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111.
Miguel A. Aguilar-Méndez Eduardo San Martín-Martínez Lesli Ortega-Arroyo Georgina Cobián-Portillo Esther Sánchez-Espíndola 《Journal of nanoparticle research》2011,13(6):2525-2532
Colloidal silver nanoparticles were synthesized by reducing silver nitrate solutions with glucose, in the presence of gelatin
as capping agent. The obtained nanoparticles were characterized by means of UV–Vis spectroscopy, transmission electron microscopy
(TEM), and Fourier transform infrared (FTIR) spectroscopy. The response surface methodology (RSM) was also used to determine
the influence of the variables on the size of the nanoparticles. The antifungal activity of the silver nanoparticles was evaluated
on the phytopathogen Colletotrichum gloesporioides, which causes anthracnose in a wide range of fruits. The UV–Vis spectra indicated the formation of silver nanoparticles preferably
spherical and of relatively small size (<20 nm). The above-mentioned was confirmed by TEM, observing a size distribution of
5–24 nm. According to RSM the synthesis variables influenced on the size of the silver nanoparticles. By means of FTIR spectroscopy
it was determined that gelatin, through their amide and hydroxyl groups, interacts with nanoparticles preventing their agglomeration.
The growth of C. gloesporioides in the presence of silver nanoparticles was significantly delayed in a dose dependent manner. 相似文献
112.
Rafael Sanchez-Lara Lelio de la Cruz-May Grethell Georgina Perez-Sanchez Ricardo Cuenca-Alvarez Jose Alfredo Alvarez-Chavez 《Optical Review》2014,21(5):500-504
The evolution of the nth analytical solutions of commonly used Raman equations, analyzed by numerical simulation and experimentally, is reported. In the experiment, a 1 km undoped single-mode fiber was pumped with an ytterbium doped fiber laser system (FL) in continuous wave regime at 1064 nm in a free running configuration. We showed that it is possible to obtain up to the nth power thresholds and the maximum power for each Stokes wave by using compact analytical solutions as a first approximation in a simple, quick process. 相似文献
113.
Georgina Sandoval Ivanna Rivera Karla A. Barrera-Rivera Antonio Martínez-Richa 《Macromolecular Symposia》2010,289(1):135-139
Summary: Enzyme-catalyzed synthesis of biopolymers is a growing area of green chemistry because the exquisite selectivity and control of the polymer structure allowed by the enzymatic synthesis. In addition, the metal traces of chemical catalysts are avoided, being this feature particularly useful in biomedical applications. Lipases are remarkable catalysts and they are efficient in the synthesis of several kinds of biopolymers. However, one of the limitations of the industrial application of lipase-catalyzed polymerizations is the cost of commercial immobilized lipases. To overcome this drawback, in this work we present some cheap and simple strategies to produce and obtain immobilized lipases, as well as some examples of biopolymer synthesis using these tailored lipases. 相似文献
114.
We have studied the oxidation of benzyl alcohols by nitrous and nitric acid in sulfuric acid media. The oxidation by nitrous acid is rapid and has an activation energy of 10.6 ± 0.8 kcal mol?1. A Hammett plot of logk2 vs. σ+ is linear with a ρ value of ?1.4. The oxidation by nitric acid in sulfuric acid media is autocatalytic. From the kinetic and product analyses, it is concluded that a common oxidant, the nitrosonium ion is involved when either nitrous or nitric acid is used. A mechanism is proposed which involves the abstraction of hydride from the alcohols as the rate determining step. It is demonstrated that the autoxidation of the alcohols is catalyzed by nitrous acid or nitric oxide. 相似文献
115.
Jayasooriya UA Grinter R Hubbard PL Aston GM Stride JA Hopkins GA Camus L Reid ID Cottrell SP Cox SF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(8):2266-2276
Muon Spin Relaxation and Avoided Level Crossing (ALC) measurements of ferrocene are reported. The main features observed are five high field resonances in the ALC spectrum at about 3.26, 2.44, 2.04, 1.19 and 1.17 T, for the low-temperature phase at 18 K. The high-temperature phase at 295 K shows that only the last feature shifted down to about 0.49 T and a muon spin relaxation peak at about 0.106 T which approaches zero field when reaching the phase transition temperature of 164 K. A model involving three muoniated radicals, two with muonium addition to the cyclopentadienyl ring and the other to the metal atom, is postulated to rationalise these observations. A theoretical treatment involving spin-orbit coupling is found to be required to understand the Fe-Mu adduct, where an interesting interplay between the ferrocene ring dynamics and the spin-orbit coupling of the unpaired electron is shown to be important. The limiting temperature above which the full effect of spin-orbit interaction is observable in the muSR spectra of ferrocene was estimated to be 584 K. Correlation time for the ring rotation dynamics of the Fe-Mu radical at this temperature is 3.2 ps. Estimated electron g values and the changes in zero-field splittings for this temperature range are also reported. 相似文献
116.
