全文获取类型
收费全文 | 178篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 135篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 28篇 |
物理学 | 29篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 14篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
排序方式: 共有194条查询结果,搜索用时 15 毫秒
21.
Javier Mazuela Oscar Pàmies Montserrat Diéguez Laetitia Palais Stephane Rosset Alexandre Alexakis 《Tetrahedron: Asymmetry》2010,21(17):2153-2157
A biaryl-based monophosphoroamidite L1–L4a–f and aminophosphine L5–L7a–f ligand library was screened in the Rh-catalyzed asymmetric hydroformylation of several vinylarenes and heterocyclic olefins. Our results indicate that the selectivity is strongly dependent on the ligand parameters and on the substrate type. Enantioselectivities (up to 46%) were moderate in the hydroformylation of several vinylarenes S1–S5 and promising (up to 58%) for the more challenging heterocyclic olefins S6–S9. 相似文献
22.
Juan Alfonso Redondo Enrique Martínez‐Campos Laetitia Plet Mnica Prez‐Perrino Rodrigo Navarro Guillermo Corrales Abhay Pandit Helmut Reinecke Alberto Gallardo Jos Luis Lpez‐Lacomba Alfonso Fernndez‐Mayoralas Carlos Elvira 《Macromolecular rapid communications》2016,37(7):575-583
The incorporation of cyclodextrins (CDs) to nonviral cationic polymer vectors is very attractive due to recent studies that report a clear improvement of their cytocompatibility and transfection efficiency. However, a systematic study on the influence of the CD derivatization is still lacking. In this work, the relevance of β‐CD permethylation has been addressed by preparing and evaluating two series of copolymers of the cationic N‐ethyl pyrrolidine methacrylamide (EPA) and styrenic units bearing pendant hydroxylated and permethylated β‐CDs (HCDSt and MeCDSt, respectively). For both cell lines, CDs permethylation shows a strong influence on plasmid DNA complexation, “in vitro” cytocompatibility and transfection efficiency of the resulting copolymers over two murine cell lines. While the incorporation of the hydroxylated CD moiety increased the cytotoxicity of the copolymers in comparison with their homopolycationic counterpart, the permethylated copolymers have shown full cytocompatibility as well as superior transfection efficiency than the controls. This behavior has been related to the different chemical nature of both units and tentatively to a different distribution of units along the polymeric chains. Cellular internalization analysis with fluorescent copolymers supports this behavior.
23.
Maria Chudnovsky Louis Esperet Laetitia Lemoine Peter Maceli Frédéric Maffray Irena Penev 《Journal of Graph Theory》2017,84(3):221-232
We prove that a graph G contains no induced ‐vertex path and no induced complement of a ‐vertex path if and only if G is obtained from 5‐cycles and split graphs by repeatedly applying the following operations: substitution, split unification, and split unification in the complement, where split unification is a new class‐preserving operation introduced here. 相似文献
24.
The stereoselective synthesis of both cis- and trans-β-fluorostyrene derivatives from a common intermediate, (Z)-1-aryl-2-fluoro-1-(trimethylsilyl)ethenes, is described. The trans isomers are obtained by a stereospecific replacement of the silyl group in the presence of water and a fluoride source, whereas the preparation of the cis isomers is achieved by a bromination/desilicobromination sequence followed by reduction of the newly created C-Br bond. A stereoselective transformation of both stereoisomers of β-fluorostyrene is also presented. 相似文献
25.
Renard L Elhamzaoui H Jousseaume B Toupance T Laurent G Ribot F Saadaoui H Brötz J Fuess H Riedel R Gurlo A 《Chemical communications (Cambridge, England)》2011,47(5):1464-1466
Self-assembled nanoporous tin-based hybrid thin films prepared by the sol-gel method from organically-bridged ditin hexaalkynides detect hydrogen gas from 50 to 200 °C at the 200-10,000 ppm level. This finding opens a fully new class of gas-sensing materials as well as a new opportunity to integrate organic functionality in gas sensing metal oxides. 相似文献
26.
Temperature and pressure sensitivities of the highly birefringent photonic crystal fiber with core asymmetry 总被引:2,自引:0,他引:2
T. Nasilowski T. Martynkien G. Statkiewicz M. Szpulak J. Olszewski G. Golojuch W. Urbanczyk J. Wojcik P. Mergo M. Makara F. Berghmans H. Thienpont 《Applied physics. B, Lasers and optics》2005,81(2-3):325-331
We investigated a particular design of a highly birefringent PCF with attractive features for pressure sensing applications. A plane-wave method together with the finite element method were used to numerically calculate phase and group modal birefringence, pressure and temperature sensitivities of our fiber. The simulation results together with the experiments demonstrate a considerable difference between a very high phase birefringence (B ∼ 10−3) and a very low negative group birefringence (G −10−3). Our fiber exhibits a low and positive temperature sensitivity (KT < 0.1 rad/(K⋅m)), and relatively high and negative mechanical (pressure) sensitivity (Kp ≤ −10 rad/(MPa⋅m)), which supports its possible use as a mechanical sensor that does not require any temperature compensation. 相似文献
27.
28.
The 1,4-addition of the lithium enolate of methyldithioacetate (LMDTA) to (+/-)-4-O-TBS-2-cyclohexenone (3) can be varied from being highly 3,4-trans selective to being highly 3,4-cis selective simply by varying the reaction temperature. This stereodivergency allows expedient syntheses of the corresponding trans and cis methyl esters 6t and 6c and derived bicyclic ketolactones 7t and 7c. 相似文献
29.
Jean-Charles Boisson Laetitia Jourdan El-Ghazali Talbi Dragos Horvath 《Journal of Mathematical Modelling and Algorithms》2010,9(2):195-208
In this article, the impact of single-objective methods as intensification factors in a multi-objective approach is presented
for the flexible docking problem. Based on a novel tri-objective model, a parallel multi-objective genetic algorithm has been
designed. However, due to the high variability of the energy objective, intensification methods focused on this objective
have been also included in order to improve the convergence speed of the genetic algorithm and the quality of the results.
The corresponding approach, combining single- and multi-objective methods, has been proved efficient according to the tested
instances and the quality criterion used. 相似文献
30.
Marie-Éléonore Marmion Laetitia Jourdan Clarisse Dhaenens 《Journal of Mathematical Modelling and Algorithms》2013,12(1):3-26
Landscape analysis has been identified as a promising way to develop efficient optimization methods. Nevertheless, the links between properties of the landscape and efficiency of methods is not easy to understand. In this article, we propose to give a contribution in this field using a vehicle routing problem as an illustration. Metaheuristics use a neighborhood operator that connects solutions of the search space. Thus, this operator acts on the dynamics of the search and impacts metaheuristics efficiency. Therefore, we characterize two landscapes differenciated by their neighborhood function and then, we analyze the performance of classical metaheuristics using one or the other neighborhood operator. Finally, a discussion provides insights on the relations between results of the landscape analysis and results of methods performance. 相似文献