全文获取类型
收费全文 | 1412篇 |
免费 | 78篇 |
国内免费 | 65篇 |
专业分类
化学 | 523篇 |
晶体学 | 2篇 |
力学 | 369篇 |
综合类 | 2篇 |
数学 | 237篇 |
物理学 | 422篇 |
出版年
2023年 | 13篇 |
2022年 | 25篇 |
2021年 | 27篇 |
2020年 | 26篇 |
2019年 | 21篇 |
2018年 | 21篇 |
2017年 | 24篇 |
2016年 | 37篇 |
2015年 | 29篇 |
2014年 | 35篇 |
2013年 | 97篇 |
2012年 | 93篇 |
2011年 | 61篇 |
2010年 | 50篇 |
2009年 | 93篇 |
2008年 | 97篇 |
2007年 | 89篇 |
2006年 | 79篇 |
2005年 | 77篇 |
2004年 | 74篇 |
2003年 | 51篇 |
2002年 | 44篇 |
2001年 | 57篇 |
2000年 | 48篇 |
1999年 | 29篇 |
1998年 | 29篇 |
1997年 | 33篇 |
1996年 | 24篇 |
1995年 | 20篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 15篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有1555条查询结果,搜索用时 19 毫秒
11.
New concepts for the study of incompressible plane or axisymmetric flows are analysed by the stream tube method. Flows without eddies and pure vortex flows are considered in a transformed domain where the mapped streamlines are rectilinear or circular. The transformation between the physical domain and the computational domain is an unknown of the problem. In order to solve the non-linear set of relevant equations, we present a new algorithm based on a trust region technique which is effective for non-convex optimization problems. Experimental results show that the new algorithm is more robust compared to the Newton-Raphson method. 相似文献
12.
The addition of the additives to the lubricant oil to enhance the characteristics of the lubricant will influence the performance of the bearings. Based on the theory of micropolar fluids, the tribological characteristics of a dynamically-loaded journal bearing are numerically studied. Comparisons are made between the Newtonian fluids and the micropolar fluids. It is shown that for a dynamically-loaded journal bearing, the micropolar fluids yield an increase not only in the friction force, but also in the friction coefficient. In addition, the oil film pressure and the oil film thickness are obviously higher than that of Newtonian fluids. 相似文献
13.
A. A. Shutov 《Fluid Dynamics》2008,43(4):533-546
Weakly conducting fluid flows in an electric field in the presence of phase interfaces are investigated theoretically and experimentally. The object of the investigation is an axisymmetric jet. The analysis is carried out within the framework of electrohydrodynamics (EHD) with allowance for surface charge transfer on mobile interfaces. The jet shape is calculated at large distances from the outflow point. The theoretical and experimental data are compared for Newtonian and polymeric fluids. 相似文献
14.
Nadir Arada Paulo Correia Adélia Sequeira 《Numerical Methods for Partial Differential Equations》2007,23(6):1468-1500
This article is concerned with the equations governing the steady motion of a viscoelastic incompressible second‐order fluid in a bounded domain. A new proof of existence and uniqueness of strong solutions is given. In addition, using appropriate finite element methods to approximate a coupled equivalent problem, sharp error estimates are obtained using a fixed point argument. The method is applied to the two‐dimensional lid‐driven cavity problem, at low Reynolds number and in a certain range of values of the viscoelastic parameters, to analyze the combined effects of inertia and viscoelasticity on the flow. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
15.
16.
A study of body waves in fractured porous media saturated by two fluids is presented. We show the existence of four compressional and one rotational waves. The first and third compressional waves are analogous to the fast and slow compressional waves in Biot's theory. The second compressional wave arises because of fractures, whereas the fourth compressional wave is associated with the pressure difference between the fluid phases in the porous blocks. The effects of fractures on the phase velocity and attenuation coefficient of body waves are numerically investigated for a fractured sandstone saturated by air and water phases. All compressional waves except the first compressional wave are diffusive-type waves, i.e., highly attenuated and do not exist at low frequencies.Now at Izmir Institute of Technology, Faculty of Engineering, Gaziosmanpasa Bulvari, No.16, Cankaya, Izmir, Turkey. 相似文献
17.
