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61.
Antonio L. Braga Wolmar A. Severo Filho Ricardo S. Schwab Luciano Dornelles Diogo S. Lüdtke 《Tetrahedron letters》2009,50(25):3005-4730
The synthesis of selenium- and tellurium-containing nucleosides, derived from uridine is described herein. These compounds were prepared in a concise and short synthetic route in good yields, by nucleophilic substitution of a tosylate group by organoselenium nucleophiles. 相似文献
62.
HPLC‐DAD for the determination of three different classes of antifungals: method characterization,statistical approach,and application to a permeation study
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Diogo Miron Alini Lange Aline R. Zimmer Paulo Mayorga Elfrides E. S. Schapoval 《Biomedical chromatography : BMC》2014,28(12):1728-1737
This study describes and characterizes methods for high‐performance liquid chromatography diode array detection (HPLC‐DAD) analysis of formulations containing molecules with antifungal activity of three different classes: terbinafine and butenafine (allylamines), miconazole and fluconazole (azoles), and geraniol, neral and geranial (monoterpenes). All methods used the same chromatographic column (RP18), enabling the analysis to be performed in a single batch. The specificity was extensively discussed through the establishment of purity peak methods. The analytical parameters (linearity, precision and accuracy) were calculated and discussed in detail using specific statistical approaches. All substances showed satisfactory results for chromatographic and analytical parameters. Limits of 1.3% to mean repeatability and 2.0% for intermediate precision are suggested as acceptance criteria in validation of methods by HPLC‐DAD, in situations where there is no extensive pretreatment of the samples. The methods proved to be robust and significant factors were discussed regarding their influence on chromatographic parameters (retention time, resolution, tailing factor and column efficiency). Finally, the application of the developed methods was demonstrated by the results of a permeation study of the antifungal agents through bovine hoof membranes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
63.
In this paper we consider time-dependent mean-field games with subquadratic Hamiltonians and power-like local dependence on the measure. We establish existence of classical solutions under a certain set of conditions depending on both the growth of the Hamiltonian and the dimension. This is done by combining regularity estimates for the Hamilton-Jacobi equation based on the Gagliardo-Nirenberg interpolation inequality with polynomial estimates for the Fokker-Planck equation. This technique improves substantially the previous results on the regularity of time-dependent mean-field games. 相似文献
64.
Ricardo Picciochi Hermínio P. Diogo Manuel E. Minas da Piedade 《Journal of Thermal Analysis and Calorimetry》2010,100(2):391-401
Combustion calorimetry, Calvet-drop sublimation calorimetry, and the Knudsen effusion method were used to determine the standard
(p
o = 0.1 MPa) molar enthalpies of formation of monoclinic (form I) and gaseous paracetamol, at T = 298.15 K:
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text cr I ) = - ( 4 10.4 ±1. 3)\text kJ \textmol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) = - ( 4 10.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text g ) = - ( 2 80.5 ±1. 9)\text kJ \textmol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) = - ( 2 80.5 \pm 1. 9){\text{ kJ}}\;{\text{mol}}^{ - 1} . From the obtained
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text cr I ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ cr I}}} \right) value and published data, it was also possible to derive the standard molar enthalpies of formation of the two other known
polymorphs of paracetamol (forms II and III), at 298.15 K:
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text crII ) = - ( 40 8.4 ±1. 3)\text kJ \textmol - 1 \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crII}}} \right) = - ( 40 8.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} and
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text crIII ) = - ( 40 7.4 ±1. 3)\text kJ \textmol - 1 . \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ crIII}}} \right) = - ( 40 7.4 \pm 1. 3){\text{ kJ}}\;{\text{mol}}^{ - 1} . The proposed
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textO 2 \textN,\text g ) \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{O}}_{ 2} {\text{N}},{\text{ g}}} \right) value, together with the experimental enthalpies of formation of acetophenone and 4′-hydroxyacetophenone, taken from the
literature, and a re-evaluated enthalpy of formation of acetanilide,
\Updelta\textf H\textm\texto ( \textC 8 \textH 9 \textON,\text g ) = - ( 10 9. 2 ± 2. 2)\text kJ \textmol - 1 , \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{C}}_{ 8} {\text{H}}_{ 9} {\text{ON}},{\text{ g}}} \right) = - ( 10 9. 2\,\pm\,2. 2){\text{ kJ}}\;{\text{mol}}^{ - 1} , were used to assess the predictions of the B3LYP/cc-pVTZ and CBS-QB3 methods for the enthalpy of a isodesmic and isogyric
reaction involving those species. This test supported the reliability of the theoretical methods, and indicated a good thermodynamic
consistency between the
\Updelta\textf H\textm\texto \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} (C8H9O2N, g) value obtained in this study and the remaining experimental data used in the
\Updelta\textr H\textm\texto \Updelta_{\text{r}} H_{\text{m}}^{\text{o}} calculation. It also led to the conclusion that the presently recommended enthalpy of formation of gaseous acetanilide in
Cox and Pilcher and Pedley’s compilations should be corrected by ~20 kJ mol−1. 相似文献
65.
