全文获取类型
收费全文 | 256篇 |
免费 | 5篇 |
专业分类
化学 | 154篇 |
晶体学 | 3篇 |
力学 | 18篇 |
数学 | 35篇 |
物理学 | 51篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 22篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 30篇 |
2012年 | 19篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 14篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 5篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有261条查询结果,搜索用时 15 毫秒
71.
N. Benzekkour N. Gabouze K. Ferdjani S. Sam K. Henda 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):168
In this work, we report a study on the influence of CHx thickness layer on optical properties of CHx/PS/Si structures. The hydrocarbon groups were deposited by plasma of methane–argon mixture.The properties of these structures are investigated by photoluminescence (PL), reflection and spectral response measurements from where a different behavior depending on CHx layer thickness has been observed.The entire total reflection spectrum is modulated by Fabry–Pérot fringes that are a result of thin film interference. As the CHx layer thickness increases, the amplitude of the interferences decreases and a positive shift of the maximum peak is observed.The PL spectra from CHx/PS samples with two CHx layer thicknesses show more intense luminescence than that observed from PS sample and the existence of an optimum thickness CHx that gives the maximum PL intensity. The spectral response spectra show the presence of an intense peak at 450 nm. Finally, the results point out the importance of CHx coating in optoelectronic applications. 相似文献
72.
A. Louhadj Mohamed Ghezali F. Badi Noureddine Mehnane Youcef Cherchab Bouhalouane Amrani Hamza Abid Nadir Sekkal 《Superlattices and Microstructures》2009,46(3):435-442
Using the plane wave version of the full potential linear muffin-tin orbital (FPLMTO) method, which enables an accurate treatment of the interstitial regions, the electronic properties of ScN, YN, LaN and GdN rocksalt/rocksalt superlattices are calculated. It is found that apart from YN/ScN, all the other superlattices have negative bandgaps. However, it is shown that these systems can be semiconductors if a correction is made to the local density approximation (LDA). 相似文献
73.
Mejri Imen Kouissi Taoufik Toumi Adel Ouerfelli Noureddine Bounaz Moncef 《Journal of solution chemistry》2021,50(9-10):1131-1168
Journal of Solution Chemistry - Density, speed of sound and viscosity data for the binary mixtures (1,4-dioxane (1)?+?water (2)), were measured over the whole composition range at... 相似文献
74.
Coraline Sester Fabrice Ofridam Noureddine Lebaz Emilie Gagnire Denis Mangin Abdelhamid Elaissari 《先进技术聚合物》2020,31(3):440-450
Poly (methyl methacrylate) derivatives such as Eudragit are largely used for drug encapsulation and in controlled oral drug delivery. With special focusing on those applications, solubilization and precipitation conditions of two pH‐sensitive Eudragit polymers, namely, L100 and E100, were investigated via systematic studies. Effects of various physicochemical parameters such as pH, polymer concentration, salinity, buffer concentration, and incubation time on the solubilization and precipitation of these polymers were investigated. In addition, pH titration of both polymers was reported. Considering both macroscopic and quantitative aspects such as the final mean particle size, size distribution, morphology, and the zeta potential, it was established that the different precited parameters could not be dissociated and exert a synergic action on the solubilization and precipitation of both polymers. Titration curves revealed two equivalences that helped estimating carboxylic content of Eudragit L100 (6 mmol/g) and ammonium content of Eudragit E100 (4 mmol/g). In this study, the solubilization and the precipitation domains were for the first time clearly established by considering the above‐mentioned parameters. Moreover, it was found that Eudragit L100 and E100 cannot be considered as classic polyelectrolytes; in fact, solubilization and precipitation domains were not affected by ionic strength. 相似文献
75.
