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981.
Synthesis, Characterization, and Antibacterial Action of Hollow Ceria Nanospheres with/without a Conductive Polymer Coating 总被引:1,自引:0,他引:1
Ioannis A. Kartsonakis Penelope Liatsi Ioannis Daniilidis George Kordas 《Journal of the American Ceramic Society》2008,91(2):372-378
Hollow ceria nanospheres were synthesized using anionic polystyrene lattices which were prepared by emulsion polymerization of styrene using potassium persulfate as the initiator. These anionic colloidal particles were dispersed in water in the presence of poly(vinylpyrrolidone) and mixed with aqueous solutions of cerium (III) acetylacetonate [Ce(acac)3 ]. Subsequently, hollow nanospheres of cerium compounds were obtained by calcination of the coated polystyrene lattices at an elevated temperature in air. The hollow ceria nanospheres were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential thermal analysis. The hollow ceria nanospheres were coated with conductive polymers (polyaniline and polypyrrole) via an electropolymerization process. Moreover, the antibacterial action of illuminated hollow ceria nanospheres and hollow ceria nanospheres coated with conductive polymers (CPCeO2 ) on a pure culture of Escherichia coli was studied. A decrease of E. coli concentration was observed after illumination of bacteria in the presence of hollow ceria nanospheres and CPCeO2 . 相似文献
982.
George W. Scherer 《Cement and Concrete Research》2008,38(3):368-378
In a standard flow-through permeameter, a hydrostatic head is applied to one side of a sample and the flux of fluid through the sample is measured. In this paper, we apply poromechanics to calculate the evolution of the pressure distribution and the flux through the sample. We allow for negative capillary pressure in the pores at the start of the experiment (owing to self-desiccation during hydration of cement), as well as entrapped air. The time required to reach steady state flow can increase by an order of magnitude by the presence of 1 vol.% of air in the pore liquid; the delay increases as the applied pressure decreases. 相似文献
983.
Demetrios C. Papamantellos George N. Angelopoulos Konstantinos T. Mavrommatis 《国际钢铁研究》1990,61(12):598-602
A mathematical model of the electro-reduction furnace process (ERF process), for the production of ferronickel from laterite ores, has been tested at Larco's metallurgical plant at Larymna Greece. The theoretical predictions for the progress of the nickel reduction have been compared with the operational results. The tests were carried out in the ERF no. 2 of Larco's plant. The influence of the main process variables on the nickel recovery and nickel losses in the ERF slags have been investigated in conjunction with the variation of the analysis of the feed and the nickel content of the metal bath. The further application of the model to the metallurgical practice is discussed. According to the predictions of the model the further development of the process in the direction of the production of low-nickel ferronickel (Ni < 15%) is analyzed. The advantages of the production of low-nickel ferronickel are presented and the possibility of its straight conversion to nickel-bearing steel-grades is discussed. 相似文献
984.
George H. Klinger Evone S. Ghali Stuart C. Porter Joseph B. Schwartz 《Drug development and industrial pharmacy》1990,16(9):1473-1490
The objective of this work was to incorporate an ethylcellulose-based controlled-release coating suspension (Surelease, Colorcon) within a tablet matrix to provide a release controlling mechanism. Anhydrous theophylline, chlorpheniramine maleate, and acetaminophen were selected as model drug entities. Surelease dispersion was incorporated as the granulating agent either to the drug entity alone or to a blended mixture of drug and filler. Control batches included simple aqueous granulations and direct compression mixtures. Tablets were prepared on a single stroke tablet press. Dissolution was performed by the USP Method I (rotating basket) in purified water for the granulations and the resulting tablets. The uncompressed granulations did not exhibit prolonged release. In general, tablets prepared with the polymer suspension as the granulating agent were non-disintegrating, and exhibited slower dissolution than the control tablets. Release profiles were affected by drug concentration and excipient levels. By the dissolution method selected, complete drug release for the various formulations ranged from less than 1 hour to greater than 12 hours. The use of the polymer dispersion appears to enhance the processing characteristics of some materials, and to provide the formulator with control over drug release. 相似文献
985.
George Ruben Ph.D. 《Microscopy research and technique》1986,4(1):75-75
986.
987.
Piotr D. Moncarz John C. Shyne George K. Derbalian 《Canadian Metallurgical Quarterly》1987,1(3):168-187
The paper describes the analysis of failures of a 108‐in. (2.74 m) diameter steel pipe water main. Total pipe separations occurred because of large unrelieved thermal stresses and stress amplification caused by the eccentricity of the welded bell‐and‐spigot joints. The pipeline designer ignored these aspects in his design, thus grossly underestimating the stresses in the pipe. This could easily have been recognized by performing an elementary longhand calculation. The failure analysis described in this paper demonstrates that the asdesigned pipeline was incapable of safely withstanding even the incorrectly defined design conditions. The designer attributed the failures to low toughness of the bell steel. Conversions of Charpy impact test data and J‐integral analysis of compact tension test data are used to demonstrate that the steel had normal fracture toughness. Nonlinear finite element stress analysis and elasticplastic fracture mechanics demonstrate that for the measured range of fracture toughness the failures were inevitable. 相似文献
988.
H. Padma Kumar C. Vijayakumar Chandy N. George Sam Solomon R. Jose J.K. Thomas J. Koshy 《Journal of Alloys and Compounds》2008,458(1-2):528-531
Barium zirconate (BaZrO3) nanoparticles synthesized by a self-sustained single-step combustion process is reported in this paper. In this process, a phase pure nanopowder of BaZrO3 has been obtained by the combustion of an aqueous solution containing Ba and Zr ions by using citric acid as complexing agent and liquor ammonia as fuel, thus giving rise to phase pure BaZrO3 nanopowder in a single-step combustion without any further calcination. The X-ray diffraction studies have shown that the as-prepared powder was single phase, crystalline, and has a cubic perovskite structure (ABO3) with a lattice constant a = 4.19 Å. The average particle size calculated from FWHM is 30 nm. The phase purity of BaZrO3 nanopowder has been examined using differential thermal analysis (DTA), thermo gravimetric analysis (TGA) and Fourier transform of infrared spectroscopy (FTIR). The transmission electron microscopic investigation has shown that the particle size of the as-prepared powder was in the range 30–50 nm with a mean size of 40 nm. The nano BaZrO3 has been sintered to a density of 99% of the theoretical density at 1650 °C in 2 h without the use of any sintering aids. The morphology of the sintered pellets has been studied with scanning electron microscopy (SEM). The dielectric constant (r) and loss factor (tan δ) values obtained at 10 MHz for a well-sintered barium zirconate pellet has been found to be 32.2 and 1 × 10−4, respectively, at room temperature. 相似文献
989.
A partnership has been developed linking the United States Military Academy and Special People in the Northeast, a non-profit agency for the mentally and physically handicapped children and adults based in Philadelphia. The present work documents a student design team's design and construction of a ticket-tearing device for a young man in the advanced stages of cerebral palsy and concludes with an evaluation of the entire process. 相似文献
990.
Three bored piles were built and tested at the National Geotechnical Experimentation Sites, at Texas A&M University, to gather data on the reliability of large-strain dynamic methods to predict the static capacity of bored piles. The three piles had a nominal diameter of 0.915 m, a nominal length of 10 m, and some planned and unplanned defects. The piles were first subjected to a static load test and then four companies were asked to perform dynamic tests—namely, Statnamic and drop weight tests—and predict the static load test results. The paper shows the comparison between predicted and measured results. 相似文献