全文获取类型
收费全文 | 490755篇 |
免费 | 6000篇 |
国内免费 | 1775篇 |
专业分类
化学 | 259867篇 |
晶体学 | 7496篇 |
力学 | 21790篇 |
综合类 | 8篇 |
数学 | 58532篇 |
物理学 | 150837篇 |
出版年
2020年 | 3488篇 |
2019年 | 3728篇 |
2018年 | 4410篇 |
2017年 | 4233篇 |
2016年 | 7194篇 |
2015年 | 5181篇 |
2014年 | 7758篇 |
2013年 | 21847篇 |
2012年 | 16501篇 |
2011年 | 20419篇 |
2010年 | 13535篇 |
2009年 | 13441篇 |
2008年 | 18796篇 |
2007年 | 19027篇 |
2006年 | 18253篇 |
2005年 | 16544篇 |
2004年 | 15042篇 |
2003年 | 13338篇 |
2002年 | 13169篇 |
2001年 | 14836篇 |
2000年 | 11374篇 |
1999年 | 9120篇 |
1998年 | 7491篇 |
1997年 | 7348篇 |
1996年 | 7221篇 |
1995年 | 6581篇 |
1994年 | 6323篇 |
1993年 | 6250篇 |
1992年 | 6735篇 |
1991年 | 6740篇 |
1990年 | 6298篇 |
1989年 | 6098篇 |
1988年 | 6444篇 |
1987年 | 6015篇 |
1986年 | 5746篇 |
1985年 | 8134篇 |
1984年 | 8320篇 |
1983年 | 6856篇 |
1982年 | 7269篇 |
1981年 | 7227篇 |
1980年 | 6914篇 |
1979年 | 7195篇 |
1978年 | 7240篇 |
1977年 | 7204篇 |
1976年 | 7190篇 |
1975年 | 6865篇 |
1974年 | 6782篇 |
1973年 | 6954篇 |
1972年 | 4443篇 |
1971年 | 3488篇 |
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
941.
T. Ishii M. Asai A. Makishima I. Hossain P. Kleinheinz M. Ogawa M. Matsuda S. Ichikawa 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):15-19
Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T
1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the
doubly magic 68Ni and its neighbor 69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
942.
Understanding of the basic nature of arc root fluctuation is still one of the unsolved problems in thermal arc plasma physics.
It has direct impact on myriads of thermal plasma applications being implemented at present. Recently, chaotic nature of arc
root behavior has been reported through the analysis of voltages, acoustic and optical signals which are generated from a
hollow copper electrode arc plasma torch. In this paper we present details of computations involved in the estimation process
of various dynamic properties and show how they reflect chaotic behavior of arc root in the system. 相似文献
943.
Th. Gerrits H. A. M. van den Berg J. Hohlfeld O. Gielkens L. Br Th. Rasing 《Journal of magnetism and magnetic materials》2002,240(1-3):283-286
We have measured the response of a 20×10 μm, 8 nm thin NiFe (80:20) permalloy film due to excitation by short in-plane magnetic field pulses. We will show that using a two-pulse-technique a complete control of the precessional motion of the magnetisation can be achieved on picosecond timescales. Furthermore, we will present numerical calculations which show that a complete suppression of magnetisation ringing after switching can only be realised by a cascade of short field pulses. 相似文献
944.
W. Kockelmann M. Hofmann O. Moze S.J. Kennedy K.H.J. Buschow 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):25-32
The element distributions and the magnetic ordering behaviour of compounds RNi10Si2 (R
=
Tb, Dy, Ho, Er, Tm) have been studied by neutron powder diffraction down to temperatures of 1.6 K. The compounds crystallize
in an ordered variant of the ThMn12 structure type in the tetragonal space group P4/nmm. An ordered 1:1 distribution of Ni and Si on sites 4d and 4e, respectively,
corresponds to a modulation vector [0, 0, 1] with respect to the space group I4/mmm of the ThMn12 structure. TbNi10Si2 orders antiferromagnetically below T
N
= 4.5 K with a magnetic propagation vector of [0, 0, 1/2]. The magnetic Tb moments, 8.97(2) /Tb atom at 1.6 K, are aligned along the c-axis. The Ni sites in TbNi10Si2 do not carry any ordered magnetic moments. The compounds with R
=
Dy, Ho, Er, and Tm are paramagnetic down to 1.6 K and 3.0 K, respectively.
