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111.
H. Gao R. K. Dutta R. M. Huizenga M. Amirthalingam M. J. M. Hermans T. Buslaps 《Science & Technology of Welding & Joining》2014,19(3):256-264
In multipass welding, each successive thermal cycle will introduce local melting, solid state phase transformations, grain growth, grain refinement, recrystallisation and recovery, all of which lead to a complicated stress state. Most stress measurements performed on multipass welded components represent the final residual stress state. Information concerning stress evolution on a pass-by-pass basis is difficult to find. In this investigation, six pass welds were made on high strength quenched and tempered steel sections, and depth resolved strain measurements in two orthogonal directions were carried out after each weld pass using energy dispersive synchrotron X-ray diffraction. The residual stresses were calculated using biaxial Hooke’s law. A thermal–metallurgical–mechanical welding model was constructed and validated with temperature and pass-by-pass stress measurements, which improves the reliability of the model. Cross-sectional stress distributions are presented after each pass, revealing the weld stress development in multipass welds. 相似文献
112.
113.
Manisha Choudhury Lipi B. Mahanta Jayashree Sarmah Goswami Meenakshi Dutta Mazumder 《Food Control》2011,22(8):1233-1239
Successful food hygiene training and the consent of safe food handling practices learnt during training are critical elements in the control of food-borne illnesses throughout the world. It is true for food handlers and vendors belonging to all sectors. But, it is all the more urgent for street vendors because they are more exposed to environmental hazards and are predominantly from much weaker socio-economic backgrounds and yet cater to the general mass. Using a cross-sectional study design a sample of 80 street food vendors were selected and provided with training to evaluate the existing Knowledge, Attitude and Practice (KAP) regarding food safety and hygiene and the change of the same after training interventions. Responses regarding KAP on food safety and hygiene before and after training revealed that there was a significant change in their perception to food safety knowledge and also practices. The knowledge level of the food vendors increased from an average 24.35%–66.2% after training interventions. The overall performance rating of full adoption of good hygiene practices by the vendors ranged from 37.5% to 50.8% in post-training period. 相似文献
114.
115.
Pushkar N. Patil Sudarshan Kathi Dhanadeep Dutta Pradeep K. Pujari 《Polymer Bulletin》2010,65(6):577-587
Poly (N-isopropyl acrylamide) gels were prepared by UV polymerization with different degree of cross-linking in different solvents.
Ethylene glycol dimethacrylate and penta-erythritol tetra-acrylate were used as cross-linkers, and methanol and dimethyl formamide
(DMF) were used as solvents for gel preparation. The free volume fraction and hole size distribution in the dry gels were
measured using positron annihilation lifetime spectroscopy. The equilibrium swelling of the samples in water was measured
at room temperature. Both swelling properties of gels and the free volume distributions were seen to be sensitive to the amount,
type, and functionality of cross-linkers as well as solvent medium used for synthesis. The gels prepared in DMF showed poor
swelling properties than those prepared in methanol. The mean free volume hole size was higher while the variance of hole
size distribution was smaller in the gels prepared in DMF medium compared to those prepared in methanol. The free volume fractions
in the gels were found to be inversely correlated to the extent of equilibrium swelling for similar chemical compositions.
The possible reasons are discussed. 相似文献
116.
The technique of electrospinning offers the advantage of growing nanowires in bulk quantities in comparison with traditional
methods. We report optical studies of polycrystalline zinc oxide (ZnO) nanofibers (∼100 nm thick and 5 μm long) deposited by electrospinning. Photoluminescence from the nanofibers shows a near-ultraviolet (near-UV) peak corresponding
to near-band-edge emission and a strong broad peak in the visible region from oxygen antisite and interstitial defects. Temperature-dependent
photoluminescence spectroscopy reveals that different carrier recombination mechanisms are dominant at low temperature. Our
Raman spectroscopy results demonstrate that characterization of the quasimodes of longitudinal optical (LO) and transverse
optical (TO) phonons present in an ensemble of polycrystalline nanofibers tilted at various angles in addition to the dominant
E
2(high) mode provides a promising technique for assessing the quality of such randomly oriented nanowires. 相似文献
117.
