全文获取类型
收费全文 | 185篇 |
免费 | 16篇 |
专业分类
化学 | 158篇 |
晶体学 | 3篇 |
力学 | 3篇 |
数学 | 9篇 |
物理学 | 28篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 9篇 |
2013年 | 6篇 |
2012年 | 17篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 2篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有201条查询结果,搜索用时 31 毫秒
1.
2.
Panos M. Pardalos Wanpracha Chaovalitwongse Leonidas D. Iasemidis J. Chris Sackellares Deng-Shan Shiau Paul R. Carney Oleg A. Prokopyev Vitaliy A. Yatsenko 《Mathematical Programming》2004,101(2):365-385
There is growing evidence that temporal lobe seizures are preceded by a preictal transition, characterized by a gradual dynamical change from asymptomatic interictal state to seizure. We herein report the first prospective analysis of the online automated algorithm for detecting the preictal transition in ongoing EEG signals. Such, the algorithm constitutes a seizure warning system. The algorithm estimates STLmax, a measure of the order or disorder of the signal, of EEG signals recorded from individual electrode sites. The optimization techniques were employed to select critical brain electrode sites that exhibit the preictal transition for the warning of epileptic seizures. Specifically, a quadratically constrained quadratic 0-1 programming problem is formulated to identify critical electrode sites. The automated seizure warning algorithm was tested in continuous, long-term EEG recordings obtained from 5 patients with temporal lobe epilepsy. For individual patient, we use the first half of seizures to train the parameter settings, which is evaluated by ROC (Receiver Operating Characteristic) curve analysis. With the best parameter setting, the algorithm applied to all cases predicted an average of 91.7% of seizures with an average false prediction rate of 0.196 per hour. These results indicate that it may be possible to develop automated seizure warning devices for diagnostic and therapeutic purposes.Mathematics Subject Classification (1991):20E28, 20G40, 20C20 相似文献
3.
Galina A. Selivanova Leonid M. Pokrovskii Vitaliy D. Shteingarts 《Journal of fluorine chemistry》2004,125(12):1829-1834
Chlorine-containing polyfluorinated anilines and meta-phenylenediamines undergo selective hydrodechlorination easily upon reduction by zinc in aqueous ammonia. A new approach is thus provided to synthetically valuable, partially fluorinated arylamines based on utilizing polyfluorochloroarenes, which are available as intermediates of perfluoroarene production from perchloroarenes. When chlorine atoms are present in positions both ortho and para to the amino group, para chlorine is initially eliminated. Based on this reaction, a one-pot synthesis of partially fluorinated 4-aminopyridines from 3,5-dichlorotrifluoro- and 3-chlorotetrafluoropyridine has been realized. 相似文献
4.
Zauresh S. Nurkeeva Al-Sayed Abdel Aal Vitaliy V. Khutoryanskiy Grigoriy A. Mun Aida G. Beksyrgaeva 《Radiation Physics and Chemistry》2003,67(6):717-722
Gamma-radiation grafting of vinyl ether of monoethanolamine and vinyl ether of ethyleneglycol (VEEG) on polyethylene films has been studied from binary monomer mixtures. The effect of co-monomer composition and total exposure radiation dose on the grafting process is investigated. A combination of potentiometric and gravimetric techniques is applied to determine the grafting degree of each monomer in the final graft copolymer. The presence of more active monomer VEEG in the mixture was found to enhance the grafting of both monomers because the increasing of copolymerization rate which in turn increases the total grafting degree. The modification of the hydrophilic properties of the graft copolymer is studied by examining the grafted films for water- and copper (II) ions uptake. 相似文献
5.
Vitaliy Petrik 《Tetrahedron letters》2007,48(19):3327-3330
The easy radical trifluoromethylation of a series of 1,3-dicarbonyl compounds with CF3I is described. The reaction occurs in the presence of a nitrogen base and sodium dithionite in CH3CN-H2O solution. Additionally, we report a new access to ammonium triflinates. 相似文献
6.
Budarin VL Clark JH Tavener SJ Wilson K 《Chemical communications (Cambridge, England)》2004,(23):2736-2737
The reaction of localised C[double bond, length as m-dash]C bonds on the surface of activated carbons has been shown to be an effective method of chemical modification especially using microwave-assisted reactions. 相似文献
7.
The reaction of 1,4-dilithiotetraphenylbutadiene (2) with 1,1′-dichloro-2,3,4,5-tetraphenyl-1-silole (3) leads to 2,3,4,5-tetraphenyl-1-(1,2,3-triphenylnaphthalen-4-yl)-1H-silole (5) instead of the expected octaphenyl-1,1′-spirobisilole (1). The reaction of 2 with SiC14 in dioxane produced 1 in low yield, confirming results reported earlier. 相似文献
8.
9.
Andriy B. Zaborovskiy Ruslan E. Prystansky Vitaliy I. Timokhin 《Journal of organometallic chemistry》2004,689(18):2912-2919
The interaction of (Me3Si)3SiH with O2 is known to afford (Me3SiO)2Si(H)SiMe3 in which the two oxygen atoms arise from the same oxygen molecule. In order to investigate the mechanism of this unusual reaction, the oxidation rates were measured in the temperature range 30-70 °C by following oxygen uptake in the presence and absence of hydroquinone as inhibitor. The rate constant for the spontaneous reaction of (Me3Si)3SiH with O2 was determined at 70 °C to be ∼3.5 × 10−5 M−1 s−1. A sequence of the propagation steps is proposed by combining the previous and present experimental findings with some theoretical results obtained at the semiempirical level. These calculations showed that the silylperoxyl radical (Me3Si)3SiOO undergoes three consecutive unimolecular steps to give (Me3SiO)2Si()SiMe3. Evidence has been obtained that the rate determining step is the rearrangement of silylperoxyl radical to a dioxirand-like pentacoordinated silyl radical. Our findings are of considerable importance for the understanding of the oxidation of hydrogen-terminated silicon surfaces. 相似文献