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1.
《Journal of Crystal Growth》2006,286(2):205-208
We demonstrated seeded growth of AlN on large-area Al- and N-polar <0 0 0 1>-oriented AlN seeds using the physical vapor transport method (PVT). In both cases, crystals having a diameter of 15 mm were obtained from 5 mm seeds. Based on growth step and terrace width analyses, it was found that the N-polar face was suitable for growth within a large window of growth parameters while the Al-polar seeds yielded high-quality crystals only at low supersaturation. 相似文献
2.
《Spectrochimica Acta Part B: Atomic Spectroscopy》1986,41(4):361-376
Physical parameters and analytical performance are determined for an analytical ICP operated at 148 MHz, a frequency nearly three times higher than any previously reported. The iron(I) excitation temperatures are approximately 1.5 times lower and the electron densities are five times lower than at 27 MHz. The consequences of these changes are lower analyte and background continuum emission intensities, such that the signal to background ratios are decreased at the higher frequency. Freedom from interferences and working curve linearity are unaffected while ease of sample introduction is improved. A shift towards atomic emission indicates a deviation farther from LTE at 148 MHz. These effects are attributed to the decrease in skin depth with increasing frequency. 相似文献
3.
《Nuclear Physics A》1986,452(4):573-590
By means of a streamer chamber exposed to the LEAR antiproton beams, the total reaction cross sections, the charged-prong multiplicity distributions and lower limits for the production of negative pions and Ks0 in the p̄-Ne interaction were measured at 19.6, 48.7 and 179.6 MeV. Annihilation was found to be dominant over all other non-elastic p̄-Ne processes. An analysis of Ne and other nuclei data in the frame of the Glauber theory allowed us to determine the ratio between the p̄-n and the p̄-p cross sections. An analysis in the light of INC model predictions allowed us to show up events which can be interpreted as annihilations having occurred deeply inside the nuclei. 相似文献
4.
《Solid State Communications》1986,59(11):765-769
Annealing of f.c.c. TiC0.625 for 10 days between 780 and 750°C leads to a trigonal superstructure by ordering of carbon vacancies. Long-range ordering decreases slightly the residual electrical resistivity ϱ(1.6 K) and the electronic specific heat and increases the temperature coefficient of the resistivity dϱ/dT between 100 and 300 K. A minimum in ϱ(T), more apparent in the disordered samples (around 65 K) is attributed to the scattering of electrons by the strong atomic disorder. 相似文献
5.
《Solid State Ionics》1986,22(1):97-104
Chemical and physical studies of molybdenum disulfide show that the extreme anisotropy which dominates the bulk properties of this layered compound is also very important in the understanding of surface properties. We observe that the basal surfaces in single crystals are chemically and optically inert. The edge surfaces are highly reactive to both oxygen and metallic impurities. Photoemission spectroscopy and optical absorption show that the edge surfaces have electronic states within the forbidden gap. The density of these surface defects is correlated with the hydrodesulfurization catalytic activity. 相似文献
6.
《Statistics & probability letters》1986,4(5):253-258
The present paper investigates estimation under the hypothesis of homogeneity or independence for a two-way contingency table. A family of optimality criteria (distances) is introduced of which well-known criteria such as maximum likelihood, Pearson- and Neyman chi-square. The Kullback-Liebler distance turn out to be special cases. We look at the convexity properties of this family and provide some general results. Give any member of this family, an analytical solution is provided for the optimal estimator under the hypothesis of homogeneity whereas a simple algorithm solution is given for the optimal row- and column margin estimators under the hypothesis of independence. 相似文献
7.
《Journal of solid state chemistry》1986,63(2):336-340
Use of a Monte Carlo method is proposed for assessing the reliability of the experimental determination of cation distribution in spinels as deduced from X-ray powder diffraction data. The method is demonstrated on the ternary spinels Cu0.6Zn0.4Al2O4 and Cu0.2Mg0.8Al2O4, which present the complication of having two cations with very close X-ray scattering power. It is shown that the proposed method tests out the precision of the cation distribution results with greater detail than what can be obtained by simple consideration of a residual function. 相似文献
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Antimony-based materials continue to provide great interest for infrared photodetector and focal plane array imaging applications. Detector architectures include InAs/Ga(In)Sb strained-layer superlattices, which create a type-II band alignment that can be tailored to cover a wide range of the mid- and long-wavelength bands by varying the thickness and composition of the constituent materials, and bulk InAsSb-based XBn barrier designs. These materials can provide desirable detector features such as wider wavelength range, suppression of tunneling currents, improved quantum efficiency, and higher operating temperatures. In order to bring these advantages to market, a reliable manufacturing process must be established on large diameter substrates. We report our latest work on the molecular beam epitaxy growth of Sb-detector epiwafers on 100 mm diameter GaSb substrates in a multi-wafer production format. The growth process has been established to address the challenges of these demanding structures, including the large numbers of alternating thin layers and mixed group-V elements. Various characterization techniques demonstrate excellent surface morphology, crystalline structure quality, and optical properties of the epiwafers. The measured wafer-to-wafer consistency and cross-wafer uniformity demonstrate the potential for volume manufacturing. 相似文献