全文获取类型
收费全文 | 95242篇 |
免费 | 6997篇 |
国内免费 | 3630篇 |
专业分类
电工技术 | 5085篇 |
技术理论 | 8篇 |
综合类 | 5861篇 |
化学工业 | 16178篇 |
金属工艺 | 5073篇 |
机械仪表 | 6178篇 |
建筑科学 | 7049篇 |
矿业工程 | 3038篇 |
能源动力 | 2817篇 |
轻工业 | 6141篇 |
水利工程 | 1393篇 |
石油天然气 | 6562篇 |
武器工业 | 643篇 |
无线电 | 10044篇 |
一般工业技术 | 12009篇 |
冶金工业 | 5012篇 |
原子能技术 | 949篇 |
自动化技术 | 11829篇 |
出版年
2024年 | 390篇 |
2023年 | 1584篇 |
2022年 | 2661篇 |
2021年 | 3645篇 |
2020年 | 2775篇 |
2019年 | 2401篇 |
2018年 | 2853篇 |
2017年 | 3123篇 |
2016年 | 2619篇 |
2015年 | 3470篇 |
2014年 | 4362篇 |
2013年 | 5422篇 |
2012年 | 5603篇 |
2011年 | 6268篇 |
2010年 | 5406篇 |
2009年 | 5107篇 |
2008年 | 5051篇 |
2007年 | 4780篇 |
2006年 | 5023篇 |
2005年 | 4593篇 |
2004年 | 3029篇 |
2003年 | 2787篇 |
2002年 | 2562篇 |
2001年 | 2244篇 |
2000年 | 2375篇 |
1999年 | 2769篇 |
1998年 | 2314篇 |
1997年 | 1936篇 |
1996年 | 1838篇 |
1995年 | 1539篇 |
1994年 | 1263篇 |
1993年 | 918篇 |
1992年 | 735篇 |
1991年 | 561篇 |
1990年 | 443篇 |
1989年 | 349篇 |
1988年 | 301篇 |
1987年 | 179篇 |
1986年 | 146篇 |
1985年 | 121篇 |
1984年 | 84篇 |
1983年 | 50篇 |
1982年 | 51篇 |
1981年 | 36篇 |
1980年 | 31篇 |
1979年 | 17篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1945年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
The synthesis and characterization of Ti–xMg (x=4, 9, 12, 15, 21, 24 at%) alloys using mechanical alloying was investigated. A nanometer-sized Ti–24Mg alloy was produced. During mechanical alloying, the height of the XRD peaks of the Mg in the Ti–9Mg alloy decreased, and then disappeared, whereas the Ti XRD peaks broadened, and the grain size decreased with increasing milling time. The Mg firstly dissolved in the grain boundaries of the Ti, and then diffused into the Ti grain interiors. The grain boundaries played an important role in enhancing the solid solubility of Mg in Ti. With increasing Mg content the volume fraction of grain boundaries increased, and a decrease in grain size occurred after mechanical alloying for 48 h. 相似文献
62.
63.
64.
再生铝工业的资源主要来源于废铝,即应用领域的消费废铝和生产领域的加工废铝.随着经济全球化,废铝已进入国际市场,成为一种可流动的资源.最近几年中国大量进口废铝,已引起国际市场的高度关注.中国是废旧铝回收与再生铝生产利用大国,同时也是一个发展中国家,虽然各级政府对环境保护极为重视,但在废旧铝再生过程中仍产生了较为严重的环境污染. 相似文献
65.
本文简要阐述了北化院BCS01和上海院SLC-S两种国产气相聚乙烯浆液催化剂的性能、催化剂结构,在Unipol聚乙烯工业装置上应用结果,以及和进口同类催化剂UCAT-J的性能比较。 相似文献
66.
Fushe-Kruje水泥厂项目位于距阿尔巴尼亚首都地拉那市28公里处,是由黎巴嫩SEAMENT集团投资兴建的.是迄今阿尔巴尼亚最大的外商投资项目,设计能力为3300t/d新型干法水泥熟料生产线,是全套生产线由我公司设计、制造成套、施工、安装、调试及试生产的总承包项目。 相似文献
67.
