全文获取类型
收费全文 | 176篇 |
免费 | 2篇 |
专业分类
化学 | 109篇 |
力学 | 2篇 |
数学 | 21篇 |
物理学 | 46篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 11篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 13篇 |
2012年 | 16篇 |
2011年 | 13篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有178条查询结果,搜索用时 46 毫秒
1.
Sun Guo-Hua Dong Qian Bezerra V. B. Dong Shi-Hai 《Journal of mathematical chemistry》2022,60(4):605-612
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,... 相似文献
2.
3.
A. P. M. Alves A. S. Araujo F. A. Bezerra K. S. Sousa S. J. G. Lima M. G. Fonseca 《Journal of Thermal Analysis and Calorimetry》2014,117(1):19-26
Acid leaching of aluminosilicates is an interesting procedure for preparing high surface porous silica. Thermal behavior of vermiculite leached with a nitric acid solution at various concentrations was studied by thermogravimetry and differential scanning calorimetry. Activation energies of the dehydration process in selected temperature zones were determined by two different methods: Ozawa–Flynn–Wall and Friedman. The material obtained was characterized through Fourier transform infrared spectroscopy, X-ray diffraction, and nitrogen adsorption at 77 K to relate them to the estimated activation energies. 相似文献
4.
Denise Tofanello Gimenes Polyana Fernandes Pereira Rafael Rodrigues Cunha Rodrigo Amorim Bezerra da Silva Rodrigo Alejandro Abarza Munoz Eduardo Mathias Richter 《Electroanalysis》2012,24(9):1805-1810
In this study, we describe for the first time the application of an internal standard method to compensate for random errors associated with the injection procedure in batch injection analysis (BIA) systems with multiple pulse amperometric detection. A sequence of potential pulses was selected in such a way that the internal standard (IS) compound was detected individually at one potential pulse and both the IS and analyte, were detected at another potential pulse. The current ratio (IIS+analyte/IIS) was used in the construction of the calibration curve and then to compensate for random errors. The use of disposable syringes or manual pipettes in BIA systems increases the robustness of the method and dispenses with skilled operators. 相似文献
5.
This work provides a straightforward and rigorous solution to the problem of evaluating and expressing relative changes in combined uncertainty resulting from relative changes in the uncertainty components. The acquired information is essential to optimize the measurement method, indicating the most significant components to work with. This approach works for any discrete relative change in the uncertainties of the inputs, whether positive or negative, and was developed for the cases of independent and correlated quantities. Examples of both cases are treated. The results agree with that provided by direct calculation and are consistent with the ideas in EA 4/16. We propose the use of the expression “sensitivity of combined standard uncertainty to changes in uncertainty components” as a uniform quantitative reference to the individual importance of the components that form the combined uncertainty. We also discuss the reason to avoid the use of the expression “contribution of an uncertainty component to the combined uncertainty.” 相似文献
6.
Maxime Balestrat Abhijeet Lale Andr Vinícius Andrade Bezerra Vanessa Proust Eranezhuth Wasan Awin Ricardo Antonio Francisco Machado Pierre Carles Ravi Kumar Christel Gervais Samuel Bernard 《Molecules (Basel, Switzerland)》2020,25(22)
The pyrolysis (1000 °C) of a liquid poly(vinylmethyl-co-methyl)silazane modified by tetrakis(dimethylamido)titanium in flowing ammonia, nitrogen and argon followed by the annealing (1000–1800 °C) of as-pyrolyzed ceramic powders have been investigated in detail. We first provide a comprehensive mechanistic study of the polymer-to-ceramic conversion based on TG experiments coupled with in-situ mass spectrometry and ex-situ solid-state NMR and FTIR spectroscopies of both the chemically modified polymer and the pyrolysis intermediates. The pyrolysis leads to X-ray amorphous materials with chemical bonding and ceramic yields controlled by the nature of the atmosphere. Then, the structural evolution of the amorphous network of ammonia-, nitrogen- and argon-treated ceramics has been studied above 1000 °C under nitrogen and argon by X-ray diffraction and electron microscopy. HRTEM images coupled with XRD confirm the formation of nanocomposites after annealing at 1400 °C. Their unique nanostructural feature appears to be the result of both the molecular origin of the materials and the nature of the atmosphere used during pyrolysis. Samples are composed of an amorphous Si-based ceramic matrix in which TiNxCy nanocrystals (x + y = 1) are homogeneously formed “in situ” in the matrix during the process and evolve toward fully crystallized compounds as TiN/Si3N4, TiNxCy (x + y = 1)/SiC and TiC/SiC nanocomposites after annealing to 1800 °C as a function of the atmosphere. 相似文献
7.
