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1.
G. Duplâtre A. Haessler A. Marques Netto 《Journal of Radioanalytical and Nuclear Chemistry》1984,82(2):219-228
Ion association has been studied by positron lifetime spectroscopy in aqueous solutions containing the Ni2+ and SO
4
2–
ions at 294 K with the double aim of assessing the reliability of the method for quantitative determination of complex formation constants and of probing the validity of various expressions to calculate single-ion activity coefficients at high ionic strength. The existence of two complexes, identified as NiSO4 and Ni2SO
4
2+
, is shown by the data analysis. Considering the formation constant of the former, KI=(196±10)M–1, determined in previous works leads to discarding several of the expressions commonly used for activity corrections. Two possible values are retained for KI, (193±20)M–1 and (179±20)M–1, while KII related to Ni2SO
4
2+
is better defined, as (2.57±0.14)M–1. 相似文献
2.
Garcia Ruano JL Alemparte C Martin Castro AM Adams H Rodriguez Ramos JH 《The Journal of organic chemistry》2000,65(23):7938-7943
The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles. 相似文献
3.
Amanda Rodrigues Pinto Costa Marcelly Muxfeldt Fernanda da Costa Santos Boechat Maria Cecília Bastos Vieira de Souza Jerson Lima Silva Marcela Cristina de Moraes Luciana Pereira Rangel Tuane Cristine Ramos Gonalves Vieira Pedro Netto Batalha 《Molecules (Basel, Switzerland)》2022,27(22)
Prion Diseases or Transmissible Spongiform Encephalopathies are neurodegenerative conditions associated with a long incubation period and progressive clinical evolution, leading to death. Their pathogenesis is characterized by conformational changes of the cellular prion protein—PrPC—in its infectious isoform—PrPSc—which can form polymeric aggregates that precipitate in brain tissues. Currently, there are no effective treatments for these diseases. The 2,5-diamino-1,4-benzoquinone structure is associated with an anti-prion profile and, considering the biodynamic properties associated with 4-quinolones, in this work, 6-amino-4-quinolones derivatives and their respective benzoquinone dimeric hybrids were synthesized and had their bioactive profile evaluated through their ability to prevent prion conversion. Two hybrids, namely, 2,5-dichloro-3,6-bis((3-carboxy-1-pentyl-4-quinolone-6-yl)amino)-1,4-benzoquinone (8e) and 2,5-dichloro-3,6-bis((1-benzyl-3-carboxy-4-quinolone-6-yl)amino)-1,4-benzoquinone (8f), stood out for their prion conversion inhibition ability, affecting the fibrillation process in both the kinetics—with a shortening of the lag phase—and thermodynamics and their ability to inhibit the formation of protein aggregates without significant cytotoxicity at ten micromolar. 相似文献
4.
Rolando Ramirez Carlos Eduardo Schnorr Jordana Georgin Matias Schadeck Netto Dison S. P. Franco Elvis Carissimi Delmira Wolff Luis F. O. Silva Guilherme Luiz Dotto 《Molecules (Basel, Switzerland)》2022,27(22)
Brazil’s production and consumption of açai pulp (Euterpe oleracea) occur on a large scale. Most of the fruit is formed by the pit, which generates countless tons of residual biomass. A new purpose for this biomass, making its consumption highly sustainable, was presented in this study, where activated carbon (AC) was produced with zinc chloride for later use as an adsorbent. AC carbon formed by carbon and with a yield of 28 % was satisfactorily used as an adsorbent in removing the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Removal efficiency was due to the highly porous surface (Vp = 0.467 cm3 g−1; Dp = 1.126 nm) and good surface área (SBET = 920.56 m2 g−1). The equilibrium data fit the Sips heterogeneous and homogeneous surface model better. It was observed that the increase in temperature favored adsorption, reaching a maximum experimental capacity of 218 mg g−1 at 328 K. The thermodynamic behavior indicated a spontaneous, favorable, and endothermic behavior. The magnitude of the enthalpy of adsorption was in agreement with the physical adsorption. Regardless of the herbicide concentration, the adsorbent displayed fast kinetics, reaching equilibrium within 120 min. The linear driving force (LDF) model provided a strong statistical match to the kinetic curves. AC with zinc chloride (ZnCl2), created from leftover açai biomass, is a potential alternative as an adsorbent for treating effluents containing 2,4-D. 相似文献
5.
