首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   413篇
  免费   20篇
  国内免费   1篇
电工技术   7篇
综合类   1篇
化学工业   148篇
金属工艺   2篇
机械仪表   5篇
建筑科学   15篇
矿业工程   1篇
能源动力   12篇
轻工业   48篇
水利工程   8篇
石油天然气   1篇
无线电   15篇
一般工业技术   79篇
冶金工业   53篇
原子能技术   1篇
自动化技术   38篇
  2024年   2篇
  2023年   6篇
  2022年   20篇
  2021年   22篇
  2020年   15篇
  2019年   9篇
  2018年   21篇
  2017年   11篇
  2016年   12篇
  2015年   9篇
  2014年   14篇
  2013年   18篇
  2012年   26篇
  2011年   24篇
  2010年   22篇
  2009年   24篇
  2008年   24篇
  2007年   19篇
  2006年   17篇
  2005年   14篇
  2004年   12篇
  2003年   6篇
  2002年   14篇
  2001年   4篇
  2000年   6篇
  1999年   6篇
  1998年   6篇
  1997年   2篇
  1996年   4篇
  1995年   2篇
  1994年   1篇
  1993年   3篇
  1992年   5篇
  1991年   4篇
  1990年   4篇
  1989年   3篇
  1988年   1篇
  1987年   3篇
  1986年   3篇
  1985年   5篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1963年   2篇
  1961年   1篇
  1960年   3篇
排序方式: 共有434条查询结果,搜索用时 15 毫秒
21.
Thermal processing is the most widely adopted technology for preservation of juices; however, it is associated with significant changes in nutritional quality and flavor. Combination of nonthermal hurdles (ozone 1.2 g/h, 10 min, and lactic acid 0.5%) reduced total bacterial count of sugarcane juice by 4.3 log and controlled enzymatic activity to a moderate level (reduction of 60% and 72% activity of polyphenol oxidase and peroxidase, respectively). Combined treatment was comparable to thermal treatment in maintaining microbial and sensory quality of sugarcane juice during 1-month storage under refrigerated conditions; however, additional hurdles may be required for extended storage.  相似文献   
22.
The red clover casebearer, Coleophora deauratella Leinig and Zeller (Lepidoptera: Coleophoridae), is a major pest of red clover (Trifolium pratense L.) grown for seed in Canada and parts of Europe. Insecticides are ineffective against C. deauratella, and other control methods, such as pheromone-mediated mating disruption, need to be explored. The efficacy and mechanisms of communication disruption were evaluated in small-plot trials (0.25 ha) with reservoir-type rope dispensers loaded with either the complete pheromone blend [10:1 ratio of (Z)-7-dodecenyl acetate: (Z)-5-dodecenyl acetate] or the major component alone [(Z)-7-dodecenyl acetate]. Both formulations reduced catches of male C. deauratella in pheromone traps (>99.6 %). In pheromone-treated plots, more males were caught on yellow sticky cards near dispensers that released the complete pheromone blend, than on cards near dispensers releasing the major component. In the laboratory, after pre-exposure to either the complete blend or the major component for 1 h, male C. deauratella antennae became adapted, as measured by electroantennograms conducted 5 min. after treatment. Adaptation due to pre-exposure to either formulation resulted in a shift in the pheromone response threshold; antennae from pre-exposed moths responded more strongly to high pheromone dosages (5–50 μg) than did antennae from untreated control moths. Antennae from moths held in clean air for 24 h after pre-exposure recovered and responded similarly to pheromone as antennae from control moths. These results suggest that both formulations have the potential to disrupt pheromone communication in C. Deauratella, but that the disruption mechanisms of the two formulations likely differ.  相似文献   
23.
