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排序方式: 共有157条查询结果,搜索用时 31 毫秒
21.
We performed molecular simulations to analyze the thermodynamics of methane solvation in dimethyl sulfoxide (DMSO)/water mixtures (298 K, 1 atm). Two contributions to the interaction thermodynamics are studied separately: (i) the introduction of solute-solvent interactions (primary contribution) and (ii) the solute-induced disruption of cohesive solvent-solvent interactions (secondary contribution). The energy and entropy changes of the secondary contribution always exactly cancel in the free energy (energy-entropy compensation), hence only the primary contribution is important for understanding changes of the free energy. We analyze the physical significance of the solute-solvent energy and solute-solvent entropy associated with the primary contribution and discuss how to obtain these quantities from experiments combining solvation thermodynamic and solvent equation of state data. We show that the secondary contribution dominates changes in the methane solvation entropy and enthalpy: below 30 mol % DMSO in the mixture, methane, because of more favorable dispersion interactions with DMSO molecules, preferentially attracts DMSO molecules, which, in response, release water molecules into the bulk, causing an increase in the entropy. This large energy-entropy compensating process easily causes a confusion in the cause for and the effect of preferred methane-DMSO interactions. Methane-DMSO dispersion interactions are the cause, and the entropy change is the effect. Procedures that infer thermodynamic driving forces from analyses of the solvation entropies and enthalpies should therefore be used with caution. 相似文献
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The purpose of this article is to introduce an implicit iteration process for approximating common fixed points of three finite families nonexpansive mappings and to prove weak and strong convergence theorems in uniformly convex Banach spaces. 相似文献
24.
Serhan Yamacli Caner Ozdemir Ali Akdagli 《International Journal of Infrared and Millimeter Waves》2008,29(2):207-216
This paper presents a simple method for determining the dielectric constant of microwave PCB substrates. In the presented
method, a bandpass microstrip filter designed on the PCB substrate with a user-predicted dielectric constant value is implemented
for a given center frequency. The simulation results of the designed bandpass filter are obtained by the help of microwave
design software; XFDTD?. Experimental results regarding the filter frequency characteristic are accomplished by means of a
vector network analyzer. The simulation results of the designed filter are modified to overlap with the experimental ones
by varying the dielectric constant value. When the simulation and experimental results are overlapped, the value of dielectric
constant is accurately selected. In order to illustrate the validity of proposed method, the dielectric constant values of
flame resistant-4 (FR4) substrates are acquired at IEEE 802.11b/g and IEEE 802.11a wireless local area network (WLAN) application
frequencies. The results obtained by using the presented method agree with the previous studies in the literature. 相似文献
25.
Ece Tugba Saka 《Journal of inclusion phenomena and macrocyclic chemistry》2018,90(1-2):61-73
The host–guest inclusion complex of meta-cresol (m-cresol, liquid at room temperature, guest molecule) is synthesized with β-cyclodextrin (β-CD, host molecule). The inclusion complex is characterized by various techniques like nuclear magnetic resonance, powder X-ray diffraction, field emission scanning electron microscopy and spectroscopic (steady state as well as time-resolved) techniques. To the best of our knowledge, no literature data is available on the photophysical properties (especially fluorescence upon photoexcitation) of m-cresol in liquid media till date. Our spectroscopic studies exhibit some interesting photophysical properties of m-cresol and its inclusion complex with β-CD in different liquid media. The present work is important in view of the various potential applications of m-cresol in science, technology and medicine. 相似文献
26.
