全文获取类型
收费全文 | 485篇 |
免费 | 130篇 |
国内免费 | 65篇 |
专业分类
化学 | 225篇 |
晶体学 | 13篇 |
力学 | 10篇 |
综合类 | 13篇 |
数学 | 13篇 |
物理学 | 406篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 8篇 |
2020年 | 28篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 21篇 |
2016年 | 23篇 |
2015年 | 14篇 |
2014年 | 31篇 |
2013年 | 49篇 |
2012年 | 27篇 |
2011年 | 21篇 |
2010年 | 32篇 |
2009年 | 28篇 |
2008年 | 23篇 |
2007年 | 32篇 |
2006年 | 28篇 |
2005年 | 24篇 |
2004年 | 28篇 |
2003年 | 21篇 |
2002年 | 23篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 26篇 |
1998年 | 28篇 |
1997年 | 17篇 |
1996年 | 19篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有680条查询结果,搜索用时 46 毫秒
1.
2.
I. A. Anoshko V. S. Ermachenko L. E. Sandrigailo 《Journal of Applied Spectroscopy》2007,74(1):102-106
We present the results of a spectroscopic study of a nonequilibrium plasma in a Hall accelerator, in particular for such an
important parameter as the electron temperature. For the studied conditions, we used the semicoronal equilibrium model, which
relates the intensity ratios for two successive ionization steps for the same element.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 93–96, January–February, 2007. 相似文献
3.
4.
X.X. Guo 《Surface science》2004,549(3):211-216
We studied parallel conductivities of pure BaF2 films with thicknesses ranging from 35 to 300 nm, epitaxially grown on Al2O3(0 1 2) substrates by molecular beam epitaxy technique. The overall conductivities of the films are found to increase with decreasing thickness. The detailed investigation of the overall conductance as a function of the thickness permits the deconvolution of bulk and boundary effects, the latter being attributed to distinct space charge effects in the interface between BaF2 film and Al2O3 substrate. The (extrinsic) Debye length (λ) is estimated to be about 8 nm at T=593 K, which corresponds to an impurity content of 1018/cm3 (singly ionized dopant assumed). This is consistent with the fact that we observed a constant boundary contribution for all investigated films (film thickness >4λ). It is also consistent with the Debye length observed in a previous report on CaF2/BaF2 heterolayers fabricated by the same technique, in which the low temperature enhancement was also attributed to space charges in BaF2 [Nature 408 (2000) 946]. Only at low temperatures (below 370 °C), the conductance seems to be influenced by strain effect. 相似文献
5.
在自旋-轨道劈裂阵模型下,通过类铜的内壳层激发组态计算了类镍Gd的双电子复合速率系数,其中考虑了共振和非共振辐射平衡跃迁对自电离能级的影响,而忽略了因碰撞跃迁引起的电子俘获,非共振辐射平衡跃迁在低电子温度条件下主要影响双电子复合过程;本文讨论了双电子复合系数及双电子伴线强度比随电子温度的变化. 相似文献
6.
Taking both the heterogeneous catalytic processes, including the surface formation of particles with excited internal degrees of freedom, and the processes of multicomponent diffusion and heat transfer in the MESOX apparatus fully into account makes it possible to obtain a recombination coefficient and an accommodation coefficient of the oxygen-atoms-on-quartz recombination energy which are in good agreement with the experimental data. The heterogeneous catalysis model constructed can be used effectively for predicting the heat fluxes to the surface of reentry vehicles on their entry into the Earth’s atmosphere. 相似文献
7.
本文从速率方程出发,讨论了类锂铝复合等离子体的激发态结构,衰减常数,反转率和小信号增益等表征介质增益特性的物理量以及它们随电子温度,电子密度和光子逃逸几率的变化。找到了进行类锂铝离子通过复合机制产生X光激光设计应创造的等离子体状态目标区域。还讨论了这些物理量随原子序数变化的定标律。 相似文献
8.
Perfluorocarboxylic thioesters RFC(O)SR (RF=CF3(CF2)j, R=CH3(CH2)i, i andj=0–5) were studied for the first time by GLC on packed columns using SE-30, SKTFT-50X, and XE-60 as the stationary phase.
The values of thermodynamics functions of sorption were calculated. The correlations between these functions and the molecular
structures as well as the conditions of analysis were established. The insertion of the S atom into the molecules of derivatives
of perfluorocarboxylic acids causes a decrease in the contribution of the orientation interaction and an increase in the dispersion
interaction of thioesters with the stationary phases compared to esters and amides of perfluorocarboxylic acids studied previously.
For Part 1, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1165–1168, June, 1997. 相似文献
9.
We revealed the changes in the γ-luminescence spectra under the influence of a thermal radiation field on high-purity alkali-silicate
glasses (I) and those with addition of Fe3+ ions (II). We explain the obtained results within the framework of the L-model of edge absorption and electron-hole recombination
processes.
Samarkand State University, 15, Universitetskii Bul., Samarkand, 703004, Republic of Uzbekistan. Translated from Zhurnal Prikladnoi
Spektroskopii, Vol. 65, No. 3, pp. 453–455, May–June, 1998. 相似文献
10.
The recombination kinetics of spin-correlated radical pairs (RPs) with three nonequivalent magnetic nuclei were calculated
under conditions of enforced encounters between radicals at time-independent frequency ndif. The simplest two-position model of a RP was used, which includes two states (contact state and distance-separated state)
of the RP, differing in magnitude of isotropic spin-spin exchange interaction between radicals. The calculated kinetic curves
were treated in terms of a three-exponential model. The dependences of corresponding rate constants (k
rec) on ndif, external magnetic field strength (B
0), and intensity, A
eff, of isotropic hyperfine coupling (HFC) were obtained. The k
rec-vs.-ndif or k
rec-vs.-viscosity (ndif varies simultaneously with the inverse lifetime of the contact state) plots pass through maxima whose positions are shifted
from the ndif region near the A
eff value at B
0 = 0.5 G toward high ndif values with an increase in B
0. At ndif ≫ A
eff, the k
rec-vs.-B
0 plots pass through maxima in the region B
0 = A
eff. The calculated dependences are compared with experimental data on recombination of biradicals. The results of calculations
show that the experimentally observed maxima on the k
rec-vs.-B
0 or k
rec-vs.-ndif plots can be due to peculiar features of the spin dynamics induced by the hyperfine coupling rather than the exchange interaction
effects, as is commonly accepted.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1103–1110, May, 2005. 相似文献