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1.
The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstructure showed fine cell and columnar structure due to high cooling rate.Ti element segrega-tion was observed in inter-cell/inter-columnar area.After post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni3(Al,Ti)particles formed.High temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure.The as-built IN738LC fabricated via the selective laser melting process displayed oxida-tion resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process.Heat-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM as-built material at 1273 K,showed relatively better oxidation resistance at 1373 K.Bimodal Ni3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy surface.It was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain. 相似文献
2.
In this research, deep consolidation technique is utilized for processing of low and high carbon content ferrous powders to manufacture composite material. High carbon content ferrous powders were used as reinforcing material. The powder particles were allowed to mix with low carbon content ferrous powders in 50:50 weight percent for fabrication of composites. The composites were heat treated at three different temperatures (i.e., 800°C, 900°C, and 1000°C). The changes in microstructure, microhardness, the grain size, and bonding among powder particles were studied. Refinement of grains was observed and this led to improved hardness enabling the processed material to be used as a suitable composite. Abrasive wear tests were carried out using a laboratory tribometer in dry reciprocating sliding contact against Sic abrasive paper. The outcomes demonstrate that the abrasive wear resistance was notably affected by the treatment temperature and hardness of the composites. 相似文献
3.
This study investigated the effect of centrifugation (9,000 × g, 50°C, flow rate = 1,000 L/h), as well as the incorporation of high-heat-treated (HHT) centrifugate into cheese milk on the composition, texture, and ripening characteristics of Maasdam cheese. Neither centrifugation nor incorporation of HHT centrifugate into cheese milk had a pronounced effect on the compositional parameters of any experimental cheeses, except for moisture and moisture in nonfat substance (MNFS) levels. Incorporation of HHT centrifugate at a rate of 6 to 10% of the total milk weight into centrifuged milk increased the level of denatured whey protein in the cheese milk and also increased the level of MNFS in the resultant cheese compared with cheeses made from centrifuged milk and control cheeses; moreover, cheese made from centrifuged milk had ~3% higher moisture content on average than control cheeses. Centrifugation of cheese milk reduced the somatic cell count by ~95% relative to the somatic cell count in raw milk. Neither centrifugation nor incorporation of HHT centrifugate into cheese milk had a significant effect on age-related changes in pH, lactate content, and levels of primary and secondary proteolysis. However, the value for hardness was significantly lower for cheeses made from milk containing HHT centrifugate than for other experimental cheese types. Overall, centrifugation appeared to have little effect on composition, texture, and ripening characteristics of Maasdam cheese. However, care should be taken when incorporating HHT centrifugate into cheese milk, because such practices can influence the level of moisture, MNFS, and texture (particularly hardness) of resultant cheeses. Such differences may have the potential to influence subsequent eye development characteristic, although no definitive trends were observed in the present study and further research on this is recommended. 相似文献
4.
在熔体温度为2323 K,抽拉速率为100 μm/s的条件下对Nb-Ti-Si基超高温合金进行了有坩埚整体定向凝固 (DS),然后对定向凝固试样进行了两种不同工艺的热处理:即1723 K/50 h高温均匀化处理 (HT1) 和1623 K/50 h 1723 K/50 h 1373 K/50 h复合热处理 (HT2)。采用XRD,SEM和EDS等分析手段研究热处理对定向凝固合金微观组织及其力学性能的影响。结果表明,热处理后合金中大尺寸初生硅化物的体积分数下降,两种方式的热处理均能有效减轻甚至消除合金中的成分偏析。热处理后原DS试样中Nbss (Nb,X)5Si3共晶胞的边界完全消失。相比HT1处理,HT2处理后试样中硅化物的分布更加均匀。与DS试样相比,经HT2处理后试样的室温断裂韧性值增加了12.3% (约19.2 MPa?m1/2),且其拉伸强度增加了26.6% (最大值达到933.2MPa)。力学性能的改善主要归因于热处理后组织中 (Nb,X)5Si3颗粒弥散分布以及韧性Nbss相的形状、尺寸及含量均发生变化。 相似文献
5.
