全文获取类型
收费全文 | 6629篇 |
免费 | 128篇 |
国内免费 | 20篇 |
专业分类
化学 | 3941篇 |
晶体学 | 15篇 |
力学 | 138篇 |
综合类 | 1篇 |
数学 | 831篇 |
物理学 | 1851篇 |
出版年
2021年 | 52篇 |
2020年 | 72篇 |
2019年 | 71篇 |
2018年 | 67篇 |
2016年 | 108篇 |
2015年 | 80篇 |
2014年 | 95篇 |
2013年 | 173篇 |
2012年 | 200篇 |
2011年 | 256篇 |
2010年 | 155篇 |
2009年 | 140篇 |
2008年 | 223篇 |
2007年 | 270篇 |
2006年 | 253篇 |
2005年 | 255篇 |
2004年 | 231篇 |
2003年 | 203篇 |
2002年 | 161篇 |
2001年 | 137篇 |
2000年 | 119篇 |
1999年 | 117篇 |
1998年 | 92篇 |
1997年 | 93篇 |
1996年 | 109篇 |
1995年 | 112篇 |
1994年 | 118篇 |
1993年 | 106篇 |
1992年 | 134篇 |
1991年 | 83篇 |
1990年 | 77篇 |
1989年 | 66篇 |
1988年 | 79篇 |
1987年 | 76篇 |
1986年 | 73篇 |
1985年 | 89篇 |
1984年 | 80篇 |
1983年 | 62篇 |
1982年 | 79篇 |
1981年 | 66篇 |
1980年 | 57篇 |
1979年 | 60篇 |
1978年 | 61篇 |
1977年 | 59篇 |
1976年 | 49篇 |
1975年 | 53篇 |
1974年 | 53篇 |
1973年 | 64篇 |
1971年 | 42篇 |
1969年 | 35篇 |
排序方式: 共有6777条查询结果,搜索用时 15 毫秒
61.
A. Roberts M. L. von Bibra H-P. Gemünd E. Kreysa 《International Journal of Infrared and Millimeter Waves》1994,15(3):505-517
In this paper a comparison between a rigorous electromagnetic model for transmission through a hexagonal array of circular waveguides in a series of thick, metallic screens and experimental measurements in the far infrared is made. It is found that there is excellent agreement between theory and experiment when the frequency is below that where any diffracted orders propagate. The agreement is still very good above this frequency. Below a frequency approximately equal to the cut-off frequency of the circular waveguides little power is transmitted. As the thickness of the screen is increased, this decrease in transmission becomes more abrupt. Also, for thick screens, resonances appear in the transmission spectrum which are analogous to those which appear in the spectra of two grids separated by a distance comparable to the wavelength of the radiation being used. 相似文献
62.
Prof. Guido Barone Prof. Aldo La Ginestra 《Journal of Thermal Analysis and Calorimetry》1992,38(12):2563-2563
63.
We investigated the photoluminescence (PL) properties of carbon nitride films (CNx) deposited by rf magnetron sputtering and compared them to their microstructure depending on the target self-bias. While many of the data are compatible with ‘a-C:H like’ PL properties the observed variation of the PL efficiency η with respect to the target bias cannot be easily explained by the standard models. It is suggested that the observed variation of η is rather dominated by a change in microstructure which depends on the bombardment intensity during growth than by the concentration of non-radiative centres. 相似文献
64.
Y. Akiyama P. von Brentano A. Gelberg 《Zeitschrift für Physik A Hadrons and Nuclei》1987,326(4):517-521
Energies of collective levels in178Hf and234U are compared with predictions of theSU (3) limit of thesdg Interacting Boson Model. All known positive parity states of178Hf below 1.8 MeV (with the exception of a 0+ band) have been satisfactorily reproduced. Most of the bands in234U are also described by the model. However, a few predicted states have no experimental counterpart. The introduction of theg-bosons strongly reduces the previously observed discrepancies between experimentalB(E2)'s in238U and thesd-IBM calculation. 相似文献
65.
H. Günther M. Foerste M. Kunze G. zu Putlitz U. von Stein 《Zeitschrift für Physik B Condensed Matter》1996,100(4):613-617
We review the previous conclusion [J.Y. Ryu, Y.C. Chung and S.D. Choi, Phys. Rev. B 32, 7769 (1984)] that the trace property Tr(ABC) = Tr(CAB) leads to two different cyclotron transition absorption formulae in the electron-phonon systems in the lowest order approximation. The pictorial expression and the calculated linewidths in Ge and Si show that the socalled EWC scheme is more seeming than the socalled MWC scheme. The difference is expected to disappear if we take into account all the higher order perturbation terms or start with the many body formalism in the complete scheme. 相似文献
66.
67.
68.
69.
A. Vanelstraete C. Laermans L. Lejarraga M. von Schickfus S. Hunklinger 《Zeitschrift für Physik B Condensed Matter》1988,70(1):19-23
The internal friction of two neutron-irradiated quartz samples was measured at audio-frequency as a function of temperature. This is an extension of acoustic measurements to much lower frequencies and thus to much longer time scales. A temperature independent behaviour has been observed and is discussed in the framework of the tunnelling model. One of the major assumptions of this model regarding the tunnelling states with long relaxation time could be verified for neutron-irradiated quartz. 相似文献