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71.
We study the slow dynamics of hydration water upon cooling in two different biological aqueous solutions, one containing a molecule of lysozyme and another with trehalose molecules. In particular we test if the glassy behaviour of these solutions fulfils the predictions of the popular Mode Coupling Theory of glassy dynamics. In particular we test the Time Temperature Superposition Principle and the matching of the exponents of the theory. Our results confirm that this theory is able to describe the dynamical behaviour of supercooled water also in non ideal cases as the ones under investigation in the region of mild supercooling. 相似文献
72.
Fernando Martins dos Santos Jr. Gunar Vingre da Silva Mota Lucas Haidar Martorano Ana Carolina Ferreira de Albuquerque Claudinei Alves da Silva Adalberto Manoel da Silva Antônio Maia de Jesus Chaves Neto Alessandra Leda Valverde Evani Ferreira Cardoso Fabio Luiz Paranhos Costa 《Magnetic resonance in chemistry : MRC》2022,60(6):533-540
The combination of computational methods and experimental data from Nuclear Magnetic Resonance (NMR) is a considerably valuable tool in the elucidation of new natural product structures and, also, in the structural revision of previously reported compounds. Until recently, only classical statistical parameters were used, for example, linear correlation coefficient (R2), mean absolute error (MAE), or root mean square deviation (RMSD), as a way to statistically “validate” the structure pointed out by experimental NMR spectra. Regarding the resolution of the relative configuration of organic molecules, novel tools were available in the last few years to assist in the NMR elucidation process. The most relevant are DP4+, which is based on a Bayesian probability, and ANN-PRA, which is based on artificial neural networks. The combined application of these tools has become the most accurate and important alternative to solve structural and stereochemical problems in natural product chemistry. Therefore, herein, in this case study, we intended to promote these novel tools, exploring the strengths and limitations of each approach in resolving the relative configuration of the sesquiterpene alpha-bisabol. We also highlighted the advantages of the complementary use of H- and C-DP4+ to obtain optimal results in the differentiation of the stereoisomers, validating the proposal with ANN-PRA method. 相似文献
73.
Martina Costa Reis Yongqi Wang Adalberto Bono Maurizio Sacchi Bassi 《Continuum Mechanics and Thermodynamics》2014,26(6):753-769
Based on the Müller–Liu entropy principle and the axioms of constitutive theory, a continuum model for reacting ionic mixtures is presented. The influence of microscopic structure on the mixture dynamics is taken into account through the thermodynamics of polar materials. Moreover, mechanical balance laws for classical mixtures under influence of electromagnetic fields and quasi-electrostatic Maxwell’s equations are briefly shown. With an appropriate constitutive model for a diluted and isotropic mixture of non-volatile solutes and by considering the same temperature field for all constituents, constraints on constitutive quantities are imposed, and the conditions for the thermodynamic equilibrium are established from the entropy principle. Furthermore, the nonlinear nature of chemical reactions as well as the reciprocal nature of some irreversible processes is highlighted. Unlike the classical approach for electrolyte solutions, the current constitutive model incorporates thermoelectric and electro-kinetic phenomena into the phenomenological equations, providing a more comprehensive approach of electrolyte solutions dynamics. 相似文献
74.
Thenner S. Rodrigues Anderson G.M. da Silva Lucas C. de Oliveira Adalberto M. da Silva Róbson R. Teixeira Pedro H.C. Camargo 《Tetrahedron letters》2017,58(6):590-595
We report herein the high yield synthesis of Cu2O spheres displaying well-defined shapes and monodisperse sizes that could be employed as the source of highly catalytic active Cu(I) species towards click reactions between several of alkynes and azides to produce a variety of 1,2,3-triazoles under ligand-free and ambient conditions (in an open reactor). The utilization of Cu2O spheres enabled superior performance as compared to a conventional protocol in which CuSO4 is employed in combination with sodium ascorbate as the catalyst system. In addition, the compounds were obtained in synthetically useful yields, and seven of them have not been previously reported. We believe the results reported herein shed new insights into the optimization of activity and versatility of click reactions towards the synthesis of target molecules in environmentally friendly conditions. 相似文献
75.
