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排序方式: 共有2208条查询结果,搜索用时 11 毫秒
51.
L. Mollard G. Destefanis N. Baier J. Rothman P. Ballet J. P. Zanatta M. Tchagaspanian A. M. Papon G. Bourgeois J. P. Barnes C. Pautet P. Fougères 《Journal of Electronic Materials》2009,38(8):1805-1813
This paper reviews recent developments in the characterization of planar p-on-n photodiodes fabricated from long- and mid-wavelength Hg1−x
Cd
x
Te at␣the Electronics and Information Technology Laboratory (LETI). The Hg1−x
Cd
x
Te epitaxial layers were grown by both liquid-phase and molecular-beam epitaxy. Planar p-on-n photodiodes were fabricated by arsenic implantation into an indium-doped Hg1−x
Cd
x
Te base layer. Electro-optical characterization on these p-on-n photodiodes showed low leakage currents (shunt resistance > 10 GΩ) and mean R
0
A values comparable to the state of the art, i.e., equal to 5000 Ω cm2 at λ
c = 9.3 μm (λ
c: cutoff wavelength). Results of focal-plane arrays operating in both the long-wavelength infrared (IR) and middle-wavelength
IR bands are reported, with noise equivalent delta temperature and responsivity values at λ
c = 9.3 μm in excess of 99.64%. These results demonstrate the viability and technological maturity of both material growth and device
processing. 相似文献
52.
J. Wei J. Barnes S. Guha L. P. Gonzalez Y. K. Yeo R. L. Hengehold G. Rajagopalan 《Journal of Electronic Materials》2011,40(2):103-108
Bulk ternary InAs1−y
P
y
polycrystals with diameters up to 50 mm were grown from a pseudobinary InP-InAs melt using the vertical Bridgman technique.
Electrical and optical properties were investigated as functions of alloy composition and sample temperature. As-grown undoped
crystals have been found to exhibit n-type conductivity irrespective of alloy composition. Though the bulk InAs1−y
P
y
substrates show high optical transmission out to long wavelengths as well as high carrier mobility, they exhibit random compositional
fluctuations across the substrate area. 相似文献
53.
Dirk‐Michael Drotlef Lukas Stepien Michael Kappl W. Jon P. Barnes Hans‐Jürgen Butt Aránzazu del Campo 《Advanced functional materials》2013,23(9):1137-1146
Elastic, microstructured surfaces (hydrophobic and hydrophilic) mimicking the surface structure of tree‐frog toe‐pads are fabricated. Their adhesion and friction behaviour in the presence of a liquid layer is evaluated and compared to flat controls. Tree‐frog‐like patterns are beneficial for wet adhesion only if the liquid does not wet the surface. The situation is different in friction, where the surface structure lead to significantly higher friction forces only if the liquid does wet the surface. Taking into account that tree‐frog attachment pads are hydrophilic and that their secretion wets all kind of surfaces, our results indicate that the surface structure in tree‐frog toe‐pads has been developed for climbing, when shear (friction) forces are involved. These results evidence the benefits and limitations of the surface design (microstructure and hydrophilicity) for adhesion and friction under wet conditions. 相似文献
54.
The Earth Observing System (EOS) is an international, 18-year program in global remote sensing of the Earth comprising multiple instruments flown on several satellite platforms. The first EOS platform, AM1, scheduled for launch in 1998, includes five instruments designed to make radiometric and reflectance measurements of the Earth over a wavelength range extending from the visible to the thermal infrared. The goal of the EOS-AM1 platform and instruments is to advance the scientific understanding of the Earth in the areas of clouds, aerosols, radiative balance, terrestrial and oceanic characterization, and the carbon cycle. In order to achieve this goal, the EOS-AM1 instruments must produce state-of-the-art accurate, precise, and consistent radiance and reflectance measurements over their five-year lifetimes. In addition, the production of continuous remote-sensing data from multiple instruments on several platforms requires that the remote-sensing measurements of the AM1 platform be radiometrically tied to the measurements made by instruments on successive platforms. This is achieved through careful prelaunch and postlaunch instrument calibration, cross-calibration, and level 1B data validation (i.e. vicarious calibration). This paper presents an overview of the calibration, cross-calibration, and level 1B data validation strategy for the AM1 platform 相似文献
55.
