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761.
Ranajoy Majumdar Prakash Manikwar John M. Hickey Jayant Arora C. Russell Middaugh David B. Volkin David D. Weis 《Journal of the American Society for Mass Spectrometry》2012,23(12):2140-2148
Chromatographic carry-over can severely distort measurements of amide H/D exchange in proteins analyzed by LC/MS. In this work, we explored the origin of carry-over in the online digestion of an IgG1 monoclonal antibody using an immobilized pepsin column under quenched H/D exchange conditions (pH 2.5, 0?°C). From a consensus list of 169 different peptides consistently detected during digestion of this large, ~150?kDa protein, approximately 30?% of the peptic peptides exhibited carry-over. The majority of carry-over originates from the online digestion. Carry-over can be substantially decreased by washing the online digestion flow-path and pepsin column with two wash cocktails: [acetonitrile (5?%)/ isopropanol (5?%)/ acetic acid (20?%) in water] and [2?M guanidine hydrochloride in 100?mM phosphate buffer pH 2.5]. Extended use of this two-step washing procedure does not adversely affect the specificity or activity of the immobilized pepsin column. The results suggest that although the mechanism of carry-over appears to be chemical in nature, and not hydrodynamic, carry-over cannot be attributed to a single factor such as mass, abundance, pI, or hydrophobicity of the peptides. 相似文献
762.
Dibenzyltin bis(2‐ethylhexanoate) 1 (4‐Y C6H4CH2)2Sn(OC(O)R1)2 [Y = H, 1a; MeO, 1b; Cl, 1c; Me, 1d; and R1 = MeCH2CH2CH2CH(Et) ] were synthesized either from the reaction of corresponding dibenzyltin dichlorides with silver 2‐ethylhexanoate or from the reaction of dibenzyltin oxides with 2‐ethylhexanoic acid. Compound 1a was further utilized as a catalyst for the reaction of mono‐ and di‐isocyanates [PhNCO, CH3C6H3‐2,4‐(NCO)2 and OCN(CH2)6NCO] with alcohols (primary, secondary, tertiary, cyclohexcyl, alkyl, allyl, benzyl and aryl) leading to the formation of the corresponding urethanes. The catalytic efficiencies of 1 vis‐à‐vis industrially known organotin catalysts have been determined through kinetic studies for the reaction of PhNCO and n‐BuOH at various temperatures. Compounds 1a, 1c and 1d show higher efficiency than dibutyltin bis(2‐ethylhexanoate). FTIR studies further provide mechanistic insights into the catalytic cycle, which comprises pre‐coordination of isocyanate to tin(IV), formation of stannyl carbamate and generation of dibenzyl(alkoxy)carboxylate as the active catalyst. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
763.
An electrochemical protocol based on reduction is developed to determine methylprednisolone using single-wall carbon nanotubes (SWNTs) modified edge plane pyrolytic graphite electrode (EPPGE). To obtain a good sensitivity, instrumental variables were studied using Square Wave Voltammetry (SWV). The voltammetric results indicate that SWNTs modified EPPGE remarkably enhances the reduction of methylprednisolone which leads to considerable improvement of peak current with shift of peak potential to less negative values. The voltammetric current showed a linear response for methylprednisolone concentration in the range 5-500 nM with a sensitivity of 98 nA nM−1. The limit of detection was estimated to be 4.5 × 10−9 M. The developed method is used for the determination of methylprednisolone in pharmaceutical dosages and human blood plasma samples of patients undergoing treatment with methylprednisolone. The major metabolites present in blood plasma did not interfere with the present investigation as they did not exhibit reduction peak in the experimental range used. A comparison of results with high performance liquid chromatography (HPLC) indicates a good agreement. 相似文献
764.
Synthesis of a number of hitherto unreported 4‐aryloxymethylene‐7‐methyl‐2,3‐dihydropyrano[3,2‐c]pyridine‐5‐ones 4a–h have been achieved in moderate yields by the thermal [3,3]sigmatropic rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐6‐methyl‐2‐pyridone. 相似文献
765.
S. M. Islam Paramita Mondal Sanghamitra Mukherjee Anupam Sigha Roy Asim Bhaumik 《先进技术聚合物》2011,22(6):933-941
A new heterogeneous Schiff base copper(II) complex was prepared by reacting amino‐polystyrene with salicylaldehyde followed by complexation with cupric chloride. The structure of this immobilized complex has been established on the basis of scanning electron microscope (SEM), thermogravimetric analysis (TGA), elemental analysis employing atomic absorption spectroscopy (AAS), and spectrometric methods like diffuse reflectance spectra of solid (DRS) and fourier transform infrared spectroscopy (FTIR). Catalytic activity of this polymer anchored Cu(II) complex was tested by studying the oxidation of cyclohexene, styrene, and benzyl alcohol in the presence of tert‐ butylhydroperoxide as oxidant. Several parameters such as solvent, oxidant, reaction time, reaction temperature, amount of catalyst, and substrates oxidant ratio were varied to optimize the reaction condition. Under optimized reaction conditions, cyclohexene gave a maximum of 74% conversion with three major products 2‐cyclohexene‐1‐one, cyclohexene epoxide, and 2‐cyclohexene‐1‐ol. The conversions of styrene and benzylalcohol proceed with 53% and 77%, respectively. Styrene gives styrene epoxide as the major product while benzylalcohol gives benzaldehyde as the major product. The catalytic results reveal that polymer anchored copper(II) Schiff base complex can be recycled more than five times without much loss in the catalytic activity. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
766.
