全文获取类型
收费全文 | 247篇 |
免费 | 11篇 |
国内免费 | 15篇 |
专业分类
化学 | 68篇 |
力学 | 16篇 |
数学 | 98篇 |
物理学 | 91篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 34篇 |
2012年 | 12篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 15篇 |
2008年 | 7篇 |
2007年 | 16篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 15 毫秒
131.
Peter Legisa 《Linear and Multilinear Algebra》2013,61(3):157-188
Let Mn be the space of all n × n matrices with coefficients in [image omitted] or [image omitted], where n ≥ 3. The star order on Mn is defined by [image omitted] iff [image omitted], where A* is the Hermitian adjoint (i.e., the conjugate transpose) of A. We characterize surjective mappings Φ on Mn such that [image omitted] iff [image omitted]. The tools we use are the Fundamental theorem of projective geometry, Wigner's theorem, and the Penrose decomposition, which we need to describe the main result as well. 相似文献
132.
R. Porter F. Liu A. Williams 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(14):2084-2094
The exact solution to radiative heat transfer in combusting flows is not possible analytically due to the complex nature of the integro-differential radiative transfer equation (RTE). Many different approximate solution methods for the solution of the RTE in multi-dimensional problems are available. In this paper, two of the principal methods, the spherical harmonics (P1) and the discrete ordinates method (DOM) are used to calculate radiation. The radiative properties of the gases are calculated using a non-gray gas full spectrum k-distribution method and a gray method. Analysis of the effects of numerical quadrature in the DOM and its effect on computation time is performed. Results of different radiative property methods are compared with benchmark statistical narrow band (SNB) data for both cases that simulate air combustion and oxy-fuel combustion. For both cases, results of the non-gray full spectrum k-distribution method are in good agreement with the SNB data. In the case of oxy-fuel simulations with high partial pressures of carbon dioxide, use of gray method for the radiative properties may cause errors and should be avoided. 相似文献
133.
《Arabian Journal of Chemistry》2020,13(1):366-376
The synthesis of neodymium(III) bromide (NdBr3) by sintering brominating of neodymium oxide (Nd2O3) with ammonium bromide (NH4Br) was investigated. The influence of various synthesis parameters (temperature, contact time and stoichiometry) on the reaction yield was studied and optimized. The main interaction effects of the synthesis parameters on the reaction yield were also determined by a full 23 factorial designs with six replicates at the center point.This study showed that the optimum conditions for the synthesis of NdBr3 are following: contact time t = 60 min, stoichiometry in moles Nd2O3:NH4Br = 1:24 and temperature T = 400 °C. The reaction yield for these parameters was equal to 97.80%. The first order model was obtained to predict the reaction yield as a function of these three parameters. It was shown that all parameters have a significant positive influence on reaction yield. In addition it was pointed out also that the interaction effects between them are significant. 相似文献
134.
This research conducts an exhaustive search for the best spectral test performance in a full period linear congruential generator (LCG) with the largest prime modulus smaller than 2b, for bit sizes b = 8, 9, … , 31. Three types of restrictions on multipliers are presented and some full period LCGs are presented for use in three different spectral test dimensions. According to the exhaustive searches we perform, the results indicate differences exist among the numbers of possible multipliers for the three types of multiplier restrictions. We demonstrate that these differences can affect the performance of spectral tests for different dimensions. 相似文献
135.
建立了一种小波软阈值法(STWPLS)同时测定铜(Ⅱ)、镉(Ⅱ)、锌(Ⅱ)方法。此法结合多分辩分析和软阈值法改进除噪质量。通过最佳化,小波函数,低频收缩截止水平(L)和阈值法类型分别选为Daubechies8,3和HYBRID。并将此法与偏最小二乘法(PLS)做了比较。 相似文献
136.
137.
138.
K. Burrage J. van Casteren S. Piskarev 《Numerical Functional Analysis & Optimization》2013,34(10):1019-1040
We consider a stochastic regularization method for solving the backward Cauchy problem in Banach spaces. An order of convergence is obtained on sourcewise representative elements. 相似文献
139.
B. Kheirfam 《Numerical Functional Analysis & Optimization》2013,34(10):1322-1338
In this article, we present a new full Nesterov-Todd step infeasible interior-point method for second-order cone optimization based on a non-coercive kernel function. The main iteration consists of a so-called feasibility step and one centering step, whereas the earlier versions, in [4, 21], needed two additional centering steps. We use a kernel function to induce the feasibility step. The new algorithm reduces the searching steps in each iteration and tenders an interesting analysis for complexity bound. 相似文献
140.
Sang Hyun Park SeJin Ahn Jihye Gwak Keeshik Shin Seoung Kyu Ahn Kyunghoon Yoon Yunae Cho Dong-Wook Kim Jae Ho Yun 《Current Applied Physics》2013,13(8):1684-1688
This study examined the effect of UV-spectrum light soaking on solar cell degradation tests. An indoor light soaking test was evaluated over three different spectral ranges: “UV only”, “UV blocked” and “Full spectrum”. a-Si:H and poly-crystalline silicon solar cell technologies were studied by light soaking tests with the same optical filter configurations.The I–V measurement results demonstrated that “UV only” irradiated solar cells exhibited the smallest output power degradation, which was only half of a percent variation compared with the full spectrum light soaking case. Using a filter that excluded the effect of the UV spectral range on light soaking, the “UV blocked” case also exhibited a significant output power degradation of the solar cells. A comparative analysis of the solar cell response, based on the I–V characteristics and the diode ideality factor under these different light soaking spectra, demonstrated the importance of the full spectrum light soaking test in the evaluation of the long-term performance of solar cells. 相似文献