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41.
[reaction: see text] A de novo structural class of chiral amino alcohol catalysts has been identified through a synergistic effort combining novel architectures from [4 + 3] cycloadditions and quantum mechanical interaction field predictions that closely match subsequent experimental measurements. 相似文献
42.
Benedetto Natalini Roccaldo Sardella Federica Ianni María Eugenia García-Rubiño Ana Conejo-García María del Carmen Núñez Miguel Angel Gallo Joaquín María Campos 《Chromatographia》2013,76(9-10):475-482
Three (R,S)-9-(2,3-dihydro-1,4-benzoxathiin-3-ylmethyl)-9H-purine derivatives (1–3) and three (R,S)-9-(2,3-dihydro-1,4-benzoxathiin-2-ylmethyl)-9H-purine derivatives (4–6) showed relevant activity against human breast cancer cell line MCF-7, when assayed as racemates. The relevant structural analogy among these compounds stimulated us to evaluate and compare their chromatographic behaviour with five polysaccharide-based chiral stationary phases (CSPs). For a column screening purpose, four cellulose-based (Chiralcel OD-H, Chiralpak IB, Lux Cellulose-2, and Sepapak-4; CSPs 1–4, respectively) and an amylose-based (Lux Amylose-2; CSP 5) CSPs were initially assayed by employing the same “standard” eluent mixture. With CSP 2, the performance from “non standard” eluent systems was also evaluated. The different type and position of the substituents onto the carbamate moiety, the coated or immobilized nature of the modified polymer chain, and the different type of winding as well as the eluent composition were found to deeply affect the enantiorecognition mechanism. While the different winding of the polymer and the derived different morphology of the binding cleft in the 2,5-disubstituted chloromethyl phenyl carbamate amylose-based CSP 5 was found to be unsuited to get profitable enantio-discriminations of all the analyzed compounds, CSP 3 and CSP 4 produced the highest α and R S values in the enantioselective analysis of four out of six racemates (that is 1–3 and 6). In CSP 2, the conformational change of the polysaccharide chain upon immobilization produced a profound influence on the chromatographic behaviour of compounds 1–6. A relevant improvement of the enantioresolution quality of CSP 2 was obtained when used in combination with “non standard” solvents as constituents of the mobile phase mixture. 相似文献
43.
JC Wolff S Monte N Haskins D Bell 《Rapid communications in mass spectrometry : RCM》1999,13(18):1797-1802
Structural analysis of minor components in mixtures is a vital requirement in the development of any pharmaceutical compound. Mass spectrometry is uniquely able to give this kind of information on the trace amounts of material present as minor impurities in a drug substance. In this study we show that a combination of mass spectrometric analysers with different characteristics is an even more powerful approach with a higher chance of establishing a potential structure. In particular the advent of analysers capable of accurate mass measurement on small amounts of material has enabled structures to be proposed in situations where previously no real conclusions could be made. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
44.
In this paper the exact solution of the non-symmetric matrixRiccati equation with analytic coefficients is approximatedby a rational matrix function with a prefixed accuracy. Thisrational matrix function is locally defined as the exact solutionof a Riccati problem with matrix polynomial coefficients obtainedby truncation of the Taylor expansions of the matrix coefficientsof the original problem. 相似文献
45.
Natalini B Sardella R Gioiello A Rosatelli E Ianni F Camaioni E Pellicciari R 《Analytical and bioanalytical chemistry》2011,401(1):267-274
In a line of research focused on the design, synthesis and development of new bile acid-based compounds, the physico-chemical
profile of the molecules must be thoroughly explored and analyzed. In this scenario, a fast and reliable information on the
critical micellar concentration (CMC) of specific compounds through a profitable chromatographic parameter can be of aid to
rationally direct the synthesis of new molecular entities, mainly during the early stages of the drug-discovery process. The
derived ‘chromatographic hydrophobicity index’ (CHI), usually employed for a fast access to the log P/log D value of physico-chemically diverse compounds and obtained via RP-gradient elution, was for the first time engaged in the
bile acid field. Accordingly, 14 unconjugated bile acids harboured with a different number, position and orientation of hydroxy
groups, as well as other substituents onto the steroidal backbone and side chain, were selected to build up a calibration
curve. Such a collection of compounds was rationally assembled in order to manage an almost continuous range of CMC values
(spanning the spectrophotometrically obtained CMCs between 5 and 25 mM). A high degree of correlation between CMC and CHI
values was obtained (R
2 and cross-validated R
xv2 of the pCMC vs CHI plot equal to 0.975 and 0.966, respectively). A selected new subset of five confidential research bile
acids with experimental CMCs in the range 6–19 mM was finally recruited to validate the proposed method. The high statistical
quality of the established mathematical model turned out into a very appreciable predictive power. 相似文献
46.
