全文获取类型
收费全文 | 450351篇 |
免费 | 4342篇 |
国内免费 | 1335篇 |
专业分类
化学 | 233674篇 |
晶体学 | 7328篇 |
力学 | 20977篇 |
综合类 | 9篇 |
数学 | 52227篇 |
物理学 | 141813篇 |
出版年
2020年 | 3506篇 |
2019年 | 3970篇 |
2018年 | 5269篇 |
2017年 | 5178篇 |
2016年 | 7617篇 |
2015年 | 4604篇 |
2014年 | 7479篇 |
2013年 | 18994篇 |
2012年 | 14142篇 |
2011年 | 17389篇 |
2010年 | 12380篇 |
2009年 | 12220篇 |
2008年 | 16222篇 |
2007年 | 16341篇 |
2006年 | 15393篇 |
2005年 | 13894篇 |
2004年 | 12863篇 |
2003年 | 11532篇 |
2002年 | 11417篇 |
2001年 | 12762篇 |
2000年 | 9828篇 |
1999年 | 7653篇 |
1998年 | 6687篇 |
1997年 | 6538篇 |
1996年 | 6225篇 |
1995年 | 5719篇 |
1994年 | 5801篇 |
1993年 | 5620篇 |
1992年 | 6103篇 |
1991年 | 6265篇 |
1990年 | 5995篇 |
1989年 | 5803篇 |
1988年 | 5928篇 |
1987年 | 5706篇 |
1986年 | 5390篇 |
1985年 | 7350篇 |
1984年 | 7674篇 |
1983年 | 6368篇 |
1982年 | 6629篇 |
1981年 | 6532篇 |
1980年 | 6419篇 |
1979年 | 6500篇 |
1978年 | 6879篇 |
1977年 | 6687篇 |
1976年 | 6851篇 |
1975年 | 6323篇 |
1974年 | 6352篇 |
1973年 | 6527篇 |
1972年 | 4585篇 |
1971年 | 3843篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
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
972.
Field emission projector studies of fullerene coatings deposited on tungsten tip field emitters reveal specific ordered patterns in the form of doublets, quadruplets, rings, disks, and other forms in the emitter images. The ways in which these types of ordered emission patterns arise and their relation to C60 microformations have been established. Possible causes of the emergence of the ordered emission images are analyzed on the basis of published data and experimental results obtained. A modification of the model of field emission from the surface of microformations taking into account internal reflection of the electronic waves from the formation boundaries has been proposed. 相似文献
973.
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
974.
V.A. Khoze A.D. Martin M.G. Ryskin 《The European Physical Journal C - Particles and Fields》2002,23(2):311-327
We study the double-diffractive production of various heavy systems (e.g. Higgs, dijet, and SUSY particles) at LHC and Tevatron collider energies. In each case we compute the probability that the rapidity gaps,
which occur on either side of the produced system, survive the effects of soft rescattering and QCD bremsstrahlung effects.
We calculate both the luminosity for different production mechanisms, and a wide variety of subprocess cross sections. The
results allow numerical predictions to be readily made for the cross sections of all these processes at the LHC and the Tevatron
collider. For example, we predict that the cross section for the exclusive double-diffractive production of a 120 GeV Higgs boson at the LHC is about 3 fb, and that the QCD background in the decay mode is about 4 times smaller than the Higgs signal if the experimental missing-mass resolution is 1 GeV. For completeness
we also discuss production via or WW fusion.
Received: 7 November 2001 / Revised version: 11 December 2001 / Published online: 25 January 2002 相似文献
975.
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
976.
R. Enberg L. Motyka G. Poludniowski 《The European Physical Journal C - Particles and Fields》2002,26(2):219-228
Diffractive heavy vector meson photoproduction accompanied by proton dissociation is studied for arbitrary momentum transfer.
The process is described by the non-forward BFKL equation, for which a complete analytical solution is found, giving the scattering
amplitude. The impact of non-leading corrections to the BFKL equation is also analysed. Results are compared to the HERA data
on production.
Received: 2 July 2002 / Revised version: 29 August 2002 / Published online: 18 October 2002 相似文献
977.
G. Kh. Panova M. N. Khlopkin N. A. Chernoplekov A. A. Shikov 《Physics of the Solid State》2002,44(7):1218-1223
The specific heats of the Ni2B amorphous system and of its crystal analog were studied in the temperature range 3–270 K. The data obtained permitted us to isolate the contribution due to atomic vibrations from the experimentally measured specific heat, determine the electronic density of states at the Fermi level and the temperature dependence of the characteristic Debye parameter Θ, and to calculate some average frequencies (moments) of the vibrational spectrum. The electronic density of states at the Fermi level increases under amorphization. An analysis of the temperature dependence of the lattice specific heat showed that amorphization brings about a substantial growth in the density of vibrational states at low frequencies, whereas the spectrum-averaged and rms frequencies change very little, which is in good agreement with neutron diffraction measurements. 相似文献
978.
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
979.
The most promising next generation Image Velocimtry (IV) is the high-speed Dynamic PIV. It requires the development of innovative
high-speed video camera sensors. We started by specifying the required performance of these new sensors, for measurements
in air and water flows. These criteria founded on the most recent developments in PIV algorithms and incorporate results from
a large questionnaire survey of users of high-speed video cameras in Japan. The results suggest that the followings are required:
(1) frame rate of 1,000,000 fps, (2) pixel count of 1,000,000 pixels, (3) frame storage capacity of 100–200 frames for tracing
a single event and 10,000 frames for turbulent measurements, (4) gray levels of 4–8 bits for PTV; 12 bits for observation.
Finally, we reviewed the state of the art of high-speed video-image sensors. Currently the standard parallel-readout sensors
can operate at 1 Kfps with a pixel count of approximately 1 Kpixels. The In-situ Storage Image Sensor (ISIS) developed by
the authors has recently achieved frame rates of 1 Mfps. 相似文献
980.