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31.
Monitoring studies of a small maintenance dredging operation in Coos Bay, Oregon, showed that significant decreases of benthic infaunal abundance immediately after dredging extended at least 100 m from the site of actual dredging. The infauna re-adjusted to pre-dredging conditions within 28 days in the dredged area and within 14 days in the adjacent areas. At the spoil site a similar decrease was followed by a 2-week recovery period. The authors suggest that an area subjected to maintenance dredging is also subjected to frequent disturbances from ship movements and other harbor activities and that the infauna is well adapted to this. Thus, maintenance dredging is a relatively normal event and should not be expected to have catastrophic effects.  相似文献   
32.
Materials exhibiting nodal‐line fermions promise superb impact on technology for the prospect of dissipationless spintronic devices. Among nodal‐line semimetals, the ZrSiX (X = S, Se, Te) class is the most suitable candidate for such applications. However, the surface chemical reactivity of ZrSiS and ZrSiSe has not been explored yet. Here, by combining different surface‐science tools and density functional theory, it is demonstrated that the formation of ZrSiS and ZrSiSe surfaces by cleavage is accompanied by the washing up of the exotic topological bands, giving rise to the nodal line. Moreover, while the ZrSiS has a termination layer with both Zr and S atoms, in the ZrSiSe surface, reconstruction occurs with the appearance of Si surface atoms, which is particularly prone to oxidation. It is demonstrated that the chemical activity of ZrSiX compounds is mostly determined by the interaction of the Si layer with the ZrX sublayer. A suitable encapsulation for ZrSiX should not only preserve their surfaces from interaction with oxidative species, but also provide a saturation of dangling bonds with minimal distortion of the surface.  相似文献   
33.
We have studied the temperature dependence of the Hall effects in multilayer selectively doped InGaAs/GaAs heterostructures with quantum dots (QDs). It was found that structures possessing photoconductivity in the IR range exhibit a sharp (nearly exponential) growth of the conductivity and Hall mobility in the temperature interval from 8 to 30 K at a virtually constant Hall coefficient and electron density. A new mechanism of the lateral photoconductivity in the structures with QDs is proposed which is related to the change in the electron mobility in the two-dimensional channel as a result of a decrease in the Coulomb scattering on charged QDs.  相似文献   
34.
Palladium ditelluride (PdTe2) is a novel transition‐metal dichalcogenide exhibiting type‐II Dirac fermions and topological superconductivity. To assess its potential in technology, its chemical and thermal stability is investigated by means of surface‐science techniques, complemented by density functional theory, with successive implementation in electronics, specifically in a millimeter‐wave receiver. While water adsorption is energetically unfavorable at room temperature, due to a differential Gibbs free energy of ≈+12 kJ mol?1, the presence of Te vacancies makes PdTe2 surfaces unstable toward surface oxidation with the emergence of a TeO2 skin, whose thickness remains sub‐nanometric even after one year in air. Correspondingly, the measured photocurrent of PdTe2‐based optoelectronic devices shows negligible changes (below 4%) in a timescale of one month, thus excluding the need of encapsulation in the nanofabrication process. Remarkably, the responsivity of a PdTe2‐based millimeter‐wave receiver is 13 and 21 times higher than similar devices based on black phosphorus and graphene in the same operational conditions, respectively. It is also discovered that pristine PdTe2 is thermally stable in a temperature range extending even above 500 K, thus paving the way toward PdTe2‐based high‐temperature electronics. Finally, it is shown that the TeO2 skin, formed upon air exposure, can be removed by thermal reduction via heating in vacuum.  相似文献   
35.
Abstract

The paper contains a complete annotated list of freshwater ichthyofauna of the Middle Ob River basin. The list is based on an analysis of publications and on the results of the authors’ research, and it includes 43 species in two classes, 9 orders, 12 families, and 30 genera. Ten of all listed species are introduced and only seven are naturalized. For each species, taxonomic comments are provided where necessary and conservation status, distribution within the Middle Ob River basin, abundance and commercial value are indicated. Latin and English names are given.  相似文献   
36.
Recurrent neural networks with fixed weights have been shown in practice to successfully classify adaptively signals that vary as a function of time in the presence of additive noise and parametric perturbations. We address the question: Can this ability be explained theoretically? We provide a mathematical proof that these networks have this ability even when parametric perturbations enter the signals nonlinearly. The restrictions that we impose on the signals to be classified are that they satisfy an assumption of nondegeneracy and that noise amplitude is sufficiently small. Further, we demonstrate that the recurrent neural networks may not only classify uncertain signals adaptively but also can recover the values of uncertain parameters of the signals, up to their equivalence classes.  相似文献   
37.
Monolayer VSe2, featuring both charge density wave and magnetism phenomena, represents a unique van der Waals magnet in the family of metallic 2D transition‐metal dichalcogenides (2D‐TMDs). Herein, by means of in situ microscopy and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X‐ray and angle‐resolved photoemission, and X‐ray absorption, direct spectroscopic signatures are established, that identify the metallic 1T‐phase and vanadium 3d1 electronic configuration in monolayer VSe2 grown on graphite by molecular‐beam epitaxy. Element‐specific X‐ray magnetic circular dichroism, complemented with magnetic susceptibility measurements, further reveals monolayer VSe2 as a frustrated magnet, with its spins exhibiting subtle correlations, albeit in the absence of a long‐range magnetic order down to 2 K and up to a 7 T magnetic field. This observation is attributed to the relative stability of the ferromagnetic and antiferromagnetic ground states, arising from its atomic‐scale structural features, such as rotational disorders and edges. The results of this study extend the current understanding of metallic 2D‐TMDs in the search for exotic low‐dimensional quantum phenomena, and stimulate further theoretical and experimental studies on van der Waals monolayer magnets.  相似文献   
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It is established for the first time that the phenomenon of ion-stimulated surface segregation can be used to increase the depth resolution of Auger profiling during analysis of the Inx Ga1 − x As/GaAs heterostructures. It is demonstrated that, by varying the energy of the sputtering Ar+ ion beam from 1 to 0.5 keV in the region of the GaAs/InGaAs heterojunction, the junction sharpness can be estimated at a resolution on the order of 0.5 nm determined by a difference in the projected range of Ar+ ions and independent of the escape depth of the Auger electrons.  相似文献   
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