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1.
An efficient stereoselective three-component reaction for the synthesis of functionalized spiro[4H-pyran-3,3′-oxindole] derivatives was realized through an organocatalyzed domino Knoevenagel/Michael/cyclization reaction using a cinchonidine-derived thiourea as the catalyst. Using water as the additive was found to improve the product ee values significantly. Under the optimized conditions, the reactions between isatins, malononitrile, and 1,3-dicarbonyl compounds yield the desired spirooxindole products in good yields (71–92%) and moderate to high ee values (up to 87% ee). 相似文献
2.
Venkatapuram Padmavathi Kaveti Sudheer Dandu Rangayapalle Chinna Venkata Subbaiah Konda Mahesh 《Journal of heterocyclic chemistry》2008,45(2):513-519
A new class of spiro heterocycles viz., spiropyrazolidinediones, isoxazolidinediones, pyrimidinetriones or thioxopyrimidinediones are developed from methyl 3‐aryl‐2‐(Z‐arylethenenylsulfonyl)acrylate by double Michael addition reaction with dimethyl malonate followed by cyclocondensation with appropriate nucleophiles. 相似文献
3.
Venkatapuram Padmavathi Annaji Venkata Nagendra Mohan Konda Mahesh 《Journal of heterocyclic chemistry》2008,45(4):1131-1138
Novel bisheterocycles, 1,2,3‐selenadiazoles, thiadiazoles and 2H‐diazaphospholes in combination with oxadiazoles, thiadiazoles and triazoles were prepared from phenacylsulfonylacetic acid methyl ester. 相似文献
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5.
Takimiya K Kunugi Y Konda Y Niihara N Otsubo T 《Journal of the American Chemical Society》2004,126(16):5084-5085
2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes including thiophene, selenophene, and tellurophene analogues as organic semiconductors for field-effect transistors were effectively synthesized in three steps from commercially available 1,4-dibromobenzene. All three benzodichalcogenophenes acted as good p-type semiconductors, and particularly the selenophene analogue, 2,6-diphenylbenzo[1,2-b:4,5-b']diselenophene, showed high FET mobility of 0.17 cm2 V-1 s-1. 相似文献
6.
Adusumilli Srikrishna Vijendra H. Pardeshi Konda Mahesh 《Tetrahedron: Asymmetry》2010,21(20):2512-2516
The enantiospecific total synthesis of two epimers of the sesquiterpene isocalamusenone has been accomplished starting from the readily available monoterpene (R)-limonene, which of the natural product established the stereostructure and the absolute configuration. 相似文献
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8.
An analytical study is reported of melting of a snow layer in an aqueous solution. A diffusion-controlled analytical model was proposed to the melting under an ideal condition that an aqueous solution was instantaneously filled up by a snow layer at the same temperature as the solution. The analytical results gave a qualitative prediction of the experimental results of the melting of snow layers suddenly immersed in a calcium chloride aqueous solution. The temperature in a melting system decreased rapidly during the melting process. The melting was complete within a few seconds, which denoted a thermodynamic equilibrium. When the initial temperatureT i and the initial porosity of snow ? i were the same, the initial concentrationC mi in the solution strongly affected both the decrease in temperature in the melting system and the melting mass per unit volume of snowM. WhenC mi andT i were the same, the maximum melting mass per unit volume of snowM max was not largely affected by snow particle diameters. A figure was presented for the relationM max?T i,C mi, and ? i , and also a relationship was presented to easily predict the non-dimensional maximum melting massM max * . 相似文献
9.
A number of recent studies have shown that mechanical stress can significantly lower or raise the activation barrier of a chemical reaction. Within a common approximation due to Bell [Science 200, 618 (1978)], this barrier is linearly dependent on the applied force. A simple extension of Bell's theory that includes higher order corrections in the force predicts that the force-induced change in the activation energy will be given by -FΔR - ΔχF(2)∕2. Here, ΔR is the change of the distance between the atoms, at which the force F is applied, from the reactant to the transition state, and Δχ is the corresponding change in the mechanical compliance of the molecule. Application of this formula to the electrocyclic ring-opening of cis and trans 1,2-dimethylbenzocyclobutene shows that this extension of Bell's theory essentially recovers the force dependence of the barrier, while the original Bell formula exhibits significant errors. Because the extended Bell theory avoids explicit inclusion of the mechanical stress or strain in electronic structure calculations, it allows a computationally efficient characterization of the effect of mechanical forces on chemical processes. That is, the mechanical susceptibility of any reaction pathway is described in terms of two parameters, ΔR and Δχ, both readily computable at zero force. 相似文献
10.
Structural Chemistry - This work reports hydrogen uptake capacity and equilibrium isotope effect (EIE) for the Be, Li, and Ti-doped closoborate (B6H6) complexes using first-principles calculations... 相似文献