Maria Suely Siqueira Ferraz Lêda Rita DAntonino Faroni Fernanda Fernandes Heleno Adalberto Hiplito de Sousa Lucas Henrique Figueiredo Prates Alessandra Aparecida Zinato Rodrigues 《Molecules (Basel, Switzerland)》2021,26(22)
Bioinsecticides are regarded as important alternatives for controlling agricultural pests. However, few studies have determined the persistence of these compounds in stored grains. This study aimed at optimizing and validating a fast and effective method for extraction and quantification of residues of safrole (the main component of Piper hispidinervum essential oil) in cowpea beans. It also sought to assess the persistence of this substance in the grains treated by contact and fumigation. The proposed method used headspace solid-phase microextraction (HS-SPME) and gas chromatography with a flame ionization detector (GC/FID). Factors such as temperature, extraction time and type of fiber were assessed to maximize the performance of the extraction technique. The performance of the method was appraised via the parameters selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy. The LOD and LOQ of safrole were 0.0057 and 0.019 μg kg−1, respectively and the determination coefficient (R2) was >0.99. The relative recovery ranged from 99.26 to 104.85, with a coefficient of variation <15%. The validated method was applied to assess the persistence of safrole residue in grains, where concentrations ranged from 1.095 to 0.052 µg kg−1 (contact) and from 2.16 to 0.12 µg kg −1 (fumigation). The levels measured up from the fifth day represented less than 1% of the initial concentration, proving that safrole have low persistence in cowpea beans, thus being safe for bioinsecticide use. Thus, this work is relevant not only for the extraction method developed, but also for the possible use of a natural insecticide in pest management in stored grains. 相似文献
76.
Hasmann Francislene-Andréia Pessoa Adalberto Roberto Inês-Conceição 《Applied biochemistry and biotechnology》2001,91(1-9):719-728
β-Xylosidase recovery by micelles using cetyl trimethyl ammonium bromide (CTAB) cationic surfactant was verified under different
experimental conditions. A 25−1 fractional factorial design with center points was employed to verify the influence of the following factors on enzyme extraction:
pH (x
1), CTAB concentration (x
2), electrical conductivity (x
3), hexanol concentration (x
4), and butanol concentration (x
5). Statistical analysis of the results shows that of the fivevariables studied only hexanol and electrical conductivity did
not have significant effects on the recovery of β-xylosidase. The other factors had significant effects in increasing order:
(x
1)>(x
2)>(x
5). The model predicts a recovery value of about 45%, which is similar to that obtained experimentally (43.5%). 相似文献
77.
Adalberto Orsatti 《Annali di Matematica Pura ed Applicata》1977,113(1):211-235
Summary Starting from a topological module E over a commutative discrete ring A, the category C(E) of E-compact modules is defined
as the class of all A-modules topologically isomorphic to closed submodules of direct product of copies of E. Under suitable
assumptions it is shown that C(E) is dual of the category of abstract A-modules M for whichHom
A(M, E) separates points of M. The duality theory so obtained contains as particular cases Pontryagin's duality between discrete
and compact abelian groups and Macdonald's duality between lineary discrete and linearly compact modules over a complete local
ring. There are also some applications to the theory of linearly compact modules over noetherian rings.
Entrata in Redazione il 10 aprile 1976.
Lavoro eseguito nell'ambito dell'attività dei gruppi di ricerca matematici del C.N.R. 相似文献
Entrata in Redazione il 10 aprile 1976.
Lavoro eseguito nell'ambito dell'attività dei gruppi di ricerca matematici del C.N.R. 相似文献
78.
Adalberto P. Bergamasco 《Transactions of the American Mathematical Society》1999,351(10):4113-4126
We present a characterization of the operators
which are globally analytic hypoelliptic on the torus. We give information about the global analytic hypoellipticity of certain overdetermined systems and of sums of squares.
79.
Yan Xu Michele Vitolo Cristina Northfleet de Albuquerque Adalberto Pessoa Jr. 《Applied biochemistry and biotechnology》2003,108(1-3):853-865
To improve the selectivity of glucose-6-phosphate dehydrogenase (G6PDH) extraction by an aqueous two-phase system, a simple
and inexpensive affinity aqueous two-phase system using unbound reactive triazine dyes as ligands was introduced. In a polyethylene
glycol (PEG)/hydroxypropyl starch (PES) system, the unbound free triazine dyes, Cibacron Blue F3GA and Procion Red HE3B, partitioned
unevenly in the top PEG-rich phase and thus showed an affinity effect on G6PDH, but no influence on hexokinase. The various
parameters investigated were pH of the system, buffers, molecular weight of PEG, and ligand type and concentration. A two-step
affinity extraction process was established for the purification of G6PDH from baker’s yeast. The total yield of G6PDH was
66.9% and purification factor was 2.35. 相似文献
80.
Luiz G. Ferreira Adalberto Fazzio Huberto Closs Luiz M. Brescansin 《International journal of quantum chemistry》1979,16(5):1021-1031
We consider the effects of a non-muffin-tin charge density in the multiple-scattering method. The study is carried out by means of a parametrized electronic density, which is used in a variational expression for the energy of the molecular system. We show that, at least in two situations, the parametrized density reproduces the true density very well. In a numerical study of the electronic configuration of the CH4 molecule, we show that the non-muffin-tin density may shift the one-electron energies by as much as 1 eV and the total energy by as much as 1 Ry. 相似文献