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61.
Optical absorption characteristics in a glass-metal nanocomposite system involving bismuth metal have been analysed using effective medium theories with a model incorporating single strand chains andfcc clusters of metallic bismuth particles. The computed values show fair agreement with experimental data.  相似文献   
62.
Research and development on glass fibres was started at the Indian Institute of Technology (IIT), Kanpur, about three years ago. The two main directions in which efforts have been concentrated are (i) development of indigenous technology for producing glass fibres, (ii) development of new glass compositions for drawing fibres having novel physical properties. In this note, we briefly describe the activities of this group and some of the salient results obtained so far.  相似文献   
63.
Different reaction paths of mullite formation via sol-gel processing techniques are reviewed. These variations are due to differences in hydrolysis/gelation behaviours of the silica and alumina components used. Variations of pH during processing without altering other variables follow three different routes of mullite formation. In the highly acidic region(pH 1), the gel does not exhibit a 980 °C exotherm but forms -Al2O3. Mullite forms at high temperature by diminution of -Al2O3 and -cristobalite, respectively. In the pH range of 3–4.5, gels exhibit a 980 °C exotherm and develop only mullite. In the highly alkaline region (pH 14), the gel produces a Si-Al spinel phase at the 980 °C exotherm and mullite formation at the 1330 °C exotherm takes place from the intermediate Si-Al spinel phase.  相似文献   
64.
Sleep disorders are common in hemodialysis patients, although causes and consequences remain unclear. We sought to establish prevalence, determinants, and outcomes of sleep disturbances in patients receiving incremental dialysis. One hundred two unselected patients undergoing incremental high‐flux hemodialysis or hemodiafiltration underwent limited overnight sleep study. Large subsets underwent echocardiography, interdialytic ambulatory blood pressure monitoring, and brain natriuretic peptide measurements. Patients were followed up to 44 months. Full sleep data were obtained in 91 patients. All had sleep disturbance as evidenced by an apnea–hypopnea index >5/min. We defined major obstructive sleep apnea (MOSA) as an apnea–hypopnea index ≥15, together with either significant oxygen desaturation or symptoms of daytime sleepiness. Forty patients met these criteria. Significant independent predictors of MOSA were age <65 years, male gender, has diabetes, and has a brain natriuretic peptide >2500 pg/mL. Mean ambulatory blood pressure and left ventricular mass index were significantly higher in these patients. In a model controlling for body mass index, high C‐reactive protein, and the presence of cancer, MOSA was associated with a twofold increased risk of mortality, although this did not reach statistical significance. MOSA was common, and was associated with hypertension and high left ventricular mass index. Whether obstructive sleep apnea contributes to the high mortality remains to be firmly established.  相似文献   
65.
Theory of Constraints philosophy operates under the assumption that the goal of a for-profit business is to ‘Make money now and in the future’. Consequently, it is a manager's job continuously to search for ways to increase their operation's throughput. Increasing the amount of free goods the operation accepts is one way a manager can do this. Free goods are items that do not use the capacity of the operation's primary constraint. Because of this, it is possible to increase their output. However, increasing the number of free goods processed decreases the amount of protective capacity within the operation. Protective capacity plays a key role in the ability of an operation to deliver orders on time. Increasing the amount of free goods the operation processes is an action that could jeopardize the system's future throughput because it will impact on the operation's ability to ship orders on time. In order for managers to fulfil the goal of making money now and in the future, they must maximize total throughput while minimizing late orders. This paper provides some initial insights about how managers can intelligently manage free goods to balance these competing goals.  相似文献   
66.
