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991.
Stefano Marchese Daniela Perret Eleonora Bafile Alessandra Gentili Fulvia Caretti Marco Berardino 《Chromatographia》2009,70(5-6):761-767
This paper describes a new method for the rapid extraction and unequivocal confirmation of herbicides chlormequat and mepiquat in wheat flours and various flours utilized in infant foods. The highly automated extraction procedure is based on accelerated solvent extraction, followed by liquid chromatography-tandem mass spectrometry as a confirmatory analysis. Typical recoveries from flours and baby food samples ranged from 83 to 99% at a fortification level of 10 ppb, corresponding to the maximum residue limits established by the European Union; while relative standard deviations (RSD) were less than 10% for all samples. The limit of detection (signal-to-noise ratio = 3) of the method for the considered phenols in baby food samples are less than 0.1 μg g?1. Traces of the selected herbicides have been detected in about 50% of baby foods, bought from different Roman supermarkets and butcher shops, applying the described methodology. 相似文献
992.
Corina Flangea Alina F. Serb Catalin Schiopu Sorin Tudor Eugen Sisu Daniela G. Seidler Alina D. Zamfir 《Central European Journal of Chemistry》2009,7(4):752-759
Sulfation pattern within chondroitin sulfate (CS) glycosaminoglycan (GAG) chains is an important post-translational modification
that regulates their interaction with proteins. In this context, development of highly efficient and reproducible analytical
methods for the investigation of CS sulfation patterns is of high necessity. In this study we report a novel method for straightforward
determination of N-acetylgalactosamine (GalNAc) sulfation sites in chondroitin sulfate disaccharides. Our protocol involves
combining fully automated chip-based nanoelectrospray (nanoESI) for analyte infusion and ionization in negative ion mode with
multistage (MSn) collision-induced dissociation (CID) high capacity ion trap (HCT) mass spectrometry for generation of sequence ions diagnostic
for identification of sulfate ester group position within GalNAc residues. The feasibility of this approach is here demonstrated
on chondroitin 6-O-sulfate and chondroitin 4-O-sulfate disaccharides. Fragmentation patterns obtained by MS2 and MS3 sequencing stages provided first mass spectrometric data from which sulfation site(s) within GalNAc monosaccharide ring could
be unequivocally deciphered. Hence, the method allowed discriminating 4S/6S sulfation sites solely on the basis of MS and
multistage MS evidence.
相似文献
993.
Denise da Gama Jaén Batista Patrícia Bernardino da Silva Daniela R. Lachter Renata S. Silva Ricardo Q. Aucelio Sonia R.W. Louro Heloisa Beraldo Maria de Nazaré C. Soeiro Letícia R. Teixeira 《Polyhedron》2010
Thiosemicarbazones are known to be active against different pathogenic microorganisms including Trypanosoma cruzi, the etiological agent of Chagas disease. In the search for new therapeutic drugs against this illness, the complexes [Mn(H4NO2Fo4M)2Cl2] (1), [Mn(H4NO2Ac4M)2Cl2] (2) and [Mn(H4NO2Bz4M)2Cl2] (3) of N4-methyl-4-nitrobenzaldehyde thiosemicarbazone (H4NO2Fo4M), N4-methyl-4-nitroacetophenone thiosemicarbazone (H4NO2Ac4M) and N4-methyl-4-nitrobenzophenone thiosemicarbazone (H4NO2Bz4M) were obtained and screened in vitro against bloodstream and intracellular forms of T. cruzi. H4NO2Fo4M, H4NO2Ac4M and their Mn(II) complexes displayed poor effect on bloodstream trypomastigotes, with IC50 values ranging from 68 to >200 μM. However, although H4NO2Bz4M was also not active, its corresponding Mn(II) complex presented high effect on this T. cruzi form, with an IC50 value of 19 μM. The effect of complex (3), against trypomastigotes of T. cruzi supports further in vitro as well as in vivo studies. 相似文献
994.
