首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   23篇
  免费   1篇
化学   15篇
力学   2篇
数学   3篇
物理学   4篇
  2022年   1篇
  2020年   2篇
  2018年   1篇
  2016年   3篇
  2015年   1篇
  2014年   3篇
  2013年   1篇
  2011年   2篇
  2010年   1篇
  2009年   2篇
  2008年   1篇
  2006年   2篇
  2004年   1篇
  2002年   1篇
  1999年   1篇
  1989年   1篇
排序方式: 共有24条查询结果,搜索用时 15 毫秒
1.
The synthesis of alkyne functionalized bipyridine ruthenium complexes are reported. The improved synthetic approach through application of stable protecting groups prevents formation of possible side products while facilitating purification. By applying copper-catalysed azide-alkyne cycloaddition reactions (CuAAC) pyrene units with flexible alkyl linkers are introduced at the periphery of the complex, opening up various applications including surface immobilization and DNA intercalation. All complexes are characterized structurally as well as photophysically, especially regarding the influence of the introduced alkyne and triazolyl substituents on their photophysical behavior.  相似文献   
2.
3.
The full and reduced shell model calculations have been carried out for the light odd-even ^105Sb and ^107Sb isotopes. The model space has been chosen as 1d5/2, 0g7/2, 1d3/2, 2s1/2, and 0h11/2 for the full calculations and excluded 0h11/2 for the reduced calculations. The reduced shell model calculations of ^105Sb and ^107Sb isotopes are presented for the first time. We obtain the energy spectra for the ^105Sb and ^107Sb isotopes in the full and reduced model space by using CD-Bonn two-body effective nucleon-nucleon interaction. The resulting energy spectra are compared to the experimental results to understand the effect of the 0h11/2 level on the shell model calculations. We draw conclusions about the right model space in the shell model calculations for the isotopes around the N =Z= 50 region of the periodic table.  相似文献   
4.
H. Yücel  H. Dikmen 《Talanta》2009,78(2):410-417
In this paper, the known multigroup γ-ray analysis method for uranium (MGAU) as one of the non-destructive γ-ray spectrometry methods has been applied to certified reference nuclear materials (depleted, natural and enriched uranium) containing 235U isotope in the range of 0.32-4.51% atom 235U. Its analysis gives incorrect results for the low component 235U in depleted and natural uranium samples where the build-up of the decay products begins to interfere with the analysis. The results reveal that the build-up of decay products seems to be significant and thus the algorithms for the presence of decay products should be improved to resulting in the correct enrichment value. For instance, for the case of 235U analysis in depleted uranium or natural ore samples, self-induced X-rays such as 94.6 keV and 98.4 keV lying in UXKα spectral region used by MGAU can be excluded from the calculation. Because the significant increases have been observed in the intensities of uranium self-induced X-rays due to γ-ray emissions with above 100 keV energy arising from decay products of 238U and 235U and these parents. Instead, the use of calibration curve to be made between the intensity ratios of self-fluorescence X-rays to 92* keV γ-ray and the certified 235U abundances is suggested for the determination of 235U when higher amounts of decay products are detected in the γ-ray spectrum acquired for the MGAU analysis.  相似文献   
5.
New mixed-valent, Ni1+/Ni2+, metastable nickelate, La3Ni2O6, was synthesized by low-temperature reduction of La3Ni2O7 with CaH2. The crystal structure of La3Ni2O6 (space group: I4/mmm, a = 3.9686(1) A and c = 19.3154(6) A) was determined from powder neutron diffraction data by Rietveld analysis. The structure can be described as an intergrowth of LaO2 fluorite and double infinite layer (LaNiO2)2 blocks and represents the n = 2 homologue of the T'-type series Lan+1NinO2n+2. Such double T'-type structural arrangement has never been observed before. The 3d9/3d8 electronic configuration of Ni1+/Ni2+ and the presence of NiO2 infinite layers resemble electronic and structural features of the superconducting cuprates. X-ray absorption spectroscopy supports the 1+/2+ oxidation state and planar coordination of Ni in agreement with the structure determination.  相似文献   
6.
