全文获取类型
收费全文 | 2788篇 |
免费 | 147篇 |
国内免费 | 62篇 |
专业分类
化学 | 175篇 |
晶体学 | 16篇 |
力学 | 731篇 |
综合类 | 7篇 |
数学 | 1063篇 |
物理学 | 1005篇 |
出版年
2023年 | 29篇 |
2022年 | 21篇 |
2021年 | 47篇 |
2020年 | 45篇 |
2019年 | 33篇 |
2018年 | 36篇 |
2017年 | 48篇 |
2016年 | 79篇 |
2015年 | 82篇 |
2014年 | 139篇 |
2013年 | 226篇 |
2012年 | 121篇 |
2011年 | 212篇 |
2010年 | 168篇 |
2009年 | 238篇 |
2008年 | 263篇 |
2007年 | 217篇 |
2006年 | 149篇 |
2005年 | 101篇 |
2004年 | 86篇 |
2003年 | 88篇 |
2002年 | 54篇 |
2001年 | 53篇 |
2000年 | 43篇 |
1999年 | 65篇 |
1998年 | 60篇 |
1997年 | 34篇 |
1996年 | 35篇 |
1995年 | 18篇 |
1994年 | 31篇 |
1993年 | 26篇 |
1992年 | 20篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1970年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有2997条查询结果,搜索用时 0 毫秒
151.
Niti Nipun Sharma 《Journal of nanoparticle research》2008,10(2):333-340
Emissive power per unit area of a blackbody has been modeled as a function of frequency using quantum electrodynamics, semi-classical
and classical approaches in the available literature. Present work extends the classical lumped-parameter systems model of
Brownian motion of nanoparticle to abstract an emissive power per unit area model for nanoparticle radiating at temperature
greater than absolute zero. The analytical model developed in present work has been based on synergism of local deformation
leading to local motion of nanoparticle due to photon impacts. The work suggests the hypothesis of a free parameter f′ characterizing the damping coefficient of resistive forces to local motion of nanoparticle and the manipulation of which
is possible to realize desired emissivity from nanoparticles. The model is validated with the well established Planck’s radiation
law. 相似文献
152.
Marco Rahm David Schurig Daniel A. Roberts Steven A. Cummer David R. Smith John B. Pendry 《Photonics and Nanostructures》2008,6(1):87-VII
The technique of applying form-invariant, spatial coordinate transformations of Maxwell’s equations can facilitate the design of structures with unique electromagnetic or optical functionality. Here, we illustrate the transformation-optical approach in the designs of a square electromagnetic cloak and an omni-directional electromagnetic field concentrator. The transformation equations are described and the functionality of the devices is numerically confirmed by two-dimensional finite element simulations. The two devices presented demonstrate that the transformation optic approach leads to the specification of complex, anisotropic and inhomogeneous materials with well directed and distinct electromagnetic behavior. 相似文献
153.
G. Parisi M. Ratiéville 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):457-468
We get back to the computation of the leading finite size corrections to some random link matching problems, first adressed
by Mézard and Parisi [J. Phys. France 48, 1451 (1987)]. In the so-called bipartite case, their result is in contradiction with subsequent works. We show that they
made some mistakes, and correcting them, we get the expected result. In the non bipartite case, we agree with their result
but push the analytical treatment further.
Received 28 April 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: giorgio.parisi@roma1.infn.it
RID="b"
ID="b"e-mail: matthieu.ratieville@roma1.infn.it 相似文献
154.
开挖过程的非线性理论分析 总被引:4,自引:2,他引:2
本文从岩土介质力学非线性和变形破坏过程自组织非线性的角度对开挖过程岩土体非线性行为进行了探讨。以此为依据,分析了岩土从微观破坏、滑移面形成、直至整体变形破坏全过程的自组织发生机理,在此基础上,建立了伴随开挖过程岩土体变形破坏的非线性动力学描述方程。 相似文献
155.
