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131.
María Teresa Caballero Walter D. Furlan Amparo Pons Genaro Saavedra Manuel Martínez-Corral 《Optics Communications》2006,260(2):767-771
The influence of optical aberrations on the retinoscopic reflex is theoretically analyzed from a geometrical point of view. The relationship between the wave aberrations to the ray aberrations is applied to explain the appearance of the retinoscopic patterns for different types of ocular aberrations. Several schematic models of the human eye are tested numerically, showing that a careful retinoscopic examination can detect the usual eye aberrations. 相似文献
132.
Pilar Puebla Zoila Honores Manuel Medarde Esther Caballero Arturo San Feliciano Lourdes Morn 《Journal of heterocyclic chemistry》1999,36(4):1097-1099
Enaminones are widely employed in the synthesis of heterocycles, however heterocyclic enaminones and their use in the synthesis of more complex systems have been less studied. The reaction between 4-chloroacetylacetate and aliphatic or aromatic 1,2-aminoalcohols, 1,2-aminothiols or 1,2-diamines, yields in one pot a six-membered 1,4-heterocyclic system containing the enaminone moiety. 相似文献
133.
Esther Caballero Dulce Alonso Concepción Alvarez Francisca Sanz Fernando Tomé 《Tetrahedron letters》2004,45(8):1631-1634
New 1-phthalimido-4-(3-indolyl)-2-trialkylsiloxy-1,3-butadienes were easily prepared from 1,3-dichloropropanone and their configurations were established from NMR data. Their Diels-Alder reactivity with different maleimides and quinones was studied, high yields of the exo cycloadducts being obtained, as confirmed by X-ray diffraction studies. 相似文献
134.
135.
Ruthenoarenes versus Phenol Derivatives as Axial Linkers for Subporphyrazine Dimers and Trimers 下载免费PDF全文
Dr. Esmeralda Caballero Dr. Carlos Romero‐Nieto Volker Strauß Dr. M. Salomé Rodríguez‐Morgade Prof. Dirk M. Guldi Prof. Jonathan L. Sessler Prof. Tomás Torres 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6518-6525
The subporphyrazine (SubPz) dimer diboron(III) [μ‐1′,4′‐benzenediolato][bis‐(1,2,6,7,11,12‐hexapropylsubporphyrazinato)] ( 2 ) and trimer triboron(III)[μ‐1′,3′,5′‐benzenetriolato][tris‐(1,2,6,7,11,12‐hexapropylsubporphyrazinato)] ( 4 ), consisting of SubPz units assembled through their axial positions by hydroquinone‐ and phloroglucinol‐linkers, respectively, have been prepared. Selective ruthenium‐π‐coordination to the linking aromatic rings afforded SubPz arrays 8 and 9 , respectively. These latter systems displayed different degrees of electronic communication between the macrocycles relative to 2 and 4 as inferred from analyses of the ground‐ and excited‐state features. For instance, as revealed by time‐resolved pump probe transient absorption spectroscopy, the excited singlet states of dimer 2 and trimer 4 undergo rather rapid deactivation. In contrast, the presence of a ruthenoarene linker, as in 8 and 9 , serves to increase the SubPz singlet excited state lifetimes; these now reach values similar to those seen in the case of monomeric SubPz compounds that either do or do not contain ruthenoarene subunits (i.e., 7 and 6 , respectively). These findings are ascribed to the redox active nature of the hydroquinone and phloroglucinol linkers in 2 and 4 and a change in the electronics that results from organometallic functionalization. 相似文献
136.
Inés Nicolás‐Vázquez Guadalupe Pérez‐Caballero Annia Galano Jiménez Georgina Guzmán Rangel René Miranda Ruvalcaba 《International journal of quantum chemistry》2013,113(8):1107-1115
A novel azocompound with two nonequivalents azo groups, 2‐(4‐phenylazoaniline)‐4‐phenylphenol, was synthesized and characterized by spectroscopic and computational analysis. An intramolecular hydrogen bonding (HB), ? O1? H1 ··· N1? , involving the ? N1?N2? group and the proton in a neighbor hydroxyl moiety, was identified. It was found responsible for a characteristic π‐conjugated H1? O1? C18?C13? N2?N1? six‐membered cyclic fragment. It is worth noting that this azo group is involved in an azo‐hydrazo equilibrium, being the azo form the most stable one. This resonance‐assisted HB was characterized using the OH‐related infrared bands and the corresponding signals in 1H NMR. In addition, conformational studies and geometrical and electronic parameter calculations were performed using the density functional theory, at B3LYP/6‐311++G** level. Bond and ring critical points were identified using the atoms in molecules theory, which allowed confirming the intramolecular HB. The second azo‐group cannot be involved in HB, but it also presents two stereoisomerics forms corresponding to cis (Z) and trans (E) configurations, with the later being the one with the lowest energy. © 2013 Wiley Periodicals, Inc. 相似文献
137.