Fitzer C. Arulampalam A. Barnes M. Zurowski R. 《Power Electronics, IEEE Transactions on》2002,17(6):1058-1066
During the transient period at the start of a voltage sag, a DVR injection transformer can experience a flux-linkage that is up to twice its nominal steady-state value. In order to prevent the transformers from saturating it is normal to choose a rating flux that is double that of the steady-state limit. An alternative method is to limit the flux-linkage during the transient switch-on period, thus preventing saturation. It is shown through both simulation and experimental results that an adaptive form factor can be applied to the DVR injected voltage, which minimizes the disturbance seen by a sensitive load, while at the same time preventing saturation. The proposed method removes the need for rating the series injection transformers for the DVR transient switch-on period, and therefore removes the redundancy normally associated with their steady state operation. In economic terms, this may reduce the total cost of a DVR system, thus making it a more attractive solution for voltage sag mitigation. 相似文献
56.
Elucidating the Origins of Subgap Tail States and Open‐Circuit Voltage in Methylammonium Lead Triiodide Perovskite Solar Cells 下载免费PDF全文
Tian Du Jinhyun Kim Jonathan Ngiam Shengda Xu Piers R. F. Barnes James R. Durrant Martyn A. McLachlan 《Advanced functional materials》2018,28(32)
Recombination via subgap trap states is considered a limiting factor in the development of organometal halide perovskite solar cells. Here, the impact of active layer crystallinity on the accumulated charge and open‐circuit voltage (Voc) in solar cells based on methylammonium lead triiodide (CH3NH3PbI3, MAPI) is demonstrated. It is shown that MAPI crystallinity can be systematically tailored by modulating the stoichiometry of the precursor mix, where small quantities of excess methylammonium iodide (MAI) improve crystallinity, increasing device Voc by ≈200 mV. Using in situ differential charging and transient photovoltage measurements, charge density and charge carrier recombination lifetime are determined under operational conditions. Increased Voc is correlated to improved active layer crystallinity and a reduction in the density of trap states in MAPI. Photoluminescence spectroscopy shows that an increase in trap state density correlates with faster carrier trapping and more nonradiative recombination pathways. Fundamental insights into the origin of Voc in perovskite photovoltaics are provided and it is demonstrated why highly crystalline perovskite films are paramount for high‐performance devices. 相似文献
57.
58.
Experimental work carried out in a flow reactor has shown that, from 700 to 750 K, low concentrations of ethane can act as a virtual catalyst in effecting the oxidation of NO to NO2. That is, while there is strong promotion of the oxidation of NO, there is very little concurrent degradation of the ethane. This contrasts with other experimental and modeling investigations, in which promotion by the hydrocarbon of NO oxidation has accompanied oxidation of a considerable fraction of the hydrocarbon. The rate of this pseudo-catalytic effect is significantly affected by the concentrations of both ethane and oxygen, which in this study ranged from 0 to 70% for [O2], 0 to 5000 ppm for [C2H6], and 0 to 350 ppm for [NO]. The level of reaction achieved under the various conditions was measured in terms of the rates of formation of NO2 and C2H4. Current kinetic mechanisms, though displaying good accuracy in other temperature regimes, fail to predict this pseudo-catalytic behavior of ethane, indicating that several elementary reactions important at the low temperatures are missing or poorly represented in such mechanisms. Mechanistic modifications are discussed and allow the measurements to be simulated more closely than with existing reaction schemes. It has been shown that the relative rates of the competing reactions C2H5 + O2 → C2H4 + HO2 and C2H5 + O2 (+M) → C2H5O2 + (M) are of critical importance in this situation. 相似文献
59.
Deep level transient spectroscopy (DLTS) measurements have been performed on a variety of AlxGa1-xAs p-n junctions prior to and following a series of fast neutron irradiations at room temperature and subsequent isochronal
anneals. In contrast with electron and proton irradiated GaAs, neutron irradiation produces a single, broad featureless DLTS
band which is a majority carrier trap in both n and p type material. The characteristics of this neutron-induced trap are
relatively independent of growth method, dopant type and concentration. In GaAs, the thermal emission energies of the trap
are 0.58 to 0.68 eV depending on the particular junction. These energies increase with Al content to 0.94 eV at 20% Al. The
trap introduction rate, which also increases with Al content, is 0.7 cm-1 in GaAs. Isochronal annealing to temperatures as high as 400‡C results in a smaller FWHM of the DLTS band, a shift in the
peak to higher temperatures, and a modest decrease in magnitude. Above 400‡C the magnitude decreases rapidly, suggesting a
similarity with the antisite defect, AsGa, which has been observed to anneal in this range. 相似文献
60.