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41.
Acidity Constant (pKa) Calculation of Large Solvated Dye Molecules: Evaluation of Two Advanced Molecular Dynamics Methods 下载免费PDF全文
Thierry De Meyer Prof. Bernd Ensing Sven M. J. Rogge Prof. Karen De Clerck Prof. Evert Jan Meijer Prof. Veronique Van Speybroeck 《Chemphyschem》2016,17(21):3447-3459
pH‐Sensitive dyes are increasingly applied on polymer substrates for the creation of novel sensor materials. Recently, these dye molecules were modified to form a covalent bond with the polymer host. This had a large influence on the pH‐sensitive properties, in particular on the acidity constant (pKa). Obtaining molecular control over the factors that influence the pKa value is mandatory for the future intelligent design of sensor materials. Herein, we show that advanced molecular dynamics (MD) methods have reached the level at which the pKa values of large solvated dye molecules can be predicted with high accuracy. Two MD methods were used in this work: steered or restrained MD and the insertion/deletion scheme. Both were first calibrated on a set of phenol derivatives and afterwards applied to the dye molecule bromothymol blue. Excellent agreement with experimental values was obtained, which opens perspectives for using these methods for designing dye molecules. 相似文献
42.
Veronique Gilard Myriam Malet-martino Robert Martino Ulf Niemeyer 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract In an attempt to clarify the alkaline hydrolytic pathway of the antitumor agent, cyclophosphamide (CP), the time course of its degradation was monitored by 31P NMR in 0.5 M KOH solution. After 16 hr at 25°C. 70% of CP is hydrolyzed (t½ 9 hr) leading to a mixture of 8 phosphorated compounds. among them only 4 represented more than 5% of the initial CP. The chemical shifts and the intensities of these compounds were as follows: 1 1 .1 ppm. 30% of the initial CP (compound 1); 9.5 ppm, 12% (compound 2); 6.4 ppm, 9% (unknown) and 4.8 ppm, 9% (compound 3). The structures of compounds 1–3 were identified by NMR (13C and IH) and mass spectrometry after their isolation. The major degradation compound formed, the nine-membered ring compound I, was also observed during CP hydrolysis at neutral or moderately acid pHsill and was detected in urine of patients treated with CP[2] Compounds 2 and 3 were also formed during the hydrolysis of compound I in 0.5 M KOH solution. Based on the formation in time of the 31P NMR signals in KOH solutions of CP and compound I, the following scheme was established for the major degradation alkaline pathway of CP. 相似文献
43.
Veronique Gilard Myriam Malet-martino Robert Martino Ulf Niemeyer 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract I fosfamide (IF) is an alkylating antitumor agent used in the treatment of solid tumors. Up to 50% of IF administered to patients undergoes an oxidative N-dealkylation reaction resulting in the loss or one, other or both chloroethyl side chain(s) to produce 2- or 3-dechloioethylIF (ZDCIF, 3DCIF) or 2,3-didechloroethyllF (DDCIF). The hydrolytic pathway of these four oxazaphosphorines has been studied earlier but only at acidic and neutral pHs[l] In the present work, we monitored their time courses of hydrolysis at basic pHs using phosphorus-3 1 NMR. The structures of the compounds formed were determined by NMR (13C and 1H) and mass spectrometry. The results are reported in the following scheme. 相似文献
44.
45.
Veronique Sinou Julien Fiot Nicolas Taudon Joël Mosnier Maryse Martelloni Sok S. Bun Daniel Parzy Evelyne Ollivier 《Journal of separation science》2010,33(12):1863-1869
In Africa, Mitragyna inermis (Willd.) O. Kuntze (Rubiaceae) is commonly used in traditional medicine to treat malaria. Antimalarial activity is mostly due to the hydromethanolic extract of M. inermis leaves and especially to the main alkaloids, uncarine D and isorhynchophilline. In the present study, we describe for the first time an HPLC method for the simultaneous quantification of uncarine D and isorhynchophylline in biological matrices. SPE was used to extract the components and the internal standard naphthalene from human and pig plasma samples. Chromatographic separation was performed on a C‐18 reversed column at a flow rate of 1 mL/min, using methanol–phosphate buffer (10:90, pH 7), as a mobile phase. Good linearity was observed over the concentration ranges of 0.0662–3.31 μg/mL for uncarine D and 0.0476–2.38 μg/mL for isorynchophylline. The precision was less than 12% and the accuracy was from 86 to 107% without any discrepancy between the two species. Uncarine D and isorhynchophylline recoveries were over 80%. These results allowed the quantification of both uncarine D and isorhynchophylline in pig plasma after intravenous administration of M. inermis extract. 相似文献
46.
