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171.
Fernando A. Otero Gloria L. Frontini Guillermo E. Eliçabe 《Journal of Polymer Science.Polymer Physics》2010,48(9):958-963
This work deals with the application of the static light scattering (SLS) model of Vrij (VM) for the characterization of a spherical polydisperse concentrated polymer particle system. This model is the exact solution for the SLS of such mixture of particles in the Percus–Yevick approximation. The analyzed polymer particle samples are obtained by solution polymerization of isobornyl methacrylate in polyisobutylene. At the end of the polymerization, as a result of phase separation, a particle system of micrometer sized particles with a moderate distribution of sizes and a volume fraction between 5 and 10% is formed. The SLS data were also analyzed using the local monodisperse approximation (LMA), a well‐known approximation to the model of Vrij. As expected, the estimations with the VM gave better results than those performed with the LMA model for the parameters related to the shape of the particle size distribution as compared with independent determinations of these quantities obtained from scanning electron microscopy micrographs. However, the main motivation to use the more rigorous model seems to be the fact that the volume fraction of particles can be extracted from the data even when relative SLS measurements are used. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 958–963, 2010 相似文献
172.
Dr. Ana Conde Dr. Rosa Fandos Dr. Carolina Hernández Prof. Dr. Antonio Otero Dr. Ana Rodríguez Dr. María José Ruiz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(8):2319-2326
Tantalum complexes [TaCp*Me{κ4‐C,N,O,O‐(OCH2)(OCHC(CH2NMe2)?CH)py}] ( 4 ) and [TaCp*Me{κ4‐C,N,O,O‐(OCH2)(OCHC(CH2NH2)?CH)py}] ( 5 ), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ3‐N,O,O‐(OCH2)(OCH)py}] (Cp*=η5‐C5Me5) with HC?CCH2NMe2 and HC?CCH2NH2, respectively. The reactions of [TaCp*Me{κ4‐C,N,O,O‐(OCH2)(OCHC(Ph)?CH)py}] ( 2 ) and [TaCp*Me{κ4‐C,N,O,O‐(OCH2)(OCHC(SiMe3)?CH)py}] ( 3 ) with triflic acid (1:2 molar ratio) rendered the corresponding bis‐triflate derivatives [TaCp*(OTf)2{κ3‐N,O,O‐(OCH2)(OCHC(Ph)?CH2)py}] ( 6 ) and [TaCp*(OTf)2{κ3‐N,O,O‐(OCH2)(OCHC(SiMe3)?CH2)py}] ( 7 ), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water‐soluble cationic complex [TaCp*(OTf){κ4‐C,N,O,O‐(OCH2)(OCHC(CH2NHMe2)?CH)py}]OTf ( 8 ). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H2O){κ3‐N,O,O‐(OCH2)(OCHC(CH2NHMe2)?CH2)py}](OTf)2 ( 9 ). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ4‐C,N,O,O‐(OCH2)(HOCHC(CH2NHMe2)?CH)py}](OTf)2 ( 10 ), which afforded the corresponding protonolysis derivative [TaCp*(OTf)2{κ3‐N,O,O‐(OCH2)(HOCHC(CH2NHMe2)?CH2)py}](OTf) ( 11 ) in solution. Complex 8 reacted with CNtBu and potassium 2‐isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13 , respectively. The molecular structures of complexes 5 , 7 , and 10 were established by single‐crystal X‐ray diffraction studies. 相似文献
173.
Antonio Otero Prof. Dr. Juan Fernández‐Baeza Agustín Lara‐Sánchez Carlos Alonso‐Moreno Isabel Márquez‐Segovia Luis F. Sánchez‐Barba Ana M. Rodríguez 《Angewandte Chemie (International ed. in English)》2009,48(12):2176-2179
With a sting in its tail : An enantiopure neodymium complex (see scheme) acts as an efficient single‐site initiator for the controlled ring‐opening polymerization of rac‐lactide, forming isotactic polyester. The heteroscorpionate complex was characterized spectroscopically and by X‐ray diffraction.
174.
