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排序方式: 共有77条查询结果,搜索用时 15 毫秒
1.
The XPS of bulk tungsten carbide, partially oxidized WC surfaces at 373 and 573 K as well as tungsten trioxide have been reported. Bulk WC has been prepared from WO3 as a starting material in a mixture of CH4 (20%) and H2 (80%) at 1150 K for 4 h, while partially oxidized WC surfaces were prepared by oxygen chemisorption on a clean WC surface at 200 K, then the temperatures were raised to 373 and 573 K respectively. The XPS of a freshly prepared WC reveals the presence of a small amount of WO3 on the surface and a slightly higher concentration in the bulk. The oxygen-exposed fresh WC surfaces and surfaces treated at temperatures higher than 373 K show the presence of WO3 in a considerable quantity depending on the length and the treatment temperature. Ar+ bombardment of this partially oxidized surface reduces WO3 to WO2 and W(0), while WC is partially reduced to W(0). Isomerization reactions of alkanes on oxygen-exposed WC surface occurs in reality on a composite surface structure containing WC, WO3, WO2 and elemental W(0). 相似文献
2.
Bertram Boehrer Lars Golmen Jarl Eivind Løvik Karsten Rahn Dag Klaveness 《Journal of Great Lakes research》2013
Thermobaric stratification was investigated in very deep lakes of elongated shape. We considered the spring time configuration when large freshwater lakes may have their deepest recirculation. In five very deep freshwater lakes in Norway, profiles were measured in spring 2006 with multiparameter probes. Temperature profiles confirmed thermobaric stratification in all of these lakes, i.e. the temperature profiles crossed the 4 °C line and thus were affected by pressure effects on the temperature of maximum density. Electrical conductance was low in all of the investigated lakes, and vertical gradients were too small to play a role in the density stratification. In all lakes, deep water was well supplied with oxygen. Three out of five lakes showed a temperature gradient close to Eklund's stability theorem. However, the remaining two lakes clearly opposed the theorem. Bottom temperatures were more closely related to lake length than their maximum depths. Oxygen saturation profiles documented recent intensive gas exchange with the atmosphere. They agree well with the possible formation of deep water from density driven flows at horizontal temperature gradients close to 4 °C. 相似文献
3.
Päivi Mäki-Arvela Mika Mikkola Jarl Hemming Kari Eränen Stefan Willför Dmitry Yu. Murzin 《Journal of the American Oil Chemists' Society》2014,91(6):1035-1046
Mixtures of fatty acids and rosin acids are industrially important products utilized as a raw material for several purposes. Their thermal properties, especially cold stability and crystallization behavior is also important. Several fatty acid and rosin acid mixtures both from industrial products and from commercially available fatty and rosin acids were prepared and treated for 30 min at 80 °C under an inert atmosphere. Thereafter, the mixture was cooled to the desired temperature. Determination of the cloud point, chemical analysis of liquid and solid phase, thermal analysis by differential scanning calorimetry as well as morphology analysis by scanning electron microscopy were performed. The results revealed that crystallization was more rapid when it occurred at 10 °C compared to 25 °C. The crystal sizes increased with decreasing the crystallization temperature. Furthermore, crystals were of irregular shape and agglomerated when rapid cooling of the mixture occurred. Chemical analysis revealed that liquid phase was enriched with stearic acid, whereas crystals contained large amounts of abietic, dehydroabietic and linoleic acids. The cloud point of the mixtures increased with increasing amount of stearic and rosin acids. Dehydroabietic acid addition improved the cold stability of the synthetic fatty acid–rosin acids mixture. 相似文献
4.
