全文获取类型
收费全文 | 1466篇 |
免费 | 551篇 |
国内免费 | 86篇 |
专业分类
化学 | 113篇 |
晶体学 | 2篇 |
力学 | 190篇 |
综合类 | 16篇 |
数学 | 138篇 |
物理学 | 1644篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 26篇 |
2020年 | 28篇 |
2019年 | 23篇 |
2018年 | 33篇 |
2017年 | 49篇 |
2016年 | 67篇 |
2015年 | 68篇 |
2014年 | 103篇 |
2013年 | 129篇 |
2012年 | 109篇 |
2011年 | 116篇 |
2010年 | 122篇 |
2009年 | 122篇 |
2008年 | 144篇 |
2007年 | 127篇 |
2006年 | 98篇 |
2005年 | 106篇 |
2004年 | 64篇 |
2003年 | 89篇 |
2002年 | 82篇 |
2001年 | 57篇 |
2000年 | 50篇 |
1999年 | 37篇 |
1998年 | 31篇 |
1997年 | 25篇 |
1996年 | 29篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有2103条查询结果,搜索用时 15 毫秒
91.
Paul Bracken 《Central European Journal of Physics》2008,6(1):135-140
An effective Hamiltonian for the generalized harmonic oscillator is determined by using squeezed state wavefunctions. The
equations of motion over an extended phase space are determined and then solved perturbatively for a specific choice of the
oscillator parameters. These results are used to calculate the dynamic and geometric phases for the generalized oscillator
with this choice of parameters.
相似文献
92.
In this paper a new ring-shaped harmonic oscillator for spin 1/2 particles is studied, and the corresponding eigenfunctions and eigenenergies are obtained by solving the Dirac equation with equal mixture of vector and scalar potentials. Several particular cases such as the ring-shaped non-spherical harmonic oscillator, the ring-shaped harmonic oscillator, non-spherical harmonic oscillator, and spherical harmonic oscillator are also discussed. 相似文献
93.
94.
95.
Abdullah Algin 《Czechoslovak Journal of Physics》2002,52(9):1011-1019
A two-parameter deformed N = 2 SUSY algebra is constructed by using the q-deformed bosonic and fermionic Newton oscillator algebras. The Fock space representation of the (q
1,q
2)-deformed N = 2 SUSY algebra is analyzed. The comparison between the algebra constructed and earlier versions of deformed N = 2 SUSY algebras is also made. 相似文献
96.
设计了紧凑型L波段同轴相对论返波振荡器,通过粒子模拟研究了L波段同轴相对论返波振荡器相互作用的物理过程,并对器件的电磁结构进行了优化和改进。分析表明,采用同轴慢波结构可以在较低的外加磁场下实现L波段返波振荡器的微波输出,同时可以大大减小微波器件的径向尺寸。这是因为同轴慢波结构的TM01模式有类似于TEM模的性质,没有截止频率,但纵向电场不为零,电子束能够与它发生强相互作用过程。粒子模拟优化结果表明,在器件半径仅为4.0 cm,电子束能量240 keV,电子束流1.8 kA,导引磁场仅为0.75 T时,返波振荡器可以在频率1.60 GHz处获得较大功率的微波输出, 平均峰值功率达140 MW,平均峰值功率效率约为32%。 相似文献
97.
提出了一种新结构的高功率径向强流速调管振荡器,该器件利用折叠式同轴谐振腔的微波场与接近空间电荷限制电流的径向电子束强烈相互作用产生高功率微波。首先对这种器件的实现机理进行了初步的分析,提出了有间隙电压情况时的径向同轴间隙的空间电荷限制电流1维近似估计模型。分析表明:对于电子束直流接近但小于直流空间限制电流的径向速调管,当有调制间隙电压时,空间限制电流要小于无调制间隙电压情况下的直流空间限制电流,径向强流电子束电流接近和超过空间电荷限制电流时会出现强烈的调制。然后用PIC程序对其特性进行了粒子模拟,在二极管输入电压500 kV、电子束电流为30 kA条件下,最终得到了峰值功率6 GW、频率1.3 GHz的微波输出。 相似文献
98.
J. Grenzer A. A. Ignatov E. Schomburg K. F. Renk D. G. Pavel'ev Yu. Koschurinov B. Melzer S. Ivanov S. Schaposchnikov P. S. Kop'ev 《Annalen der Physik》1995,507(3):184-190
We report on a microwave oscillator based on Bloch oscillations of electrons in a semiconductor superlattice. Our GaAs/AlAs superlattice, at room temperature, was coupled electromagnetically by an antenna to a rectangular cavity resonator, and was operated at a current-voltage state of negative differential conductance. We observed generation of microwave radiation at frequencies, depending on the resonator length, between 7 and 30 GHz. Electronic tuning by several percent was possible; the ratio of linewidth to frequency was of the order of 10?4. A radiation power up to 1 μW (at 10 GHz) was obtained, corresponding to a generator efficiency of the order of 10?3 for the conversion of electrical power to microwave radiation. 相似文献
99.
Chunfeng?WuEmail author Kang?Xue 《International Journal of Theoretical Physics》2004,43(12):2395-2403
We investigate the realizations of Yangian algebra for a Dirac oscillator. Applying the representation theory of Y(sl(2)) to Dirac oscillator, shift operaors for different energy levelsfor this system are obtained. 相似文献
100.
Yu. Satov B. Sharkov Yu. Smakovski K. Makarov A. Stepanov V. Roerich S. Kondrashev A. Shumshurov A. Balabaev 《Journal of Russian Laser Research》2004,25(6):524-534
A set-up of the CO2 SKATE and its output characteristics are described. The system is based on a self-sustained gas discharge module with x-ray preionization that ensures reliability and stable repetition rate operation at 1 Hz for a long time. Measurement of the initial electron density in the discharge volume produced by an x-ray gun is presented for different gases and their mixtures, which is of independent interest for some applications of x-ray preionization. Data on measurements of the low-intensity signal gain and laser parameters for a free-running generator configuration are presented as well as long-term operation characteristics. This laser system has been used as a CO2 generator with gigawatt peak intensity and high spatial–temporal characteristics. In particular, the laser can be used as a driver for a source of multicharged ions in contrast to the laboratory prototypes previously investigated. 相似文献