Alan G. Gonçalves Diogo R. B. Ducatti T. Bruce Grindley M. Eugênia R. Duarte Miguel D. Noseda 《Journal of the American Society for Mass Spectrometry》2010,21(8):1404-1416
We have prepared a number of isomeric red seaweed galactan-derivative sulfated oligosaccharides to determine whether there
were diagnostic differences among the isomeric mass spectra obtained using ESI CID MS/MS (triple quadrupole instrument). Fragmentation
of the single or multicharged molecular ions from di-, tetra-, and hexasaccharides indicated that the relative positioning
of the sulfate groups and type of monosaccharide unit affect the rate of cleavage of the glycosidic bonds. We also performed
a comparative [M-Na]− fragmentation study of positional isomers of sulfated disaccharides that present all four monosulfation possibilities on
the galactopyranosidic ring. In this case, negative-ion ESI CID MS/MS approach gave diagnostic product ions from cross-ring
cleavages along with the same main B1 ion (from sulfated Galp), at m/z 241, for all isomers. The isomeric disaccharides were also submitted to increased spray energy conditions inducing in-source
fragmentation; preformed B1 ions were then fragmented to give similar product ions as those found in [M-Na]− analysis. Evaluation of the relative abundances mainly for cross-ring fragment ions at m/z 138, 139, 151, 153 allowed clear distinction among the members of the disaccharide series. The different ratios for m/z 151/153 ions were consistent with the predominance of m/z 153 being related to the cases when the bond involved in the cleavage process links a sulfated carbon. A quadrupole ion trap
instrument (MSn analysis) was also utilized to compare the results obtained with the triple quadrupole instrument. 相似文献
66.
Amal Al-Kahlout Diogo Vieira César O. Avellaneda Edson R. Leite Michel A. Aegerter Agnieszka Pawlicka 《Ionics》2010,16(1):13-19
Proton-conducting gel polymer electrolytes based on gelatin plasticized with glycerol and containing acetic acid were investigated,
characterized, and applied to electrochromic window. For glycerol contents varying from 7% to 48%, the conductivity of the
uniform and predominantly amorphous gel electrolyte was found to follow a Vogel–Tamman–Fulcher behavior with the temperature.
Typically, for the electrolyte chosen to make 7 × 2 cm2 electrochromic smart window with the configuration: glass/fluor-doped tin oxide (FTO)/WO3/gelatin electrolyte/CeO2–TiO2/FTO/glass and containing 28% of glycerol, the conductivities were found to be of the order of 5 × 10−5 S/cm at room temperature and 3.6 × 10−4 S/cm at 80 °C. The device was characterized by spectroelectrochemical techniques and was tested up to 10,000 cycles showing
a fast coloring/bleaching behavior, where the coloring process was achieved in 10 s and the bleaching in 2 s. The transmission
variation at the wavelength of 550 nm was about 15%. The cyclic voltammograms showed a very good reversibility of the cathodic/anodic
processes, and the charge density was about 3.5 mC/cm2. The memory tests showed that the transmittance in the colored state increased by 8% in 90 min after removing the potential. 相似文献
67.
