全文获取类型
收费全文 | 34766篇 |
免费 | 2897篇 |
国内免费 | 1722篇 |
专业分类
电工技术 | 1148篇 |
综合类 | 1268篇 |
化学工业 | 12174篇 |
金属工艺 | 3203篇 |
机械仪表 | 465篇 |
建筑科学 | 400篇 |
矿业工程 | 1304篇 |
能源动力 | 3748篇 |
轻工业 | 1137篇 |
水利工程 | 49篇 |
石油天然气 | 822篇 |
武器工业 | 69篇 |
无线电 | 2561篇 |
一般工业技术 | 6863篇 |
冶金工业 | 3363篇 |
原子能技术 | 354篇 |
自动化技术 | 457篇 |
出版年
2024年 | 131篇 |
2023年 | 758篇 |
2022年 | 1102篇 |
2021年 | 1413篇 |
2020年 | 1317篇 |
2019年 | 1263篇 |
2018年 | 1175篇 |
2017年 | 1240篇 |
2016年 | 1179篇 |
2015年 | 1137篇 |
2014年 | 1743篇 |
2013年 | 1971篇 |
2012年 | 2220篇 |
2011年 | 2760篇 |
2010年 | 2119篇 |
2009年 | 2003篇 |
2008年 | 1763篇 |
2007年 | 2077篇 |
2006年 | 1838篇 |
2005年 | 1479篇 |
2004年 | 1318篇 |
2003年 | 1175篇 |
2002年 | 1084篇 |
2001年 | 810篇 |
2000年 | 821篇 |
1999年 | 598篇 |
1998年 | 527篇 |
1997年 | 410篇 |
1996年 | 353篇 |
1995年 | 271篇 |
1994年 | 251篇 |
1993年 | 181篇 |
1992年 | 181篇 |
1991年 | 146篇 |
1990年 | 135篇 |
1989年 | 98篇 |
1988年 | 65篇 |
1987年 | 40篇 |
1986年 | 29篇 |
1985年 | 39篇 |
1984年 | 31篇 |
1983年 | 21篇 |
1982年 | 32篇 |
1981年 | 25篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1977年 | 5篇 |
1974年 | 5篇 |
1959年 | 5篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
Charles A. Bateman Lijie Zhang Helen M. Chan Martin P. Harmer 《Journal of the American Ceramic Society》1992,75(5):1281-1283
It is experimentally observed that the peritectic reaction, 211 + liquid → 123, can be driven essentially to completion in 1 h at an undercooling of only ∽30°C. The kinetic data, together with the observed microstructures, are inconsistent with the normal mechanism of the peritectic reaction. It is proposed that the mechanism of the reaction involves dissolution of 211 particles into the liquid and precipitation of solid 123. The aligned grain structure is explained through sympathetic nucleation of new 123 grains on existing grains. 相似文献
52.
53.
54.
Lanthanum doped nickel and YSZ composite anode (LaNi–YSZ) exhibited a greatly reduced polarization resistance and high performance for electrochemical oxidation of hydrogen and methane, which resulted from a fine anode structure with a high dispersion of nickel catalyst and a high catalytic activity towards methane. 相似文献
55.
用共沉淀法制备了TiO2-ZrO2复合氧化物载体,BET,DTA,XRD表征结果表明,该复合载体具有较大的比表面和较好的热稳定性,对于环己酮肟气相Beckmann重排反应制己内酰胺,用复合载体制备的B2O3/TiO2-ZrO2催化剂,比分别以TiO2,ZrO2为载体所制备的B2O3/TiO2和B2O3/ZrO2催化剂具有更高的活性和选择性,实验表明,催化剂表面中等强度的酸位是环己酮肟气相Beckmann重排反应的有效活性中心。 相似文献
56.
中国软磁铁氧体用氧化铁 总被引:1,自引:0,他引:1
介绍了中国软磁铁氧体用氧化铁的发展历史和现状,预测了未来的市场需求,并探讨了氧化铁的应用技术问题。 相似文献
57.
Hari B. Goyal M. O. Garg K. R. Rao R. D. Srivastava 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(2):49-56
The kinetics of the reaction of acetic acid and acetylene over zinc acetate-activated carbon catalyst was investigated over a wide range of process variables in a pilot reactor. Although various catalytic reaction mechanisms were postulated, the rate of reaction was most satisfactorily correlated by a mechanism of surface reaction between charged adsorbed acetic acid and acetylene, which assumes that the rate controlling step was the irreversible charged adsorption of acetylene and acetic acid. 相似文献
58.
K. Chatty T. P. Chow R. J. Gutmann E. Arnold D. Alok 《Journal of Electronic Materials》2002,31(5):356-360
Hall measurements have been used to compare the properties of 4H-SiC inversion-mode MOSFETs with “wet” and “dry” gate oxides.
While the field-effect mobilities were approximately 3–5 cm2/Vs, the Hall mobilities in 4H-SiC MOSFETs in the wet and dry oxide samples were approximately 70–80 cm2/Vs. The dry-oxidized metal oxide semiconductor field effect transistors (MOSFETs) had a higher transconductance, improved
threshold voltage, improved subthreshold slope, and a higher inversion carrier concentration compared to the wet-oxidized
MOSFETs. The difference in characteristics between the wet- and the dry-oxidized MOSFETs is attributed to the larger fixed
oxide charge in the dry oxide sample and a higher interface trap density in the wet oxide sample. 相似文献
59.
The influence of convective heat transfer on constant current density anodizing of aluminium in sulfuric acid has been examined in a wall-jet electrode reactor. The uniformity of the anodic film thickness is related to the local electrode temperature distribution, which is dependent on the convection. The higher the local temperature, the greater the local oxide thickness. An increased local temperature enhances local field assisted oxide dissolution at the pore bases, and consequently acts to increase the local current density. At relatively high current densities, local features develop on the electrode surface, accompanied by high initial, local temperature rises. The relevance of such local features, limiting useful oxide growth, is considered further. 相似文献
60.
D Ganguli 《Bulletin of Materials Science》1993,16(6):523-531
The various parameters related to sol-gel processing are discussed with special reference to those which usually attract less
attention but depending on the final product in mind, can play important roles. The versatility of the sol-gel technique in
materials preparation is demonstrated by discussing the various products developed at the author’s laboratory by using this
processing method. 相似文献