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101.
Piper DJ Barbante GJ Brack N Pigram PJ Hogan CF 《Langmuir : the ACS journal of surfaces and colloids》2011,27(1):474-480
The electrodeposition of the electrochemiluminescent (ECL) ruthenium complex, bis(2,2'-bipyridyl)(4'-(4-aminophenyl)-2,2'-bipyridyl)ruthenium(II), [Ru(bpy)(2)(apb)](2+), via the in situ formation of a diazonium species from aqueous media is reported. Surface characterization undertaken using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) determined that the layer is bound to the substrate via azo bonding. The layer displays good ECL activity and is stable over a long period of time. The excellent potential of this system for ECL sensing applications is demonstrated using the well-known ECL coreactant 2-(dibutylamino)ethanol (DBAE) as a model analyte, which can be detected to a level of 10 nM with a linear range between 10(-8) and 10(-4) M. 相似文献
102.
Shavorskiy A Aksoy F Grass ME Liu Z Bluhm H Held G 《Journal of the American Chemical Society》2011,133(17):6659-6667
The coadsorption of water with organic molecules under near-ambient pressure and temperature conditions opens up new reaction pathways on model catalyst surfaces that are not accessible in conventional ultrahigh-vacuum surface-science experiments. The surface chemistry of glycine and alanine at the water-exposed Cu{110} interface was studied in situ using ambient-pressure photoemission and X-ray absorption spectroscopy techniques. At water pressures above 10(-5) Torr a significant pressure-dependent decrease in the temperature for dissociative desorption was observed for both amino acids, accompanied by the appearance of a new CN intermediate, which is not observed for lower pressures. The most likely reaction mechanisms involve dehydrogenation induced by O and/or OH surface species resulting from the dissociative adsorption of water. The linear relationship between the inverse decomposition temperature and the logarithm of water pressure enables determination of the activation energy for the surface reaction, between 213 and 232 kJ/mol, and a prediction of the decomposition temperature at the solid-liquid interface by extrapolating toward the equilibrium vapor pressure. Such experiments near the equilibrium vapor pressure provide important information about elementary surface processes at the solid-liquid interface, which can be retrieved neither under ultrahigh vacuum conditions nor from interfaces immersed in a solution. 相似文献
103.
Kersten H Derpmann V Barnes I Brockmann KJ O'Brien R Benter T 《Journal of the American Society for Mass Spectrometry》2011,22(11):2070-2081
We report on the development of a novel atmospheric pressure photoionization setup and its applicability for in situ degradation
product studies of atmospherically relevant compounds. A custom miniature spark discharge lamp was embedded into an ion transfer
capillary, which separates the atmospheric pressure from the low pressure region in the first differential pumping stage of
a conventional atmospheric pressure ionization mass spectrometer. The lamp operates with a continuous argon flow and produces
intense light emissions in the VUV. The custom lamp is operated windowless and efficiently illuminates the sample flow through
the transfer capillary on an area smaller than 1 mm2. Limits of detection in the lower ppbV range, a temporal resolution of milliseconds in the positive as well as the quasi
simultaneously operating negative ion mode, and a significant reduction of ion transformation processes render this system
applicable to real time studies of rapidly changing chemical systems. The method termed capillary atmospheric pressure photo
ionization (cAPPI) is characterized with respect to the lamp emission properties as a function of the operating conditions,
temporal response, and its applicability for in situ degradation product studies of atmospherically relevant compounds, respectively. 相似文献
104.
Korswagen HC 《Chemistry & biology》2011,18(4):485-410
Studies using chemical inhibitors have suggested that p38 MAP kinase is a key regulator of Wnt/β-catenin signaling. In this issue, Verkaar et?al. (2011) show that cross-reactivity of p38 inhibitors with casein kinase Iδ/? is responsible for Wnt/β-catenin pathway inhibition. 相似文献
105.
