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排序方式: 共有138条查询结果,搜索用时 8 毫秒
41.
Devon M. Samuel Nathaniel Inumerable Andrew Stumpf Waltraud M. Kriven 《International Journal of Applied Ceramic Technology》2023,20(1):475-486
We fabricated 50.8-mm cube-shaped samples of metakaolin geopolymer (GP) composites with various additives chosen to increase or decrease the thermal conductivity of the composite. Sodium-based GP (NaGP) and GP composites were more conductive than potassium-based GP (KGP) composites for a given phase fraction of filler, but the maximum amount of filler phase was higher with KGP due to the lower viscosity of the KGP mixture. The highest thermal conductivity achieved was about 8 W/m K by KGP + 44-vol% graphite flakes, whereas NaGP + 27 vol% graphite flakes reached 4.7 W/m K. The thermal conductivity was strongly affected by the moisture remaining in the composite, which appeared to have a greater effect at higher filler content. On the other hand, the size of alumina particles (6, 40, or 120 μm) did not have any apparent effect on thermal conductivity for the same filler content. Larger particles caused less change in mixture viscosity, though, thus permitting incorporation of higher filler phase fractions and therefore higher thermal conductivity. 相似文献
42.
This study explores the viability of fiberglass‐geopolymer composites as an intermediate temperature structural ceramic composite. E‐glass fibers are cheap, readily available, resistant to heat, electricity and chemical attack. Geopolymers are refractory and can be processed at room temperature. However, pure geopolymers have low tensile strength and fracture toughness, as is typical of ceramics. In this work, tensile and flexure properties of metakaolin‐based sodium and potassium geopolymers reinforced with E‐glass leno weaves were measured and the data was analyzed by Weibull statistics. The average tensile and flexural strengths for sodium geopolymer reinforced with E‐glass leno weaves were 39.3 ± 7.2 MPa and 25.6 ± 4.8 MPa, respectively. For potassium geopolymer reinforced with E‐glass leno weaves, the average tensile and flexural strengths were 40.7 ± 9.9 MPa and 15.9 ± 4.0 MPa, respectively. The composites were heat treated for one hour at two temperatures, 300°C and 550°C and their flexure properties were studied at room temperatures. The average flexural strengths for sodium geopolymer reinforced with E‐glass leno weaves were reduced to 6.6 ± 1.0 MPa after heat treatment at 300°C, and 1.2 ± 0.3 MPa after heat treatment at 550°C, respectively. For potassium geopolymer reinforced with E‐glass leno weaves, the average flexural strengths were 6.1 ± 1.5 MPa and 1.3 ± 0.3 MPa after heat treatment at 300°C and 550°C, respectively. SEM and EDS were performed to observe the fiber‐matrix interface. XRD was done to check if the geopolymer was amorphous as expected. 相似文献
43.
The use of LaPO4 as a weak interface in composites for high temperature applications was investigated using tape-cast laminates and fiber model systems. Three laminates were fabricated with LaPO4 as one component and Al2O3, Y3Al5O12 or LaAl11O18 as the other. The chemical compatibility between the different components of the laminates, as well as the mechanical responses to flexural deformation and the propagation of indentation cracks, were examined. Two fiber model systems (Al2O3 fiber/LaPO4 coating/Al2O3 matrix and Y3Al5O12 fiber/LaPO4 coating/Al2O3 matrix) were studied by fiber pushout tests to measure the interfacial shear strengths. The interfacial shear strengths were calculated by the linear and shear-lag approaches for different embedded fiber lengths. The results suggest that Y3Al5O12 fiber-reinforced composites with LaPO4 coatings have potential as high temperature materials in oxidizing environments. 相似文献
44.
H. Marx Bernhard Brunner Waltraud Weinzierl Rudolf Hoffmann Andreas Stolle 《European Food Research and Technology》1997,204(4):282-286
Taking into account aspects of meat quality and animal welfare, three methods of stunning fish were compared: a manual technique
(blow on the head, stab in the neck), one using electricity and one using CO2. The following results were obtained using eel (n=72), carp (n=120) and trout (n=54). From the viewpoint of animal welfare, the effects on the fish were judged. Excitation and mucus secretion as well as
the time taken for the fish to be anaesthetized were recorded. With manual and electrical stunning, all fish were anaesthetized
almost immediately, while using CO2 it took 3.2 min (trout), 9.2 min (carp) and 109.7 min (eel) on average. After slaughter and after 3 and 8 days of storage
on ice, the fish meat quality parameters, i.e. pH value, water-holding capacity and rigor mortis, were measured. CO2 stunning gave rise to the lowest pH values and water-holding capacities. Rigor mortis in carp and eel advanced the most.
