全文获取类型
收费全文 | 366篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
化学 | 248篇 |
晶体学 | 5篇 |
力学 | 36篇 |
数学 | 61篇 |
物理学 | 32篇 |
出版年
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 20篇 |
2015年 | 6篇 |
2014年 | 18篇 |
2013年 | 34篇 |
2012年 | 28篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 18篇 |
2008年 | 20篇 |
2007年 | 20篇 |
2006年 | 15篇 |
2005年 | 8篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1989年 | 3篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1938年 | 1篇 |
1921年 | 1篇 |
排序方式: 共有382条查询结果,搜索用时 484 毫秒
291.
Using a system of cavity quantum electrodynamics(QED) we present two schemes for multipartite entanglement generation. In the first scheme, a three-level atom is interacting with three cavities successively. In the second one, two three-level atoms are interacted with a coherent optical cavity. These protocols allow us to generate the six classes of tripartite entanglement(GHZ, W, A-B-C, AB-C, C-AB, and B-AC class states) by controling the interaction time between atoms and cavities. Moreover, they allow us to generate entanglement between the cavity fields degrees of freedom(from the first scheme), and a mixed entanglement between the cavity field degrees of freedom and the atomic degrees of freedom. 相似文献
292.
This work consists in evaluating algebraically and numerically the influence of a disturbance on the spectral values of a diagonalizable matrix. Thus, two approaches will be possible; to use the theorem of disturbances of a matrix depending on a parameter, due to Lidskii and primarily based on the structure of Jordan of the no disturbed matrix. The second approach consists in factorizing the matrix system, and then carrying out a numerical calculation of the roots of the disturbances matrix characteristic polynomial. This problem can be a standard model in the equations of the continuous media mechanics. During this work, we chose to use the second approach and in order to illustrate the application, we choose the Rayleigh–Bénard problem in Darcy media, disturbed by a filtering through flow. The matrix form of the problem is calculated starting from a linear stability analysis by a finite elements method. We show that it is possible to break up the general phenomenon into other elementary ones described respectively by a disturbed matrix and a disturbance. A good agreement between the two methods was seen. To cite this article: H.B. Hamed, R. Bennacer, C. R. Mecanique 336 (2008). 相似文献
293.
Yassine Benmassaoud Khaled Murtada Rachid Salghi Mohammed Zougagh ngel Ríos 《Molecules (Basel, Switzerland)》2022,27(9)
A rapid and sensitive technique for frauds determination in vanilla flavors was developed. The method comprises separation by liquid chromatography followed by an electrochemical detection using a homemade screen-printed carbon electrode modified with aluminium-doped zirconia nanoparticles (Al-ZrO2-NPs/SPCE). The prepared nanomaterials (Al-ZrO2-NPs) were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). This method allows for the determination of six phenolic compounds of vanilla flavors, namely, vanillin, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, vanillyl alcohol, vanillic acid and ethyl vanillin in a linear range between 0.5 and 25 µg g−1, with relative standard deviation values from 2.89 to 4.76%. Meanwhile, the limits of detection and quantification were in the range of 0.10 to 0.14 µg g−1 and 0.33 to 0.48 µg g−1, respectively. In addition, the Al-ZrO2-NPs/SPCE method displayed a good reproducibility, high sensitivity, and good selectivity towards the determination of the vanilla phenolic compounds, making it suitable for the determination of vanilla phenolic compounds in vanilla real extracts products. 相似文献
294.
Back Cover: Unravelling the Correlation between the Aspect Ratio of Nanotubular Structures and Their Electrochemical Performance To Achieve High‐Rate and Long‐Life Lithium‐Ion Batteries (Angew. Chem. Int. Ed. 49/2014) 下载免费PDF全文
295.
