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991.
Unprecedented Spectroscopic and Computational Evidence for Allenyl and Propargyl Titanocene(IV) Complexes: Electrophilic Quenching of Their Metallotropic Equilibrium 下载免费PDF全文
Ana Belén Ruiz‐Muelle Dr. Pascual Oña‐Burgos Dr. Manuel A. Ortuño Prof. Dr. J. Enrique Oltra Prof. Dr. Ignacio Rodríguez‐García Prof. Dr. Ignacio Fernández 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2427-2439
The synthesis and structural characterization of allenyl titanocene(IV) [TiClCp2(CH=C=CH2)] 3 and propargyl titanocene(IV) [TiClCp2(CH2?C≡C?(CH2)4CH3)] 9 have been described for the first time. Advanced NMR methods including diffusion NMR methods (diffusion pulsed field gradient stimulated spin echo (PFG‐STE) and DOSY) have been applied and established that these organometallics are monomers in THF solution with hydrodynamic radii (from the Stokes–Einstein equation) of 3.5 and 4.1 Å for 3 and 9 , respectively. Full 1H, 13C, Δ1H, and Δ13C NMR data are given, and through the analysis of the Ramsey equation, the first electronic insights into these derivatives are provided. In solution, they are involved in their respective metallotropic allenyl–propargyl equilibria that, after quenching experiments with aromatic and aliphatic aldehydes, ketones, and protonating agents, always give the propargyl products P (when carbonyls are employed), or allenyl products A (when a proton source is added) as the major isomers. In all the cases assayed, the ratio of products suggests that the metallotropic equilibrium should be faster than the reactions of 3 and 9 with electrophiles. Indeed, DFT calculations predict lower Gibbs energy barriers for the metallotropic equilibrium, thus confirming dynamic kinetic resolution. 相似文献
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Prof. Enrique Rodríguez-Castellón Dr. Daniel Delgado Dr. Ana Dejoz Dr. Isabel Vázquez Dr. Said Agouram Dr. Juan A. Cecilia Dr. Benjamín Solsona Prof. José M. López Nieto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(42):9371-9381
A Nb-containing siliceous porous clay heterostructure (PCH) with Nb contents from 0 to 30 wt %) was prepared from a bentonite and used as support in the preparation of supported NiO catalysts with NiO loading from 15 to 80 wt %. Supports and NiO-containing catalysts were characterised by several physicochemical techniques and tested in the oxidative dehydrogenation (ODH) of ethane. The characterisation studies on Nb-containing supports showed the presence of well-anchored Nb5+ species without the formation of Nb2O5 crystals. High dispersion of nickel oxide with low crystallinity was observed for the Nb-containing PCH supports. In addition, when NiO is supported on these Nb-containing porous clays, it is more effective in the ODH of ethane (ethylene selectivity of ca. 90 %) than NiO supported on the corresponding Nb-free siliceous PCH or on Nb2O5 (ethylene selectivities of ca. 30 and 60 %, respectively). Factors such as the NiO–Nb5+ interaction, the NiO particle size and the properties of surface Nin+ species were shown to determine the catalytic performance. 相似文献
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F. Rodríguez I. Hernández R.E. Gutiérrez S. García-Revilla M. Moreno R. Alcalá 《高压研究》2013,33(1):115-119
The surprising disappearance of the Mn 2+ photoluminescence (PL) on passing from CaF 2 to SrF 2 through the Ca 1 m x Sr x F 2 :Mn 2+ series is investigated through pressure spectroscopy, and as a function of the temperature. The PL quenching which is observed along the series is explained on the basis of multiphonon relaxation mechanisms, which are described by a thermally activated process. In non-luminescent crystals, PL can be recovered by applying pressure. The results are accounted for through an universal equation relating the PL lifetime as a function of P (or V ) and T , using an activation energy and a transition rate that are strongly dependent on the lattice parameter (crystal volume). 相似文献
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Javier Illescas Yessica S. Ramirez‐Fuentes Ernesto Rivera Omar G. Morales‐Saavedra Antonio A. Rodríguez‐Rosales Valeria Alzari Daniele Nuvoli Sergio Scognamillo Alberto Mariani 《Journal of polymer science. Part A, Polymer chemistry》2012,50(4):821-830
2‐Phenoxyethyl acrylate (2‐PEA) was polymerized alone and in the presence of an azobenzene comonomer derived from Disperse Red‐1, N‐ethyl‐N‐(2‐hydroxyethyl)‐4‐(4‐nitrophenylazo)aniline (MDR‐1), by using the frontal polymerization technique. Two novel ionic liquids, recently synthesized by us, were used as initiators: tetrabutylphosphonium persulfate (TBPPS) and trihexyltetradecylphosphonium persulfate (TETDPPS). Even if their concentrations were smaller than those found when benzoyl peroxide and terbutylperoxy neodecanoate were used, these compounds gave rise to stable propagating polymerization fronts characterized by relatively low maximum temperatures and good velocities. Moreover, at variance to these latter, TBPPS and TETDPPS prevent bubble formation, thus allowing the use of the obtained materials in optical applications. The obtained polymers were characterized by infrared spectroscopy (FTIR), their thermal properties were determined by differential scanning calorimetry, and their optical properties were studied by absorption spectroscopy in the UV–vis region. Finally, the nonlinear optical (NLO) properties of the 2‐PEA/MDR‐1 copolymers obtained with TBPPS and TETDPPS were performed according to the Z‐Scan technique with prepared film samples. It has been proven that samples with higher MDR‐1 content (0.05 mol %) exhibited outstanding cubic NLO activity with negative NLO refractive coefficients around n2 = ?1.7 × 10?3 esu. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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Rodríguez de Rivera Pedro Jesús Rodríguez de Rivera Miriam Socorro Fabiola Callicó Gustavo Marrero Calbet Jose A. L. Rodríguez de Rivera Manuel 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7385-7398
Journal of Thermal Analysis and Calorimetry - A non-invasive sensor equipped with a programmable thermostat has been developed to assess in vivo the heat flow transmitted by conduction from human... 相似文献
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