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Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Costa I Cremaldi LM Darling C Denisenko K Fernandez A Gagnon P Gerzon S Gobel C Gounder K Granite D Halling AM Herrera G Hurvits G James C Kasper PA Kondakis N Kwan S Langs DC Leslie J Lichtenstadt J Lundberg B Manacero A MayTal-Beck S Meadows B de Mello Neto JR Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV 《Physical review letters》1996,76(3):364-367
183.
B. Abad‐García S. Garmón‐Lobato L.A. Berrueta B. Gallo F. Vicente 《Journal of mass spectrometry : JMS》2009,44(7):1017-1025
Fifteen flavonoid O‐diglycosides with different interglycosidic linkage isomery and glycosylation position have been studied in order to analyze their fragmentation patterns. Initial separation was carried out using high performance liquid chromatography with diode array detection (HPLC/DAD) coupled to an electrospray ionization (ESI) interface and a triple quadrupole mass spectrometer. Some useful differences in their MS spectra have been found and discussed. As it has already been reported, [Y*]+/[Y0]+ ratio for flavanones and [Y1]+/[Y0]+ ratio for other flavonoids is specific for each isomeric interglycosidic linkage. In this work it has also been observed that the abundance of these ions is dependent on the position of glycosylation. On the basis of these differences, systematic guidelines for our experimental conditions have been proposed for the differentiation of not only isomeric interglycosidic linkage but also glycosylation position using collision‐induced dissociation MS/MS (CID‐MS/MS) spectra in positive mode. These results have been successfully applied for the characterization of three diglycosyl flavonoids found in Citrus fruit juices and these conclusions have also been extrapolated for characterizing two triglycosides in the same fruits. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Size exclusion chromatographic (SEC) evaluation of secondary mechanisms and column specific resolution, of five solvent/polymer systems in four sets of pure and mixed organic columns packings based on polystyrene/divinylbenzene copolymer, TSK-Gel HHR and TSK-Gel HXL, has been carried out. The combination of columns employed has been: (i) three HHR columns (set A); (ii) two HHR and one HXL column (set B); (iii) one HHR and two HXL columns (set C) and (iv) three HXL columns (set D). Both packings offer similar characteristics (pore size, particle size, efficiency) but some differences have been found when eluting the same systems in different combination of both of them. Values of the chromatographic partition coefficient, Kp, of the volume fraction of the network in the swollen state, 3, and the concentration effect on the retention volume have been related. It can be concluded that the higher the 3, the higher the crosslinking degree and Kp, and the higher the concentration effect on the retention volume for a given solvent/polymer system. We also observe that, in general, a decrease of Kp comes along with an increase of specific resolution, RS, and that the sets of mixed columns show lower secondary effects different from pure size exclusion (lower Kp) and higher RS than the two sets of pure HHR or HXL columns.Presented at: International Symposium on Separation and Characterization of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, February 5–7, 2003 相似文献
186.
de Farias RF de Souza JM de Melo JV Airoldi C 《Journal of colloid and interface science》2000,227(1):147-151
Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press. 相似文献
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In the present study, the kinetics and thermodynamics of the successful one-pot synthesis of arene-based PCP/PNP pincer ligands by less nucleophilic secondary halophosphines (mono/bis(phosphinomethyl)benzene/pyridine) via SN2 reactions, which have been recently developed by Shih and Ozerov (Organometallics 34:4591, 35), have been studied. By utilizing different substituents on the target molecules, the impact of such modifications has been investigated both in gas phase and in solution. Performed calculations showed clear dependence of the activation energy and reaction rates on the presence of lithium in the structure. Additionally, the nature of the leaving group was observed to influence the favorability of the reaction. Similarly, the type of the halogen on both substrate and nucleophile had impact on the reaction rates, with the use of iodide leading to the observation of the fastest reaction rates. The solvent used was also noted to exert considerable influence on the thermodynamics and kinetics of the reactions. However, the R group in the nucleophile (XPR2) showed no significant inductive effect on the activation energy, but a slight steric effect could be observed. 相似文献
190.
Abad JM Mertens SF Pita M Fernández VM Schiffrin DJ 《Journal of the American Chemical Society》2005,127(15):5689-5694
This paper presents an efficient strategy for the specific immobilization of fully functional proteins onto the surface of nanoparticles. Thioctic acid-derivatized gold clusters are used as a scaffold for further stepwise modification, leading to a cobalt(II)-terminated ligand shell. A histidine tag introduced by genetic engineering into a protein is coordinated to this transition metal ion. The specific immobilization has been demonstrated for the cases of a genetically engineered horseradish peroxidase and ferredoxin-NADP(+) reductase, confirming the attachment of the fully functional proteins to the Co(II)-terminated nanointerface. The absence of nonspecific protein adsorption and the specificity of the binding site have been verified using several analogues of the enzymes without the histidine tag. 相似文献