全文获取类型
收费全文 | 454篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
化学 | 119篇 |
力学 | 138篇 |
数学 | 130篇 |
物理学 | 100篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 18篇 |
2020年 | 19篇 |
2019年 | 21篇 |
2018年 | 38篇 |
2017年 | 22篇 |
2016年 | 31篇 |
2015年 | 14篇 |
2014年 | 18篇 |
2013年 | 17篇 |
2012年 | 34篇 |
2011年 | 57篇 |
2010年 | 35篇 |
2009年 | 36篇 |
2008年 | 41篇 |
2007年 | 16篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有487条查询结果,搜索用时 281 毫秒
21.
Wang Yanan Liu Xia Huang Yongshun Hayat Tasawar Alsaedi Ahmed Li Jiaxing 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(1):209-217
Graphene oxide (GO) is an ideal adsorbent due to excellent physicochemical properties. Humic acid (HA) is ubiquitous in aquatic and soil environment, which can affect the migration of metal ions. In this study, we investigated the sorption mechanisms of U(VI) onto GO surfaces in the presence of HA. pH dependent and ionic strength independent sorption process were observed and the concentration of HA is positively proportional to U(VI) sorption capacities. Results also suggest that a pre-mixing HA + U(VI) gave better results than a pre-mixing of GO + HA, which can be explained by the size distribution of different GO systems.
相似文献22.
This article looks at the hydrodynamic elastico-viscous fluid over a stretching surface. The equations governing the flow are reduced to ordinary differential equations, which are analytically solved by applying an efficient technique namely the homotopy analysis method (HAM). The solutions for the velocity components are computed. The numerical values of wall skin friction coefficients are also tabulated. The present HAM solution is compared with the known exact solution for the two-dimensional flow and an excellent agreement is found. 相似文献
23.
24.
25.
This work is concerned with the two-dimensional boundary layer flow of an upper-convected Maxwell (UCM) fluid in a channel
with chemical reaction. The walls of the channel are porous. Employing similarity transformations the governing non-linear
partial differential equations are reduced into non-linear ordinary differential equations. The resulting ordinary differential
equations are solved analytically using homotopy analysis method (HAM). Expressions for series solutions are derived. The
convergence of the obtained series solutions are shown explicitly. The effects of Reynold’s number Re, Deborah number De, Schmidt number Sc and chemical reaction parameter γ on the velocity and the concentration fields are shown through graphs and discussed. 相似文献
26.
This Letter looks at the rotating flow of a second grade fluid past a porous shrinking surface. The fluid is electrically conducting in the presence of a constant applied magnetic field. The governing partial differential equations are first reduced into ordinary differential equations and then solved by homotopy analysis method (HAM). Convergence of the series solution is shown explicitly. In addition, the obtained results are illustrated graphically to indicate the effects of the pertinent physical parameters. 相似文献
27.
The effect of variable viscosity on the peristaltic flow of a Newtonian fluid in an asymmetric channel has been discussed. Asymmetry in the flow is induced due to travelling waves of different phase and amplitude which propagate along the channel walls. A long wavelength approximation is used in the flow analysis. Closed form analytic solutions for velocity components and longitudinal pressure gradient are obtained. The study also shows that, in addition to the effect of mean flow parameter, the wave amplitude also effect the peristaltic flow. This effect is noticeable in the pressure rise and frictional forces per wavelength through numerical integration. 相似文献
28.
In this article, analysis is presented to study the effect of Hall current on the rotating flow of a non-Newtonian fluid in
a porous medium taking into consideration the modified Darcy's law. The Oldroyd-B fluid model is used to characterize the
non-Newtonian fluid behavior. The governing equations for unsteady rotating flow have been modeled in a porous medium. The
analysis includes the flows induced by general periodic oscillations and elliptic harmonic oscillations of a plate. The effect
of the various emerging parameters is discussed on the velocity distribution. The analytical results are confirmed mathematically
by giving comparison with previous studies in the literature. It is observed that the velocity distribution increases with
an increase of Hall parameter. The behavior of permeability is similar to that of the Hall parameter. 相似文献
29.
Exact analytical solutions for a class of unsteady unidirectional flows of an incompressible second-order fluid are constructed. The flows are generated impulsively from rest by motion of a plate or two plates or by sudden application of a pressure gradient. Expressions for velocity, flux and skin friction are obtained for both large and small times. It is found that large and small times solutions are dependent on the coefficient of viscoelasticity. The solutions corresponding to Newtonian fluids can be easily obtained from those for fluids of second order by letting the viscoelastic parameter to be zero. 相似文献
30.
Altaf HussainSardar Sikandar Hayat M.A. Choudhry 《Physica B: Condensed Matter》2011,406(10):1961-1965
The electronic structures and optical properties of TiAl intermetallic alloy system are studied by the first-principle orthogonalized linear combination of atomic orbitals method. Results on the band structure, total and partial density of states, localization index, effective atomic charges, and optical conductivity are presented and discussed in detail. Total density of states spectra reveal that (near the Fermi level) the majority of the contribution is from Ti-3d states. The effective charge calculations show an average charge transfer of 0.52 electrons from Ti to Al in primitive cell calculations of TiAl alloy. On the other hand, calculations using supercell approach reveal an average charge transfer of 0.48 electrons from Ti to Al. The localization index calculations, of primitive cell as well as of supercell, show the presence of relatively localized states even above the Fermi level for this alloy. The calculated optical conductivity spectra of TiAl alloy are rich in structures, showing the highest peak at 5.73 eV for supercell calculations. Calculations of the imaginary part of the linear dielectric function show a prominent peak at 5.71 eV and a plateau in the range 1.1-3.5 eV. 相似文献