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21.
Titanate whisker-reinforced polypropylene composites were prepared in a twin-screw extruder followed by injection molding. The whiskers were surface treated with tetrabutyl orthotitanate prior to blending. The static and dynamic mechanical properties, impact strength, and thermal properties of the composites were investigated. Static tensile measurements showed that the tensile strength and Young's modulus of the composites increased with increasing whisker content. However, the Izod impact tests indicated that the impact strength of longitudinal samples remained unchanged with the addition of whisker up to 10 wt %. Thereafter, it shows a continuous decrease with increasing whisker content. The thermogravimetric and dynamic mechanical tests demonstrated that the heat-resistance and thermooxidative stability for the composites also increased with increasing whisker content. Scanning electron microscopic observations revealed that the whiskers within the composites were oriented uniformly. The experimental data were compared with the well established mechanical models to evaluate the reinforcing efficiency. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 431–439, 1998 相似文献
22.
Maleic anhydride compatibilized blends of isotactic polypropylene (PP) and thermotropic liquid crystaline polymer (LCP) were prepared either by the direct injection molding (one-step process), or by twin-screw extrusion blending, after which specimens were injection molded (two-step process). The morphology and mechanical properties of these injection molded in situ LCP composites were studied by means of scanning electron microscopy (SEM), Izod impact testing, static tensile, and dynamic mechanical measurements. SEM observations showed that fine and elongated LCP fibrils are formed in the maleic anhydride compatibilized in situ composites fabricated by means of the one-step process. The tensile strength and modulus of these composites were considerably close to those predicted from the rule of mixtures. Furthermore, the impact behavior of LCP fibril reinforced composites was similar to that of the glass fiber reinforced polymer composites. On the other hand, the maleic anhydride compatibilized blends prepared from the two-step process showed lower mechanical performance, which was attributed to the poorer processing behavior leading to the degradation of PP. The effects of the processing steps, temperatures, and compatibilizer addition on the mechanical properties of the PP/LCP blends are discussed. 相似文献
23.
Composites based on isotactic polypropylene (PP) and sisal fiber (SF) were prepared by melt mixing and injection molding. The melt mixing characteristics, thermal properties, morphology, crystalline structure, and mechanical behavior of the PP/SF composites were systematically investigated. The results show that the PP/SF composites can be melt mixed and injection molded under similar conditions as the PP homo‐polymer. For the composites with low sisal fiber content, the fibers act as sites for the nucleation of PP spherulites, and accelerate the crystallization rate and enhance the degree of crystallinity of PP. On the other hand, when the sisal fiber content is high, the fibers hinder the molecular chain motion of PP, and retard the crystallization. The inclusion of sisal fiber induces the formation of β‐form PP crystals in the PP/SF composites and produces little change in the inter‐planar spacing corresponding to the various diffraction peaks of PP. The apparent crystal size as indicated by the several diffraction peaks such as L(110)α, L(040)α, L(130)α and L(300)β of the α and β‐form crystals tend to increase in the PP/SF composites considerably. These results lead to the increase in the melting temperature of PP. Moreover, the stiffness of the PP/SF composites is improved by the addition of sisal fibers, but their tensile strength decreases because of the poor interfacial bonding. The PP/SF composites are toughened by the sisal fibers due to the formation of β‐form PP crystals and the pull‐out of sisal fibers from the PP matrix, both factors retard crack growth. 相似文献
24.
The dynamic mechanical properties of A‐glass bead filled polypropylene (PP)/ethylene–propylene–diene monomers polymer (EPDM) ternary composites have been measured over a temperature range from −80 °C to 100 °C and at a fixed frequency of 1 Hz, using a dynamic mechanical analyser (DMA), to identify the effects of the filler content and its surface treatment with a silane coupling agent on the dynamic viscoelastic behaviour. The results show that the storage modulus (E′c) and loss modulus (E ″c) of these composites with 10% volume fraction of EPDM at 25 °C increase non‐linearly with increasing volume fraction of glass beads (ϕg). At the same test conditions, the E′c value of the PP/EPDM filled with pretreated glass beads is higher than that of the uncoated glass bead filled PP/EPDM system, especially at higher ϕg, while the difference in E ″c between both systems is very small. The mechanical damping for the former decreases with increasing ϕg, but the opposite is true for the latter. The glass transition temperature of these composites varies irregularly with ϕg. The dynamic complex viscosity increases nonlinearly with an increase of ϕg. In addition, the interfacial structure between the matrix and inclusions has been observed by means of a scanning electron microscope. © 1999 Society of Chemical Industry 相似文献
25.
Mechanical and thermal behavior of polycarbonate composites reinforced with aluminum borate whiskers
Inorganic aluminum borate (Al18B4O33) whisker was employed in this study to reinforce polycarbonate (PC). The composites were prepared in a single-screw extruder, followed by injection molding. The whiskers were pretreated with tetrabutyl orthotitanate prior to compounding. The tensile, dynamic mechanical, impact, and thermal properties of the composites were studied. Tensile results showed that the modulus of PC–Al18B4O33 composites increased markedly with increasing whisker content. However, the tensile stress of the composite decreased slightly with the addition of 5 wt % whisker; thereafter, it increased slowly with increasing whisker content. Differential thermal analysis and thermogravimetric measurements showed that the glass transition temperature (Tg) and 5% weight loss temperature (T−5%) of the composite shift rapidly to lower temperature regimes with the addition of Al18B4O33 whiskers up to 10 wt %. Thereafter, the Tg and T−5% of PC–Al18B4O33 composites tended to decrease slowly with increasing whisker content. The mechanical and thermal properties of PC–Al18B4O33 composites were compared with those of PC–potassium titanate (K2Ti6O13) whisker composites. The reinforcing effect of Al18B4O33 and K2Ti6O13 whiskers on PC was discussed and contrasted. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2247–2253, 1999 相似文献
26.
