全文获取类型
收费全文 | 508篇 |
免费 | 26篇 |
国内免费 | 8篇 |
专业分类
化学 | 205篇 |
晶体学 | 1篇 |
力学 | 26篇 |
数学 | 146篇 |
物理学 | 73篇 |
无线电 | 91篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 19篇 |
2019年 | 20篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 25篇 |
2015年 | 11篇 |
2014年 | 25篇 |
2013年 | 52篇 |
2012年 | 34篇 |
2011年 | 27篇 |
2010年 | 22篇 |
2009年 | 21篇 |
2008年 | 30篇 |
2007年 | 19篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 19篇 |
2003年 | 14篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1885年 | 1篇 |
排序方式: 共有542条查询结果,搜索用时 172 毫秒
81.
In this paper, we deal with the acoustic inverse scattering problem for reconstructing cracks of possibly different types from the far‐field map. The scattering problem models the diffraction of waves by thin two‐sided cylindrical screens. The cracks are characterized by their shapes, the type of boundary conditions and the boundary coefficients (surface impedance). We give explicit formulas of the indicator function of the probe method, which can be used to reconstruct the shape of the cracks, distinguish their types of boundary conditions, the two faces of each of them and reconstruct the possible material coefficients on them by using the far‐field map. To test the validity of these formulas, we present some numerical implementations for a single crack, which show the efficiency of the proposed method for suitably distributed surface impedances. The difficulties for numerically recovering the properties of the crack in the concave side as well as near the tips are presented and some explanations are given. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
82.
Mourad Bellassoued 《Applicable analysis》2013,92(10):983-1014
One of the basic inverse problems in an anisotropic media is the determination of coefficients in a bounded domain with a single measurement. We consider the problem of finding the coefficient of the second derivatives in a second-order hyperbolic equation with variable coefficients. Under a weak regularity assumption and a geometrical condition on the metric, we prove the uniqueness in a multidimensional hyperbolic inverse problem with a single measurement. Moreover we show that our uniqueness results yield the Lipschitz stability estimate in L 2 space for solution to the inverse problem under consideration. 相似文献
83.
Maya?Al AzriEmail author Mohamed?Elzain Khalid?Bouziane Salim Mourad?Chérif 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(9):402
The electronic and magnetic properties of 6H-SiC with Mn impurities have been calculated using GGA formalism. Various configurations of Mn sites were considered. It was found that 6H-SiC doped with Mn atoms possess a moment for both types of substitution. The Mn atom at Si site possesses larger magnetic moment than Mn atom at C site. The energy levels appearing in the band gap due to vacancies and due to Mn impurities are determined and the calculated densities of states (DOSs) are used to analyse the different value of the magnetic moments for different types of substitution. A model that explains the magnetic moment at Mn site is proposed. 相似文献
84.
85.
Yann K. Petit Christian Leypold Nika Mahne Elonore Mourad Lukas Schafzahl Christian Slugovc Sergey M. Borisov Stefan A. Freunberger 《Angewandte Chemie (International ed. in English)》2019,58(20):6535-6539
Singlet oxygen (1O2) causes a major fraction of the parasitic chemistry during the cycling of non‐aqueous alkali metal‐O2 batteries and also contributes to interfacial reactivity of transition‐metal oxide intercalation compounds. We introduce DABCOnium, the mono alkylated form of 1,4‐diazabicyclo[2.2.2]octane (DABCO), as an efficient 1O2 quencher with an unusually high oxidative stability of ca. 4.2 V vs. Li/Li+. Previous quenchers are strongly Lewis basic amines with too low oxidative stability. DABCOnium is an ionic liquid, non‐volatile, highly soluble in the electrolyte, stable against superoxide and peroxide, and compatible with lithium metal. The electrochemical stability covers the required range for metal–O2 batteries and greatly reduces 1O2 related parasitic chemistry as demonstrated for the Li–O2 cell. 相似文献
86.
Karaman Abdelhak Boudjahem Abdel-Ghani Boulbazine Mouhssin Gueid Abdelhak 《Structural chemistry》2020,31(1):203-214
Structural Chemistry - DFT calculations have been carried out over the IrnV (n = 2–10) clusters in order to predict their stability, electronic, and catalytic properties. Based on the... 相似文献
87.
Arrahli Abdellah Kherbeche Abdelhak Bianchi Daniel 《Research on Chemical Intermediates》2019,45(3):1421-1436
Research on Chemical Intermediates - FTIR spectroscopy and volumetric measurements are used to study the adsorption of CO (mainly 1% CO/He) in the temperature range 300–713 K on a... 相似文献
88.
Houda Daoud Sawssen Lahiani Samir Ben Salem Mourad Loulou 《International Journal of Electronics》2020,107(4):659-682
ABSTRACTWith the aggressive scaling of integrated circuit technology, parametric estimation is a critical task for designers who looked for solutions to the challenges of some Nanoscale CMOS parameters. This paper presented the prediction of primary parameters of CMOS transistor for 16 nm to 10 nm process nodes using both of Bisquare Weights (BW) method and a novel recursive least squares (RLS) parameter estimation algorithm. The proposed RLS algorithm consists of the minimisation of a quadratic criterion relating to the prediction error in order to attain the best estimated parameters of the developed mathematical model. The obtained results thanks to the proposed RLS algorithm were better than those reached using the BW method. Comparisons between Predictive Technology Model (PTM) data and parameters estimated with RLS algorithm were made to check the validity and the consistency of the proposed algorithm. These predicted primary parameters were helpful to estimate and to optimise the performances of the Variable Gain Amplifier (VGA) which was a basic circuit element with a key role in the design of new upcoming receivers. 相似文献
89.
Ayari Faouzi Mannei Emna Asedegbega-Nieto Esther Mhamdi Mourad Guerrero-Ruiz Antonio Ricardo Delahay Gérard Ghorbel Abdelhamid 《Journal of Thermal Analysis and Calorimetry》2018,131(2):1295-1306
Journal of Thermal Analysis and Calorimetry - Thermal decomposition (2 K min?1) of ammonium heptamolybdate tetrahydrate, performed between room temperature and... 相似文献
90.