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排序方式: 共有221条查询结果,搜索用时 15 毫秒
1.
The aims of this study were to determine the most appropriate duration for the measurement of the maximal accumulated O2 deficit (MAOD), which is analogous to the anaerobic capacity, to ascertain the effects of mass, fat free mass (FFM), leg volume (Vleg) and lower body volume (V1b) on anaerobic test performance, to examine the reproducibility for peak power output (Wpeak) or maximal anaerobic power using an air-braked cycle ergometer and to produce approximations for the percentages of aerobic and anaerobic metabolism during exercise of short duration but high intensity. A group of 12 endurance trained cyclists [mean age 25.1 (SD 4.6) years; mean body mass 73.43 (SD 7.12) kg; mean maximal oxygen consumption 5.12 (SD 0.35) l.min-1; mean body fat 12.5 (SD 4.1) %] accordingly performed four counterbalanced treatments of 45, 60, 75 and 90 s of maximal cycling on an air-braked ergometer. The mean O2 deficit of 3.52 l for the 45-s treatment was significantly less (P < 0.01) than those for the 60 (3.75 l), 75 (3.80 l) and 90-s (3.75 l) treatments. These data therefore indicate that in predominantly aerobically trained subjects the O2 deficit attains a plateau after 60 s of maximal cycling on an air-braked ergometer. Statistically significant interclass correlation coefficients (P < 0.05) between the anthropometric variables (mass, FFM, Vleg and Vlb) and Wpeak or maximal anaerobic power (0.624-0.748) and MAOD (ml) or anaerobic capacity (0.666-0.772) furthermore would suggest the relevance of taking into account muscle mass during anaerobic tests.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
2.
Over the last few years, Polaroid has been actively trying to reduce the amount of waste produced at its sites. In this article, Ian McKeown looks at the measures taken at the UK site in Scotland to achieve this aim.  相似文献   
3.
Small-angle X-ray and small-angle neutron scattering studies have been carried out on poly(vinyl chloride) (PVC), and blends of PVC with solution-chlorinated polyethylene (SCPE) and poly(butyl acrylate) (PBA). The PVC used was commercial (suspension-polymerized) or bulk-polymerized. The blends of PVC with PBA were prepared by solvent-casting and those with SCPE by in situ polymerization. PVC samples show shoulders in the scattering spectra, presumably due to crystallites, which persist even in samples which have been solvent cast. Blends of PVC with PBA also show a peak but at a higher ‘d’ spacing. The blends with SCPE which were prepared by in situ polymerization show no such peak. This suggests that the method of preparation prevents the formation of crystallites. An increase in scattering of the PBA blends was observed when the samples were heated to the temperature of phase separation. Neutron scattering studies were also carried out using 2% deuterium labelled PVC in PVC and in the blends. In the PVC this showed chain dimensions in good agreement with predicted values. In the blends, dimensions of the same order were obtained, confirming a molecular dispersion of chains in the single phase, but there was an apparent reduction in the chain dimensions. This could be explained by a true reduction in dimensions or a non-zero A2 value in the blends.  相似文献   
4.
A sufficiently thin column of liquid was produced to permit penetration with a 200 keV electron beam as evidenced by the observation of diffraction rings due to the intermolecular spacing of the liquid samples. For liquid thickness below 800 nm, the diffraction rings became visible above the inelastic background. Studies were carried out in the environmental chamber of a transmission electron microscope using water and isopropanol.  相似文献   
5.
Catchpole K  McKeown D 《Ergonomics》2007,50(8):1287-1301
Ambulance sirens are essential for assisting the safe and rapid arrival of an ambulance at the scene of an emergency. In this study, the parameters upon which sirens may be designed were examined and a framework for emergency vehicle siren design was proposed. Validity for the framework was supported through acoustic measurements and the evaluation of ambulance transit times over 240 emergency runs using two different siren systems. Modifying existing siren sounds to add high frequency content would improve vehicle penetration, detectability and sound localization cues, and mounting the siren behind the radiator grill, rather than on the light bar or under the wheel arch, would provide less unwanted noise while maintaining or improving the effective distance in front of the vehicle. Ultimately, these considerations will benefit any new attempt to design auditory warnings for the emergency services.  相似文献   
6.
Rule-based interpretation of aerial imagery   总被引:5,自引:0,他引:5  
In this paper, we describe the organization of a rule-based system, SPAM, that uses map and domain-specific knowledge to interpret airport scenes. This research investigates the use of a rule-based system for the control of image processing and interpretation of results with respect to a world model, as well as the representation of the world model within an image/map database. We present results on the interpretation of a high-resolution airport scene wvhere the image segmentation has been performed by a human, and by a region-based image segmentation program. The results of the system's analysis is characterized by the labeling of individual regions in the image and the collection of these regions into consistent interpretations of the major components of an airport model. These interpretations are ranked on the basis of their overall spatial and structural consistency. Some evaluations based on the results from three evolutionary versions of SPAM are presented.  相似文献   
7.
We provide an overview of two multimedia generation systems developed at Columbia University, COMET and MAGIC, and analyze them using the standard reference model for intelligent multimedia presentation systems. COMET (Coordinated Multimedia Explanation Testbed) emphasizes the coordinated generation of text and 3D graphics in a military maintenance and repair documentation domain. It features support for automated determination of what information to present, assignment of information to appropriate media and generation of textual cross-references to the structure and content of generated graphics, including the automated redesign of graphics to make possible better cross-references. MAGIC (Multimedia Abstract Generation for Intensive Care) generates presentations that use temporal media, including speech and animation, to explain the status of hospital patients. It extends the media coordination approach used in COMET to include a multi-stage negotiation process that solves temporal constraints imposed by individual media generators to determine when and for how long actions should occur in each medium.  相似文献   
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9.
Four proteins, α/β globulin, serum albumin, γ‐globulin and fibrinogen, were isolated from bovine blood and hydrolysed using papain. Hydrolysates were assessed for non‐cellular and cellular antioxidant activity. The anti‐proliferative activity of hydrolysed fractions was assessed in a number of cancer cell lines including U937 lymphoma cells, MCF‐7 breast cancer cells, HepG2 hepatocytes and Caco‐2 epithelial colorectal adenocarcinoma cells. Anti‐inflammatory activity of the hydrolysates was also assessed. Hydrolysates generated from γ‐globulin or fibrinogen had significant antioxidant activity in non‐cellular assays. Hydrolysates were also found to be highly toxic to different cancer cell lines, in particular U937 lymphoma cells when assessed using the MTT assay. The fibrinogen hydrolysate was the most toxic sample and toxicity appeared to correlate with its non‐cellular antioxidant activity. None of the hydrolysates had significant anti‐inflammatory activity. The high cytotoxicity of the γ‐globulin and the fibrinogen hydrolysates towards cancer cells may indicate a potential use as anti‐proliferative agents.  相似文献   
10.
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