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361.
Silvio Aime Mauro Fasano Enzo Terreno Corrado Sarzanini Edoardo Mentasti 《Magnetic resonance imaging》1991,9(6):963-968
The interaction of a soluble Melanin Free Acid (MFA) from Sepia melanin with Mn2+ ions is investigated by measuring the proton water relaxation rates. The similarity between MFA and the parent melanin is assessed by means of their high resolution 13C cross polarization magic angle spinning NMR spectra. The observed marked increase in longitudinal proton relaxation rates and the characteristic 1/T1 NMRD profile are associated to the formation of a macromolecular metal complex. The presence of similar paramagnetic species is expected to cause the high contrast shown by melanotic tissues in MRI. 相似文献
362.
363.
Umberto Bianchi Carla Cuniberti Enrico Pedemonte Corrado Rossi 《Journal of Polymer Science.Polymer Physics》1969,7(5):845-853
The conformational energy contribution (ΔUconf) to the heat of solution in polymer-solvent systems is presented and discussed in connection with chain conformational properties. In particular, ΔUconf has been discussed in terms of various possible mechanisms of coil deformation. 相似文献
364.
Deuterium N.M.R. spectroscopy has been used to investigate the orientational ordering of perdeuteriated naphthalene and two perdeuteriated fluorescent probes (pyrene and perylene) dissolved in a discotic nematic micellar phase of potassium laurate/potassium chloride/decanol/water. The results show that the ordering tensors of these probes are not cylindrically symmetric. 相似文献
365.
Daniele Belletti Mauro Carcelli Corrado Pelizzi Giancarlo Pelizzi 《Journal of chemical crystallography》1992,22(2):185-191
A seven-coordinate cobalt(II) complex has been synthesized with a new hydrazonic ligand, H4dapis, and its crystal structure determined by X-ray diffraction methods and refined toR 0.0564 for 2763 independent reflections. The structure consists of [Co(H4dapis)(OH2)2] cations, Cl anions, and lattice H2O molecules interlinked by hydrogen bonds. The cobalt atom has a distorted pentagonal bipyramidal environment with two axial H2O molecules and the H4dapis ligand forming the basal plane. 相似文献
366.
367.
Jean Ngoune Corrado Di Nicolas Justin Nenwa Claudio Pettinari Eleuterio Alvarez Siméon Ponou 《Transition Metal Chemistry》2013,38(1):21-29
A complex of composition {[{Cu(NDC)(OH2)(tn)(μ-OH2)}2]·2H2O}∞ (1) and a mononuclear complex salt [Cu(OH2)2(tn)2](NDC)·3H2O (2), where NDC = 2,6-naphthalenedicarboxylate dianion and tn = 1,3-diaminopropane, were simultaneously crystallized from an aqueous solution of the copper(II) naphthalenedicarboxylate—1,3-diaminopropane—methanol system. The crystal and molecular structures of both complexes were determined by single-crystal X-ray diffraction. Compound (1) consists of a supramolecular coordination complex in which the monomeric unit is assembled from a homodinuclear Cu(II) bridged by two water ligands. The Cu(II) centers exhibit distorted octahedral coordination; the equatorial plane is provided by one chelating tn ligand, one NDC2? ligand, one μ-H2O while the axial positions are occupied by H2O and μ-H2O. Strong intra- and/or intermolecular hydrogen bonds, also involving the crystallization water molecules, together with π–π stacking interactions, are involved in building up the supramolecule. The solid structure of compound (2) includes three water molecules of crystallization, the counter ion NDC2?, and a Cu(II) cationic complex in which the metal is six-coordinated in an axially elongated octahedron defined by two chelating tn ligands in the equatorial plane and two water ligands in the axial positions. Thermal analyses of (1) show two significant weight losses corresponding to water molecules (lattice and coordinated), followed by the decomposition of the network. 相似文献
368.
