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101.
Gianni Podda Antonio Maccioni Anna Maria Fadda Sergio Daolio Beatrice Pelli Pietro Traldi 《Journal of mass spectrometry : JMS》1984,19(10):496-501
The mass spectrometric behaviour of two newly synthesized β-blocking benzodioxole derivatives, their synthons and synthetic intermediates has been studied in detail with the aid of exact mass measurements, linked scans, collisionally activated decomposition mass analysed ion kinetic energy spectra and deuterium labelling experiments. A retrosynthetic process, leading to the original synthons, is described. 相似文献
102.
Alan Hinchliffe Beatrice Nikolaidi Humberto J Soscún Machado 《Central European Journal of Chemistry》2005,3(2):361-369
We report Ab Initio studies of the electric dipole polarizability of the linear polyacene series benzene through nonacene. A number of Ab Initio studies were done at different levels of theory for benzene, with all remaining Ab Initio calculations being at the B3LYP/6-311G(2d, 1p)//B3LYP/6-311+G(2d, 1p) level of theory. We find that the NN tensor component
shows a constant increment of 20 atomic units per ring. AM1 and QSAR-quality empirical calculations show poor absolute agreement
with the Ab Initio results but given excellent statistical correlation coefficients with the Ab Initio values. This implies that the results of such cheaper calculations can be suitably scaled for predictive purposes. 相似文献
103.
104.
In present theories a particle is commonly associated with a singularity of the field. A more realistic picture would describe the particle by an intense but singularity-free field. We have found a new solution to the aesthetic field equations for which the field associated with the particle has a very large magnitude. The particle appears to be bounded despite the large numbers appearing in the solution. We prove that this present solution is not equivalent to theO(3)-invariant solution discussed in Muraskin (1973b). Since our present solution appears well-behaved, the suggestion is that we do not confine ourselves toO(3)-invariant data in future work. Owing to the large magnitude fields, we were unable to study trajectories of the particle in any detail. There is nothing wrong, in itself, with large numbers. The present solution, which we have now studied, is the first instance in our work on aesthetic field theory in which large numbers appear without the suggestion of unboundedness. 相似文献
105.
Dr. Bolong Zhang Dr. Kieran D. Richards Beatrice E. Jones Abigail R. Collins Rosie Sanders Dr. Sarah R. Needham Dr. Pu Qian Amoghavarsha Mahadevegowda Prof. Caterina Ducati Prof. Stanley W. Botchway Prof. Rachel C. Evans 《Angewandte Chemie (International ed. in English)》2023,62(47):e202308602
Image contrast is often limited by background autofluorescence in steady-state bioimaging microscopy. Upconversion bioimaging can overcome this by shifting the emission lifetime and wavelength beyond the autofluorescence window. Here we demonstrate the first example of triplet-triplet annihilation upconversion (TTA-UC) based lifetime imaging microscopy. A new class of ultra-small nanoparticle (NP) probes based on TTA-UC chromophores encapsulated in an organic–inorganic host has been synthesised. The NPs exhibit bright UC emission (400–500 nm) in aerated aqueous media with a UC lifetime of ≈1 μs, excellent colloidal stability and little cytotoxicity. Proof-of-concept demonstration of TTA-UC lifetime imaging using these NPs shows that the long-lived anti-Stokes emission is easily discriminable from typical autofluorescence. Moreover, fluctuations in the UC lifetime can be used to map local oxygen diffusion across the subcellular structure. Our TTA-UC NPs are highly promising stains for lifetime imaging microscopy, affording excellent image contrast and potential for oxygen mapping that is ripe for further exploitation. 相似文献
106.
Villamena FA Xia S Merle JK Lauricella R Tuccio B Hadad CM Zweier JL 《Journal of the American Chemical Society》2007,129(26):8177-8191
Limitations exist among the commonly used cyclic nitrone spin traps for biological free radical detection using electron paramagnetic resonance (EPR) spectroscopy. The design of new spin traps for biological free radical detection and identification using EPR spectroscopy has been a major challenge due to the lack of systematic and rational approaches to their design. In this work, density functional theory (DFT) calculations and stopped-flow kinetics were employed to predict the reactivity of functionalized spin traps with superoxide radical anion (O2*-). Functional groups provide versatility and can potentially improve spin-trap reactivity, adduct stability, and target specificity. The effect of functional group substitution at the C-5 position of pyrroline N-oxides on spin-trap reactivity toward O2*- was computationally rationalized at the PCM/B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) and PCM/mPW1K/6-31+G(d,p) levels of theory. Calculated free energies and rate constants for the reactivity of O2*- with model nitrones were found to correlate with the experimentally obtained rate constants using stopped-flow and EPR spectroscopic methods. New insights into the nucleophilic nature of O2*- addition to nitrones as well as the role of intramolecular hydrogen bonding of O2*- in facilitating this reaction are discussed. This study shows that using an N-monoalkylsubstituted amide or an ester as attached groups on the nitrone can be ideal in molecular tethering for improved spin-trapping properties and could pave the way for improved in vivo radical detection at the site of superoxide formation. 相似文献
107.
