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121.
Nastri F Lista L Ringhieri P Vitale R Faiella M Andreozzi C Travascio P Maglio O Lombardi A Pavone V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4444-4453
Mimicking enzymes with alternative molecules represents an important objective in synthetic biology, aimed to obtain new chemical entities for specific applications. This objective is hampered by the large size and complexity of enzymes. The manipulation of their structures often leads to a reduction of enzyme activity. Herein, we describe the spectroscopic and functional characterization of Fe(III)-mimochrome VI, a 3.5 kDa synthetic heme-protein model, which displays a peroxidase-like catalytic activity. By the use of hydrogen peroxide, Fe(III)-mimochrome VI efficiently catalyzes the oxidation of several substrates, with a typical Michaelis-Menten mechanism and with several multiple turnovers. The catalytic efficiency of Fe(III)-mimochrome VI in the oxidation of 2,2'-azino-di(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) and guaiacol (k(cat)/K(m)=4417 and 870 mM(-1) s(-1), respectively) is comparable to that of native horseradish peroxidase (HRP, k(cat)/K(m)=5125 and 500 mM(-1) s(-1), respectively). Fe(III)-mimochrome VI also converts phenol to 4- and 2-nitrophenol in the presence of NO(2) (-) and H(2) O(2) in high yields. These results demonstrate that small synthetic peptides can impart high enzyme activities to metal cofactors, and anticipate the possibility of constructing new biocatalysts tailored to specific functions. 相似文献
122.
The reaction between differently N-substituted benzaldimines and (2R)-Schöllkopf's bislactim ether was studied: the azaenolate addition to imines followed by hydrolysis of the resulting adducts gave syn-(2S,3R) and anti-(2S,3S)-methyl 2,3-diamino-3-phenylpropanoate derivatives in good yields. The configurations of the newly formed stereocenters of α,β-diamino acids were assigned on the basis of the 1H NMR analysis and by comparison with known products. The diastereoisomeric ratios were explained taking into account the effect of the substituent present on the imine nitrogen on the transition state stability. This method represents a new approach for stereoselective synthesis of α,β-diamino acids. 相似文献
123.
Lapolla A Fedele D Reitano R Aricò NC Seraglia R Traldi P Marotta E Tonani R 《Journal of the American Society for Mass Spectrometry》2004,15(4):496-509
An extensive study was carried out on HSA and non-enzymatically glycated HSA by enzymatic digestion with trypsin and endoproteinase Lys-C, with the aim of identifying specific glycated peptides deriving from enzymatic digestion of glycated HSA. They may be considered, in pectore, as advanced glycation end products/peptides. These compounds, important at a systemic level in diabetic and nephropathic subjects, are produced by enzymatic digestion of in vivo glycated proteins: They are related to the pathological state of patients and have been invoked as responsible for tissue modifications. The digested mixtures obtained by the two enzymes were analyzed by MALDI/MS and LC/ESI/MSn, and clear cut differences were found. First of all, the digestion products of glycated HSA are generally less abundant than those observed in the case of unglycated HSA, accounting for the lower proclivity of the former to enzymatic digestion. MS/MS experiments on doubly charged ions, comparisons with a protein database, and molecular modeling to identify the lysine NH2 groups most exposed to glycation, identified some glycated peptides in digestion mixtures obtained from both types of enzymatic digestion. Residues 233K, 276K, 378K, 545K, and 525K seem to be privileged glycation sites, in agreement with the fractional solvent accessible surface values calculated by molecular modeling. 相似文献
124.
Luca Rivoira Michele Castiglioni Massimo Del Bubba Maria Concetta Bruzzoniti 《International journal of environmental analytical chemistry》2013,93(12):1149-1159
ABSTRACTIn this work, we innovatively applied the 3D amperometry detection, coupled to liquid chromatography, for the determination of a mixture of chromatographically unresolved compounds (two herbicides—monuron and bentazon, one drug—propranolol and the main metabolite of an antiepileptic drug—5-(4?-hydroxyphenyl)-5-phenylhydantoin). Exploiting the post-chromatographic current integration, a scanning waveform was successfully applied to explore a wide range of potentials (0.0–1.3 V) to find the peculiar oxidative potential value for each compound. This approach allowed us to obtain 3D chromatograms (elution time vs potential vs current) in which coeluted species could be clearly distinguished.Quantitation was easily obtained by extraction of 2D chromatograms (elution time vs integrated current), from the 3D ones, at the optimised waveform time ranges (800–1,000 msec and 1,500–1,700 msec, corresponding to 0.6–0.8 V and 1.0–1.2, respectively). Validation of the proposed 3D amperometry method was performed in terms of linearity, limits of detection and quantitation and repeatability. Matrix effect was studied by statistical treatment on a wastewater effluent. By coupling an on-line solid phase extraction step prior to separation and detection by 3D amperometry, detection limits were significantly reduced (57 ng/L for bentazon, with recovery yields of 82.9 ± 10.9%). It is worth mentioning that this value fully satisfies the requirements of the 98/83/CE directive for the determination of bentazon in groundwater. 相似文献
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127.
