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931.
Zannini P 《Annali di chimica》2002,92(11-12):1077-1087
Three clayey raw materials for production of traditional ceramics, all with medium to high fluorine content, have been investigated for determining their attitude to fluoride emission during firing, at varying parameters of the firing cycle, maximum firing temperature included, and in the presence or in the absence of calcium carbonate either added to the sample or naturally present in it. Different analytical methods for the determination of fluoride have been tested, together with different sample preparation procedures aimed to obtain minimum loss of fluoride in the pre-treatment step. 相似文献
932.
Di Bussolo V Caselli M Romano MR Pineschi M Crotti P 《The Journal of organic chemistry》2004,69(25):8702-8708
6-O-Trityl- (1a) and 6-(O-benzyl)-substituted epoxide (1b) derived from D-glucal were examined in their addition reactions with O-, C-, N-, and S-nucleophiles. A 1,4-regio- and beta-stereoselective or an anti 1,2-addition pathway is commonly observed depending on the ability of the nucleophile to coordinate with the oxirane oxygen. When TMSN(3) or LiN(3) are used as azide-based nucleophiles, a 1,2-syn-addition pathway is also observed. 相似文献
933.
Mario Nardelli Corrado Pelizzi Giovanni Predieri Gian Paolo Chiusoli 《Journal of organometallic chemistry》1981,204(1):75-78
Bis(dinitrogen)bis[1,2-bis(diphenylphosphino)ethane]molybdenum reacts with chlorobenzene to form molybdenum chloro complexes and phenylated organic products. Benzene, biphenyl, o-, m-, p-chlorobiphenyl, a dihydro derivative of o-chlorobiphenyl, triphenylphosphine and diphenylvinylphosphine were formed. The isomer distribution of the chlorobiphenyls is close to that obtained by decomposition of 0.02 M benzoyl peroxide in chlorobenzene under dinitrogen. The cleavage of the PhCl bond induced by the molybdenum-dinitrogen complex appears to give rise to the same homolytic reaction pattern. Phenylation of anisole and of triethyl phosphite has also been achieved with the same reagent. 相似文献
934.
Mario Suwalsky Beryl NorrisTamas Kiss Paolo Zatta 《Coordination chemistry reviews》2002,228(2):285-295
Aluminum, a very abundant metal, might play an important role in several pathologies which could be related to its interactions with cell membranes. Although the effects of Al(III) on biological membranes have been extensively described, direct information concerning the molecular basis of its biological activity is rather scarce. One reason for this lack of molecular information is the ill-defined chemical speciation of the metal compounds utilized in toxicological experimental protocols. Another is the complex molecular structure of cell membranes. For this reason, molecular models consisting in phospholipid bilayers are commonly used. In this review the interaction of four Al(III) compounds with phospholipid bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) and their effects on ion channels present in isolated toad skins are discussed. The aluminum compounds are Al(acac)3, AlCl3, AlF3 and the Al-citrate complex [K5Al(C6H4O7)2]. It is concluded that they interact with and produce different structural and functional effects on the model and biological membranes. X-ray diffraction revealed that AlCl3 (1 mM) induced the most damaging effects to both DMPC and DMPE bilayers whereas the Al-citrate complex caused only slight perturbation, the effects of Al(acac)3 and AlF3 being intermediate. The inhibitory effects on the isolated skin, in descending order, were (100 μM): AlCl3, possibly by indirect and direct inactivation of Na+ channels and/or perturbation of an ATPase; AlF3, by direct inactivation of the Na+ channel and mild ATPase inhibition; Al-citrate, by decrease of Na+ permeability, and lastly, Al(acac)3, which decreased Na+ transport only at far higher concentration (250 μM). 相似文献
935.
936.
937.
George Papamokos Jens Dreyer Luciano Navarini Paolo Carloni 《International journal of quantum chemistry》2014,114(9):553-559
Neurotoxic and carcinogenic acrylamide (ACR) is present in many food products. This finding spurred numerous studies for ACR scavengers. Niacin is putatively one of them because it reacts via Michael addition with ACR to form 1‐propanamide‐3‐carboxy pyridinium. Here, we study the mechanism and energetics of this reaction in aqueous solution by density functional theory. The CAM‐B3LYP and M06‐2X functionals with the 6‐31+G(d,p) basis set and implicit solvent were used. Single point calculations at the MP2 level with the same basis set were performed on optimized structures obtained at the M06‐2X level. Solvent effects comprehended both polarizable continuum model and solvation model density solvation models. The calculated NMR chemical shifts of 1‐propanamide‐3‐carboxy pyridinium are in agreement with experimental results. The theoretical study favors thermodynamically the formation of the adduct while the calculated activation energies turn out not to be too dissimilar from the ones measured for the alkylation reaction between ACR and 4(p‐nitrobenzyl)pyridine. © 2014 Wiley Periodicals, Inc. 相似文献
938.
939.
Paolo Ceccherelli † Massimo Curini Maria Carla Marcotullio Francesco Epifano Ornelio Rosati 《合成通讯》2013,43(16):3057-3064
A mild and convenient oxidative Nef reaction using Oxone® (potassium hydrogen persulfate) is described. Following our procedure primary and secondary nitroalkanes generate carboxylic acids and ketones, respectively, both in good yields. 相似文献
940.