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141.
Stanek J Augustyniak R Koźmiński W 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2012,214(1):91-102
The development of non-uniform sampling (NUS) strategies permits to obtain high-dimensional spectra with increased resolution in significantly reduced experimental time. We extended a previously proposed signal separation algorithm (SSA) to process sparse four-dimensional NMR data. It is employed for two experiments carried out for a partially unstructured 114-residue construct of chicken Engrailed 2 protein, namely 4D HCCH-TOCSY and 4D C,N-edited NOESY. The SSA allowed us to obtain high-quality spectra using only as little as 0.16% of the available samples, with low sampling artefacts approaching the thermal noise level in most spectral regions. It is demonstrated that NUS 4D HCCH-TOCSY is dominated by sampling noise and requires efficient artefact suppression. On the other hand, 4D C,N-edited NOESY is a particularly attractive experiment for NUS, as the absence of diagonal peaks renders the problem of artefacts less critical. We also present a transverse-relaxation optimized sequence for HMQC that is especially designed for longer evolution periods in the indirectly detected proton dimension in high-dimensional pulse sequences. In conjunction with novel sampling strategies and efficient processing methods, this improvement enabled us to obtain unique structural information about aliphatic-amide contacts. 相似文献
142.
Luchowski R Sabnis S Szabelski M Sarkar P Raut S Gryczynski Z Borejdo J Bojarski P Gryczynski I 《Journal of luminescence》2010,130(12):2446-2451
Concentration is a key determining factor in the fluorescence properties of organic fluorophores. We studied self-quenching of disodium fluorescein (uranin) fluorescence in polyvinyl alcohol (PVA) thin films. The concentration dependent changes in brightness and anisotropy were followed by a lifetime decrease. We found that at a concentration of 0.54 M, the lifetime decreases to 7 ps. At a concentration of 0.18 M the lifetime was 10 ps with the relatively high quantum yield of 0.002. In these conditions the fluorescence intensity decay was homogeneous (well approximated by a single lifetime). We realized that such a sample was an ideal fluorescence lifetime standard for spectroscopy and microscopy, and therefore characterized instrument response functions for a time-domain technique. We show that self-quenched uranin enables measurements free of the color effect, making it a superior choice for a lifetime reference over scattered light. 相似文献
143.
Jourdain V Simpson ET Paillet M Kasama T Dunin-Borkowski RE Poncharal P Zahab A Loiseau A Robertson J Bernier P 《The journal of physical chemistry. B》2006,110(20):9759-9763
We demonstrate the use of sequential catalytic growth to encapsulate iron, nickel-iron, and iron-cobalt phosphide catalyst nanoparticles periodically along the entire lengths of carbon nanotubes. Investigations by local electron spectroscopies and electron diffraction reveal the compositions and crystal structures of the encapsulated particles. Significantly, high spatial resolution magnetic characterization using magnetic force microscopy and off-axis electron holography demonstrates that encapsulated iron-cobalt phosphide nanoparticles are ferromagnetic at room temperature, in accordance with the properties of bulk metal phosphides of the same structure and composition. 相似文献
144.
145.
A fundamental aim in the field of electrochemistry is to investigate electron transfer events caused by electrode processes, which are more commonly described as redox reactions. In this short review, an overview of the use of electrochemical redox reactions in the realm of organic synthesis is given. These reactions can be divided into three subcategories: cathodic reduction, anodic oxidation, and a paired approach. This short review illustrates the basic schemes of these reactions and introduces representative examples that have been reported in the past 2 years, with a particular emphasis on the development of novel reactions. 相似文献
146.
Radaram B Ivie JA Singh WM Grudzien RM Reibenspies JH Webster CE Zhao X 《Inorganic chemistry》2011,50(21):10564-10571
The synthesis, characterization, and water oxidation activity of mononuclear ruthenium complexes with tris(2-pyridylmethyl)amine (TPA), tris(6-methyl-2-pyridylmethyl)amine (Me(3)TPA), and a new pentadentate ligand N,N-bis(2-pyridinylmethyl)-2,2'-bipyridine-6-methanamine (DPA-Bpy) have been described. The electrochemical properties of these mononuclear Ru complexes have been investigated by both experimental and computational methods. Using Ce(IV) as oxidant, stoichiometric oxidation of water by [Ru(TPA)(H(2)O)(2)](2+) was observed, while Ru(Me(3)TPA)(H(2)O)(2)](2+) has much less activity for water oxidation. Compared to [Ru(TPA)(H(2)O)(2)](2+) and [Ru(Me(3)TPA)(H(2)O)(2)](2+), [Ru(DPA-Bpy)(H(2)O)](2+) exhibited 20 times higher activity for water oxidation. This study demonstrates a new type of ligand scaffold to support water oxidation by mononuclear Ru complexes. 相似文献
147.
