresence signals from two different transitions simultaneously, allowing the determination of vibrational temperatures without the need for calibration. To minimize problems associated with low signal to noise ratios, background subtraction and spatial averaging was required.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
93.
Bend manholes of sewers with 45° deflection angles are considered. Previous results are reconsidered by introducing the so-called
bend extension. It is demonstrated that the discharge capacity of the 45°- and the 90°-bend manholes is identical if the bend
extension, a U-shaped straight downstream portion, is added to the 45° manhole. In addition, the effect of the bend cover
is analyzed as a general means to suppress shock waves. Both bend extensions and bend covers may be added to existing structures
that convey discharge close to or over the design discharge. The hydraulics of bend manholes are analyzed in detail, including
the wave profiles along the inner and the outer bend walls, the complete free surface, the recirculation zone, the pressure
distributions on the walls and flow in the downstream sewer.
Received: 12 March 2001 / Accepted: 10 August 2001 相似文献
94.
A method is outlined for solving two-dimensional transonic viscous flow problems, in which the velocity vector is split into the gradient of a potential and a rotational component. The approach takes advantage of the fact that for high-Reynolds-number flows the viscous terms of the Navier-Stokes equations are important only in a thin shear layer and therefore solution of the full equations may not be needed everywhere. Most of the flow can be considered inviscid and, neglecting the entropy and vorticity effects, a potential model is a good approximation in the flow core. The rotational part of the flow can then be calculated by solution of the potential, streamfunction and vorticity transport equations. Implementation of the no-slip and no-penetration boundary conditions at the walls provides a simple mechanism for the interaction between the viscous and inviscid solutions and no extra coupling procedures are needed. Results are presented for turbulent transonic internal choked flows. 相似文献
95.
Viscous profiles of shock waves in systems of conservation laws can be viewed as heteroclinic orbits in associated systems of ordinary differential equations (ODE). In the case of overcompressive shock waves, these orbits occur in multi-parameter families. We propose a numerical method to compute families of heteroclinic orbits in general systems of ODE. The key point is a special parameterization of the heteroclinic manifold which can be understood as a generalized phase condition; in the case of shock profiles, this phase condition has a natural interpretation regarding their stability. We prove that our method converges and present numerical results for several systems of conservation laws. These examples include traveling waves for the Navier-Stokes equations for compressible viscous, heat-conductive fluids and for the magnetohydrodynamics equations for viscous, heat-conductive, electrically resistive fluids that correspond to shock wave solutions of the associated ideal models, i.e., the Euler, resp. Lundquist, equations.
96.
莫嘉琪 《数学物理学报(A辑)》2003,23(5):530-534
该文是利用匹配条件讨论一类非线性方程激波解。得出了对应的激波解与边界条件的关系。 相似文献
97.
The problem of attenuating the noise from weapons firing is studied experimentally and numerically. As a possible method of attenuating the noise significantly, a silencer with no internal baffles is attached to the M242 cannon. The internal pressures inside the muffler are measured. The near-field overpressures outside the muffler at various polar angles are also measured. A numerical simulation of the flow through the muffler is performed, using Harten's shock-capturing method to solve the Euler equations of ideal compressible flow. The numerical simulation yields a detailed picture of the flow field as displayed by the pressure and Mach contours. Pressure–time curves at selected locations are obtained and compared with experimental data. There is good agreement, except that the numerical simulation generates more vigorous oscillations. 相似文献
98.
Rajiv R. Thareja James R. Stewart Obey Hassan Ken Morgan Jaime Peraire 《国际流体数值方法杂志》1989,9(4):405-425
An upwind finite element technique that uses cell-centred quantities and implicit and/or explicit time marching has been developed for computing hypersonic laminar viscous flows using adaptive triangular grids. The approach is an extension to unstructured grids of the LAURA algorithm due to Gnoffo. A structured grid of quadrilaterals is laid out near a solid surface. For inviscid flows the method is stable at Courant numbers of over 100000. A first-order basic scheme and a higher-order flux-corrected transport (FCT) scheme have been implemented. This technique has been applied to the problem of predicting type III and IV shock wave interactions on a cylinder, with a view to simulating the pressure and heating rate augmentation caused by an impinging shock on the leading edge of a cowl lip of an engine inlet. The predictions of wall pressure and heating rates compare very well with experimental data. The flow features are distinctly captured with a sequence of adaptively generated grids. 相似文献
99.
O. K. Sommersel D. Bjerketvedt S. O. Christensen O. Krest K. Vaagsaether 《Shock Waves》2008,18(4):291-297
This paper describes application of a background oriented schlieren technique in order to obtain quantitative measurements
of shock waves from explosions by processing high speed digital video recordings. The technique is illustrated by an analysis
of two explosions, a high explosive test and a hydrogen gas explosion test. The visualization of the shock front is utilized
to calculate the shock Mach number, leading to a predicted shock front pressure. For high explosives the method agreed quite
well with a standard curve for side-on shock pressures. In the case of the gas explosion test we can also show that the shock
front is non-spherical. It should be possible to develop this technique to investigate external blast waves and external explosions
from vented gas explosions in more details.
This paper is based on work that was presented at the 21th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Poitiers, France, July 23–27, 2007. 相似文献
100.
Transient shock waves in a confined elliptical chamber are experimentally investigated. Quantitative results of the pressure
distribution are obtained for an air-filled cavity. Lower bounding surfaces of different geometrical shapes can be inserted
making it possible to get chambers with varying height. An electrical discharge across a pair of electrodes inside the cavity
gives rise to the shock waves. Double pulsed holographic interferometry is used to study the propagation and focusing process
of the waves. The results are quantitatively evaluated by using the method of two-reference-beam holography. The angular pressure
distribution behind the converging wave front is presented for different geometries of an air-filled cavity. The pressure
distribution is non-homogeneous but symmetric along the wave front. The pressure level is higher for the geometry where the
height of the chamber decreases with the radial distance from the outgoing focus and lower for increasing height of the chamber.
In addition, shock waves in a water-filled cavity are studied. In this case qualitative results are obtained.
Received 3 November 1996 / Accepted 5 January 1997 相似文献