Poly(styrene-divinylbenzene) monoliths have been hypercrosslinked using a Fe3+ catalyzed Friedel–Crafts reaction involving three external crosslinkers (1) 4,4′-bis(chloromethyl)-1,1′-biphenyl, (2) α,α′-dichloro-p-xylene, and (3) formaldehyde dimethyl acetal. The first crosslinker was found to produce monoliths with the best chromatographic performance. The effects of a number of variables affecting the hypercrosslinking reaction were studied in detail. These variables included: (i) the temperature and time used for polymerization of the precursor monoliths, (ii) the amount and loading procedure of the external crosslinker and catalyst, and, (iii) the temperature and reaction time of the Friedel–Crafts alkylation. Polymers with extremely large surface areas reaching up to 900 m2/g were obtained using a precursor monolith polymerized for only 2.5 h, and hypercrosslinked with 4,4’-bis(chloromethyl)-1,1′-biphenyl. The increased performance of monoliths modified using this new procedure is comparable to the performance obtained with monolithic polymers containing chloromethylstyrene. However, the preparation of the poly(styrene-divinylbenzene) precursor is simpler than that of conterparts containing chloromethylstyrene. The hypercrosslinked monoliths in capillary columns were tested in an isocratic reversed phase liquid chromatography separation using a mixture comprised of acetone and six alkylbenzenes. Column efficiencies for retained analytes exceeded 70,000 plates/m.  相似文献   
24.
Phosphoproteomics is a cutting-edge technique that can be utilized to explore adipose tissue (AT) metabolism by quantifying the repertoire of phospho-peptides (PP) in AT. Dairy cows were supplemented with conjugated linoleic acid (CLA, n = 5) or a control diet (CON, n = 5) from 63 d prepartum to 63 d postpartum; cows were slaughtered at 63 d postpartum and AT was collected. We performed a quantitative phosphoproteomics analysis of subcutaneous (SC) and omental (OM) AT using nanoUPLC-MS/MS and examined the effects of CLA supplementation on the change in the phosphoproteome. A total of 5919 PP were detected in AT, and the abundance of 854 (14.4%) were differential between CON and CLA AT (p ≤ 0.05 and fold change ± 1.5). The abundance of 470 PP (7.9%) differed between OM and SC AT, and the interaction treatment vs. AT depot was significant for 205 PP (3.5% of total PP). The integrated phosphoproteome demonstrated the up- and downregulation of PP from proteins related to lipolysis and lipogenesis, and phosphorylation events in multiple pathways, including the regulation of lipolysis in adipocytes, mTOR signaling, insulin signaling, AMPK signaling, and glycolysis. The differential regulation of phosphosite on a serine residue (S777) of fatty acid synthase (FASN) in AT of CLA-supplemented cows was related to lipogenesis and with more phosphorylation sites compared to acetyl-coenzyme A synthetase (ACSS2). Increased protein phosphorylation was seen in acetyl-CoA carboxylase 1 (ACACA;8 PP), FASN (9 PP), hormone sensitive lipase (LIPE;6 PP), perilipin (PLIN;3 PP), and diacylglycerol lipase alpha (DAGLA;1 PP) in CLA vs. CON AT. The relative gene expression in the SC and OM AT revealed an increase in LIPE and FASN in CLA compared to CON AT. In addition, the expression of DAGLA, which is a lipid metabolism enzyme related to the endocannabinoid system, was 1.6-fold higher in CLA vs. CON AT, and the expression of the cannabinoid receptor CNR1 was reduced in CLA vs. CON AT. Immunoblots of SC and OM AT showed an increased abundance of FASN and a lower abundance of CB1 in CLA vs. CON. This study presents a complete map of the SC and the OM AT phosphoproteome in dairy cows following CLA supplementation and discloses many unknown phosphorylation sites, suggestive of increased lipid turnover in AT, for further functional investigation.  相似文献   
25.
We have developed a novel sensor that enables us to measure the relative story displacement of a building structure in real time. This lateral displacement sensor (LDS) is composed of a light‐emitting diode (LED) array, which is fixed on the ceiling, and a position‐sensitive detector (PSD) unit, which is placed on the floor. We optimized the LDS to achieve high accuracy in lateral displacement measurement. The accuracy was evaluated to be 60 µm by conducting shaking table tests. Two LDSs were implemented in an actual building equipped with an active variable stiffness (AVS) system, and the building was vibrated with seismic waveforms by an exciter placed on the rooftop. The seismic displacement of the second floor relative to the first floor was measured using the LDS. Furthermore, the inclination angle of the second floor could be measured using the LDS during the seismic vibration. Using the AVS system, we realized the residual displacement of the second floor without inducing damage to the building, and succeeded in real‐time residual displacement measurement for the first time. These results indicate that the LDS is useful for the health diagnosis of a building structure. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
26.
