全文获取类型
收费全文 | 123篇 |
免费 | 1篇 |
专业分类
化学 | 82篇 |
晶体学 | 2篇 |
力学 | 5篇 |
数学 | 15篇 |
物理学 | 20篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 1篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 12篇 |
2011年 | 10篇 |
2010年 | 16篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 3篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有124条查询结果,搜索用时 13 毫秒
91.
Helio G. Bonacorso Rogério V. Lourega Fernando J. Righi Everton D. Deon Nilo Zanatta Marcos A. P. Martins 《Journal of heterocyclic chemistry》2008,45(6):1679-1686
The synthesis of a novel series of the intermediates N2(N3)‐[1‐alkyl(aryl/heteroaryl)‐3‐oxo‐4,4,4‐trifluoroalk‐1‐en‐1‐yl]‐2‐aminopyridines [F3CC(O)CH?CR1(2? NH?C5H3N)] and 2,3‐diaminopyridines [F3CC(O)CH?CR1(2‐NH2‐3‐NH? C5H3N)], where R1 = H, Me, C6H5, 4‐FC6H4, 4‐CIC6H4, 4‐BrC6H4, 4‐CH3C6H4, 4‐OCH3C6H4, 4,4′‐biphenyl, 1‐naphthyl, 2‐thienyl, 2‐furyl, is reported. The corresponding series of 2‐aryl(heteroaryl)‐4‐trifluoromethyl‐3H‐pyrido[2,3‐b][1,4]diazepin‐4‐ols obtained from intramolecular cyclization reaction of the respective trifluoroacetyl enamines or from the direct cyclocondensation reaction of 4‐methoxy‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 2,3‐diaminopyridine, under mild conditions, is also reported. 相似文献
92.
Jamile Zeni Karine Cence Camila Elis Grando Lídia Tiggermann Rosicler Colet Lindomar A. Lerin Rogério L. Cansian Geciane Toniazzo Débora de Oliveira Eunice Valduga 《Applied biochemistry and biotechnology》2011,163(3):383-392
The aim of this work was to perform the screening of microorganisms, previously isolated from samples of agro-industrial waste and belonging to the culture collection of our laboratory, able to produce polygalacturonases (PG). A total of 107 microorganisms, 92 newly isolated and 15 pre-identified, were selected as potential producers of enzymes with PG activity. From these microorganisms, 20 strains were able to synthesize PG with activities above 3 U mL−1. After the kinetic study, the enzyme activity was increased up to 13 times and the microorganism identified as Aspergillus niger ATCC 9642 and the newly isolated W23, W43, and D2 (Penicillium sp.) after 24 h of fermentation led to PG activities of 30, 41, 43, and 45 U mL−1, respectively. The RAPD analysis demonstrated that the selected strains differs genetically, indicating that no duplication of strains among them in the experiments for polygalacturonases production was verified. 相似文献
93.
Sensato FR Custodio R Longo E Safont VS Andres J 《The Journal of organic chemistry》2003,68(15):5870-5874
The molecular mechanism for the oxidation of sulfides to sulfoxides and subsequent oxidation to sulfones by diperoxo, MoO(O(2))(2)(OPH(3)) (I), and monoperoxo, MoO(2)(O(2))(OPH(3)) (II), complexes of molybdenum was studied using density functional calculations at the b3lyp level and the transition state theory. Complexes I and II were both found to be active species. Sulfide oxidation by I or II shows similar activation free energy values of 18.5 and 20.9 kcal/mol, respectively, whereas sulfoxides are oxidized by I (deltaG = 20.6 kcal/mol) rather than by II (deltaG = 30.3 kcal/mol). Calculated kinetic and thermodynamic parameters account for the spontaneous overoxidation of sulfides to sulfones as has been experimentally observed. The charge decomposition analysis (CDA) of the calculated transition structures of sulfide and sulfoxide oxidations revealed that I and II are stronger electrophilic oxidants toward sulfides than they are toward sulfoxides. 相似文献
94.
