全文获取类型
收费全文 | 148篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 90篇 |
晶体学 | 2篇 |
力学 | 13篇 |
数学 | 31篇 |
物理学 | 20篇 |
出版年
2024年 | 1篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 8篇 |
2013年 | 21篇 |
2012年 | 14篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 11篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2003年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 2篇 |
排序方式: 共有156条查询结果,搜索用时 0 毫秒
31.
32.
A shift‐adaptive meshfree method for solving a class of initial‐boundary value problems with moving boundaries in one‐dimensional domain 下载免费PDF全文
Mohsen Esmaeilbeigi Gholamreza Garmanjani 《Numerical Methods for Partial Differential Equations》2016,32(6):1622-1646
A new shift‐adaptive meshfree method for solving a class of time‐dependent partial differential equations (PDEs) in a bounded domain (one‐dimensional domain) with moving boundaries and nonhomogeneous boundary conditions is introduced. The radial basis function (RBF) collocation method is combined with the finite difference scheme, because, unlike with Kansa's method, nonlinear PDEs can be converted to a system of linear equations. The grid‐free property of the RBF method is exploited, and a new adaptive algorithm is used to choose the location of the collocation points in the first time step only. In fact, instead of applying the adaptive algorithm on the entire domain of the problem (like with other existing adaptive algorithms), the new adaptive algorithm can be applied only on time steps. Furthermore, because of the radial property of the RBFs, the new adaptive strategy is applied only on the first time step; in the other time steps, the adaptive nodes (obtained in the first time step) are shifted. Thus, only one small system of linear equations must be solved (by LU decomposition method) rather than a large linear or nonlinear system of equations as in Kansa's method (adaptive strategy applied to entire domain), or a large number of small linear systems of equations in the adaptive strategy on each time step. This saves a lot in time and memory usage. Also, Stability analysis is obtained for our scheme, using Von Neumann stability analysis method. Results show that the new method is capable of reducing the number of nodes in the grid without compromising the accuracy of the solution, and the adaptive grading scheme is effective in localizing oscillations due to sharp gradients or discontinuities in the solution. The efficiency and effectiveness of the proposed procedure is examined by adaptively solving two difficult benchmark problems, including a regularized long‐wave equation and a Korteweg‐de Vries problem. © 2016Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 1622–1646, 2016 相似文献
33.
In this article, we study some algebraic and geometrical properties of polynomial numerical hulls of matrix polynomials and joint polynomial numerical hulls of a finite family of matrices (possibly the coefficients of a matrix polynomial). Also, we study polynomial numerical hulls of basic A-factor block circulant matrices. These are block companion matrices of particular simple monic matrix polynomials. By studying the polynomial numerical hulls of the Kronecker product of two matrices, we characterize the polynomial numerical hulls of unitary basic A-factor block circulant matrices. 相似文献
34.
35.
Gholamreza Khayatian Seyde Somaye Hosseini Shahed Hassanpoor 《Journal of the Iranian Chemical Society》2013,10(6):1167-1173
A green and sensitive dispersive liquid-phase microextraction procedure based on room-temperature ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) for preconcentration and determination of total iron in real samples prior to flame atomic absorption spectrometry was developed. 2-Mercaptopyridine-N-oxide (pyrithione) and ethanol were used as complexing agent and dispersive solvent in the proposed method, respectively. The factors influencing the extraction were optimized. Under optimum conditions, the enhancement factor of 15 was obtained from only 11.35 mL of aqueous phase. The linear dynamic range and the detection limit were 10.0–700 and 2.4 μg L?1, respectively. The relative standard deviation (RSD) for ten replicate measurements of 500 μg L?1 of iron is 3.1 %. The developed method has been successfully applied for the determination of iron in water samples, human blood serum and rock certified reference material with high efficiency. 相似文献
36.
Hossein Tavakol Saeed Hatami Shahryar Ghammamy Gholamreza Rezaei Bebahani Fahmideh Shabani 《Heteroatom Chemistry》2009,20(7):398-404
Synthesis, characterization, spectral and molecular parameters of some new room‐temperature ionic liquids (tetraalkylammonium bromotrichloro aluminum [R4N]+[AlCl3Br]−) have been studied in the present study. All synthesized ionic liquids were characterized by IR, 1H, 13C, and 81Br‐NMR. In addition, synthesized structures were optimized at the B3LYP/LANL2DZ level of theory and then the structures, molecular specifications, and infrared spectra of these were extracted using Gaussian 03 program. Theoretical data show good agreement with the experimental results. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:398–404, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20564 相似文献
37.
38.
Shahed Hassanpoor Gholamreza Khayatian Amir Reza Judy Azar 《Mikrochimica acta》2015,182(11-12):1957-1965
39.
Zahra Koohi Lai Ali Namaki Ali Hosseiny Gholamreza Jafari Marcel Ausloos 《Entropy (Basel, Switzerland)》2021,23(1)
In this paper, we focus on the critical periods in the economy that are characterized by unusual and large fluctuations in macroeconomic indicators, like those measuring inflation and unemployment. We analyze U.S. data for 70 years from 1948 until 2018. To capture their fluctuation essence, we concentrate on the non-Gaussianity of their distributions. We investigate how the non-Gaussianity of these variables affects the coupling structure of them. We distinguish “regular” from “rare” events, in calculating the correlation coefficient, emphasizing that both cases might lead to a different response of the economy. Through the “multifractal random wall” model, one can see that the non-Gaussianity depends on time scales. The non-Gaussianity of unemployment is noticeable only for periods shorter than one year; for longer periods, the fluctuation distribution tends to a Gaussian behavior. In contrast, the non-Gaussianities of inflation fluctuations persist for all time scales. We observe through the “bivariate multifractal random walk” that despite the inflation features, the non-Gaussianity of the coupled structure is finite for scales less than one year, drops for periods larger than one year, and becomes small for scales greater than two years. This means that the footprint of the monetary policies intentionally influencing the inflation and unemployment couple is observed only for time horizons smaller than two years. Finally, to improve some understanding of the effect of rare events, we calculate high moments of the variables’ increments for various q orders and various time scales. The results show that coupling with high moments sharply increases during crises. 相似文献
40.
Rostampour Malihe Aboudzadeh Mohammadreza Sadeghi Mahdi Hamidi Saeid Alirezapour Behroz Soltani Naser Aslani Gholamreza 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(3):1759-1766
Excitation functions and theoretical yields via charge particle induced reactions were evaluated using EMPIRE-3.2.2 and ALICE/ASH codes and the obtained results have been discussed and compared with the available reported experimental data. It has been verified that natCu(p,n)65Zn reaction is the optimum 65Zn production route. The 65Zn was produced using natCu(p,xn) 65Zn reaction in the energy range of 16.8 → 12.2 MeV with the thick target yield of 0.15 ± 0.005 MBq/μA h. The 65Zn radionuclide was purified by anion exchange chromatography.
相似文献