Testing of raw and prepared fish was performed by a panel assessing organoleptic properties. In many cases, fish anaesthetized
manually were ranked to be better than those in the other groups.
Received: 4 June 1996 / Revised version: 5 July 1996 相似文献
45.
We consider an incomplete repair model, that is, the impact of repair is not minimal as in the homogeneous Poisson process and not “as good as new” as in renewal processes but lies between these boundary cases. The repairs are assumed to impact the failure intensity following a virtual age process of the general form proposed by Kijima. In previous works field data from an industrial setting were used to fit several models. In most cases the estimated rate of occurrence of failures was that of an underlying exponential distribution of the time between failures. In this paper, it is shown that there exist maintenance schedules under which the failure behavior of the failure-repair process becomes a homogeneous Poisson process. 相似文献
46.
Chestnut Ronald Grasmueck Barbara Hadsell Richard Krieger Edith Lebershausen Waltraud Lowsky Juergen Plappert Winfried Richter Matthias Rother Hans-Peter Siart Otto Thieme Ruth 《IEEE transactions on nuclear science》1979,26(4):4417-4421
An integrated facility-wide system for nuclear physics data acquisition is described. Four PDP-11/45's connected via a SYSTEM/7 to an IBM/370-168 are used in the system. User programs specifying spectrum definition and analysis logic are written using macros and are expanded into PL11 or PL/1, depending on the subsystem into which the program is to be linked. Both subsystems also use a common command set. 相似文献
47.
48.
Synthesis and Characterization of Silicon Carbide Powders Converted from Metakaolin‐Based Geopolymer
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Cengiz Bagci Gregory P. Kutyla Kevin C. Seymour Waltraud M. Kriven 《Journal of the American Ceramic Society》2016,99(7):2521-2530
Silicon carbide (SiC) ceramic powders were synthesized by carbothermal reduction in specific geopolymers containing carbon nanopowders. Geopolymers containing carbon and having a composition M2O·Al2O3·4.5SiO2·12H2O+18C, where M is an alkali metal cation (Na+, K+, and Cs+) were carbothermally reacted at 1400°C, 1500°C, and 1600°C, respectively, for 2 h under flowing argon. X‐ray diffraction and microstructural investigations by SEM/EDS and TEM were made. The geopolymers were gradually crystallized into SiC on heating above 1400°C and underwent significant weight loss. SiC was seen as the major phase resulting from Na‐based geopolymer heated to ≥1400°C, even though a minor amount of Al2O3 was also formed. However, phase pure SiC resulted with increasing temperature. While a slight increment of the Al2O3 amount was seen in potassium geopolymer, Al2O3 essentially replaced cesium geopolymer on heating to 1600°C. SEM revealed that SiC formation and a compositionally variable Al2O3 content depended on the alkaline composition. Sodium geopolymer produced high SiC conversion into fibrous and globular shapes ranging from ~5 μm to nanosize, as seen by X‐ray diffraction as well as SEM and TEM, respectively. 相似文献
49.
Christian J. Espinoza Santos Teng‐Sing Wei Bumrae Cho Waltraud M. Kriven 《Journal of the American Ceramic Society》2013,96(11):3379-3388
The purpose of this study was to improve the forming techniques and parameters for producing spherical ceramic beads using sodium alginate as a sacrificial template. This process has the potential of producing beads for applications such as stress‐wave propagation of granular media, beads for milling, catalyst support, and encapsulation of drugs, as well as water filtration. This simple, inexpensive, and environmentally friendly approach to producing spherical ceramic beads using bead‐forming equipment occurs when a flat‐tipped needle produces droplets that cross‐link, forming green bodies upon contact with CaCl2 solution. An exchange of ions takes place where sodium alginates substitute their Na+ for Ca2+ to form semirigid bodies. Spherical ceramic beads using 50 wt% alumina suspension with 0.04 wt% polyacrylate dispersant are produced when: the viscosity of the slurry is below 0.3 Pa·s, the surface tension of the gelling solution is below 50 mN·m, and the distance of the nozzle tip to the reacting solution is ~3 cm. This approach for producing ceramic beads using alginates will allow its use for any type of ceramic material, changing its chemical composition, and controlling the microstructure and shape of the beads. 相似文献
50.
介绍了Schlafllorst公司开发的Fancynation花式装置在Autocoro 360转杯纺纱机上的应用。模块化设计的花式装置可适应小批量订货的需求。 相似文献