全文获取类型
收费全文 | 204篇 |
免费 | 10篇 |
国内免费 | 5篇 |
专业分类
化学 | 109篇 |
晶体学 | 2篇 |
力学 | 15篇 |
数学 | 19篇 |
物理学 | 39篇 |
无线电 | 35篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 7篇 |
2016年 | 26篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 17篇 |
2010年 | 14篇 |
2009年 | 9篇 |
2008年 | 14篇 |
2007年 | 6篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1994年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有219条查询结果,搜索用时 593 毫秒
141.
Farzad Hosseini Bahmaei Manochehr Davallo Mehran 《Russian Journal of Electrochemistry》2021,57(4):357-374
Russian Journal of Electrochemistry - A Cu2O–CuO/rGO/CPE was used for simultaneous measurement of propranolol (PRO), Acetaminophen (AC) and folic acid (FA) using differential pulse... 相似文献
142.
Daryoush Afzali Ali Mostafavi Farzad Etemadi Ali Ghazizadeh 《Arabian Journal of Chemistry》2012,5(2):187-191
In this work, the potential of modified multiwalled carbon nanotubes for separation and preconcentration of trace amounts of manganese ion is studied. Multiwalled carbon nanotubes were oxidized with concentrated HNO3 and then modified with loading 1-(2-pyridylazo)-2-naphtol. Mn(II) ions could be quantitatively retained by modified multiwalled carbon nanotubes in the pH range of 8–9.5. Elution of the adsorbed manganese was carried out with 5.0 mL of 0.1 mol L?1 HNO3. Detection limit is 0.058 ng mL?1 and analytical curve is linear in the range of 0.1 ng mL?1–5.0 μg mL?1 in the initial solution with a correlation coefficient 0.9977 and the preconcentration factor is 100. Relative standard deviation for eight replicate determination of 0.5 μg mL?1 of manganese in the final solution is 0.41%. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type, breakthrough volume and interference ions, were studied for preconcentration of Mn(II) ions in detail to optimize the conditions. The method was successfully applied for separation, preconcentration and determination of manganese in different samples. 相似文献
143.
Farzad Alavi 《Molecular physics》2013,111(1):161-174
A dipolar–quadrupolar contribution to the residual Helmholtz energy for a polar square well (a square well plus either a point dipole or a point quadrupole) fluid is developed based on the Padé approximation. Taking the square well system as reference, the contribution is formulated using an expansion for radial distribution function of the reference system. In addition to square well potential parameters the contribution depends only on dipole and quadrupole moments. This term is added as perturbation to a generalized equation of state for square well fluids. The results are then compared with the available simulation data in the literature. With the new equation obtained, it was possible to predict liquid–vapour equilibrium properties and critical properties of polar square well fluids more accurately than with available perturbation theories for multipolar square well systems. Application of the equation of state to a real dipolar (water) and a real quadrupolar (carbon dioxide) fluid indicated that the polar contribution greatly improved the predictions of saturation properties. Accurate prediction of critical properties for polar square well fluids remains as a challenge. This work can be useful in the development of better equations of state. 相似文献
144.
Ehtemam F Forbes PA Schouten AC van der Helm FC Happee R 《IEEE transactions on bio-medical engineering》2012,59(7):1978-1984
Humans actively stabilize the head-neck system based on vestibular, proprioceptive and visual information. Galvanic vestibular stimulation (GVS) has been used previously to demonstrate the role of vestibular feedback in standing balance. This study explores the effect of GVS on head-neck kinematics and evaluates the approach to investigate the vestibular contribution to head-neck stabilization. GVS was applied to 11 seated subjects using seven different stimuli (single sinusoids and multisines) at amplitudes of 0.5-2 mA and frequencies of 0.4-5.2 Hz using a bilateral bipolar configuration while 3-D head and torso kinematics were recorded using motion capture. System identification techniques were used evaluating coherence and frequency response functions (FRFs). GVS resulted in significant coherence in roll, yaw and lateral translation, consistent with effects of GVS while standing as reported in the literature. The gain of the FRFs varied with frequency and no modulation was observed across the stimulus amplitudes, indicating a linear system response for the stimulations considered. Compared to single sine stimulation, equivalent FRFs were observed during unpredictable multisine stimulation, suggesting the responses during both stimuli to be of a reflexive nature. These results demonstrate the potential of GVS to investigate the vestibular contribution to head-neck stabilization. 相似文献
145.