Clémence Guillaume Noureddine Ajellal Jean‐François Carpentier Sophie M. Guillaume 《Journal of polymer science. Part A, Polymer chemistry》2011,49(4):907-917
The controlled ring‐opening polymerization of racemic allyl‐β‐butyrolactone (rac‐BLallyl) in toluene or in bulk, catalyzed by the discrete β‐diiminate zinc amido [(BDIiPr)Zn(N(SiMe3)2)] ( 1 ) or {amino‐methoxy‐bis(phenolate)}yttrium amido [(ONOOtBu)Y(N(SiHMe2)2)(THF)] ( 2 ) complexes, in association with an alcohol, gave poly(β‐hydroxyalkanoate)s (PHAs) with allylic side chains. These PHAsallyl exhibit either a slightly isotactic‐enriched (Pm = 0.61) or highly syndiotactic‐enriched (Pr = 0.82) backbone structure, respectively, with high molar mass (M n up to 21,100 g mol?1) and narrow molar mass distribution values (1.05 < M w/M n < 1.28), as evidenced by detailed 13C NMR and size exclusion chromatography analyses. Postpolymerization rhodium‐catalyzed hydroboration of the resulting PHAsallyl with pinacolborane quantitatively afforded the corresponding PHAsboron. Introduction of boron into the pendant chains did not alter neither the structure of the polymer backbone nor the macromolecular features (M n, M w/M n, and stereoregularity). However, differential scanning calorimetry analyses revealed a significant increase of the glass transition temperature on modifying the allyl for the boron function in these PHAs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
76.
77.
78.
79.
Bouhadjar Boukoussa Zahira Kibou Zakaria Abid Rachida Ouargli Noureddine Choukchou-Braham Didier Villemin Abdelkader Bengueddach Rachida Hamacha 《Chemical Papers》2018,72(2):289-299
Mesoporous silica Si-MCM-41 was prepared by hydrothermal method using TEOS and CTAB as the source of silica and structuring agent, respectively. The surface of the as-synthesized material was treated using HCl/ETOH solvent to remove the CTA surfactant instead of using the calcination. Characterization of the catalysts was performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen sorption at 77 K, scanning and transmission electronic microscopy (SEM, TEM), and thermogravimetric analysis TGA. The catalytic properties of the prepared materials in the condensation of acetophenone with ethyl cyanoacetate were studied. The effects of the catalyst type, Si/Al ratio, reaction kinetics, and reaction temperature were also investigated to find an optimal parameter. The results show that an interesting yield was obtained (about 96%) in a short reaction time; it is found that the yields of products depend not only on the amount of surfactant inside the mesopores but also on the Si/Al ratio. The catalyst reuse shows that this catalyst can be used up to five cycles, and at temperatures higher than 50 °C, the yield of products decreases due to the slight destruction of the catalyst as confirmed by the XRD analysis. Based on the results obtained, a possible mechanism of the condensation reaction of acetophenone was proposed. 相似文献
80.
Noureddine Charef Lekhmici Arrar Ali Ourari Ruba M. Zalloum Mohammad S. Mubarak 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):177-184
A new polystyrene-supported Schiff base resin, N,N-bis(salicylidenepropylenetriamine)- aminomethyl polystyrene, has been synthesized through a reaction between the commercially available 4-chloromethyl polystyrene polymer and the Schiff base, N,N′-disalicylidenepropylenetriamine. The chelation behavior of this resin toward the divalent metal ions Cu2 +, Ni2 +, Zn2 +, and Pb2 + in aqueous solutions was investigated. Batch equilibration experiments were carried out as a function of contact time, pH, amount of metal-ion, polymer mass, and temperature. The amount of metal-ion uptake of the polymers was determined by using atomic absorption spectrometry (AAS). Results of the study revealed that the resin exhibited higher capacities and a more pronounced adsorption toward Cu2 + and that the metal-ion uptake follows the order: Cu2 + > Zn 2 + > Ni2 + > Pb2+. The adsorption and binding capacity of the resin toward the various metal ions investigated are discussed. 相似文献