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121.
The photoluminescence (PL) at ∼2.2-2.3 eV from Ge-based nanocrystalline materials is described in the literature as nanocrystal size-independent. We have observed visible luminescence from two different types of stain-etched Ge samples, one prepared after Sendova-Vassileva et al. (Thin Solid Films 255 (1995) 282) in a solution of H2O2:HF at 50:1 volume ratio, and the other in a solution of HF:H3PO4:H2O2 at 34:17:1 volume ratio. Energy dispersive X-ray analysis (EDX), Raman and FTIR spectroscopy, and the near edge X-ray absorption structure (XANES), indicate that the chemically etched Ge layers of the former type of samples are composed of non-stoichometric Ge oxides, i.e. GeOx (0<x<2), and free from any Ge nanoconstructions. It is also suggested from XANES that the latter type of chemically etched Ge samples comprise 8-9 nm nanocrystals of Ge, surface-covered with mainly oxygen. Photoluminescence occurred at ∼2.3 eV for all samples. The PL behavior of the latter type of chemically etched Ge on annealing in different chemical environments (air or H) allowed us to conclude that the PL from these materials, as well as that from those Ge-based nanocrystalline materials reported in the literature, is from GeOxs. 相似文献
122.
Erdal Ertas Turan Ozturk John. D. Wallis William H. Watson 《Journal of chemical crystallography》1998,28(5):409-412
The crystal structure of ethyl bis(2,4-dinitrophenyl)acetate, determined by room temperature X-ray diffraction, shows that this crowded molecule contains two short intramolecular interactions between nitro oxygen atoms and electron deficient carbon atoms. One mimics an early stage of the nucleophilic addition to a carbonyl group (O...C, 2.730 Å), and the other mimics an early stage of a Michael reaction (O...C, 2.854 Å). Crystal data: C16H12N4O10, M
r = 420.29, a = 10.079(1), b = 11.139(1), c = 16.162(1) Å, = 91.319(7)°, monoclinic, P21/c, Z = 4. 相似文献
123.
Klymchenko AS Duportail G Ozturk T Pivovarenko VG Mély Y Demchenko AP 《Chemistry & biology》2002,9(11):1199-1208
3-hydroxyflavone (3-HF) derivatives are very attractive fluorescence sensors due to their ability to respond to small changes in their microenvironment via a dramatic alteration of the relative intensities of their two well-separated emission bands. We developed fluorescence probes with locations at different depths and orientations of 3-HF moiety in the phospholipid bilayer, which determine their fluorescence behavior. While the spectral shifts of the probes correlate with their binding site polarity, the intensity ratio is a complex parameter that is also sensitive to the local hydration. We demonstrate that even the deeply located probes sense this hydration effect, which can be modulated by the charge of the lipid heads and is anisotropic with respect to the bilayer plane. Thus the two-band ratiometric fluorescence probes can provide multiparametric information on the properties of lipid membranes at different depths. 相似文献
124.
Interphase boundaries between 3C SiC grains and two different -Si3N4 morphologies in Si3N4–SiC composites have been studied by transmission electron microscopy. In general, boundaries between small -Si3N4 intragranular precipitates and surrounding SiC grains were relatively free of intergranular films, whereas boundaries between large -Si3N4 grains and adjacent SiC grains were invariably covered with thin intergranular films. Orientation relationships approximating to [110] 3C SiC [0001] -Si3N4 and (001) 3C SiC (10
0) -Si3N4 were found to dominate between 3C SiC grains and the intragranular -Si3N4 precipitates, but there was no evidence of any favoured orientation relationship between the large -Si3N4 grains and adjacent SiC grains. The rationale for special orientation relationships arising when there is no intergranular film present at 3C SiC–-Si3N4 interfaces is explored geometrically using the near-coincidence site lattice model, with the significant result that the dominant orientation relationships between 3C SiC grains and the intragranular -Si3N4 precipitates have low misfits relative to all other possible orientation relationships between 3C SiC and -Si3N4. 相似文献
125.
