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161.
162.
Diethylzinc-mediated radical addition to CN bonds was investigated in the presence of phenylorganotellurium compounds as radical precursors. As group transfer agents, secondary alkyl phenyl tellurides were shown to be about twice as reactive as the corresponding alkyl iodides towards ethyl radical. Their use was proven to be advantageous regarding both chemoselectivity and yield. The replacement of diethylzinc by dimethylzinc, offers no advantage in these reactions. 相似文献
163.
Standard thermodynamic properties of minerals and phases of ternary systems Ag-Au-X (X = S, Se, Te) are determined by measuring the EMF in the cells with a common gas space and Ag4RbI5 as the solid electrolyte. By this means, thermodynamic functions of the following minerals and phases are determined: Au2S, Ag3AuS2 (uytenbogaardtite), AgAuS (petrovskaite), Ag2Se (naumannite), AuSe, Ag3AuSe2 (fischesserite), and Ag5Te3 (stuetzite). Thermodynamics of a pyrite-pyrrhotite equilibrium in the Ag-Fe-S system is studied in a cell with a solid electrolyte based on silver iodide at 500–730 K and atmospheric pressure. 相似文献
164.
The commensurate superstructures of a NiAs/Ni2In type parent structure, Ni3.32InTe2 and Ni3.12In0.86Te2.14 (q=γ[0 0 1]*, γ=2/3) as well as one dimensionally incommensurate structure of Ni3InTe2 (γ=0.71) were refined from neutron powder diffraction data (Rwp=4.77%, 4.53% and 4.91% for the three structures, respectively, at 298 K). The commensurate structures were refined in the P63/mmc space group (c=3cNiAs). The stacking sequence at the hcp array is -In/Te/Te/- and the trigonal bipyramidal site within the In layer, Ni(2), is partially occupied while it is empty in the Te layers. The octahedral position in between the In and Te layers, Ni(1a), is fully occupied while the octahedral position in between two adjacent Te layers, Ni(1b), is partially occupied. With decreasing In and Ni content, the modulation wave vector, γ, was found to increase continuously until γ=1. From this, crenel functions to describe the whole homogeneity range of the solid solution were constructed with the length of the atomic domains ΔTe=γ (and hence ΔIn=ΔNi=1−γ) and ΔNi(1b)=γ/2 (and hence ΔNi(1a)=1−γ/2) which were then used for the refinement of the incommensurate structure of Ni3InTe2. The corresponding effect in real space is that the single In layers separating double layers of Te occur less frequent when γ in increasing until at γ=1 the CdI2 type structure of Ni1+xTe2 is reached. 相似文献
165.
166.
Thermal noise measurements at proper biasing conditions are shown to represent a powerful tool for the characterization of the homogeneity of thin nanostructured films and their adhesion to the substrate. By modeling a thin-film as a two-dimensional random resistor network, we introduce a new type of excess-noise arising from local sources of Nyquist noise due to the presence of defective regions. The dishomogeneous Joule heating of the film is responsible for a thermal and electrical instability which is efficiently described by using a biased percolation model. The results of our simulations show that the Nyquist excess-noise temperature should provide a sensitive and non-destructive indicator of the packing density and of the quality of heat contact to the substrate of nanostructured films with grain size in the range 10–500 nm. 相似文献
167.
168.
The impact of a rotating magnetic field (RMF) on the axial segregation in Vertical Gradient Freeze (VGF) grown, Ga doped germanium is investigated. Growth experiments were performed using the VGF‐RMF as well as the conventional VGF technique. Carrier concentration profiles characterising the Ga segregation were measured by the Spreading Resistance method and calibrated using Hall values of carrier concentration and mobility. The Ga concentration rises more gradually under RMF action, i.e., the dopant segregation is significantly reduced by the rotating field. This effect is attributed to a better mixing of the melt. Numerical results on the flow velocity confirm this explanation. The RMF induced flow is much more intense than the natural buoyant convection due to the radial temperature gradient and leads to a pronounced decrease of the effective partition coefficient keff. In the early stages of growth a keff value close to k0 was obtained, i.e., the gallium was almost homogeneously distributed within the melt. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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170.
V. V. Litvinov A. A. Klechko J. L. Lindstrom V. P. Markevich L. I. Murin 《Journal of Applied Spectroscopy》2000,67(5):904-909
The vibrational absorption bands associated with some types of double thermal donors (TD) in Ge enriched with the oxygen isotopes 16O and 18O have been identified. The thermal donors were formed during heat treatment of Ge:O crystals at 300 and 350°C. Absorption spectra were measured at room temperature and at 10 K. The formation of the thermal donors was accompanied by the appearance of three absorption bands, which in the Ge:16O spectra at room temperature are located at 600, 740, and 780 cm–1. In low-temperature measurements, the bands at 600 and 780 cm–1 exhibited splitting into series of narrow lines (up to 9) associated with some types of thermal donors (TD1–TD9). The absorption spectra measured at 10 K after different cooling conditions display bistability of the first four types of thermal donors (TD1–TD4). In the samples cooled by illumination with light in the region of frequencies of the fundamental absorption of Ge, pairs of lines are observed that belong to the bistable thermal donors in the helium-like configuration of double donors (DD). After cooling the samples in the dark, these pairs of lines are replaced by three new bands, which belong to local vibrational modes of bistable thermal donors in the low-energy neutral configuration. Based on the isotopic shift of the local vibrational modes of the thermal donors in Ge:16O and Ge:18O, a rigorous proof of the oxygen atoms entering into the composition of thermal donors is obtained. 相似文献