采用磁控溅射制备含1.16%~15.8%(原子分数)Nb的Cu-Nb及含2.2%~27.8%Mo的Cu-Mo合金薄膜,井采用EDX、XRD、SEM、显微硬度仪和电阻计对薄膜的成分、结构和性能进行研究。结果表明,Nb和Mo的添加分别使Cu-Nb及Cu-Mo薄膜晶粒显著细化,Cu-Nb和Cu-Mo薄膜呈纳米晶结构,存在Nb在Cu中的fcc Cu(Nb)和Mo在Cu中的fcc Cu(Mo)非平衡亚稳过饱和固溶体,固溶度随Nb或Mo含量增加而上升。添加Nb和Mo显著提高Cu-Nb及Cu-Mo薄膜的显微硬度和电阻率,且随Nb或Mo含量增加而升高。经650℃热处理1h后,Cu-Nb和Cu-Mo薄膜显微硬度和电阻率均下降,且分析表明均发生基体相晶粒长大,并出现微米-亚微米级富Cu第二相,Cu-Nb及Cu-Mo薄膜结构和性能形成及演变的主要原因是添加的Nb、Mo引起的晶粒细化效应以及退火中基体相晶粒度的增大。 相似文献
6.
The effects of spinning deformation and subsequent heat treatments on the mechanical properties and microstructure of 18Ni Co-free Maraging steel (T250) tube were evaluated comparatively with the perform. An obvious radial shrinkage is detected in spun tubes after heat treatment and the magnitude of the shrinkage induced by solution treatment is almost the same as that by aging. Plastic deformation during spinning elongated the grains severely in the direction of metal flow. The solution treatment resulted in a drastically refined grain and recrystallised microstructure, removing the effect of plastic deformation, relieving the tangential residual stress and strain and improving hardness. Subsequent aging obtained a tempered microstructure, enhancing hardness values strikingly for precipitation strengthening. XRD (X-ray diffraction) analysis indicated that the reversed austenite formed in a plate-like along the grain boundaries and the volume fraction of austenite in spun tube was more than double that in the preform. These results imply that the residual stress and stain induced by spinning process and reversed austenite forming during aging might have the similar contribution to the radical shrinkage. 相似文献
7.
折叠箱内铰链是折叠箱中较关键的部件,一直采用钢板割焊生产,材料利用率低,工序多,成本高.为提高生产效率,降低成本,折叠箱生产厂家决定采用铸造方法生产.根据内铰链的工况要求,需开发出一种低成本、高屈服强度的焊接结构钢生产内铰链.参照焊接结构钢化学成分的要求,设计较低的贵重金属Cr、M0、Cu含量,并通过870℃油淬及580℃的回火热处理,材料达到了折叠箱内铰链铸钢件的要求,即焊接性能好,屈服强度≥390MPa,而且有较好的韧性.生产加工后的内铰链铸件产品完全满足使用要求,内铰链的生产完全可以由铸件生产代替钢板割焊生产. 相似文献
8.
9.
针对旅大原油高含蜡特性,比较了本实验优选合成的EVA改性型降凝剂ZLX-01与市售7种降凝剂对旅大原油的降凝效果,并探讨了影响加剂效果的因素。实验结果表明,旅大原油最佳热处理温度为50~55℃,降凝剂ZLX-01最优加剂量为300 mg/L,原油凝点由加剂前的22℃降至9℃,反常点由加剂前的35℃降至30℃。在原油温度25℃、剪速12 1/s下,加入300 mg/L的降凝剂ZLX-01后,原油表观黏度由加剂前的420 mPa.s降至116 mPa.s,降黏率为72.4%。重复加热温度低于40℃时会恶化加剂原油的低温流变性,此外加有ZLX-01的原油还具有较好的静态稳定性。图2表4参2 相似文献
10.
通过优化设计与控制C,Ni,Cr主合金元素和H,O,N气体元素含量,优化管材冷轧工艺,有效防止了1Cr13管材加工时的开裂现象,保证了管材表面质量良好;通过调整成品热处理工艺,使试制的管材样件的力学性能完全满足了技术条件要求. 相似文献