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11.
C. B. Jacoby C. L. Holliman D. L. Rempel M L. Gross 《Journal of the American Society for Mass Spectrometry》1993,4(2):186-189
It has been difficult to achieve the expected high resolving power for high-mass biomolecule ions in Fourier transform mass spectrometry. Our hypothesis is that ion clouds produced by laser desorption or injection are diffuse and produce poor signals. To test the hypothesis, clouds of benzene molecular ions produced by electron ionization were purposefully expanded via magnetron mode excitation and characterized by a new experimental sequence for cloud sectional analysis. The expanded cloud was then successfully focused to the trap center by using a high-pressure dynamic event (radiofrequency-only mode). The expanded cloud in a conventional cubic trap produces no detectable signal, whereas the focused cloud in a compensated trap yields a high-resolution signal with good signal-to-noise ratio. 相似文献
12.
Iron Nanoparticles in Severe-plastic-deformed Copper 总被引:1,自引:0,他引:1
Superparamagnetic iron nanoparticles with a size of a few nanometers were produced in copper by severe plastic deformation. In a isochronal annealing experiment near a temperature of 450K, which corresponds to the temperature of structural relaxation and the first step of grain growth (from 128 to 150nm) of submicrocrystalline copper, an abrupt increase in the magnetic susceptibility is detected. This increase is shown to be due to iron nanoparticles increasing in size from 2.8 to 3.3nm. The vanishing of the ferromagnetic contribution by iron nanoparticles observed at 850K, well below the Curie temperature of iron, is due to the dissolution of nanoparticles in plastically deformed copper. 相似文献
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A method for calculating the x-ray diffraction patterns of cadmium sulfide nanoparticles with a disordered internal structure, a real surface, shape, and size is proposed within the kinematic theory of scattering. A computer analysis has revealed that the characteristic shape of the experimental x-ray diffraction patterns of cadmium sulfide films and powders is determined by a specific disordered nanoparticle structure differing from the crystal structures of wurtzite and sphalerite. According to the computer simulation, cadmium sulfide nanoparticles synthesized through chemical deposition have a shape similar to a hexagonal prism with a characteristic size of approximately 5 nm. 相似文献
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For a transmission problem for the Laplace operator the unique solvability is proved in natural Sobolev spaces in the case when edges and corners are present. The behaviour of the solution near the corner is reduced to the question when an explicitely given meromorphic family of one-dimensional integral operators on a geodesic polygon on the two sphere has a non-trivial kernel. 相似文献
18.
A. S. Vorokh N. S. Kozhevnikova A. A. Rempel A. Magerl 《Journal of Structural Chemistry》2010,51(6):1170-1175
Dense thin nanostructured films of cadmium sulfide CdS obtained by chemical deposition from aqueous solutions are strongly
bound to a substrate due to the formation of cadmium hydroxide Cd(OH)2 in the system. By X-ray reflectometry and grazing incidence diffraction it is found that at the beginning of the deposition
a dense Cd(OH)2/SiO2 layer is produced on the surface of a silicon or glass substrate. This layer is formed through the atomic-layer adsorption
of crystalline 1–3 nm thick Cd(OH)2 film by the oxygencontaining substrate surface. During sulfidation of this cadmium-containing substrate layer, a surface
nucleation layer of CdS/Cd(OH)2/SiO2 forms, which provides the growth, denseness, and strong adhesion to the substrate of nanostructured CdS film with a disordered
structure. According to the obtained experimental data, a “hydroxide scheme” of film deposition is confirmed and refined,
and the stages of CdS nanofilm formation are determined. 相似文献
19.
We recently described a new electrically compensated trap in FT ion cyclotron resonance mass spectrometry and developed a means of tuning traps of this general design. Here, we describe a continuation of that research by comparing the ion transient lifetimes and the resulting mass resolving powers and signal-to-noise (S/N) ratios that are achievable in the compensated vs. uncompensated modes of this trap. Transient lifetimes are ten times longer under the same conditions of pressure, providing improved mass resolving power and S/N ratios. The mass resolving power as a function of m/z is linear (log-log plot) and nearly equal to the theoretical maximum. Importantly, the ion cyclotron frequency as a function of ion number decreases linearly in accord with theory, unlike its behavior in the uncompensated mode. This linearity should lead to better control in mass calibration and increased mass accuracy than achievable in the uncompensated mode. 相似文献
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