全文获取类型
收费全文 | 485305篇 |
免费 | 3773篇 |
国内免费 | 1404篇 |
专业分类
化学 | 238090篇 |
晶体学 | 7533篇 |
力学 | 23721篇 |
综合类 | 7篇 |
数学 | 67969篇 |
物理学 | 153162篇 |
出版年
2020年 | 3418篇 |
2019年 | 3914篇 |
2018年 | 11933篇 |
2017年 | 12499篇 |
2016年 | 10535篇 |
2015年 | 5006篇 |
2014年 | 7213篇 |
2013年 | 17903篇 |
2012年 | 16616篇 |
2011年 | 26039篇 |
2010年 | 17157篇 |
2009年 | 17142篇 |
2008年 | 23510篇 |
2007年 | 26394篇 |
2006年 | 14540篇 |
2005年 | 18096篇 |
2004年 | 14413篇 |
2003年 | 13422篇 |
2002年 | 11704篇 |
2001年 | 11780篇 |
2000年 | 9330篇 |
1999年 | 7016篇 |
1998年 | 6024篇 |
1997年 | 5957篇 |
1996年 | 5744篇 |
1995年 | 4973篇 |
1994年 | 5007篇 |
1993年 | 5050篇 |
1992年 | 5337篇 |
1991年 | 5533篇 |
1990年 | 5222篇 |
1989年 | 5205篇 |
1988年 | 5168篇 |
1987年 | 5031篇 |
1986年 | 4761篇 |
1985年 | 6401篇 |
1984年 | 6708篇 |
1983年 | 5410篇 |
1982年 | 5836篇 |
1981年 | 5668篇 |
1980年 | 5372篇 |
1979年 | 5671篇 |
1978年 | 5871篇 |
1977年 | 5757篇 |
1976年 | 5837篇 |
1975年 | 5376篇 |
1974年 | 5424篇 |
1973年 | 5566篇 |
1972年 | 3854篇 |
1971年 | 3297篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
A new version of the fast optically pumped magnetometer, an optically pumped balanced quantum magnetometer, built around a pair of symmetric transitions in the hyperfine structure of the 87Rb ground state is implemented for the first time. The noise-limited sensitivity of the prototype in terms of the variance is 6 pT for a measurement time of 0.1 s. The basic advantages of the new magnetometer are the absence of dead zones when it changes orientation relative to the magnetic field and an extremely low sensitivity to the drift of pumping parameters. 相似文献
982.
P. V. Dvornikov 《Russian Physics Journal》2006,49(4):392-401
A standard model Lagrangian is constructed making the pseudo-Finsleroid generalization of the Yang-Mills field equation by
the conformal method. The Higgs field potential is suggested that ensures generation of particle masses caused by the spontaneous
symmetry breaking. After transition to the conformal coordinates, the expressions obtained assume the standard form that in
many cases allows the results of pseudo-Euclidean theory to be used in calculations of the Feynman diagrams.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–51, April, 2006. 相似文献
983.
R. G. Makitra G. G. Midyana E. Ya. Pal’chikova 《Russian Journal of Applied Chemistry》2006,79(1):43-49
The influence of physicochemical properties of organic solvents on the distribution constants of aromatic carboxylic acids between the organic and aqueous phases was examined. 相似文献
984.
T. G. Dzherayan A. V. Rudnev V. P. Morgalyuk 《Russian Journal of Applied Chemistry》2006,79(10):1634-1638
Synthesis of polyhexamethyleneguanidine hydrochloride was studied by capillary electrophoresis. A procedure for determining the reaction components was developed. 相似文献
985.
L. M. Gornostaev E. A. Bocharova N. V. Geets 《Russian Journal of Organic Chemistry》2006,42(9):1289-1292
1,3-Dichloro-2-nitrosobenzene and 1,3-dibromo-5-fluoro-2-nitrosobenzene reacted with amines to give previously unknown nitrosobenzene derivatives containing alkylamino groups in positions 3 and 5. 相似文献
986.
We discuss the spectral lineshapes of reflectance and modulated reflectance (MR) measurements on optoelectronic device structures such as epi-layers, quantum wells (QWs), vertical-cavity surface emitting-lasers (VCSELs) and resonant-cavity light-emitting diodes (RCLEDs). We consider the various methods for the extraction of built-in electric fields and band-gap energies from Franz-Keldysh oscillations (FKO), using the example of a tensilely strained InGaAs QW system, whose InGaAsP barriers yield strong FKO. We describe how critical point transition energies can be easily obtained by eye from Kramers-Kronig (KK) transforms of low field or QW modulation spectra, using the example of the modulated transmittance spectra of dilute-nitrogen InGaAsN p-i-n structures. We also discuss how the ordinary reflectivity spectrum, usually acquired at the same time as the MR signal, may also be exploited to extract layer thicknesses and compositions, and information about the active QW absorption spectrum in VCSEL and RCLED structures. 相似文献
987.
N. Moslemzadeh G. Beamson P. Tsakiropoulos J.F. Watts S.R. Haines P. Weightman 《Journal of Electron Spectroscopy and Related Phenomena》2006
High-energy X-ray photoelectron spectroscopy (XPS) is of particular importance for minimizing the effects of surface contamination by increasing photoelectron escape depths. In this study high-resolution high-energy Cu Kα1 and soft Al Kα1 XPS and Auger electron spectroscopy were used to compare the electronic structure of Ti in TiO2 powder and Ti metal. The Ti 1s in TiO2 XPS line is narrower and more symmetric than in Ti metal. A comparison of the relative intensities of the L23M23M45 and L23M23M23 Auger transitions in Ti metal and TiO2 is consistent with the expected transfer of Ti 3d electrons away from the Ti site in the oxide. The satellites accompanying the Ti 1s XPS line excited by Cu Kα1 X-rays occur at the same energies as the satellites accompanying the Ti 2s and 2p XPS lines excited by Al Kα1 X-rays indicating that they do not depend on the core-level, the experimental resolution or inelastic scattering processes. 相似文献
988.
J.J. Kolodziej B. Such M. Goryl F. Krok P. Piatkowski M. Szymonski 《Applied Surface Science》2006,252(21):7614-7623
Surfaces of several AIIIBV compound semiconductors (InSb, GaAs, InP, InAs) of the (0 0 1) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III-V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination. 相似文献
989.
Mössbauer investigations about iron atom redistribution in oxide films of zirconium alloys subjected to corrosion at 500°C in pure oxygen and water pair have been analysed. The alloys were also subjected to autoclave conditions at a pressure of 10.0 MPa and autoclave conditions at 350°C and at a pressure of 16.8 MPa, using distilled water and water with additives of lithium and fluorine. It is shown that, depending on the corrosion environment, various compounds of iron, such as α-Fe2O3, Fe3O4, and FeO, as solid solutions of iron in ZrO2 are formed in oxide films. 相似文献
990.
The mass spectrum ofcb meson is investigated with an effective quark-antiquark potential of the form -αc/r +Ar
νwith ν varying from 0.5 to 2.0. TheS andP-wave masses, pseudoscalar decay constant, weak decay partial widths in spectator model and the lifetime ofB
cmeson are computed. The properties calculated here are found to be in good agreement with other theoretical and experimental
values at potential index,ν = 1 相似文献