全文获取类型
收费全文 | 140篇 |
免费 | 4篇 |
国内免费 | 2篇 |
专业分类
化学 | 85篇 |
晶体学 | 4篇 |
力学 | 11篇 |
数学 | 21篇 |
物理学 | 25篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1989年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有146条查询结果,搜索用时 31 毫秒
41.
42.
43.
Hassen Sbihi Faouzia Ouahmi Mohamed Beji Ahmed Baklouti 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):539-544
Abstract Reaction of highly fluorinated carboxylic acids with aroxysulfonylisocyanates in the presence of triethylamine allowed the preparation of the corresponding highly fluorinated aroxy-N-sulfonylsulfamates. The reaction proceeds with good yield in toluene at room temperature or more rapidly in the same solvent at 60 °C. Surface tension measurement at the air/water interface showed that these compounds constitute new excellent nonionic surfactants exhibiting high surface activity in the range of the best nonionic fluoro surfactants, already described in the literature. The critical micelle concentration (CMC) has been calculated from the surface tension measurements on surface aqueous solutions. 相似文献
44.
Natural frequencies and mode shapes of initially curved carbon nanotube resonators under electric excitation 总被引:1,自引:0,他引:1
Hassen M. Ouakad 《Journal of sound and vibration》2011,330(13):3182-3195
Estimating accurately the natural frequencies of electrically actuated carbon nanotubes (CNTs) has been an active research subject over the past few years. Despite the importance of the topic, robust knowledge is still missing in the understanding of the role of various physical parameters affecting the natural frequencies, such as the stretching of doubly clamped CNTs, the DC electrostatic force, and the initial curvature of slack CNTs. In this investigation, we use a 2D nonlinear curved beam model in the form of an arch to simulate the coupled in-plane and out-of-plane motions of a CNT with curvature. We calculate the variation of its natural frequencies and mode shapes with the level of slackness and the DC electrostatic load. Towards this end, we derive a reduced-order model using a multimode Galerkin procedure. We show various scenarios of mode crossing and mode veering as the levels of slackness and DC load are varied. Finally, we tackle the forced vibration problem of a curved CNT when actuated by small DC and AC loads. The results show the transfer of energy among the vibration modes involved in the veering phenomenon. 相似文献
45.
L. Beji L. Sfaxi B. Ismaïl A. Missaoui F. Hassen H. Maaref H. Ben Ouada 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):636-642
A typical porous structure with pores diameters ranging from 10 to 50 nm has been obtained by electrochemical etching of (1 0 0) heavily doped p-type GaAs substrate in HF solution. Room temperature photoluminescence (PL) investigations of the porous GaAs (π-GaAs) reveal the presence of two PL bands, I1 and I2, located at 1.403 and 1.877 eV, respectively. After GaAs capping, the I1 and I2 PL bands exhibit opposite shift trends. However, the emission efficiency of these two bands is not strongly modified. Low temperature PL of capped porous GaAs versus injection levels shows that the I1 PL band exhibits a red shift while the I2 PL band exhibits a blue shift with increasing injection levels. The I2 PL band intensity temperature dependence shows an anomalous behaviour and its energy location shows a blue shift as temperature increases. The observed PL bands act independently and are attributed to electron – hole recombination in porous GaAs and to the well-known quantum confinement effects in GaAs nanocrystallites. The I2 PL band excitation power and temperature dependencies were explained by the filling effect of GaAs nanocrystallites energy states. 相似文献
46.
Taissir Hentati Leila Bouazizi Mohamed Taktak Hassen Trabelsi Mohamed Haddar 《Applied Acoustics》2016
The identification of the physical parameters of porous materials presents an important field of research, in which many identification methods are developed. One of those methods is presented in this paper. In fact, a multi-levels inverse identification method is developed in order to estimate these physical parameters. The proposed method is based on the minimization of the difference between a reference acoustic absorption coefficient of a porous material and the computed values. The minimization is done according three levels, in each level an acoustic model of porous material is used to evaluate one or two parameters. Finally, the five physical parameters of the porous materials are deduced. The proposed method is applied to Polyurethane foam material. The obtained results are satisfying with small values of errors and with estimated acoustic absorption coefficient reaching the reference one. 相似文献
47.
M. Hnaiein W.M. Hassen A. Abdelghani C. Fournier-Wirth J. Coste F. Bessueille D. Leonard N. Jaffrezic-Renault 《Electrochemistry communications》2008,10(8):1152-1154
We report a new approach for immunoassays based on magnetite nanoparticles for Escherichia coli (E. coli) detection using conductometric measurements. Biotinylated antibodies, anti-E. coli, were immobilized on streptavidin modified magnetite nanoparticles by biotin–streptavidin interaction. A layer of functionalized nanoparticles were directly immobilized on the conductometric electrode using glutaraldehyde cross-linking.The specific test with E. coli cells and the non specific test using Staphylococcus epidermidis (S. epidermidis) were investigated by conductometric measurements. Results show a good response as a function of antigen additions. The detection of 1 CFU/ml of E. coli induces a conductivity variation of 35 μS. The negative test shows good selectivity using the conductometric immunosensor. Conductometric measurements allow to detect 500 CFU/l. 相似文献
48.
49.
3',5'-dimethoxybenzoin (DMB) is an important photoremovable protecting group. The primary photoreactions of DMB acetate and fluoride following photoexcitation by a subpicosecond laser flash were investigated by pump-probe spectroscopy. The primary photoproduct is identified as a preoxetane biradical intermediate that decays by different pathways depending on solvent polarity. In polar solvents (acetonitrile, water), the biradical decays by releasing acetate or fluoride with a lifetime of about 2 ns. Thus, DMB is an excellent protecting group for the investigation of fast processes such as protein folding. 相似文献
50.
Jens Schoene Hassen Bel Abed Mathias Christmann Marc Nazaré 《Tetrahedron letters》2017,58(16):1633-1635
A versatile two-step, one-pot reaction to access N-substituted-2H-indazol-2-amine derivatives has been elaborated. A diverse set of analogues was obtained by a sequential hydrazone formation and reductive cyclization in moderate to good yields from readily available starting materials. The strategy tolerates a broad range of substitutions pattern and functional groups allowing further derivatizations. 相似文献