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31.
Jifei Jia Eishi Tanabe Peng Wang Kouichi Ito Hiroyuki Morioka Ye Wang Tetsuya Shishido Katsuomi Takehira 《Catalysis Letters》2001,76(3-4):183-192
A solid phase crystallization (spc) method was applied for the preparation of SrTiO3-supported Ni catalysts and compared to the impregnation (imp) method. spc-Ni0.2/SrTiO3 has highly dispersed and stable Ni metal particles resulting in higher activity and higher sustainability against coking than imp-Ni0.2/SrTiO3 in the partial oxidation of CH4. Both catalysts were tested for the CH4 pyrolysis in order to elucidate the catalytic nature against coking of spc-Ni0.2/SrTiO3. The amount of carbon and the rate of H2 formation were similar over both catalysts at both 773 and 1073 K. On both catalysts, CH4 continuously decomposed at 773 K, while the rate of CH4 pyrolysis quickly decreased at 1073 K. Fibrous carbons grew up with a Ni metal particle on the tip of the fiber at 773 K, while carbon balls and short carbon fibers with a Ni metal particle encapsulated inside formed and no sufficient growth of the fiber was observed at 1073 K. The carbon species formed at 773 K was hydrogenated completely to CH4 around 873 K, while the hydrogenation of that formed at 1073 K needed higher temperature around 1073 K. However, the carbon species formed on both the catalysts at either 773 or 1073 K was completely oxidized around 773 K. Thus, judging from the anti-coking nature, the behaviors in the CH4 pyrolysis are similar over both catalysts, nonetheless spc-Ni0.2/SrTiO3 was far superior to imp-Ni0.2/SrTiO3 in the CH4 oxidation. It is likely that the high sustainability against coking of spc-Ni0.2/SrTiO3 is not due to its intrinsic nature suppressing the coking but due to its high activity of reforming which can quickly eliminate the carbon formed on the catalyst surface. 相似文献
32.
A total of fifteen saturated fatty acid esters were newly identified from the secretions of an unidentified Anaulaciulus sp. (Julida: Julidae). The fatty acid components of the esters were composed of normal chain acids (from C10 to C14) and of branched chain acids (from iso-C12 to iso-C15 and anteiso-C15). The alcohol moieties were all composed of normal chain alcohols varying from n-butanol to n-octanol. The most abundant component found in the total esters was n-hexyl laurate (64.7%). Novel compounds identified from the millipede secretion extracts include six branched iso- and anteiso-fatty
esters, an odd-numbered C11-fatty acid ester, a C13-fatty acid ester, and a C7-alcohol ester, all of which were previously undescribed natural products. In addition, a characteristic mixture of benzoquinones,
such as 2-methyl-1,4-benzoquinone, 2-methoxy-3-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, 2-methoxy-6-methyl-1,4-benzoquinone,
and 2,3-dimethoxy-5-methyl-1,4-benzoquinone were identified from the secretions, together with trace amounts of 1,4-benzoquinone. 相似文献
33.
Jorge D.A. Bellido Eurico Y. Tanabe Elisabete M. Assaf 《Applied catalysis. B, Environmental》2009,90(3-4):485-488
Supported nickel catalysts of composition Ni/Y2O3–ZrO2 were synthesized in one step by the polymerization method and compared with a nickel catalyst prepared by wet impregnation. Stronger interactions were observed in the formed catalysts between NiO species and the oxygen vacancies of the Y2O3–ZrO2 in the catalysts made by polymerization, and these were attributed to less agglomeration of the NiO during the synthesis of the catalysts in one step. The dry reforming of ethanol was catalyzed with a maximum CO2 conversion of 61% on the 5NiYZ catalyst at 800 °C, representing a better response than for the catalyst of the same composition prepared by wet impregnation. 相似文献
34.
