全文获取类型
收费全文 | 412篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
化学 | 252篇 |
晶体学 | 2篇 |
力学 | 26篇 |
数学 | 67篇 |
物理学 | 75篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 30篇 |
2011年 | 23篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 22篇 |
2007年 | 37篇 |
2006年 | 22篇 |
2005年 | 9篇 |
2004年 | 23篇 |
2003年 | 17篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有422条查询结果,搜索用时 15 毫秒
121.
Control of Luminescence by Tuning of Crystal Symmetry and Local Structure in Mn4+‐Activated Narrow Band Fluoride Phosphors 下载免费PDF全文
Mu‐Huai Fang Wei‐Lun Wu Prof. Dr. Ye Jin Tadeusz Lesniewski Dr. Sebastian Mahlik Prof. Dr. Marek Grinberg Prof. Dr. Mikhail G. Brik Dr. Alok M. Srivastava Dr. Chang‐Yang Chiang Prof. Dr. Wuzong Zhou Dr. Donghyuk Jeong Prof. Dr. Sun Hee Kim Dr. Grzegorz Leniec Prof. Dr. Slawomir M. Kaczmarek Dr. Hwo‐Shuenn Sheu Prof. Dr. Ru‐Shi Liu 《Angewandte Chemie (International ed. in English)》2018,57(7):1797-1801
Mn4+‐doped fluoride phosphors have been widely used in wide‐gamut backlighting devices because of their extremely narrow emission band. Solid solutions of Na2(SixGe1?x)F6:Mn4+ and Na2(GeyTi1?y)F6:Mn4+ were successfully synthesized to elucidate the behavior of the zero‐phonon line (ZPL) in different structures. The ratio between ZPL and the highest emission intensity υ6 phonon sideband exhibits a strong relationship with luminescent decay rate. First‐principles calculations are conducted to model the variation in the structural and electronic properties of the prepared solid solutions as a function of the composition. To compensate for the limitations of the Rietveld refinement, electron paramagnetic resonance and high‐resolution steady‐state emission spectra are used to confirm the diverse local environment for Mn4+ in the structure. Finally, the spectral luminous efficacy of radiation (LER) is used to reveal the important role of ZPL in practical applications. 相似文献
122.
123.
This paper examines the universal quantitative properties of the fractional- and integer-order Chen?CLee systems. A?series of bifurcation diagrams of the system were generated in order to measure Feigenbaum??s constants. It was found that the measured values of the integer-order system were accurately approaching their universal constants, while the errors between measured values of the fractional-order system and the universal constants were not very large. The results showed that both the fractional- and integer-order Chen?CLee systems belonged to a quadratic map. To the authors?? knowledge, this is the first paper to measure Feigenbaum??s constants in fractional-order systems. 相似文献
124.
Guey‐Horng Wang Jui‐Hsin Su Chien‐Ting Chen Chang‐Yih Duh Chang‐Feng Dai Jyh‐Horng Sheu 《中国化学会会志》2004,51(1):217-220
Two novel polyhydroxysteroids, (24S)‐24‐methylcholestane‐3β,5α,6β,25ξ;,26‐pentol 26‐n‐decanoate ( 1 ), (24S)‐24‐methylcholestane‐3β,5α,6β,25ξ;,26‐pentol 25,26‐diacetate ( 2 ), and three known sterols ( 3‐5 ), have been isolated from a Formosan soft coral Sarcophyton glaucum. The molecular structures of these compounds were determined by spectral methods. The cytotoxicity of these compounds toward various cancer cell lines has also been determined. 相似文献
125.
Solvent evaporation upon drying the precipitate was found to be the key factor for the phase transformation of cubic mesoporous silica SBA-1 to hexagonal SBA-3 studied by in-situ X-ray diffraction and 29Si solid state NMR on the precipitates formed various crystallisation conditions. 相似文献
126.
127.
Polyethylene (PE) particles are produced by a catalyst prepared by contacting a (C4H9Cp)2ZrCl2/MAO pre‐mixing solution with SiO2 support. These particles have a large granular size and very few fine particles compared with those derived from a catalyst prepared by adsorption of (C4H9Cp)2ZrCl2 onto methylaluminoxane modified SiO2. The amount of Al in the pre‐mixing catalyst has an important effect on its activity and the PE particle size distribution. The optimal concentration is about 30 wt.‐%. The PE particles produced using a pre‐mixing catalyst consist of globules with randomly oriented fiber structure on the surface, whereas those produced using adsorption catalysts have worm‐like fibrils protruding from the PE globule surface. 相似文献
128.
H. J. Chen S. Schaible R. L. Sheu 《Journal of Optimization Theory and Applications》2009,141(1):93-105
We propose a unified framework to study various versions of Dinkelbach-type algorithms for solving the generalized fractional
programming problem. Classical algorithms used carefully selected iterate points and incorporated subtle convergence proofs.
Our generic algorithm, however, is natural and simple. Moreover, the convergence analysis can be carried out through geometric
observations and fundamental properties of convex functions. Consequently, the classical results are either refined or strengthened
with new insights. 相似文献
129.
Wen-Ying Wang Shey-Huei Sheu Yan-Chun Chen Der-Juinn Horng 《European Journal of Operational Research》2009
This paper addresses issues relating to off-line inspection with rework consideration. We develop a mathematical model to determine the first unit inspected and the average number to be inspected in a batch, assuming the involvement of a quality-control department with a standard procedure. Numerical analyses are used to simulate the effect of changes in the various parameters on the optimal solution when the probability of a transition between states follows the discrete Weibull distribution. 相似文献
130.
The 1,3-dipolar cycloaddition reactions of nitrile oxides and α,β-unsaturated 1,3-dioxolanes were effectively accelerated by ultrasound irradiation to give the A2-isoxazolines with yields and regioselectivities surpassing those of the corresponding thermal reactions. 相似文献