Javier Gonzalez Marc Caballero Antoni Aguilar-Mogas Miquel Torrent-Sucarrat Ramon Crehuet Albert Sol�� Xavier Gim��nez Santiago Olivella Josep M. Bofill Josep M. Anglada 《Theoretical chemistry accounts》2011,128(4-6):579-592
The reaction between the HO radical and (H2O)n (n?=?1, 3) clusters has been investigated employing high-level quantum mechanical calculations using DFT-BH&HLYP, QCISD, and CCSD(T) theoretical approaches in connection with the 6-311?+?G(2df,2p), aug-cc-pVTZ, and aug-cc-pVQZ basis sets. The rate constants have also been calculated and the tunneling effects have been studied by means of time?Cdependent wavepacket calculations, performed using the Quantum?CReaction Path Hamiltonian method. According to the findings of previously reported theoretical works, the reaction between HO and H2O begins with the formation of a pre-reactive complex that is formed before the transition state, the formation of a post-reactive complex, and the release of the products. The reaction between HO and (H2O)2 also begins with the formation of a pre-reactive complex, which dissociates into H2O??HO?+?H2O. The reaction between HO and (H2O)3 is much more complex. The hydroxyl radical adds to the water trimer, and then it occurs a geometrical rearrangement in the pre-reactive hydrogen-bonded complex region, before the transition state. The reaction between hydroxyl radical and water trimer is computed to be much faster than the reaction between hydroxyl radical and a single water molecule, and, in both cases, the tunneling effects are very important mainly at low temperatures. A prediction of the atmospheric concentration of the hydrogen-bonded complexes studied in this work is also reported. 相似文献
138.
Dr. Eva M. Barea Dr. Rubén Caballero Leticia López‐Arroyo Dr. Antonio Guerrero Dr. Pilar de la Cruz Prof. Fernando Langa Prof. Juan Bisquert 《Chemphyschem》2011,12(5):961-965
Porphyrins are promising sensitizers for dye solar cells (DSCs) but narrow absorption bands at 400–450 and 500–650 nm limit their light‐harvesting properties. Increasing elongation of the π‐conjugation and loss of symmetry causes broadening and a red‐shift of the absorption bands, which considerably improves the performance of the DSC. Herein we use an oligothienylenevinylene to bridge a Zn‐porphyrin system and the anchoring group of the sensitizer. We separately study the performance of the two basic units: oligothienylenevinylene and Zn‐porphyrin. The combined system provides a three‐fold enhancement of the photocurrent with respect to parent dyes. This is caused by an additional strong absorption in the region 400–650 nm that leads to flat IPCE of 60 %. Theoretical calculations support that the addition of the oligothienylenevinylene unit as a linking bridge creates a charge transfer band that transforms a Zn‐porphyrin dye into a push–pull type system with highly efficient charge injection properties. 相似文献
139.
Copolymer composition and comonomer distribution are important magnitudes in polymer material that have a big effect on different kind of properties and consequently there are several ways to study.In this work several ethylene/propylene copolymers synthesized with two different metallocene catalysts and a Ziegler–Natta catalyst and covering a wide composition range were studied. Characterization was carried out by nuclear magnetic resonance (13C NMR) and by gel permeation chromatography with 4 detectors (GPC-4D): refractive index, viscosity, multi-angle light scattering and infrared detectors.Different behaviour in the comonomer distribution along the molecular weight was obtained for metallocene and for ZN copolymers as expected due to the differences between these catalytic systems. Nevertheless, Ziegler–Natta copolymers present more homogeneous comonomer distribution due to the synthesis method. Study of conformation of chains in solution was improved by defining the scaling law of Rg against the number of repeat units because it avoids the effect of the repetitive unit size. Both metallocene copolymer sets show similar dependence of q value with the copolymer composition, however Ziegler–Natta copolymers show different behaviour with q values independent on copolymer composition. This different behaviour has been related with the effects of the heterogeneity of the ethylene distribution and of the molecular weight of the samples. 相似文献
140.
J. Caballero K. Sadarangani 《Applied mathematics and computation》2011,218(5):1617-1622
In this paper we prove a fuzzy integral inequality for convex functions. Our results improve recent results that appear in literature. Some examples are given to illustrate our theorems. 相似文献