Russian Journal of General Chemistry - The Schiff base ligand has been synthesized from 5-bromo-2-hydroxybenzaldehyde and ethyl... 相似文献
126.
2-D elemental distribution of Ge in silicon oxide substrates with differing implantation doses of between 3 × 1016 cm− 2 and 1.5 × 1017 cm− 2 has been investigated by Laser-Induced Breakdown Spectroscopy (LIBS). Spectral emission intensity has been optimized with respect to time, crater size, ablation depth and laser energy. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-Ray Spectroscopy (EDX) have been utilized to obtain crater depth, morphology and elemental composition of the sample material, respectively. LIBS spectral data revealed the possibility of performing 2-D distribution analysis of Ge atoms in silicon oxide substrate. EDX analysis results confirmed that LIBS is capable to detect Ge atoms at concentrations lower than 0.2% (atomic). LIBS as a fast semi-quantitative analysis method with 50 µm lateral and 800 nm depth resolution has been evaluated. Results illustrate the potential use of LIBS for rapid, on-line assessment of the quality of advanced technology materials during the manufacturing process. 相似文献
127.
We have applied new methods for performing coupled-cluster calculations to small molecules containing iodine atoms; specifically, NI3 and N2I4. Because NI3 is known to be very reactive, attempts to measure its thermodynamic properties have been challenging at best. To date, N2I4 has not been isolated, and our results suggest that its isolation will be just as challenging. We find that the ΔHf(NI3)=+307.7 kJ mol−1 and ΔHf(N2I4)=+551.6 kJ mol−1, confirming that they are unstable with respect to their decomposition products N2 and I2. 相似文献
128.
In this paper a typical fluid-structure interaction scenario is investigated for a turbulent flow past a circular cylinder
at a relatively low subcritical Reynolds number. Numerous experimental and numerical studies have been undertaken for a baseline
Reynolds number of 4,000 involving a stationary cylinder to study in detail the near wake mean flow and turbulence characteristics.
These studies conclusively show that the turbulent wake displays significant coherent periodic structures of large eddies
that could be adequately and profitably resolved by “low order modelling” of turbulence. In this study, an unsteady numerical
framework is employed for the simulations, incorporating an Arbitrary Lagrangian–Eulerian (ALE) method for the associated
grid deformation to simulate the coupled motion of the circular cylinder with a single degree of freedom in the initial zone
in a typical cylinder-flow response map or what is called “initial regime”. Particular attention is paid towards resolving
the large scales of the fluid motion and the inherent coupling of the cylinder’s motion towards the associated evolution of
the time averaged flow field. The flow-induced vibration effects regarding the kinetic energy exchange between the mean flow
and the coherent periodic scales are investigated further. The predictions discussed and analyzed in detail in the paper display
reasonable agreement with the chosen benchmark tests of the stationary cylinder and suggest that the conclusions outlined
regarding the coupled flow-cylinder system potentially provides a valuable contribution to the state of the art. 相似文献
129.
SiO2 layer structures with a middle layer containing Ge nanocrystals were prepared by sputtering on n- and p-type Si substrates, and by consecutive annealing. Ge content in the middle layer was varied in the range of 40-100%. Most of the structures exhibited low breakdown voltages. The current through the structures became Schottky-like after breakdown. However, some p-type samples showed a considerable memory effect. It was obtained by spectroscopic ellipsometry that the middle layer contains amorphous Ge phase as well. The results also suggest intermixing of the layers during the sputtering and/or the annealing process. 相似文献
130.
Let A be an f-algebra with unit and L,M be two f-modules on A. We define f-orthomorphisms from L into M and show that these operators coincide with the f-linear operators whenever M is topologically full with respect to A. We show that f-orthomorphisms enjoy many of the properties of orthomorphisms. 相似文献