Serena Esposito Maria Turco Gianguido Ramis Giovanni Bagnasco Pasquale Pernice Concetta Pagliuca Maria Bevilacqua Antonio Aronne 《Journal of solid state chemistry》2007,180(12):3341-3350
Cobalt–silicon mixed oxide materials (Co/Si=0.111, 0.250 and 0.428) were synthesised starting from Co(NO3)2·6H2O and Si(OC2H5)4 using a modified sol–gel method. Structural, textural and surface chemical properties were investigated by thermogravimetric/differential thermal analyses (TG/DTA), XRD, UV–vis, FT-IR spectroscopy and N2 adsorption at −196 °C. The nature of cobalt species and their interactions with the siloxane matrix were strongly depending on both the cobalt loading and the heat treatment. All dried gels were amorphous and contained Co2+ ions forming both tetrahedral and octahedral complexes with the siloxane matrix. After treatment at 400 °C, the sample with lowest Co content appeared amorphous and contained only Co2+ tetrahedral complexes, while at higher cobalt loading Co3O4 was present as the only crystalline phase, besides Co2+ ions strongly interacting with siloxane matrix. At 850 °C, in all samples crystalline Co2SiO4 was formed and was the only crystallising phase for the nanocomposite with the lowest cobalt content. All materials retained high surface areas also after treatments at 600 °C and exhibited surface Lewis acidity, due to cationic sites. The presence of cobalt affected the textural properties of the siloxane matrix decreasing microporosity and increasing mesoporosity. 相似文献
128.
Concetta Pacifico Mariarita Laforgia Francesco P. Intini Giacomo Padovano Giovanni Natile 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(7):m306-m310
Two new polymorphs of the title compound, K[PtCl3(C6H15O4PS)], already known in the monoclinic form, were obtained by crystallization from acetone–n‐pentane solutions of different composition. Both polymorphs are orthorhombic in the space group P212121, with Z′ = 1 (solvent ratio 1:4) and 3 (solvent ratio 1:9). In both polymorphs, electrostatic interactions link K+ cations and [PtCl3(SMP)]− anions [SMP is diethyl (methylsulfinylmethyl)phosphonate] in infinite chains, while adjacent chains are held together by weak C—H⋯Cl and C—H⋯O hydrogen‐bond interactions. 相似文献
129.
Francesco Cal�� Giuseppa Ruggeri Mirella Vinci Concetta Meli Carla Carducci Vincenzo Leuzzi Simone Pozzessere Pietro Schinocca Alda Ragalmuto Valeria Chiavetta Salvatore Miccich�� Valentino Romano 《Experimental & molecular medicine》2010,42(2):81-86
A consistent finding of many studies describing the spectrum of mutant phenylalanine hydroxylase (PAH) alleles underlying hyperphenylalaninemia is the impossibility of achieving a 100% mutation ascertainment rate using conventional gene-scanning methods. These methods include denaturing gradient gel electrophoresis (DGGE), denaturing high performance liquid chromatography (DHPLC), and direct sequencing. In recent years, it has been shown that a significant proportion of undetermined alleles consist of large deletions overlapping one or more exons. These deletions have been difficult to detect in compound heterozygotes using gene-scanning methods due to a masking effect of the non-deleted allele. To date, no systematic search has been carried out for such exon deletions in Italian patients with phenylketonuria or mild hyperphenylalaninemia. We used multiplex ligation- dependent probe amplification (MLPA), comparative multiplex dosage analysis (CMDA), and real-time PCR to search for both large deletions and duplications of the phenylalanine hydroxylase gene in Italian hyperphenylalaninemia patients. Four deletions removing different phenylalanine hydroxylase (PAH) gene exons were identified in 12 patients. Two of these deletions involving exons 4-5-6-7-8 (systematic name c.353-?_912 + ?del) and exon 6 (systematic name c.510-?_706 + ?del) have not been reported previously. In this study, we show that exon deletion of the PAH gene accounts for 1.7% of all mutant PAH alleles in Italian hyperphenylalaninemics. 相似文献
130.
Static dipole polarizabilities are calculated for the ground states of the alkali anions from Li- to Fr-. The polarizabilities include scalar relativistic effects at the second-order Douglas-Kroll level and were computed using the finite-field, coupled-cluster CCSD(T) method with large, carefully optimized basis sets. The relativistic polarizabilities increase with Z, reach a maximum at Cs-, and then decrease again unlike their nonrelativistic counterparts which increase monotonically with Z. 相似文献