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941.
Boris Remenec Silvia Dulanská Veronika Pau?ová L’ubomír Mátel 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(2):403-407
This paper describes a simple and rapid method of 99Tc pre-concentration, separation and purification by using AnaLig? Tc02 gel in two stages or AnaLig? Tc02 gel in a first stage and TEVA? resin in a second stage, which are commercially available from IBC advanced technologies, Inc. and Eichrom technologies,
Inc., respectively. The method is suitable for analyzing large volume concentrate samples in a relatively short time. The
use and effectiveness of AnaLig? Tc02 and Eichrom’s TEVA? resin were successfully tested by analysis of evaporator concentrate samples which belong to the class of most difficult
matrices to analyze. 相似文献
942.
Bovine and human serum albumins catalyze the aldol reaction of aromatic aldehyedes and acetone, with saturation kinetics and moderate and opposite enantioselectivity. The reaction occurs at the binding site in domain IIa, and is inhibited by warfarin. Kinetic data are consistent with an enamine mechanism. The activity is conserved in a 103 aminoacid peptide derived from the albumin sequence. 相似文献
943.
Orihuela R Fernández B Palacios O Valero E Atrian S Watt RK Domínguez-Vera JM Capdevila M 《Chemical communications (Cambridge, England)》2011,47(44):12155-12157
Ferritin (Ft) interaction with the Zn-complexes of mammalian MT1, MT2 and MT3 metallothioneins (MT) leads to simultaneous Fe(II) and Zn(II) release. 相似文献
944.
Catalin Croitoru Silvia Patachia Attila Porzsolt Christian Friedrich 《Cellulose (London, England)》2011,18(6):1469-1479
In this paper, the influence of three alkylimidazolium-based ionic liquids with the same cation (1-ethyl-3-methylimidazolium)
and different anions (chloride, tetrafluoroborate and hexafluorophosphate) on the structure and properties of cellulose, have
been studied by using Fourier transform infrared spectroscopy measurements, fluorescence microscopy imaging, viscometric and
methylene blue sorption tests. Cellulose treated with ionic liquids showed better stability to UV light, as demonstrated by
the lower variations of the polymerization degree, carboxyl groups content, moisture index, crystallinity index, lateral order
index and allomorph index, with the increase of the UV exposure period, by comparing to non-treated cellulose. The results
show that the tested ionic liquids could be effective as “green” plasticizers and UV stabilizers for cellulose-based materials. 相似文献
945.
Piperno S Tse Sum Bui B Haupt K Gheber LA 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):1547-1550
We describe the fabrication of polymer nanofibers with entrapped molecularly imprinted polymer (MIP) nanoparticles and study their possible use in a fluorescence-based biosensor application. The MIP was imprinted with the fluorescent amino acid derivative dansyl-L-phenylalanine. Poly(vinyl alcohol) was used as a support for MIP nanoparticles because it is water-soluble and can be spun into very thin fibers. The fibers were characterized by atomic force microscopy and optical microscopy, and fluorescence microscopy was used for the characterization of target binding to the MIP. The fibers show close to 100% recovery upon extraction and rebinding of the target molecule. The selectivity of the system has been demonstrated through competitive binding experiments with nonfluorescent analogues boc-L-phenylalanine and boc-D-phenylalanine. 相似文献
946.
Detoni CB Souto GD da Silva AL Pohlmann AR Guterres SS 《Photochemistry and photobiology》2012,88(4):913-921
It is desirable and challenging to prevent E-resveratrol (E-RSV) from photoisomerizing to its Z-configuration to preserve its biological and pharmacological activities. The aim of this research was to evaluate the photostability of E-RSV-loaded supramolecular structures and the skin penetration profile of chemically and physically stable nanoestructured formulations. Different supramolecular structures were developed to act as carriers for E-RSV, that is, liposomes, polymeric lipid-core nanocapsules and nanospheres and solid lipid nanoparticles. The degrees of photostability of these formulations were compared with that of an ethanolic solution of E-RSV. The skin penetration profiles of the stable formulations were obtained using vertical diffusion cells (protected from light and under UVA radiation) with porcine skin as the membrane, followed by tape stripping and separation of the viable epidermis and dermis in a heated water bath. Photoisomerization was significantly delayed by the association of resveratrol with the nanocarriers independently of the supramolecular structure. Liposomes were the particles capable of maintaining E-RSV concentration for the longest time. On the other hand, E-RSV-loaded liposomes reduced in size showing low physical stability under UVA radiation. In the dark, the skin penetration profiles were very similar, but under UVA radiation the E-RSV-loaded nanocarriers showed increasing amounts in the total epidermis. 相似文献
947.
Conversion of methanol to hydrocarbons: how zeolite cavity and pore size controls product selectivity 总被引:1,自引:0,他引:1
Olsbye U Svelle S Bjørgen M Beato P Janssens TV Joensen F Bordiga S Lillerud KP 《Angewandte Chemie (International ed. in English)》2012,51(24):5810-5831
Liquid hydrocarbon fuels play an essential part in the global energy chain, owing to their high energy density and easy transportability. Olefins play a similar role in the production of consumer goods. In a post-oil society, fuel and olefin production will rely on alternative carbon sources, such as biomass, coal, natural gas, and CO(2). The methanol-to-hydrocarbons (MTH) process is a key step in such routes, and can be tuned into production of gasoline-rich (methanol to gasoline; MTG) or olefin-rich (methanol to olefins; MTO) product mixtures by proper choice of catalyst and reaction conditions. This Review presents several commercial MTH projects that have recently been realized, and also fundamental research into the synthesis of microporous materials for the targeted variation of selectivity and lifetime of the catalysts. 相似文献
948.
