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701.
The currently used composites produced by classical sintering methods are characterised by numerous limitations due to the difficulties in combining different materials with extreme properties. One of the ways to overcome these limitations is in the use of modern sintering methods, including the high pressure-high temperature process. This study describes the composite materials based on 316L austenitic steel reinforced with titanium diboride and examines the effect of sintering conditions on the mechanical properties and microstructure of sintered composites. It has been found that the key parameter in the manufacture of composites with optimal properties is the sintering time and temperature, while martensitic transformation taking place in the composite matrix can be controlled by the properly selected pressure applied during the sintering process. 相似文献
702.
Aleksandra Pacuła Robert P. Socha Piotr Pietrzyk Małgorzata Zimowska Małgorzata Ruggiero-Mikołajczyk Dariusz Mucha Robert Kosydar Grzegorz Mordarski 《Journal of Materials Science》2018,53(16):11292-11314
Two sets of the carbon materials containing nitrogen and cobalt were prepared by simultaneous carbonization of CH3CN and decomposition of Co–Al layered double hydroxides (LDHs) (of Co/Al atomic ratios equal to 2 or 3) at 600, 700 and 800 °C followed by treatment with HCl. The physicochemical features of the samples were characterized by means of XRD, TG, EA, XPS, XRF, FT-IR, SEM, Raman spectroscopy and nitrogen sorption. All of the composites were active in oxygen reduction reaction (ORR) in alkaline medium. Their ORR behaviour was determined by the contribution of structural defects and N-doping in graphitic lattice. The beneficial effect of metallic cobalt encapsulated inside the N-CNTs on the ORR performance was also taken into consideration. The studies showed that the likelihood of the existence of Co–N–C species and their participation in ORR seemed to be suppressed by the formation of CoAl2O4. The samples prepared at 600 and 700 °C appeared to be more active in ORR than that obtained at 800 °C. The number of electrons involved in ORR (2.89, 2.82 and 2.77) decreased with increasing synthesis temperature for the samples prepared with LDHs of Co/Al?=?2 as a consequence of lowering concentration of nitrogen (3.2, 2.4 and 1.5 wt%), in particular diminishing contribution of pyridinic nitrogen, and decreasing exposure of graphitic edges (ID1/IG?~?2.6, 2.0 and 1.0). The ORR performance of the samples prepared with LDHs of Co/Al?=?3 is comparable to that of the corresponding samples prepared with LDHs of Co/Al?=?2. 相似文献
703.
DNA computing, sticker systems, and universality 总被引:14,自引:0,他引:14
Lila Kari Gheorghe Păun Grzegorz Rozenberg Arto Salomaa Sheng Yu 《Acta Informatica》1998,35(5):401-420
We introduce the sticker systems, a computability model, which is an abstraction of the computations using the Watson-Crick complementarity as in Adleman's
DNA computing experiment, [1]. Several types of sticker systems are shown to characterize (modulo a weak coding) the regular
languages, hence the power of finite automata. One variant is proven to be equivalent to Turing machines. Another one is found
to have a strictly intermediate power.
Received: 10 October 1996 / 16 April 1997 相似文献
704.
O. A. Rozenberg E. A. Pashchenko A. G. Mamalis 《Journal of Materials Engineering and Performance》2012,21(6):1099-1105
Despite being one of the oldest objects of materials science, powder structures still are of great interest. Significant information can be provided by analysis of interactions between particles in powder medium. This article discusses the experimental results from measurements of dynamics of probing solvent removal from pore volume, linked to interparticle contacts. The concept of topological uniformity of pore space in powder bodies is formulated and distributions of three-dimensional interparticle contacts by volumes are analyzed. 相似文献
705.
Artur Podhorodecki Grzegorz Zatryb Lukasz W Golacki Jan Misiewicz Jacek Wojcik Peter Mascher 《Nanoscale research letters》2013,8(1):98
Silicon nanocrystals embedded in a silicon-rich silicon oxide matrix doped with Er3+ ions have been fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition. Indirect excitation of erbium photoluminescence via silicon nanocrystals has been investigated. Temperature quenching of the photoluminescence originating from the silicon nanocrystals and the erbium ions has been observed. Activation energies of the thermally activated quenching process were estimated for different excitation wavelengths. The temperature quenching mechanism of the emission is discussed. Also, the origin of visible emission and kinetic properties of Er-related emission have been discussed in details. 相似文献
706.
Alicja Nowaczyk Magdalena Kowalska Jacek Nowaczyk Grzegorz Grzek 《International journal of molecular sciences》2021,22(11)
The year 2021 is the 100th anniversary of the confirmation of the neurotransmission phenomenon by Otto Loewi. Over the course of the hundred years, about 100 neurotransmitters belonging to many chemical groups have been discovered. In order to celebrate the 100th anniversary of the confirmation of neurotransmitters, we present an overview of the first two endogenous gaseous transmitters i.e., nitric oxide, and carbon monoxide, which are often termed as gasotransmitters. 相似文献
707.
Highly graphitic carbon nanocoils were synthesised from the catalytic graphitization of carbon spherules obtained by the hydrothemal treatment of different saccharides (sucrose, glucose and starch). This nanostructured carbon was characterized by X-ray power diffraction, N2 adsorption and microscopy techniques (SEM and TEM). The carbon nanocoils were used as a support for PtRu nanoparticles, which were well-dispersed over the carbon surface. This catalytic system was investigated for use as an electrocatalyst for methanol electrooxidation in an acid medium. The experiments were carried out at two working temperatures (25 °C and 60 °C). It was found that the carbon nanocoils supporting PtRu nanoparticles exhibit a high catalytic activity, which is even higher than that of conventional carbon supports (Vulcan XC-72R). We believe that the high electrocatalytic activity of the carbon nanocoils presented here is due to the combination of a good electrical conductivity, derived from their graphitic structure, and a wide porosity that allows the diffusional resistances of reactants/products to be minimized. 相似文献
708.
709.
Martin Peter Elsner Grzegorz Ziomek Andreas Seidel‐Morgenstern 《American Institute of Chemical Engineers》2009,55(3):640-649
The focus of this work is to study the enantioseparation of conglomerate forming systems using an innovative configuration for preferential crystallization. Two batch crystallizers are coupled by an exchange of their liquid phases. In each vessel one of the two enantiomers is seeded initially and crystallizes subsequently. Compared with conventional single batch crystallization the exchange of the crystal free liquid phases between two crystallizers leads to an increase of the concentrations of the preferred enantiomers and therefore to an increase of the driving forces for the crystallization. This enhances the productivity of the process compared with the conventional operation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
710.
A. V. Agranovskii G. N. Korol'kov A. V. Rozenberg V. A. Sborshchikov 《Measurement Techniques》1999,42(11):1075-1079
The underwater sound field in the vicinity of interference maxima can be approximated locally by a quasi-plane wave. The sensitivity
measurement technique discussed in the article calls for measurements to be performed at times when the calibrated and the
standard hydrophones reside in the zone of an interference maximum of the sound field generated by a moving radiator. The
motion of the latter can be utilized to formulate a simple dynamic algorithm for monitoring the entry of acoustic transducers
into the zone of a maximum of the sound field.
Translated from Izmeritel'naya Tekhnika, No. 11, pp. 49–52, November, 1999. 相似文献