Electrochemical degradation of buprofezin insecticide in aqueous solutions by anodic oxidation at boron-doped diamond electrode 总被引:1,自引:0,他引:1
Mohamed Errami Rachid Salghi Mohammed Zougagh Abdelkader Zarrouk El Houcine Bazzi Abdelkhaleq Chakir Hassan Zarrok Belkheir Hammouti Lahcen Bazzi 《Research on Chemical Intermediates》2013,39(2):505-516
Buprofezin (2-tert-butylimino-3-isopropyl-5-phenyl-1,3,5-thiadiazinan-4-one) is identified as a commonly used chemical with satisfactory biological activities against sucking insect pests, but its disposal causes serious environmental problems. This pesticide was treated by an electrolysis system using a boron-doped diamond (BDD) as anode and platinum as cathode. A number of experiments were run on a laboratory scale and the results are presented. The chemical oxygen demand (COD) measurement during the processing permitted the evaluation of the kinetic of organic matter decay and the instantaneous current efficiency. Different operating conditions and factors affecting the treatment process including current density, conductive electrolyte, pH, concentration of buprofezin, and time of electrolysis were studied and optimized. The best obtained conditions for COD removal on the BDD anode to degrade buprofezin solutions (COD0 = 1,200 mg L?1) include operating at 60 mA cm?2 and 25 ± 3 °C. The high efficiency of this technology can be explained in terms of the direct electrooxidation at the BDD surface and the oxidation carried out by hydroxyl radicals (OH?) and other electro-generated oxidants (Cl?, ClO?). 相似文献
296.
Alberto Navalón Rachid El-Khattabi Antonio González-Casado José Luis Vilchez 《Mikrochimica acta》1999,130(4):261-265
The reduction reaction of imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] at a mercury electrode shows two well-defined waves in the range of pH 2.0–11.0. The characteristics of the electrode processes were examined. The analyte captures four electrons in the first step and two in the second to give the hydroxylamine and amine derivatives, respectively. A differential-pulse polarographic method for the determination of imidacloprid based on the first reduction peak of this compound is presented. Britton-Robinson buffer was used as a supporting electrolyte and optimum pH value was found to be pH 8.O. The applicable concentration range was from 10 to 200 ng/ml, with a relative standard deviation of 1.5% (for a level of 80 ng/ml) and a detection limit of 3 ng/ml. The method has been satisfactorily applied to the determination of imidacloprid in commercial formulations. 相似文献
297.
298.
299.
Rachid Saim Rachid Bouchenafa Hamidou Benzenine Hakan F. Oztop Khaled Al-Salem Said Abboudi 《Heat and Mass Transfer》2013,49(6):761-774
Numerical studies of momentum and heat transfer characteristics have been investigated of a steady incompressible turbulent flow of air through channel. The channel has inclined baffles which are arranged on the walls in a periodically staggered way. The governing equations, namely, continuity, Navier–Stokes and energy, based on k–ω turbulence model to describe the turbulence phenomenon are solved using the finite volume method and the SIMPLE algorithm. Calculations are performed for a Reynolds number between 12,000 and 38,000. The axial velocity profiles, the velocity fields, the local and average coefficient of friction and the Nusselt number distribution were obtained for all the geometry considered and for different sections selected, upstream, downstream and between the two inclined baffles. Simulation results which were obtained by the use of baffles are validated by an experimental study. Good agreement is observed between numerical and experimental results data in the literature. 相似文献
300.
Jean-François Ganghoffer Rachid Rahouadj 《Continuum Mechanics and Thermodynamics》2016,28(1-2):443-463
We presently extend the virial theorem for both discrete and continuous systems of material points with variable mass, relying on developments presented in Ganghoffer (Int J Solids Struct 47:1209–1220, 2010). The developed framework is applicable to describe physical systems at very different scales, from the evolution of a population of biological cells accounting for growth to mass ejection phenomena occurring within a collection of gravitating objects at the very large astrophysical scales. As a starting basis, the field equations in continuum mechanics are written to account for a mass source and a mass flux, leading to a formulation of the virial theorem accounting for non-constant mass within the considered system. The scalar and tensorial forms of the virial theorem are then written successively in both Lagrangian and Eulerian formats, incorporating the mass flux. As an illustration, the averaged stress tensor in accreting gravitating solid bodies is evaluated based on the generalized virial theorem. 相似文献