全文获取类型
收费全文 | 45848篇 |
免费 | 5534篇 |
国内免费 | 1344篇 |
专业分类
电工技术 | 3713篇 |
技术理论 | 2篇 |
综合类 | 3315篇 |
化学工业 | 9826篇 |
金属工艺 | 434篇 |
机械仪表 | 922篇 |
建筑科学 | 3311篇 |
矿业工程 | 15970篇 |
能源动力 | 3979篇 |
轻工业 | 877篇 |
水利工程 | 614篇 |
石油天然气 | 1418篇 |
武器工业 | 55篇 |
无线电 | 1052篇 |
一般工业技术 | 1107篇 |
冶金工业 | 3209篇 |
原子能技术 | 52篇 |
自动化技术 | 2870篇 |
出版年
2024年 | 72篇 |
2023年 | 317篇 |
2022年 | 1049篇 |
2021年 | 1537篇 |
2020年 | 1667篇 |
2019年 | 975篇 |
2018年 | 1044篇 |
2017年 | 1034篇 |
2016年 | 1494篇 |
2015年 | 1722篇 |
2014年 | 3465篇 |
2013年 | 3006篇 |
2012年 | 4773篇 |
2011年 | 4142篇 |
2010年 | 3026篇 |
2009年 | 2974篇 |
2008年 | 2647篇 |
2007年 | 2924篇 |
2006年 | 2392篇 |
2005年 | 2085篇 |
2004年 | 1644篇 |
2003年 | 1514篇 |
2002年 | 1177篇 |
2001年 | 1137篇 |
2000年 | 943篇 |
1999年 | 713篇 |
1998年 | 510篇 |
1997年 | 465篇 |
1996年 | 382篇 |
1995年 | 330篇 |
1994年 | 238篇 |
1993年 | 149篇 |
1992年 | 142篇 |
1991年 | 79篇 |
1990年 | 48篇 |
1989年 | 35篇 |
1988年 | 46篇 |
1987年 | 36篇 |
1986年 | 25篇 |
1985年 | 188篇 |
1984年 | 231篇 |
1983年 | 173篇 |
1982年 | 154篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1974年 | 1篇 |
1967年 | 1篇 |
1962年 | 1篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
51.
Two lignite samples, Beulah No. 3 and Big Brown No. 1, were liquefied at 420 °C using H2 and synthesis gas to determine the optimum beneficial amount of H2S in the batch autoclave reactor. Under the conditions employed, 50–100 psi partial pressure of H2S, nominally 4–10 wt% of daf lignite, was optimum for both samples. Synthesis gas outperformed H2 with and without H2S for the liquefaction of the two coals. 相似文献
52.
Erv J. Kuhlmann Dick Y. Jung Richard P. Guptill Charles A. Dyke Hyung K. Zang 《Fuel》1985,64(11):1552-1557
The presence of hydroaromatic, hydrogen donor components in a coal-derived solvent is one of the more important factors in the successful operation of a non-catalytic coal liquefaction process. Various hydrogen donor species present in a hydrogenated creosote oil have been identified. Their rate of disappearance under conditions that are consistent with a short residence time coal liquefaction process has been used to rank the reactivities of the various hydrogen donors. 1,2,3,10b-Tetrahydrofluoranthene was found to be an exceptional donor while 4,5-dihydropyrene, the hexahydropyrenes and 9,10-dihydrophenanthrene were found to be quite active. Sym.-octahydrophenanthrene and 2a,3,4,5-tetrahydroacenaphthene exhibited moderate activity. Tetralin and the four methyltetralin isomers were found to be unreactive under the coal liquefaction conditions employed. 相似文献
53.
Results for various types of polar compounds in SRC-11 coal-derived liquids and other fuels were obtained by one or more of the three analytical methods: non-aqueous titration, i.r. spectroscopy and h.p.l.c. Practical aspects as well as precision, accuracy and assumptions necessary for effective application of each of the methods are discussed. H.p.l.c. is applicable to the widest variety of compound types, is the most rapid, most sensitive and shows the best promise for increased development and improvement. Application and development of these techniques is a logical step toward improving process monitoring, catalyst development, toxicological screening and general fuel analysis. 相似文献
54.
The new structure of fibre glass reinforced plastics bolt 总被引:4,自引:0,他引:4
The develop actuality and direction of FRP (fibre glass reinforced plastics) bolt in the world are analyzed. The new type structure of FRP bolt was designed. Trial data indicate that, all kinds of capability target of this FRP bolt all achieve and exceed the country stand-ard, substitute present metal bolt, wood bolt and bamboo bolt and other side bolt, it can gain magnitude technology and economy benefit. FRP bolt mechanization product line produce ef-ficiency is high, its throughput a day are 750 base, this can meet demand of hit-small mining company. 相似文献
55.
56.
The influence of raw material characteristics on the industrial pelletizing process and pellet quality 总被引:1,自引:0,他引:1
Mehrdad Arshadi Rolf Gref Paul Geladi Sten-Axel Dahlqvist Torbjörn Lestander 《Fuel Processing Technology》2008
Industrial pelletizing of sawdust was carried out as a designed experiment in the factors: sawdust moisture content, fractions of fresh pine, stored pine and spruce. The process parameters and response variables were energy consumption, pellet flow rate, pellet bulk density, durability and moisture content. The final data consisted of twelve industrial scale runs. Because of the many response variables, data evaluation was by principal component analysis of a 12 × 9 data matrix. The two principal component model showed a clustering of samples, with a good reproducibility of the center points. It also showed a positive correlation of energy consumption, bulk density and durability all negatively correlated to flow rate and moisture content. The stored pine was more related to high durability and bulk density. The role of the spruce fraction was unclear. The design matrix, augmented with the process parameters was a 12 × 6 matrix. Partial least squares regression showed excellent results for pellet moisture content and bulk density. The model for durability was promising. A 12 × 21 data matrix of fatty- and resin acid concentrations measured by GC–MS showed the differences between fresh and stored pine very clearly. The influence of the spruce fraction was less clear. However, the influence of the fatty- and resin acids on the pelletizing process could not be confirmed, indicating that other differences between fresh and stored pine sawdust have to be investigated. This work shows that it is possible to design the pelletizing process for moderate energy consumption and high pellet quality. 相似文献
57.
新型煤填充高分子复合材料的研制与应用 总被引:4,自引:0,他引:4
根据煤的结构特点,对煤进行闭环的超细粉碎,脱除部分挥发分,表面傅-克烷基化化学改性,与塑料经强制排气式共混,研制了一种新型的煤填充高分子复合塑料母料.将该母料用于聚丙烯,可制得具有较好强度、韧性和优良电绝缘性能的复合材料,在煤含量为20%(质量分数)时,复合材料的拉伸屈服强度大于24.0MPa,缺口冲击强度不小于8.0 kJ/m2;同时,煤/聚丙烯复合材料在较大的煤含量范围内(0%~50%,质量分数),直流绝缘电阻率保持在1014 Ω·cm以上.新型煤填充高分子复合材料在电线电缆中的应用表明,加工性能良好,成品绝缘层力学性能满足标准要求,绝缘性能优良,并可有效降低材料的成本. 相似文献
58.
59.
煤巷锚杆支护技术的探讨 总被引:1,自引:0,他引:1
从巷道围岩强度,原岩自重应力,地质构适应力,煤柱留设宽度和巷道断面形状等方面对影响煤巷稳定性的因素进行了分析,提出了煤巷锚杆支护注意的6个问题。 相似文献
60.