Diogo P. Moraes Juliana S. F. Pereira Liange O. Diehl Márcia F. Mesko Valderi L. Dressler José Neri G. Paniz Guenter Knapp Érico M. M. Flores 《Analytical and bioanalytical chemistry》2010,397(2):563-570
In this work, three sample preparation methods were evaluated for further halogen determination in elastomers containing high
concentrations of carbon black. Samples of nitrile-butadiene rubber, styrene-butadiene rubber, and ethylene-propylene-diene
monomer elastomers were decomposed using oxygen flask combustion and microwave-induced combustion (MIC) for further Br and
Cl determination by ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively
coupled plasma mass spectrometry (ICP-MS). Extraction assisted by microwave radiation in closed vessels was also evaluated
using water or alkaline solution. Digestion by MIC was carried out using 50 mmol l−1 (NH4)2CO3 as the absorbing solution. The effect of the reflux step was also evaluated. Accuracy was evaluated using certified reference
materials with polymeric matrix composition and by comparison of results using neutron activation analysis. Agreement for
Br and Cl was better than 95% by MIC using 5 min of reflux, and no statistical difference was found using IC, ICP OES, and
ICP-MS for determination of both analytes. For MIC, the relative standard deviation (RSD) was lower than 5%. Using extraction
in closed vessels, a high amount of residues was observed, and recoveries were lower than 45% for both analytes. For oxygen
flask combustion, the agreement was similar using MIC but RSD was higher (20%). The residual carbon content, an important
parameter used to evaluate the digestion efficiency, was always below 1% for MIC. Using MIC, it was possible to digest elastomers
with high efficiency, resulting in a single solution suitable for halogen determination by different techniques. 相似文献
68.
We discuss the application of spline collocation methods to a certain class of weakly singular Volterra integral equations. It will be shown that, by a special choice of the collocation parameters, superconvergence properties can be obtained if the exact solution satisfies certain conditions. This is in contrast with the theory of collocation methods for Abel type equations. Several numerical examples are given which illustrate the theoretical results. 相似文献
69.
Antonio L. Braga Diogo S. Lüdtke Jasquer A. Sehnem Eduardo E. Alberto 《Tetrahedron》2005,61(49):11664-11671
A new series of modular chiral selenium-containing oxazolines has been synthesized from inexpensive and commercially available l-serine and l-aspartic acid. These new compounds were evaluated as chiral ligands in the palladium-catalyzed asymmetric allylic alkylation reaction, furnishing the product in high enantiomeric excess, using Cs2CO3/CH2Cl2 as the base/solvent system. 相似文献
70.
Ivo Paulo Luis Costa Abel Rodrigues Sofia Orikov Sandro Matos Diogo Gonalves Ana Raquel Gonalves Luciana Silva Salom Vieira Joo Carlos Bordado Rui Galhano dos Santos 《Molecules (Basel, Switzerland)》2022,27(1)
Liquefaction of biomass delivers a liquid bio-oil with relevant chemical and energetic applications. In this study we coupled it with short rotation coppice (SRC) intensively managed poplar cultivations aimed at biomass production while safeguarding environmental principles of soil quality and biodiversity. We carried out acid-catalyzed liquefaction, at 160 °C and atmospheric pressure, with eight poplar clones from SRC cultivations. The bio-oil yields were high, ranging between 70.7 and 81.5%. Average gains of bio-oil, by comparison of raw biomasses, in elementary carbon and hydrogen and high heating, were 25.6, 67, and 74%, respectively. Loss of oxygen and O/C ratios averaged 38 and 51%, respectively. Amounts of elementary carbon, oxygen, and hydrogen in bio-oil were 65, 26, and 8.7%, and HHV averaged 30.5 MJkg−1. Correlation analysis showed the interrelation between elementary carbon with HHV in bio-oil or with oxygen loss. Overall, from 55 correlations, 21 significant and high correlations among a set of 11 variables were found. Among the most relevant ones, the percentage of elementary carbon presented five significant correlations with the percentage of O (−0.980), percentage of C gain (0.902), percentage of O loss (0.973), HHV gain (0.917), and O/C loss (0.943). The amount of carbon is directly correlated with the amount of oxygen, conversely, the decrease in oxygen content increases the elementary carbon and hydrogen concentration, which leads to an improvement in HHV. HHV gain showed a strong positive dependence on the percentage of C (0.917) and percentage of C gain (0.943), while the elementary oxygen (−0.885) and its percentage of O loss (0.978) adversely affect the HHV gain. Consequently, the O/C loss (0.970) increases the HHV positively. van Krevelen’s analysis indicated that bio-oils are chemically compatible with liquid fossil fuels. FTIR-ATR evidenced the presence of derivatives of depolymerization of lignin and cellulose in raw biomasses in bio-oil. TGA/DTG confirmed the bio-oil burning aptitude by the high average 53% mass loss of volatiles associated with lowered peaking decomposition temperatures by 100 °C than raw biomasses. Overall, this research shows the potential of bio-oil from liquefaction of SRC biomasses for the contribution of renewable energy and chemical deliverables, and thereby, to a greener global economy. 相似文献