Does Excited‐State Proton‐Transfer Reaction Contribute to the Emission Behaviour of 4‐Aminophthalimide in Aqueous Media? 下载免费PDF全文
Dr. Dinesh Chandra Khara Sanghamitra Banerjee Prof. Anunay Samanta 《Chemphyschem》2014,15(9):1793-1798
4‐Aminophthalimide (AP) is an extensively used molecule both for fundamental studies and applications primarily due to its highly solvent‐sensitive fluorescence properties. The fluorescence spectrum of AP in aqueous media was recently shown to be dependent on the excitation wavelength. A time‐dependent blue shift of its emission spectrum is also reported. On the basis of these findings, the excited‐state solvent‐mediated proton‐transfer reaction of the molecule, which was proposed once but discarded at a later stage, is reintroduced. We report on the fluorescence behaviour of AP and its imide‐H protected derivative, N‐BuAP, to prove that a solvent‐assisted excited‐state keto–enol transformation does not contribute to the steady‐state and time‐resolved emission behaviour of AP in aqueous media. Our results also reveal that the fluorescence of AP in aqueous media arises from two distinct hydrogen‐bonded species. The deuterium isotope effect on the fluorescence quantum yield and lifetime of AP, which was thought to be a reflection of the excited‐state proton‐transfer reaction in the system, is explained by considering the difference in the influence of H2O and D2O on the nonradiative rates and ground‐state exchange of the proton with the solvent. 相似文献
767.
The bicyclic coumarin derivative-1, 3 propano-2-bromo-1,2-dihydro-3H-pyrano [2, 3-c] [1]benzo-pyran-5-one (8) was synthesised by a sequence of reaction viz. acetylation of 4-[2′-cyclohexenyl] -3-hydroxy [1] benzopyran-2-one (4), addition of bromine to cyclohexenyl double bond and treating the resulting acetyldi-bromo derivative (7) with 4% alcoholic KOH. Benzofuro [2, 3-c] [1] -benzopyran-6-one (10) was synthesised from 4 via oxymercuration with mercuric acetate in methanol followed by dehydrogenative damercuration with Pd-C in refluxing diphenyl ether. 相似文献
768.
Prakash T. Parvatkar P.S. Parameswaran Debasish Bandyopadhyay Sanghamitra Mukherjee Bimal K. Banik 《Tetrahedron letters》2017,58(30):2948-2951
Microwave-induced Bi(NO3)3-catalyzed one-pot synthesis of a series of linear indoloquinolines is accomplished under mild reaction conditions. While majority of these examples were carried out under solvent-free conditions, in a few cases, minimal quantity of THF is used as solvent. The methodology involves several unique reaction pathways, providing different linear indolo[2,3-b]quinolines in good yields from readily available starting materials and using environmentally benign Bi(NO3)3·5H2O as catalyst. 相似文献
769.
Sen Gupta Kalyan Kali Maiti Surajit Samanta Tapashi Nandi Sanghamitra Banerjee Amalendu 《Transition Metal Chemistry》1982,7(5):274-279
Summary The kinetics of oxidation of ethylene glycol, 2,3-butanediol and pinacol have been studied spectrophotometrically under different experimental conditions. The reactions seem to occur through the formation of an intermediate complex between each diol and iridium(IV). The complexes decompose through intermediate free radicals to form formaldehyde, acetaldehyde and acetone, respectively. Thermodynamic parameters have been calculated. 相似文献
770.
K. C. Majumdar G. H. Jana S. K. Ghosh S. Saha 《Monatshefte für Chemie / Chemical Monthly》1997,128(6-7):641-650
Summary At elevated temperatures, the 3-(meta-substituted aryloxymethyl) coumarins3a–e and3g–k undergo sigmatropic rearrangements to give the hydroxylated 3-benzylcoumarins4a–e and4g–k. Upon methylation and subsequent oxidation with N-bromo succinimide, the 3-(chlorosubstituted benzyl) coumarins4a,4m and4n afford 3-(chlorosubstituted benzoyl) coumarins8a,8m, and8n.
Untersuchungen von sigmatropen Umlagerungen: Thermische Umlagerung von 3-meta-substituierten Aryloxymethylcumarinen
Zusammenfassung Bei erhöhter Temperatur reagieren die 3-meta-substituierten Aryloxymethylcumarine3a–e und3g–k über eine sigmatrope Umlagerung zu den hydroxylierten 3-Benzylcumarinen4a–e und4g–k. Methylierung der 3-chlorsubstituierten Benzoylcumarine4a,4m und4n, gefolgt von Oxidation mit N-Bromsuccinimid, ergibt die 3-chlorsubstituierten Benzoylcumarine8a,8m und8n.相似文献