Elisandra Rigo André E. Polloni Daniela Remonatto Francieli Arbter Silvana Menoncin J. Vladimir Oliveira Débora de Oliveira Helen Treichel Susana J. Kalil Jorge L. Ninow Marco Di Luccio 《Applied biochemistry and biotechnology》2010,162(7):1881-1888
The main objective of this work was the isolation and screening of microorganisms with potential for producing lipases for the synthesis of fatty esters as well as evaluating the specificity of the enzymes produced, using different alcohols (methanol, ethanol, n-propanol, and butanol) and fatty acids (oleic and lauric acids) as substrates. Promising biocatalysts for organic synthesis were obtained in this work. The isolated strains 69F and 161Y showed ability to efficiently catalyze the reaction for production of n-propyl oleate. Other strains can also be considered of potential interest, as 74F, 111Y, and 186Y. The future development of production using different substrates could result in cheap crude lipase of high importance to industrial applicability. 相似文献
995.
Binolfi A Rodriguez EE Valensin D D'Amelio N Ippoliti E Obal G Duran R Magistrato A Pritsch O Zweckstetter M Valensin G Carloni P Quintanar L Griesinger C Fernández CO 《Inorganic chemistry》2010,49(22):10668-10679
The aggregation of alpha-synuclein (AS) is a critical step in the etiology of Parkinson's disease (PD). A central, unresolved question in the pathophysiology of PD relates to the role of AS-metal interactions in amyloid fibril formation and neurodegeneration. Our previous works established a hierarchy in alpha-synuclein-metal ion interactions, where Cu(II) binds specifically to the protein and triggers its aggregation under conditions that might be relevant for the development of PD. Two independent, non-interacting copper-binding sites were identified at the N-terminal region of AS, with significant difference in their affinities for the metal ion. In this work we have solved unknown details related to the structural binding specificity and aggregation enhancement mediated by Cu(II). The high-resolution structural characterization of the highest affinity N-terminus AS-Cu(II) complex is reported here. Through the measurement of AS aggregation kinetics we proved conclusively that the copper-enhanced AS amyloid formation is a direct consequence of the formation of the AS-Cu(II) complex at the highest affinity binding site. The kinetic behavior was not influenced by the His residue at position 50, arguing against an active role for this residue in the structural and biological events involved in the mechanism of copper-mediated AS aggregation. These new findings are central to elucidate the mechanism through which the metal ion participates in the fibrillization of AS and represent relevant progress in the understanding of the bioinorganic chemistry of PD. 相似文献
996.
We report on the use of optical Faraday rotation to monitor the nuclear-spin signal in a set of model (19)F- and (1)H-rich fluids. Our approach integrates optical detection with high-field, pulsed NMR so as to record the time-resolved evolution of nuclear-spins after rf excitation. Comparison of chemical-shift-resolved resonances allows us to set order-of-magnitude constrains on the relative amplitudes of hyperfine coupling constants for different bonding geometries. When evaluated against coil induction, the present detection modality suffers from poorer sensitivity, but improvement could be attained via multipass schemes. Because illumination is off-resonant i.e., the medium is optically transparent, this methodology could find extensions in a broad class of fluids and soft condensed matter systems. 相似文献
997.
Valeria Nardelli Daniela dell’Oro Carmen Palermo Diego Centonze 《Journal of chromatography. A》2010,1217(30):4996-5003
A multi-residue method for the determination of organochlorine pesticides in fish feed samples was developed and optimized. The method is based on a cleanup step of the extracted fat, carried out by liquid–liquid extraction on diatomaceous earth cartridge with n-hexane/acetonitrile (80/20, v/v) followed by solid phase extraction (SPE) with silica gel–SCX cartridge, before the identification and quantification of the residues by gas chromatography–triple quadrupole tandem spectrometry (GC–MS/MS). Performance characteristics, such as accuracy, precision, linear range, limits of detection (LOD) and quantification (LOQ), for each pesticide were determined. Instrumental LODs ranged from 0.01 to 0.11 μg L−1, LOQs were in the range of 0.02–0.35 μg L−1, and calibration curves were linear (r2 > 0.999) in the whole range of explored concentrations (5–100 μg L−1). Repeatability values were in the range of 3–15%, evaluated from the relative standard deviation of six samples spiked at 100 μg kg−1 of fat, and in compliance with that derived by the Horwitz's equation. No matrix effects or interfering substances were observed in fish feed analyses. The proposed method allowed high recoveries (92–116%) of spiked extracted fat samples at 100 μg kg−1, and very low LODs (between 0.02 and 0.63 μg kg−1) and LOQs (between 0.05 and 2.09 μg kg−1) determined in fish feed samples. 相似文献
998.
