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91.
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
92.
Parvin Askari Ali Faraji Gholamreza Khayatian Sajjad Mohebbi 《Journal of the Iranian Chemical Society》2017,14(3):613-621
A series of new (MgO) x CuO and (MgO) x MnO2 nanocomposites were prepared and used as adsorbent for removal of As3+, Hg2+, and Pb2+ ions from aqueous solution with high capacity and detection limit. These nanocomposites were synthesized with different molar ratios by sonochemical method in alkaline solution using polyvinylpyrrolidone as a capping agent and were characterized by FTIR, AAS, UV–Vis spectroscopy, and TEM and SEM imaging. The maximum heavy metal ions adsorption was achieved for (MgO)0.32CuO and (MgO)2.9MnO2 nanocomposites assisted by 3-min sonication using ultrasound. Adsorbent capacity of (MgO)0.32CuO reached 500.0 mg/g and detection limit was 0.1 ppb for As3+. Also (MgO)2.9MnO2 nanocomposite adsorbed 457.1 mg/g of Hg2+ and 461.2 mg/g of Pb2+. Extremely low detection limits of 1.5 and 2.0 ppb were obtained for Hg(II) and Pb(II) ions, respectively, which are much lower than the WHO allowable limits. So, these nanocomposites should be excellent candidate for heavy metal removal with advantage of high capacity, high sensitivity, cost effectiveness and easy preparation. 相似文献
93.
Global results for semilinear hyperbolic equations with damping term on manifolds with conical singularity 下载免费PDF全文
Mohsen Alimohammady Morteza Koozehgar Kalleji Gholamreza Karamali 《Mathematical Methods in the Applied Sciences》2017,40(11):4160-4178
In this paper, we apply the family of potential wells to the initial boundary value problem of semilinear hyperbolic equations on the cone Sobolev spaces. We not only give some results of global existence and nonexistence of solutions but also obtain the vacuum isolating of solutions. Finally, we show blow‐up in finite time of solutions on a manifold with conical singularities. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
94.
Zahra?Emami Qingkai?Meng Gholamreza?Pircheraghi Ica?Manas-ZloczowerEmail author 《Cellulose (London, England)》2015,22(5):3161-3176
Cellulose nanowhiskers (CNWs) prepared via TEMPO mediated oxidation are used as biodegradable filler in an epoxy matrix. Since CNWs are hydrophilic and epoxy is hydrophobic, amphiphilic block copolymer surfactants are employed to improve the interactions between the filler and the matrix. The surfactants used are Pluronics, a family of triblock copolymers containing two poly(ethylene oxide) blocks and one poly(propylene oxide) block. In this study, Pluronic L61 and L121 with molecular weight of 2000 and 4400 g/mol and hydrophilic to lipophilic balance of 3 and 1 respectively, are used and their effect on the dispersion of CNWs in epoxy is discussed. The hydrophilic tails of Pluronics interact with the hydroxyl and carboxylic groups on the CNW surface and then these surfactant-treated CNWs are directly incorporated into epoxy by high speed mixing. The dispersion state of the surfactant-treated CNWs in epoxy is assessed by rheological measurements and the mechanical properties of the resulting composites are characterized by tensile test and dynamic mechanical thermal analysis. The Pluronic L61 treated CNW/epoxy composites show the highest storage modulus at high temperatures (about 77 % increases) indicative of improved interfacial interactions between the CNWs and the epoxy matrix. Also, an increase of around 10 °C in the glass–rubbery transition temperature of the L61 treated CNW/epoxy composite leads to potential application at higher service temperatures. 相似文献
95.
Ali Khalafi‐Nezhad Abdolkarim Zare Abolfath Parhami Mohammad Navid Soltani Rad Gholam Reza Nejabat 《合成通讯》2013,43(23):3549-3562
N‐Arylation of some pyrimidine and purine nucleobases in the presence of SiO2 and Cs2CO3 under solvent‐free as well as in solution conditions is described. In these conditions, N1‐aryl pyrimidines and N9‐aryl purines have been obtained regioselectively in moderate to high yields with relatively short reaction times. 相似文献
96.
Sedigheh Borhani Seyed Gholamreza Etemad Seyed Abdolkarim Hosseini Ravandi 《Heat and Mass Transfer》2011,47(7):807-811
In this study a non-conventional electrospinning technique was designed for the production of high bulky polyacrylonitrile
(PAN) nanofiber mats. Optimum nanofiber mats are achieved with 15 wt.% solution of PAN in dimethylformamide. Such mats result
in a bulk porosity which is as high as 99.9 and a density as low as 0.84 × 10−3 g/cm3. The effect of the porosity of nanofiber mats on the air permeability and coupled heat and moisture transfer of fibers was
investigated. Based on the results, high bulky nanofiber mats possess high heat and moisture transfer. Experimental data reveal
that upon a slight decrease in the bulk porosity, air permeability and heat transfer decrease noticeably, while moisture transfer
variation is low. 相似文献
97.
Golipour-Chobar Elnaz Salimi Farshid Ebrahimzadeh Rajaei Gholamreza 《Monatshefte für Chemie / Chemical Monthly》2020,151(3):309-318
Monatshefte für Chemie - Chemical Monthly - Previous reports were shown that boron nitride nanostructures can be biocompatible and nontoxic. Therefore, interaction of lomustine as an... 相似文献
98.
Hossein Tavakol Gita Gaimech Shahryar Ghammamy Gholamreza Rezaei Bebahani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2464-2471
The synthesis of six tetraalkylammonium bromopentachlorophosphoride ionic liquids (ILs) is reported here. Their structures were determined by IR, 1H NMR, and 13C NMR spectroscopy. Moreover, thermogravimetric (TG) and differential thermal analysis (DTA) were used to investigate the thermal behavior of these compounds. The results show that these ILs have excellent thermal stability below 145°C, and by decreasing the size of the alkyl groups, the thermal stabilities will increase. Along with the experimental study, these compounds have been studied computationally at the B3LYP/LANL2DZ level of theory using the PC GAMESS/Firefly program package. From these calculations, optimized geometries, molecular parameters, and vibrational spectra of ILs have been calculated. In addition, calculated frequencies are compared with the experimental frequencies after correction by the appropriate scaling factor. This comparison shows that our theoretical data are in good agreement with the experimental results. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
99.
Numerical Algorithms - For their several attractive features from the viewpoint of the numerical computations, linear barycentric rational interpolants have been recently used to construct various... 相似文献
100.
An environmentally friendly copper‐based catalyst supported on 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 was prepared and characterized by Fourier transform‐infrared, transmission electron microscopy, field emission‐scanning electron microscopy, X‐ray diffraction and inductively coupled plasma techniques. The catalyst was applied for the one‐pot three‐component C–S coupling reactions of aryl halides with benzyl bromide and thiourea under aerobic conditions to afford the corresponding coupled products in good yields in water. The catalyst could be recovered and recycled five times. These results prove 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 supported Cu (II) complex was not leached during the reaction. Also it shows the correct heterogeneous nature of the catalyst. 相似文献