Pino A Alimonti A Botrè F Minoia C Bocca B Conti ME 《Rapid communications in mass spectrometry : RCM》2007,21(12):1900-1906
A simple and efficient digestion method for rapid sample preparation and quantification of 25 chemical elements in lichens by sector field inductively coupled plasma mass spectrometry is described. A microwave (MW)-assisted acid digestion was carried out at atmospheric pressure simultaneously handling up to 80 samples in screw-capped disposable polystyrene tubes. This digestion procedure was compared with the established MW digestion in closed vessels in order to examine its potential applicability in routine analysis for environmental monitoring. Three certified reference materials, i.e. BCR 482 (lichens), BCR 62 (olive leaves) and BCR 100 (beech leaves), as well as a small set of real samples were analyzed. Limits of quantification, accuracy and precision of the method were assessed. The majority of the elements were totally recovered from the lichens and from the other vegetable matrices. Low contamination risk, simplicity, time-saving, and applicability in routine analyses make this method very suitable for use in extensive screening campaigns. 相似文献
108.
Cristiana Cesari Beatrice Berti Francesco Calcagno Cristina Femoni Marco Garavelli Maria Carmela Iapalucci Ivan Rivalta Stefano Zacchini 《Molecules (Basel, Switzerland)》2021,26(6)
The reaction of [Co(CO)4]− (1) with M(I) compounds (M = Cu, Ag, Au) was reinvestigated unraveling an unprecedented case of polymerization isomerism. Thus, as previously reported, the trinuclear clusters [M{Co(CO)4}2]− (M = Cu, 2; Ag, 3; Au, 4) were obtained by reacting 1 with M(I) in a 2:1 molar ratio. Their molecular structures were corroborated by single-crystal X-ray diffraction (SC-XRD) on isomorphous [NEt4][M{Co(CO)4}2] salts. [NEt4](3)represented the first structural characterization of 3. More interestingly, changing the crystallization conditions of solutions of 3, the hexanuclear cluster [Ag2{Co(CO)4}4]2− (5) was obtained in the solid state instead of 3. Its molecular structure was determined by SC-XRD as Na2(5)·C4H6O2, [PPN]2(5)·C5H12 (PPN = N(PPh3)2]+), [NBu4]2(5) and [NMe4]2(5) salts. 5 may be viewed as a dimer of 3 and, thus, it represents a rare case of polymerization isomerism (that is, two compounds having the same elemental composition but different molecular weights) in cluster chemistry. The phenomenon was further studied in solution by IR and ESI-MS measurements and theoretically investigated by computational methods. Both experimental evidence and density functional theory (DFT) calculations clearly pointed out that the dimerization process occurs in the solid state only in the case of Ag, whereas Cu and Au related species exist only as monomers. 相似文献
109.
Strong convergence of the discontinuous Galerkin scheme for the low regularity miscible displacement equations
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Vivette Girault Jizhou Li Beatrice M. Rivière 《Numerical Methods for Partial Differential Equations》2017,33(2):489-513
Strong convergence of the numerical solution to a weak solution is proved for a nonlinear coupled flow and transport problem arising in porous media. The method combines a mixed finite element method for the pressure and velocity with an interior penalty discontinuous Galerkin method in space for the concentration. Using functional tools specific to broken Sobolev spaces, the convergence of the broken gradient of the numerical concentration to the weak solution is obtained in the L2 norm. © 2016 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 489–513, 2017 相似文献
110.
In a previous communication we reported the site-directed generation of a heterodinuclear FeIIICuII complex ( 1 ) by using an asymmetric dinucleating ligand FloH. The iron(III) ion was introduced first on the preferential metal-binding site of the ligand that led to the formation of the thermodynamically favored five-membered chelate ring upon metal-binding. Copper(II) was introduced in the next step. The stepwise metalation strategy reported previously has now been extended to synthesize a series of heterodinuclear FeIIIMII [M = Mn ( 2 ), Fe ( 3 ), Co ( 4 ), and Ni ( 5 )] and FeIICuI ( 1a ) as well as the homodinuclear CuICuI ( 6 ) complexes. The complexes were characterized by X-ray crystallography (except for 1a and 6 ), and by a limited number of spectroscopic methods. Complex 1 with a labile solvent binding site at FeIII reacted with H2O2 to form a transient intermediate that showed reactivity typical of metal peroxide complexes. The metal centers in the complexes 2 – 5 are coordinatively saturated, and hence they showed no reactivity with H2O2. Complex 1a reacted with O2 via an intermolecular pathway to form a μ-oxo bridged tetrameric complex 1b , which was structurally characterized. This is in contrast to the homodinuclear CuICuI and heme FeIICuI cores, which prefer an intramolecular pathway for O2 activation. 相似文献