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51.
Pinheiro AV Parola AJ Baptista PV Lima JC 《The journal of physical chemistry. A》2010,114(49):12795-12803
There are numerous reports of coumarin ester derivatives, in particular phosphate esters, as photocleavable cages in biological systems. Despite the comprehensive analysis of the photocleavage mechanism, studies of 4-methylcoumarin caged phosphates and/or nucleotides were always performed at constant pH. In this work, we present the study of the pH effect on the photochemistry of (7-diethylaminocoumarin-4-yl)methyl phosphate (DEACM-P). Fluorescence and photocleavage quantum yields, as well as the fluorescence decay times were measured as a function of the pH. It was found that the pH produces significant changes in the overall photochemical quantum yield of DEACM-P, and the observed changes are complementary to those obtained from the fluorescence quantum yield. Deprotonation of DEACM-HPO(4)(-) to yield DEACM-PO(4)(2-), produces a decrease in the photochemical quantum yield (from 0.0045 to 0.0003) and an increase in the fluorescence quantum yield (from 0.072 to 0.092). Moreover, from the analysis of the decay times, we have also found that hydroxyl ion is not only relevant, but it is mechanistically involved in the photoreaction of DEACM-HPO(4)(-). 相似文献
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In this paper an electromechanical system is analyzed. The existence and asymptotic stability of a periodic orbit are obtained in a mathematically rigorous way as well as an expansion of the period by using an adequate small parameter. For the analytical results the main tool used is the regular perturbation theory. Some results, such as the growing of the period according to some powers of the parameters and the relation 2:1 between the period of the cart, which is a part of the electromechanical system, and the period of the current, are compatible with earlier numerical findings. 相似文献
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Alcântara Antônio F. C. Dos Santos Hélio F. De Almeida Wagner B. Vaz Maria G. F. Pinheiro Luíza M. M. Stumpf Humberto O. 《Structural chemistry》1999,10(5):367-374
2-(2-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide radical 2 and the 2-[2-(N-alkyl)-pyrid-inium] derivatives (3a and 3b) were synthesized and characterized by elemental analysis, melting points, and spectroscopy. The density functional theory (DFT) was used in order to obtain the structures and electronic properties of the new nitronyl nitroxide radicals. Modified reaction procedures of the intermediates are described with better yield and purity of the final products. The magnetic properties of the compounds 2, 3a, and 3b are predicted for the first time using a simple model of charge transference, in the framework of the molecular orbital calculations. The obtained results show that the substituent at the central carbon atom of the imidazoline is important to determine the spin distribution and consequently the nature of the magnetic interaction. 相似文献
57.
Costa EV Pinheiro ML de Souza AD Barison A Campos FR Valdez RH Ueda-Nakamura T Filho BP Nakamura CV 《Molecules (Basel, Switzerland)》2011,16(11):9714-9720
Phytochemical investigation of the branches of Annona foetida Mart. led to isolation from the CH(2)Cl(2) extract of four alkaloids: Atherospermidine (1), described for the first time in this species, liriodenine (2), O-methylmoschatoline (3), and annomontine (4). Their chemical structures were established on the basis of spectroscopic data from IR, MS, NMR (1D and 2D), and comparison with the literature. Compounds 2-4 showed potent trypanocidal effect when evaluated against epimastigote and trypomastigote forms of Trypanosoma cruzi. 相似文献
58.
Lopez Kenneth Pinheiro Silvana Zamora William J. 《Journal of computer-aided molecular design》2021,35(8):923-931
Journal of Computer-Aided Molecular Design - A multiple linear regression model called MLR-3 is used for predicting the experimental n-octanol/water partition coefficient (log PN) of 22... 相似文献
59.
Ana Valria de Oliveira Braz Mariana Carvalho Rodrigues Philippe Alencar Araújo Maia Ana Paula Dantas Pereira Jussara de Lima Silva Francisco Antonio Vieira dos Santos Luiz Everson da Silva Wanderley do Amaral Maura Lins dos Santos Henrique Douglas Melo Coutinho Tomasz Baj Grayna Kowalska Radosaw Kowalski Edinardo Fagner Ferreira Matias 《Molecules (Basel, Switzerland)》2022,27(18)
Commercialized mouthwashes are generally expensive for the most financially vulnerable populations. Thus, several studies evaluate the antimicrobial potential of herbal products, such as essential oils, to reduce the activity of microorganisms in the mouth. The objective of this research was to carry out the chemical characterization and antibacterial activity of the essential oil of Piper mosenii (EOPm), providing data that enable the development of a low-cost mouthwash formulation aimed at vulnerable communities. The analysis of the antibacterial potential and modulator of bacterial resistance was verified by the microdilution method to determine the minimum inhibitory concentration-MIC. The chemical components were characterized by gas chromatography coupled to mass spectrometry, where 23 chemical constituents were detected, with α-pinene, being the major compound. The EOPm showed a MIC ≥ 1024 µg/mL for all bacterial strains used in the tests. When the EOPm modulating activity was evaluated together with chlorhexidine, mouthwash and antibiotics against bacterial resistance, the oil showed a significant synergistic effect, reducing the MIC of the products tested in combination, in percentages between 20.6% to 96.3%. Therefore, it is recommended to expand the tests with greater variation of EOPm concentration and the products used in this research, in addition to the evaluation of toxicity and in vivo tests, seeking the development of a possible formulation of mouthwash accessible to the vulnerable population. 相似文献
60.
Ana C.D. Midões Pedro E. Aranha Mirian P. dos Santos Érica Tozzo Sandra Romera Regina H. de A. Santos Edward R. Dockal 《Polyhedron》2008
The crystal structure, spectroscopic properties and catalytic property of the copper(II) complex, prepared by the reaction between copper(II) diacetate with the bidentate Schiff base, SalAHE (SalAHE = salicylaldehydeimine-1-hydroxyethane), are reported. This complex is able to oxidize 3,5-di-tert-butylcatechol to the respective o-quinone. The oxidation reaction was studied in CH3CN with molecular oxygen at 0, 5, 15 and 25 °C. The progress of the catalytic reaction was followed by gas chromatographic analyses (GC). 相似文献