全文获取类型
收费全文 | 18803篇 |
免费 | 3331篇 |
国内免费 | 1167篇 |
专业分类
化学 | 7585篇 |
晶体学 | 79篇 |
力学 | 2784篇 |
综合类 | 228篇 |
数学 | 2651篇 |
物理学 | 9974篇 |
出版年
2024年 | 52篇 |
2023年 | 208篇 |
2022年 | 492篇 |
2021年 | 581篇 |
2020年 | 627篇 |
2019年 | 531篇 |
2018年 | 475篇 |
2017年 | 698篇 |
2016年 | 749篇 |
2015年 | 702篇 |
2014年 | 1130篇 |
2013年 | 1228篇 |
2012年 | 1211篇 |
2011年 | 1246篇 |
2010年 | 1064篇 |
2009年 | 1158篇 |
2008年 | 1185篇 |
2007年 | 1194篇 |
2006年 | 1082篇 |
2005年 | 1072篇 |
2004年 | 980篇 |
2003年 | 789篇 |
2002年 | 611篇 |
2001年 | 533篇 |
2000年 | 484篇 |
1999年 | 407篇 |
1998年 | 375篇 |
1997年 | 333篇 |
1996年 | 273篇 |
1995年 | 273篇 |
1994年 | 188篇 |
1993年 | 205篇 |
1992年 | 177篇 |
1991年 | 153篇 |
1990年 | 134篇 |
1989年 | 124篇 |
1988年 | 117篇 |
1987年 | 95篇 |
1986年 | 56篇 |
1985年 | 60篇 |
1984年 | 52篇 |
1983年 | 29篇 |
1982年 | 60篇 |
1981年 | 33篇 |
1980年 | 19篇 |
1979年 | 22篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1973年 | 7篇 |
1971年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
We consider some types of packet discretization for continuous spectra in quantum scattering problems. As we previously showed, this discretization leads to a convenient finite-dimensional (i.e., matrix) approximation for integral operators in the scattering theory and allows reducing the solution of singular integral equations connected with the scattering theory to some suitable purely algebraic equations on an analytic basis. All singularities are explicitly singled out. Our primary emphasis is on realizing the method practically. 相似文献
63.
S. Schrader A. Penzkofer W. Holzer R. Velagapudi B. Grimm 《Journal of luminescence》2004,110(4):303-308
Optical, structural and morphological properties of thin films of polyparaphenylenevinylene (PPV) formed by an alkyl sulfinyl precursor route have been studied. Thin films were fabricated on an optical glass and on quartz glass either by spin-coating of the precursor solution or by layer-by-layer deposition using Langmuir–Blodgett technique. PPV precursor films were also spin-coated on gold-coated glass in order to study thin-film optical parameters by surface plasmon spectroscopy. We have been successful in forming about 40 precursor mono layers on quartz glass by Langmuir–Blodgett technique using optimized surface pressure and dipping conditions. After thermal conversion of the precursor layers good quality fluorescent PPV films of yellow colour have been obtained. Optical characterization of the films was carried out by linear absorption and emission spectroscopy, ellipsometry, and surface plasmon spectroscopy. Structural and morphological studies on the thin films were carried out by using X-ray scattering and atomic force microscopy. Wave-guided travelling-wave laser action has been achieved in a PPV film on quartz glass. The sample was transversally pumped with picosecond laser pulses (wavelength 347.15 nm, duration 35 ps). Laser emission occurred at 550 nm for pump pulse energy densities above . 相似文献
64.
Othman Belhadj Miled David Grosso Jacques Livage 《Journal of Physics and Chemistry of Solids》2004,65(10):1751-1755
This paper describes the synthesis and optical pH sensing properties of a pH indicator dye activated mesostructured silica coated optical fibre. The pH-sensitive dye bromothymol blue was incorporated into the mesostructure sol precursor and thin films/coatings were used for pH-sensing applications without prior removal of the surfactant. The pH sensitivity range and operating wavelength were analysed by absorption measurements on layer dip-coated on glass slides. The pH sensing properties of coated optical fibre were tested by evanescent wave method. Experiments were carried out by using a series of solutions of known pH. No leaching was observed (except at very high pH) and an excellent reversibility was obtained between pH=2 and 5. 相似文献
65.
66.
67.
Yang Ruike Wu Zhensen You Jinguang 《International Journal of Infrared and Millimeter Waves》2003,24(8):1383-1392
The influence of sand and dust storms on modern MMW and satellite communication systems reliability have been paid more attention to. The attenuations induced by sand and dust storms are estimated by means of Mie-theory and Rayleigh approximation, in the case of the tenuous distribution of particles. With the particle density increasing, however, these method become inadequate, the multiple scattering effects then become dominant for attenuation estimation. The attenuations considering multiple scattering effects are estimated by Monte-Carlo and four fluxes method at horizontal paths. At slant paths, based on multi-layer media model, the attenuations considering multiple scattering effects are calculated by layered Monte-Carlo method at 100, 37, 24, and 14GHz. It is shown that the multiple scattering effects should be considered at the attenuation prediction in the sand and dust storm, which the visibility is about 0.5km and smaller than 0.5km and frequency is about 20GHz. Above 30GHz, the multiple scattering effects due to sand and dust particles should be considered, as visibility is about 1km and smaller than 1km at slant paths. 相似文献
68.
69.
I. Longo D. Cros N. Tosoratti 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):273-277
We present a numerical and experimental characterization of high-Q whispering gallery resonant modes excited in a fused quartz spherical shell operated in the 18-26.5 GHz band; easy coupling
and selection of modes is a most advantageous feature of the proposed structure with respect to ordinary bulk resonators.
The numerical results, based on a finite element algorithm, well match experimental data, which also show the capability of
our device to perform gaseous spectroscopy measurements.
Received 25 October 2002 Published online 4 February 2003 相似文献
70.