Ha-Thi MH Souchon V Hamdi A Métivier R Alain V Nakatani K Lacroix PG Genêt JP Michelet V Leray I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(35):9056-9065
The design of a new class of fluorophores is presented. Some push-pull chromophores (D-pi-A) containing polyphenylethynyl units and a phosphane oxide moiety were efficiently prepared from common intermediates. Straightforward syntheses gave novel one-armed, rod-shaped and three-armed, star-shaped fluorophores. The optical properties of the resulting star-shaped derivatives were evaluated, showed high fluorescence quantum yields, and their excitation induces very efficient charge redistribution. Moreover, thanks to their push-pull character, the molecules exhibited significant second-order NLO properties with good transparency, up to 67x10(-30) esu at 1907 nm, with an absorption lambdamax at 369 nm. The effect of the donor group and of the number of phenylethynyl arms have been studied in this work. 相似文献
47.
Maria G. Corradini Veronique Stern Thongchai Suwonsichon Micha Peleg 《Rheologica Acta》2000,39(5):452-460
Samples of commercial tomato paste, low fat mayonnaise and mustard about 6–8 mm thick were squeezed to 0.8 mm at various
speeds between 5 mm min−1 and 25 mm min−1 between Teflon-coated parallel plates 127 mm in diameter using an Instron UTM Model 5542. All the log force vs log height
relationships had a clearly identified linear region. This indicated that a dominant squeezing flow regime was achieved at
about 3 mm height, and that the machine has the proper stiffness to perform the tests. The stress level at a pre-selected
height in this region is a measure of consistency, sensitive enough to distinguish between products of different brands. The
residual stress after relaxation for about 2 min was on order of 10–50% of the initial stress, an indication that all three
foods have a considerable structural integrity. In all three products there was a considerable discrepancy between the observed
rate effects and predictions based on a pseudoplastic (power law) model. It could be described by the empirical relation (Fv1 − FR)/(Fv2 − FR)=(V1/V2)m where Fv1 and Fv2 are the forces at the given displacement reached at speeds v1 and v2 respectively, FR is the residual force after relaxation (found to be practically rate independent), and m is a constant of the order of 0.15–0.33,
independent of the compression velocities ratio but characteristic of the food and brand. The calculated elongational viscosity
was not a unique function of biaxial strain rate. To a certain extent, this was probably due to imperfect lubrication. But
it was also a manifestation of these products considerable structural integrity which cannot be accounted for by models developed
for ideal liquids.
Received: 1 November 1999 Accepted: 2 May 2000 相似文献
48.
Simone Veronique Fannang Victor Kuete Celine Mbazoa Djama Marlise Diane J.Dongfack Jean Duplex Wansi Francois Tillequin Elisabeth Seguin Elizabeth Chosson Jean Wandji 《中国化学快报》2011,22(2):171-174
A new friedelane-type triterpene named 3β-hydroxyfriedelane-7,12,22-trione,as well as nine known compounds were isolated from the whole stems of Drypetes laciniata Hutch.(Euphorbiaceae).Their structures were established on the basis of spectroscopic methods.The new triterpene derivative and a known saponin were tested for antimicrobial and antifungal activities and they appeared to be moderate active. 相似文献
49.
50.
Synthesis of poly(2‐oxazoline)s with side chain methyl ester functionalities: Detailed understanding of living copolymerization behavior of methyl ester containing monomers with 2‐alkyl‐2‐oxazolines 下载免费PDF全文
Maarten Vergaelen Bryn D. Monnery Saron Catak Jan C. M. van Hest Veronique Van Speybroeck Richard Hoogenboom 《Journal of polymer science. Part A, Polymer chemistry》2015,53(22):2649-2661
Poly(2‐oxazoline)s with methyl ester functionalized side chains are interesting as they can undergo a direct amidation reaction or can be hydrolyzed to the carboxylic acid, making them versatile functional polymers for conjugation. In this work, detailed studies on the homo‐ and copolymerization kinetics of two methyl ester functionalized 2‐oxazoline monomers with 2‐methyl‐2‐oxazoline, 2‐ethyl‐2‐oxazoline, and 2‐n‐propyl‐2‐oxazoline are reported. The homopolymerization of the methyl ester functionalized monomers is found to be faster compared to the alkyl monomers, while copolymerization unexpectedly reveals that the methyl ester containing monomers significantly accelerate the polymerization. A computational study confirms that methyl ester groups increase the electrophilicity of the living chain end, even if they are not directly attached to the terminal residue. Moreover, the electrophilicity of the living chain end is found to be more important than the nucleophilicity of the monomer in determining the rate of propagation. However, the monomer nucleophilicity can be correlated with the different rates of incorporation when two monomers compete for the same chain end, that is, in copolymerizations. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2649–2661 相似文献