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71.
Delayed fracture properties of AISI 4135 high strength steels with 1490 and 1310 MPa of tensile strength, represented as B15 and B13, respectively, have been studied by means of slow strain rate test (SSRT) of notched bar specimens after outdoor exposure at rural and coastal areas. The exposed specimens were kept at humid medium before SSRT to reproduce active hydrogen entry influenced by the rust layer and to homogenize hydrogen distribution. The influences of exposure site and exposure time on fracture stress have been investigated. The susceptibility of B15 to delayed fracture was obviously higher than that of B13. 相似文献
72.
Takashi Matsumura Fumio Iida Takuya Hirose Masahiko Yoshino 《Journal of Materials Processing Technology》2012,212(12):2669-2677
A micro fabrication is presented to manufacture hydrophobic surfaces with micro-scale structures. Hydrophobicity is controlled with the shape and the alignment of micro pillars in the structure. The structures are manufactured in large areas at high production rates in the following processes: (1) the structure is fabricated on a tool by focused ion beam sputtering; (2) the reverse structure is formed on a metal plate by incremental stamping using the structured tool; and (3) the structure is transferred onto plastic plates by molding. A consecutive stamping is also proposed to fabricate several structures on a surface accurately with a structured tool, in which the moving pitch of the structured tool is numerically controlled. The effect of the surface topography on hydrophobicity is discussed with measuring contact angles on the structured surfaces in the water droplet tests. Hydrophobicity on the plastic plate is associated with the solid fraction on the structured surface based on the Cassie–Baxter model. A larger contact angle is observed for a smaller solid fraction of the surface. 相似文献
73.
The demulsification of oil-in-water (O/W) emulsions under freezing conditions is connected to fat crystallization in the oil
droplet. Therefore, demulsification can be prevented by the use of oil with a low melting point, and also by lowering the
O/W ratio. However, an oil with a low melting point, such as sunflower, is rather expensive, and the O/W ratio has a significant
effect on the texture of emulsions. We searched for an oil that is suitable for the production of a freeze-stable emulsion
and found that soybean oil has unique characteristics. Normally, emulsions are more unstable at lower temperatures; soybean
oil emulsion is unstable at −10°C and stable at −20°C. This unique characteristic results from the following two reasons.
First, the solid fat content of soybean oil is almost the same at −10 and −20°C. Second, small crystals form a larger network
over a period of time, and the higher temperature promotes faster restructuring. This structure formation was microscopically
observed with the use of a thermostated stage. Structure formation was suppressed with the addition of a crystal structure
modifier, polyglycerol fatty acid full ester, which also suppressed coalescence. 相似文献
74.
Jinfeng Wang Takuya Tsuzuki Lu Sun Xungai Wang 《Journal of the American Ceramic Society》2009,92(9):2083-2088
The use of zinc oxide (ZnO) nanoparticles as ultraviolet (UV) absorbers for many organic substrates is limited because of the high photocatalytic activity of ZnO. In this study, a facile and efficient technique for the preparation of a hybrid material of silica-coated ZnO nanoparticles was used to reduce the photocatalytic activity of ZnO. Monodispersed ZnO nanopartcles were prepared by wet chemistry and the particle surface was modified by tetraethylorthosilicate to form a silica coating via the Stöber method. ZnO samples, both before and after the coating process, were investigated by transmission electron microscopy, X-ray diffraction, dynamic light scanning, infrared, and UV-Vis absorption spectroscopy. The effect of the surface modification on the photocatalytic activity of ZnO was studied by monitoring the degradation of Rhodamine B caused by photo-generated free radicals. The results implied that the photo-generation of free-radicals was strongly quenched by the presence of silica on the particle surface. 相似文献
75.
The Heck reaction of iodobenzene and methyl acrylate was investigated with CO2-philic Pd complex catalysts having fluorous ponytails and the organic base triethylamine (Et3N) in the presence of CO2 under solventless conditions at 80 °C. The catalysts are not soluble in the organic phase in the absence of CO2 and the reaction occurs in a solid-liquid biphasic system. When the organic liquid mixture is pressurized by CO2, CO2 is dissolved into the organic phase and this promotes the dissolution of the Pd complex catalysts. As a result, the Heck reaction occurs homogeneously in the organic phase, which enhances the rate of reaction. This positive effect of CO2 pressurization competes with the negative effect that the reacting species are diluted by an increasing amount of CO2 molecules dissolved. Thus, the maximum conversion appears at a CO2 pressure of around 4 MPa under the present reaction conditions. The catalysts are separated in the solid granules by depressurization and are recyclable without loss of activity after washing with n-hexane and/or water. When the washing is made with hexane alone, the catalytic activity tends to increase on the repeated Heck reactions, probably due to the accumulation of such a base adduct as Et3NHI on the catalysts. When the washing is further made with water, however, the base adduct is taken off from the catalysts and they show similar activity levels in the repeated runs. The potential of CO2 pressure tunable heterogeneous/homogeneous reaction system has also been investigated for Sonogashira reactions of iodobenzene and phenylacetylene under similar conditions. 相似文献
76.
