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排序方式: 共有311条查询结果,搜索用时 281 毫秒
211.
Natarajan Arumugam Abdulrahman I. Almansour Raju Suresh Kumar Vagolu Siva Krishna Dharmarajan Sriram Ramanathan Padmanaban 《Arabian Journal of Chemistry》2021,14(2):102938
A stereo- and regioselective synthesis of hitherto unexplored novel class of β-lactam embedded spirooxindolopyrrolidine hybrid heterocycles have been accomplished via ionic liquid accelerated [3 + 2]-cycloaddition reaction process. The expected unusual lactonization/lactamization product could not be observed even in traces. The in vitro antimycobacterium tubercular activity of the synthesized spiroheterocyclic hybrids were assessed against Mycobacterium tuberculosis H37Rv. Among them, the compounds with no substitution and chlorosubstitution on the oxindole ring showed the most potent activity with a MIC 0.78 μg/mL and 1.56 μg/mL, respectively which were two-fold and equal activity than the standard drug, ethambutol (MIC = 1.56 μg/mL). 相似文献
212.
The Theoretical and Experimental Studies on Oxidation of Straight Chain Amino Acids in Moderately Concentrated Sulfuric Acid Medium 下载免费PDF全文
Homayoon Bahrami Gholamreza Jaferian Mehdi D. Davari Mansour Zahedi Ali Akbar Moosavi‐Movahedi 《国际化学动力学杂志》2016,48(11):647-659
The kinetics of the permanganic oxidation process of some straight chain amino acids in moderately concentrated sulfuric acid medium have been investigated using a spectrophotometric technique. Conclusive evidences have proven autocatalytic activity of Mn(II) for these reactions. It is determined that even and odd effects of the number carbon atom in a carbon chain are annihilated when it's the number of carbon atoms is increased more than of three in a noncatalytic oxidation pathway. Thus, rate constants belonging to glycine, l ‐α‐amino‐n‐butyric acid, l ‐norleucine, and l ‐α‐amino‐n‐heptanoic acid satisfy Taft's equation involving the induction factor in the noncatalytic pathway, whereas l ‐α‐amino‐n‐heptanoic acid has an odd number of carbon atom in its chain carbon. On the other hand, in the catalytic pathway, rate constants satisfy Taft' equation including inductive and steric factors, when rate constants belonging to amino acids with an even number of carbon atoms are separated from those with an odd number of carbon atoms. The oxidation process of amino acids in the noncatalytic pathway and those with the even number of carbon atoms in the carbon chain in the catalytic pathway speeds up by an increase in the length of chain that is accompanied with an increase in the carbon chain's electron‐donating characteristic. On the other hand, an increase in the length of the carbon chain is accompanied with more steric hindrance, which counteracts its electron‐donating character, thereby decreasing reaction rate in the catalytic pathway. Finally, amino acid–Mn(II) complexes were studied using a density functional theory method. Results obtained show that such a complex is less stable than reactants, namely it is formed in an endothermic reaction. The number and strength of hydrogen bonding belonging to amino acid is more than those of the amino acid–Mn(II) complex. Besides, it has been illustrated that natural bond orbital analysis and molecular orbital calculations satisfy the findings. 相似文献
213.
Sodium hexafluorosilicate (Na2SiF6) powder has been used as a silicon source for formation of Si3N4 coatings by the hybrid precursor system‐chemical vapor deposition (HYSY‐CVD) route. The quantitative effect of processing time, temperature, gas flow rate, and process atmosphere (N2 and N2:5% NH3) upon the fractional weight loss during the decomposition of Na2SiF6 was studied using a standard L9 Taguchi experimental design and analysis of variance. The decomposition kinetics of Na2SiF6(s) was studied theoretically and experimentally in the temperature range of 550–650ºC by applying the shrinking core model. It was found that regardless of atmosphere type, the reaction order is n ≈ 0.12 and that a two‐stage mixed mechanism consisting of chemical reaction and boundary layer gas transfer controls the decomposition rate. The determined fractional weight loss during Na2SiF6 decomposition in nitrogen atmosphere is about 1.05–1.5 orders of magnitude greater than that in N2:NH3. The gas flow rate affects the dissociation activation energy, being of 121, 109, and 94 kJ/mol in N2 and of 140, 120, and 115 kJ/mol in N2:NH3, for the flow rates of 20, 60, and 100 cm3/min, respectively, in both atmosphere types. A good agreement is observed by comparing experimental weight loss data with model predictions. 相似文献
214.
Synthesis,characterization and application of graphene palladium porphyrin as a nanocatalyst for the coupling reactions such as: Suzuki‐Miyaura and Mizoroki‐Heck 下载免费PDF全文
The palladium(II)‐coordinated 5,10,15,20‐tetrakis‐(4‐hexyloxyphenyl)‐porphyrin as a macrocyclic palladium complex was covalently grafted to the surface of graphene oxide (denoted as GO‐CPTMS@Pd‐TKHPP). GO‐CPTMS@Pd‐TKHPP was characterized using microscopic and spectroscopic techniques for confirmation of functionalization. The synthesized catalyst was checked in the Suzuki‐Miyaura and the Mizoroki‐Heck coupling reactions. The catalyst is very easy to handle, environmentally safe and economical. Also, this catalytic system shows high catalytic activity and the yields of the products are excellent. Moreover, the suggested catalyst was reusable for five runs with no significant decrease in catalytic activity. 相似文献
215.
216.
S. Jafar Hoseini Mehrangiz Bahrami Mahnaz Maddahfar Roghayeh Hashemi Fath Mahmoud Roushani 《应用有机金属化学》2018,32(1)
This study describes the polymerization of graphene oxide (GO) nanosheet to reduced‐GO‐aminoclay (RGC) by covalent functionalization of chemically reactive epoxy groups on the basal planes of GO with amine groups of magnesium phyllosilicate clay (known as aminoclay). The resulting RGC sheets were characterized and applied to support platinum nanostructures at toluene/water interface. Pt nanoparticles (NPs) with diameters about several nanometers were adhered to RGC sheets by chemical reduction of [PtCl2(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) complex. Catalytic activity of Pt NPs thin films were investigated in the methanol oxidation reaction. Cyclic voltammetry results exhibit that the Pt/reduced‐GO (RGO) and Pt/RGC thin films showed improved catalytic activity in methanol oxidation reaction in comparison to other Pt NPs thin films, demonstrating that the prepared Pt/RGO and Pt/RGC thin films are promising catalysts for direct methanol fuel cell. 相似文献
217.
218.
Abbasali Mohammadi Fariba Bahrami Hakimeh Mohammadpour 《Applied Mathematics Letters》2012,25(9):1240-1244
In this paper, we investigate a minimization problem related to the principal eigenvalue of the Schrödinger operator. The optimized solution can be applied to design new electronic and photonic devices based on the quantum dots. 相似文献
219.
We carry out a coarse-grained molecular dynamics simulation of phospholipid vesicles with transmembrane proteins. We measure the mean and Gaussian curvatures of our protein-embedded vesicles and quantitatively show how protein clusters change the shapes of their host vesicles. The effects of depletion force and vesiculation on protein clustering are also investigated. By increasing the protein concentration, clusters are fragmented to smaller bundles, which are then redistributed to form more symmetric structures corresponding to lower bending energies. Big clusters and highly aspherical vesicles cannot be formed when the fraction of protein to lipid molecules is large. 相似文献