Tin-Yau Tam 《Proceedings of the American Mathematical Society》1999,127(1):35-44
For any , let be the following subset of :
We show that if , then is always convex. When , it is an ellipsoid, probably degenerate. The convexity result is best possible in the sense that if we have defined similarly, then there are examples which fail to be convex when and .
The set is also symmetric about the origin for all , and contains the origin when . Equivalent statements of this result are given. The convexity result for is similar to Au-Yeung and Tsing's extension of Westwick's convexity result for .
156.
Modelling flow over a backward–facing step using the F.E.M. and the two-equation model of turbulence
Flow over a downstream-facing step is predicted using the F.E.M. A two-equation model of turbulence is employed where the transport of turbulence kinetic energy and dissipation rate are depicted using transport-type equations, i.e. the two-equation model of turbulence. The results obtained are compared with other models and experimental results. Generally, the model was found to be under-predictive with regard to the reattachment length when previous empirical data was used in the transport equations. 相似文献
157.
158.
Non-destructive testing of tubes using a time reverse numerical simulation (TRNS) method 总被引:4,自引:0,他引:4
A method for the detection of defects in cylindrical structures and the determination of their positions and orientations is presented in this paper. The scattered field, which is generated by the interaction of excited guided waves with a defect, is evaluated with an approach named time reverse numerical simulation method (TRNS). Since the excited waves and the scattered field propagate along the sample, the time-consuming scanning of the whole tube can be eliminated. The scattered displacement field is measured in three dimensions over time with a laser vibrometer at different locations distributed equally around the circumference at a fixed axial coordinate far away from the defect. Instead of analyzing the complicated time signals directly, they are played back in time. If the recorded displacement histories of the scattered field are reversed in time and played back in an identical structure, the waves travel back the same path and interfere to a maximum at their origin. The result is an amplitude increase at the position of the defect where the scattered field was generated. Instead of playing back the recorded time signals in an experiment, this step is replaced by a numerical simulation. Only this enables the visualization and detection of the amplitude increase. As long as the simulation is of high accuracy, the position of the maximum interference corresponds exactly to the location of the defect in the experiment, although no defect is implemented in the simulation. 相似文献
159.
S.?BoettcherEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(4):439-445
A reduction procedure to obtain ground states of spin
glasses on sparse graphs is developed and tested on the
hierarchical lattice associated with the Migdal-Kadanoff
approximation for low-dimensional lattices. While more generally
applicable, these rules here lead to a complete reduction of the
lattice. The stiffness exponent governing the scaling of the
defect energy E with system
size L, (E) ~L
y, is obtained as
y
3 = 0.25546(3) by reducing the equivalent
of lattices up to L =
2100 in d = 3, and as y
4 = 0.76382(4) for up to
L =
235 in d = 4. The reduction rules allow the
exact determination of the ground state energy, entropy, and
also provide an approximation to the overlap distribution. With
these methods, some well-know and some new features of diluted
hierarchical lattices are calculated. 相似文献
160.
U. Schröter 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):297-310
Green's dyadic technique represents a powerful tool for calculations in electrodynamics, especially in modelling optical properties
of nanoscopic objects. The method does not only provide field distributions, but also maps of susceptibilities and densities
of states. Whereas the formalism is well established for dielectrics and electric fields, I present here a straight forward
extension to tensors of both electric and magnetic type as well as mixed ones and furthermore to the situation where objects
with dielectric and magnetic permeabilities are present together. As examples, characteristic field patterns are compared
for elementary dielectric and magnetic perturbations. Green's tensors calculated for a coral structure reveal that mixed susceptibilities
can exhibit other symmetries than pure electric or magnetic ones. Maps of all tensor components can thus give essential clues
to the interpretation of near-field images.
Received 15 December 2002 Published online 20 June 2003
RID="a"
ID="a"Files “maths.ps” and “tensors.ps” are only available in electronic form at http://www.edpsciences.org
RID="b"
ID="b"e-mail: Ursula.Schroeter@uni-konstanz.de 相似文献