全文获取类型
收费全文 | 10196篇 |
免费 | 671篇 |
国内免费 | 232篇 |
专业分类
电工技术 | 25篇 |
技术理论 | 1篇 |
综合类 | 204篇 |
化学工业 | 5592篇 |
金属工艺 | 2424篇 |
机械仪表 | 324篇 |
建筑科学 | 131篇 |
矿业工程 | 48篇 |
能源动力 | 130篇 |
轻工业 | 186篇 |
水利工程 | 17篇 |
石油天然气 | 24篇 |
武器工业 | 29篇 |
无线电 | 275篇 |
一般工业技术 | 1385篇 |
冶金工业 | 265篇 |
原子能技术 | 25篇 |
自动化技术 | 14篇 |
出版年
2024年 | 25篇 |
2023年 | 192篇 |
2022年 | 181篇 |
2021年 | 321篇 |
2020年 | 336篇 |
2019年 | 294篇 |
2018年 | 308篇 |
2017年 | 259篇 |
2016年 | 240篇 |
2015年 | 262篇 |
2014年 | 517篇 |
2013年 | 593篇 |
2012年 | 619篇 |
2011年 | 807篇 |
2010年 | 706篇 |
2009年 | 594篇 |
2008年 | 632篇 |
2007年 | 666篇 |
2006年 | 722篇 |
2005年 | 567篇 |
2004年 | 512篇 |
2003年 | 338篇 |
2002年 | 224篇 |
2001年 | 183篇 |
2000年 | 172篇 |
1999年 | 186篇 |
1998年 | 174篇 |
1997年 | 113篇 |
1996年 | 80篇 |
1995年 | 54篇 |
1994年 | 49篇 |
1993年 | 36篇 |
1992年 | 31篇 |
1991年 | 31篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Molds made of gray cast iron for casting pig iron ingots are subjected to severe temperature fluctuations. The main life-
limiting factor for mold damage is the formation of surface cracks arising from thermal fa-tigue. Various flame and plasma
sprayed coatings were investigated to extend the life of these molds. Coating materials studied include plasma sprayed ceramic
coatings with bond coats as well as flame sprayed oxidation- resistant alloy powders. The results of cyclic furnace tests
from room temperature to 1100 °C in air, simulating the thermal cycle in casting, indicated that failure occurred along the
interface between the bond coat and the gray iron substrate because of iron oxidation, and not at the interface between the
ceramic top coat-ing and the bond coating for a superalloy substrate. The field test results indicated that plasma sprayed
alumina coatings with 200 μm top coating thickness are the most promising materials for pig iron casting. 相似文献
43.
Austenitic Mn-Al alloys (20–32 W/O Mn, 7–10 Al, 2–3 Si, 1C) were found to have satisfactory oxidation resistance up to 950°C under isothermal conditions in air. Surface enrichment of aluminum is a necessary condition for obtaining an almost pure alumina scale for uses at higher temperatures. Four different Mn-steels were Al-coated by the Capuano electroplating process. In all the steels there was an increase in the hot-oxidation resistance. The best results were obtained with steels containing both Al and Si, and this for temperatures up to 1100°C. No spalling was noticed during rapid cooling of the test pieces. Silicon was found to act as a diffusion barrier to outward iron diffusion. It appears that there is formation of a pure, thin film of alumina from the matrix which interacts with the aluminum diffusing from the superimposed, coating for the formation of good bonds. 相似文献
44.
45.
46.
47.
Low-Thermal-Conductivity Rare-Earth Zirconates for Potential Thermal-Barrier-Coating Applications 总被引:9,自引:0,他引:9
Jie Wu Xuezheng Wei Nitin P. Padture Paul G. Klemens Maurice Gell Eugenio García Pilar Miranzo Maria I. Osendi 《Journal of the American Ceramic Society》2002,85(12):3031-3035
Rare-earth zirconates have been identified as a class of low-thermal-conductivity ceramics for possible use in thermal barrier coatings (TBCs) for gas-turbine engine applications. To document and compare the thermal conductivities of important rare-earth zirconates, we have measured the thermal conductivities of the following hot-pressed ceramics: (i) Gd2 Zr2 O7 (pyrochlore phase), (ii) Gd2 Zr2 O7 (fluorite phase), (iii) Gd2.58 Zr1.57 O7 (fluorite phase), (iv) Nd2 Zr2 O7 (pyrochlore phase), and (v) Sm2 Zr2 O7 (pyrochlore phase). We have also measured the thermal conductivity of pressureless-sintered 7 wt% yttria-stabilized zirconia (7YSZ)—the commonly used composition in current TBCs. All rare-earth zirconates investigated here showed nearly identical thermal conductivities, all of which were ∼30% lower than the thermal conductivity of 7YSZ in the temperature range 25°–700°C. This finding is discussed qualitatively with reference to thermal-conductivity theory. 相似文献
48.
通过选用透明度高、太阳能吸收率高的丙烯酸树脂和高亮度、长余辉时间的镝和铕稀土离子共掺杂的稀土硅酸盐光致发光粉末材料aCaO·bZnO·cBaO·dMgO·nSiO2:Eu,Dy,制备出了具有较强的蓄光能力和较长发光时间的夜光涂料,并论述了其制备方法和特性。 相似文献
49.
Summary: A semi‐batch process using nitroxide mediated polymerization, was explored for the design of low molecular weight solvent‐borne coatings, typical of those used in the automotive industry. While living radical polymerization (LRP) offers many advantages in the control of polymer chain microstructure that may confer important physical and chemical property benefits to coatings, adapting LRP to a semi‐batch process poses significant challenges in the design and operation of the process. Using styrene monomer, various two‐component initiating systems (free radical initiator, 4‐hydroxy‐TEMPO) were studied to understand the effects of different initiators on the course of polymerization. In addition, an alkoxyamine was synthesized and used as the initiating source. The initiators Luperox 7M75 and Luperox 231 give higher polymerization rates and reasonable control over polymerization, while benzoyl peroxide (BPO), Vazo 67, and the alkoxyamine are less effective. The number of polymer chains in the final product is always less than the theoretical value, reflecting poor initiation efficiency, probably resulting from undesirable termination reactions that become important due to the nature of the semi‐batch process. Adding camphorsulfonic acid (CSA) or charging initiator concurrently with monomer during semi‐batch feed, can increase the polymerization rate while maintaining the living character of the polymerization. The copolymerization of styrene and butyl acrylate is also shown to exhibit living character.