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111.
《Mendeleev Communications》2020,30(2):145-146
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112.
Analysis of the Electronic Structure of Aqueous Urea and Its Derivatives: A Systematic Soft X‐Ray–TD‐DFT Approach
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Dr. Marc F. Tesch Ronny Golnak Felix Ehrhard Daniela Schön Dr. Jie Xiao Dr. Kaan Atak Dr. Annika Bande Prof. Emad F. Aziz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12040-12049
Soft X‐ray emission (XE), absorption (XA), and resonant inelastic scattering (RIXS) experiments have been conducted at the nitrogen K‐edge of urea and its derivatives in aqueous solution and were compared with density functional theory and time‐dependent density functional theory calculations. This comprehensive study provides detailed information on the occupied and unoccupied molecular orbitals of urea, thiourea, acetamide, dimethylurea, and biuret at valence levels. By identifying the electronic transitions that contribute to the experimental spectral features, the energy gap between the highest occupied and the lowest unoccupied molecular orbital of each molecule is determined. Moreover, a theoretical approach is introduced to simulate resonant inelastic X‐ray scattering spectra by adding an extra electron to the lowest unoccupied molecular orbital, thereby mimicking the real initial state of the core‐electron absorption before the subsequent relaxation process. 相似文献
113.
James J. Mousseau Liyan Xing Nathalie Tang Louis A. Cuccia Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(39):10030-10038
Herein we report the design and synthesis of crescent‐shaped and helical urea‐based foldamers, the curvature of which is controlled by varying the constituent building blocks and their connectivity. These oligomers are comprised of two, three or five alternating aromatic heterocycles (pyridazine, pyrimidine or pyrazine) and methyl‐substituted aromatic carbocycles (tolyl, o‐xylyl or m‐xylyl) connected together through urea linkages. A crescent‐shaped conformational preference is encoded within these π‐conjugated urea‐linked oligomers based on intramolecular hydrogen bonding and steric interactions; the degree of curvature is tuned by the urea connectivity to the heterocycles and the aryl groups. NMR characterization of these foldamers confirms the intramolecular hydrogen‐bonded conformation expected (Z,E configuration of the urea bond) in both the pyridazyl and pyrimidyl foldamers in solution. An X‐ray crystal structure of the N3,N6‐diisobutylpyridazine‐4,6‐diamine–o‐tolyl urea‐linked foldamer ( 4 ) confirms the presence of N? H???N hydrogen bonds between the heterocyclic nitrogen atom and the free hydrogen of the urea linkage. Additionally, the tolyl methyl group interacts unfavourably with the urea carbonyl oxygen, thus destabilising the alternate planar conformation. 相似文献
114.
Dihydropteroate synthase (DHPS) is an alluring target for designing novel drug candidates to prevent infections caused by pathogenic Escherichia coli strains. Diaryl Sulfone (SO) compounds are found to inhibit DHPS competitively with respect to the substrate pABA (p-aminobenzoate). The extra aromatic ring of diaryl sulfone compounds found to stabilize them in highly flexible pABA binding loops. In this present study, a statistically significant 3D-QSAR model was developed using a data set of diaryl sulfone compounds. The favourable and unfavourable contributions of substitutions in sulfone compounds were illustrated by contour plot obtained from the developed 3D-QSAR model. Molecular docking calculations were performed to investigate the putative binding mode of diaryl sulfone compounds at the catalytic pocket. DFT calculations were carried out using SCF approach, B3LYP- 6-31 G (d) basis set to compute the HOMO, LUMO energies and their respective location at pABA binding pocket. Further, the developed model was validated by FEP (Free Energy Perturbation) calculations. The calculated relative free energy of binding between the highly potent and less potent sulfone compound was found to be −3.78 kcal/ mol which is comparable to the experimental value of −5.85 kcal/mol. A 10 ns molecular dynamics simulation of inhibitor and DHPS confirmed its stability at pABA catalytic site. Outcomes of the present work provide deeper insight in designing novel drug candidates for pathogenic Escherichia coli strains. 相似文献
115.
采用密度泛函理论(DFT)方法对二芳基氨(硼)-π-十二顶点碳硼烷三元化合物的结构及二阶非线性光学(NLO)性质进行计算.结果表明,化合物共轭桥长度及二芳基氨(硼)对化合物偶极矩的影响较小.随着分子共轭桥的增长,分子的电子空间范围R2增大,从而使极化率和第一超极化率增大.通过分析化合物的电子光谱和对应的分子轨道组成可知,分子中电荷转移主要发生在二芳基氨(硼)和π-桥之间,碳硼烷的贡献较少.二芳基氨和二芳基硼的供电子能力差异可以调节分子的二阶NLO响应. 相似文献
116.
Diaryl ethers have been prepared by a mild and efficient SNAr reaction by coupling of various phenols including that having a electron-withdrawing group with activated fluoroarenes using sonication in good to excellent yields at very low temperature (58 °C) under catalyst-free. 相似文献
117.
Brooks SJ García-Garrido SE Light ME Cole PA Gale PA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(12):3320-3329
The anion-binding properties of two similar hybrid amide/urea macrocycles containing either a 2,6-dicarboxamidophenyl or a 2,6-dicarboxamidopyridine group are compared. Significant differences in anion affinity and mode of interaction with anions are attributed to the presence of intramolecular hydrogen bonds in the pyridine system. In fact, remarkably, the phenyl macrocycle undergoes amide hydrolysis under neutral conditions in DMSO/water. The anion binding abilities of the receptors are compared to those of acyclic analogues of the macrocycles that show that the phenyl receptor behaves in a similar fashion to acyclic urea-containing receptors (i.e., showing little selectivity amongst oxo anions), whilst the pyridine-containing receptor shows a high affinity and selectivity for carboxylates. 相似文献
118.
119.
偶氮化合物可用作非线性光学材料、激光盘信息存贮材料和现代科技中的油溶性染料[1].传统偶氮化合物的制备有重氮盐偶合和取代肼氧化等许多方法[2~4],其偶氮基两端一般联有烃基或芳环,而联有羰基的偶氮类化合物用通常方法难以制备.本文首次用N-溴代丁二酰亚... 相似文献
120.
Shur等[1]曾对若干金属有机络合物如Cp2TiAr2的固氮作用进行了早朗研究。 相似文献