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71.
Geometries and binding energies are predicted at B3LYP/6-311+G* level for the adenine–BX3 (X=F,Cl) systems and four conformers with no imaginary frequencies have been obtained for both adenine–BF3 and adenine–BCl3, respectively, and single energy calculations using much larger basis sets (6-311+G(2df,p)) and aug-cc-pVDZ were carried out as well. The most stable conformer is BF3 or BCl3 connected to N3 of adenine and with the stabilization energy of 22.55 or 20.59 kcal/mol at B3LYP/6-311+G* level (BSSE corrected). The analyses for the combining interaction between BX3 and adenine with natural bond orbital method (NBO) and the atom-in-molecules theory (AIM) have been performed. The results indicate that all the conformers were formed with σ–p type interactions between adenine and BX3, in which pyridine-type nitrogen or nitrogen atom of amino group offers its lone pair electron to the empty p orbital of boron atom and the concomitances of charge transference from adenine to BX3 were occurred. Frequency analysis suggested that the stretching vibration of BX3 underwent a red shift in complexes. Adenine–BF3 complex was more stable than adenine–BCl3 although the distance of B–N is shorter in the later. 相似文献
72.
73.
LetK be a class of spaces which are eigher a pseudo-opens-image of a metric space or ak-space having a compact-countable closedk-network. LetK′ be a class of spaces which are either a Fréchet space with a point-countablek-network or a point-G
δ
k-space having a compact-countablek-network. In this paper, we obtain some sufficient and necessary conditions that the products of finitely or countably many
spaces in the classK orK′ are ak-space. The main results are that
Project supported by the Mathematical Tianyuan Foundation of China 相似文献
Theorem A | If X, Y∈K. Then X x Y is a k-space if and only if (X, Y) has the Tanaka's condition. |
Theorem B | The following are equivalent: |
(a) | BF(ω 2)is false. |
(b) | For each X, Y ∈ K′, X x Y is a k-space if and only if (X,Y) has the Tanaka's condition. |
74.
UV光谱研究[Cp-Fe-Cp]BF4和[Cp-Fe-Naph]BF4的光解动力学及机理 总被引:3,自引:0,他引:3
本文测定了两种新型阳离子光聚合引发剂二茂铁四氟硼酸盐([Cp-Fe-Cp]BF4)和环戊二烯基-铁-萘四氟硼酸盐([Cp-Fe-Naph]BF4)在二氯甲烷和环氧氯丙烷中的紫外-可见吸收光谱,研究了紫外光照射对吸收光谱的影响,通过实时紫外-可见吸收光谱分析,研究了两种光引发剂在环氧氯丙烷中的光解动力学。发现二者的吸收光谱随光照时间的变化规律一致,而且光解反应均为一级反应,速率常数分别为0.72和0.65min^-1,从而提出了二茂铁四氟硼酸盐的光引发机理。 相似文献
75.
76.
Karol Jackowski Włodzimierz Makulski Anna Szyprowska Andrej Antušek Michał Jaszuński 《Magnetic resonance in chemistry : MRC》2009,47(10):857-861
The 1J(11B19F) spin–spin coupling of gaseous BF3 was observed in 11B NMR spectra as a function of density in a wide range of temperatures. Following the extrapolation of the measured values to the zero‐density limit, the coupling constant free from intermolecular effects 1J0(11B19F) was obtained for each temperature. In contrast to previous investigations, the final results indicate a nonlinear dependence of 1J0(11B19F) on temperature. In the corresponding ab initio calculations of spin–spin coupling constants performed at the coupled cluster singles and doubles (CCSD) level to obtain a reliable result for this coupling constant we had to take into account large vibrational corrections. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
77.
Two types of novel BF2 complexes are readily obtained by the reaction of BF3OEt with 3-(2-oxo-2-arylethylidene)-3,4-dihydro-1H-quinoxalin-2-ones or 3-(2-oxo-2-arylethylidene)-3,4-dihydrobenzo[1,4]oxazin-2-ones, respectively in refluxing acetic acid/toluene solvent mixture. The complexes are confirmed by elemental analysis, FT-IR, 1H, 13C, 11B, 19F NMR and one of them is executed its X-ray crystallographic study. The outstanding photophysical properties of these complexes are determined by UV–vis absorption and fluorescence emission spectroscopy. 相似文献
78.
79.
Qin He Jing Yang Xiang-jun Meng 《化学物理学报(中文版)》2009,(5):517-522
The hydrogen bonding character between the BF4- and glycine was theoretically studied at the level of B3LYP/6-31+G^*, single point energies were performed at the level of B3LYP/6-311++G^**. The relevant geometrical characteristics, energy properties, as well as the characters of the intramolecular hydrogen bonds have been studied. Atoms in molecule theory topological analysis indicated the (3,-1) critical points for hydrogen bonds. In addition, the electron density and Laplacian were in the range suggested for the hydrogen bonds. Especially, the changes of atomic charge, hydrogen upon hydrogen bonds formation dipole moment, enegry as well as volume of the were systemitically discussed. 相似文献
80.
以钛酸丁酯为前驱物,在离子液体([Bmim]BF4)中采用微波辐射加热法合成了TiO2/聚苯乙烯(PS)复合材料,用TG、XRD、IR、XPS和SEM对复合材料进行了表征.通过测试复合材料在乙酸乙酯中的吸光度及对甲基橙溶液的降解率,考察了离子液体体积、微波功率、反应温度、反应时间等因素对复合材料分散性和光催化活性的影响.结果表明:微波助离子液体介质中制备TiO2/PS复合材料的最佳条件是:钛酸丁酯与ST体积比为3.4∶1.1,[Bmim]BF42.0mL,微波功率700W,反应温度50℃,反应时间60min;在离子液体介质中使用微波辐射加热制备TiO2/PS复合材料,能够降低反应的温度,极大地缩短反应的时间;且制得的复合材料的亲油性能大大提高,在乙酸乙酯中具有较好的分散性,该复合材料不需要高温煅烧就具有较高的光催化活性(紫外光照射1.5h甲基橙降解率为96.2%). 相似文献