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排序方式: 共有229条查询结果,搜索用时 31 毫秒
111.
112.
Güler Narin Çisem Bulut Albayrak Semra Ülkü 《Journal of Sol-Gel Science and Technology》2014,69(1):214-230
In the present study, potential application of the local clinoptilolite-rich natural zeolite in formulation of antibacterial hydrogels was investigated. The zeolite powder exchanged with cobalt(II) ions was used in preparation of the zeolite/poly(vinyl alcohol) hydrogel films in different amounts. The films were physically crosslinked by the freezing-thawing method and characterized for their crystallinity, surface and cross sectional morphology, chemical composition, thermal behaviour, mechanical properties, swelling and dissolution behaviours, and antibacterial activities against a Gram-negative bacteria. The films with 0.48 wt% and higher cobalt-exchanged zeolite contents showed antibacterial activity. Addition of the zeolite powder in the formulations did not cause significant changes in the other properties of the films. 相似文献
113.
FT-IR and FT-Raman spectra of 1-cyclopropylpiperazine (1cppp) are experimentally examined in the range 4000-200 cm?1. The optimized geometric parameters, conformational equilibria, normal mode frequencies and corresponding vibrational assignments of 1cppp C7H14N2 are theoretically examined by means of B3LYP hybrid density functional theory (DFT) with the 6–31++G(d,p) basis set. Based on the potential energy distribution (PED) reliable vibrational assignments are made and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of 1cppp are predicted. Calculations are performed for four different conformations in two point groups of 1cppp in the gas phase. A comparison between the experimental and theoretical results indicates that the B3LYP method is able to provide satisfactory results for the prediction of vibrational frequencies, structural parameters, and assignments. Furthermore, the C s (equatorial-equatorial) point group is found as the most stable conformer of 1cppp. 相似文献
114.
We present a novel perfusion-based microfluidic platform for label-free drug toxicity screening which can single out non-lethal morphological changes from cellular death using electrical impedance spectroscopy. Minor cellular changes such as cell-cell contacts and major cell injury were identified via impedance phase angle analysis and follow-up of impedance magnitude at different frequencies. Having exposed HepG2/C3A cells to acetaminophen (AP), we showed that continuous drug perfusion caused a time and concentration-dependent impedance decrease. Moreover, perfusion of repeated doses revealed altered dielectric properties of the cell culture after recovery from AP exposure. This study highlights the possibility to sense cellular changes long before cellular death takes place, pointing out the remarkable sensitivity advantage of this technique over standard endpoint viability tests and its interest for toxicology. 相似文献
115.
One-step synthesis of hierarchical zeolite beta via network formation of uniform nanocrystals 总被引:1,自引:0,他引:1
Möller K Yilmaz B Jacubinas RM Müller U Bein T 《Journal of the American Chemical Society》2011,133(14):5284-5295
A hierarchical mesoporous network of zeolite beta with very high micropore as well as mesopore volume was synthesized without the need of a porogen at near 100% yield in the form of easily retrievable micrometer-sized particles. This was achieved by a dense-gel synthesis utilizing steam-assisted conversion (SAC) to induce a burst of nucleation. During the first phase of the synthesis, individual, evenly sized zeolite beta nanoparticles are formed that subsequently condense into a porous network displaying uniform mesopores. The final product consists of hierarchical self-sustaining macroscopic zeolite aggregates assembled from 20 nm crystalline domains of zeolite beta. The small size of the zeolite crystals in the resulting materials gives rise to mesopores with dominant pore sizes of about 13 nm. Large surface areas between 630 and 750 m(2)/g and total pore volumes up to 0.9 mL/g were obtained without sacrificing the microporosity (usually larger than 0.20 mL/g). Crystallization conditions were optimized for different Si/Al ratios between 10 and 33. A complete conversion into hierarchical zeolite beta was achieved in only a few hours at 170-180 °C if the amount of water present during the steam-assisted conversion was adequately adjusted. This dense gel steam conversion process proves to be a highly efficient strategy for fabricating hierarchical zeolite beta networks in a single step. 相似文献
116.