Thales R. de Moura Sahra L. Cavalcanti Paulo R. D. V. de Godoy Elza T. Sakamoto-Hojo Fillipe V. Rocha Eduardo T. de Almeida Victor M. Deflon Antonio E. Mauro Adelino V. G. Netto 《Transition Metal Chemistry》2017,42(6):565-574
Complexes of the type cis-[PdX2(imzt)(PPh3)] {imzt = imidazolidine-2-thione; PPh3 = triphenylphosphine; X = Cl (1), Br (2), I (3), SCN (4)} have been synthesized and characterized by elemental analyses, molar conductance, IR and 1H NMR spectroscopies. The complex 1·MeOH was obtained from the reaction of [PdCl2(CH3CN)2], imidazolidine-2-thione and triphenylphosphine in CHCl3/CH3OH. Complexes 2·MeOH, 3 and 4 were prepared by metathesis of the chlorido ligands in 1 with bromide, iodide and thiocyanate, respectively. Elemental analyses showed good agreement with the expected mononuclear compositions, while the molar conductivities of the complexes in DMF were consistent with their nonelectrolytic nature. NMR spectra confirmed coordination of the imidazolidine-2-thione and triphenylphosphine ligands. Single-crystal X-ray diffraction determination of 1·CH3OH showed that the coordination geometry around PdII is nearly square planar, with the chlorido ligands in a cis configuration. All four complexes have been tested in vitro by XTT assay for their cytotoxicity against human glioblastoma cell line (U87MG). The binding of 1 with guanosine was studied by 1H NMR spectroscopy, revealing that the coordination takes place via N7. 相似文献
6.
This paper reports the multivariate optimization of a liquid–liquid extraction procedure for the determination of 15 EPA-polycyclic aromatic hydrocarbons (PAHs) by high-performance liquid chromatography with fluorescence detection. A Doehlert design was used to find optimum conditions for the procedure through Response Surface Methodology. Three variables (total volume of hexane, number of extraction steps and duration of such steps) were elected as factors in the optimization study. A principal component analysis (PCA) was run with optimized data, resulting in four groups of PAHs, ordered according to their molecular weight. Final working conditions were established in order to achieve a more robust methodology in relation to all fifteen PAHs under study. Best results could be observed when 77 mL of hexane were divided in four consecutive extraction steps with 18 min each. These experimental conditions were applied in the analysis of a spiked river water sample, and the recoveries varied between 80.9 and 106%, with an average value of 97.1 ± 6.8%. The application of the methodology to river water showed that the method has a good average precision for the studied PAHs. 相似文献
7.
EI Rodriguez Martinez CI Barriga-Paulino MI Zapata CC Chinchilla AM López-Jiménez CM Gómez 《BMC neuroscience》2012,13(1):104-23
ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. 相似文献
8.
Stocker Mariele K. Sanson Murilo L. Bernardes Arthur A. Netto Antonio Marchi Brambilla Rodrigo 《Journal of Sol-Gel Science and Technology》2021,98(3):568-579
Journal of Sol-Gel Science and Technology - In this work, silica capsules containing bromothymol blue (BTB) were synthesized by a modified Stöber sol–gel method. These silica capsules... 相似文献
9.
KM Varier AM Vinodkumar NVSV Prasad PV Madhusudhana Rao DL Sastry Lagy T Baby MC Radhakrishna NG Puttaswamy JJ Das P Sugathan N Madhavan AK Sinha DO Kataria 《Pramana》1999,53(3):529-533
Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies.
Coupled channel calculations incorporating couplings to 2+ and 3− states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements
had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer
were carried out for 46,48Ti+61Ni systems. The present paper gives the results of these studies. 相似文献
10.
Sun R Colin E Ajitanand NN Alexander JM Barton MA DeYoung PA Drake KL Elmaani A Gelderloos CJ Gualtieri EE Guinet D Hannuschke S Jaasma JA Kowalski L Lacey RA Lauret J Norbeck E Pak R Peaslee GF Stern M Stone NT Sundbeck SD Vander Molen AM Westfall GD Yang LB Yee J 《Physical review letters》2000,84(1):43-46
For central collisions of (17-115)A MeV 40Ar+Cu, Ag, Au, an overall balance is determined for the average mass, energy, and longitudinal momentum. Light charged particles and fragments are separated into forward-focused and isotropic components in the frame of the heaviest fragment. Energy removal by the isotropic component reaches 1-2 GeV. For such high deposition energies, statistical multifragmentation models predict much more extensive nuclear disassembly than is observed. 相似文献