Earlier we reported on the synthesis of α,4-dicarboxy-2-nitrobenyzl caged compounds (Schaper, K. et al. [2002] Eur. J. Org. Chem., 1037–1046). These compounds have the advantage of an increased hydrophilicity compared with the well-established α-carboxy-2-nitrobenzyl caged compounds; however, the release of the active compound becomes slower due to the introduction of the additional carboxy group. Based upon theoretical calculations we predicted that the release would become faster when the additional carboxy group is moved to the 5-position. Here we describe the synthesis and the photochemical and biological characterization of an α,5-dicarboxy-2-nitrobenyzl caged compound. The high hydrophilicity of the new caging group is maintained due to the fact that the additional carboxy moiety is preserved, while the release of the active species from the new derivative is even faster than for the reference, an α-CNB caged compound. 相似文献
999.
Coppola C Paciello A Mangiapia G Licen S Boccalon M De Napoli L Paduano L Tecilla P Montesarchio D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(46):13757-13772
A novel fluorescently labelled synthetic ionophore, based on a cyclic phosphate-linked disaccharide (CyPLOS) backbone and decorated with four tetraethylene glycol tails carrying dansyl units, has been synthesised in 12 steps in 26% overall yield. The key intermediate in the synthetic strategy is a novel glucoside building block, serving through its 2- and 3-hydroxy groups as the anchor point for flexible tetraethylene glycol tentacles with reactive azido moieties at their ends. To test the versatility of this glucoside scaffold, it was preliminarily functionalised with a set of diverse probes--as fluorescent, redox-active or hydrophobic tags--either by reduction of the azides followed by condensation with activated carboxylic acid derivatives, or by a direct coupling with a terminal alkyne in a Cu(I)-promoted 1,3-dipolar cycloaddition. Tagging of the monomeric building block with dansyl residues allowed us to prepare a fluorescent, amphiphilic macrocycle, which was investigated for its propensity to self-aggregate in CDCl(3)--studied by means of concentration-dependent (31)P NMR spectroscopy experiments--and in aqueous solution, in which combined dynamic light scattering (DLS) and small-angle neutron scattering (SANS) measurements provided a detailed physico-chemical analysis of the self-assembled systems, mainly organised in the form of large vesicles. Its ion-transport properties through phospholipid bilayers, determined by HPTS fluorescence assays, showed this compound to be more active than the previously synthesised CyPLOS congeners. Solvent-dependent fluorescence changes for the labelled ionophore in liposome suspension established that the dansyl moieties are dispersed in environments with polarity intermediate between those of CH(2)Cl(2) and propan-2-ol, suggesting that the CyPLOS tentacles infiltrate the mid-polar region of the membranes. 相似文献
1000.
Szychowski J Mahdavi A Hodas JJ Bagert JD Ngo JT Landgraf P Dieterich DC Schuman EM Tirrell DA 《Journal of the American Chemical Society》2010,132(51):18351-18360
The azide-alkyne cycloaddition provides a powerful tool for bio-orthogonal labeling of proteins, nucleic acids, glycans, and lipids. In some labeling experiments, e.g., in proteomic studies involving affinity purification and mass spectrometry, it is convenient to use cleavable probes that allow release of labeled biomolecules under mild conditions. Five cleavable biotin probes are described for use in labeling of proteins and other biomolecules via azide-alkyne cycloaddition. Subsequent to conjugation with metabolically labeled protein, these probes are subject to cleavage with either 50 mM Na(2)S(2)O(4), 2% HOCH(2)CH(2)SH, 10% HCO(2)H, 95% CF(3)CO(2)H, or irradiation at 365 nm. Most strikingly, a probe constructed around a dialkoxydiphenylsilane (DADPS) linker was found to be cleaved efficiently when treated with 10% HCO(2)H for 0.5 h. A model green fluorescent protein was used to demonstrate that the DADPS probe undergoes highly selective conjugation and leaves a small (143 Da) mass tag on the labeled protein after cleavage. These features make the DADPS probe especially attractive for use in biomolecular labeling and proteomic studies. 相似文献