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851.
A four-component reaction of hydrazine hydrate or phenyl hydrazine, ethyl 3-alkyl-3-oxo propanoate, aldehydes and malononitrile has been achieved in the presence of nanosized magnesium oxide as a highly effective heterogeneous base catalyst to produce of 6-amino-3-alkyl-4-aryl-5-cyano-1,4-dihydropyrano[2,3-c]pyrazole derivatives in excellent yields and in a short experimental time. This method is simple and rapid for focusing a pyrano ring with a pyrazole ring. 相似文献
852.
853.
Homeira Ebrahimzadeh Nafiseh Shekari Najmeh Tavassoli Mostafa M. Amini Maryam Adineh Omid Sadeghi 《Mikrochimica acta》2010,170(1-2):171-178
Aminopropyl-functionalized mesoporous silicas, NH2-MCM-41 and NH2-SBA-15, as absorbents were utilized for rapid extraction, preconcentration and determination of trace amounts of silver. Flow rates of sample and eluent, pH, eluent solution, type, concentration and the least amount of eluent for desorption of silver ions were optimized; moreover, break through volume and the effect of various cationic interferences on the sorption of silver were evaluated. The extraction efficiency of silver ions was greater than 95% for MCM-41-NH2 and 85% for SBA-15-NH2 and the limit of detection (LOD) was less than 4 ng mL?1 for both functionalized mesoporous silicas. The preconcentration factor was greater than 210 and the relative standard deviation (RSD) was <2%. The adsorption capacity of the mesoporous silicas is higher than 143 mg g?1 for NH2-MCM-41 and 137 mg g?1 for NH2-SBA-15. Under similar experimental conditions the results for these solid phases were compared with each other. NH2-SBA-15, in spite of larger pore size diameter and adsorption of silver ions in higher flow rates has lower recovery and a higher RSD compared to MCM-41. This method has been applied to determine silver in photographic emulsions and real samples. 相似文献
854.
Abstract
The derivatization of a glassy carbon electrode surface was achieved with and without electrochemical reduction of various diazonium salts in acetonitrile solutions. The surfaces were characterized, before and after their attachment, by cyclic voltammetry and electrochemical impedance spectroscopy to evidence the formation of a coating on the carbon surface. The results were indicative of the presence of substituted phenyl groups on the investigated surface. Also, the effects of diazonium thin films at the surface of a glassy carbon electrode, modification time, and salt concentration on their electrochemical responses in the presence of the Fe(CN)63−/4− probe were investigated. Electrochemical impedance measurements indicated that the kinetics of electron transfer is slowed down when the time and the concentration used to modify the glassy carbon electrode are increased. We therefore modified a glassy carbon surface via its derivatization with and without electrochemical reduction of various diazonium salts in acetonitrile solution. 相似文献855.
Gohari AR Saeidnia S Malmir M Hadjiakhoondi A Ajani Y 《Natural product research》2010,24(20):1902-1906
The genus Salvia (Lamiaceae) contains more than 50 shrub species in Iran, and Salvia limbata C.A. Meyer grows widely in the north and central parts of the country. Six flavones and rosmarinic acid were isolated from the ethyl acetate and methanol extracts of the flowered aerial parts of S. limbata collected from Semnan province. The separation process was carried out using several chromatographic methods. Structural elucidation was based on NMR data, in comparison with those reported in the literature. The isolated compounds were identified as ladanein (1), salvigenin (2), luteolin 7-methyl ether (3), cirsiliol (4), eupatorin (5), luteolin 7-O-glucoside (6) and rosmarinic acid (7). Some of these flavonoids have been reported to show antibacterial and cytotoxic activities. 相似文献
856.
A completely analytical equation of state for pure hard chain fluids, derived on the basis of perturbation theory and reported in our previous work, is applied for the calculation of pVT properties and the prediction of vapour–liquid equilibria of n-alkanes and n-perfluoroalkanes. The molecules are treated as a chain formed from freely joined spheres which interact via an extended site-site square-well potential. The molecular parameters of compounds are obtained from the experimental compressibility factor data above the critical temperature. These parameters are capable of relatively satisfactory prediction of the vapour–liquid equilibrium coexistence curves of compounds. Linear relationships have been found between the potential parameters of fluids and their molecular weight, which make it possible to predict the pVT data and vapour–liquid phase equilibria of heavier compounds. 相似文献
857.
