全文获取类型
收费全文 | 496294篇 |
免费 | 3979篇 |
国内免费 | 1381篇 |
专业分类
化学 | 242524篇 |
晶体学 | 7509篇 |
力学 | 27112篇 |
综合类 | 18篇 |
数学 | 79561篇 |
物理学 | 144930篇 |
出版年
2020年 | 3598篇 |
2019年 | 4245篇 |
2018年 | 15884篇 |
2017年 | 15731篇 |
2016年 | 14040篇 |
2015年 | 5317篇 |
2014年 | 7929篇 |
2013年 | 17843篇 |
2012年 | 16888篇 |
2011年 | 25967篇 |
2010年 | 17380篇 |
2009年 | 17735篇 |
2008年 | 21334篇 |
2007年 | 23459篇 |
2006年 | 14098篇 |
2005年 | 13645篇 |
2004年 | 13059篇 |
2003年 | 12438篇 |
2002年 | 11414篇 |
2001年 | 11776篇 |
2000年 | 9103篇 |
1999年 | 6952篇 |
1998年 | 6107篇 |
1997年 | 6141篇 |
1996年 | 5736篇 |
1995年 | 5180篇 |
1994年 | 5347篇 |
1993年 | 5048篇 |
1992年 | 5700篇 |
1991年 | 5753篇 |
1990年 | 5606篇 |
1989年 | 5526篇 |
1988年 | 5555篇 |
1987年 | 5437篇 |
1986年 | 5189篇 |
1985年 | 6761篇 |
1984年 | 7099篇 |
1983年 | 5915篇 |
1982年 | 5989篇 |
1981年 | 5913篇 |
1980年 | 5704篇 |
1979年 | 5980篇 |
1978年 | 6265篇 |
1977年 | 6308篇 |
1976年 | 6331篇 |
1975年 | 5878篇 |
1974年 | 5883篇 |
1973年 | 6143篇 |
1972年 | 4440篇 |
1971年 | 3867篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
A. L. Goldenberg V. N. Manuilov M. Yu. Glyavin 《Radiophysics and Quantum Electronics》2005,48(6):461-465
We describe a nonadiabatic electron gun operated in the mode of a currentconfined by spatial charge and intended for producing
helical electron beams for high-power gyroresonantdevices.Results of numerical simulation of electron trajectories and electron-beam
parameters arepresented. It is shown that for a high operating current, the pitch factor and the electronvelocity spread can
be significantly better than in the conventional adiabatic systems.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48,No. 6, pp. 517–522, June 2005 相似文献
992.
993.
994.
The acoustoelectromagnetic interaction is examined in a regime where three mechanisms must be taken into account simultaneously:
photoelasticity, quadratic photoelasticity, and elastic nonlinearity. It is shown that beyond the critical conditions, acoustic
solitary waves are formed at harmonic and subharmonic frequencies in a crystal. Including damping and nonideal reflection
at the boundaries does not lead to the establishment of any sort of stationary state: a soliton spatial-temporal dynamic develops.
Fiz. Tverd. Tela (St. Petersburg) 39, 1101–1104 (June 1997) 相似文献
995.
N. I. Alekseev V. B. Kaplan A. M. Martsinovskii I. I. Stolyarov 《Technical Physics》1997,42(6):599-605
Results are presented from a systematic investigation of the conditions under which anomalously high rates of plasma generation
are observed in the anode region of a low-voltage Knudsen arc in grid plasma switch elements. The phenomenon develops over
a wide range of currents and switched voltages under conditions for which the plasma density in the cathode-grid region is
noticeably higher than the density in the anode region. and its onset is characterized by a pronounced pressure threshold
of ∼2×10−2 Torr. The results are analyzed from the standpoint of the possible mechanisms for anomalous plasma generation — collisional
nonresonance diffusion of electrons in velocity space, leading to enrichment of the distribution function in fast particles,
and the collapse of Langmuir waves in the gap at the high energies of the beam produced when the wires of the grid are bridged
by the quenching pulse and and the current is blocked.
Zh. Tekh. Fiz. 67, 15–21 (June 1997) 相似文献
996.
A. V. Vashkovskii É. G. Lokk V. I. Shcheglov 《Journal of Experimental and Theoretical Physics》1997,84(3):560-568
The propagation of surface and volume magnetostatic waves in unsaturated films of yttrium iron garnet is studied experimentally
for the case when the wavelength greatly exceeds the domain width, while the domain width is comparable to the film thickness.
The characteristics of these waves are examined for symmetric linear, asymmetric linear, and symmetric zigzag strip domain
structures in the films. These characteristics cannot be explained by a theory based on averaging the magnetization over all
the domains.
Zh. éksp. Teor. Fiz. 111, 1016–1031 (March 1997) 相似文献
997.
The yield and energy distributions of potassium and cesium atoms emitted in electron-stimulated desorption (ESD) from a molybdenum
surface, oxidized to different extent and maintained at 300 K, have been measured by the time-of-flight technique with a surface
ionization detector. The ESD threshold for potassium and cesium atoms lies around 25 eV, irrespective of molybdenum oxidation
state. In the case of molybdenum coated by an oxygen monolayer, secondary thresholds at ∼40 and ∼70 eV have been observed,
as well as atomic energy distribution tailing down to very low energies. The most probable kinetic energies of the atoms are
a few tenths of one eV. The results are explained within a model involving Auger neutralization of the adsorbed alkali metal
ions after the filling of the 2s O, 4s Mo, and 4p Mo core holes. The possibility of ESD of a neutral species as a result of oxide-cation core-level ionization has been demonstrated
for the first time.
Fiz. Tverd. Tela (St. Petersburg) 39, 758–761 (April 1997) 相似文献
998.
999.
Structure studies are reported on martensite transformations in porous TiNi alloy made by high-temperatures self-propagating
synthesis. The transformations occur over a large temperature range and are incomplete. The structure data are used in reconstructing
the heat release during the transition, where it is shown that it is determined by the superposition of martensite transformations
occurring locally at various temperatures.
Tomsk State Architectural and Building Academy. Kuznetsov Siberian Technical Physics Institute, Tomsk State University. Translated
from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 20–24, January, 1997. 相似文献
1000.
G. E. Volovik 《JETP Letters》1997,65(7):522-527
The efficiency of conversion of the heat flux into hard x radiation (HXR) is analyzed, via time-dependent two-temperature
one-dimensional non-LTE-radiation-hydrodynamic numerical modeling, for a heat-to-radiation flux converter linked to the edge
of a low-atomic-number hot Z-pinch. The domain of parameters in this scheme is found where about the same HXR yield can be
achieved at values of input energy which are an order of magnitude lower than in the conventional scheme of a radially imploding
plasma.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 7, 502–506 (10 April 1997)
Published in English in the original Russian Journal. Edited by Steve Torstveit. 相似文献