全文获取类型
收费全文 | 243篇 |
免费 | 5篇 |
专业分类
化学 | 150篇 |
晶体学 | 3篇 |
力学 | 18篇 |
数学 | 36篇 |
物理学 | 41篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 22篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 30篇 |
2012年 | 18篇 |
2011年 | 23篇 |
2010年 | 18篇 |
2009年 | 11篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 5篇 |
1998年 | 1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248条查询结果,搜索用时 15 毫秒
241.
Noureddine Said Soufiane Touil Azaiez Ben Akacha Mohamed Lotfi Efrit 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2726-2733
The reaction of α -phosphonylketones 1 with active methylenenitriles 2 leads to phosphonoalkylidenes 3 . The reaction of compounds 3 with sulfur under basic conditions leads to the new 2-amino-4-phosphonothiophenes 4 . The structure of all obtained products was confirmed by NMR (1H, 31P, 13C) and IR spectroscopy, and in some cases by mass spectrometry. 相似文献
242.
Abdallah Harizi Noureddine Saïd Zine Mighri Hédi Zantour 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2623-2632
A variety of 5-aryl-3-[(1-dialcoxyphosphonyl)methyl]-1,2,4-triazoles 3 has been synthesized efficiently by treatment of trialkylphosphites with 5-aryl-3-chlorométhyl-1,2,4-triazoles 2 . Compound 2 has been prepared by action of N-chloroacylimidates 1 with hydrazines. The structure of triazoles 2 and 3 have been unequivocally confirmed by means of IR, 1 H, 13 C, 31 P NMR spectroscopy and mass spectra. 相似文献
243.
Meriem Toumi Med Abderrahmane Sanhoury Michel Bordeau Noureddine Raouafi Khaled Boujlel 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):920-930
Abstract Hindered rotation in alkyldithiocarbamates of the type RR′NC(= S)SR″ [R, R′, R″ = Me, Me, Et (1); PhCH2, Me, Et (2); PhCH2, H, Et (3); PhCH2, H, Me (4) and O(CH2CH2)2, Et (5)′ has been investigated using variable-temperature 1H NMR spectroscopy in CDCl3, C6D6, and DMSO-d6 solutions. Rotational parameters were calculated by the coalescence temperature method. Nitrogen substituent effects on the free energy of activation and on the equilibrium constant of unsymmetrical conformers at room temperature are discussed. 相似文献
244.
The structure of bis(N,N,N′,N′-tetramethylthiophosphoramidoyl)-methylamine 1 has been determined by single-crystal X-ray diffraction. The compound 1 crystallizes in the monoclinic system, with a space group P21/c, a = 11.836(2) Å, b = 11.659(2) Å, c = 12.796(5) Å and β = 95.28(3)°, V = 1758.3(5) Å3 and Z = 4. The X-ray crystallographic data have been assessed by semi-empirical and ab-initio density functional theory and by Hartree–Fock molecular orbital methods. A comparative study of the results of the different methods is given. 相似文献
245.
Dr. Khouloud Hchicha Dr. Noureddine Mhadhbi Dr. Ahlem Guesmi Dr. Taoufik Soltani Dr. Naoufel Ben Hamadi Prof. Houcine Naïli 《欧洲无机化学杂志》2023,26(13):e202200696
S-substituted La2Mo2O9 were synthesized by a solid-state procedure employing ammonium sulfate (NH4)2SO4 as a sulfur source. The synthesized powders were examined using X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared, and Raman spectroscopies. The results divulged that the stabilization of the β-La2Mo2O9 polymorph occurred in the interval of sulfur composition 0.1≤y≤0.6. This substitution generates a linear dwindling of the unit cell volume. The decomposition of all substituted samples started above 900 °C with a total weight loss linearly dependent on the sulfur content. Electrical studies confirmed that substituting S6+ for Mo6+ suppresses the phase transition of La2Mo2O9 and stabilizes the cubic polymorph down to ambient temperature. It was also remarkable that this substitution caused a decrease in the conductivity, and unfortunately, none of the tested compositions allowed exceeding the conductivity of La2Mo2O9. Infrared and Raman spectra confirmed the presence of the characteristic peaks of sulfates and molybdates groups. 相似文献
246.
The electrochemical behavior of sulfaguanidine was investigated in PBS buffer aqueous solutions. Cyclic voltammograms have shown that (1) the Sg provided a well-defined irreversible oxidation peak (2) the signal-to-background current ratio is 3 times higher at COOH-MWCNT coated GCE than that of bare GCE and (3) the modifying GCE surface by COOH-MWCNT led to a significant improvement (2.7 folds) of the electrochemical response. It has been shown that Sg oxidizes according to a diffusion-controlled mechanism. A linear calibration curve was obtained for the oxidation of Sg at 10–70 μM. The COOH-MWCNT coated GCE has also been successfully used for the determination of Sg in real samples. 相似文献
247.
Jose Fidel Chavez Juan Jorge Martinez-Vega Noureddine Zouzou Jean Guastavino 《Macromolecular Symposia》2004,212(1):485-490
Polymers find an important field of application in the electrical industry because of their utilization as insulators and dielectrics. The challenge over the last several years has been to make electrical compounds smaller in size. In that way the material morphology is of strategic importance in the performance of new components in relation to their geometry. Therefore, it is important to know the influence of different types of stress on electric properties of the materials. We have studied the influence of the crystallinity on electric conductance of poly(ethylenenaphthalene-2,6-dicarboxylate) (PEN), which is increasingly replacing some dielectrics (polypropylene and PET) in certain electric applications. Starting from an amorphous PEN, samples with various crystallinities were obtained and analyzed using DSC in order to determine their thermal characteristics. Moreover, measurements of charge and discharge currents were carried out on PEN samples to characterize their electric properties. The steady state current observed after 120 min, in response to the electric field, shows an increase in the insulator resistivity with the crystallinity. The increase in the crystallinity favors a decrease in the free volume, so the movement of charges is restricted especially by the species of large sizes. 相似文献
248.
Mabrouk Walid Jebri Sonia Charradi Khaled Silimi Bishir Alzahrani Abdullah Y. A. Boubakri Ali Ghodbane Ouassim Raouafi Noureddine Keshk Sherif. M. A. S. 《Journal of Solid State Electrochemistry》2023,27(4):991-999
Journal of Solid State Electrochemistry - In this study, graphene (G) was blended with sulfonated polyether sulfone octyl sulfonamide (SPESOS) in different ratios (1, 1.5, and 2 wt.%) to enhance... 相似文献