全文获取类型
收费全文 | 497585篇 |
免费 | 5400篇 |
国内免费 | 2182篇 |
专业分类
化学 | 258616篇 |
晶体学 | 7637篇 |
力学 | 22851篇 |
综合类 | 68篇 |
数学 | 60101篇 |
物理学 | 155894篇 |
出版年
2021年 | 4185篇 |
2020年 | 4641篇 |
2019年 | 5101篇 |
2018年 | 6908篇 |
2017年 | 7091篇 |
2016年 | 9931篇 |
2015年 | 5993篇 |
2014年 | 9532篇 |
2013年 | 22631篇 |
2012年 | 18109篇 |
2011年 | 21744篇 |
2010年 | 15971篇 |
2009年 | 15695篇 |
2008年 | 19846篇 |
2007年 | 19851篇 |
2006年 | 18434篇 |
2005年 | 16337篇 |
2004年 | 14944篇 |
2003年 | 13235篇 |
2002年 | 13112篇 |
2001年 | 15113篇 |
2000年 | 11317篇 |
1999年 | 8689篇 |
1998年 | 7275篇 |
1997年 | 7078篇 |
1996年 | 6801篇 |
1995年 | 5905篇 |
1994年 | 5946篇 |
1993年 | 5710篇 |
1992年 | 6312篇 |
1991年 | 6498篇 |
1990年 | 6149篇 |
1989年 | 6016篇 |
1988年 | 5743篇 |
1987年 | 5787篇 |
1986年 | 5604篇 |
1985年 | 7208篇 |
1984年 | 7329篇 |
1983年 | 6100篇 |
1982年 | 6339篇 |
1981年 | 5919篇 |
1980年 | 5729篇 |
1979年 | 6119篇 |
1978年 | 6279篇 |
1977年 | 6298篇 |
1976年 | 6297篇 |
1975年 | 5883篇 |
1974年 | 5928篇 |
1973年 | 6038篇 |
1972年 | 4483篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
The influence of additives such as TiO2, Al2O3 and their mechanical mixture as well as aluminium oxide, the surface of which contains phosphorous and titanium-oxide nanostructures, on the combustibility of foam plast (trade mark PEN-I), produced on the basis of epoxide novolak block-copolymers, was studied. It was stated that the incorporation both phosphorous-containing and titanium-containing oxides in the composition results in significant (in two to five times) decreasing of the samples’ combustibility. The probable mechanism of inhibition of burning process for those combustion retarders was discussed. 相似文献
982.
983.
984.
985.
986.
987.
988.
S. M. Arabei D. V. Novik T. A. Pavich K. N. Solov’ev 《Journal of Applied Spectroscopy》2006,73(4):511-521
We have studied the fluorescence and fluorescence excitation spectra at 300 K, 77 K, and 4.2 K for silicate gel matrices colored
with meso-tetrapropylporphin by impregnation of the matrix with a solution of the pigment. Comparison of the data obtained
with the absorption spectra in acidified solutions and analysis of the low-temperature fine-structure vibronic spectra, and
also taking into account data obtained earlier for octaethylporphin in a xerogel showed formation of two cationic forms of
meso-tetrapropylporphin in the gel matrix: the short-wavelength form has a dicationic structure, while the long-wavelength form
has a monocationic structure. We have traced out the correlations of the vibrational structure in the spectra of the dicationic
form with data for the porphin dication, and we have drawn a number of conclusions concerning the normal vibrational modes
that are active in the vibronic fluorescence and absorption spectra of the studied cationic forms. Using the AM1 semiempirical
quantum chemical method, we optimized the geometry of the mesotetrapropylporphin dication: the most stable of the possible
conformers is the dication structure with saddleshaped macrocycle nonplanarity.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 453–461, July–August, 2006. 相似文献
989.
Oleg S. Ugolnikov Igor A. Maslov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,102(3):499-512
The work is devoted to the analysis of the surface photometric observations of two total lunar eclipses in 2004. The lunar surface relative brightness distribution inside the umbra was used to retrieve the vertical distribution of aerosol extinction of the solar radiation expanding by a tangent path and its dependence on the location at the limb of the Earth. The upper altitude of troposphere aerosol layer was estimated for different latitude zones. The correlation between additional aerosol extinction in the upper troposphere and cyclones was investigated. 相似文献
990.
Ion synthesis and laser annealing of Cu nanoparticles in Al2O3 总被引:1,自引:0,他引:1
A.L. Stepanov V.N. Popok D.E. Hole I.B. Khaibullin 《Applied Physics A: Materials Science & Processing》2002,74(3):441-446
Al2O3 samples with Cu nanoparticles, synthesised by ion implantation at 40 keV with a dose of 1×1017 ion/cm2 and a current density from 2.5 to 12.5 μA/cm2, were annealed using ten pulses from a KrF excimer laser with a single pulse fluence of 0.3 J/cm2. The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment
were studied by Rutherford backscattering (RBS), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM) and
optical spectroscopy. It was found that laser annealing leads to a reduction in the nanoparticle size without diffusion of
metal atoms into the bulk. The change in particle size and the possibility for oxidation of the copper particles are examined
in the framework of Mie theory. Calculations presented show that under excimer laser treatment, Cu nanoparticles are more
likely to be reduced in size than to undergo oxidation.
Received: 19 April 2001 / Accepted: 7 November 2001 / Published online: 23 January 2002 相似文献