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61.
Aliakbar Dehno Khalaji Gholamhossein Grivani Samaneh Jalali Akerdi Helen Stoeckli-Evans Debasis Das 《Journal of chemical crystallography》2012,42(1):83-88
Abstract
Two zinc(II) complexes [ZnI2((2,3-MeO-ba)2en)] (1) and [ZnCl2((2,3-MeO-ba)2en)] (2), with the symmetrical bidentate Schiff-base ligand (2,3-MeO-ba)2en [N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane] have been synthesized and characterized by elemental analyses (CHN), FT-IR and 1H-NMR spectroscopy. The thermal behaviors of these complexes were studied using thermogravimetry in order to evaluate their thermal stability and thermal decomposition pathways. The crystal structure of [ZnI2((2,3-MeO-ba)2en)] (1) was determined from single-crystal X-ray diffraction. The coordination polyhedron about the zinc(II) center in the complex 1 is best described as a distorted tetrahedron. 相似文献62.
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Kinetics of the substitution reaction of solvent molecule in uranyl(VI) Schiff base complexes by tri‐n‐butylposphine as the entering nucleophile in acetonitrile at 10–40°C was studied spectrophotometrically. The second‐order rate constants for the substitution reaction of the solvent molecule were found to be (8.8 ± 0.5) × 10?3, (5.3 ± 0.2) × 10?3, (7.5 ± 0.3) × 10?3, (6.1 ± 0.3) × 10?3, (13.5 ± 1.6) × 10?3, (13.2 ± 0.9) × 10?3, (52.9 ± 0.2) × 10?3, and (88.1 ± 0.6) × 10?3 M?1 s?1 at 40°C for [UO2(Schiff base)(CH3CN)], where Schiff base = L1–L8, respectively. In a temperature dependence study, the activation parameters ΔH# and ΔS# for the reaction of uranyl complexes with PBu3 were determined. From the linear rate dependence on the concentration of PBu3, the span of k2 values and the large negative values of the activation entropy, an associative (A) mechanism is deduced for the solvent substitution. By comparing the second‐order rate constants k2, it was concluded that the steric and the electronic properties of the complexes were important for the rate of the reactions. 相似文献
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A simple graphical approach to predict local residue conformation using NMR chemical shifts and density functional theory 下载免费PDF全文
Hoora Shaghaghi Hossein Pasha Ebrahimi Fariba Fathi Niloufar Bahrami Panah Mehdi Jalali‐Heravi Mohsen Tafazzoli 《Journal of computational chemistry》2016,37(14):1296-1305
The dependency of amino acid chemical shifts on φ and ψ torsion angle is, independently, studied using a five‐residue fragment of ubiquitin and ONIOM(DFT:HF) approach. The variation of absolute deviation of 13Cα chemical shifts relative to φ dihedral angle is specifically dependent on secondary structure of protein not on amino acid type and fragment sequence. This dependency is observed neither on any of 13Cβ, and 1Hα chemical shifts nor on the variation of absolute deviation of 13Cα chemical shifts relative to ψ dihedral angle. The 13Cα absolute deviation chemical shifts (ADCC) plots are found as a suitable and simple tool to predict secondary structure of protein with no requirement of highly accurate calculations, priori knowledge of protein structure and structural refinement. Comparison of Full‐DFT and ONIOM(DFT:HF) approaches illustrates that the trend of 13Cα ADCC plots are independent of computational method but not of basis set valence shell type. © 2016 Wiley Periodicals, Inc. 相似文献
67.
Optimization of parameters in preparation of PCM microcapsules based on melamine formaldehyde through dispersion polymerization 总被引:1,自引:0,他引:1
Fahimeh Khakzad Zeinab Alinejad Abbas Rezaee Shirin-Abadi Maryam Ghasemi Ali Reza Mahdavian 《Colloid and polymer science》2014,292(2):355-368
Microencapsulated phase change materials have attracted special attention due to their wide applications in saving and releasing energy. Here, microencapsulation of hexadecane (HD) in melamine formaldehyde shell was carried out through in situ dispersion polymerization in the aqueous media. Some important parameters such as stabilizer type and amount, surfactant amount, homogenization conditions as the critical affective factors on final particle size, morphology, and thermal resistance of the microcapsules were investigated extensively. The obtained microcapsules were concurrently analyzed by SEM, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques. SEM images showed that the best stabilization was achieved by polyvinyl alcohol. Also, particle size, as an indication of surface area for heat transfer properties, showed a decrement by increasing stabilizer amount, surfactant amount, and homogenization speed. The amount of entrapped HD and efficiencies of microencapsulation were determined by DSC, and the reason for observing such changes were discussed in detail. Thermal stability of the microcapsules as an important property for their performance was investigated, too. The results illustrated that an improved thermal stability would be obtained by an efficient stabilization in the emulsification step. Also the highest thermal stability up to 388 °C was reached at homogenization speed of 6,000 rpm. Finally, the optimized conditions for desirable encapsulation were proposed in such systems. 相似文献
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69.
Elaheh K. Goharshadi Maryam Imani Rayhaneh Rahimi-Zarei Fahimeh Razghandi Maryam Abareshi Ali R. Berenji 《European Polymer Journal》2010,46(3):587-591
In this work, the excess thermodynamic properties, namely excess molar Gibbs energy, excess molar enthalpy, excess molar entropy, excess molar internal energy, and excess molar Helmholtz energy for four polymer mixtures and blends at different temperatures, pressures, and compositions have been calculated using the GMA equation of state. We have also calculated the activity coefficient for these polymeric mixtures using the GMA equation of state. The values of statistical parameters between experimental and calculated properties show the ability of this equation of state in reproducing and predicting the excess thermodynamic functions and activity coefficients for studied polymeric mixtures. 相似文献
70.
Aliakbar Dehno Khalaji Matthias Weil Gholamhossein Grivani Samaneh Jalali Akerdi 《Monatshefte für Chemie / Chemical Monthly》2010,103(2):539-543