全文获取类型
收费全文 | 111篇 |
免费 | 3篇 |
专业分类
化学 | 77篇 |
力学 | 1篇 |
数学 | 12篇 |
物理学 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 10篇 |
2012年 | 16篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 8篇 |
2003年 | 2篇 |
2002年 | 4篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有114条查询结果,搜索用时 31 毫秒
31.
Carla Di Teodoro Massimiliano Aschi Andrea Amadei Danilo Roccatano Francesco Malatesta Luca Ottaviano 《Chemphyschem》2005,6(4):681-689
A theoretical study of the conformational properties of a small heme peptide in aqueous solution is carried out by classical, long-timescale molecular dynamics simulations. The electronic properties of this species, that is, the relative energies of its excited electronic states and the redox potential, are reproduced and related to the conformational behavior using the perturbed matrix method and basic statistical mechanics. Our results show an interesting coupling between the conformational transitions and the electronic properties. These investigations, beyond the biophysically relevant results addressing the long-standing question of the actual role of the enzyme structure on the enzyme activity, are also of some methodological interest since they offer a further computational perspective for including the electronic degrees of freedom into the modeling of rather complex molecular systems. 相似文献
32.
We investigate the-nucleus potential in the framework of a relativistic mean field approximation. As input for the elementaryN interaction we supplement the-repulsion by the exchange of an effective, complex-meson to account for theN N conversion. As the main result we find that the strength of ths absorptive central potential is smaller than the corresponding real part, whereas in the spin-orbit interaction, which is expected to be much weaker than for a nucleon, the imaginary component dominates.This work was partially supported by CNPq, FINEP (Brazil) and by the Bilateral Cooperation W. Germany — Brazil (KFA — CNPq). 相似文献
33.
34.
Dr. Manoj B. Gawande Dr. Anuj K. Rathi Prof. Dr. Paula S. Branco Dr. Isabel D. Nogueira Prof. Dr. Alexandre Velhinho Dr. Janhavi J. Shrikhande Dr. Utkarsha U. Indulkar Prof. Dr. Radha V. Jayaram Dr. C. Amjad A. Ghumman Dr. Nenad Bundaleski Prof. Orlando M. N. D. Teodoro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12628-12632
35.
36.
Vignaduzzo SE Maggio RM Castellano PM Kaufman TS 《Analytical and bioanalytical chemistry》2006,386(7-8):2239-2244
Two new analytical methods have been developed as convenient and useful alternatives for simultaneous determination of hydrochlorothiazide
(HCT) and propranolol hydrochloride (PRO) in pharmaceutical formulations. The methods are based on the first derivative of
ratio spectra (DRS) and on partial least squares (PLS) analysis of the ultraviolet absorption spectra of the samples in the
250–350-nm region. The methods were calibrated between 8.7 and 16.0 mg L−1 for HCT and between 14.0 and 51.5 mg L−1 for PRO. An asymmetric full-factorial design and wavelength selection (277–294 nm for HCT and 297–319 for PRO) were used
for the PLS method and signal intensities at 276 and 322 nm were used in the DRS method for HCT and PRO, respectively. Performance
characteristics of the analytical methods were evaluated by use of validation samples and both methods showed to be accurate
and precise, furnishing near quantitative analyte recoveries (100.4 and 99.3% for HCT and PRO by use of PLS) and relative
standard deviations below 2%. For PLS the lower limits of quantification were 0.37 and 0.66 mg L−1 for HCT and PRO, respectively, whereas for DRS they were 1.15 and 3.05 mg L−1 for HCT and PRO, respectively. The methods were used for quantification of HCT and PRO in synthetic mixtures and in two commercial
tablet preparations containing different proportions of the analytes. The results of the drug content assay and the tablet
dissolution test were in statistical agreement (p < 0.05) with those furnished by the official procedures of the USP 29. Preparation of dissolution profiles of the combined
tablet formulations was also performed with the aid of the proposed methods. The methods are easy to apply, use relatively
simple equipment, require minimum sample pre-treatment, enable high sample throughput, and generate less solvent waste than
other procedures.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
37.
