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排序方式: 共有168条查询结果,搜索用时 109 毫秒
21.
22.
燃气辐射供暖系统辐射管发射率对室内热环境的影响研究 总被引:2,自引:0,他引:2
在对物理模型合理简化的基础上,对燃气辐射供暖空间温度场的分布进行了模拟,指出辐射管不同发射率对空间温度场的影响,指出提高辐射管黑度可强化燃气辐射供暖技术。 相似文献
23.
The paper demonstrates a versatile procedure suitable for industrial implementation of temperature measurement on a hot titanium alloy. The driving force has been the need for an accurate temperature measurement during additive manufacturing using laser welding technology where Ti–6Al–4V-wire is melted. The challenges consider both industrial constraints and the varying emissivity of the surface. Measurements makes use of a narrow bandwidth spot radiation pyrometer and a calibration procedure for estimation of the surface temperature through spectral emissivity estimation. The theoretical results are validated through experiments. A number of difficulties in radiation temperature measurements for metals with varying surface properties are discussed; especially the case of surface oxidation. The uncertainty in temperature reading due to the uncertainty in the emissivity estimate is established along with a model that qualitatively describes surface oxidation. The procedure is expected to be useful for several manufacturing applications where it is important to control high temperatures. 相似文献
24.
在温度量值复现与传递以及国际比对中经常需要对亮度温度进行波长修正.探讨了钨带灯结构与亮度温度模型的关系,计算了T型钨带灯在400~1100 nm亮度温度对波长的导数,并利用实验数据进行了大波长间隔的修正验证.定性分析了不同结构钨带灯与T型钨带灯亮度温度-波长特性的差异.利用钨带灯的亮度温度-波长特性进行波长修正可减小温度量值传递的不确定度,扩展钨带灯应用的光谱范围. 相似文献
25.
器件表面温度是表征器件热性能的重要参数,应用红外热像法探测表面温度时,影响其测量结果准确性的关键因素是表面发射率的修正,通过对红外热像法发射率直接修正误差的统计分析,给出了不同条件下的发射率修正值标准差δ、误差ε的范围,提出了应用于电子器件的最小误差探测条件。 相似文献
26.
C. Monte B. Gutschwager S. P. Morozova J. Hollandt 《International Journal of Thermophysics》2009,30(1):203-219
A new experimental facility was realized at the PTB for reduced-background radiation thermometry under vacuum. This facility
serves three purposes: (i) providing traceable calibration of space-based infrared remote-sensing experiments in terms of
radiation temperature from −173 °C to 430 °C and spectral radiance; (ii) meeting the demand of industry to perform radiation
thermometric measurements under vacuum conditions; and (iii) performing spectral emissivity measurements in the range from
0 °C to 430 °C without atmospheric interferences. The general concept of the reduced background calibration facility is to
connect a source chamber with a detector chamber via a liquid nitrogen-cooled beamline. Translation and alignment units in
the source and detector chambers enable the facility to compare and calibrate different sources and detectors under vacuum.
In addition to the source chamber, a liquid nitrogen-cooled reference blackbody and an indium fixed-point blackbody radiator
are connected to the cooled beamline on the radiation side. The radiation from the various sources is measured with a vacuum
infrared standard radiation thermometer (VIRST) and is also imaged on a vacuum Fourier-transform infrared spectrometer (FTIR)
to allow for spectrally resolved measurements of blackbodies and emissivity samples. Determination of the directional spectral
emissivity will be performed in the temperature range from 0 °C to 430 °C for angles from 0° to ±70° with respect to normal
incidence in the wavelength range from 1 μm to 1,000 μm.
References to commercial products are provided for identification purposes only and constitute neither endorsement nor representation
that the item identified is the best available for the stated purpose. 相似文献
27.
Olivier Rozenbaum Domingos De Sousa Meneses Patrick Echegut 《International Journal of Thermophysics》2009,30(2):580-590
Thermal and optical properties of ceramics are dependent on radiation scattering and cannot be determined by a knowledge of
their chemical composition alone, as for single crystals. In this paper, extrinsic effects, such as roughness, porosity, and
texture, on the spectral emissivity of alumina ceramics are investigated. Roughness effects have an influence mainly in the
opaque zone; an important porosity dependence and the presence of a critical porosity threshold were observed in the semitransparent
zone. Furthermore, it was shown that two ceramics with similar total porosities, but with different textures, possess radically
different emissivities, showing that grain size, pore size, and spatial repartition of the grains are also crucial for an
understanding of the thermal properties of the ceramics.
This study was performed at CEMTHI laboratory. 相似文献
28.
V. B. Khromchenko S. N. Mekhontsev L. M. Hanssen 《International Journal of Thermophysics》2009,30(1):9-19
To complement existing water bath blackbodies that now serve as NIST primary standard sources in the temperature range from
15 °C to 75 °C, a gallium fixed-point blackbody has been recently built. The main objectives of the project included creating
an extended-area radiation source with a target emissivity of 0.9999 capable of operating either inside a cryo-vacuum chamber
or in a standard laboratory environment. A minimum aperture diameter of 45 mm is necessary for the calibration of radiometers
with a collimated input geometry or large spot size. This article describes the design and performance evaluation of the gallium
fixed-point blackbody, including the calculation and measurements of directional effective emissivity, estimates of uncertainty
due to the temperature drop across the interface between the pure metal and radiating surfaces, as well as the radiometrically
obtained spatial uniformity of the radiance temperature and the melting plateau stability. Another important test is the measurement
of the cavity reflectance, which was achieved by using total integrated scatter measurements at a laser wavelength of 10.6 μm.
The result allows one to predict the performance under the low-background conditions of a cryo-chamber. Finally, results of
the spectral radiance comparison with the NIST water-bath blackbody are provided. The experimental results are in good agreement
with predicted values and demonstrate the potential of our approach. It is anticipated that, after completion of the characterization,
a similar source operating at the water triple point will be constructed.
Certain commercial equipment, instruments, or material are identified in this paper to specify the experimental procedures
and result adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute
of Standards and Technology, nor is it intended to imply that material or equipment identified are necessarily the best available
for the purpose. 相似文献
29.
Xiaogang Sun Peng Xiao Guibin Yuan Jingmin Dai 《International Journal of Thermophysics》2009,30(1):249-256
The temperatures and emissivities of the metallic thermal protection blanket at (900–1,300) °C are investigated experimentally
by using a multi-wavelength pyrometer. A linear relation between the emissivity and true temperature at different wavelengths
is assumed. Based on this assumption, the true temperatures and spectral emissivities of the metallic thermal protection blanket
at the two temperature measurement points can be calculated simultaneously. Some experimental results for the practical data
processing of measurements performed on the metallic thermal protection blanket show that the difference between the calculated
temperature and the temperature measured by a standard thermocouple is within ± 10°C. 相似文献
30.