Received 10 July 2002 / Received in final form 12 September 2002 Published online 29 October 2002 相似文献
945.
K. Weibert J. Main G. Wunner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):379-388
In the periodic orbit quantization of physical systems, usually only the leading-order ? contribution to the density of states is considered. Therefore, by construction, the eigenvalues following from semiclassical
trace formulae generally agree with the exact quantum ones only to lowest order of ?. In different theoretical work the trace formulae have been extended to higher orders of ?. The problem remains, however, how to actually calculate eigenvalues from the extended trace formulae since, even with ? corrections included, the periodic orbit sums still do not converge in the physical domain. For lowest-order semiclassical trace formulae the convergence problem can be elegantly, and universally, circumvented by application of the
technique of harmonic inversion. In this paper we show how, for general scaling chaotic systems, also higher-order
? corrections to the Gutzwiller formula can be included in the harmonic inversion scheme, and demonstrate that corrected semiclassical
eigenvalues can be calculated despite the convergence problem. The method is applied to the open three-disk scattering system,
as a prototype of a chaotic system.
Received 10 September 2001 and Received in final form 3 January 2002 相似文献
946.
The standard model on non-commutative space-time 总被引:1,自引:0,他引:1
X. Calmet B. Jurčo P. Schupp J. Wess M. Wohlgenannt 《The European Physical Journal C - Particles and Fields》2002,23(2):363-376
We consider the standard model on a non-commutative space and expand the action in the non-commutativity parameter . No new particles are introduced; the structure group is . We derive the leading order action. At zeroth order the action coincides with the ordinary standard model. At leading order
in we find new vertices which are absent in the standard model on commutative space-time. The most striking features are couplings
between quarks, gluons and electroweak bosons and many new vertices in the charged and neutral currents. We find that parity
is violated in non-commutative QCD. The Higgs mechanism can be applied. QED is not deformed in the minimal version of the
NCSM to the order considered.
Received: 29 November 2001 / Published online: 25 January 2002 相似文献
947.
A self-consistent model of the development of dendrites and partial discharges in a dielectric solid under a variable voltage
is suggested. Dendrites originate at sites with the enhanced local field strength and also where the dielectric is broken
down under the action of partial discharges. The numerical simulation is used to quantitatively describe the space-time dynamics
of the dendrites and partial discharges in epoxy resin for the tip-plane electrode configuration. The simulated data are compared
with electrical measurements of partial discharges and with optical images of dendrite growth under the same conditions. 相似文献
948.
Ivonin I. V. Krasil'nikova L. M. Lavrent'eva L. G. Porokhovnichenko L. P. 《Russian Physics Journal》2002,45(5):493-497
Experimental proofs of asymmetric trapping of atoms at the growth step in vapor-phase epitaxy of gallium arsenide in the GaAs–AsCl3–H2 system are given. The data obtained confirm the important role of the surface diffusion mass transfer in the growth of epitaxial GaAs layers on vicinals in the neighborhood of (111)A. The effective diffusion length is estimated. 相似文献
949.
Fields due to an electromagnetic wave propagating in a long irregular two-dimensional waveguide are calculated efficiently, using the method of left-right splitting to solve the coupled integral equations. Results are compared with those obtained from independent ray-theoretic calculations and give very close agreement. The approach has previously been applied to rough surfaces at low angles of incidence; here it is found to converge rapidly for surface slopes of 30°, and after a few iterations for incident angles up to 60° from grazing. 相似文献
950.