I.P. Coelho M.S. VasconcelosC.G. Bezerra 《Journal of magnetism and magnetic materials》2011,323(23):3162-3167
In this paper we investigated the influence of mirror symmetry on the transmission spectra of quasiperiodic magnonic multilayers arranged according to Fibonacci, Thue-Morse and double period quasiperiodic sequences. We consider that the multilayers composed of two simple cubic Heisenberg ferromagnets with bulk exchange constants JA and JB and spin quantum numbers SA and SB, respectively. The multilayer structure is surrounded by two semi-infinite slabs of a third Heisenberg ferromagnetic material with exchange constant JC and spin quantum number SC. For simplicity, the lattice constant has the same value a in each material, corresponding to epitaxial growth at the interfaces. The transfer matrix treatment was used for the exchange-dominated regime, taking into account the random phase approximation (RPA). Our numerical results illustrate the effects of mirror symmetry on (i) transmission spectra and (ii) transmission fingerprints. 相似文献
8.
Di?go P. Bezerra Ronan S. Oliveira Rodrigo S. Vieira Célio L. Cavalcante Diana C. S. Azevedo 《Adsorption》2011,17(1):235-246
Adsorption may be a potentially attractive alternative to capturing CO2 from stationary sources in the context of Carbon Capture and Sequestration (CCS) technologies. Activated carbon and zeolites
are state-of-art adsorbents which may be used for CO2 adsorption, however physisorption alone tends to be insignificant at high temperatures. In the present work, commercial adsorbents
have been impregnated with monoethanolamine (MEA) and triethanolamine (TEA) in order to investigate the effect of the modified
surface chemistry on CO2 adsorption, especially above room temperature. Adsorption isotherms for CO2, N2 and CH4 were measured in a gravimetrically system in the pressure range of UHV to 10 bar, at 298 and 348 K for activated carbon and
zeolite 13X supports. The adsorbed concentration of CO2 was significantly higher than those of CH4 and N2 for both adsorbents in the whole pressure range studied, zeolite 13X showing a remarkable affinity for CO2 at very low pressures. However, at 348 K, the adsorbed concentration of CO2 decreases significantly. The supports impregnated with concentrated amine solutions and dried in air suffered a detrimental
effect on the textural properties, although CO2 uptake became much less susceptible to temperature increase. Impregnations carried out with dilute solution followed by drying
in inert atmosphere yielded materials with very similar textural characteristics as compared to the parent support. CO2 isotherms in such materials showed a significant change with similar capacities at 348 K as compared to the original support
at 298 K in the case of activated carbons. The impregnated zeolite showed a decrease in adsorbed phase concentration in low
pressures for a given temperature, but the adsorbed amount also seemed to be less affected by temperature. These results are
promising and indicate that CO2 adsorption may be enhanced despite high process temperatures (e.g. 348 K), if convenient impregnation and drying methods
are applied. 相似文献
9.
Exposure risk assessment of uranium intake of the milk products from the region of Pernambuco,Brazil
dos Santos Amaral Romilton dos Santos Júnior José Araújo da Silva Aquino Fabiana de Albuquerque Amaral Bruno Fernández Zahily Herrero Bezerra Mariana Brayner Cavalcanti Freire da Silva Arykerne Nascimento Casado dos Santos Djalma Cordeiro do Nascimento Santos Josineide Marques da Silva Alberto Antônio de Barros Correia Filipe Lopes 《Journal of Radioanalytical and Nuclear Chemistry》2019,319(3):927-935
Journal of Radioanalytical and Nuclear Chemistry - Haloperidol (HP) is a dopamine blocking agent. HP was radiolabeled with 125I using direct electrophilic substitution. Different HP formulations... 相似文献
10.
<Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">R</Emphasis>) global monopole revisited
Thiago R. P. Caramês Júlio C. Fabris E. R. Bezerra de Mello H. Belich 《The European Physical Journal C - Particles and Fields》2017,77(7):496
In this paper the f(R) global monopole is reexamined. We provide an exact solution for the modified field equations in the presence of a global monopole for regions outside its core, generalizing previous results. Additionally, we discuss some particular cases obtained from this solution. We consider a setup consisting of a possible Schwarzschild black hole that absorbs the topological defect, giving rise to a static black hole endowed with a monopole’s charge. Besides, we demonstrate how the asymptotic behavior of the Higgs field far from the monopole’s core is shaped by a class of spacetime metrics which includes the ones analyzed here. In order to assess the gravitational properties of this system, we analyze the geodesic motion of both massive and massless test particles moving in the vicinity of such configuration. For the material particles we set the requirements they have to obey in order to experience stable orbits. On the other hand, for the photons we investigate how their trajectories are affected by the gravitational field of this black hole. 相似文献