The adsorption of a cationic dye, Basic Blue 16 (BB16), by montmorillonitic clay was studied in detail. Changes in the molecular structure during adsorption were analyzed by FTIR spectroscopy. BB16 adsorption onto the clay mainly results from hydrogen bonding between OH and NH2 groups of dye molecules and OH groups of clay and electrostatic interaction between the negatively charged clay surface and cationic dye. The montmorillonitic clay dose had an inverse effect on the adsorption performance, while the highest dye removal was 305 mg/g at pH 3.6. An increase in temperature and dye concentration positively enhanced the adsorption capacity of the montmorillonitic clay. Temperature had no effect on the adsorption at a dye concentration less than 500 mg/L, while dye adsorption was positively enhanced at elevated dye concentrations. Three-parameter equations provided higher better fitting than two-parameter equations while the Freundlich model had the highest correlation coefficient and the lowest error values with experimental data. The BB16 adsorption was well followed by pseudo-second order model and the rate of adsorption process was controlled by surface and intraparticle diffusion. Thermodynamic evaluations revealed that the adsorption process was spontaneous and endothermic, while the randomness increased during adsorption. Experimental results indicate that montmorillonitic clay from Eskisehir is a promising adsorbent for the removal of cationic dye molecules from aqueous solutions.  相似文献   
7.
In this study, a bentonite sample from Ünye, Turkey was treated with various HCl solutions (0.1, 1.0 and 5.0 M) at 90 °C during 3 and 6 h. X-ray diffraction (XRD), X-ray fluorescence (XRF), differential thermal analysis (DTA), thermogravimetric analysis (TG), Fourier transform infrared (FT-IR), magic angle spinning nuclear magnetic resonance (29Si and 27Al MAS NMR) and surface area measurement methods were employed in order to investigate the structural and thermal changes occurring as a result of the acid activation. The data for the adsorption of C2H4 obtained at 273 K and pressures up to 100 kPa correlated with structural properties of the acid treated bentonite samples. With the increase of both concentration of acid solution and treatment time, the specific surface area values and the retentions of C2H4 gas of bentonite samples increased. Bentonite treated with 5.0 M HCl for 6 h adsorbed C2H4 most effectively.  相似文献   
8.
We have performed two kinds of non-linear fitting procedures to the single-particle energies in the sdgh major shell to obtain better shell model results. The low-lying energy eigenvalues of the light Sn isotopes with A = 103- 110 in the sdgh-shell are calculated in the framework of the nuclear shell model by using CD-Bonn two-body effective nucleonnucleon interaction. The obtained energy eigenvalues are fitted to the corresponding experimental values by using two different non-linear fitting procedures, i.e., downhill simplex method and clonal selection method. The unknown single-particle energies of the states 2s1/2, 1d3/2, and 0h11/2are used in the fitting methods to obtain better spectra of the104,106,108,110 Sn isotopes. We compare the energy spectra of the104,106,108,110 Sn and103,105,107,109 Sn isotopes with/without a nonlinear fit to the experimental results.  相似文献   
9.
FT-IR and Raman spectra of methyl(5-[2-thienylcarbonyl]-1H-benzimidazol-2-yl (nocodazole) are experimentally examined in the region of 4000–400 cm?1. The optimized geometric parameters, conformational equilibria, normal mode frequencies, and corresponding vibrational assignments of nocodazole (C14H11N3O3S) calculated by means of the B3LYP hybrid density functional theory (DFT) method using the 6-31++G(d,p) basis set. Vibrational assignments are made based on the total energy distribution (TED) and the thermodynamic functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of nocodazole are calculated. Calculations are employed for four energetically possible conformers of nocodazole (N1, N2, N3, and N4) in the gas phase. A comparison between the experimental and theoretical results indicates that the B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers if calculated values are scaled properly and the structural parameters.  相似文献   
10.
A novel, ecofriendly, and easy extraction and preconcentration method named as vortex‐assisted spraying‐based fine droplet formation liquid‐phase microextraction was proposed for the determination of prochloraz at trace levels in orange juice samples by gas chromatography–mass spectrometry (GC‐MS). In this novel system, extraction solvent is dispersed by the help of spraying apparatus instead of dispersive solvent. Various parameters of the method were carefully optimized to increase signal‐to‐noise ratio of the analyte. Under the optimum chromatographic and extraction conditions, limit of detection and limit of quantification were calculated as 3.2 and 10.8 μg/kg, respectively. Moreover, enhancement in quantification power for the GC‐MS system was determined as 372 folds based on LOQ comparison. Relative recovery results for orange juice samples were found to be between 95.0–107.7% by utilizing matrix matching calibration. Furthermore, the developed method may be used to efficiently and simply extract other organic compounds for their determinations in several matrices.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号