全文获取类型
收费全文 | 185篇 |
免费 | 3篇 |
专业分类
化学 | 134篇 |
力学 | 3篇 |
数学 | 16篇 |
物理学 | 35篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1902年 | 2篇 |
排序方式: 共有188条查询结果,搜索用时 61 毫秒
11.
Artale MA Augugliaro V Drioli E Golemme G Grande C Loddo V Molinari R Palmisano L Schiavello M 《Annali di chimica》2001,91(3-4):127-136
The possibility of entrapping polycrystalline TiO2 in a polymeric support, in order to couple the two unit operations, i.e. ultrafiltration and photodegradation of organic pollutants in aqueous solutions, was investigated. To this aim, polymeric membranes for ultrafiltration with entrapped TiO2 were prepared, characterised and tested. The polymeric support chosen was commercial polysulfone (PSf). The membrane preparation was carried out with the technique referred to as phase inversion. A three-component system, with a polymer, a solvent and a non-solvent was used. The best operative conditions were determined in order to obtain the desired membrane morphology. Permeability measurements and photostability tests were also carried out by using a system under pressure. Finally, a preliminary investigation was performed in order to evaluate the photocatalytic activity of the membranes with entrapped TiO2 for the oxidation of 4-nitrophenol as a model molecule in aqueous solutions. 相似文献
12.
Measurements of the electronic energy loss are presented for (4)He and (7)Li ions channeling along the Si main axial directions at intermediate to high projectile energies. The Barkas effect, an energy-loss enhancement proportional to the third power of the projectile charge at high energies, is clearly separated from other processes. It reaches about 50% for Li ions channeling along the Si [110] direction. The observed Barkas contribution from the valence-electron gas is in fair agreement with the Lindhard model. 相似文献
13.
14.
Hasan Guleryuz Ingeborg Kaus Claudine Filiàtre Tor Grande Mari-Ann Einarsrud 《Journal of Sol-Gel Science and Technology》2010,54(2):249-257
Deposition of silica thin films on silicon wafer was investigated by in situ mass measurements with a microbalance configured
for dip coating. Mass change was recorded with respect to deposition time when the substrate was fully immersed in the silica
sol. Mass gain during deposition was higher than predicted from monolayer coverage of silica nano particles. This implied
that deposition was facilitated by gelling of the nanoparticles on the substrate. The rate of deposition was enhanced by increasing
the particle concentration in the sol and by decreasing the particle size from 12 to 5 nm. Increasing the salt concentration
of the silica sol at constant pH enhanced the deposition of the silica particles. Reducing the pH of the sol from 10 to 6
decreased the deposition rate due to aggregation of the primary silica particles. 相似文献
15.
D.F. Sanchez F.P. Luce Z.E. Fabrim M.A. Sortica P.F.P. Fichtner P.L. Grande 《Surface science》2011,605(7-8):654-658
Medium energy ion scattering (MEIS) measurements and transmission electron microscopy (TEM) observations are applied to characterize a buried Pb nanoparticle (NP) system synthesized by ion implantation. The NPs are located at the SiO2/Si film interface, forming a dense two-dimensional array. Full 2D (energy and angle) experimental MEIS spectra are compared with Monte Carlo simulated ones. The results demonstrate that MEIS measurements provide microstructural information (mean NP volume of about 150 nm3 and areal density of about 4 × 1011 NP/cm2), but no accurate information on the NP geometrical shape. 相似文献
16.
17.
B. Das S. Grande W. Weissflog A. Eremin M. W. Schr der G. Pelzl S. Diele H. Kresse 《Liquid crystals》2003,30(5):529-539
New meta -substituted homologous three-ring mesogens, the 4-(3- n -decyloxyphenyliminomethyl) phenyl 4- n -alkyloxybenzoates, have been synthesized, which are non-linear due only to the attachment of one of the alkyloxy groups in a meta -position. The mesophases were studied by optical microscopy, differential scanning calorimetry, NMR spectroscopy, X-ray diffraction, and electro-optical and dielectric measurements. Unusual phase behaviour was observed on varying the length of the terminal chain. The most interesting finding is the occurrence of two polymorphic tilted smectic phases designated as SmC 1 and SmC 2 . The existence of these phases was revealed by calorimetric studies and also from the pronounced difference in optical textures. It was shown from NMR measurements that the molecular orientation changes from a synclinic to an anticlinic arrangement in the SmC 1 to SmC 2 phase transition. It has also been shown, using NMR, that the SmC 1 →SmC 2 phase transition in these compounds is accompanied by a conformational change in the molecular fragment containing the aromatic ring with the meta -substituted terminal alkyloxy chain. This conformational change is linked to a change in the shape of the molecules and leads to a different packing of the molecules within the layers of the SmC 2 phase. From dielectric measurements an increase by a factor of two was detected in the molecular mobility at the transition into the low temperature SmC 2 phase. This finding supports a change in the packing as result of conformational changes. 相似文献
18.
About Oxocuprates. XV. The Crystal Structure of Rare Earth Oxocuprates: La2CuO4, Gd2CuO4 Gd2CuO4 and La2CuO4 are examined by single crystal X-ray methods. Gd2CuO4 is isotypic with Nd2CuO4, La2CuO4 however shows a slightly distorted K2NiF4 structure. Cu2+ has square (Gd2CuO4) or octahedral (La2CuO4) coordination. La2CuO4 is the only compound in the system of Rare Earth cuprates with K2NiF4-type structure. 相似文献
19.
20.
Hilde Lea Lein Øystein Skottun Andersen Per Erik Vullum Edgar Lara-Curzio Randi Holmestad Mari-Ann Einarsrud Tor Grande 《Journal of Solid State Electrochemistry》2006,10(8):635-642
Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of and , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship
observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials.
Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature
creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending
was in the range 107–128 MPa. The corresponding fracture toughness of , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture
mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface
of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient
temperature fracture strength and toughness. 相似文献