全文获取类型
收费全文 | 97篇 |
免费 | 2篇 |
国内免费 | 5篇 |
专业分类
化学 | 69篇 |
晶体学 | 1篇 |
数学 | 15篇 |
物理学 | 19篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 3篇 |
2011年 | 10篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1996年 | 7篇 |
1994年 | 2篇 |
1982年 | 3篇 |
1975年 | 1篇 |
排序方式: 共有104条查询结果,搜索用时 15 毫秒
1.
CO conversion to hydrocarbons at various reaction temperatures and atmospheric pressure has been investigated on alumina-supported Fe, Ni and Fe–Ni catalysts. Maxima of activity and selectivity were obtained in hydrocarbon formation as a function of Fe content in the samples, which corresponds to a certain stoichiometry of metallic components. 相似文献
2.
Ana-Maria Popescu Virgil Constantin 《化学物理学报(中文版)》2014,(3):368-372
A systematic study was conducted on current efficiency (CE), corrosion and structural changes in SnO2-based inert anodes (made of 96wt%SnO2+2wt%Sb2O3+2wt%CuO) on a laboratory Hall-Heroult aluminium cell. The influence of operating parameters and electrolyte composition on the CE and corrosion process were evaluated. The CE was found to be more than 90% and catastrophic corrosion took place at low percent of Al2O3, high percent of LiF, low cryolite ratio and high current densities. From all the structural changes that took place in the SnO2-based inert anodes, we assumed that the most important contribution was due to the migration of CuO towards the outer limits of the constituent grains of SnO2 based ceramic. The complex process occurred during the formation of various phases and their sintering ability both directly depended on Cu/Sb molar ratio. 相似文献
3.
A low specific on-resistance (R S,on) silicon-on-insulator (SOI) trench MOSFET (metal-oxide-semiconductor-field-effect-transistor) with a reduced cell pitch is proposed.The lateral MOSFET features multiple trenches:two oxide trenches in the drift region and a trench gate extended to the buried oxide (BOX) (SOI MT MOSFET).Firstly,the oxide trenches increase the average electric field strength along the x direction due to lower permittivity of oxide compared with that of Si;secondly,the oxide trenches cause multiple-directional depletion,which improves the electric field distribution and enhances the reduced surface field (RESURF) effect in the SOI layer.Both of them result in a high breakdown voltage (BV).Thirdly,the oxide trenches cause the drift region to be folded in the vertical direction,leading to a shortened cell pitch and a reduced R S,on.Fourthly,the trench gate extended to the BOX further reduces R S,on,owing to the electron accumulation layer.The BV of the MT MOSFET increases from 309 V for a conventional SOI lateral double diffused metal-oxide semiconductor (LDMOS) to 632 V at the same half cell pitch of 21.5 μm,and R S,on decreases from 419 m · cm 2 to 36.6 m · cm 2.The proposed structure can also help to dramatically reduce the cell pitch at the same breakdown voltage. 相似文献
4.
Fabian Scheipl Ana-Maria Staicu Sonja Greven 《Journal of computational and graphical statistics》2013,22(2):477-501
We propose an extensive framework for additive regression models for correlated functional responses, allowing for multiple partially nested or crossed functional random effects with flexible correlation structures for, for example, spatial, temporal, or longitudinal functional data. Additionally, our framework includes linear and nonlinear effects of functional and scalar covariates that may vary smoothly over the index of the functional response. It accommodates densely or sparsely observed functional responses and predictors which may be observed with additional error and includes both spline-based and functional principal component-based terms. Estimation and inference in this framework is based on standard additive mixed models, allowing us to take advantage of established methods and robust, flexible algorithms. We provide easy-to-use open source software in the pffr() function for the R package refund. Simulations show that the proposed method recovers relevant effects reliably, handles small sample sizes well, and also scales to larger datasets. Applications with spatially and longitudinally observed functional data demonstrate the flexibility in modeling and interpretability of results of our approach. 相似文献
5.