G. J. Dear D. N. Mallett D. M. Higton A. D. Roberts S. A. Bird H. Young R. S. Plumb I. M. Ismail 《Chromatographia》2002,55(3-4):177-184
Summary In this paper we investigate the potential of alkyl-bonded silica monolithic columns for the isolation and identification
of drug-related components in biological fluids. Up to 6 columns have been connected in series to produce a chromatographic
system with up to 40,000 plates. This high-resolution chromatography system has been coupled to both MS and NMR to enable
efficient detection and characterisation of drug-related components in biological fluids. The use of six coupled columns has
been shown to give enhanced resolution over a high quality silica particulate column packed with 3 μm material which exhibits
the same back pressure. The effect of volume and mass load on the performance of monolithic columns for semi-preparative chromatography
of biological fluids has also been investigated. In these studies it was possible to inject up to 100 mL of neat urine with
no loss of chromatographic performance. Furthermore, upon re-testing, the columns showed similar chromatographic performance.
Again several columns were serially connected, producing enhanced resolution in the semi-preparative mode. 相似文献
18.
J. Popplewell A. Al-Qenaie S. W. Charles R. Moskowitz K. Raj 《Colloid and polymer science》1982,260(3):333-338
The thermal conductivity of a number of ferrofluids consisting of colloidally dispersed Fe3O4 particles in diester, hydrocarbon, water and fluorcarbon carriers have been measured at 38°C. The variation in thermal conductivity with particle concentration is well described by Tareef's equation (1940). This has enabled the ratio of the physical to magnetic size to be determined and compared with estimates of the ratio obtained from electron micrographs and magnetic measurements.The fit between theory and experiment is particularly good for hydrocarbon carrier fluids giving the ratio of solid to magnetic radiusR
i/R
m=1.24±0.03 compared with the value obtained from magnetic data and electron micrographs of 1.19±0.07. The corresponding value from the fluids with a diester carrier ranges between 1.1<R
d/R
m<1.3 which is again consistent with microscopy and magnetic data.The application of a magnetic field of 0.1 T had no noticeable effect on the thermal conductivities of ferrofluids. 相似文献
19.
K.S. Morley N.V. Tokareva V.K. Popov J. Zhang S.M. Howdle 《European Polymer Journal》2007,43(2):307-314
A supercritical fluid (SCF) route for facile and homogeneous introduction of silver nanoparticles into polymer hosts is described. Our focus is on ultra-high molecular weight polyethylene (UHMWPE). We demonstrate that the metallic nanoparticles have a substantial effect upon the wear and tribochemical properties of the polymer substrate. 相似文献
20.
P. Placke V. Edel L. Reversat R. Richert E. W. Fischer 《Colloid and polymer science》1995,273(12):1156-1162
Structural relaxations of an electrorheological fluid (ERF) due to changes in the applied electrical field strength or shear rate are observed on time scales 1 s<t<40 000 s. Commercial ERFs consisting of mesoscopic polyurethane particles in a silicone oil matrix were studied by three different experimental techniques in order to obtain and compare the characteristic relaxation times. It is demonstrated that dielectric spectroscopy, viscosimetry and light transmission experiments represent the same results concerning the structural relaxation phenomena of ERFs when electrical fields are applied. The tendency of strong induced dipoles to align the particles in the direction of the field increases the effective dipole moment and therefore , the shear viscosity and the amount of light transmitted along the field direction in an ITO/glass sandwich cell. The optical experiment is capable of resolving fast processes within the first 1 ms if large electrical fields are applied. The effects of electrophoresis and shearing, which both counteract the field induced structures, are also addressed. 相似文献