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531.
Andrej?Voronov Sergej?Minko Alexander?Shulga Emile?PefferkornEmail author 《Colloid and polymer science》2004,282(9):1000-1007
The poly(2-vinylpyridine) layer was established at the Pyrex glass/water interface with periodic phases of adsorption/desorption runs observed over several days. This was evidenced by determining the concentration of radio-labelled molecules in the solution equilibrating the glass beads as a function of time (the effluent) while the same radio-labelled polymer was slowly supplied by injecting the polymer solution into the reactor containing the adsorbent at a controlled extremely slow rate. Although the adsorption (or the desorption) steps seemed to present some periodic character, they were better correlated with the successive bulk concentration thresholds that were established with time when the initial surface was free of polymer at time zero. Even when the adsorbent was coated at different degrees, desorption steps were correlated to the overstepping of decreasing concentration thresholds. Adsorption and desorption runs were attributed to the existence of different typical interfacial conformations of the adsorbed macromolecules that only can be stabilised in the adsorbed state when the layer was equilibrated with the polymer solution of a certain concentration. Macromolecule were definitely adsorbed when the reconformation process led to a flat conformation (trains). Macromolecules adsorbed with a conformation close to their solution conformation may be desorbed as a result of the reconformation process affecting previously adsorbed neighbour molecules (in the case of partially coated surfaces at time zero of injection). Macromolecules with loops and tails were retained on the surface when the polymer concentration in the bulk was progressively increased (for uncoated surfaces at time zero of injection). All these effect were attributed to the combined influence of topological effects on adsorption and reconformation of adsorbed macromolecules that characterise the non-equilibrium adsorption processes. 相似文献
532.
N. G. Dem’yantseva S. M. Kuz’min M. A. Solunin S. A. Solunin A. M. Solunin 《Technical Physics》2012,57(11):1465-1474
The equations of motion for a charged particle in an electric field featuring a stationary and an oscillating component are considered for the case where the force of friction is linear in the particle velocity. The averaging of these equations over the period of field oscillations is legitimate under some specific conditions. The most general expression for an additional stationary force acting on the particle under these conditions is derived, and the limiting values of this force are found. Applications of the results obtained in the present study are considered. Such applications include the use of pulsed currents in the electrochemical dimensional treatment of materials. 相似文献
533.
Marjan Druovec Bojan A
ko Andrej Godina Tatjana Welzer 《Optics and Lasers in Engineering》2009,47(11):1131-1138
The paper presents research into line centre detection using a video positioning system, as part of a measuring system for line scale calibration. In the described approach, the video positioning system processes an image taken by a CCD camera to estimate the position of the observed line's centre. An important part of this research is also an analysis of line scale contamination's influence (scratches, dirt, usage, etc.) on line position determination. The outcome of the research is mathematical models that can be used as a base for developing a positioning algorithm. This algorithm is simple and adaptable to different types of line scales. It also includes a module for increasing the basic scale factor of the positioning as defined by the number of pixels in the CCD sensor, and a module for reducing the influence of contamination on positioning. 相似文献
534.
Andrej A. Konʼkov 《Journal of Mathematical Analysis and Applications》2012,388(1):102-124
We obtain estimates for non-negative solutions of quasilinear elliptic inequalities with the lowest terms. 相似文献
535.
Samuel Andrejčák Dr. Péter Kisszékelyi Dr. Michal Májek Prof. Dr. Radovan Šebesta 《European journal of organic chemistry》2023,26(5):e202201399
Arylboronates are helpful building blocks in organic synthesis. Here, we present an efficient mechanochemical synthesis of arylboronates from arene diazonium salts. Importantly, this transformation was significantly enhanced by sodium chloride, which probably promotes the decomposition of diazonium salts via anion exchange. Chloride anions also participate in the formation of strongly reducing Cl−B anion radical intermediate that promotes radical chain reaction. The reaction proceeds more efficiently with a small amount of polar solvent as a liquid-assisted grinding additive. Quantum chemical calculations support the mechanistic proposal. 相似文献
536.
Fidanchevski Emilija Angjusheva Biljana Jovanov Vojo Murtanovski Pece Vladiceska Ljubica Aluloska Nikolina Stamatovska Nikolic Jelena Krneta Ipavec Andrej Šter Katarina Mrak Maruša Dolenec Sabina 《Journal of Radioanalytical and Nuclear Chemistry》2021,330(3):685-694
Journal of Radioanalytical and Nuclear Chemistry - Huge quantities of fly ash and bottom ash are generated from thermal power plants and it presents great concern for country, mainly due... 相似文献
537.
538.
Werner Uhl Christian Appelt Jana Backs Hans Klöcker Andrej Vinogradov Hauke Westenberg 《无机化学与普通化学杂志》2014,640(1):106-109
The synthesis of dineopentylaluminum hydride, H‐Al(CH2CMe3)2, is known in the literature since 1988. We determined the crystal structure of this important starting material and found different ring sizes with dimeric versus trimeric formula units. The molecular shape depends on the polarity of the solvent used for recrystallization (n‐pentane or 1,2‐difluorobenzene). The synthesis of diphenylaluminum hydride, which is also long known in the literature, was optimized. It has a trimeric structure in the solid state with an Al3H3 heterocycle. 相似文献
539.
540.
Andrej Staško Viktor Milata Zuzana Barbieriková Vlasta Brezová 《Magnetic resonance in chemistry : MRC》2014,52(1-2):22-26
4‐Oxoquinoline derivatives (quinolones) represent heterocyclic compounds with a variety of biological activities, along with interesting chemical reactivity. The quinolone derivatives possessing secondary amino hydrogen at the nitrogen of the enaminone system are oxidized with 3‐chloroperbenzoic acid to nitroxide radicals in the primary step while maintaining their 4‐pyridone ring. Otherwise, N‐methyl substituted quinolones also form nitroxide radicals coupled with the opening of the 4‐pyridone ring in a gradual oxidation of the methyl group via the nitrone–nitroxide spin‐adduct cycle. This was confirmed in an analogous oxidation using N,N‐dimethylaniline as a model compound. N‐Ethyl quinolones in contrast to its N‐methyl analog form only one nitroxide radical without a further degradation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献