全文获取类型
收费全文 | 4849篇 |
免费 | 789篇 |
国内免费 | 191篇 |
专业分类
电工技术 | 514篇 |
综合类 | 347篇 |
化学工业 | 1311篇 |
金属工艺 | 263篇 |
机械仪表 | 183篇 |
建筑科学 | 212篇 |
矿业工程 | 430篇 |
能源动力 | 60篇 |
轻工业 | 386篇 |
水利工程 | 28篇 |
石油天然气 | 49篇 |
武器工业 | 46篇 |
无线电 | 348篇 |
一般工业技术 | 557篇 |
冶金工业 | 900篇 |
原子能技术 | 80篇 |
自动化技术 | 115篇 |
出版年
2024年 | 12篇 |
2023年 | 56篇 |
2022年 | 107篇 |
2021年 | 148篇 |
2020年 | 170篇 |
2019年 | 158篇 |
2018年 | 174篇 |
2017年 | 209篇 |
2016年 | 221篇 |
2015年 | 158篇 |
2014年 | 275篇 |
2013年 | 383篇 |
2012年 | 330篇 |
2011年 | 313篇 |
2010年 | 198篇 |
2009年 | 224篇 |
2008年 | 188篇 |
2007年 | 285篇 |
2006年 | 282篇 |
2005年 | 239篇 |
2004年 | 208篇 |
2003年 | 208篇 |
2002年 | 241篇 |
2001年 | 205篇 |
2000年 | 144篇 |
1999年 | 110篇 |
1998年 | 97篇 |
1997年 | 79篇 |
1996年 | 57篇 |
1995年 | 55篇 |
1994年 | 43篇 |
1993年 | 30篇 |
1992年 | 44篇 |
1991年 | 34篇 |
1990年 | 47篇 |
1989年 | 34篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1977年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有5829条查询结果,搜索用时 78 毫秒
41.
Epoxy adhesives filled with four different volume fractions of eutectic tin-bismuth solder alloy were prepared and the effect of filler content on the electrical and mechanical properties of these anisotropic electrically conductive adhesives was investigated. The results show that the adhesive containing the lowest amount of the filler alloy had the best combination of conductivity, insulation resistance and shear strength. The DSC-measurements suggested that the filler melts before the cure of the resin begins which allows the filler to wet and bond well to the conductors. This was verified by SEM/EPMA examinations. A temperature cycling test and high humidity, high temperature treatment were conducted on the best composite adhesive. The temperature variation had no effect on conductivity of the joints while humid and hot environment decreased the conductivity. 相似文献
42.
用DSC研究了高T_e超导体B_(2-r)Pb_rSr_2Ca_2Cu_sO_v(x=0,0.2,0.4,0.6)从室温至600℃范围内的相变。在320℃和440℃附近有二个吸热蜂,每一个峰对应一个相变过程。440℃附近的相变是不可递的,其原子激活能为1.37eV,是由高T_e相向低T_e相的转变。而320℃附近的相变则与超结构的形成有关。 相似文献
43.
44.
Ping-Hua Xiang Xian-Lin Dong Chu-De Feng Yong-Ling Wang 《Journal of the American Ceramic Society》2003,86(9):1631-1634
NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO3 )2 ·6H2 O, and NH4 HCO3 as the starting materials. The amorphous NiCO3 ·2Ni(OH)2 ·2H2 O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ∼8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ∼30 nm. 相似文献
45.
分析用水水质对日用陶瓷铅溶出量测定具有重要影响,CL-、SO42-、CO2等严重抑制铅的溶出,使测定结果偏低。 相似文献
46.
47.
48.
Lisbeth M Ottosen Ana T Lima Anne J Pedersen Alexandra B Ribeiro 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(4):553-559
The possibility of using fly ash from municipal solid waste incineration (MSWI) in, for example, concrete is considered. MSWI fly ash, however, has too high a concentration of heavy metals, which may cause leaching problems during use or problems with waste handling at the end of the lifetime of the concrete. The Cl content in MSWI fly ash is also too high and will cause corrosion problems in reinforced concrete. The possibility of removing some of the unwanted heavy metals (Cu and Pb) together with Cl from an MSWI fly ash suspended in water using an electrodialytic separation method was investigated. The removal of Pb and Cu was found to be highly pH dependent and the highest contents removed were 41 and 90%, respectively. The Cu concentration of the ash decreased from 2200 to 860 mg kg?1 but the Pb concentration increased from 8560 to 16 800 mg kg?1, showing that Pb is mainly found in the ash fraction that is least soluble. Hence electrodialytic treatment of the ash suspended in water is not a solution to improve the ash quality in terms of Pb. The water‐soluble Cl content per unit weight of the original ash was 12.4%. The removal of water‐soluble Cl was efficient and >98% of Cl was removed (calculated on the basis of mean initial and final concentrations). This result indicates that electrodialytic extraction may be a method that can be used for the removal of Cl from ash prior to its utilization in concrete. Copyright © 2006 Society of Chemical Industry 相似文献
49.
新型环氧防腐涂料的研究 总被引:1,自引:0,他引:1
采用在环氧树脂中加入纳米复合铁钛粉防锈颜料WD—D-325、固化剂、制备了新型环氧树脂防腐涂料。由于纳米技术的特性,该防腐涂料具有较高的防腐性、优异的附着力和柔韧性。实验确定了复合铁钛粉防锈颜料在环氧防腐涂料中的添加量。作为新型的环保颜料,复合铁钛粉防锈颜料可以替代红丹、锌铬黄等颜料。 相似文献
50.
Yasuyuki Matsumura Shigeru Sugiyama Hiromu Hayashi John B. Moffat 《Catalysis Letters》1994,30(1-4):235-240
The introduction of small quantities of lead into calcium hydroxyapatite catalysts produces marked increases in the selectivity to C2+ hydrocarbons, while the conversion of methane remains relatively constant. Small surface concentrations of lead are sufficient to achieve C2+ selectivities of 80 and 90%, with oxygen and nitrous oxide, respectively, in contrast with 18 and 46%, respectively, obtained in the absence of lead. Since surface concentration of lead species sufficient to stabilize pairs of methyl radicals in close proximity to each other would be expected to facilitate the formation of C2 hydrocarbons, an ensemble effect appears to be extant. 相似文献