Sharma GV Chary DH Chandramouli N Achrainer F Patrudu S Zipse H 《Organic & biomolecular chemistry》2011,9(11):4079-4084
Radical cyclization reactions were performed by 5-exo-dig mode to yield cis-fused bicyclic systems, leading to the synthesis of bis-butyrolactone class of natural products. The study was aimed at understanding the impact of alkyl side chains of furanoside ring systems in L-ara configuration on the radical cyclization. It was amply demonstrated by experimental studies that the increase in the length of the alkyl side chain has an effect on the cyclization: while efficient cyclization reactions could be realized with methyl and ethyl side chains, the yields were significantly reduced in the case of n-pentyl side chain. Theoretical studies using DFT and (RO)MP2 methods were carried out to analyze the influence of the substitution pattern on the cyclization barriers. 相似文献
106.
Panda SK Al-Hajji AA Müller H Koseoglu OR 《Analytical and bioanalytical chemistry》2011,400(5):1231-1239
In the present study, we established a statistical distribution pattern of indigenous sulfur, nitrogen, and oxygen species in Arabian Heavy crude oil and its distilled fractions: naphtha, gas oil, and vacuum gas oil (VGO) using chemical derivatization with methyl iodide and subsequent characterization by positive electrospray Fourier transform mass spectrometry. It was observed that sulfur species for naphtha and gas oil were accumulated at lower double bond equivalent values and at lower carbon numbers compared to VGO, whereas crude oil encompassed a complete range of the sulfur species detected in all distilled fractions. Moreover, the use of alumina column chromatography and ligand exchange chromatography (LEC) on a palladium-bonded silica stationary phase revealed additional structural features of sulfur heterocycles in terms of condensed and non-condensed thiophenes. During LEC separation, in addition to sulfur heterocycles, interesting results were obtained for oxygen-containing compounds. Ortho-substituted alkyl phenols were separated from meta- and para-substituted alkyl phenols on a palladium-bonded silica stationary phase. 相似文献
107.
Coppage R Slocik JM Briggs BD Frenkel AI Heinz H Naik RR Knecht MR 《Journal of the American Chemical Society》2011,133(32):12346-12349
The ability to control the size, shape, composition, and activity of nanomaterials presents a formidable challenge. Peptide approaches represent new avenues to achieve such control at the synthetic level; however, the critical interactions at the bio/nano interface that direct such precision remain poorly understood. Here we present evidence to suggest that materials-directing peptides bind at specific time points during Pd nanoparticle (NP) growth, dictated by material crystallinity. As such surfaces are presented, rapid peptide binding occurs, resulting in the stabilization and size control of single-crystal NPs. Such specificity suggests that peptides could be engineered to direct the structure of nanomaterials at the atomic level, thus enhancing their activity. 相似文献
108.
Barbante GJ Hogan CF Wilson DJ Lewcenko NA Pfeffer FM Barnett NW Francis PS 《The Analyst》2011,136(7):1329-1338
Using a combination of electrochemical, spectroscopic and computational techniques, we have explored the fundamental properties of a series of ruthenium diimine complexes designed for coupling with other molecules or surfaces for electrochemiluminescence (ECL) sensing applications. With appropriate choice of ligand functionality, it is possible to manipulate emission wavelengths while keeping the redox ability of the complex relatively constant. DFT calculations show that in the case of electron withdrawing substituents such as ester or amide, the excited state is located on the substituted bipyridine ligand whereas in the case of alkyl functionality it is localised on a bipyridine. The factors that dictate annihilation ECL efficiency are interrelated. For example, the same factors that determine ΔG for the annihilation reaction (i.e. the relative energies of the HOMO and LUMO) have a corresponding effect on the energy of the excited state product. As a result, most of the complexes populate the excited state with an efficiency (Φ(ex)) of close to 80% despite the relatively wide range of emission maxima. The quantum yield of emission (Φ(p)) and the possibility of competing side reactions are found to be the main determinants of ECL intensity. 相似文献
109.
110.