全文获取类型
收费全文 | 22950篇 |
免费 | 4937篇 |
国内免费 | 3444篇 |
专业分类
电工技术 | 1572篇 |
综合类 | 2593篇 |
化学工业 | 1017篇 |
金属工艺 | 697篇 |
机械仪表 | 2073篇 |
建筑科学 | 1098篇 |
矿业工程 | 484篇 |
能源动力 | 270篇 |
轻工业 | 3165篇 |
水利工程 | 271篇 |
石油天然气 | 988篇 |
武器工业 | 239篇 |
无线电 | 3000篇 |
一般工业技术 | 1568篇 |
冶金工业 | 535篇 |
原子能技术 | 129篇 |
自动化技术 | 11632篇 |
出版年
2024年 | 344篇 |
2023年 | 753篇 |
2022年 | 1449篇 |
2021年 | 1401篇 |
2020年 | 1445篇 |
2019年 | 1143篇 |
2018年 | 999篇 |
2017年 | 1070篇 |
2016年 | 1161篇 |
2015年 | 1246篇 |
2014年 | 1554篇 |
2013年 | 1471篇 |
2012年 | 1980篇 |
2011年 | 1968篇 |
2010年 | 1527篇 |
2009年 | 1437篇 |
2008年 | 1428篇 |
2007年 | 1546篇 |
2006年 | 1305篇 |
2005年 | 1119篇 |
2004年 | 902篇 |
2003年 | 789篇 |
2002年 | 649篇 |
2001年 | 514篇 |
2000年 | 448篇 |
1999年 | 364篇 |
1998年 | 283篇 |
1997年 | 220篇 |
1996年 | 172篇 |
1995年 | 126篇 |
1994年 | 104篇 |
1993年 | 73篇 |
1992年 | 60篇 |
1991年 | 41篇 |
1990年 | 47篇 |
1989年 | 40篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 21篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
通过对电、汽两用节能加热锅炉的描述,指出该设备具有投资少,无污染,能源转化率高,起停速度快,负荷调节范围大,结构简单,安全性能好并可充分利用电能等特点. 相似文献
32.
通过介绍特细砂混凝土在嘉陵江流域的马回、东西关、桐子壕等水电站建设中的应用情况 ,分析了特细砂混凝土的特性和配合比等特点 ,并闸明了在施工中使用特细砂混凝土的经济效益。 相似文献
33.
34.
35.
毛家河水电站库区岩溶发育特征及邻谷渗漏分析 总被引:1,自引:0,他引:1
毛家河水电站位于碳酸盐岩地区,库首距左岸邻谷可渡河14—23km、距右岸邻谷北盘江干流14.8km,水库两岸大型落水洞、溶洞及地下岩溶管道相对较为发育。为初步判断水库存在邻谷渗漏的可能性,对水库两岸可溶岩地层岩溶发育形态、特征及规律进行了勘察,并根据现场地质调查资料对3条可疑渗漏带进行了分析论证。 相似文献
36.
The main difficulty with EM algorithm for mixture model concerns the number of components, say g. This is the question of model selection, and the EM algorithm itself could not estimate g. On the contrary, the algorithm requires g to be specified before the remaining parameters can be estimated. To solve this problem, a new algorithm, which is called stepwise split-and-merge EM (SSMEM) algorithm, is proposed. The SSMEM algorithm alternately splits and merges components, estimating g and other parameters of components simultaneously. Also, two novel criteria are introduced to efficiently select the components for split or merge. Experimental results on simulated and real data demonstrate the effectivity of the proposed algorithm. 相似文献
37.
This paper reports the results of current fundamental research at the Department of Process Engineering, University of Miskolc on the processing of clean coal from Mecsek bituminous coal, Southern Hungary. The theoretical possibility of the separation of different petrographic components was proven experimentally and their liberation degree was determined based on the petrographic composition, flotation kinetic study of isolated components (groups of components), scanning electron microscopy and microprobe analyses. The mill with stirred ball media was chosen for the ultra-fine liberation of the coal components. It was revealed that along with the liberation of coal components, their surface oxidation and spontaneous agglomeration, entrapping the mineral impurities take place in ultra-fine grinding. This paper discusses the interfacial phenomena occurring in the ultra-fine grinding process and their influence on the flotation. The concept for the advanced preparation of clean coal was developed, tested and proved. The main steps of this concept are the ultra-fine liberation in the stirred-media mill, the de-agglomeration of flocs spontaneously formed during the ultra-fine grinding and the induced (hydrophobic) flocculation with the following two-step flotation in a flotation column. 相似文献
38.
Depression is a widespread disorder with devastating individual and societal consequences. Although a great deal of research and theory has focused on treatment of acute episodes, progress needs to be made in preventing the emergence of first episodes of the disorder. There has been considerable advancement in understanding psychological vulnerability factors associated with this mood disorder, especially on the basis of cognitive behavioural models and research findings based on this theoretical model. In this paper we review the concept of cognitive vulnerability, with a particular focus on what this body of research work suggests clinically for the prevention of depression. We outline, based on this science, what the effective ingredients of a prevention program could be. We also discuss some of the pragmatic aspects of developing an effective prevention program for depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
聚乙烯丙纶复合防水卷材的特点及其应用 总被引:2,自引:0,他引:2
介绍了聚乙烯丙纶复合防水卷材的产品结构特点和性能特点、防水系统结构特点和配套材料、应用拼接技术以及产品应用范围。 相似文献
40.
Christos Bouras Agisilaos Konidaris 《International Journal of Communication Systems》2005,18(2):119-142
Redundant data transfers over the Web, can be mainly attributed to the repeated transfers of unchanged data. Web caches and Web proxies are some of the solutions that have been proposed, to deal with the issue of redundant data transfers. In this paper we focus on the efficient estimation and reduction of redundant data transfers over the Web. We first prove that a vast amount of redundant data is transferred in Web pages that are considered to carry fresh data. We show this by following an approach based on Web page fragmentation and manipulation. Web pages are broken down to fragments, based on specific criteria. We then deal with these fragments as independent constructors of the Web page and study their change patterns independently and in the context of the whole Web page. After the fragmentation process, we propose solutions for dealing with redundant data transfers. This paper has been based on our previous work on ‘Web Components’ but also on related work by other researchers. It utilises a proxy based, client/server architecture, and imposes changes to the algorithms executed on the Proxy server and on clients. We show that our proposed solution can considerably reduce the amount of redundant data transferred on the Web. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献