Akihiro Orita Shoko Tanabe Tatsuhiko Ono Junzo Otera 《Advanced Synthesis \u0026amp; Catalysis》2010,352(9):1419-1423
Fluorous distannoxanes (XRf2SnOSnRf2X)2⋅n H2O (Rf=C6F13C2H4) ( 1 : X=C8F17SO3, n=10; 4 : X=Cl, n=0) ( 1 ) catalyze the Mukaiyama aldol reaction and the allylation of aldehydes with tetraallyltin at room temperature in fluorous/organic biphasic solvent systems, in which the reactions proceed more rapidly than in a single organic or fluorous solvent. Due to the unique surface activity of 1 , the catalyst, organic substrate(s), and reagent(s) are distributed in both organic and fluorous phases to facilitate smooth reactions. Upon dilution with toluene after the reaction, the catalyst concentrates to the fluorous phase, while the organic substances migrate to the organic phase to effect facile catalyst recovery and recycling. By virtue of such a unique solvophilicity, a new version of fluorous biphase technology has been developed. 相似文献
35.
Biodegradable elastomeric network poly(ester-carbonate)s were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Yt) or trimesic acid (Y) and polycarbonate diols (PCD) with molecular weights of 1000 and 2000 g/mol. Prepolymers prepared by a melt polycondensation were cast from dimethylformamide solution and postpolymerized at 270 °C for 40-80 min to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. WAXS exhibited the crystalline peaks due to polycarbonate segments for the network films from PCD2000, while those from PCD1000 were amorphous. The tensile properties were determined for these network films at the temperatures 22, 30, 40 and 50 °C. These films showed elastomeric properties at all temperatures measured. The elongation at break was much higher for the films from PCD2000 (208-434%) than those from PCD1000 (40-120%), and decreased with increasing temperatures. The weight losses of the network films degraded in the buffer solution of Rhizopus delemar lipase at 37 °C increased with time, suggesting that these network films are biodegradable. The degradation rate of the network films from Yt is faster than that from Y. The GPC curves showed that the lipase hydrolyzed both the ester linkages between Y or Yt and PCD as well as polycarbonate moiety in the network polymer. 相似文献
36.
Open dumping site in Asian developing countries: a potential source of polychlorinated dibenz-p-dioxins and polychlorinated dibenzofurans 总被引:1,自引:0,他引:1
Nguyen HM Tu BM Watanabe M Kunisue T Monirith I Tanabe S Sakai S Subramanian A Sasikumar K Pham HV Bui CT Tana TS Prudente MS 《Environmental science & technology》2003,37(8):1493-1502
Open landfill dumping areas for municipal wastes in Asian developing countries have recently received particular attention with regard to environmental pollution problems. Because of the uncontrolled burning of solid wastes, elevated contamination by various toxic chemicals including dioxins and related compounds in these dumping sites has been anticipated. In this study, concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) were determined in soils from dumping sites in the Philippines, Cambodia, India, and Vietnam. Residue concentrations of PCDD/Fs and coplanar PCBs in dumping site soils were apparently greater than those in soils collected in agricultural or urban areas far from dumping sites, suggesting that dumping sites are potential sources of PCDD/Fs and related compounds. Observed PCDD/F concentrations in soils from dumping sites in the Philippines and Cambodia were comparable or higher than those reported for dioxin-contaminated locations in the world (e.g., near the municipal waste incinerators and open landfill dumping sites). Homologue profiles of PCDD/Fs in dumping site soils from the Philippines and, to a lesser extent, from Cambodia and India reflected patterns of samples representing typical emissions, while profiles of agricultural or urban soils were similar to those of typical environmental sinks. This result suggests recent formation of PCDD/Fs in dumping site areas and that open dumping sites are a potential source of dioxins in Asian developing countries. Uncontrolled combustions of solid wastes by waste pickers, generation of methane gas, and low-temperature burning can be major factors for the formation of dioxins in dumping sites. Elevated fluxes of PCDD/Fs to soils in dumping sites were encountered in the Philippines, Cambodia, India, and Vietnam-Hanoi, and these levels were higher than those reported for other countries. Considerable loading rates of PCDD/Fs in the dumping sites of these countries were observed, ranging from 20 to 3900 mg/yr (0.12-35 mg TEQ/yr). PCDD/F concentrations in some soil samples from the Philippines, Cambodia, India, and Vietnam-Hanoi exceeded environmental guideline values, suggesting potential health effects on humans and wildlife living near these dumping sites. The estimated intakes of dioxins via soil ingestion and dermal exposure for children were higher than those for adults, suggesting greater risk of dioxin exposure for children in dumping sites. To our knowledge, this is the first comprehensive study on PCDD/Fs contamination in open dumping sites of Asian developing countries. On the basis of the result of this study, we have addressed a new environmental issue that open dumping sites are potential sources of PCDD/Fs and related compounds, and dioxin contamination in dumping sites may become a key environmental problem in developing countries. 相似文献
37.