Jamali S Czerwieniec R Kia R Jamshidi Z Zabel M 《Dalton transactions (Cambridge, England : 2003)》2011,40(36):9123-9130
The binuclear cyclometalated complexes [Pt(2)Me(2)(ppy)(2)(μ-dppm)], 1a, and [Pt(2)Me(2)(bhq)(2)(μ-dppm)], 1b, in which ppy = 2-phenylpyridyl, bhq = benzo{h}quinoline and dppm = bis(diphenylphosphino)methane, were synthesized by the reaction of [PtMe(SMe(2))(ppy)] or [PtMe(SMe(2))(bhq)] with 1/2 equiv of dppm at room temperature, respectively. Complexes 1a and 1b were fully characterized by multinuclear ((1)H, (31)P, (13)C, and (195)Pt) NMR spectroscopy and were further identified by single crystal X-ray structure determination. A comparison of the intramolecular Pt-Pt and π-π interactions in complexes 1a and 1b has been made on the basis of data on crystal structures and wave functions analysis. The binuclear complexes 1a and 1b are luminescent in the solid state, and showing relatively intense orange-red emissions stemming from (3)MMLCT excited states. The reaction of complex 1b with excess MeI gave the binuclear cyclometalated Pt(IV)-Pt(IV) complex [Pt(2)Me(4)(bhq)(2)(μ-I)(2)], 2. Crystal structure of complex 2 shows intermolecular C-H···I and C-H···π interactions in solid state. 相似文献
148.
The intermolecular non-covalent interactions in aminonitromethylbenzenes namely 2-methyl-4-nitroaniline, 4-methyl-3-nitroaniline,
2-methyl-6-nitroaniline, 4-amino-2,6-dinitrotoluene, 2-methyl-5-nitroaniline, 4-methyl-2-nitroaniline, 2,3-dimethyl-6-nitroaniline,
4,5-dimethyl-2-nitroaniline and 2-methyl-3,5-dinitroaniline were studied by quantum mechanical calculations at RHF/311++G(3df,2p)
and B3LYP/311++G(3df,2p) level of theory. The calculations prove that solely geometrical study of hydrogen bonding can be
very misleading because not all short distances (classified as hydrogen bonds on the basis of interaction geometry) are bonding
in character. For studied compounds interaction energy ranges from 0.23 kcal mol−1 to 5.59 kcal mol−1. The creation of intermolecular hydrogen bonds leads to charge redistribution in donors and acceptors. The Natural Bonding
Orbitals analysis shows that hydrogen bonds are created by transfer of electron density from the lone pair orbitals of the
H-bond acceptor to the antibonding molecular orbitals of the H-bond donor and Rydberg orbitals of the hydrogen atom. The stacking
interactions are the interactions of delocalized molecular π-orbitals of the one molecule with delocalized antibonding molecular
π-orbitals and the antibonding molecular σ-orbital created between the carbon atoms of the second aromatic ring and vice versa.
相似文献
149.
Marta Sosnowska Monika Goral-Kurbiel Magdalena Skunik-Nuckowska Rafal Jurczakowski Pawel J. Kulesza 《Journal of Solid State Electrochemistry》2013,17(6):1631-1640
Preparation and electrochemical behavior of new hybrid materials composed of multi-walled carbon nanotubes (CNTs) that were derivatized with poly(diallyldimethylammonium) chloride and modified with vanadium-mixed addenda Dawson-type heteropolytungstate, [P2W17VO62]8?, is described here. These nanostructured composite systems exhibited fast dynamics of charge propagation. They were characterized by the transport (effectively diffusional) kinetic parameter of approximately 8?×?10?8 cm?2 s?1/2 and the specific capacitance parameter of 82 F g?1 (at the charging/discharging current of 200 mA g?1). The latter parameter for bare CNTs was found to be only 50 F g?1 under analogous conditions. These observations were based on the results of galvanostatic charging–discharging, cyclic voltammetric, and AC impedance spectroscopic measurements. The improved capacitance properties were attributed to the systems’ pseudocapacitive features originating from the fast redox transitions of the [P2W17VO62]8? polyanions. In addition to the fast redox conduction, the proposed organic–inorganic hybrid materials exhibited interesting electrocatalytic activity toward reduction of bromate in the broad concentration range (sensitivity, 0.24 mA cm?2 mmol?1 dm3). 相似文献
150.
H. Charles Manning Mingfeng Bai Rafal Lisiak Darryl J. Bornhop 《Tetrahedron letters》2005,46(28):4707-4710
Phosphonic acid appended tetraazacyclododecane (cyclen)-based macrocycles are attractive metal-ion chelators for diagnostic imaging and therapeutic delivery. Here, we report a novel P-protected methodology that facilitates the rapid synthesis and purification of targeted phosphonic acid bearing macrocycles. Purification of these intermediates is facile, and deprotection using neat TFA is rapid, yet mild enough to preserve the integrity of delicate peptides and/or targeting moieties. 相似文献