全文获取类型
收费全文 | 510篇 |
免费 | 48篇 |
国内免费 | 2篇 |
专业分类
化学 | 345篇 |
晶体学 | 2篇 |
力学 | 18篇 |
数学 | 39篇 |
物理学 | 156篇 |
出版年
2024年 | 6篇 |
2023年 | 9篇 |
2022年 | 25篇 |
2021年 | 28篇 |
2020年 | 22篇 |
2019年 | 19篇 |
2018年 | 27篇 |
2017年 | 21篇 |
2016年 | 23篇 |
2015年 | 25篇 |
2014年 | 26篇 |
2013年 | 39篇 |
2012年 | 46篇 |
2011年 | 45篇 |
2010年 | 22篇 |
2009年 | 19篇 |
2008年 | 25篇 |
2007年 | 11篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有560条查询结果,搜索用时 0 毫秒
531.
The present study explores the free convective oblique Casson fluid over a stretching surface with non-linear thermal radiation effects. The governing physical problem is modelled and transformed into a set of coupled non-linear ordinary differential equations by suitable similarity transformation, which are solved numerically with the help of shooting method keeping the convergence control of 10-5 in computations. Influence of pertinent physical parameters on normal, tangential velocity profiles and temperature are expressed through graphs. Physical quantities of interest such as skin friction coefficients and local heat flux are investigated numerically. 相似文献
532.
533.
534.
Microwave-assisted parallel synthesis of a 4,6-diamino-2,2-dimethyl-1,2-dihydro-1-phenyl-s-triazine library 总被引:3,自引:0,他引:3
Microwave-assisted parallel synthesis of a library of 20 phenyl dihydrotriazines was successfully achieved and compared to an identical library generated by conventional parallel synthesis. Microwave synthesis dramatically decreased reaction times from an average of 22 h to 35 min, and compounds generated using microwave irradiation were purer. Isolated yields of all the compounds were comparable when the two methods were used. 相似文献
535.
Breese MB Teo EJ Rana MA Huang L van Kan JA Watt F King PJ 《Physical review letters》2004,92(4):045503
High spatial resolution, high-contrast transmission channeling images of stacking faults in silicon have been produced using a beam of 2 MeV protons focused to a spot size of 60 nm. Over a narrow range of beam tilts to the (011) planes, up to ten periodic intensity oscillations are observed, providing evidence of a long-range coherency of the planar channeled trajectories. This behavior is characterized using Monte Carlo computer simulations, and a phase-space model of planar channeled ion interactions with stacking faults is developed which incorporates all observed channeling and blocking phenomena. 相似文献
536.
M.A. Rana T. Osipowicz H.W. Choi M.B.H. Breese F. Watt S.J. Chua 《Applied Physics A: Materials Science & Processing》2003,77(1):103-108
Annealling experiments were performed on GaN layers, grown on sapphire, over a wide range of temperatures (500–1100 °C). Rutherford
Backscattering Spectrometry (RBS) was performed in random and 〈0001〉 channelling geometries using 2 MeV protons and helium
ions to determine the stoichiometric and structural alterations produced during annealling. We present here, for the first
time, a comprehensive and quantitative analysis of the depth distribution of both stoichiometric and structural changes in
the near-surface region (∼750 nm) with a resolution of 50 nm for stoichiometric and 20 nm for structural changes. No decomposition
was measured for temperatures up to 800 °C. Decomposition in the near-surface region increased rapidly with further increases
in temperature, resulting in a near-amorphous region (500 nm) for annealling at 1100 °C. We describe the range of annealling
conditions under which negligible stoichiometric and structural changes are observed. Our nanoscale resolution results are
useful for the fabrication and operation of conventional and nanoscale optoelectronic and high-temperature devices.
Received: 23 December 2002 / Accepted: 16 January 2003 / Published online: 28 March 2003
RID="*"
ID="*"Corresponding author. Fax: +65-6777/6126, E-mail: scip0229@nus.edu.sg 相似文献
537.
A self-consistent theory of dyons in Abelian and non-Abelian limits has been formulated in terms of an extra magnetic symmetry
and topological magnetic charge. It has been shown that the restricted gauge potential describes the fields of dyons in terms
of two regular (time-like) potentials only when recourse is made to the duality of topological (magnetic) and isocolour (electric)
charges. Choosing a suitable Lagrangian density for the system of dyons in non-Abelian gauge theory, the field equations,
energy-momentum tensor, Hamiltonian and momentum densities have also been derived and the conservation of the four-linear
momentum and the total angular momentum has been demonstrated. 相似文献
538.
Rana N.S. Sodhi C.E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1985,37(1):97-123
Electron energy loss Spectroscopy has been used to obtain the inner shell electronic excitation spectra of PH3, PF3, PCl3 and P(CH3)3 in the phosphorus L-shell (P 2p, 2s) region as well as the respective ligand K -shells (F 1s, C 1s) and L-shell (Cl 2p and 2s) regions. The spectra were obtained under small momentum transfer conditions so that dipole-allowed transitions dominate. An impact energy of 2.5 ke V was used and inelastically scattered electrons were detected at a typical scattering angle of about 1°. A dipoleforbidden transition of unusual character is observed at 135.11 eV in the P 2p spectrum of PCl3. Although optically forbidden, as indicated by its absence in a soft X-ray absorption spectrum, the intensity of this transition rises very rapidly with increase in momentum transfer. 相似文献
539.
Planar Channelling Criticalities of MeV Protons in Si Crystal: Simulations, Evaluation and Applications
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mukhtar Ahmed Rana 《中国物理快报》2008,25(10):3724-3727
We reports a phase-space structure of MeV proton beam planar channelled along {110} planes in Si crystal using simulation results with the help of a computer code FLUX. The aim is to understand channelling conditions suitable for disorder measurement in crystals. Phase-space distribution of a planar channelled proton beam evolutes in a systematic fashion when it travels into the crystal. Planar channelled beam oscillates between phase-like and space-like conditions in which a part of the beam becomes under phase and space criticalities. These criticality conditions in planar channelling are analysed, explained and discussed with the perspective of defect measurement in crystals. 相似文献
540.
This article investigates the effects of variable thermal conductivity and variable mass diffusion coefficient on the transport of heat and mass in the flow of Casson fluid. Numerical simulations for two-dimensional flow induced by stretching surface are performed by using Galerkin finite element method (GFEM) with linear shape functions. After assembly process, nonlinear algebraic equations are linearized through Picard method and resulting linear system is solved iteratively using Gauss Seidal method with simulation tolerance 10-8. Maximum value of independent variable η is searched through numerical experiments. Grid independent study was carried out and error analysis is performed. Simulated results are validated by comparing with already published results. Parametric study is carried out to explore the physics of the flow. The concentration increases when mass diffusion coefficient is increased. The concentration and thermal boundary layer thicknesses increase when ε1 and ε are increased. The effect of generative chemical reaction on concentration is opposite to the effect of destructive chemical reaction on the concentration. 相似文献