K. Hashimoto M. YamasakiS. Meguro T. SasakiH. Katagiri K. IzumiyaN. Kumagai H. HabazakiE. Akiyama K. Asami 《Corrosion Science》2002,44(2):371-386
CO2 emissions, which induce global warming, increase with the development of economic activity. It is impossible to decrease the CO2 emissions by suppression of the economic activity. Global CO2 recycling can solve this problem. The global CO2 recycling consists of three district: The electricity is generated by solar cells on deserts. At desert coasts, the electricity is used for H2 production by seawater electrolysis and H2 is used for CH4 production by the reaction with CO2. CH4 which is the main component of liquefied natural gas is liquefied and transported to energy consuming districts where CO2 is recovered, liquefied and transported to the desert coasts. A CO2 recycling plant for substantiation of our idea has been built on the roof of the Institute for Materials Research in 1996. Key materials necessary for the global CO2 recycling are the anode and cathode for seawater electrolysis and the catalyst for CO2 conversion. All of them have been tailored by us. They have very high activity and selectivity for necessary reactions in addition to excellent durability. A pilot plant consisting of minimum units in an industrial scale is going to be built in three years. 相似文献
77.
Segawa T Kateb F Duma L Bodenhausen G Pelupessy P 《Chembiochem : a European journal of chemical biology》2008,9(4):537-542
Although labile protons that are exchanging rapidly with those of the solvent cannot be observed directly, their exchange rate constants can be determined by indirect detection of scalar-coupled neighboring nuclei. We have used heteronuclear NMR spectroscopy to measure the exchange rate constants of labile protons in the side chains of lysine and arginine residues in ubiquitin enriched in carbon-13 and nitrogen-15 at neutral pH. Exchange rate constants as fast as 40x10(3) s(-1) were thus measured. These results demonstrate that NMR spectroscopy is a powerful tool for the characterization of lysine NH3(+) and arginine NH groups in proteins at physiologically relevant pH values. 相似文献
78.
Ping Sun Chao-Nan Xu Morito Akiyama Tadahiko Watanabe 《Journal of the American Ceramic Society》1999,82(6):1447-1450
Transparent PLZT(7/60/40) ceramics with large piezoelectric coefficients were obtained using a two-step sintering process with controlled oxygen partial pressure. Specifically, low-oxygen-pressure and low-temperature sintering were used in the first step, followed by a high-oxygen-pressure, high-temperature sintering cycle. High-density ceramics with small grain sizes of about 3 µm were prepared. As a result, k p = 0.71, k 33 = 0.78, d 33 = 850 × 10-12 C/N, and a transparency of 15% (λ= 610 nm, thickness of 1 mm) have been achieved; 20% improvement of d 33 was gained compared to conventional processed PLZT ceramics ( d 33 = 710 × 10-12 C/N). 相似文献
79.
I Made Joni Takuya Nishiwaki Kikuo Okuyama Shuuji Isoi Ryotaro Kuribayashi 《Powder Technology》2010,204(1):145-153
The use of aluminum trihydroxide (ATH) fillers as non-halogen flame retardants for polymethylmethacrylates (PMMA) creates a conflict between the mechanical properties and heat resistance of the composites. Therefore, to ensure that the PMMA mechanical properties remain satisfactory, improvements in both the filler–polymer interactions and the ability to control the size and size distribution, morphology and dispersion of the fillers are required. Thus, in the present study, bead milling was used to control both the size distribution and dispersion of ATH fillers in MMA, which had an initial average size of 0.75 μm. The dispersion was obtained by alteration of the surface characteristics of ATH fillers using a silane-based dispersing agent, (3-acryloxypropyl) trimethoxysilane (APTMS). Bead milling successfully comminuted the ATH particles and prevented the formation of ATH agglomerates. The smallest average size of the ATH particles after bead milling was 300 nm. Highly dispersed ATH filler particles were observed in the TEM images of the PMMA/ATH composites. The filler–polymer interaction, i.e. the interaction parameter (B), was calculated. The effects of volume fraction, particle size distribution, and surface modification of the fillers on the results of dynamic mechanical analysis (DMA) are discussed. The thermal stability of the PMMA/ATH composites was also investigated using thermal gravimetric analysis (TGA). 相似文献
80.
Takuya Noguchi Toshihiro Shimada Takashi Chiba Masao Terada Tetsuya Hasegawa 《Diamond and Related Materials》2010,19(2-3):107-109
We have carried out very high temperature heat treatment at 1400–2700 °C of about 10 nm-thick amorphous carbon thin films deposited on refractory substrates MgO, Al2O3, and yttria-stabilized zirconia (YSZ) using pulsed laser deposition techniques. After the annealing, a few nanometer scale sp2 crystallization of the films and a large corrugation with a height of more than 1 μm were observed by Raman spectroscopy analysis and optical/atomic force microscopes, respectively. The corrugation is probably caused by the formation of gases at the film/substrate interface during the heat treatment. 相似文献