全文获取类型
收费全文 | 245143篇 |
免费 | 3169篇 |
国内免费 | 518篇 |
专业分类
化学 | 136625篇 |
晶体学 | 3864篇 |
力学 | 8730篇 |
综合类 | 12篇 |
数学 | 27536篇 |
物理学 | 72063篇 |
出版年
2021年 | 1874篇 |
2020年 | 2360篇 |
2019年 | 2479篇 |
2018年 | 3136篇 |
2017年 | 3179篇 |
2016年 | 5113篇 |
2015年 | 3496篇 |
2014年 | 4805篇 |
2013年 | 11945篇 |
2012年 | 9192篇 |
2011年 | 10517篇 |
2010年 | 7363篇 |
2009年 | 7065篇 |
2008年 | 9352篇 |
2007年 | 9067篇 |
2006年 | 8464篇 |
2005年 | 7876篇 |
2004年 | 7078篇 |
2003年 | 6405篇 |
2002年 | 5999篇 |
2001年 | 6990篇 |
2000年 | 5492篇 |
1999年 | 4118篇 |
1998年 | 3227篇 |
1997年 | 3102篇 |
1996年 | 3125篇 |
1995年 | 2818篇 |
1994年 | 2783篇 |
1993年 | 2584篇 |
1992年 | 3256篇 |
1991年 | 3080篇 |
1990年 | 3061篇 |
1989年 | 3004篇 |
1988年 | 3030篇 |
1987年 | 3012篇 |
1986年 | 2873篇 |
1985年 | 3711篇 |
1984年 | 3669篇 |
1983年 | 2898篇 |
1982年 | 2998篇 |
1981年 | 3064篇 |
1980年 | 2789篇 |
1979年 | 3123篇 |
1978年 | 3091篇 |
1977年 | 3198篇 |
1976年 | 3058篇 |
1975年 | 2757篇 |
1974年 | 2733篇 |
1973年 | 2693篇 |
1968年 | 1852篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
111.
112.
Jürgen Kurths M. Carmen Romano Marco Thiel Grigory V. Osipov Mikhail V. Ivanchenko István Z. Kiss John L. Hudson 《Nonlinear dynamics》2006,44(1-4):135-149
We present two different approaches to detect and quantify phase synchronization in the case of coupled non-phase coherent
oscillators. The first one is based on the general idea of curvature of an arbitrary curve. The second one is based on recurrences
of the trajectory in phase space. We illustrate both methods in the paradigmatic example of the R?ssler system in the funnel
regime. We show that the second method is applicable even in the case of noisy data. Furthermore, we extend the second approach
to the application of chains of coupled systems, which allows us to detect easily clusters of synchronized oscillators. In
order to illustrate the applicability of this approach, we show the results of the algorithm applied to experimental data
from a population of 64 electrochemical oscillators. 相似文献
113.
114.
115.
116.
Trichloroethylene has been found to act as a rate enhancing co-factor in the liquid phase, tantalum (V) halide catalyzed, fluorine-for-chlorine exchange reaction of 1,2-dichloro-1,1-difluoroethane (R-132b) to 2-chloro-1,1,1-trifluorethane (R-133a). Several trifluoromethyl substituted benzenes have also been found to be rate-enhancing solvents. 相似文献
117.
Any system that approximates an infinite lattice by a family of finite clusters (with periodic boundary conditions) passes through an intermediate region with enlarged (hidden) symmetry as the system size is increased. The hidden symmetry allows for extra degeneracies and level crossings and has application to exact-diagonalization studies, Monte Carlo simulations, lattice gauge theories, and renormalization group calculations. 相似文献
118.
F. Seiffert R. Schwengner G. Winter L. Funke W. Lieberz R. Reinhardt K. P. Schmittgen D. Weil R. Wrzal K. O. Zell P. von Brentano 《Zeitschrift für Physik A Hadrons and Nuclei》1991,340(2):141-153
Excited states of73Se have been investigated up to spin, 21/2 using techniques of in-beamγ-ray spectroscopy in connection with the70Ge(α, n) reaction. Mean lifetimes of 12 levels have been determined applying Doppler-shift andγ-RF-methods. Five different bands have been identified that reflect a variety of different excitation modes. The decoupled 9/2+ band is likely to correspond to an oblate deformation while the 5/2+ band is interpreted as a strongly coupled prolate band built on the Nilsson configuration [422] 5/2+. The 3/2? band is a strongly coupled band built on the [301] 3/2} configuration.Nuclear reactions:70Ge(α,n),E=14, 16, 18, 19, 20MeV; measuredE γ,I γ,σ(E γ,θ),γγ-coin, linear polarization, DSA,γ(t).75Se deduced levels,I, π, τ, δ(E2/M1), B(σλ). Enriched targets, Ge detectors. 相似文献
119.
120.
Ram K. Ganesh 《国际流体数值方法杂志》1991,13(5):557-578
The total drag force on the surface of a body, which is the sum of the form drag and the skin friction drag in a 2D domain, is numerically evaluated by integrating the energy dissipation rate in the whole domain for an incompressible Stokes fluid. The finite element method is used to calculate both the energy dissipation rate in the whole domain as well as the drag on the boundary of the body. The evaluation of the drag and the energy dissipation rate are post-processing operations which are carried out after the velocity field and the pressure field for the flow over a particular profile have been obtained. The results obtained for the flow over three different but constant area profiles—a circle, an ellipse and a cross-section of a prolate spheroid—with uniform inlet velocity are presented and it is shown that the total drag force times the velocity is equal to the total energy dissipation rate in the entire finite flow domain. Hence, by calculating the energy dissipation rate in the domain with unit velocity specified at the far-field boundary enclosing the domain, the drag force on the boundary of the body can be obtained. 相似文献