全文获取类型
收费全文 | 383篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
化学 | 207篇 |
晶体学 | 1篇 |
力学 | 22篇 |
数学 | 118篇 |
物理学 | 50篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 40篇 |
2012年 | 20篇 |
2011年 | 28篇 |
2010年 | 17篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 16篇 |
2006年 | 17篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 8篇 |
2002年 | 16篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1986年 | 2篇 |
1983年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有398条查询结果,搜索用时 31 毫秒
101.
Abdellatif Agouzal 《计算数学(英文版)》2000,18(6):639-644
1. IlltroductionThe finite element approximation of the convection--diffusin equations has been investigated using several different approaches (see e.g. [3] [4] and the references therein).Previous analysis in primal formulation of these problems was done for two types ofapproximation schemes: one which produces a continuous piecewise polynomial approximation and one which produces a piecewise polynomial approximation which arecontinuous for certain number of moments accross interelement edge… 相似文献
102.
Synthesis of Unprecedented Sulfonylated Phosphono‐exo‐Glycals Designed as Inhibitors of the Three Mycobacterial Galactofuranose Processing Enzymes 下载免费PDF全文
Christophe J.‐M. Frédéric Dr. Abdellatif Tikad Jian Fu Dr. Weidong Pan Ruixiang B. Zheng Dr. Akihiko Koizumi Dr. Xiaochao Xue Prof. Todd L. Lowary Prof. Stéphane P. Vincent 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15913-15920
This study reports a new methodology to synthesize exo‐glycals bearing both a sulfone and a phosphonate. This synthetic strategy provides a way to generate exo‐glycals displaying two electron‐withdrawing groups and was applied to eight different carbohydrates from the furanose and pyranose series. The Z/E configurations of these tetrasubstituted enol ethers could be ascertained using NMR spectroscopic techniques. Deprotection of an exo‐glycal followed by an UMP (uridine monophosphate) coupling generated two new UDP (uridine diphosphate)‐galactofuranose analogues. These two Z/E isomers were evaluated as inhibitors of UGM, GlfT1, and GlfT2, the three mycobacterial galactofuranose processing enzymes. Molecule 46‐(E) is the first characterized inhibitor of GlfT1 reported to date and was also found to efficiently inhibit UGM in a reversible manner. Interestingly, GlfT2 showed a better affinity for the (Z) isomer. The three enzymes studied in the present work are not only interesting because, mechanistically, they are still the topic of intense investigations, but also because they constitute very important targets for the development of novel antimycobacterial agents. 相似文献
103.
Debenzylative Cycloetherification: An Overlooked Key Strategy for Complex Tetrahydrofuran Synthesis 下载免费PDF全文
Dr. Abdellatif Tikad Julien A. Delbrouck Prof. Stéphane P. Vincent 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9456-9476
Tetrahydrofuran (THF) is a major structural feature found in many synthetic and natural products displaying a variety of biological properties. This review summarizes the main synthetic approaches that have been developed to construct tetrahydrofuran moieties involving debenzylative cycloetherification reactions (DBCE). Interestingly, this reaction is regio‐ and stereoselective without the requirement of a selective protection/deprotection strategy. Many applications of this process have been reported, including carbafuranoside synthesis, regioselective deprotection of the benzyl group positioned γ to an alkene, and total synthesis of natural products. The stereochemical outcome and the mechanism of these interesting transformations are also discussed. 相似文献
104.
Idriss Bakas Gorkem Yilmaz Zouhair Ait‐Touchente Aazdine Lamouri Philippe Lang Nicolas Battaglini Benjamin Carbonnier Mohamed M. Chehimi Yusuf Yagci 《Journal of polymer science. Part A, Polymer chemistry》2016,54(21):3506-3515
The surface chemistry of aryl diazonium salts has progressed at a remarkable pace in the last two decades, and opened many avenues in materials science. These compounds are excellent coupling agents for polymers to surfaces via several surface‐confined polymerization methods. For the first time, we demonstrate that diazonium salts are efficient for surface initiating radical photopolymerization in the visible light of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) taken as model monomers. To do so, 4‐(dimethylamino)benzenediazonium salt was electroreduced on gold plates or flexible ITO sheets to provide 4‐(dimethylamino)phenyl (DMA) hydrogen donor layers; while excited state camphorquinone acted as the free hydrogen abstractor. In the same way, we co‐polymerized HEMA and MMA with ethylene glycol dimethacrylate in order to obtain crosslinked polymer grafts. We demonstrate by XPS that gold was efficiently screened by the polymer layers and that the wettability of the surfaces accounts for the hydrophilic or hydrophobic characters of the tethered polymers. Homo‐ and crosslinked PMMA grafts were found to resist removal by the paint stripper methyl ethyl ketone. The grafted DMA/camphorquinone system operating in the visible light holds great promises in terms of adhesion of in situ designed continuous or patterned polymer coatings on various substrates. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3506–3515 相似文献
105.