Francesco Acquasanta Corrado BertiMartino Colonna Maurizio FioriniSreepadaraj Karanam 《Polymer Degradation and Stability》2011,96(12):2098-2103
Engineering thermoplastic polymers such as polyamides, polycarbonates, semi-crystalline aromatic polyesters and their blends are widely used as insulating materials in electrical and electronic appliances. Flame retardants are often employed in the formulation of these materials, since good performance in terms of ignition and tracking resistance, evaluated by Glow Wire Tests (GWIT) and Comparative Tracking Index (CTI) are required in these applications. In this paper, a comparative evaluation of GWIT and CTI performances has been simultaneously performed for a wide set of glass fibre filled materials chosen among engineering thermoplastics and their blends. Some flame retarded formulations have been also tested, in order to screen the effects of various additives. Useful indications have been obtained on the effect of each polymer and additives on GWIT and CTI properties. In addition, interesting synergies have been observed, especially by blending polyesters and polyamides. Thermogravimetric measurements of char yields have been successfully related with CTI behaviour. The presence of additives changes the structure of the carbonaceous residue, hence the conductivity of the tracks. Neat polycarbonate passed the GWIT test but not CTI, while poly(butylene terephthalate) showed the best balance of GWIT and CTI performance among the pure resins tested. Blending polycarbonate with polyester did not improve significantly GWIT performance, but had a negative effect on tracking resistance. Polyesters/polyamide blends were dominated by polyester in GWIT, but they showed synergistic effects in CTI. 相似文献
369.
The ortho-metallated complex [Pd(μ-Cl){κ2(C,C)-[C6H4(PPh2CHC(O)C6H4-Ph-4)}]2 (2a) was prepared by refluxing of Pd(OAc)2 and {(Ph)3PCHCOC6H4-Ph-4} (PhBPPY) of in CH2Cl2 followed by addition of an excess of KCl in MeOH Complex (2a) reacts with triphenylphosphine to give the mononuclear derivative [Pd(Cl)(PhC6H4COCHPPh2C6H4)(PPh3)] (3a) whose crystal structure has been determined by single crystal X-ray diffraction. The Suzuki reactions of aryl bromides and chlorides of varying electron density using complex (3a) as an efficient catalyst were performed, giving the cross-coupling products in good to excellent yields. 相似文献
370.
Cooper JK Franco AM Gul S Corrado C Zhang JZ 《Langmuir : the ACS journal of surfaces and colloids》2011,27(13):8486-8493
Surface ligands of semiconductor quantum dots (QDs) critically influence their properties and functionalities. It is of strong interest to understand the structural characteristics of surface ligands and how they interact with the QDs. Three quantum dot (QD) systems (CdSe, ZnSe, and ZnS) with primary aliphatic amine capping ligands were characterized primarily by FT-IR spectroscopy as well as NMR, UV-vis, and fluorescence spectroscopy, and by transmission electron microscopy (TEM). Representative primary amines ranging from 8 to 16 carbons were examined in the vapor phase, KBr pellet, and neat and were compared to the QD samples. The strongest hydrogen-bonding effects of the adsorbed ligands were observed in CdSe QDs with the weakest observed in ZnS QDs. There was an observed splitting of the N-H scissoring mode from 1610 cm(-1) in the neat sample to 1544 and 1635 cm(-1) when bound to CdSe QDs, which had the largest splitting of this type. The splitting is attributed to amine ligands bound to either Cd or Se surface sites, respectively. The effect of exposure of the QDs dispersed in nonpolar medium to methanol as a crashing agent was also examined. In the CdSe system, the Cd-bound scissoring mode disappeared, possibly due to methanol replacing surface cadmium sites. The opposite was observed for ZnSe QDs, in which the Se-bound scissoring mode disappeared. It was concluded that surface coverage and ligand bonding partners could be characterized by FT-IR and that selective removal of surface ligands could be achieved through introduction of competitive binding interactions at the surface. 相似文献