In the present work cassava starch/agar Ag and ZnO nanocomposite films were prepared by the solution casting method. The structural, physical and antimicrobial properties of the nanocomposite films were studied as a function of the concentration of Ag and ZnO nanoparticles. The results of the thermogravimetric analysis showed 8–15% degradation of both the nanocomposite films at 150°C endorsing the thermal stability of the films. Scanning electron microscopic analysis reveals the uniform blending of Ag and ZnO nanoparticles with a starch/agar matrix with tiny waves like appearance on the surface. The incorporation of Ag and ZnO nanoparticles in the film was found to reduce the moisture content, water solubility and water vapour permeability with increase in the concentration of Ag and ZnO nanoparticles. The growth kinetics study of Pseudomonas aeruginosa and Staphylococcus aureus in the presence of Ag and ZnO blended nanocomposite films showed promising results especially against Gram‐negative P. aeruginosa. Thus, the film synthesised in the present study bears the potential to be used as active packaging material to prevent food from bacterial contamination and spoilage.Inspec keywords: casting, microorganisms, scanning electron microscopy, nanoparticles, food preservation, solubility, thermal analysis, zinc compounds, food processing industry, food products, thermal stability, permeability, antibacterial activity, food packaging, contaminationOther keywords: water vapour permeability, food packaging, solution casting method, structural properties, physical properties, antimicrobial properties, water solubility, agar nanocomposite film, starch nanocomposite film, Pseudomonas aeruginosa, Staphylococcus aureus, bacterial contamination prevention, spoilage prevention, scanning electron microscopic analysis, thermogravimetric analysis, temperature 150.0 degC, Ag, ZnO  相似文献   
67.
Composites comprising of nanoparticles of Ni0?5Zn0?5Fe2O4 (NZF) and BaTiO3 (BT), respectively were synthesized by a chemical method. The particles had diameters in the range of 15–31 nm. NZF was prepared by a coprecipitation technique. This was soaked in a sol containing BT. Compositions synthesized were xNZF-(1 – x) BT, where x = 0?7, 0?5 and 0?3, respectively. The composites showed ferromagnetic hysteresis loops due to NZF phase. The analysis of coercivity variation as a function of temperature gave blocking temperatures in the range of 306–384 K depending on the diameter of the ferrite nanoparticles. This implied that superparamagnetic interactions are above these temperatures. The nanocomposites also exhibited ferroelectric behaviour arising due to the presence of BT. The remanent polarization of the samples was small. This was adduced to the nanosize of BT. The specimens showed magneto-dielectric (MD) effect in the magnetic field range 0–0?7 Tesla. The MD parameter measured at the maximum magnetic field was around 2%. This was one order of magnitude higher than that reported so far in similar composite systems. This was explained on the basis of a two-phase inhomogeneous medium model with an interface between them, the phases possessing drastically different electrical conductivities.  相似文献   
68.
Nanocomposites   总被引:7,自引:0,他引:7  
Nanocrystalline metals having sizes of the order of a few nanometres dispersed in an oxide glass matrix have been discussed in this review. The various physical and chemical routes developed so far for synthesizing such materials have been described. The different physical properties, especially optical, electrical and magnetic behaviour of these nanocomposites have been delineated. The physical mechanisms which give rise to these characteristics are discussed.  相似文献   
69.
Review Synthesis of conducting nanowires   总被引:2,自引:0,他引:2  
Work reported on the synthesis of nanowires of different metals/alloys and semiconductors respectively in recent years is reviewed. The methods used mostly belong to one of the following categories: chemical, electrodeposition, physical and filling of carbon nanotubes. Electrical properties investigated for some of these nanowires indicate quantum mechanical effects to be present. Nanodevice fabrication using doped semiconducting nanowires has also been reported.  相似文献   
70.
Ultrasonic machining (USM) process has several important performance measures (responses), some of which are correlated. For example, material removal rate and tool wear rate are highly correlated. Although in the recent past several methods have been proposed in the literature to resolve the multi-response optimization problems, only a few of them take care of the possible correlation between the responses. All these methods primarily make use of principal component analysis (PCA) to consider the possible correlation between the responses. Process engineers may face the difficulty of selecting the appropriate method because the relative optimization performances of these methods are unknown. In this paper, two sets of past experimental data on USM process are analysed using three methods dealing with the multiple correlated responses, and the optimization performances of these three methods are subsequently compared. It is observed that both the weighted principal component (WPC) and PCA-based TOPSIS methods result in a better optimization performance than the PCA-based grey relational analysis method. However, the WPC method is preferable because of its simpler computational procedure.  相似文献   
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