Mohebbi S Falcón-Pérez JM González E Millet O Mato JM Kobarfard F 《Chemical & pharmaceutical bulletin》2012,60(1):70-78
A series of 2-substituted-4,6-diaminipyrimidine derivatives were synthesized and evaluated for their dihydrofolate reductase (DHFR) inhibitory activity. Saturation transfer difference (STD) (1)H-NMR experiments were used to probe the binding characteristics of the compounds with human DHFR enzyme. The most potent molecules, 12 and 15, in enzyme assay study showed the best results in STD experiments indicating their intimate interaction with the receptor. The docking studies were followed to explain the structural basis for the observed interaction between the ligands and DHFR. All the compounds were also assayed in vitro for their growth inhibitory activity on MCF-7, HepG2, SKHep1, and Hela tumor cell lines. Compounds 16, 17, and 22 demonstrated the most potent in vitro anti-proliferative activity among the others. 相似文献
146.
H. Raissi Abraham F. Jalbout B. Abbasi F. Fazli F. Farzad E. Nadim Aned de Leon 《International journal of quantum chemistry》2010,110(4):893-901
The molecular structure and intramolecular hydrogen bond energy of 18 conformers of 3‐imino‐propenyl‐amine were investigated at MP2 and B3LYP levels of theory using the standard 6‐311++G** basis set. The atom in molecules or AIM theory of Bader, which is based on the topological properties of the electron density (ρ), was used additionally and the natural bond orbital (NBO) analysis was also carried out. Furthermore calculations for all possible conformations of 3‐imino‐propenyl‐amin in water solution were also carried out at B3LYP/6‐311++G** and MP2/6‐311++G** levels of theory. The calculated geometrical parameters and conformational analyses in gas phase and water solution show that the imine–amine conformers of this compound are more stable than the other conformers. B3LYP method predicts the IMA‐1 as global minimum. This stability is mainly due to the formation of a strong N? H···N intramolecular hydrogen bond, which is assisted by π‐electrons resonance, and this π‐electrons are established by NH2 functional group. Hydrogen bond energies for all conformers of 3‐imino‐propenyl‐amine were obtained from the related rotamers methods. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
147.
Despite its success for modeling electrolyte thermodynamics in aqueous media, the use of the Pitzer approach for the investigation
of electrolytes in nonaqueous or in mixed solvent media is still very limited. Further, a review of the literature reveals
that there are no more than a few research groups who have used the exact form of the Pitzer–Simonson–Clegg (PSC) ion-interaction
approach for the investigation of electrolytes in mixed solvent systems. As a continuation of our previous studies, the present
investigation reports modeling of HCl in the 2-propanol + water mixed solvent system with the Pitzer, PSC and an extended
form of the PSC ion-interaction approaches using the experimental potentiometric data from a cell containing pH glass membrane
and Ag/AgCl electrodes. The electrochemical measurements were performed over the HCl molality range from 0.01 to 4.5 mol⋅kg−1 in mixed 2-propanol (x%)+water (100−x%) solvents, with different solvent percent mass fractions (x%=10,20,30,40 and 50%) at 298.15±0.05 K. 相似文献
148.
149.
Farzad Nasirpouri 《Ionics》2011,17(4):331-337
Electrodeposition mechanism of lead on polycrystalline copper from a perchlorate solution in the presence of chloride ions
was investigated. Electrochemical quartz crystal microbalance data including frequency and resistance were simultaneously
recorded with cyclic voltammograms and current transients. The change of frequency and resistance shows that a rigid bulk
film forms at the potentials more negative than −0.52 V saturated calomel electrode (SCE), exhibiting the overpotential deposits
of Pb (OPD). However, at the potentials ranging from −0.38 to −0.43 V SCE, a monolayer of lead as the underpotential deposit
of Pb (UPD) is formed. The measured real mass of the OPD of Pb compared to the charge passed through the cell elucidates the
formation of Pb (II). The magnitude of the applied overpotential has considerable effect on the growth of the OPD of lead.
The Pb OPDs formed at the lower overpotentials (or applied potentials in a range of −0.54 to −0.58 V SCE) show slight positive
deviation of the electrochemical equivalent (M/n) of Pb (II). We ascribe this evidence to the possible incorporation of adsorbed/alloyed elements like chlorine in the film
composition. At the higher overpotentials (or applied potentials of negative than −0.58 V SCE), the ratio starts to decrease,
mainly due to the hydrogen evolution associated with the possible morphology change of deposit. Our results also show that
the nucleation and growth of Pb OPD can be described with the instantaneous mechanism based on Scharifker–Hills prediction
with nondimensional plots. 相似文献
150.