The stock of aged power equipment is increasing and it is important to clarify the characteristics of deteriorated insulating oil. This paper describes a basic study of molecular behavior in the oxidation of insulating oil by terahertz spectroscopy. The oxidation of insulating oil was modeled by using various compositions of dodecane and 2‐octanol. The terahertz measurements indicated that signi?cant absorption related to hydroxyl groups (‐OH) occurred between 6 and 7 THz. The absorption band was also observed in accelerated aging alkylbenzene, which is used in power equipment as insulating oil and is sensitive to hydrogen bonds. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 9–15, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22335  相似文献   
27.
The topcoat thickness of thermal barrier coating (TBC) samples was measured using terahertz (THz) waves. The index of refraction of yttria‐stabilized zirconia (YSZ), which is the topcoat material, is necessary to obtain the topcoat thickness from time domain re?ectometry. Time domain THz spectroscopy was applied to YSZ samples, and the index of refraction was measured to be 4.8 in the frequency region 0.1 to 1.2 THz. The topcoat thickness of six di?erent TBC samples, which varied from 300 to 600 µm, was measured using THz waves. The results were in agreement with microscope observation results to within measurement error. In addition, the topcoat thickness pro?le of a turbine blade sample was measured with a resolution of 2.4 µm. The pro?le showed a standard deviation of 4 µm, which re?ects the actual variation in the topcoat thickness. The results showed that THz waves are e?ective for high‐resolution measurement of the topcoat thickness. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 1–9, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22385  相似文献   
28.
Hybrid architectures combining conventional processors with configurable logic resources enable efficient coordination of control with datapath computation. With integration of the two components on a single device, housekeeping tasks and, optionally, loop control and data-dependent branching, can be handled by the conventional processor, while regular datapath computation occurs on the configurable hardware. This paper describes a novel approach to programming such hybrid devices that gives the programmer control over mapping of data and computation between conventional processor and configurable logic. With a simple set of pragma and intrinsic function directives, the NAPA C language provides for manual control over perhaps the most important aspect of programming such hybrid devices. Alternatively, as experience is gained about tradeoffs between the two computational resources, mapping directives may eventually be generated by an external tool. The paper further describes a research prototype compiler that targets the hybrid processor model, with a concrete implementation for the National Semiconductor NAPA1000 chip. The NAPA C compiler parses the mapping directives, performs semantic analysis, and co-synthesizes a conventional processor executable combined with a configuration bit stream for the configurable logic. Two major compiler phases, the synthesis of pipelined loops and the datapath synthesis, are described in detail.  相似文献   
29.
An amphiphilic copolymer composed of maleic acid and alkyl (C18) vinyl monomer was encapsulated into the porous support. A series of colloidal gold nanoparticles of known size was substantially immobilized in the composite porous supports based on cross-linked polyacrylate ester and cross-linked polystyrene resin. Maleic acid moiety of the amphiphilic copolymer can act as a stabilizer for gold nanoparticles in analogy to citric acid, whereas alkyl chains play a role for the stable accommodation of the amphiphilic copolymer. Maleic acid stabilizes the gold nanoparticles by flexing the geometrical arrangement of the linear polymer. Presence of C18 alkyl chain in the poly(C18-vinyl maleate) is indispensable to act as spacing group that prevents mutual aggregation of gold nanoparticles. On the other hand, gold nanoparticles with average diameter of less than 8 nm were spontaneously formed by treatment of the composite resin beads with aqueous HAuCl4 solution, subsequently dispersed inside the pores of resin beads as observed by TEM. We have also elucidated the catalytic activity of the material with the hydrogenation of cinnamaldehyde in supercritical carbon dioxide. Notably, apparent size effect of gold was observed in the selectivity of the reaction.  相似文献   
30.
The degree of homogeneity and H-bond interaction in blends of low-molecular-mass poly(ethylene glycols) (PEG, Mw = 400, 600, 1000) and poly(vinylpyrrolidone) (PVP, Mw = 9 × 103) prepared in supercritical CO2, ethanol and as physical mixtures were studied by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMA) techniques. Homogeneity of samples prepared in supercritical CO2 were greater than physically mixed samples, but slightly less than ethanol-cast samples. PEG-PVP H-bond interaction was higher for ethanol-cast blends when compared to blends prepared in supercritical CO2. This reduced interaction was attributed to a combination of: (1) shielding of PEG-PVP H-bond interactions when CO2 is dissolved in the blend; (2) rapidly reduced PEG and PVP chain mobility upon CO2 venting, delaying rearrangement for optimum PEG-PVP H-bond interaction.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号