全文获取类型
收费全文 | 1066篇 |
免费 | 512篇 |
国内免费 | 117篇 |
专业分类
化学 | 118篇 |
晶体学 | 11篇 |
力学 | 120篇 |
综合类 | 30篇 |
数学 | 111篇 |
物理学 | 1305篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 31篇 |
2021年 | 36篇 |
2020年 | 41篇 |
2019年 | 25篇 |
2018年 | 33篇 |
2017年 | 43篇 |
2016年 | 33篇 |
2015年 | 48篇 |
2014年 | 121篇 |
2013年 | 101篇 |
2012年 | 82篇 |
2011年 | 85篇 |
2010年 | 105篇 |
2009年 | 115篇 |
2008年 | 86篇 |
2007年 | 76篇 |
2006年 | 88篇 |
2005年 | 82篇 |
2004年 | 71篇 |
2003年 | 64篇 |
2002年 | 64篇 |
2001年 | 55篇 |
2000年 | 46篇 |
1999年 | 16篇 |
1998年 | 20篇 |
1997年 | 14篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1976年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1695条查询结果,搜索用时 31 毫秒
61.
We use the improved Faddeev-Jackiw quantization method to quantize the electromagnetic field and its Lagrange multiplier fields. The method's comparison with the usual Faddeev-Jackiw method and the Dirac method is given. We show that this method is equivalent to the Dirac method and also retains all the merits of the usual Faddeev-Jackiw method. Moreover, it is simpler than the usual one if one needs to obtain new secondary constraints. Therefore, the improved Faddeev-Jackiw method is essential. Meanwhile, we find the new meaning of the Lagrange multipliers and explain the Faddeev-Jackiw generalized brackets concerning the Lagrange multipliers. 相似文献
62.
63.
R. Giovanelli 《Il Nuovo Cimento D》1987,9(11):1443-1460
Summary Using the Boris mover, or other standard methods, the error pile-up in the computation of the relativistic orbit of charged
particles in electric and magnetic fields becomes quickly excessive, if one wants to keep reasonably limited the number of
points employed to build the particle orbit. An analytical solution becomes, therefore, desirable and its construction is
the subject of the present work.
Riassunto Unsando il metodo di Boris, oppure altri metodi standard, l'accumulazione degli errori nella determinazione numerica delle orbite relativistiche di particelle cariche in campi elettrici e magnetici diventa intollerabile, se il numero dei punti impiegati per costruire le orbite stesse è mantenuto basso. Una soluzione analitica diviene quindi utile, e questa costituisce l'argomento del presente lavoro.
Резюме В рамках стндартных методов погрешность при вычислении релятивистской орбиты заряженных частиц в электронном и магнитном полях становится чрезмерно большой, если для построения орбиты часицы используется ограниченное число точек. В связи с этим конструируется аналитическое решение.相似文献
64.
The rectangular dielectric waveguide is the most commonly used structure in integrated optics, especially in semi-conductor
diode lasers. Demands for new applications such as high-speed data backplanes in integrated electronics, waveguide filters,
optical multiplexers and optical switches are driving technology toward better materials and processing techniques for planar
waveguide structures. The infinite slab and circular waveguides that we know are not practical for use on a substrate because
the slab waveguide has no lateral confinement and the circular fiber is not compatible with the planar processing technology
being used to make planar structures. The rectangular waveguide is the natural structure. In this review, we have discussed
several analytical methods for analyzing the mode structure of rectangular structures, beginning with a wave analysis based
on the pioneering work of Marcatili. We study three basic techniques with examples to compare their performance levels. These
are the analytical approach developed by Marcatili, the perturbation techniques, which improve on the analytical solutions
and the effective index method with examples.
T Srinivas received the B.Sc. (Hon.) degree from Nehru Science College, Hydrabad and M.E. (Int.) and Ph.D. dgrees from the Indian Institute
of Science, Bangalore, India. He was a Postdoctoral Research Fellow at Toyohashi University of Technology, Japan from 1992
to 1996. He is currently an Associate Professor with the Department of Electrical Communication Engineering, Indian Institute
of Science. His areas of interests are optical communication networks, integrated optics, micro-opto-electrical-mechanical
systems (MOEMS) and fiberoptic sensors 相似文献
65.
圆形面偶极层与圆电流的电磁场 总被引:12,自引:7,他引:5
通过解电场的轴对称边值问题求出了圆形面偶极层的电势分布,使用其结果和类比方法找到了圆电流的磁场分布。 相似文献
66.
67.
Y. K. Hong C. Y. Lee C. K. Jeong J. H. Sim K. Kim J. Joo M. S. Kim J. Y. Lee S. H. Jeong S. W. Byun 《Current Applied Physics》2001,1(6):3492
Through the chemical coating of polypyrrole (PPy) doped with naphthalene sulfonic acid (NSA) on electrically insulating poly (ethylene terephthalate) (PET) woven fabric, PPy–NSA/PET complexes were synthesized. By using the electrochemical coating of PPy doped anthraquinone-2-sulfonic acid (AQSA) on PPy–NSA/PET complexes, PPy–AQSA/PPy–NSA/PET complexes were synthesized. The silver (Ag) was thermally vacuum evaporated on the surface of PPy–AQSA/PPy–NSA/PET complexes (Ag|PPy–AQSA/PPy–NSA/PET). Electromagnetic interference (EMI) shielding efficiency (SE) and dc conductivity (σdc) of fabric complexes were measured for EMI shielding characteristics and theoretical simulation. The measurement of EMI SE in the frequency range from 50 MHz to 1.5 GHz was performed by using ASTM D4935-99 method. The EMI shielding characteristics such as transmittance, reflectance and absorbance were obtained from the S (scattering)-parameter analysis. We control the contribution of the absorbance or the reflectance to total EMI SE through the coating of conductive PPy and the evaporation Ag. 相似文献
68.
69.
A. Ya. Silenko 《Theoretical and Mathematical Physics》2008,156(3):1308-1318
We successively apply the generalized Case-Foldy-Feshbach-Villars (CFFV) and the Foldy-Wouthuysen (FW) transformation to derive
the Hamiltonian for relativistic scalar particles in an electromagnetic field. In contrast to the original transformation,
the generalized CFFV transformation contains an arbitrary parameter and can be performed for massless particles, which allows
solving the problem of massless particles in an electromagnetic field. We show that the form of the Hamiltonian in the FW
representation is independent of the arbitrarily chosen parameter. Compared with the classical Hamiltonian for point particles,
this Hamiltonian contains quantum terms characterizing the quadrupole coupling of moving particles to the electric field and
the electric and mixed polarizabilities. We obtain the quantum mechanical and semiclassical equations of motion of massive
and massless particles in an electromagnetic field.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 156, No. 3, pp. 398–411, September, 2008. 相似文献
70.