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排序方式: 共有340条查询结果,搜索用时 31 毫秒
71.
Masabumi Masuko Akihito Suzuki Yu Sagae Maiko Tokoro Kenji Yamamoto 《Tribology International》2006,39(12):1601
Water has been considered as an alternative working fluid for hydraulic power systems in order to minimize the consumption of fossil fuels and mineral oils. In spite of the many advantages to this use of water, difficult technical problems remain. The key technology for establishing a water hydraulic system is tribology, because water has a lack of lubricity, and thus some coating is needed to protect the metal surfaces from corrosion and frictional wear when using water as a lubricant. It has already been demonstrated that some Si-containing materials have good lubricity in a water environment. Recently, it has been shown that diamond-like carbon (DLC) coatings also have good lubricity with water. In order to clarify the mechanism by which such materials are lubricated with water, and to develop surface coatings that have good lubricity with water, the friction characteristic of several coated metals were investigated in this study. Coatings of CrN, CrSiN, and two types of DLC were applied on an SUS630 stainless steel flat disk substrate. Additive-free distilled water was used as a lubricating fluid. The friction characteristics of these coatings at different sliding speeds were evaluated using a tribometer with two contact configurations in which stainless steel balls and a flat ring without coatings were used as mating specimens.In addition, the lubrication characteristics of organic hydro-gels such as alginic acid or its metal salt were studied by immobilizing them on the surface, and their effects on the lubrication with water were discussed. 相似文献
72.
73.
Yu Nagata Masaya Minagawa Shosei Hisatomi Yuki Tsunazawa Kyoko Okuyama Motonori Iwamoto Yasuyoshi Sekine Chiharu Tokoro 《Advanced Powder Technology》2019,30(5):1034-1042
A bead mill is commonly used to produce nanomaterials. The design of the bead mill rotor is an important factor in efficient nanomaterial production to avoid re-agglomeration. We investigated the effect of bead-mill rotor shape on the dispersion state using experimental tests and the discrete-element method (DEM) coupled with computational fluid dynamics (CFD) simulations. Experimental results using TiO2 in the bead mill showed that the high rotor rotation speed caused TiO2 particles re-agglomeration, and a sharp particle-size distribution was obtained by dispersion with a mill with a wide gap between the rotor and the chamber. To evaluate the dispersion performance, bead collisions were analyzed using the DEM-CFD simulation. The simulation results indicated that an increase in bead-collision energy lead to damage of the TiO2 primary particles and re-agglomeration at a high rotation speed. A uniform dispersion was achieved when the frequency of high-energy collision between the particle and wall decreased and a small standard deviation of the collision energy frequency was obtained by the mill with a wide gap. These simulation results correlate with the experimental results. Therefore, this study shows that the DEM-CFD simulation could contribute to an appropriate rotor design for uniform dispersion. 相似文献
74.
Kenji Kikuchi Hiroko Takeda Beatrice Rabolt Takuji Okaya Zempachi Ogumi Yasuhiro Saihara Hiroyuki Noguchi 《Journal of Applied Electrochemistry》2001,31(12):1301-1306
The supersaturated concentration of hydrogen in electrolyzed water obtained from a flow-type electrolytic cell was studied under various electrolysis conditions. The degree of supersaturation was found to decrease as the solution supply rate to the cell increased. The ratio of observed hydrogen concentration to the theoretical hydrogen concentration obtained from the electrochemical equivalent, as calculated from the transfer of charge in the cell, was found to increase with the solution supply rate. The concentration of hydrogen in solution has a maximum at a current density of approximately 0.3 A dm–2. This maximum was found to be independent of the flow rate, indicating that the hydrogen concentration is related to both the diffusion of dissolved hydrogen from the electrode surface to the bulk solution and hydrogen bubble growth. 相似文献
75.
Kamiya Noriho; Okimoto Yuko; Ding Zhen; Ohtomo Hiroko; Shimizu Masafumi; Kitayama Atsushi; Morii Hisayuki; Nagamune Teruyuki 《Protein engineering, design & selection : PEDS》2001,14(6):415-419
We have recently generated a new mutant of cytochrome b562 (cytb562)in which Met7, one of the axial heme ligands, is replaced byAla (M7A cytb562). The M7A cytb562 can bind heme and the UV-visibleabsorption spectrum is of a typical high-spin ferric heme. Toinvestigate the effect of the lack of Met7 ligation on the structuralintegrity of cytb562, thermal transition analyses of M7A cytb562were conducted. From the thermodynamic parameters obtained,it is concluded that the folding of M7A cytb562 is comparableto the apoprotein despite the presence of heme. On the otherhand, exogenous ligands such as cyanide and azide ions are readilybound to the heme iron, indicating that the axial coordinationsite is available for substrate binding. The peroxidase activityof this mutant is thus examined to evaluate new enzymatic functionat this site and M7A cytb562 was found to catalyze an oxidationreaction of aromatic substrates with hydrogen peroxide. Theseobservations demonstrate that the Met7/His102 bis-ligation tothe heme iron is crucial for the stable folding of cytb562,whereas the functional conversion of cytb562 is successfullyachieved by the loose folding together with the open coordinationsite. 相似文献
76.