Arvind Kumar Mike J. Walker Suresh Sundarraj Pradip Dutta 《Metallurgical and Materials Transactions B》2011,42(4):825-836
Experimental studies were performed to investigate the role and influence of grain movement on macrosegregation and microstructure
evolution during equiaxed solidification. Casting experiments were performed with a grain-refined Al-Cu alloy in a rectangular
sand mold. For the aluminum alloy studied, the equiaxed grains are lighter than the bulk melt and thus float up. Experiments
were designed to investigate floatation phenomena of equiaxed grains in the presence of thermosolutal convection. Cooling
curves were recorded at key locations in both the casting and the chill. Quantitative image analysis and spatial chemical
analysis were performed on the solidified casting to observe the chemical and microstructural inhomogeneity created by the
melt convection and solid floatation. Several notable features that can be attributed to grain movement were observed in temperature
histories, macrosegregation patterns, and microstructures. In our experiments, the floatation of grains influences the thermal
conditions and the overall flow direction in the casting cavity. In some cases, the induced flow resulting from the grain
movement caused a flow reversal. This in turn influences the solidification direction, microstructure evolution, and the overall
macrosegregation behavior. 相似文献
118.
Sunanda Mukhopadhyay Sarbasree Dutta Sheikh A. Ansar Sumita Das Susmita Misra 《Journal of the American Ceramic Society》2009,92(8):1895-1900
Oxidation resistance and water wettability of graphite flakes have been improved by a thin sol–gel film of magnesium aluminate spinel (MgAl2 O4 ) over its surface. The hydrosol has been synthesized by less expensive precursors and the spinel formation has been studied by scanning electron microscopy (SEM), supplemented with energy dispersive spectral analysis. After an easy-to-use mixing procedure, drying (110°C), and subsequent calcination (550°C), coated graphites were sieved to below 75 μm. The coating over the powder contained 1.5 wt% MgAl2 O4 , which enormously increased the oxidation resistance (performed at 600°, 900°, and 1200°C) and water wettability, as revealed by hydrophilic functional groups from infrared spectra. Defective, intermediate spinel structure of fine, lamellar Mg-doped γ-Al2 O3 has been considered to be significant for this improvement. An approximate (1:2) stoichiometry of (Mg:Al) in the coating composition was confirmed by an X-ray photoelectron spectroscopy test. Castables prepared by this graphite remarkably improved their bulk density and apparent porosity compared with those prepared by the as-received graphite. Casting water was reduced along with the amount of antioxidants. This also enhanced the resistance toward the basic slag by retaining the graphite in the refractory. 相似文献
119.
In this paper we report successful simple synthesis of unique elastic polyesters by carrying out catalyst-free polyesterification of multifunctional non-toxic monomers: 1,8-octanediol (OD), citric acid (CA) and sebacic acid (SA). The chemical, physical, and surface chemical properties of the resulting copolyester polyoctanediol citrate/sebacate [p(OCS)] have been investigated. This new material was characterized by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF-MS), nuclear magnetic resonance spectroscopy (NMR), thermal analysis (TA), mechanical tests, photo-acoustic Fourier-transform infrared spectroscopy (PA-FTIR), X-ray photoelectron spectroscopy (XPS) and swelling experiments. We demonstrate that the chemical structure, morphology, physical integrity and surface chemistry of the synthesized co-polymer can be controlled by simply varying the initial acid concentration (CA/SA) in the pre-polymer. This novel p(OCS) polymer exhibits versatility in mechanical properties, hydration and hydrolytic degradation as determined by the chemical structure of the polyester elastomer. 相似文献
120.
Characterization of melting process in a Phase Change Material (PCM)-based heat sink with plate fin type thermal conductivity enhancers (TCEs) is numerically studied in this paper. Detailed parametric investigations are performed to find the effect of aspect ratio of enclosure and the applied heat flux on the thermal performance of the heat sinks. Various non-dimensional numbers, such as Nusselt number (Nu), Rayleigh number (Ra), Stefan number (Ste) and Fourier number (Fo) based on a characteristic length scale, are identified as important parameters. The half fin thickness and the fin height are varied to obtain a wide range of aspect ratios of an enclosure. It is found that a single correlation of Nu with Ra is not applicable for all aspect ratios of enclosure with melt convection taken into account. To find appropriate length scales, enclosures with different aspect ratios are divided into three categories, viz. (a) shallow enclosure, (b) rectangular enclosure and (c) tall enclosure. Accordingly, an appropriate characteristic length scale is identified for each type of enclosure and correlation of Nu with Ra based on that characteristic length scale is developed. 相似文献