全文获取类型
收费全文 | 323400篇 |
免费 | 4529篇 |
国内免费 | 1915篇 |
专业分类
化学 | 177465篇 |
晶体学 | 4559篇 |
力学 | 13290篇 |
综合类 | 73篇 |
数学 | 37763篇 |
物理学 | 96694篇 |
出版年
2021年 | 2011篇 |
2020年 | 2294篇 |
2019年 | 2232篇 |
2018年 | 2212篇 |
2017年 | 2116篇 |
2016年 | 4286篇 |
2015年 | 3634篇 |
2014年 | 4892篇 |
2013年 | 14644篇 |
2012年 | 11541篇 |
2011年 | 14220篇 |
2010年 | 8899篇 |
2009年 | 8809篇 |
2008年 | 13000篇 |
2007年 | 13202篇 |
2006年 | 12771篇 |
2005年 | 11612篇 |
2004年 | 10433篇 |
2003年 | 9111篇 |
2002年 | 8919篇 |
2001年 | 10228篇 |
2000年 | 7804篇 |
1999年 | 6211篇 |
1998年 | 4957篇 |
1997年 | 4791篇 |
1996年 | 4825篇 |
1995年 | 4409篇 |
1994年 | 4151篇 |
1993年 | 3969篇 |
1992年 | 4463篇 |
1991年 | 4319篇 |
1990年 | 4041篇 |
1989年 | 3851篇 |
1988年 | 4140篇 |
1987年 | 3805篇 |
1986年 | 3692篇 |
1985年 | 5341篇 |
1984年 | 5413篇 |
1983年 | 4391篇 |
1982年 | 4760篇 |
1981年 | 4800篇 |
1980年 | 4555篇 |
1979年 | 4672篇 |
1978年 | 4674篇 |
1977年 | 4653篇 |
1976年 | 4601篇 |
1975年 | 4517篇 |
1974年 | 4364篇 |
1973年 | 4527篇 |
1972年 | 2572篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
831.
P. Pellegrino B. Garrido C. García R. Ferr J. A. Moreno J. R. Morante 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):424
The ability of surface passivation to enhance the photoluminescence (PL) emission of Si nanocrystals in SiO2 has been investigated. Silicon precipitation in implanted samples takes place in a time scale of few minutes at 1100°C. For longer annealing at the same temperature, the PL intensity of the Si nanocrystals increases and eventually reaches saturation, while it correlates inversely with the amount of Si dangling bonds at the Si–SiO2 interface (Pb centers), as measured by electron spin resonance. This combined behavior is independent on the silica matrix properties, implantation profiles and annealing atmosphere and duration. The observation that the light emission enhancement is directly related to the annealing of Pb centers is confirmed by treatment in forming gas. This mild hydrogenation at much lower temperature (450°C) leads to a complete passivation of the Pb defects, increasing at the same time the PL yield and the lifetime. 相似文献
832.
This paper describes how parametric cubic splines and cubicBezier curves may be used in designing a two dimensional shape.A simple aerofoil shape is designed using both methods. Themathematics is described and the shape drawn using Excel. Theeffect of varying parameters is shown in both methods. 相似文献
833.
834.
Role of the microstructure on the transport properties of Y-doped zirconia and Gd-doped ceria 总被引:1,自引:1,他引:0
Transmission electron microscopy characterizations and XPS analyses have allowed us to show the influence of the microstructure
and nanochemistry on the transport properties of Y2O3-(9 mol%)-stabilized zirconia (YSZ) and Gd2O3 (10 mol%)-doped ceria (GDC). The grain boundary electrical conductivity (σgb) and oxygen diffusion coefficient (Do) of conventional YSZ ceramics increase with the grain size, while an opposite behavior was found for GDC samples. This difference
was attributed to glassy precipitates present at YSZ grain boundaries. Furthermore, it was shown that kinetic demixing processes
take place during cooling, at the end of sintering. This causes important changes in the cationic species distribution at
interfaces and plays an important role on the transport properties of these two materials.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
835.
J.-P. Blaizot E. Iancu A. Rebhan 《The European Physical Journal C - Particles and Fields》2003,27(3):433-438
We compare our previously proposed hard-thermal-loop (HTL) resummed calculation of quark number susceptibilities using a
self-consistent two-loop approximation to the quark density with a recent calculation of the same quantity at the one-loop
level in a variant of HTL-screened perturbation theory. Besides pointing out conceptual problems with the latter approach,
we show that it severely over-includes the leading-order interaction effects, while including none of the plasmon terms, which
is the main reason for requiring improved resummation schemes.
Received: 27 June 2002 / Revised version: 23 September 2002 / Published online: 31 January 2003 相似文献
836.
837.
Y. V. Bludov A. J. Kirichenko A. E. Kogut V. V. Kutuzov V. A. Solodovnik 《Radiophysics and Quantum Electronics》2005,48(12):927-933
We experimentally study a new type of resonator, namely, a barrel-shaped dielectric resonator with whispering-gallery modes
which is formed by the cutting dielectric hemisphere. Compared with a hemispherical dielectric resonator, the E type oscillation
spectrum of such a resonator is rarefied with respect to the azimuthal index. Comparative analysis of the electromagnetic
characteristics of the barrel-shaped dielectric resonator and half-disk dielectric resonators shows that the radiation losses
of the mode energy from the spherical surface are smaller than those from the cylindrical surface. This fact stimulates the
high values of the internal Q-factor of modes of the barrel-shaped dielectric resonator.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 12, pp. 1041–1048, December 2005. 相似文献
838.
E.J. Avital 《Journal of sound and vibration》2004,270(3):483-494
A new Dispersion-Relation-Preserving (DRP) scheme has been developed using the Lax-Wendroff methodology. Two collocated grids are placed in a staggered formation and a staggered DRP scheme is used to calculate the spatial differentiation of the propagation and convection terms. A staggered filtering scheme of a six points stencil is developed to complete the transformation from one grid to another. Existing DRP Runge-Kutta schemes are used for the time marching. Stability limits and accuracy issues are investigated using a simple 1D advection equation. The new method is then tested for monopole and quadrupole radiation, diffraction effects of an aperture in a wall, and convection effects of shear flow. All demonstrate the good accuracy and numerical stability of the new method. 相似文献
839.
Elliott Lieb's ice-type models opened up the whole field of solvable models in statistical mechanics. Here we discuss the “commuting transfer matrix” T,Qequations for these models, writing them in a more explicit and transparent notation that we believe offers new insights. The approach manifests the relationship between the six-vertex and chiral Potts models, and between the eight-vertex and Kashiwara–Miwa models. 相似文献
840.
W. Shi Y.J. Ding C. Fang Q. Pan Q. Gu 《Applied Physics A: Materials Science & Processing》2003,77(3-4):567-570
The optimal corona-poling temperature of polymer films was accurately determined by measuring the temperature dependence of the in situ second-harmonic (SH) intensity profile under the applied poling electric field. The in situ SH intensity profile was first measured by probing both the surface voltages and the poling currents induced by surface/space charges for the corona-poled polymer films. Moreover, charge effects on the stability of the chromophore orientation were first studied by using the thermally stimulated discharge-current technique. PACS 72.20.Jv; 42.65.Ky; 73.61.Ph; 81.40.Tv 相似文献