Helmi Keskinen Jyrki M. Mäkelä Mikko Aromaa Jorma Keskinen Sami Areva Cilâine V. Teixeira Jarl B. Rosenholm Viljami Pore Mikko Ritala Markku Leskelä Mari Raulio Mirja S. Salkinoja-Salonen Erkki Levänen Tapio Mäntylä 《Catalysis Letters》2006,111(3-4):127-132
Titania and titania-silver nanoparticle deposits were made by Liquid Flame Spray technique, in which the liquid precursor
is injected into a high temperature flame, where it will evaporate and nucleate to nanosize particles. One-step and two-step
methods were used for preparation of titania-silver deposits. The amount of silver added was 1 wt%. The deposits were collected
in the flame zone on steel and glass surfaces and were analyzed by TEM, EDS, XPS and SAXS. The titania deposits consisted
of porous nanosized titania agglomerates of primary particles (~10 nm). With silver addition, small spherical silver metal
particles (~2 nm) were detected on the agglomerates. An increase in the photocatalytic activity was verified by stearic acid
decomposition and biofilm removal using Deinococcus geothermalis as the model organism. 相似文献
5.
Chunlin Xu Menghua Qin Yingjuan Fu Na Liu Jarl Hemming Bjarne Holmbom 《木材化学与工艺学杂志》2013,33(2):105-117
Abstract The lipophilic extractives in stemwood and bark from three different heights of Populus × euramericana “Guariento” were analyzed. The bark samples, especially from 4 and 8 meters height, contained much more extractives than the stemwood samples. The lipophilic extractives identified by Gas Chromatography–Mass Spectroscopy (GC-MS) were composed of five component groups (i.e. triglycerides, steryl esters, free fatty acids, sterols, and free fatty alcohols both in the stemwood and bark). Besides ferulic acid esters, α-amyrin and its esters, 4-hydroxycinnamic acid esters of fatty alcohols were also identified in the stemwood and bark. Small amounts of alkanes and oligomeric or polymeric material with higher molar mass than triglycerides were present only in the bark. Glycerides, mainly triglycerides, were the largest component group of the lipophilic extractives. The high proportion of short-chain fatty acids released after alkaline hydrolysis are beneficial when removing pitch particles or fatty acid soaps by dispersing and washing during pulping and papermaking. 相似文献
6.
R. Sastrawan J. Beier U. Belledin S. Hemming A. Hinsch R. Kern C. Vetter F.M. Petrat A. Prodi-Schwab P. Lechner W. Hoffmann 《Solar Energy Materials & Solar Cells》2006,90(11):1680-1691
As the dye solar cell (DSC) technology progresses from laboratory-scale to large-area applications, long-term stability is one major obstacle. Especially for large-area DSC modules, stability is often a matter of hermetic sealing both between cells and for the whole module. Here we suggest glass frit as sealing material. Glass frit is thermally, mechanically and chemically very stable and can be applied via screen printing.DSC modules of 30×30 cm2 with a glass frit as primary sealing material have been produced.It was shown that glass frit is applicable for the upscaling of the DSC technology to large areas. The thermal stability of the glass frit sealing and the integrated series connections was verified in a thermal cycling from −40 to 80 °C.The colouration process has been scaled up to 30×30 cm2 by pumping the dye solution through the module using only two filling holes. By heating the module to 70 °C the filling of the module with electrolytes based on high viscous ionic liquids was demonstrated. 相似文献
7.
8.
Evidence is presented that the apparent diffusion coefficient of one penetrant can be increased by competition from another penetrant for the same adsorption sites in polyester. The competition is governed by the relative diffusivities of the penetrants and their affinities for the adsorption sites. 相似文献
9.
10.
Kari Törrönen Kim Wallin Timo Saario Hannu Hänninen Rauno Rintamaa Jarl Forstén 《Nuclear Engineering and Design》1985
The effect of metallurgical variables on the two most important crack growth mechanisms - stable crack growth by environmentally assisted cyclic crack growth and unstable crack growth by cleavage - in light water reactor pressure vessel steels is evaluated. The analyses are based on micromechanisms of fracture and sensitivity analysis, when applicable. Metallurgical variables considered are non-metallic inclusions and carbides as well as other parameters through their effects on yield strength and other mechanical properties. 相似文献