全文获取类型
收费全文 | 334944篇 |
免费 | 2542篇 |
国内免费 | 783篇 |
专业分类
化学 | 175687篇 |
晶体学 | 5130篇 |
力学 | 16307篇 |
综合类 | 17篇 |
数学 | 36170篇 |
物理学 | 104958篇 |
出版年
2020年 | 2945篇 |
2019年 | 3493篇 |
2018年 | 4793篇 |
2017年 | 4775篇 |
2016年 | 6827篇 |
2015年 | 3669篇 |
2014年 | 6291篇 |
2013年 | 14150篇 |
2012年 | 11016篇 |
2011年 | 13411篇 |
2010年 | 10082篇 |
2009年 | 10267篇 |
2008年 | 12524篇 |
2007年 | 12539篇 |
2006年 | 11341篇 |
2005年 | 10232篇 |
2004年 | 9402篇 |
2003年 | 8430篇 |
2002年 | 8487篇 |
2001年 | 9285篇 |
2000年 | 7010篇 |
1999年 | 5402篇 |
1998年 | 4645篇 |
1997年 | 4632篇 |
1996年 | 4279篇 |
1995年 | 3908篇 |
1994年 | 3969篇 |
1993年 | 3724篇 |
1992年 | 4277篇 |
1991年 | 4476篇 |
1990年 | 4234篇 |
1989年 | 4270篇 |
1988年 | 4146篇 |
1987年 | 4094篇 |
1986年 | 3856篇 |
1985年 | 4986篇 |
1984年 | 5180篇 |
1983年 | 4299篇 |
1982年 | 4407篇 |
1981年 | 4266篇 |
1980年 | 3999篇 |
1979年 | 4473篇 |
1978年 | 4635篇 |
1977年 | 4672篇 |
1976年 | 4691篇 |
1975年 | 4428篇 |
1974年 | 4413篇 |
1973年 | 4498篇 |
1972年 | 3254篇 |
1971年 | 2960篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
T. Gleisberg F. Krauss C. G. Papadopoulos A. Schälicke S. Schumann 《The European Physical Journal C - Particles and Fields》2004,34(2):173-180
In this paper total cross sections for signals and backgrounds of top- and Higgs-production channels in e + e- collisions at a future linear collider are presented. All channels considered are characterized by the emergence of six-particle final states. The calculation takes into account the full set of tree-level amplitudes in each process. Two multi-purpose parton level generators, HELAC/PHEGAS and AMEGIC + + , are used, and their results are found to be in perfect agreement.Received: 26 November 2003, Revised: 15 January 2004, Published online: 3 March 2004 相似文献
982.
E. N. Dancer 《Journal of Fixed Point Theory and Applications》2007,1(1):47-60
We discuss the calculation of homotopy indices on closed convex sets in a Banach space and then use these ideas to prove the
existence of multiple solutions of nonlinear elliptic equations. We obtain more information on the solutions than in earlier
work. A key idea is to calculate the homotopy index of the stable and mountain pass solutions and the connections joining
them.
Dedicated to the memory of Jean Leray 相似文献
983.
S. A. Klimin M. N. Popova E. P. Chukalina B. Z. Malkin A. R. Zakirov E. Antic-Fidancev Ph. Goldner P. Aschehoug G. Dhalenne 《Physics of the Solid State》2005,47(8):1425-1430
The absorption spectra of Yb2Ti2O7 single crystals and the luminescence and luminescence excitation spectra of Y2Ti2O7: Yb (1%) polycrystals were studied in the temperature range 4.2–300 K. The spectra were analyzed in terms of the crystal-field
theory and the exchange-charge model. Based on the set of crystal-field parameters found for Yb2Ti2O7, analogous sets of parameters were determined for other rare-earth titanates and proved to be in reasonable agreement with
all available experimental data.
__________
Translated from Fizika Tverdogo Tela, Vol. 47, No. 8, 2005, pp. 1376–1380.
Original Russian Text Copyright ? 2005 by Klimin, Popova, Chukalina, Malkin, Zakirov, Antic-Fidancev, Goldner, Aschehoug,
Dhalenne. 相似文献
984.