Hector Rene Vega-Carrillo Arturo Ortíz-Hernandez Victor Martin Hernandez-Davila Berenice Hernández-Almaraz Teodoro Rivera Montalvo 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(2):537-540
Neutron spectrum and ambient dose equivalent has been measured around two 10 MV linear accelerators. Measurements were carried
out in Mevatron and Primus model linacs, both made by Siemens. Main differences between those models are the beam collimator
and the vault room. Here, Bonner sphere spectrometer with a passive thermal neutron detector has been utilized to measure
the neutron spectrum inside the vault. Using an active detector the neutron spectrum was measured at the vault’s door of both
accelerators. With a neutron area monitor the dose equivalent was measured by the door at both vault doors. Neutron strength,
total fluence rate and ambient dose equivalent were compared, from this was found that shielding conditions are better in
the Primus model. 相似文献
38.
The reaction of N-tosyltryptamines with thioortho esters, leading to 1-thiosubstituted tetrahydro-beta-carbolines under modified Pictet-Spengler conditions, is described. The 1-heterosubstituted beta-carbolines furnished 1-substituted beta-carbolines upon reaction with Grignard reagents and silyl derivatives under Lewis acid promotion. [reaction: see text] 相似文献
39.
Silvana E. Vignaduzzo Luciana Vera-Candioti Patricia M. Castellano H��ctor C. Goicoechea Teodoro S. Kaufman 《Chromatographia》2011,74(7-8):609-617
A capillary zone electrophoresis method for the simultaneous determination of pridinol mesylate (PRI) and meloxicam (MEL) employing epinastine hydrochloride and piroxicam as internal standards, was developed and optimized employing experimental design and response surface methodologies. The separation was optimally achieved in less than 2 min at 30 kV in an uncoated fused-silica capillary (41.4 cm × 75 ??m I.D.), employing an 18 mmol L?1 sodium phosphate buffer solution (pH 5.90) at 25 °C. Samples were injected in hydrodynamic mode (50 mbar, 5 s) and the analytes were spectrophotometrically detected at 200 nm. Method robustness was demonstrated by ANOVA of determinations performed under conditions slightly different from the optimum. The method was validated regarding separation selectivity (peak purity factors > 0.99), linearity and range (PRI = 17.6?C31.4 mg L?1; MEL = 66.5?C122.5 mg L?1), accuracy (PRI = 100.2?C101.9%; MEL = 98.9?C100.7%) and precision. The RSD values obtained were ??1.3% for injection repeatability and ??1.9% for intra-day precision. The limits of detection (1.0 and 0.9 mg L?1) and quantification (3.3 and 16.5 mg L?1) of PRI and MEL, respectively, were also determined. The method was successfully applied to the determination of both drugs in three brands of tablet formulations. No statistically significant differences were observed when these results were compared with those of a RP-HPLC method. 相似文献
40.
Saviour A. Umoren Mauro J. Banera Teodoro Alonso-Garcia Claudio A. Gervasi Maria V. Mirífico 《Cellulose (London, England)》2013,20(5):2529-2545
The efficiency of chitosan (a naturally occurring polymer) as a corrosion inhibitor for mild steel in 0.1 M HCl was investigated by gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopy measurements, scanning electron microscopy, and UV–visible analysis. The polymer was found to inhibit corrosion even at a very low concentration. Inhibition efficiency increases with a rise in temperature up to 96 % at 60 °C and then drops to 93 % at 70 °C, while it slightly increases with an increase in chitosan concentration. Polarization curves indicate that chitosan functions as a mixed inhibitor, affecting both cathodic and anodic partial reactions. Impedance results indicate that chitosan was adsorbed on the metal/solution interface. Adsorption of chitosan at the mild steel surface is found to be in agreement with Langmuir adsorption isotherm model. Chemical adsorption is the proposed mechanism for corrosion inhibition considering the trend of protection efficiency with temperature. Calculated kinetic and thermodynamic parameters corroborate the proposed mechanism. 相似文献