We present the structural and dynamic nature of water ultraconfined in the quasi-two-dimensional nanopores of the highly disordered calcium-silicate-hydrate (C-S-H), the major binding phase in cement. Our approach is based on classical molecular simulations. We demonstrate that the C-S-H nanopore space is hydrophilic, particularly because of the nonbridging oxygen atoms on the disordered silicate chains which serve as hydrogen-bond acceptor sites, directionally orienting the hydrogen atoms of the interfacial water molecules toward the calcium-silicate layers. The water in this interlayer space adopts a unique multirange structure: a distorted tetrahedral coordination at short range up to 2.7 ?, a disordered structure similar to that of dense fluids and supercooled phases at intermediate range up to 4.2 ?, and persisting spatial correlations through dipole-dipole interactions up to 10 ?. A three-stage dynamics governs the mean square displacement (MSD) of water molecules, with a clear cage stage characteristic of the dynamics in supercooled liquids and glasses, consistent with its intermediate-range structure identified here. At the intermediate time scales corresponding to the β-relaxation of glassy materials, coincident with the cage stage in MSD, the non-Gaussian parameter indicates a significant heterogeneity in the translational dynamics. This dynamic heterogeneity is induced primarily because of the heterogeneity in the distribution of hydrogen bond strengths. The strongly attractive interactions of water molecules with the calcium silicate walls serve to constrain their motion. Our findings have important implications on describing the cohesion and mechanical behavior of cement from its setting to its aging. 相似文献
117.
In this study HCl generation of polyvinyl (chloride) (PVC)/SiO2 composites during its combustion was investigated. SiO2 with different particle sizes were used as HCl absorbers and their HCl uptake ability results were compared to that of CaCO3. It was found that the amount of released HCl gas during PVC combustion decreased in the presence of SiO2. The HCl uptake ability of SiO2 improved with decreasing of its particle size. Although thermogravimetric analysis (TGA) results showed that SiO2 particles decreased the first thermal degradation temperature (T onset) of PVC by initiating dehydrochlorination of PVC at lower temperatures, SiO2 particles had more effective HCl uptaking ability than that of CaCO3. Scanning electron microscopy (SEM) micrographs showed that some aggregates whose size was less than 100 nm were formed when Si-25 nm was used as filler. When SiO2 with micron size was added to PVC as filler, more uniform and better distribution of the SiO2 on the surface was observed. 相似文献
118.
M. Ablikim M. N. Achasov X. C. Ai O. Albayrak M. Albecht D. J. Ambrose A. Amoroso 《中国物理C(英文版)》2016,40(11):113001-113001
By analyzing 2.93 fb-1 data collected at the center-of-mass energy √s=3.773 GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay D+→K0e+ve to be B(D+→K0e+ve)=(8.59±0.14±0.21)% using K0→KS0→π0π0, where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties.. 相似文献
119.
Bar Tercan Tuncer Hkelek Selen Bilge Bilgehan
zgü Zeynel Kl 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(6):o381-o383
The title compound, C15H16Cl4N5O2P3, is a cyclophosphazenic lariat (PNP‐pivot) ether with a spiro‐cyclic 12‐membered macrocyclic ligand containing two ether O and two N atoms; the phosphazene ring is nearly planar. In the macrocyclic ring, there is a four‐center (trifurcate) N—H⋯O/N—H⋯N hydrogen bond. The relative inner‐hole size of the macrocycle is estimated as approximately 0.95 Å. 相似文献
120.
E. Albayrak 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):491-496
The thermal entanglement of a two-qubit anisotropic Heisenberg XXZ
chain with Dzyaloshinskii-Moriya (DM) interaction in an
inhomogeneous magnetic field was studied in detail. The effects of
the DM parameter, external magnetic field (B), a parameter b
which controls the inhomogeneity of B and the bilinear
interaction parameters Jx = Jy ≠ Jz (the anisotropic case) on
the concurrence (C) was formulated and studied in detail. The
behaviors of the concurrences for the cases between (J = Jz = 1) and
(J = -1,Jz = 1) and, (J = Jz = -1) and (J = 1,Jz = -1) at the ground
state and at the thermal equilibrium are exactly the same. It was
found that for the antiferromagnetic (AFM) case the entanglements
persist to higher temperatures in comparison with the ferromagnetic
(FM) case. In addition, the AFM case presents a special point at
which the nonzero concurrences are all equal at some special
temperatures. The further properties will be given in the text. 相似文献