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11.
The mechanism of the decomposition of acryloylcarbamates 7a–b yielding highly reactive isocyanates 3a–b was proposed based on NMR measurements and quantum chemical calculations. A good agreement between the experimental kinetic data and DFT calculations allowed us to demonstrate that the stability of 7a–d depends on the presence of methyl in the acryloyl moiety and the position of the nitro group in the nitrophenolic part of the molecule. Furthermore, the reactivity of 7a–d with weakly nucleophilic and sterically hindered 2,4,6‐tri‐tert‐butylaniline was explored by 1H NMR demonstrating the usefulness of reagents 7a–d offering access to a variety of 1‐N‐substituted uracils and thymines with potentially interesting biological properties. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
12.
We have analyzed the vibrational spectra of uracil and its methyl-substituted derivatives using the DFT/B3LYP/6-31G(p,d) method,
in the anharmonic approximation. We have shown that it is possible to use second-order anharmonic theory of vibrational spectra
in predictive calculations for substituted uracils.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 431–436, July–August, 2006. 相似文献
13.
Malihe Javan Khoshkholgh Hamid Reza Bijanzadeh Jürgen H. Gross 《Tetrahedron letters》2008,49(49):6965-6968
An efficient synthesis of tetracyclic uracil derivatives (polycyclic pyrans) is achieved via domino Knoevenagel-hetero-Diels-Alder reactions of O-propargylated salicylaldehyde derivatives with 1,3-dimethylbarbituric acid in water as solvent in the presence of CuI. The products are formed in good yields. 相似文献
14.
基于尿嘧啶作为一种碱基,具备一定的分子识别能力,制备了一种新颖的尿嘧啶共价修饰电极,用X射线光电子能谱和电化学方法进行了表征,并研究了酪氨酸、色氨酸、儿茶酚胺(如多巴胺,肾上腺素,去甲肾上腺素)及相关的化合物尿酸、抗坏血酸在该电极上的电化学行为,获得相应的氧化电位、电流灵敏度、线性范围和检测限等信息。其中,色氨酸检测线性范围:1.8 - 120 mM,检测限(s/n=3):0.8 mM;酪氨酸检测线性范围:1.8 - 89mM,检测限(s/n=3):0.8 mM。实验表明,尿嘧啶修饰电极能催化氧化上述电活性物质,但催化能力不同,据此,我们讨论了尿嘧啶与上述物质的相互作用,详细探讨了催化机理,扩展了对基于分子识别的传感器的研究。 相似文献
15.
Michael Meyer Thomas Steinke Maria Brandl Jürgen Sühnel 《Journal of computational chemistry》2001,22(1):109-124
The structures and interaction energies of guanine and uracil quartets have been determined by B3LYP hybrid density‐functional calculations. The total interaction energy ΔET of the C4h‐symmetric guanine quartet consisting of Hoogsteen‐type base pairs with two hydrogen bonds between two neighbor bases is −66.07 kcal/mol at the highest level. The uracil quartet with C6 H6O4 interactions between the individual bases has only a small interaction energy of −20.92 kcal mol−1, and the interaction energy of −24.63 kcal/mol for the alternative structure with N3 H3O4 hydrogen bonds is only slightly more negative. Cooperative effects contribute between 10 and 25% to all interaction energies. Complexes of metal ions with G‐quartets can be classified into different structure types. The one with Ca2+ in the central cavity adopts a C4h‐symmetric structure with coplanar bases, whereas the energies of the planar and nonplanar Na+ complexes are almost identical. The small ions Li+, Be2+, Cu+, and Zn2+ prefer a nonplanar S4‐symmetric structure. The lack of coplanarity prevents probably a stacking of these base quartets. The central cavity is too small for K+ ions and, therefore, this ion favors in contrast to all other investigated ions a C4‐symmetric complex, which is 4.73 kcal/mol more stable than the C4h‐symmetric one. The distance 1.665 Å between K+ and the root‐mean‐square plane of the guanine bases is approximately half of the distance between two stacked G‐quartets. The total interaction energy of alkaline earth ion complexes exceeds those with alkali ions. Within both groups of ions the interaction energy decreases with an increasing row position in the periodic table. The B3LYP and BLYP methods lead to similar structures and energies. Both methods are suitable for hydrogen‐bonded biological systems. Compared with the before‐mentioned methods, the HCTH functional leads to longer hydrogen bonds and different relative energies for two U‐quartets. Finally, we calculated also structures and relative energies with the MMFF94 forcefield. Contrary to all DFT methods, MMFF94 predicts bifurcated C HO contacts in the uracil quartet. In the G‐quartet, the MMFF94 hydrogen bond distances N2 H22N7 are shorter than the DFT distances, whereas the N1 H1O6 distances are longer. © 2000 John Wiley & Sons, Inc. J Comput Chem 22: 109–124, 2001 相似文献
16.
