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51.
Weakly useful sequences 总被引:1,自引:0,他引:1
Stephen A. Fenner Jack H. Lutz Elvira Mayordomo Patrick Reardon 《Information and Computation》2005,197(1-2):41-54
An infinite binary sequence x is defined to be
- (i) strongly useful if there is a computable time bound within which every decidable sequence is Turing reducible to x; and
- (ii) weakly useful if there is a computable time bound within which all the sequences in a non-measure 0 subset of the set of decidable sequences are Turing reducible to x.
Keywords: Computability; Randomness; Random sequence; Computational depth; Logical depth; Computable measure; Resource-bounded measure; Useful; Weakly useful 相似文献
52.
This paper describes how morphology of PVC changes in the Brabender mixing head. At the range of temperatures used for PVC processing, the Brabender torque-time curve shows minimum torque and maximum torque. The minimum torque is associated with a breakdown of 150 μm PVC grains and 10 μm agglomerates resulting in the release of the 1μm primary particles. The torque increases from minimal interaction between primary particles to the point where primary particles agglomerate at maximum torque so that fibriles can be formed when PVC samples are swollen in acetone and sheard. Further heating reduces the viscosity resulting in lower torque even though residual primary particles still exist with much particle to particle interaction. Primary particle structure disappears at about 215° C with complete melting. 相似文献
53.
Luisa Torsi Francesco Marinelli M. Daniela Angione Antonio Dell’Aquila Nicola Cioffi Elvira De Giglio Luigia Sabbatini 《Organic Electronics》2009,10(2):233-239
Contact effects in organic thin-film transistors (OTFTs) sensors are here investigated specifically respect to the gate field-induced sensitivity enhancement of more than three orders of magnitude seen in a DHα6T OTFT sensor exposed to 1-butanol vapors. This study shows that such a sensitivity enhancement effect is largely ascribable to changes occurring to the transistor channel resistance. Effects, such as the changes in contact resistance, are seen to influence the low gate voltage regime where the sensitivity is much lower. 相似文献
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Guilherme Ferreira Sumita Goswami Suman Nandy Luis Pereira Rodrigo Martins Elvira Fortunato 《Advanced functional materials》2020,30(5)
Sustainable and safe energy sources combined with cost effectiveness are major goals for society when considering the current scenario of mass production of portable and Internet of Things (IoT) devices along with the huge amount of inevitable e‐waste. The conceptual design of a self‐powered “eco‐energy” smart card based on paper promotes green and clean energy, which will bring the zero e‐waste challenge one step closer to fruition. A commercial raw filter paper is modified through a fast in situ functionalization method, resulting in a conductive cellulose fiber/polyaniline composite, which is then applied as an energy harvester based on a mechano‐responsive charge transfer mechanism through a metal/conducting polymer interface. Different electrodes are studied to optimize charge transfer based on contact energy level differences. The highest power density and current density obtained from such a paper‐based “eco‐energy” smart card device are 1.75 W m?2 and 33.5 mA m?2 respectively. This self‐powered smart energy card is also able to light up several commercial light‐emitting diodes, power on electronic devices, and charge capacitors. 相似文献
56.
Glass fiber reinforced PVC has several distinctive and useful properties. Its tensile strength can be twice that of unreinforced PVC. Excellent coupling of the glass fibers to the PVC matrix is required for good retention of tensile strength when exposed to warm water, Its modulus can be twice that of unreinforced PVC and equal to that of wood. PVC's high load carrying capability is not significantly increased to higher temperatures by adding glass fibers as judged by its 264 psi heat deflection temperature. However, by changing the polymeric matrix, glass reinforced vinyl with an increased HDT of 86°C has been produced for higher use temperature. The coefficient of linear thermal expansion of PVC can be cut in half by the addition of glass fibers and has a coefficient equal to that of aluminum. Glass fiber reinforced PVC has exceptionally good resistance to crack propagation and resists shattering as judged by sawing, punching, stapling, and hammering. When properly formulated for weathering resistance, glass fiber reinforced PVC has good color retention, impact retention, and outstanding dimensional stability. As for all glass fiber reinforced plastics, processing equipment must be built for high abrasion resistance for long economical manufacturing runs. 相似文献
57.
Ofelia Mora Jos L Romano Elvira Gonzlez Felipe J Ruiz Armando Shimada 《Journal of the science of food and agriculture》1999,79(2):273-276
Two experiments were conducted to determine the rumen fluid disappearance rates (kd) of β‐carotene, lutein, total carotene and total xanthophyll from lucerne (Medicago sativa) hay, in two ruminant species: Brahman steers (fat‐pigmenting) and Granadine goats (non‐pigmenting). Within species, the in vitro and the in situ methods were compared. The concentration of carotenoid compounds was determined by spectrophotometry and high performance liquid chromatography. The in vitro disappearance trends were linear for all compounds (P<0.01). β‐carotene kd were 0.13 and 0.37; lutein, 0.20 and 0.25; total carotene, 0.20 and 0.62 and total xanthophyll, 0.30 and 0.77 h −1 for steers and goats, respectively. The in situ disappearance trends were quadratic (P<0.01). Dry matter kd were 1.9 and 1.5% h−1; cellular content, 2.0 and 2.3; β‐carotene, 2.5 and 1.2; lutein, 2.5 and 1.5; total carotene, 2.2 and 1.0 and total xanthophyll, 2.1 and 1.1% h−1 for steers and goats, respectively. The large disappearance rates of carotenoids observed in the in situ method vs the virtual absence of disappearance in the in vitro method in both species, can be related to the dry matter and cellular content kd. These results suggest that carotenoids disappear probably by joining the cellular content and not by their direct destruction or by attack from the ruminal microorganisms, and the ruminal disappearance is independent of the species studied. © 1999 Society of Chemical Industry 相似文献
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