全文获取类型
收费全文 | 58257篇 |
免费 | 5678篇 |
国内免费 | 3381篇 |
专业分类
电工技术 | 2049篇 |
综合类 | 4531篇 |
化学工业 | 10453篇 |
金属工艺 | 6072篇 |
机械仪表 | 6119篇 |
建筑科学 | 3418篇 |
矿业工程 | 2018篇 |
能源动力 | 1582篇 |
轻工业 | 7802篇 |
水利工程 | 1645篇 |
石油天然气 | 1644篇 |
武器工业 | 581篇 |
无线电 | 4601篇 |
一般工业技术 | 8107篇 |
冶金工业 | 2042篇 |
原子能技术 | 571篇 |
自动化技术 | 4081篇 |
出版年
2024年 | 360篇 |
2023年 | 1138篇 |
2022年 | 1588篇 |
2021年 | 1898篇 |
2020年 | 2174篇 |
2019年 | 1972篇 |
2018年 | 2010篇 |
2017年 | 2343篇 |
2016年 | 2319篇 |
2015年 | 2403篇 |
2014年 | 3186篇 |
2013年 | 4074篇 |
2012年 | 4133篇 |
2011年 | 4268篇 |
2010年 | 3014篇 |
2009年 | 3018篇 |
2008年 | 2873篇 |
2007年 | 3607篇 |
2006年 | 3332篇 |
2005年 | 2691篇 |
2004年 | 2233篇 |
2003年 | 1906篇 |
2002年 | 1718篇 |
2001年 | 1396篇 |
2000年 | 1265篇 |
1999年 | 1058篇 |
1998年 | 855篇 |
1997年 | 796篇 |
1996年 | 709篇 |
1995年 | 533篇 |
1994年 | 480篇 |
1993年 | 402篇 |
1992年 | 318篇 |
1991年 | 217篇 |
1990年 | 235篇 |
1989年 | 165篇 |
1988年 | 146篇 |
1987年 | 76篇 |
1986年 | 88篇 |
1985年 | 74篇 |
1984年 | 58篇 |
1983年 | 50篇 |
1982年 | 47篇 |
1981年 | 13篇 |
1980年 | 24篇 |
1979年 | 16篇 |
1977年 | 3篇 |
1959年 | 7篇 |
1955年 | 3篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
高速气流冲击式粉体表面改性装置——HYBRIDIZATION系统及应用 总被引:4,自引:0,他引:4
利用高速气流冲击法进行粉体/粉体系表面改性技术,是迄今为止各种粉体材料开发中最为引人注目的技术之一。HYBRIDIZATION(下称HYB)系统是利用高速气流冲击法对微粉体进行干式/机械化处理,是使材料复合化的最实用的装置,可对各类有机物、无机物、金属等进行广泛组合,通用性很强,适用于许多行业领域。从本文所述的系统构成、型式,有关的典型球形化处理的运转特性,利用复合化高温粉体测定被处理粉体表面温度,利用颜料改变色调等的处理特点及该系统的适用性等(一部分是从已发表的学术论文及专利上摘录的),可以说明HYB系统的概况。 相似文献
43.
44.
Spectroscopic evidence for the interaction of hydroxyl groups and chromium ions was obtained using a catalyst prepared from chromyl chloride. A new OH peak, observed at 3705 cm–1 after pumping away CO gas, is attributed to the direct interaction of OH with the low-valent chromium. This peak shifts to 3590 cm–1 on contact with O2 at room temperature and it is assigned to a hydroxyl interacting with the oxidized chromium. New assignments are also proposed for IR bands of CO presorbed on the catalyst. The peak due to CO at 2188 cm–1 decreases as the OH intensity at 3705 cm–1 increases, suggesting that the former peak arises from adsorption on Cr(II) species to which two oxygen atoms are attached. 相似文献
45.
Carbon Aerogels as Electrode Material in Supercapacitors 总被引:5,自引:0,他引:5
U. Fischer R. Saliger V. Bock R. Petricevic J. Fricke 《Journal of Porous Materials》1997,4(4):281-285
Due to their large specific surface area and their high electrical conductivity carbon aerogels are promising materials for electrodes in electrochemical double-layer capacitors (supercapacitor). The carbon aerogels were made via pyrolysis of resorcinol formaldehyde aerogels. The latter were prepared by supercritical and subcritical drying as well. The important findings of our investigation were, that the highest capacities of 46 F/cm3 were measured for samples with a density of about 800 kg/m3 pyrolyzed at 800°C. Also it was shown that RF-gels with molar resorcinol/catalyst ratios 1000 or higher can be dried subcritically without cracking or significant shrinkage. Carbon aerogels derived from these RF-aerogels have a small mesopore surface area, however an especially large micropore area. They provide electrical capacities which are most suitable for their use in supercapacitors. 相似文献
46.
ABSTRACT In this research, the effect of particle size on the surface oxidation and flotation behavior of galena in the lime system was studied. Coarse (?0.074 + 0.038 mm), intermediate (?0.038 + 0.025 mm) and fine (?0.025 mm) galena particles were used in the experiment. The dissolution tests, flotation tests, and sorption tests were accomplished. Through further analysis by XPS, the effect of particle size and lime was observed. The decrease of mineral particle sizes increased the adsorption ratio of collector and the dissolution of galena, while the hydrophilic product OH?/Ca(OH)+ produced by dissolution occupied the dominant position, which led to the minerals hydrophilic. 相似文献
47.
碳纤维(CF)表面经氧等离子、KH550和 LiAlH_4处理后,其物理和化学性能得以改善.由于提高了 CF 和树脂间的联结,使 CF 复合材料的层间剪切强度提高50%以上,在湿热下的强度保留率达94%以上.使用纤维接触角测定仪,SEM 和 XPS 等对 CF 表面的浸润性、形态和化学组成进行了研究.实验指出:CF 经等离子和 KH550处理后,其临界表面能有了提高;CF 本身仅受氧离子刻蚀,故其拉伸强度的损失小于其他处理方法. 相似文献
48.
49.
50.
A number of methods of surface preparation of tantalum for encapsulation in silicone rubber and for structural adhesive bonding were explored. The only ones which could be generally useful were boiling for 24 hours in distilled water (28% improvement) or boiling for 4 hours in 20% sodium hydroxide solution followed by boiling for 2 hours in dilute hydrochloric acid (34% improvement). An alternative, which could sometimes be used, was heating in air for at least 2 hours at 100°C. 相似文献