Lamsabhi AM Mó O Gutiérrez-Oliva S Pérez P Toro-Labbé A Yáñez M 《Journal of computational chemistry》2009,30(3):389-398
The intermolecular double proton transfer in dimers of uracil and 2-thiouracil is studied through density functional theory calculations. The reaction force framework provides the basis for characterizing the mechanism that in all cases has been associated to a dynamic balance between polarization and charge transfer effects. It has been found that the barriers for proton transfer depend upon the nature of the acceptor atoms and its position within the seminal monomer. Actually, the change in the nature of the hydrogen bonds connecting the two monomers along the reaction coordinate may favor or disfavor the double-proton transfer. 相似文献
17.
Danillo Valverde Adalberto V. S. de Araújo Antonio Carlos Borin 《Molecules (Basel, Switzerland)》2021,26(17)
The photophysical relaxation mechanisms of 1-cyclohexyluracil, in vacuum and water, were investigated by employing the Multi-State CASPT2 (MS-CASPT2, Multi-State Complete Active-Space Second-Order Perturbation Theory) quantum chemical method and Dunning’s cc-pVDZ basis sets. In both environments, our results suggest that the primary photophysical event is the population of the bright state. Afterwards, two likely deactivation pathways can take place, which is sustained by linear interpolation in internal coordinates defined via Z-Matrix scans connecting the most important characteristic points. The first one (Route 1) is the same relaxation mechanism observed for uracil, its canonical analogue, i.e., internal conversion to the ground state through an ethylenic-like conical intersection. The other route (Route 2) is the direct population transfer from the bright state to the triplet state via an intersystem crossing process involving the (/) singlet-triplet crossing point. As the spin-orbit coupling is not too large in either environment, we propose that most of the electronic population initially on the state returns to the ground following the same ultrafast deactivation mechanism observed in uracil (Route 1), while a smaller percentage goes to the triplet manifold. The presence of a minimum on the potential energy hypersurface in water can help to understand why experimentally it is noticed suppression of the triplet states population in polar protic solvent. 相似文献
18.
19.
Poly(alkylene phosphate)s bearing regularly distributed uracil moiety in the main chain have been obtained. The synthetic procedure consists of condensation of bis(diethylamino)-methoxyphosphine with N1,N3-bis(2′-hydroxyethyl) uracil followed by oxidation, dealkylation, and transformation to the resulting sodium polysalt. The final polymer ($\bar M_n \approx 10^4 $) as well as the intermediate products were characterized by 1H-, 13C-, and 31P-NMR spectroscopy. 相似文献
20.
Structure and Reactivity of Uracil Derivatives. 2. Ambident Nucleophilic Reactivity of 5-Diazouracil
On the basis of 3-21G type ab initio calculations we have studied all the possible complexes of 5-diazouracil with boron trifluoride. The most stable of these are the systems with the BF3 coordinated at the 3, 9, and 10 positions of the heterocyclic molecule. 相似文献