全文获取类型
收费全文 | 4048篇 |
免费 | 372篇 |
国内免费 | 80篇 |
专业分类
化学 | 103篇 |
晶体学 | 7篇 |
力学 | 1317篇 |
综合类 | 19篇 |
数学 | 879篇 |
物理学 | 2175篇 |
出版年
2024年 | 19篇 |
2023年 | 43篇 |
2022年 | 47篇 |
2021年 | 62篇 |
2020年 | 146篇 |
2019年 | 137篇 |
2018年 | 91篇 |
2017年 | 116篇 |
2016年 | 91篇 |
2015年 | 123篇 |
2014年 | 202篇 |
2013年 | 239篇 |
2012年 | 150篇 |
2011年 | 246篇 |
2010年 | 179篇 |
2009年 | 231篇 |
2008年 | 277篇 |
2007年 | 237篇 |
2006年 | 222篇 |
2005年 | 173篇 |
2004年 | 170篇 |
2003年 | 175篇 |
2002年 | 150篇 |
2001年 | 108篇 |
2000年 | 107篇 |
1999年 | 79篇 |
1998年 | 93篇 |
1997年 | 73篇 |
1996年 | 68篇 |
1995年 | 52篇 |
1994年 | 45篇 |
1993年 | 45篇 |
1992年 | 40篇 |
1991年 | 48篇 |
1990年 | 23篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 6篇 |
1982年 | 17篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1971年 | 2篇 |
排序方式: 共有4500条查询结果,搜索用时 0 毫秒
161.
M. Rahman 《Applied Mathematical Modelling》1986,10(6):401-408
This paper considers the wave loads on large monolithic offshore structures. The second order wave force formulae developed by Rahman and Heaps, applicable to large circular cylinders in waves, are extended to evaluate the overturning moments on large circular cylinders. The theory is then applied to square section caissons in waves, to predict the wave loads on these structures. These calculations are performed using the exact form of the second order velocity potential, φ2, with arbitrary wave number, k2, and the approximate form of φ2, with twice the value of the wave number of the first order velocity potential. The second order analytical predictions are compared with available experimental data for various ranges of wave parameters for both circular and square caissons in large amplitude waves. 相似文献
162.
The evolution of nonlinear Langmuir waves in the interplanetary medium is investigated by appropriately accounting for the
random density irregularities of the medium. A pair of modified Zakharov equations, which describe these waves, is solved
numerically as an initial value problem for large scale (≫ 102 km) initial pertubations. For an ion acoustic-Langmuir solitary wave, the random irregularities damp the Langmuir wave by
way of scattering and let the ion density perturbation radiate away in a few days. However an initial solitary or shock-like
Langmuir wave excites the ion density perturbations within a fraction of a second, and then itself gets damped. These effects
will strongly decelerate the collapse of large scale Langmuir waves. The possibility of detecting these processes, by means
of interplanetary scintillation, is discussed.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
163.
D. J. Harris H. S. Eggleston 《International Journal of Infrared and Millimeter Waves》1987,8(9):1115-1118
A radiating horn of continuously variable gain using groove-guide is proposed. The beam width in both planes is varied. Some experimental measurements at 100 GHz confirm the behaviour.Work carried out at the University of Wales Institute of Science and Technology, Cardiff, U.K. 相似文献
164.
H. Aynaou V.R. Velasco A. Nougaoui E.H. El Boudouti D. Bria B. Djafari-Rouhani 《Surface science》2005,590(2-3):224-242
We have studied the acoustic waves in the (0 0 1) and (1 1 0) surfaces of AlN, GaN and InN. We have employed the surface Green function matching method and different sets of calculated elastic constants available in the literature for these materials, because no experimental values are available. Important differences are found for the velocities of the bulk and surface acoustic waves coming from these sets of elastic constants, in such a way that they could be easily measured by ultrasonic and Brillouin techniques. These results together with the expressions obtained here for the velocities of the acoustic waves in high symmetry directions could be used to determine the elastic coefficients of these materials. 相似文献
165.
A hyperbolic reaction–diffusion model for the hantavirus infection, generalizing the parabolic set of equations recently derived by Abramson and Kenkre, is proposed within the context of Extended Thermodynamics. The model, as in the parabolic case, captures some of the realistic features of the dynamics of hantavirus in mice population, while it avoids the unphysical features concerning the instantaneous diffusive effects typical of parabolic equations. Traveling wave solutions, related to the spread of the infection in the landscape, are investigated. Both analytical and numerical results obtained herein are discussed and validated from the behavior of the biological system. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
166.
167.
Guido Schneider 《Physica D: Nonlinear Phenomena》2000,140(3-4):283-293
Modulating pulse-solutions consist of a pulse-like envelope advancing in the laboratory frame and modulating an underlying spatially and temporarily oscillating wave train. Such solutions play a big role in nonlinear optics, where information is transported as pulse-like modulations of an underlying electromagnetic wave. For a phenomenological model we prove criteria for the existence and asymptotic stability of such solutions in terms of the coefficients of the associated equation for the envelope. 相似文献
168.
Thin viscous fluid film flows over rotating curvilinear surfaces are considered. The steady-state flow is studied for large and finite Ekman numbers. The possibility of obtaining a film of given thickness is considered. The wave formation on the surface of an inhomogeneous film and the development of nonlinear waves are also investigated. The film flow parameters in the cases of flow over a plane disk and a curvilinear surface are compared. 相似文献
169.
L. V. Perova 《Computational Mathematics and Mathematical Physics》2008,48(6):1001-1023
Propagation of small perturbations in a two-layer inviscid stratified fluid is studied. It is assumed that the higher density fluid occupies the lower unbounded half-space, while the lower density fluid occupies the upper unbounded half-space. The source of the excitation is a plane wave traveling along the interface of the fluids. An explicit analytical solution to the problem is constructed, and its existence and uniqueness are proved. The long-time wave pattern developing in the fluids is analyzed. 相似文献
170.
M. V. Buntina V. V. Ostapenko 《Computational Mathematics and Mathematical Physics》2008,48(12):2241-2253
For the shallow water equations in the first approximation (Saint-Venant equations), a TVD scheme is developed for shock-capturing computations of open channel flows with discontinuous waves. The scheme is based on a special nondivergence approximation of the total momentum equation that does not involve integrals related to the cross-section pressure force and the channel wall reaction. In standard divergence difference schemes, most of the CPU time is spent on the computation of these integrals. Test computations demonstrate that the discontinuity relations reproduced by the scheme are accurate enough for actual discontinuous wave propagation to be numerically simulated. All the qualitatively distinct solutions for a dam collapsing in a trapezoidal channel with a contraction in the tailwater area are constructed as an example. 相似文献