The aluminated sepiolite, obtained by alkaline treatment with KAlO2, as well as the silver-exchanged aluminated sepiolite were tested in ethanol conversion. The reactions were performed at 280°C and with 50 Torr of ethanol in He. After the alumination through KA1O2, ethanol dehydrogenation and ethanol dehydration resulted from the Lewis acidity. The dispersion of silver led to a bifunctional catalytic system and the overall catalytic activity and the selectivity towards the acetaldehyde production increased. As a result of the Prins reaction, a significant yield in butadiene was observed. 相似文献
68.
Grace Y. Sun 《Lipids》1979,14(11):918-924
The phospholipid composition and their acyl group profiles from subcellular fractions of guinea pig adrenal gland and the
same fractions from the cortex and medulla of the bovine gland were compared. The phospholipids of guinea pig adrenal were
enriched in diacyl-glycerophosphocholines (GPC) which comprised over 50% of the total phospholipids, but the proportions of
ethanolamine and choline plasmalogens, sphingomyelin and diacyl-glycerophosphoserine (GPS) were lower in guinea pig adrenals
as compared to the bovine adrenals. In the bovine adrenal, sphingomyelin and diacyl-GPS were enriched in the medulla, whereas
diacyl-glycerophosphoinositol (GPI) were enriched in the cortex. Although lysolecithin was present (up to 4.5%) in the bovine
adrenal, only trace amounts of this lipid were detected in the guinea pig adrenal. Characteristic acyl group profiles were
found associated with each type of the phosphoglycerides in adrenal membranes. However, acyl group profiles of the phosphoglycerides
were not greatly different either between the bovine and guinea pig adrenal or with respect to the type of subcellular membranes
isolated. Diacyl-GPC were enriched in 16∶0 and 18∶1, but also contained considerable amounts of 18∶0, 18∶2 and 20∶4. Diacyl-GPE
were enriched in 18∶0, 18∶1 and 20∶4, while diacyl-GPI, diacyl-GPS, as well as alkenylacyl-GPE, were enriched in 20∶4. The
lysolecithin from bovine adrenal membranes contained mainly 16∶0, 18∶0 and 18∶1 with only trace amounts of the polyunsaturated
fatty acids. Other polyunsaturated fatty acids, such as 22∶4 and 22∶6, are apparently not prominent in the phosphoglycerides
from either the bovine or the guinea pig adrenal gland. 相似文献
69.
炭黑填充硬聚氯乙烯的改性 总被引:1,自引:0,他引:1
为使聚氯乙烯具有抗静电性能,采用加入具有导电性填料的方法,但加入大量的填料,会使硬聚氯乙烯的冲击性能降低,加工性能变差。本文是在以炭黑为填料的基础上,研究不同的改性剂和加工助剂改进硬聚氯乙烯的效果,结果表明,加入冲击改性剂和加工助剂后,大大增加了硬聚氯乙烯的冲击强度,且加工性能也得到改善,同时由于炭黑具有补强效果,其拉伸强度和弯曲强度在加入改性剂后也能满足使用要求。 相似文献
70.
Chunnuan Ji Rongjun Qu Cheng Bo Cao Huo Chen Qiang Xu Changmei Sun Chunhua Wang Huafang Yuan Jun Zhou 《应用聚合物科学杂志》2006,102(6):6054-6059
A novel chelating resin containing sulfoxide and diethylene glycol, poly{4‐vinylbenzyl‐[2‐2‐(hydroxyethyl)ethoxyl]sulfoxide} (PVESO) was synthesized using chloromethylated polystyrene (PS‐Cl) as material. Its structure was characterized by elemental analysis, infrared spectra, and scanning electron microscopy (SEM). The adsorption capacities of the resin for Hg2+, Ag+, Cu2+, Zn2+, and Pb2+ at various pH values were determined. The maximum adsorption capacities for Hg2+ and Ag+ were 1.56 and 0.75 mmol g?1 respectively. The resin had high selectivity for Hg2+ and Ag+ over the pH range 1.0–7.0. The adsorption capacities for Hg2+ and Ag+ under competitive condition were also determined by batch experiment method. In addition, the adsorption kinetics of the resin towards Hg2+ at different temperatures was also investigated. The results showed that the adsorption rate was governed by film diffusion at 20°C and 25°C, by particle diffusion at 30°C and 35°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6054–6059, 2006 相似文献