Hakan Arslan Donald VanDerveer Ismail Ozdemir Bekir Cetinkaya Serpil Demir 《Journal of chemical crystallography》2005,35(6):491-495
Two imidazolidin ruthenium complexes, [RuCl2{[N-(2,4,6-trimethyl-benzyl)-N-(n-butyl)]-imidazolidin-2-ylidene}], 1, and [RuCl2{[N-(2,4,6-trimethyl-benzyl)-N-(2-methoxyethyl)]-imidazolidin-2-ylidene}], 2, have been synthesised and their crystal structures have been determined from single crystal X-ray diffraction data. Compound 1 is monoclinic, of space group C2/c with a = 18.466(4) Å, b = 14.816(3) Å, c = 15.413(3) Å, β = 118.067(2)∘, and V = 3720.9(12) Å3 with Z = 8 for dcalc = 1.536 g/cm3. Compound 2 is monoclinic, of space group P21/c with a = 8.1800(5) Å, b = 14.344(8) Å, c = 14.809(9), β = 91.604(10)∘, and V = 1736.7(18) Å3 with Z = 4 for dcalc = 1.653 g/cm3. In each complex the ligand functions as an arene and carbene, occupying four coordination sites. The two chlorines in each compound complete a distorted octahedron. 相似文献
27.
Ozmen UO Olgun G 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(3):641-645
Prophane sulfonic acid hydrazide (psh: CH(3)CH(2)CH(2)SO(2)NHNH(2)) derivatives as salicylaldehydeprophanesulfonylhydrazone (salpsh), 5-methylsalicylaldehydeprophanesulfonylhydrazone (5-msalpsh), 2-hydroxyacetophenoneprophanesulfonylhydrazone (afpsh), 5-methyl-2-hydroxyacetophenoneprophanesulfonylhydrazone (5-mafpsh) and their Ni(II) complexes have been synthesized. The structure of these compounds has been investigated by using elemental analysis, FTIR, (1)H NMR, LC/MS, UV-vis spectrophotometric method, magnetic susceptibility and conductivity measurements. The complexes were found to have general compositions [NiL2]. Square-planer structures are proposed for the Ni(II) complexes on the basis of magnetic evidence, electronic spectra and TGA data. Bacterial activities of sulfonyl hydrazone compounds were studied against gram-positive bacteria: Staphylococcus aureus, Bacillus subtilis, Bacillus magaterium and gram-negative bacteria: Salmonella enteritidis, Escherichia coli by using minimum inhibitory concentrations (MICs) method. 相似文献
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29.
Remote‐Controlled Release of Singlet Oxygen by the Plasmonic Heating of Endoperoxide‐Modified Gold Nanorods: Towards a Paradigm Change in Photodynamic Therapy
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Dr. Safacan Kolemen Dr. Tugba Ozdemir Dayoung Lee Gyoung Mi Kim Tugce Karatas Prof. Juyoung Yoon Prof. Engin U. Akkaya 《Angewandte Chemie (International ed. in English)》2016,55(11):3606-3610
The photodynamic therapy of cancer is contingent upon the sustained generation of singlet oxygen in the tumor region. However, tumors of the most metastatic cancer types develop a region of severe hypoxia, which puts them beyond the reach of most therapeutic protocols. More troublesome, photodynamic action generates acute hypoxia as the process itself diminishes cellular oxygen reserves, which makes it a self‐limiting method. Herein, we describe a new concept that could eventually lead to a change in the 100 year old paradigm of photodynamic therapy and potentially offer solutions to some of the lingering problems. When gold nanorods with tethered endoperoxides are irradiated at 808 nm, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. We demonstrate that the amount of singlet oxygen produced in this way is sufficient for triggering apoptosis in cell cultures. 相似文献
30.
C. Yohannan Panicker Hema Tresa Varghese Asha Raj K. Raju Tugba Ertan-Bolelli Ilkay Yildiz Ozlem Temiz-Arpaci Carlos M. Granadeiro Helena I.S. Nogueira 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(1):132-139
The FT-IR and FT-Raman spectra of 2-phenoxymethylbenzothiazole were recorded and analyzed. The surface enhanced Raman scattering (SERS) spectrum was recorded in a silver colloid. The vibrational wavenumbers of the compound have been computed using the Hartree–Fock/6-31G* basis and compared with the experimental values. The appearance of the Ag–O stretching mode at 237 cm−1 in the SERS spectrum along with theoretically calculated atomic charge density, leads us to suggest that the molecule is adsorbed through the oxygen atom with the molecular plane tilted on the colloidal silver surface. The direction of charge transfer contribution to SERS has been discussed from the frontier orbital theory. 相似文献