Ana-Maria Udrea Andra Dinache Jean-Marie Pags Ruxandra Angela Pirvulescu 《Molecules (Basel, Switzerland)》2021,26(8)
Multidrug resistance of bacteria is a worrying concern in the therapeutic field and an alternative method to combat it is designing new efflux pump inhibitors (EPIs). This article presents a molecular study of two quinazoline derivatives, labelled BG1189 and BG1190, proposed as EPIs. In silico approach investigates the pharmacodynamic and pharmacokinetic profile of BG1189 and BG1190 quinazolines. Molecular docking and predicted ADMET features suggest that BG1189 and BG1190 may represent attractive candidates as antimicrobial drugs. UV-Vis absorption spectroscopy was employed to study the time stability of quinazoline solutions in water or in dimethyl sulfoxide (DMSO), in constant environmental conditions, and to determine the influence of usual storage temperature, normal room lighting and laser radiation (photostability) on samples stability. The effects of irradiation on BG1189 and BG1190 molecules were also assessed through Fourier-transform infrared (FTIR) spectroscopy. FTIR spectra showed that laser radiation breaks some chemical bonds affecting the substituents and the quinazoline radical of the compounds. 相似文献
6.
Ana-Maria Matache Tomáš Roubíček Christoph Schwab 《Advances in Computational Mathematics》2003,19(1-3):73-97
The general theory of approximation of (possibly generalized) Young measures is presented, and concrete cases are investigated. An adjoint-operator approach, combined with quasi-interpolation of test integrands, is systematically used. Applicability is demonstrated on an optimal control problem for an elliptic system, together with one-dimensional illustrative calculations of various options. 相似文献
7.
The species resulting in CO, CO+H2 or CO+D2O adsorption on supported Ni catalysts were followed by IR spectroscopy and their role in methane synthesis mechanism is discussed.
- , CO, CO+H2 CO+D2O . .相似文献
8.
Neuner U Bock R Roth M Spiller P Constantin C Funk UN Geissel M Hakuli S Hoffmann DH Jacoby J Kozyreva A Tahir NA Udrea S Varentsov D Tauschwitz A 《Physical review letters》2000,85(21):4518-4521
A specifically tailored plasma lens could shape a high-energy, heavy-ion beam into the form of a hollow cylinder without loss of beam intensity. It has been experimentally confirmed that both a positive as well as a negative radial gradient of the current density in the active plasma lens can be the underlying principle. Calculations were performed that yield the ideal current density distribution for both cases. A numerical simulation of an experiment with an intense ion beam highlights that the shaping of the beam increases the achievable compression in a lead sample. 相似文献
9.
Ana-Maria Acu 《Positivity》2017,21(1):283-297
In this paper some representations of a linear positive functional are established. These results are extended for linear positive operators \(L_n:C[a,b] \rightarrow C[a,b]\). Also, approximation properties of linear positive operators, expressed in terms of moduli of smoothness, are considered. In the last section, the remainder term in various approximation processes is studied. 相似文献
10.
Simple and low cost biosensor based on screen-printed electrode for sensitive detection of some alkylphenols was developed, by entrapment of HRP in a nanocomposite gel based on single-walled carbon nanotubes (SWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid. Raman and FTIR spectroscopy, CV and EIS studies demonstrate the interaction between SWCNTs and ionic liquid. The nanocomposite gel, SWCNT-[BMIM][PF6] provides to the modified sensor a considerable enhanced electrocatalytic activity toward hydrogen peroxide reduction. The HRP based biosensor exhibits high sensitivity and good stability, allowing a detection of the alkylphenols at an applied potential of −0.2 V vs. Ag/AgCl, in linear range from 5.5 to 97.7 μM for 4-t-octylphenol and respectively, between 5.5 and 140 μM for 4-n-nonylphenol, with a response time of about 5 s. The detection limit was 1.1 μM for 4-t-octylphenol, and respectively 0.4 μM for 4-n-nonylphenol (S/N = 3). 相似文献