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61.
Abolghasem Moghimi Robabeh Alizadeh Hossein Aghabozorg Abbas Shockravi M. Carla Aragoni Francesco Demartin Francesco Isaia Vito Lippolis Andrew Harrison A. Shokrollahi Mojtaba Shamsipur 《Journal of Molecular Structure》2005,750(1-3):166-173
The one-pot reaction between the novel proton transfer compound (pydaH2)2+(phendc)2−, LH2, and Cu(II) afforded the compounds (pydaH)2[Cu(phendc)2]·10H2O, 1, and (pydaH)2[Cu(phendc)(phendcH)]2·5H2O, 2, where pyda=2,6-diaminopyridine, and phendcH2=1,10-phenanthroline-2,9-dicarboxylic acid. The single crystal X-ray diffraction analysis of 1 and 2 revealed that these are two novel self-assembled 3D Cu(II) complex-organo-networks, in which (pydaH)+ ions and [Cu(phendc)2]2− or complex units are held together by ion pairing, H-bonding, and π–π interactions. Magnetic measurements over the temperature range 1.8–310 K revealed no significant magnetic coupling between Cu(II) centers in 1 or 2. 相似文献
62.
Veysel T. Yilmaz Serkan Guney Omer Andac William T. A. Harrison 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(8):m427-m430
The title complexes [M(sac)2(mpy)2] [sac is saccharinate (C7H4NO3S) and mpy is 2‐pyridylmethanol (C6H7NO)], with M = ZnII and CdII, are isostructural and consist of neutral molecules. The ZnII or CdII cations are octahedrally coordinated by the two neutral mpy and two anionic sac ligands. The mpy ligand acts as a bidentate donor through the amine N and hydroxyl O atoms. The sac ligands exhibit an ambidentate coordination behaviour; one is N‐coordinated and the other is O‐coordinated within the same coordination octahedron. The crystal packing is determined by C—H?O‐type hydrogen bonding, as well as by weak py–py and sac–sac aromatic π–π‐stacking interactions. 相似文献
63.
Anthony B. Cornwell Philip G. Harrison John A. Richards 《Journal of organometallic chemistry》1977,140(3):273-287
The reaction of organotin chlorides with the lithium salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) or hexaalkylditins with TCNQ yield stable organotin-substituted free radicals of the types R3SnTCNQ. (R = Me, n-Pr, n-Bu) and Me2Sn(TCNQ.)2. The reaction of hexaphenylditin with TCNQ yields a (σ → π) charge transfer complex of stoichiometry (Ph3SnSnPh3)·TCNQ, whilst [Me2SnCl(terpyridyl)+](TCNQ-·) was isolated from the reaction of [Me2SnCl(terpyridlyl)+][Me2SnCl3-] and LiTCNQ. The oxidation of hexaalkylditins by tetracyanoethylene (TCNE) yields stable free radicals of the type R3SnTCNE·, but treatment with 2,3,5,6-tetrachlorobenzoquinone yields either R3SnOC6Cl4O·-p (R = Me) or R3SnOC6Cl4OSnR3-p (R = n-Bu, Ph). Tin-119 Mössbauer spectroscopy shows that the derivatives R3SnTCNQ· and R3TCNE· have trigonally-bipyramidally coordinated tin with planar [SnC3] skeletons and bridging [TCNQ·] and [TCNE·] groups forming infinite one-dimensional chain structures. Me3SnOC6Cl4O·-p was inferred to possess a similar structure but with oxy bridges forming chains with a Sn---O---Sn---O backbone. Me2Sn(TCNQ·)2 has a structure intermediate between tetrahedral and octahedral with a non-linear MeSnMe unit and anisobidentate chelation by two TCNQ groups. The TCNQ derivatives were of two types: (i) “green” or “brown”, indicative of delocalisation of the Ione electron over the cyanoquinone ligand, and (ii) a “blue” form in which spin-pairing of the Ione electron between adjacent organic groups takes place. Me3SnTCNQ· may exist in both forms depending upon the mode of preparation. 相似文献
64.
The appearance potentials for the [R'CO2H2]+ ion produced in the fragmentation process \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm R}^{\rm '} {\rm CO}_{\rm 2} {\rm R}} \right]_{}^{_.^ + } $\end{document} → [R'CO2H2]++[R? 2H] have been measured using mono-energetic electron impact techniques for ethyl, n-propyl, and i-propyl formates and acetates. The results indicate that at the threshold the product ion has the protonated acid structure with the hydrogen on the carbonyl and not the hydroxyl group, and that the neutral product for the propyl esters is the allyl radical and not the cyclopropyl radical. For the propyl formates and acetates the appearance potential of the [R'CO2H2]+ ion is identical with the adiabatic ionization potential of the parent ester (measured by photoelectron spectroscopy) indicating that fragmentation occurs for ground state molecular ions. A two-step mechanism is proposed to rationalize the results. 相似文献
65.
Conversion of -methyl-hydroxyisopropyldihydrofuro-4-quinolones ( and ) into allylic acetate derivatives ( and ) was effected by Ac2O-pyridine-HCl; subsequent hydrolysis and methylation furnished the alkaloids, ptelefoline () and ptelefoline methyl ether (). Mechanisms of the reactions are discussed. 相似文献
66.