The successful enantioseparation of five 6-desfluoroquinolones with three polysaccharide-based stationary phases (namely, the cellulose-based Chiralpak IB and the two amylose-based Chiralpak AD-H and Lux Amylose-2) is herein described. The investigated species differ for the nature of substituents and/or the position of the stereogenic centre on the quinolone scaffold.The effect on the enantioseparation performance exerted by the different morphology of the cellulose-based and amylose-based polymers, was systematically evaluated for all compounds. In this frame, the impact of alternative alcoholic (ethanol, 2-ethoxyethanol, methanol, 2-propanol) and acidic (acetic, methanesulfonic and trifluoroacetic acid) modifiers as well as of a “non-standard” solvent (chloroform), was investigated in normal phase conditions along with the stereo-electronic peculiarities of the selected polymers. While 7-[4-(1,3-benzothiazol-2-yl)-2-methyl-1-piperazinyl]-1-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylic acid (1) was enantioresolved with conventional normal-phase conditions by means of the largely employed amylose-based Chiralpak AD-H column, the recruitment of a bulky alcohol (2-ethoxyethanol) succeeded in the enantioresolution of 6-amino-1-methyl-7-[2-methyl-4-(2-pyridinyl)-1-piperazinyl]-4-oxo-1,4-dihydro-3-quinolinecarboxylic acid (2) and 6-amino-1-[1-(hydroxymethyl)propyl]-4-oxo-7-(4-pyridin-2-ylpiperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (3) with the same column. The use of the amylose-based Lux Amylose-2 column, carrying both an electro-withdrawing (chlorine) and an electro-donating (methyl) group on the carbamate residue, allowed to get 6-amino-1-methyl-4-oxo-7-[3-(2-pyridinyl)-1-pyrrolidinyl]-1,4-dihydro-3-quinolinecarboxylic acid hydrochloride (4) enanantioresolved, and 6-amino-1-methyl-4-oxo-7-(3-pyridin-2-ylpiperidin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (5) enantioseparated. 相似文献
47.
This paper presents a numerical method for solving the two‐dimensional unsteady incompressible Navier–Stokes equations in a vorticity–velocity formulation. The method is applicable for simulating the nonlinear wave interaction in a two‐dimensional boundary layer flow. It is based on combined compact difference schemes of up to 12th order for discretization of the spatial derivatives on equidistant grids and a fourth‐order five‐ to six‐alternating‐stage Runge–Kutta method for temporal integration. The spatial and temporal schemes are optimized together for the first derivative in a downstream direction to achieve a better spectral resolution. In this method, the dispersion and dissipation errors have been minimized to simulate physical waves accurately. At the same time, the schemes can efficiently suppress numerical grid‐mesh oscillations. The results of test calculations on coarse grids are in good agreement with the linear stability theory and comparable with other works. The accuracy and the efficiency of the current code indicate its potential to be extended to three‐dimensional cases in which full boundary layer transition happens. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
48.
49.
Luna Pollini Francesca Blasi Federica Ianni Luca Grispoldi Simone Moretti Alessandra Di Veroli Lina Cossignani Beniamino Terzo Cenci-Goga 《Molecules (Basel, Switzerland)》2022,27(6)
Currently, there is an increasing interest to valorise agri-food waste containing bioactive compounds with potential health benefits. In this paper, the recovery of functional molecules from apple pomace, the most abundant by-product of the apple processing industry, was carried out by ultrasound-assisted extraction (UAE) on fresh and freeze-dried samples. UAE extract, obtained by double extraction of freeze-dried apple pomace, was subjected to chromatographic and spectrophotometric characterization. It showed good levels of total phenol content, high antioxidant activity, and interesting antioxidant compounds (quercetin derivatives, chlorogenic acid, phloridzin). Subsequently, freeze-dried apple pomace, containing 40.19% of dietary fibre, was used as a fortifying agent for beef burgers (4% and 8%). The results concerning colour and sensory analysis of the fortified products were graded even better than the control (0%). The improved fibre and phenol content, together with the neutral flavour, represent the most interesting characteristics of fortified burgers. The results confirm that UAE was a successful technique for extracting phenol compounds and that the addition of apple pomace represents a valid approach to increase the health properties and palatability of beef burgers, including for consumers who do not like meat. 相似文献
50.