Hiroko Abe Yasuko Fujita Yuki Takaoka Eri Kurita Shuntaro Yano Naotaka Tanaka Ken-ichi Nakayama 《Journal of Bioscience and Bioengineering》2009,108(3):199-204
Ethanol damages the cell membrane and functional proteins, gradually reducing cell viability, and leading to cell death during fermentation which impairs effective bioethanol production by budding yeast Saccharomyces cerevisiae. To obtain more suitable strains for bioethanol production and to gain a better understanding of ethanol tolerance, ethanol-tolerant mutants were isolated using the novel mutagenesis technique based on the disparity theory of evolution. According to this theory evolution can be accelerated by affecting the lagging-strand synthesis in which DNA polymerase δ is involved. Expression of the pol3-01 gene, a proofreading-deficient of DNA polymerase δ, in S. cerevisiae W303-1A grown under conditions of increasing ethanol concentration resulted in three ethanol-tolerant mutants (YFY1, YFY2 and YFY3), which could grow in medium containing 13% ethanol. Ethanol productivity also increased in YFY strains compared to the wild-type strain in medium containing 25% glucose. Cell morphology of YFY strain cells was normal even in the presence of 8% ethanol, whereas W303-1A cells were expanded by a big vacuole. Furthermore, two of these mutants were also resistant to high-temperature, Calcofluor white and NaCl. Expression levels of TPS1 and TSL1, which are responsible for trehalose biosynthesis, were higher in YFY strains relative to W303-1A, resulting in high levels of intracellular trehalose in YFY strains. This contributed to the multiple-stress tolerance that makes YFY strains suitable for the production of bioethanol. 相似文献
77.
Takashi Watanabe Hiroko Ikeda Kazuo Masaki Tsutomu Fujii Haruyuki Iefuji 《Journal of Bioscience and Bioengineering》2009,108(3):225-230
Phosphohydrolysis of organic phosphorus compounds by acid phosphatases (EC 3.1.3.1 and EC 3.1.3.2) is an important method for efficient removal of phosphorus from high concentration organic wastewater. Another important method is supplementation of animal feed with phytase (EC 3.1.3.8 and EC 3.1.3.26), which improves the availability of phytate-phosphates (phosphate that are hydrolyzed by phytases), making it possible to add less phosphate to animal feed and resulting in the excretion of less phosphorus by the animals. In the present study, we purified a novel phytase from the wastewater treatment yeast Hansenula fabianii J640 (Hfphytase), cloned the 1456 bp open reading frame (ORF) encoding Hfphytase, and characterized Hfphytase. The molecular weight of Hfphytase after deglycosylation by PNGaseF was 49 kDa. The optimal pH and temperature for enzyme activity were 4.5 and 50 °C, respectively. Hfphytase exhibits 40% identity with Debaryomyces castellii phytase, 37% identity with Aspergillus niger PhyB, and 34% identity with Saccharomyces cerevisiae Pho5p. Recombinant Hfphytase was transformed and expressed in Pichia pastoris. The yield was 23 g/l by jar fermenter cultivation. The marked phosphohydrolysis activity exhibited by Hfphytase on six substrates (pNP-P, sodium phytate, glucose-1 phosphate, glucose-6 phosphate, α-glycerophosphate and β-glycerophosphate) indicated that it is a non-specific acid phosphatase. 相似文献
78.
79.
Cognition, Technology & Work - Vessel traffic service (VTS) is important to protect the safety of maritime traffic. Along with the expansion of monitoring area per VTS operator in Tokyo Bay,... 相似文献
80.
Hiroko Ohuchi Akira Yamadera Takashi Nakamura 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2000,450(2-3):343-352
Several experiments were performed to investigate the effects of temperature on the fading of the commercial imaging plate, IP (BAS-UR). The fading characteristics were measured under controlled temperatures between 0°C and 60°C after irradiation with 238U alpha-ray and 60Co gamma-ray sources. Applying Arrhenius' equation to the experimental results, we calculated a universal functional equation that includes two variables: elapsed time (t) and temperature (K). The photo-stimulated luminescence (PSL) calculated by this equation showed good agreement with the results of our experimental ones between 0°C and 40°C. From this equation, the activation energies of the fading are estimated to be about 0.9 eV for both 238U alpha-ray and 60Co gamma-ray sources. 相似文献