Vera Aparecida de Oliveira Tiera Marcio José Tiera Neide Aparecida Blaz Vieira Bruno Rochetti do Amaral Rogério Zambelli Pires 《Journal of Dispersion Science and Technology》2013,34(8):1121-1128
The interaction between cationic surfactants and isopropylacrylamide-acrylic acid-ethyl methacrylate (IPA:AA:EMA) terpolymers has been investigated using steady-state fluorescence and spectrophotometric measurements to assess the effect of the polymer composition on the aggregation process and terpolymers’ thermosensitivities. Micropolarity studies using pyrene show that the interaction of cationic surfactants with IPA:AA:EMA terpolymers occurs at surfactant concentrations much smaller than that observed for the pure surfactant in aqueous solution. The critical aggregation concentration (CAC) values decrease with both the hydrocarbon length of the surfactant and the content of ethyl methacrylate. These results were interpreted as a manifestation of the increasing contribution of attractive hydrophobic and electrostatic forces between negatively charged polymer chains and positively charged surfactant molecules. The increase of ethyl methacrylate in the copolymers lowers the CAC due to the larger hydrophobic character of the polymer backbone. The cloud point determination reveals that the lower critical solution temperatures (LCST) depend strongly on the copolymer composition and surfactant nature. The binding of surfactants molecules to the polymer chain screens the electrostatic repulsion between the carboxylic groups inducing a conformational transition and the dehydration of the polymer chain. 相似文献
95.
Fabiana Fernandes de Santana e Silva Cardoso Isabela Costa César Iram Moreira Mundim Leonardo de Souza Teixeira Enikson Pontes da Silva Ricardo Rodrigues Bonfim Sandro Antônio Gomes Denys Pires Ferreira Aderimar Rogério Batista Lopes Helifas Duarte Pascoal Weidson Carlo de Souza Gerson Antônio Pianetti 《Biomedical chromatography : BMC》2013,27(11):1457-1462
A new method was developed for the quantitation of 3‐α‐hydroxy tibolone, in human plasma, after oral administration of a tablet formulation containing tibolone (2.5 mg). 3‐α‐Hydroxy tibolone was extracted by a liquid–liquid procedure, using cyproterone acetate as internal standard and chlorobutane as extraction solvent. After extraction, samples were submitted to a derivatization step with p‐toluenesulfonyl isocyanate. A mobile phase consisting of acetonitrile and water (72:28 v/v) was used and chromatographic separation was achieved using Agilent XDB C18 column (100 × 4.6 mm i.d.; 5 µm particle size), at 40°C. Mass spectrometric detection was performed using atmospheric pressure chemical ionization in negative mode for 3‐α‐hydroxy tibolone and in positive mode for cyproterone acetate. The fragmentation transitions were m/z 510.2 → m/z 170.1 and m/z 417.0 → m/z 357.1 for 3‐α‐hydroxy tibolone and cyproterone acetate, respectively. Calibration curves were constructed over the range 100–30,000 pg/mL and the method was shown to be specific, precise and accurate, with a mean recovery rate of 94.2% for 3‐α‐hydroxy tibolone. No matrix effect or carry‐over was detected in the samples. The validated method was applied in a pharmacokinetic study with a tibolone formulation in healthy female volunteers. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
96.
M. Fernanda P. Costa Rogério B. Francisco Ana Maria A. C. Rocha Edite M. G. P. Fernandes 《Journal of Optimization Theory and Applications》2017,174(3):875-893
This paper proposes a self-adaptive penalty function and presents a penalty-based algorithm for solving nonsmooth and nonconvex constrained optimization problems. We prove that the general constrained optimization problem is equivalent to a bound constrained problem in the sense that they have the same global solutions. The global minimizer of the penalty function subject to a set of bound constraints may be obtained by a population-based meta-heuristic. Further, a hybrid self-adaptive penalty firefly algorithm, with a local intensification search, is designed, and its convergence analysis is established. The numerical experiments and a comparison with other penalty-based approaches show the effectiveness of the new self-adaptive penalty algorithm in solving constrained global optimization problems. 相似文献
97.
98.
Camargo Luan Pereira Lucilha Adriana Campano Gomes Guilherme Augusto Barros Liberatti Vanessa Rocha Andrello Avacir Casanova da Silva Paulo Rogério Catarini Dall’Antonia Luiz Henrique 《Journal of Solid State Electrochemistry》2020,24(8):1935-1950
Journal of Solid State Electrochemistry - Photoelectrodegradation of dyes using semiconductors under visible light is currently a major research topic. In this work, copper pyrovanadate (Cu2V2O7)... 相似文献
99.
100.
Dian M.B. Ribeiro Marina Ritter Alexander O. Souza Rogério A. Freitag Marília D. Farias Alex F.C. Flores Alynne A. Souto Claiton L. Lencina Claudio M.P. Pereira 《Ultrasonics sonochemistry》2013,20(1):99-102
This work describes the ultrasound-assisted regeneration of aldehydes from oximes in ethanol and phosphoric acid as mediator of the reaction. The large scale regeneration of benzaldehyde was shown under similar conditions. The products were isolated in good yields after short reaction times under mild conditions. 相似文献