全文获取类型
收费全文 | 402篇 |
免费 | 3篇 |
国内免费 | 12篇 |
专业分类
化学 | 129篇 |
晶体学 | 2篇 |
力学 | 157篇 |
综合类 | 3篇 |
数学 | 16篇 |
物理学 | 110篇 |
出版年
2023年 | 19篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 15篇 |
2014年 | 28篇 |
2013年 | 17篇 |
2012年 | 12篇 |
2011年 | 27篇 |
2010年 | 18篇 |
2009年 | 25篇 |
2008年 | 24篇 |
2007年 | 32篇 |
2006年 | 19篇 |
2005年 | 19篇 |
2004年 | 18篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有417条查询结果,搜索用时 437 毫秒
101.
The present paper shows how a standard volumetric adsorption device can be used to measure solvent desorption isotherms on
gels. As gels are very soft materials, they shrink significantly during the measurement, and the data have to be analyzed
in terms of the mechanical properties of the gel’s skeleton. Methanol desorption isotherms are measured on a series of silica
gels, and the results are compared with independent characterizations, notably beam bending. 相似文献
102.
Solid-phase photocatalytic degradation of polystyrene (PS) plastic with TiO2 as photocatalyst was investigated in the ambient air under ultraviolet light irradiation. Higher weight loss rate, lower average molecular weight, increased carbonyl peak intensity, less volatile organics and more CO2 emitted with irradiation in PS-TiO2 composite sample compared to pure PS sample were observed. These facts indicated the higher photodegradation rate of PS-TiO2 sample than that of PS sample, and emphasized the potential of the composite sample in bring about complete photodegradation of polystyrene plastic. It is implied that the degradation initially occurred over TiO2 particles, followed by the diffusion reaction with the aid of reactive oxygen species generated on TiO2 particle surface. 相似文献
103.
Tung-Lin Li 《European Polymer Journal》2007,43(8):3368-3373
A new high temperature, flexible and colorless indium-tin-oxide (ITO) coated plastic substrate has been prepared from a thermally stable, high glass transition temperature (Tg) and colorless polyimide film. The polyimide was synthesized from 3,3′-diaminodiphenylsulfone (3,3′-DDS) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) monomers. Its heat distortion temperature was 278 °C. The ITO was deposited on the polyimide film using the magnetron-sputtering process. After annealing at 250 °C under nitrogen for 1 h, the resistivity of the ITO film was 4.0 × 10−4 Ω cm, and its transmittance was 83.5%. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to observe the surface and morphology of the ITO film. UV-visible spectroscopy and the four-probe method were used to study their optical and electrical properties. The high performance ITO-plastic substrate can be used in the next generation flat panel displays. 相似文献
104.
Use of surfactants to remove water-based inks from plastic film: effect of calcium ion concentration and length of surfactant hydrophobe 总被引:1,自引:0,他引:1
Hatice?GecolEmail author John?F.?Scamehorn Sherril?D.?Christian Brian?P.?Grady Fred?E.?Riddell 《Colloid and polymer science》2004,283(2):154-163
Effective plastic film deinking could permit the reuse of recycled polymer to produce clear film, reduce solid waste for landfills, reduce raw material demand for polymer production, and aid process economics. In this study, the deinking of a commercial polyethylene film printed with water-based ink was studied using surfactants in the presence of hardness ions (calcium ions) at various pH levels. The electrostatic properties of ink particles in a washing bath were also investigated. Synthetic anionic surfactant or fatty acid soap in the presence of calcium ions at alkaline pH levels was found to be nearly as effective at deinking as cationic, nonionic, or amphoteric surfactants alone. However, adding calcium ions decreases the deinking effectiveness of cationic, nonionic, and amphoteric surfactants. Increasing the length of the ionic surfactant hydrophobe enhances deinking. Zeta potential measurements showed that water-based ink particles in water reach the point of zero charge (PZC) at a pH of about 3.6, above which ink particles are negatively charged, so cationic surfactant tends to adsorb better on the ink than anionic surfactant above the PZC in the absence of calcium. As the cationic surfactant concentration is varied between 0.005 and 25 mM, the zeta potential of the ink particles reverses from negative to positive owing to adsorption of cationic surfactant. For anionic surfactants, added calcium probably forms a bridge between the negatively charged ink and the negatively charged surfactant head groups, which synergizes adsorption of the surfactant and aids deinking. In contrast, calcium competes for adsorption sites with cationic and nonionic surfactants, which inhibits deinking. All the surfactants studied here disperse ink particles effectively in the washing bath above pH 3 except for the ethoxylated amine surfactant. 相似文献
105.
106.
This paper studied the results of evaluation on resistance to radiation, moisture permeability, bacteria permeability, tensile strength, elongation at break and sealing ability for several plastic films available on the market. The result shows that nylon, sarin, and polyethylene complex films, high and low density polyethylene films are applicable for packing of radiation sterilized products. 相似文献
107.
Liquid-phase catalytic degradation of polyethylene wax over MFI zeolites with different particle sizes 总被引:2,自引:0,他引:2
The liquid-phase catalytic degradation of polyethylene wax into fuel oil was studied over MFI catalysts with different particle sizes (0.2 to 4.0 μm). Although structures and acidities of these catalysts were almost the same, the degradation activity varied greatly according to their particle size. The small particle catalyst showed higher activity due to its larger external surface, due to the low restriction on the mass transfer of large polymer molecules. Product distribution was also dependent on the particle size, producing higher hydrocarbons in the liquid product on the catalyst of small particles. The particle size effect of MFI zeolite on its activity and product composition in the liquid-phase degradation was discussed. 相似文献
108.
109.
Kinetic modeling of the thermal degradation of polyethylene and polystyrene mixtures 总被引:5,自引:0,他引:5
Tiziano Faravelli Giulia Bozzano Mauro Colombo Eliseo Ranzi Mario Dente 《Journal of Analytical and Applied Pyrolysis》2003,70(2):1193-777
One possible process for recovering valuable chemical and petrochemical products from plastic waste is the stepwise thermal degradation of polymer mixtures. This potentially allows the step by step simultaneous separation of the different product fractions generated by the polymers of the blend. The aim of this paper is to investigate the effect of the mixing scale of the polymers and their interactions in the melt. Several thermogravimetric analyses were performed on small samples of polyethylene (PE) and polystyrene (PS) mixtures. Two types of operating conditions were adopted: the first one is a dynamic analysis with a linear increase of the temperature over time, the latter consists of two sequential isothermal steps. The experimental results confirm that if the mixing scale is poor, the decomposition of each polymer behaves independently of the presence of the other one. Conversely, when the mixing of the two polymers reaches the molecular scale, a co-pyrolysis takes place with partial interactions. A two phase system is assumed: one phase characterized by a larger PS fraction, the other one by a prevailing PE amount. In order to properly predict the kinetic interactions typical of the mixed phases, it was necessary to extend the detailed kinetic model already developed and validated for the single polymers. The resulting two phase model gives a satisfactory explanation of several experimental data from the thermal degradation of PE–PS mixtures. 相似文献
110.