Ferrer S Martí S Moliner V Tuñón I Bertrán J 《Physical chemistry chemical physics : PCCP》2012,14(10):3482-3489
Salicylate synthase from Mycobacterium tuberculosis, MbtI, is a highly promiscuous Mg(2+) dependent enzyme with up to four distinct activities detected in vitro: isochorismate synthase (IS), isochorismate pyruvate lyase (IPL), salicylate synthase (SS) and chorismate mutase (CM). In this paper, Molecular Dynamic (MD) simulations employing hybrid quantum mechanics/molecular mechanics (QM/MM) potentials have been carried out to get a detailed knowledge of the IS and the IPL activities at the molecular level. According to our simulations, the architecture of the MbtI active site allows catalyzing the two reactions: the isochorismate formation, by means of a stepwise mechanism, and the salicylate production from isochorismate, that appears to be pericyclic in nature. Findings also explain the role of the magnesium cation and the pH dependence activity experimentally observed in MbtI. Mg(2+) would be polarizing and pre-organizing the substrate and active site, as well as shifting the pK(a) values of key active site residues. 相似文献
949.
Silvia Tardioli Cees Gooijer Gert van der Zwan 《Journal of Raman spectroscopy : JRS》2011,42(5):1016-1024
Ultraviolet Resonance Raman (UVRR) spectroscopy—a Raman technique that combines high sensitivity with high selectivity and does not suffer from background fluorescence—is applied to the fluorescent H1 antihistamines tripelennamine (TRP) and mepyramine (MEP) in aqueous solution to elucidate their molecular structure as a function of pH. In a previous investigation of these compounds (C. Tardioli, G. Gooijer G. van der Zwan, J. Phys. Chem. B, 113 , (2009), 6949), the presence of gauche conformers caused by intramolecular interaction of the protonated alkylamine tail with the pyridine nitrogen was assumed to explain the pH dependence of the fluorescence properties. In order to validate this assumption, use is made of the resonant excitation of the aminopyridine chromophore in TRP and MEP. In that way, structural information associated with the vibrations of that moiety can be obtained, and the changes it undergoes upon protonation can be monitored. Assignment of the vibrations was achieved with the help of a number of other compounds, and quantum chemical calculations. N,N‐Dimethylaminopyridine (2DMP) and its mono‐protonated form (2DMPH+) were investigated, since this molecule was shown to have optical properties closely resembling those of the aminopyridine moiety in TRP and MEP. Assignment of the vibrations of 2DMP was accomplished by comparison with the resonance Raman spectra of two other reference structures, 2‐aminopyridine and dimethylaniline—for which ordinary Raman data are available—and by Gaussian calculations. UVRR spectra of TRP and MEP could be readily interpreted on the basis of vibrational assignments of the parent chromophores, i.e. 2DMP and 2DMPH+. Vibrations of the aminopyridine chromophore in TRP and MEP at neutral pH, where the aminoalkyl chain is protonated, are modified when compared to the vibrational pattern recorded for a fully neutral molecule in alkaline solution. This implies an electronic redistribution in the ring originating from internal hydrogen bonding between the aminoalkyl tail and the aminopyridine chromophore. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
950.
José M. García Santos Miguel Blanquer Silvia Torres del Río Francisca Iniesta Joaquín Gomez Espuch Miguel Ángel Pérez-Espejo Salvador Martínez José M. Moraleda 《Magnetic resonance imaging》2013,31(8):1298-1308
ObjectiveTo report MRI spinal changes after surgical infusion of bone marrow stem cells (BMSc) in ALS patients and assess their correlation with clinical events and functional performance.MethodsBMSc were surgically injected in the thoracic spinal cord of 11 ALS patients (6/5 male/female; median age 46 years). We performed first-week and third, sixth, ninth and twelfth post-surgical months spinal MRIs. The spinal changes in the postsurgical week and follow-up MRIs, as well as clinical events, functional scales and respiratory and electromyography data, were longitudinally monitored. Correlations between the imaging and clinical data were evaluated with the Spearman's test.ResultsTransient extradural fluid collections (100%), transient spinal cord T2 hyperintensity (81.8%), and chronic spinal cord deformities (63.6%) were the dominating MRI changes. Spinal cord hemorrhages (27.3%) and cystic myelomalacia (1/11 patients) were important although unusual findings. During the follow-up, minor adverse events of mild to moderate intensity eventually improved. Initial and follow-up imaging scores showed a strongly positive correlation (r 0.879, P < 0.001). The initial and delayed clinical scores did not correlate. There was no significant correlation between any of the imaging scores and clinical data.ConclusionsInfusion of BMSc produces a variety of spinal changes apparently unrelated with clinical events and disease worsening. 相似文献