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31.
Hiba Kottayil Shaibuna Machingal Sherly mole Parackal B. Shebitha Alungal M. Letcy V. Theresa Avudaiappan Govindan Sreekumar Krishnapillai 《Journal of heterocyclic chemistry》2020,57(9):3310-3317
A new polyamine was prepared by the ring opening polymerization of epichlorohydrin and properly characterized. The catalytic property of the prepared polymer was assessed by synthesizing 2-aryl-substituted benzimidazole and benzoxazole derivatives by the conjugation of o-phenylenediamine/o-aminophenol with various aromatic aldehydes in the presence of atmospheric oxygen. Significant attributes of the present synthesis include short reaction time, good to excellent yield, high purity, easy reusability, and room temperature reaction. The reaction was carried out in the absence of any metal catalyst and other cooxidants. 相似文献
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Highly regio- and stereoselective synthesis of tricyclic frameworks using Baylis-Hillman derivatives
Manickam Bakthadoss Nagappan Sivakumar Govindan Sivakumar Gandhi Murugan 《Tetrahedron letters》2008,49(5):820-823
A simple and convenient synthetic route for the synthesis of tricyclic chromeno[4,3-b]pyrrolidine frameworks using Baylis-Hillman bromides involving in situ formation of an imine, decarboxylation and a [3+2] cycloaddition sequence is described. 相似文献
34.
V. Krishnakumar Fazlur-Rahman Nawaz Khan Badal Kumar Mandal Sukanya Mitta Ramu Dhasamandha Vindhya Nanu Govindan 《Research on Chemical Intermediates》2012,38(8):1819-1826
The ethyl-2-chloroquinoline-3-carboxylates, 4, were achieved from o-aminobenzophenones in two steps. i.e. initially, the ethyl-2-oxoquinoline-3-carboxylates, 3, were obtained by base-catalyzed Friedlander condensations of o-aminobenzophenones, 1, and diethylmalonate, 2. The 2-chloroquinoline-3-carboxylates, 4, were then obtained by the reaction with POCl3 in good yields. The chemical structures were confirmed by FTIR, mass and 1H-NMR spectroscopic techniques. All the synthesized compounds were tested for their in vitro antibacterial activity against Bacillus subtilis and Vibrio cholera and found to possess moderate activity. 相似文献
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Krishna?Kishore?Kottapalli Kalyan?Kumar?Adari Parvataneni?VaniEmail author Sudarsan?Kochu?Govindan 《Transition Metal Chemistry》2005,30(7):773-777
The kinetics of oxidation of L-Cysteine in aqueous HClO4 medium were studied using a one-equivalent oxidant, hexachloroiridate(IV). The reaction exhibits second-order dependence
with respect to hexachloroiridate(IV) and first-order in cysteine. The rate decreases with increase in hydrogen ion concentration
indicating that the zwitterionic form of cysteine is more reactive. Cysteic acid is identified as the product of oxidation.
A suitable mechanism involving the formation of [IrCl6]2− – sulphur bonded intermediate is proposed. The activation parameters of the reaction are computed using the linear least
squares method and the values of Ea and ΔS# are found to be 27.97±1.82 kJ mol−1 and −51.30±6.0 J K−1mol−1, respectively. 相似文献
37.
Ruslan M. Minyaev Wolfgang Quapp Govindan Subramanian Paul von R. Schleyer Yirong Mo 《Journal of computational chemistry》1997,18(14):1792-1803
The paths of correlated internal disrotation (barrier less than 0.4 kcal/mol) and conrotation (barrier around 1.9 kcal/mol) of the two BH2 groups in H2BCH2BH2 have been computed employing ab initio [MP2(full)/6–31G**] and density functional theory (Becke3LYP/6–311+G**) methods. Two B(SINGLE BOND)C(DOTTED BOND)B(p) hyperconjugative interactions stabilize the Cs symmetric H2BCH2BH2 isomer ( 1 ). The B(SINGLE BOND)C(DOTTED BOND)B(p) hyperconjugative stabilization, evaluated by homodesmotic reactions and using the orbital deletion procedure (which “deactivates” the “vacant” born p orbital), is less than 6 kcal/mol in diborylmethane. The B(SINGLE BOND)C(DOTTED BOND)B(p) stabilization is shown to be remarkably large in C4B6H10 (Td). At MP2(fu)/6–31G**, disproportionation into 1 and methane is only 5.6 kcal/mol exothermic. The 1,3 H exchange in diborylmethane is an asynchronous process and proceeds via a doubly bridged cyclic intermediate with 9.3 kcal/mol barrier. Structures with “planar tetracoordinate” carbon are stabilized considerably by BH2 substituents, but they are still high in energy. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1792–1803, 1997 相似文献
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We discuss a model of an economic community consisting of N interacting agents. The state of each agent at any time is characterized, in general, by a mixed strategy profile drawn from a space of s pure strategies. The community evolves as agents update their strategy profiles in response to payoffs received from other agents. The evolution equation is a generalization of the replicator equation. We argue that when N is sufficiently large and the payoff matrix elements satisfy suitable inequalities, the community evolves to retain the full diversity of available strategies even as individual agents specialize to pure strategies. © 1998 John Wiley & Sons, Inc. 相似文献
40.
Using detrended fluctuation analysis (DFA), we studied the scaling properties of the time instances (occurrence) of the fetal breathing, gross-body, and extremity movements scored on a second by second basis from the recorded ultrasound measurements of 49 fetuses. The DFA exponent α of all the three movements of the fetuses varied between 0.63 and 1.1. We found an increase in α obtained for the movement due to breathing as a function of the gestational age while this trend was not observed for gross-body and extremity movements. This trend was argued as the indication of the maturation of lung and functional development of respiratory aspect of the fetal central nervous system. This result may be useful in discriminating normal fetuses from high-risk fetuses. 相似文献