S. Wang F. Yamamoto T. Akatsu Y. Tanabe E. Yasuda 《Journal of Materials Science》1999,34(14):3489-3494
YAG-alumina composites with Al2O3-rich and YAG-rich compositions were prepared by annealing the hot-pressed composites at the eutectic temperature (1820°C) for 1 h followed by cooling down at 10 or 100°C/min in argon atmosphere. Microstructural observations of the solidified composites identified that metastable phase -Al2O3 precipitated in the Al2O3-rich specimens cooled down at both the cooling rates. For the solidified YAG-rich specimens, however, equilibrium phase -Al2O3 could not be reprecipitated, moreover, metastable YAlO3 phase was formed at cooling rate of 100°C/min. Formation of the metastable phases in the solidified composites was attributed to the decreased melting temperature caused by the divorced eutectic precipitation and the metastable decomposition of YAG component in YAG-alumina eutectic melt during rapid solidification. 相似文献
38.
39.
Even at ambient pressure and temperature TiFe and TiFe-Nb 6.8 at.% compounds display their outstanding abilities for absorbing hydrogen when cathodically polarized in an aqueous solution. Electrochemical reaction is also highly activated on electrodes made of these intermetallic compounds. This paper describes the results of electrochemical measurement and the surface properties of both TiFe and TiFe-Nb 6.8 at.% electrodes in comparison with those obtained using TiNin and TiCon (n = 1, 2, 3), emphasizing catalytic activity for the reaction of hydrogen evolution. It was concluded that the electrochemically active site of TiFe or TiFe-Nb 6.8 at.% electrode surface could be formed only after a specified area of the electrode had been covered with hydrogen of one or a few atomic layers. At the same time, this site acts as an entrance and exit for hydrogen into and out of the electrode. 相似文献
40.
H. Tsukada Z. Asaki T. Tanabe Y. Kondo 《Metallurgical and Materials Transactions B》1981,12(3):603-609
. A rectangular plate of mixed copper-iron sulfide composed of bornite (Cu5FeS4) and troilite (FeS) was oxidized in an O2-Ar mixed gas stream at 1023 to 1123 K. At the start of the oxidation, iron was preferentially oxidized with the rapid formation
of a dense Fe3O4 layer of about 10 μm thickness on the sample surface, without the evolution of SO2 gas. Following this reaction, layers of both Fe3O4 and Fe2O3 grew on the sulfide surface in accordance with the parabolic rate law. The diffusion of iron through the oxide layers was
assumed to control the oxidation rate during this stage. The effect of oxygen partial pressure on the parabolic rate constants
was minor and an apparent activation energy of 126 kJ/mol was obtained. During the later stages of the reaction, when the
sulfur activity in the inner sulfide core increased, the oxidation proceeded irregularly to the interior of the remaining
sulfide with the formation of a porous oxide and the evolution of gaseous SO2. The remaining sulfide core was found to be
a mixture of bornite (Cu5FeS4) and djurleite (Cu1.96S).
H. TSUKADA, former Graduate Student at Kyoto University 相似文献