Potassium titanate (K2Ti6O13) whisker treated with tetrabutyl orthotitanate was used to improve the mechanical and thermal properties of the poly(acrylonitrile–butadiene–styrene) (ABS) copolymer. The composites were prepared in a twin‐screw extruder followed by injection molding. Static tensile measurements showed that both the modulus and breaking stress of ABS/K2Ti6O13 composites increase considerably with increasing whisker content; the strain at break of ABS was almost unaffected by the incorporation of a whisker content up to 15 wt %. Izod impact tests indicated that the composites showed a decrease in the impact strength with increasing whiskers content. Thermogravimetric analysis showed that the K2Ti6O13 whisker additions have little effect on the thermooxidative stability of ABS. Scanning electron microscopic observations revealed that the whiskers were aligned along the melt‐flow direction in the thin surface layer, whereas the whiskers were oriented randomly as well as perpendicular to the injection direction in the thick core region of the composites. The Tsai–Halpin equation was used to evaluate the moduli of the ABS/K2Ti6O13 composites. The theoretical calculations generally correlated well with the experiment data by assuming K2Ti6O13 whiskers to have an aspect ratio of 12. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2985–2991, 1999 相似文献
27.
Ternary in situ polycarbonate (PC)/polybutylene terephthalate (PBT)/liquid crystalline polymer (LCP) composites were prepared by injection molding. The liquid crystalline polymer used was a versatile Vectra A950. The matrix of composite was composed of PC/PBT 60/40 by weight. A solid epoxy resin (bisphenol type‐A) was used as a compatibilizer for the composites. Dynamic mechanical analysis (DMA) showed that epoxy resin was effective to improve the compatibility between PC and PBT, and between PC/PBT and LCP, respectively. Tensile tests revealed that the stiffness of composites shows little change with the LCP content up to 10 wt %. Above this concentration, the stiffness tended to increase with increasing LCP content. Furthermore, the tensile strengths appeared to increase with increasing LCP content, and their values were close to those predicted from the rule of mixtures. Scanning electron microscopic examination showed that LCP ribbons and short fibrils were developed in the composites containing LCP content ≤10 wt %. However, fine and elongated fibrils were formed in the skin and core sections of the composites when the LCP content reached 25 wt % and above. Thermogravimetric analysis indicated that the thermooxidative stability of the PC/PBT 60/40 blend tended to improve with increasing LCP content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1827–1835, 1999 相似文献
28.
Hydroxyapatite (HA) and its nanocomposites reinforced with low loading levels of multiwalled carbon nanotubes (MWNTs) are prepared by spark plasma sintering process. The structure, morphology, and hardness of sintered HA and MWNT/HA nanocomposites are characterized by means of X‐ray diffraction (XRD), scanning electron microscopy and nanoindentation techniques. XRD results show that the orientation of crystallographic planes of sintered HA are highly related to the applied pressure direction. The perpendicular section of sintered MWNT/HA nanocomposites shows predominantly oriented HA a‐and b‐planes while the parallel section displays a dominant c‐plane orientation. The hardness of MWNT/HA nanocomposites improves considerably with increasing MWNT content. 相似文献
29.
A facile micelle precursor having cyclohexane/ethanol/cetyl trimethyl ammonium bromide/aqueous phase was treated hydrothermally to form nanohydroxyapatite. The synthesized products were characterized by means of X-ray diffraction, thermogravimetric analysis, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the synthesized products display the crystalline structure and vibration modes of hydroxyapatite. Transmission electron micrograph revealed that nanohydroxyapatite exhibits elongated rod morphology with large aspect ratios. Nanohydroxyapatite prepared from a surfactant of 1.25 millimole showed good thermal stability at 1000 degrees C on the basis of thermogravimetric analysis. Simulated body fluid immersion test indicated that an apatite layer can be readily deposited on the nanohydroxyapatite surface demonstrating its good bio-resorbability. 相似文献
30.
Rong Hua Zhang De An Shi Chi Pong Tsui Chak Yin Tang Sie Chin Tjong Robert Kwok Yiu Li 《Polymer Engineering and Science》2011,51(2):403-410
Compatibilized polypropylene (PP)/polyamide (PA6) blends with and without β nucleating agent (β‐NA) are prepared, and are designated as Blend‐0.3 and Blend‐0, respectively. The melting and crystallization characteristic of the blends crystallized under different cooling rates and different crystallization temperatures are studied. It is observed that high β‐PP content can be developed in Blend‐0.3 only at slow cooling rates (<5°C/min), whereas high α‐PP content is formed at fast cooling rates. Isothermal crystallization analysis of Blend‐0 indicates that PA6 is an effective NA for α‐PP in the lower temperature range, whereas the α‐nucleating effect disappears in the higher temperature range. Blend‐0.3 can, therefore, be viewed as a system containing both α‐ and β‐NAs, simultaneously. PA6 is competing with β‐NA in inducing PP crystallization. Under the normal injection of Blend‐0.3, the melt will be cooled through the higher temperature that favors the effectiveness of β‐NA rapidly because of the faster cooling rate. However, the α‐nucleation effect from PA6 predominate at the lower temperature. This explains the difficulty in obtaining high β‐PP content in Blend‐0.3 from injection molding. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers 相似文献