Alexander AM Bria M Brunklaus G Caldwell S Cooke G Garety JF Hewage SG Hocquel Y McDonald N Rabani G Rosair G Smith BO Spiess HW Rotello VM Woisel P 《Chemical communications (Cambridge, England)》2007,(22):2246-2248
A ferrocene-functionalised ureidopyrimidinone has been synthesised that can signal the solvent-induced tautomerism of the dimeric 4[1H]-pyrimidinone form to the monomeric 6[1H]-pyrimidinone form. 相似文献
117.
David Ellis Georgina M. Rosair Susan Robertson Alan J. Welch 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):1399-1400
In the title compound, C16H25B9S, there are two crystallographically independent molecules, and the conformations of the phenyl and SMe2 substituents indicate some intramolecular steric crowding. The bridging H atom is asymmetrically disposed. The title compound is a precursor to a crowded vertex‐labelled nido carborane ligand important in establishing the mechanism of isomerization of icosahedral heteroboranes. 相似文献
118.
Melissa D'Ascenzio Kathryn M. Pugh Rebecca Konietzny Georgina Berridge Cynthia Tallant Shaima Hashem Octovia Monteiro Jason R. Thomas Markus Schirle Stefan Knapp Brian Marsden Oleg Fedorov Chas Bountra Benedikt M. Kessler Paul E. Brennan 《Angewandte Chemie (International ed. in English)》2019,58(4):1007-1012
119.
Inés Nicolás‐Vázquez Guadalupe Pérez‐Caballero Annia Galano Jiménez Georgina Guzmán Rangel René Miranda Ruvalcaba 《International journal of quantum chemistry》2013,113(8):1107-1115
A novel azocompound with two nonequivalents azo groups, 2‐(4‐phenylazoaniline)‐4‐phenylphenol, was synthesized and characterized by spectroscopic and computational analysis. An intramolecular hydrogen bonding (HB), ? O1? H1 ··· N1? , involving the ? N1?N2? group and the proton in a neighbor hydroxyl moiety, was identified. It was found responsible for a characteristic π‐conjugated H1? O1? C18?C13? N2?N1? six‐membered cyclic fragment. It is worth noting that this azo group is involved in an azo‐hydrazo equilibrium, being the azo form the most stable one. This resonance‐assisted HB was characterized using the OH‐related infrared bands and the corresponding signals in 1H NMR. In addition, conformational studies and geometrical and electronic parameter calculations were performed using the density functional theory, at B3LYP/6‐311++G** level. Bond and ring critical points were identified using the atoms in molecules theory, which allowed confirming the intramolecular HB. The second azo‐group cannot be involved in HB, but it also presents two stereoisomerics forms corresponding to cis (Z) and trans (E) configurations, with the later being the one with the lowest energy. © 2013 Wiley Periodicals, Inc. 相似文献
120.
Georgina M. S. Alves Júlia M. C. S. Magalhães Helena M. V. M. Soares 《Electroanalysis》2013,25(2):493-502
The simultaneous determination of Zn and Cu by anodic stripping voltammetry (ASV) is prone to errors due to the formation of Cu‐Zn intermetallic compounds. The main aim of this work was to study the possibility of simultaneous determination of Zn and Cu, together with Hg and Pb, using a mercury‐free solid gold microwire electrode. The multi‐element detection was carried out by differential pulse anodic stripping voltammetry (DPASV), in a chloride medium (0.5 M NaCl) under moderate acid conditions (HCl 1.0 mM) in the presence of oxygen, where the gold microwire electrode was used as stationary or vibrating working electrode during the deposition step. Under these conditions, no formation of Cu‐Zn intermetallic compounds were found for concentrations usually determined in surface waters. In addition, quantification of Zn and Cu, together with Hg and Pb, can be performed in a wide range of concentrations (about two orders of magnitude) using the same sample, in a very short period of time. The detection limits for Cu, Hg, Pb and Zn, using a vibrating electrode and 30 s of deposition time, were 0.2 µg L?1 for Hg, 0.3 µg L?1 for Pb and 0.4 µg L?1 for Zn and Cu, respectively. The proposed DPASV methods were successfully applied to the determination of Cu, Hg, Pb, and Zn in a certified reference fresh water, river, tap and coastal sea waters. These results proved the applicability and versatility of the proposed methods for the analysis of different water matrices and showed that a gold microwire electrode is a suitable choice to determine simultaneously Zn and Cu. 相似文献