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61.
Nelson F. Martínez Estela Lladosa MaCruz Burguet Juan B. Montn 《Fluid Phase Equilibria》2008,270(1-2):62-68
Consistent isobaric vapour–liquid equilibrium data have been measured for 2-butanone + ethanol, 2-butanone + 1-propanol, and 2-butanone + 2-propanol at 20 and 101.3 kPa. The binary systems 2-butanone + ethanol and 2-butanone + 2-propanol present a minimum boiling azeotrope at both pressures, and show that the azeotropic compositions is strongly dependent on pressure. The equilibrium data were correlated using the Wilson, NRTL, and UNIQUAC models for which the parameters are reported. 相似文献
62.
Estela Giménez Fernando Benavente José Barbosa Victoria Sanz-Nebot 《Analytical and bioanalytical chemistry》2010,398(1):357-365
2,5-Dihydroxybenzoic acid (DHB) has been demonstrated to be a more suitable matrix than 3,5-dimethoxy-4-hydroxycinnamic acid
(sinapinic acid, SA) to obtain reliable molecular mass values of intact glycoproteins because it prevents sugar fragmentation.
Lack of spot homogeneity during the crystallization step was prevented by drying the sample-matrix mixture under vacuum conditions.
Nevertheless, this sample-matrix preparation procedure requires a specific experimental setup and may be time-consuming. In
this work, we investigated the effectiveness of different ionic liquid matrices (ILMs) with SA and DHB on the ionization of
a set of intact glycoproteins with several degrees of glycosylation. The obtained results demonstrate that some of the tested
ILMs allow detection of the studied intact glycoproteins. Furthermore, the selected optimum conditions solve the reproducibility
issue of using the DHB as a solid matrix without the vacuum drying method and, surprisingly, avoid sugar fragmentation when
both SA and DHB were used as ILMs. 相似文献
63.
Cover Picture: Sulfoxide‐Directed Metal‐Free ortho‐Propargylation of Aromatics and Heteroaromatics (Chem. Eur. J. 20/2015) 下载免费PDF全文
64.
Montserrat Mancera-Arteu Estela GiménezJosé Barbosa Victòria Sanz-Nebot 《Analytica chimica acta》2016
In this study, a ZIC-HILIC-MS methodology for the analysis of N-glycan isomers was optimized to obtain greater detection sensitivity and thus identify more glycan structures in hAGP. In a second step, this method was combined with glycan reductive isotope labelling (GRIL) through [12C6]/[13C6]-aniline and exoglycosidase digestion to characterize the different glycan isomers. The GRIL method allows the peak areas resulting from two different labelled samples to be compared, since neither retention time shifts nor variations in the ionization of glycans between these samples are obtained. First, sialic acid linkage assignations were performed for most hAGP glycan isomers with α2-3 sialidase digestion. Bi-, tri- and tetraantennary glycan isomers with different terminal sialic acid linkages to galactose (α2-3 or α2-6) were assigned, and the potential of this technique for the structural characterization of isobaric isomers was therefore demonstrated. Furthermore, fucose linkage isomers of hAGP glycans were also characterized using this isotope-labelling approach in combination with α1-3,4 fucosidase and β1-4 galactosidase digestion. α1-3 antennary fucoses and α1-6 core fucosylation were detected in hAGP fucosylated glycans. These established methodologies can be extremely useful for patho-glycomic studies to characterize glycoproteins of biomedical interest and find novel glycan isomers that could be used as biomarkers in cancer research. 相似文献
65.
