全文获取类型
收费全文 | 1370篇 |
免费 | 36篇 |
专业分类
化学 | 658篇 |
晶体学 | 16篇 |
力学 | 25篇 |
数学 | 206篇 |
物理学 | 501篇 |
出版年
2020年 | 18篇 |
2019年 | 18篇 |
2016年 | 61篇 |
2015年 | 47篇 |
2014年 | 51篇 |
2013年 | 132篇 |
2012年 | 38篇 |
2011年 | 15篇 |
2010年 | 35篇 |
2009年 | 34篇 |
2008年 | 28篇 |
2007年 | 22篇 |
2006年 | 37篇 |
2003年 | 13篇 |
2002年 | 30篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 27篇 |
1997年 | 20篇 |
1996年 | 20篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 17篇 |
1992年 | 28篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 19篇 |
1984年 | 21篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 20篇 |
1978年 | 23篇 |
1977年 | 17篇 |
1976年 | 21篇 |
1975年 | 24篇 |
1974年 | 25篇 |
1973年 | 14篇 |
1972年 | 15篇 |
1970年 | 14篇 |
1969年 | 18篇 |
1968年 | 12篇 |
1966年 | 24篇 |
1965年 | 14篇 |
1961年 | 16篇 |
排序方式: 共有1406条查询结果,搜索用时 31 毫秒
91.
92.
93.
J. Burget M. Odehnal V. PetŘíček J. šácha L. Trlifaj 《Czechoslovak Journal of Physics》1961,11(10):719-728
The observation of double quantum transitions on three kinds of free radicals (DPPH, DPANO, ultramarine) at temperatures of liquid nitrogen is described. Signals having an absorption and emission character were observed in the 12-5 MHz–18 MHz frequency band in the direction parallel to the external magnetic fieldH
0 and their dependence on different parameters was studied.Bloch equations were solved for two mutually perpendicular high-frequency fields and expressions were found for the components of dynamic susceptibility in theH
0 direction. The experiments agree with theory.The possibility of using double quantum transitions for measuring relaxation times is discussed.
(DPPH, DPANO, ) . 12,5MHz–18MHz H 0, ; . H 0. . .相似文献
94.
The influence of X-ray irradiation and the following bleaching on microhardness and dislocation mobility was investigated. It was found that dislocations were pinned in irradiated samples and the pinning was not destroyed by illumination. The microhardness, increased by irradiation, increased still further by bleaching. 相似文献
95.
96.
Formation of the plasma potential in a plasma that contains energetic electrons and is bounded by a floating collector that
emits electrons is studied theoretically. The problem is treated by a static. kinetic plasma-sheath model of Schwager and
Birdsall [Phys. Fluids B2 (1990) 1057], which we have extended in order to include additional energetic electron population. The distribution of these
electrons is assumed to be a high-temperature Maxwellian. They are called hot electrons. In the paper we study effects of
the density and temperature of the hot electrons on the formation of the plasma potential. The model shows that for certain
densities and temperatures of the hot electron population plasmas with two different plasma potentials can coexist in the
system. These two plasmas are separated spatially by a double layer. For the case when there is no emission of electrons from
the collector, results of the model are compared with computer simulation and very good agreement between the model and the
simulation is found. The simulation also confirms existence of two plasmas with two different potentials separated by a double
layer. 相似文献
97.
Considering the Markov binomial distribution, we study large deviations for the Poisson approximation. Apart from the standard choice of parameters, we use the approach where the parameter of approximation depends on the argument of the approximated distribution function. 相似文献
98.
It is well known that in the non-depleted pump approximation, the efficiency of a second harmonic generation (SHG) of a guided mode in a non-linear optical waveguide increases quadratically with the interaction length (P
2 L
2), and linearly (P
2 L) in the erenkov regime. The efficiency of the erenkov SHG in the waveguide with a non-linear substrate and linear guiding layer is known to be strongly peaked at a particular pump wavelength and a particular waveguide thickness, with the erenkov angle approaching zero. The known theory predicts an infinite efficiency value at the peak, however. In this contribution, a simple integral expression for the SHG efficiency in the erenkov regime is derived. For large erenkov angles and interaction lengths it yields the expected P
2 L dependence, while in the limit of small erenkov angles the dependence is found to have the form of P L
3/2, possessing also a finite value at the efficiency peak. The condition determining the accurate position of the efficiency peak in the waveguide thickness–pump wavelength plane is given, too. 相似文献
99.
Alexander Čeklovský Juraj Bujdák Adriana Czímerová Nobuo Iyi 《Central European Journal of Physics》2007,5(2):236-243
Tetracationic porphyrin dyes TMPyP and ZnPyP were intercalated into hydrophobized layered silicate films of three smectites.
The smectites represented the layered silicate specimens of high (Fluorohectorite, Corning; FHT), medium (Kunipia F montmorillonite;
KF) and low layer charge (Laponite, Laporte; LAP). The molecular orientations of the dye cations were studied by means of
linearly-polarized ultraviolet-visible (UV-VIS) spectroscopy. The spectral analysis and consequent calculations of tilting
angles of the transition moments at the wavelengths of Soret band transitions were in the range of 25°-35°. The determined
angles indicated molecular orientation of the dye cations being almost parallel to the surface of the silicates. Slightly
higher values (above 35°), determined for a FHT film, indicated either a slightly tilted orientation of the dye cations or
the change of molecular comformation after the intercalation of the dye.
Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia 相似文献
100.
Laila Čakare Marija Kosec Barbara Malič 《Journal of Sol-Gel Science and Technology》2000,19(1-3):603-606
PbZrO3 (PZ) thin films have been prepared by 2-methoxyethanol route from lead oxide or lead acetate and zirconium n-butoxide. The use of lead oxide as lead source and the seeding layer of TiO2 on Pt/TiO2/SiO2/Si substrate facilitate the formation of the perovskite phase. 相似文献