全文获取类型
收费全文 | 50675篇 |
免费 | 7076篇 |
国内免费 | 2720篇 |
专业分类
电工技术 | 2750篇 |
技术理论 | 4篇 |
综合类 | 3837篇 |
化学工业 | 8286篇 |
金属工艺 | 316篇 |
机械仪表 | 798篇 |
建筑科学 | 2309篇 |
矿业工程 | 22763篇 |
能源动力 | 2683篇 |
轻工业 | 212篇 |
水利工程 | 357篇 |
石油天然气 | 913篇 |
武器工业 | 48篇 |
无线电 | 1094篇 |
一般工业技术 | 928篇 |
冶金工业 | 3291篇 |
原子能技术 | 58篇 |
自动化技术 | 9824篇 |
出版年
2024年 | 103篇 |
2023年 | 357篇 |
2022年 | 1140篇 |
2021年 | 1740篇 |
2020年 | 2060篇 |
2019年 | 1218篇 |
2018年 | 1311篇 |
2017年 | 1274篇 |
2016年 | 1633篇 |
2015年 | 1876篇 |
2014年 | 3611篇 |
2013年 | 3130篇 |
2012年 | 5026篇 |
2011年 | 4365篇 |
2010年 | 3258篇 |
2009年 | 3384篇 |
2008年 | 3306篇 |
2007年 | 3612篇 |
2006年 | 3116篇 |
2005年 | 2671篇 |
2004年 | 2175篇 |
2003年 | 2061篇 |
2002年 | 1458篇 |
2001年 | 1267篇 |
2000年 | 1058篇 |
1999年 | 781篇 |
1998年 | 572篇 |
1997年 | 482篇 |
1996年 | 407篇 |
1995年 | 351篇 |
1994年 | 280篇 |
1993年 | 174篇 |
1992年 | 152篇 |
1991年 | 101篇 |
1990年 | 53篇 |
1989年 | 40篇 |
1988年 | 55篇 |
1987年 | 44篇 |
1986年 | 26篇 |
1985年 | 188篇 |
1984年 | 224篇 |
1983年 | 170篇 |
1982年 | 145篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
简述了我国钨矿业概况、现有采选技术水平及钨矿加工利用率 ;从资源配置出发 ,阐述了钨矿业发展存在的几个主要问题 ,并且针对性地提出了可持续发展的几点建议。 相似文献
56.
57.
Investigations of water inrushes from aquifers under coal seams 总被引:6,自引:0,他引:6
In many coal mines, limestone-confined aquifers underlie coal seams. During coal extraction from these mines, water inrushes occur frequently with disastrous consequences. This paper introduces the hydrogeological conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams. It then presents the water inrush mechanism. The main factors which control water inrushes include strata pressure, mining size, geologic structures and the water pressure in the underlying aquifer. Analysis shows that reduction of confinement due to mining is the major cause of the water-conducting failure in the floor strata. The depth of the failure zone is strongly dependent on the mining width. This paper also presents field observation results of the water-conducting failure in the floor strata, and applies the finite element method coupled with stress-dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction. Finally, theoretical and empirical methods to predict water inrushes are given, and technical measures for improving mine design and safety for coal extraction over aquifers are presented. These measures include fault and fracture grouting and mining method modification such as changing long-wall to short-wall mining. 相似文献
58.
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
59.
Using Web resources to construct multilingual medical thesaurus for cross-language medical information retrieval 总被引:1,自引:0,他引:1
Due to the language barrier, non-English users are unable to retrieve the most updated medical information from the U.S. authoritative medical websites, such as PubMed and MedlinePlus. However, currently, there is no any cross-language medical information retrieval (CLMIR) system that can help Chinese-speaking consumers cross the language barrier in finding useful English medical information. A few CLMIR systems utilize MeSH (Medical Subject Headings) to help overcome the language barrier. Unfortunately, the traditional Chinese version of MeSH is currently unavailable.In this paper, we employ a semi-automatic term translation method to construct a Chinese–English MeSH by exploiting abundant multilingual Web resources, including Web anchor texts and search–result pages. Through this method, we have developed a Chinese–English Mesh Compilation System to assist knowledge engineers in compiling a Chinese–English medical thesaurus with more than 19,000 entries. Furthermore, this thesaurus has been used to develop a prototypical system for cross-language medical information retrieval, MMODE, which can help consumers retrieve top-quality English medical information using Chinese terms. 相似文献
60.