985.
Measures of complexity for 3D image analysis of trabecular
bone 总被引:1,自引:0,他引:1
Based on fractal properties and spatial auto-correlation, the
measures of complexity lacunarity, Moran's I and Geary's C index
are defined for 3D image analysis. Their abilities to investigate
translational invariance, characteristic length scales, spatial
correlation and shapes of 3D micro-structures are demonstrated on
proto-typical examples. Finally, using these measures of complexity,
3D images of trabecular bone are analysed. The main findings are
that the complexity of the trabecular structure decreases and the
plate-like shapes of the trabeculae change to mainly rod-like shapes
during bone loss. These results and the proposed measures could have
a great impact for medicine and for space exploration. 相似文献
986.
N. A. Smirnova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(10):1608-1616
The directions of the studies of aqueous solutions containing two surfactants or surfactants and various additives performed by the authors and coworkers are discussed, with the focus being on systems in which mixing is accompanied by synergistic effects (a significant decrease in the critical micelle concentration, the growth of aggregates, an increase in the viscosity, changes in the topology of the solubility diagram, etc.). Experimental data and results of modeling with the use of molecular-thermodynamic approaches of various levels are presented. 相似文献
987.
Montecchi M. Nichelatti E. Montereali R.M. Piccinini M. Somma F. 《Optical and Quantum Electronics》2004,36(1-3):43-56
An analytical expression of the complex permittivity is derived for absorbing centres featuring inhomogeneous absorption-line broadening. Such an expression gives the dispersion law of the real part of the permittivity when the imaginary part has a Gaussian lineshape. Our mathematical approach starts from an overlap integral of Lorentzian-type dielectric susceptibilities weighted by a Gaussian probability distribution of the resonance absorption energies. The analytical solution found is consistent with the Kramers–Kronig relation. We demonstrate that, like in the case of homogeneous absorption-line broadening, the refractive index increases at photon energies lower than the resonance absorption energy also for inhomogeneous absorption-line broadening; if the absorbing centres emit Stokes-shifted radiation, such an increase can be exploited for passive and active waveguiding applications. An example is reported regarding active waveguides based on colour centres in a lithium fluoride crystal. 相似文献
988.
The forces acting on interacting moving atoms exposed to resonant laser radiation are calculated. It is shown that the forces acting on the atoms include the radiation pressure forces as well as the external and internal bias forces. The dependences of the forces on the atomic spacing, polarization, and laser radiation frequency are given. It is found that the internal bias force associated with the interaction of atomic dipoles via the reemitted field may play an important role in the dynamics of dense atomic ensembles in a light field. It is shown that optical size resonances appear in the system of interacting atoms at frequencies differing substantially from transition frequencies in the spectrum of atoms. It is noted that optical size resonances as well as the Doppler frequency shift in the spectrum of interacting atoms play a significant role in the processes of laser-radiation-controlled motion of the atoms. 相似文献
989.
Ya. I. Korenman N. N. Popova T. A. Kuchmenko 《Russian Journal of Applied Chemistry》2007,80(6):955-959
The quantitative and kinetic parameters of sorption of formic and acetic acids on thin films of various modifiers of piezoelectric quartz resonator electrodes are determined. Parameters of film formation on the electrodes (application procedure and thickness) are optimized. Methods for joint and separate determination of formic and acetic acids in air by piezoelectric microweighing with single- and double-sensor devices are developed. 相似文献
990.
M.D. Williams S.C. Williams S.A. Yasharahla N. Jallow 《Applied Surface Science》2007,253(20):8568-8570
Ultraviolet photoemission spectroscopy is used to study the kinetics of the H-Zn complex deactivation in Zn doped InP(1 0 0). Hydrogen injected into the material electronically passivates the local carrier concentration. Reverse-biased anneals of the InP under ultra-high vacuum show a dramatic change in the work function of the material with increasing temperature. Spectral features are also shown to be sensitive to sample temperature. To our knowledge, we show the first view of hydrogen retrapping at the surface using photoemission spectroscopy. A simple photoelectron threshold energy analysis shows the state of charge compensation of the material. 相似文献