Carmona-Novillo E Bartolomei M Hernández MI Campos-Martínez J 《The Journal of chemical physics》2007,126(12):124315
Quasiclassical trajectory calculations have been carried out for H(2)(v(1)=high)+H(2)(v(2)=low) collisions within a three degrees of freedom model where five different geometries of the colliding complex were considered. Within this approach, probabilities for different competitive processes are studied: four center reaction, collision induced dissociation, reactive dissociation, and three-body complex formation. The purpose is to compare in detail with equivalent quantum-mechanical wave packet calculations [Bartolomei et al., J. Chem. Phys 122, 064305 (2005)], especially the behavior of the probabilities near reaction thresholds. Quasiclassical calculations compare quite well with the quantum-mechanical ones for collision induced dissociation as well as for the four center reaction, although quantum effects become very important near thresholds, particularly for lower v(1)'s and for the four center process. Less quantitative agreement is found for reactive dissociation and three-body complex formation. It is found that most quantum effects are due to differences between quantum and classical vibrational distributions of H(2)(v(1)=high). Zero point energy violation has been found in the classical reactive-dissociative probabilities. Extension of these findings to full-dimensional treatments is examined. 相似文献
66.
Miranda Paulo H. de S. Lourenço Estela M. G. Morais Alexander M. S. de Oliveira Pedro I. C. Silverio Priscilla S. de S. N. Jordão Alessandro K. Barbosa Euzébio G. 《Molecular diversity》2021,25(1):1-12
Molecular Diversity - Tuberculosis, caused by Mycobacterium tuberculosis (M. tuberculosis), is still responsible for a large number of fatal cases, especially in developing countries with alarming... 相似文献
67.
Pereira RM Andrades NE Paulino N Sawaya AC Eberlin MN Marcucci MC Favero GM Novak EM Bydlowski SP 《Molecules (Basel, Switzerland)》2007,12(7):1352-1366
The antioxidant activity of flavonoids is believed to increase when they are coordinated with transition metal ions. However, the literature on this subject is contradictory and the outcome seems to largely depend on the experimental conditions. In order to understand the contribution of the metal coordination and the type of interaction between a flavonoid and the metal ion, in this study a new metal complex of Cu (II) with naringin was synthesized and characterized by FT-IR, UV-VIS, mass spectrometry (ESI-MS/MS), elemental analysis and 1H-NMR. The results of these analyses indicate that the complex has a Cu (II) ion coordinated via positions 4 and 5 of the flavonoid. The antioxidant, anti-inflammatory and antimicrobial activities of this complex were studied and compared with the activity of free naringin. The Naringin-Cu (II) complex 1 showed higher antioxidant, anti-inflammatory and tumor cell cytotoxicity activities than free naringin without reducing cell viability. 相似文献
68.
Albert Barroso Estela GiménezFernando Benavente José BarbosaVictoria Sanz-Nebot 《Analytica chimica acta》2015
In this study, the classical semiempirical relationships between the electrophoretic mobility and the charge-to-mass ratio (me vs. q/Mα) were used to model the migration behaviour of peptides and glycopeptides originated from the digestion of recombinant human erythropoietin (rhEPO), a biologically and therapeutically relevant glycoprotein. The Stoke’s law (α = 1/3), the classical polymer model (α = 1/2) and the Offord’s surface law (α = 2/3) were evaluated to predict migration of peptides and glycopeptides, with and without sialic acids (SiA), in rhEPO digested with trypsin and trypsin–neuraminidase. The Stoke’s law resulted in better correlations for the set of peptides used to evaluate the models, while glycopeptides fitted better with the classical polymer model. Once predicted migration times with both models, it was easy to simulate their separation electropherogram. Results were later validated predicting migration and simulating separation of a different set of rhEPO glycopeptides and also human transferrin (Tf) peptides and glycopeptides. The excellent agreement between the experimental and the simulated electropherograms with rhEPO and Tf digests confirmed the potential applicability of this simple strategy to predict, in general, the peptide–glycopeptide electrophoretic map of any digested glycoprotein. 相似文献
69.
70.
J. M. Riego A. Costa P. Deyá J. V. Sinisterra J. M. Marinas 《Reaction Kinetics and Catalysis Letters》1982,19(1-2):61-63
The Beckmann rearrangement of cyclohexanone oxime p-toluenesulfonate has been studied using several catalysts. The reaction is catalyzed by weakly acidic sites and seems to occur by way of O-(p-toluenesulfonyl)--caprolactim.
- -, . - -(-)--.相似文献