Chrif F. Matta Christopher N. Cow Paul H. M. Harrison 《Journal of Molecular Structure》2003,660(1-3):81-97
X-ray crystallography and theoretical analysis were applied to explore the molecular basis for the efficient and selective Claisen-like condensations of diacylglycolurils. The crystal structures of 1-acetyl-6-benzoyl-3,4,7,8-tetramethylglycoluril (4b), and of 1-(3′-oxo-3′-phenylpropionyl)-3,4,7,8-tetramethylglycoluril (5b), the product of base-promoted intramolecular condensation of 4b, were obtained by X-ray diffraction. The acetyl (Ac) group in 4b is essentially coplanar with the attached tetrahydroimidazolone ring of the glycoluril core (τ=7°), while the benzoyl (Bz) group is twisted by τ=45° relative to a plane through the ring to which it is bonded. Product 5b contains a flat amide (τ=7°). Ab initio energy optimizations of the experimental structures for 4b and 5b give optimized geometries which are not dramatically altered, suggesting that crystal packing effects are small. An atoms-in-molecules study of the delocalization of the Fermi hole reveals that electrons in the Bz C=O group of 4b are delocalized into the phenyl ring as well as into the urea moiety of the glycoluril core. This effect stabilizes the Bz over the Ac carbonyl group, and accounts for selective twisting of the Bz group. The Laplacian of the electron density reveals a non-bonded valence shell charge concentration at O of the Ac group, corresponding to a lone-pair region, aligned with a charge depletion in the valence shell of the Bz C=O carbon [(C15–O16C18)=113°]. The angle of approach [(O16C18=O19)] is 100°, equal to the angle for ideal nucleophilic attack on a carbonyl group. Oxygen atom O16 is thus poised to attack C18; only the O16C18 distance (3.248 Å) seems to prevent reaction. These results suggest that the same distance restraint may prevent O-acylation in the enolate intermediate 6b derived from4b. By contrast, the transition state for C-acylation, leading from 6b towards product 5b requires a different geometry, which may explain the observed selectivity for C-acylation in this enolate. The results show that, as 4b is converted to 5b, amide torsional strain is relieved, which may account for the high reactivity of 4b and the efficiency and irreversibility of this condensation process. This study provides a starting point for quantitative correlation of substrate structure in diacylglycolurils with kinetic data for the rearrangement reaction. 相似文献
67.
Wiest O Harrison CB Saettel NJ Cibulka R Sax M König B 《The Journal of organic chemistry》2004,69(24):8183-8185
Two new artificial photolyase models that recognize pyrimidine dimers in protic and aprotic organic solvents as well as in water through a combination of charge and hydrogen-bonding interactions and use a mimic of the flavine to achieve repair through reductive photoinduced electron transfer are presented. Fluorescence and NMR titration studies show that it forms a 1:1 complex with pyrimidine dimers with binding constants of approximately 10(3) M(-1) in acetonitrile or methanol, while binding constants in water at pH 7.2 are slightly lower. Excitation of the complex with visible light leads to clean and rapid cycloreversion of the pyrimidine dimer through photoinduced electron transfer catalysis. The reaction in water is significantly faster than in organic solvents. The reaction slows down at higher conversions due to product inhibition. 相似文献
68.
[reaction: see text] Cyclic ene-N-p-toluenesulfonamides tethered to an electron-deficient alkyne undergo cycloisomerizations readily under the influence of catalytic Pt(II) salts (PtCl2 or [dppbPtmu-OH]2(BF4)2) or AgOTf. Yields for this process range from 47% to 99%. The resulting functionalized 2-azahydrindans can be reacted further using the Diels-Alder reaction. Tandem cycloisomerization-cycloaddition reactions in one pot generate highly functionalized 1-azadecalin ring systems in a highly stereocontrolled manner. 相似文献
69.
GABA(C) (rho) receptors are members of the Cys-loop superfamily of neurotransmitter receptors, which includes nicotinic acetylcholine (nACh), 5-HT(3), and glycine receptors. As in other members of this family, the agonist binding site of GABA(C) receptors is rich in aromatic amino acids, but while other receptors bind agonist through a cation-pi interaction to a tryptophan, the GABA(C) binding site has tyrosine at the aligning positions. Incorporating a series of tyrosine derivatives at position 198 using unnatural amino acid mutagenesis reveals a clear correlation between the cation-pi binding ability of the side chain and EC(50) for receptor activation, thus demonstrating a cation-pi interaction between a tyrosine side chain and a neurotransmitter. Comparisons among four homologous receptors show variations in cation-pi binding energies that reflect the nature of the cationic center of the agonist. 相似文献
70.
William T. A. Harrison R. Alan Howie Janet M. S. Skakle James L. Wardell 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(6):m351-m354
The title compounds, [Sn(C6H5)2(C5H4S5)] and [Sn(C5H4S5)2], respectively, are of interest because they can be regarded as intermediate in nature between chelates and heterocyclic compounds containing the C3S5 fragment. In contrast with the essentially normal bond lengths and angles within the molecules, the molecular conformations are somewhat unexpected, as are the intermolecular contacts found in the case of the latter compound. 相似文献