全文获取类型
收费全文 | 508篇 |
免费 | 56篇 |
国内免费 | 35篇 |
专业分类
化学 | 205篇 |
晶体学 | 6篇 |
力学 | 14篇 |
综合类 | 8篇 |
数学 | 193篇 |
物理学 | 173篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 32篇 |
2013年 | 36篇 |
2012年 | 45篇 |
2011年 | 59篇 |
2010年 | 49篇 |
2009年 | 45篇 |
2008年 | 22篇 |
2007年 | 34篇 |
2006年 | 37篇 |
2005年 | 23篇 |
2004年 | 18篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 10篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有599条查询结果,搜索用时 15 毫秒
1.
《Journal of Crystal Growth》2006,286(2):400-406
Radiofrequency (RF) nitrogen plasma sources are commonly employed in the growth of group III-nitrides by molecular beam epitaxy and reactive evaporation. These sources produce atomic nitrogen and excited molecules (N2*). In this work the relative flux of these two species produced by an RF source was studied by emission spectroscopy as a function of power, pressure, and argon dilution. Polycrystalline indium nitride thin films were synthesized under the same conditions. It was found that argon dilution had a strong influence on the production of active nitrogen, with maximum fluxes obtained around ∼40% N2. Film properties, as measured by X-ray diffraction, atomic force microscopy and Hall effect, were also optimized at this condition. It was observed that the Hall mobility scaled with the sum of N and N2* emission, suggesting that both species may be beneficial for InN growth. 相似文献
2.
Kinetics of oxidation of lactose, maltose, cellobiose and melibiose has been studied by hexacyanoferrate(III) in the presence of ammonia. A general mechanism involving the formation of intermediate enodiol anion has been suggested. The effects of dielectric constant and salts have been studied in detail. The oxidation products have been characterised by descending paper chromatography. Compensation effects have been observed. 相似文献
3.
4.
合成了七(2,3-二-O-乙酰基-6-O-叔丁基二甲基硅烷基)-β-环糊精,并采用静态法成功地将其涂渍到弹性石英毛细管柱上。研究了其气相色谱分离性能,发现此固定相涂渍性好,柱效较高,热稳定性好,对卤代芳烃异构体以及难分离的二取代苯的位置异构体具有良好的分离能力。 相似文献
5.
《Solid State Communications》1986,59(8):565-568
Low frequency (< 30 cm-1) Raman scattering lineshapes for the chalcogenide glasses As2S3 and As2Se3 have been interpreted in terms of a model which explicitly includes acoustic (∼ ω2 density-of-states) and optic (rigid-layer like) vibrational modes. 相似文献
6.
7.
Effect of Reactor Pressure on Qualities of GaN Layers Grown by Hydride Vapour Phase Epitaxy 下载免费PDF全文
The influence of reactor pressure on GaN layers grown by hydride vapour phase epitaxy (HVPE) is investigated. By decreasing the reactor pressure from0. 7 to 0.5 mm, the GaN layer growth mode changes from the island-like one to the step flow. The improvements in structural and optical properties and surface morphology of GaN layers are observed in the step flow growth mode. The results clearly indicate that the reactor pressure, similarly to the growth temperature, is One of the important parameters to influence the qualities of GaN epilayers grown by HVPE, due to the change of growth mode. 相似文献
8.
S. Parveen S. Singh D. Shukla M. Yasmin M. Gupta J. P. Shukla 《Journal of solution chemistry》2012,41(1):156-172
Ultrasonic velocity, density, refractive index and viscosity of binary mixtures of aniline with acetic acid (AA) and propionic
acid (PA) have been measured at 293.15, 303.15 and 313.15 K over the entire composition range. Further, the specific heat
ratio, heat capacity, effective Debye temperature and pseudo-Gruensisen parameter and non-linearity parameter have been evaluated
using ultrasonic absorption data. The deviation in isentropic compressibility, excess molar volume, excess intermolecular
free length, deviation in molar refraction, deviation in viscosity, relaxation time, enthalpy, entropy and Gibbs energy of
activation have been calculated from the experimental data and fitted with the Redlich-Kister polynomial equation. A comparative
study has also been made between experimental and theoretically calculated values of densities using the HBT and Rackett density
models. Mixing rules for the prediction of refractive index, e.g. Lorentz-Lorenz (L-L), Eykmen (Eyk), Weiner (W), Heller (H),
Gladstone-Dale (G-D), Arago-Biot (A-B) and Newton (N) have been applied to these binary mixtures. 相似文献
9.
《Tetrahedron letters》2014,55(52):7190-7193
An iron-catalyzed coupling reaction of methylarenes with thiols leading to thioesters has been developed. The reactions were carried out in water with tert-butyl hydroperoxide (TBHP) as the oxidant and polyoxyethanyl α-tocopheryl sebacate (PTS) as the surfactant. The reaction medium is compatible with a series of functional groups and can be reused. 相似文献
10.