In this Note we establish a Hölder stability estimate for an inverse pointwise source elliptic problem. 相似文献
106.
Ahmed Hader Imad Achik Khalid Sbiaai Lahcen El Arroum Yahia Boughaleb 《Optical and Quantum Electronics》2014,46(1):57-63
We aimed in this work to study numerically the scaling behavior and the mound morphological properties of the interfaces generated by the multilayer deposition process. We have found that when the diffusion process dominates strongly the deposition one, the obtained interfaces consist of wedding-cake like structures. The width of the surface is a self-affine fractal exhibiting non-trivial scaling with the surface height and the system size, and the obtained interfaces follow the Family–Vicsek law with exponent values more consisting with the Edwards–Wilkinson model. 相似文献
107.
Abdellatif Mamanou Fethi Khelfaoui Kamel Edinne Aiadi 《Optical and Quantum Electronics》2014,46(1):235-245
In this paper, a number of polymeric waveguide structures have been analyzed by using two distinct techniques which are: effective index method (EIM) and numerical simulation based on finite difference method (FDM). The main aim of this investigation is the calculation of effective indexes (EI) of the following structures: rib, ridge and buried channel waveguides at telecom wavelength $\lambda =1.55\,\upmu \hbox {m}$ for different dimensions of waveguide cores varying from 1.5–4 $\upmu \hbox {m}$ . Moreover, other optical propagation characteristics such as: confinement factor, normalized and propagation constant have been studied in TE polarisation. Otherwise the effect of the structure parameters and dimensions on the dispersion characteristics has been investigated. On the other hand, the optical field distribution has been computed using commercial software named OlympIOs. The polymers applied in the design of waveguide structures are the PVCi (n = 1,562 $\lambda = {1.55}\,\upmu $ m) used as core layer and the PMATRIFE (n = 1,409 $\lambda = 1.55\,\upmu $ m) used as substrate or cladding layer. The results obtained using EIM and simulation based on FDM show that effective index and field confinement factor of TE fundamental mode increase monotonously with the increasing dimension of core. The obtained results are in good agreement with published data based on other numerical methods. 相似文献
108.
Touahir L Galopin E Boukherroub R Gouget-Laemmel AC Chazalviel JN Ozanam F Saison O Akjouj A Pennec Y Djafari-Rouhani B Szunerits S 《The Analyst》2011,136(9):1859-1866
The use of an amorphous silicon-carbon alloy overcoating on silver nanostructures in a localized surface plasmon resonance (LSPR) sensing platform allows for decreasing the detection limit by an order of magnitude as compared to sensors based on gold nanostructures deposited on glass. In addition, silver based multilayer structures show a distinct plasmonic behaviour as compared to gold based nanostructures, which provides the sensor with an increased short-range sensitivity and a decreased long-range sensitivity. 相似文献
109.
Hakima Chicha Latifa Bouissane Lahcen El Ammari Mohamed Saadi Michel Baltas 《合成通讯》2013,43(17):2005-2013
AbstractThe treatment of N-alkyl-5-nitroindazole with stannous chloride in ethanol, aftercoupling of the obtained amines with arylsulfonyl chloride in pyridine, gave the new 4-ethoxy- and 4-chloroindazoles bearing sulfonamide in moderate to good yields. Chlorination and ethoxylation of indazole were observed during the reduction of the nitro group with anhydrous SnCl2 in ethanol. The influence of the N-alkylation in N-1 and N-2 position of 5-nitroindazole on the reduction was investigated. The presence ofethoxy group and chlorine atom at position C-4 of indazole was confirmed by x-ray diffraction analysis of compounds 7a and 8a. 相似文献
110.
Rahhal El Ajlaoui Amiri Ouafa Souad Mojahidi Lahcen El Ammari Mohamed Saadi 《合成通讯》2013,43(17):2035-2042
AbstractThe reaction of 3-allylrhodanine with 2-arylidene-4-methyl-5-oxopyrazolidinium ylides proceeded unexpectedly to form novel 3-allyl-5-(arylidene)-2-thioxo-thiazolidin-4-ones 6a–k in good yields. All structures have been formulated on the basis of their spectral (IR, NMR, MS) data and elemental analyses. In addition, the structure of compound 6a was confirmed by means of x-ray crystallographic analysis. 相似文献