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排序方式: 共有193条查询结果,搜索用时 46 毫秒
31.
Ioannis Papanastasiou Andrew Tsotinis George B. Foscolos S. Radhika Prathalingam John M. Kelly 《Journal of heterocyclic chemistry》2008,45(5):1401-1406
32.
Self‐Assembly of “Chalcone” Type Push‐Pull Dye Molecules into Organic Single Crystalline Microribbons and Rigid Microrods for Vis/NIR Range Photonic Cavity Applications
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Radhika Vattikunta Dasari Venkatakrishnarao Prof. Dr. Mahamad Ahamad Mohiddon Prof. Dr. Rajadurai Chandrasekar 《Chemphyschem》2016,17(21):3435-3441
A novel supramolecular fluorescent donor–acceptor type dye molecule, (2E,4E)‐1‐(2‐hydroxyphenyl)‐5‐(pyren‐1‐yl)penta‐2,4‐dien‐1‐one (HPPD) self‐assembles in a mixture of ethanol/chloroform through intermolecular π–π stacking (distance ca. 3.384 Å) to form J‐aggregated single‐crystalline microribbons displaying Fabry–Pèrot (F‐P) type visible‐range optical resonance. The corresponding borondifluoride dye (HPPD‐BF), with a reduced HOMO–LUMO gap, self‐assembles into crystalline microrods acting as an F‐P type resonator in the near‐infrared (NIR) range. 相似文献
33.
Rogers JE Slagle JE McLean DG Sutherland RL Brant MC Heinrichs J Jakubiak R Kannan R Tan LS Fleitz PA 《The journal of physical chemistry. A》2007,111(10):1899-1906
A comprehensive photophysical study of the linear and nonlinear absorption properties has been carried out on two series of two-photon absorbing dyes to gain insight into how structure-property relationships influence observed nonlinear absorption. The materials studied consist of an electron accepting benzothiazole group connected to an electron donating diphenylamine via a fluorene bridging group. Two series differ from each other by the addition of one phenyl group and for each series one-arm (dipolar, AF240 and AF270), two-arm (quadrupolar, AF287 and AF295), and three-arm (octupolar, AF350 and AF380) versions were studied. Overall the AF240 series exhibits higher intrinsic two-photon absorption (TPA) cross-sections than the AF270 series as well as enhanced nanosecond nonlinear absorption, with an increase with number of branches. The enhanced nanosecond nonlinearity is understood by taking into account the contribution from the singlet and triplet excited states and was verified by a two-photon assisted excited-state absorption model that satisfactorily predicts the nonlinear absorption of the chromophores. 相似文献
34.
Closed form solutions for a simultaneously AM and high-harmonic FM mode locked laser system is presented. Analytical expressions
for the pulsewidth and pulsewidth-bandwidth products are derived in terms of the system parameters. The analysis predicts
production of 17 ps duration pulses in a Nd:YAG laser mode locked with AM and FM modulators driven at 80 MHz and 1.76 GHz
for 1 W modulator input power. The predicted values of the pulsewidth-bandwidth product lie between the values corresponding
to the pure AM and FM mode locking values. 相似文献
35.
Pervanadyl (VO2+) complexes with N‐(aroyl)‐N′‐(picolinylidene)hydrazines (HL = Hpabh, Hpath and Hpadh; H stands for the dissociable amide hydrogen) are described. The Schiff bases were obtained by condensation of 2‐pyridine‐carboxaldehyde with benzhydrazide (Hpabh), 4‐methylbenzhydrazide (Hpath) and 4‐dimethylaminobenzhydrazide (Hpadh), respectively. The reaction of [VO(acac)2] and HL in acetonitrile in air affords the complexes of general formula [VO2L]. The diamagnetic nature and EPR silence confirm the +5 oxidation state of vanadium in these complexes. Infrared spectra of the complexes are consistent with the enolate form of the coordinated ligands. Electronic spectra show charge transfer bands in the range 486–233 nm. The complexes are redox active and display an irreversible reduction (–0.64 to –0.72 V vs. Ag/AgCl). The crystal structures of all the complexes have been determined. In each complex, the metal centre is in a distorted trigonal‐bipyramidal N2O3 coordination sphere formed by the pyridine‐N, the imine‐N and the deprotonated amide‐O donor L– and two oxo groups. The planar ligand satisfies one equatorial and two axial positions. The other two equatorial positions are occupied by the two oxo groups. In the solid state, the molecules of each of the three complexes form a chain‐like arrangement via the azomethine‐H…oxo interactions. Interchain weak π‐π interactions lead to two dimensional networks for [VO2(pabh)] and [VO2(path)]. On the other hand, [VO2(padh)] forms a two‐dimensional network through interchain N‐methyl‐H…oxo interactions. 相似文献
36.
37.
G. Vasuki V. Parthasarathi K. Ramamurthi D. P. Jindal S. Dubey 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(9):1062-1063
The title compound, C25H31NO2·H2O, has the outer two six‐membered rings in chair conformations, while the central ring is in an 8β,9α‐half‐chair conformation. The five‐membered ring adopts a 13,14‐half‐chair conformation. The pyridylmethylene moiety has an E configuration with respect to the carbonyl group at position 17. The structure is stabilized by intermolecular O—H?N and O—H?O hydrogen bonds. 相似文献
38.
For any two primes, , such that< and divides–1, it is shown that there exists a non-Moufang Bol loop of order
2 which is isomorphic to each of its loop isotopes. 相似文献
39.
40.
Modeling the mechanism involved during the sorption of methylene blue onto fly ash 总被引:15,自引:0,他引:15
Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using fly ash as an adsorbent. Operating variables studied were initial dye concentration, fly ash mass, pH, and contact time. Maximum color removal was observed at a basic pH of 8. Equilibrium data were represented well by a Langmuir isotherm equation with a monolayer sorption capacity of 5.718 mg/g. Sorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics. Rate constants at different initial concentrations were estimated. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter D(i) values were estimated at different initial concentrations and the average value was determined to be 2.063 x 10(-9)cm2/s. Analysis of sorption data using a Boyd plot confirms the particle diffusion as the rate-limiting step for the dye concentration ranges studied in the present investigation (20 to 60 mg/L). 相似文献