Fischer-Tropsch synthesis over ruthenium-promoted Co/Al2O3 catalyst with different reduction procedures
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Ali Karimi Ali Nakhaei Pour Farshad Torabi Behnam Hatami Ahmad Tavasoli Mohammad Reza Alaei Mohammad Irani 《天然气化学杂志》2010,19(5):503-508
The effect of reduction procedure on catalyst properties, activity and products selectivity of ruthenium-promoted Co/γ-Al2O3 catalyst in Fischer-Tropsch synthesis (FTS) was investigated. Catalyst samples were reduced with different reduction gas compositions and passivated before being characterized by TPR and XRD techniques. Different activity and product selectivity analyses were also performed. These results showed that the catalyst dispersion, particle size, and the degree of reduction changed with different reduction gas compositions, which were resulted from the water partial pressures in reduction process that give varying degrees of interaction with the support. It has been suggested that the FTS activity of cobalt catalyst was directly dependent on the catalyst reducibility. A reduction gas with a molar ratio of H2/He = 1 was used to prevent the formation of Co-support compound during catalyst reduction. 相似文献
858.
Seyedi Maryam Sadat Sohrabi Mahmoud Reza Motiee Fereshte Mortazavinik Saeid 《Research on Chemical Intermediates》2020,46(3):1645-1662
Research on Chemical Intermediates - A simple and fast method based on activated carbon@nanozerovalent iron–nickel (AC@nZVI/Ni) nanoadsorbent was developed for highly efficient removal of... 相似文献
859.
Mohammad Yousefi Mojdeh Safari Maryam Bikhof Torbati Vahid Molla Kazemiha Hassan Sanati Amir Amanzadeh 《应用有机金属化学》2012,26(8):438-444
Since organotin complexes have been reported to show fewer side effects relative to other heavy metal anticancer compounds, in the present study we report for the first time four novel organotin(IV) derivatives with the general formula R2SnL2, where R = methyl (1), n‐butyl (2), phenyl (3), benzyl (4) and L = morpholine‐1‐carbodithioate (MCDT). The newly synthesized ligand was monodentate or bidentate, coordinating through a sulfur atom. The complexes were synthesized by directly mixing, refluxing and stirring the ligand, with diorganotin(IV) dichlorides in a suitable solvent. The complexes were found to be pure and their solid and solution phase structural configuration was investigated by FT‐IR, multinuclear NMR (1 H, 13 C, 119Sn) and mass spectrometry. Complex 2 was also studied for its thermal decomposition by thermogravimetry and differential thermal analysis. The results obtained on the basis of these techniques are in full concurrence with the proposed 1:2 (Sn:L) stoichiometry. The cytotoxic activity of the MCDT and diorganotin(IV) complexes (1–4) was tested against tumor cell lines – human cervix carcinoma HeLa and human myelogenous leukemia K562 – and normal immunocompetent cells: peripheral blood mononuclear cells PBMC. Results of bioassay demonstrated that organotin derivatives were in general more active than the anticancer drug cisplatin. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
860.
Zahra Mohammadzahery Maryam Jandaghi Samira Alipour Siamak Dadras Shahram Kazemi Jamshid Sabbaghzadeh 《Optics & Laser Technology》2012,44(4):1095-1100
This study deals with the thermal characterization of a continuous wave (CW-) and end-pumped passively Q-switched microchip Nd:YAG laser crystal by solving the rate and heat transfer equations in the laser cavity. In this approach, a parametric study has been performed to investigate the influence of the pumping parameters, cooling metal dimension and also the crystal dimension and doping concentration on the thermal behavior of the laser crystal. Obtained results reveal a closed correlation between the mentioned parameters and the thermal behavior of the crystal indicating that a proper selection of the laser parameters is essential to control the crystal's temperature and improve the performance of the laser accordingly. 相似文献