Conde A Fandos R Hernández C Otero A Rodríguez A Ruiz MJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(8):2319-2326
Tantalum complexes [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NMe(2))=CH)py}] (4) and [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NH(2))=CH)py}] (5), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ(3)-N,O,O-(OCH(2))(OCH)py}] (Cp* = η(5)-C(5)Me(5)) with HC≡CCH(2)NMe(2) and HC≡CCH(2)NH(2), respectively. The reactions of [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(Ph)=CH)py}] (2) and [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(SiMe(3))=CH)py}] (3) with triflic acid (1:2 molar ratio) rendered the corresponding bis-triflate derivatives [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(OCHC(Ph)=CH(2))py}] (6) and [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(OCHC(SiMe(3))=CH(2))py}] (7), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water-soluble cationic complex [TaCp*(OTf){κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NHMe(2))=CH)py}]OTf (8). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H(2)O){κ(3)-N,O,O-(OCH(2))(OCHC(CH(2)NHMe(2))=CH(2))py}](OTf)(2) (9). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ(4)-C,N,O,O-(OCH(2))(HOCHC(CH(2)NHMe(2))=CH)py}](OTf)(2) (10), which afforded the corresponding protonolysis derivative [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(HOCHC(CH(2)NHMe(2))=CH(2))py}](OTf) (11) in solution. Complex 8 reacted with CNtBu and potassium 2-isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13, respectively. The molecular structures of complexes 5, 7, and 10 were established by single-crystal X-ray diffraction studies. 相似文献
175.
Marele AC Mas-Ballesté R Terracciano L Rodríguez-Fernández J Berlanga I Alexandre SS Otero R Gallego JM Zamora F Gómez-Rodríguez JM 《Chemical communications (Cambridge, England)》2012,48(54):6779-6781
The reaction between 1,3,5-tris(4-hydroxyphenyl)benzene and benzene-1,3,5-tricarbonyl trichloride leads to polyester condensation and formation of a novel COF on an Au(111) surface. The characterization performed in situ by means of variable temperature STM and XPS reveals the formation of an array of hexagonal cavities with ca. 2 nm size. 相似文献
176.
The dissociation reaction of nitrosomethane into methyl and nitric oxide and the tautomerization reactions to formaldehyde oxime, nitrone, and methoxy nitrene have been studied with the second-order multiconfigurational perturbation theory (CASPT2) by the computation of numerical energy gradients. The prevailing reactions in both the ground and the excited states are dissociations. The structures of the ground and excited states are compared with the corresponding complete active space SCF (CAS-SCF) geometries. It is found that changes in the individual bond lengths are rather large (0.01-0.02 A), while the character and energetics of the CASPT2 optimizations remain similar to the CAS-SCF values. 相似文献
177.
Centeno SP López-Tocón I Arenas JF Soto J Otero JC 《The journal of physical chemistry. B》2006,110(30):14916-14922
Surface-enhanced Raman spectra (SERS) of pyrimidine recorded on a silver electrode have been analyzed on the basis of a resonant Raman (RR) process involving photoexcited charge transfer (CT) states of the metal-adsorbate surface complex. The main feature of the SERS of benzene and azine derivatives is the enhancement of the totally symmetric ring stretching mode 8a due to Franck-Condon contributions related to the CT transition. Although this behavior is observed in the SERS of pyrimidine, its spectrum is also characterized by the strong enhancement of the nontotally symmetric mode 8b. This peculiar feature can be explained only by the redistribution of the Franck-Condon factors between the 8ab pair of vibrations originated by the descent in symmetry occurring when pyrimidine is bonded to silver nanoclusters. This conclusion is a new evidence of the main role of the RR-CT enhancement mechanism in the SERS of aromatic molecules and shows once again the usefulness of the methodology developed by our group in order to analyze these complex spectra. 相似文献
178.
179.
Hydrogen adsorption (physisorption) on the faujasite-type zeolite Mg-X was studied by means of variable-temperature (80-140 K) FT-IR spectroscopy. Perturbation of the adsorbed H2 molecules by the cationic adsorbing centres of the zeolite renders the H-H stretching mode IR active, at 4065 cm−1. Simultaneous measurement of IR absorbance and hydrogen equilibrium pressure, for a series of spectra recorded at the increasing temperature, allowed standard adsorption enthalpy and entropy to be determined. They resulted to be ΔH0 = −13 kJ mol−1 and ΔS0 = −114 J mol−1 K−1, respectively. Both, spectroscopic and thermodynamic results are discussed in the broader context of corresponding data for hydrogen adsorption on other alkali and alkaline-earth cation exchanged zeolites, showing that, while an approximate correlation exists between ΔH0 and H-H stretching frequency, deviations can be expected for the case of zeolites containing small metal cations. 相似文献
180.
R. Otero F. Calleja V. M. García-Surez J. J. Hinarejos J. de la Figuera J. Ferrer A. L. Vzquez de Parga R. Miranda 《Surface science》2004,550(1-3):65-72
A possible relationship between population of the surface electronic state and chemical reactivity for Cu layers on Ru(0 0 0 1) is revealed by tunneling spectroscopy and microscopy. The surface state shifts down in energy with increasing thickness. Ab initio calculations indicate that the energy shift can be assigned to the decreasing tensile strain of the deposited film. The reactivity of the surface towards oxygen correlates with the population of this state, reaching a maximum at Cu thicknesses where the surface state is empty. These data provides an indication of the effect of strain on the reactivity of metal surfaces. 相似文献