全文获取类型
收费全文 | 196338篇 |
免费 | 14134篇 |
国内免费 | 10456篇 |
专业分类
电工技术 | 11719篇 |
综合类 | 15617篇 |
化学工业 | 24905篇 |
金属工艺 | 12748篇 |
机械仪表 | 11203篇 |
建筑科学 | 10325篇 |
矿业工程 | 5601篇 |
能源动力 | 4057篇 |
轻工业 | 16822篇 |
水利工程 | 4801篇 |
石油天然气 | 4239篇 |
武器工业 | 1553篇 |
无线电 | 20723篇 |
一般工业技术 | 25538篇 |
冶金工业 | 7061篇 |
原子能技术 | 2134篇 |
自动化技术 | 41882篇 |
出版年
2024年 | 735篇 |
2023年 | 1921篇 |
2022年 | 4595篇 |
2021年 | 5831篇 |
2020年 | 4094篇 |
2019年 | 2779篇 |
2018年 | 17408篇 |
2017年 | 16934篇 |
2016年 | 13167篇 |
2015年 | 5809篇 |
2014年 | 6463篇 |
2013年 | 7812篇 |
2012年 | 12479篇 |
2011年 | 19216篇 |
2010年 | 17501篇 |
2009年 | 14662篇 |
2008年 | 15983篇 |
2007年 | 16854篇 |
2006年 | 7829篇 |
2005年 | 7536篇 |
2004年 | 5677篇 |
2003年 | 4339篇 |
2002年 | 3449篇 |
2001年 | 2743篇 |
2000年 | 2312篇 |
1999年 | 770篇 |
1998年 | 293篇 |
1997年 | 189篇 |
1996年 | 145篇 |
1995年 | 110篇 |
1994年 | 76篇 |
1993年 | 89篇 |
1992年 | 77篇 |
1991年 | 76篇 |
1990年 | 50篇 |
1989年 | 59篇 |
1988年 | 43篇 |
1980年 | 36篇 |
1968年 | 43篇 |
1967年 | 34篇 |
1966年 | 43篇 |
1965年 | 45篇 |
1960年 | 30篇 |
1959年 | 66篇 |
1958年 | 38篇 |
1957年 | 36篇 |
1956年 | 35篇 |
1955年 | 63篇 |
1954年 | 68篇 |
1951年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
在铝材生产中,熔炼、铸造工序是能源与资源消耗多的工序,因此,节约资源、降低烧损与能耗有着重要意义。降低能耗还可以相应地减少温室气体与有害、有毒物质排放,对环保有利。中国当前铝合金熔炼铸造能源与资源节约的主要措施:调整加工用锭坯供应结构,大幅提高电解铝厂供应的锭坯,由2013年供应的42%提高到"十三五"末的65%-70%;加快走出去的力度,到国外去办铝厂,将在国外生产的铝合金锭坯运回来,争取2020年出口的铝材与铝制品全部以进口锭坯加工,这是最大的资源与能源节约;加强废铝回收与有效再生利用;加强创新,大力采用新装备、新技术与新工艺;加强管理,精心操作,管理中还有较大的能源与资源节约潜力。 相似文献
2.
Rectangular section control technology(RSCT)was introduced to achieve high-precision profile control during silicon steel rolling.The RSCT principle and method were designed,and the whole RSCT control strategy was developed.Specifically,RSCT included roll contour design,rolling technology optimization,and control strategy development,aiming at both hot strip mills(HSMs)and cold strip mills(CSMs).Firstly,through the high-performance variable crown(HVC)work roll optimization design in the upper-stream stands and the limited shifting technology for schedule-free rolling in the downstream stands of HSMs,a hot strip with a stable crown and limited wedge,local spot,and single wave was obtained,which was suitable for cold rolling.Secondly,an approximately rectangular section was obtained by edge varying contact(EVC)work roll contour design,edge-drop setting control,and closed loop control in the upper-stream stands of CSMs.Moreover,complex-mode flatness control was realized by coordinating multiple shape-control methods in the downstream stands of CSMs.In addition,the RSCT approach was applied in several silicon-steel production plants,where an outstanding performance and remarkable economic benefits were observed. 相似文献
3.
陕南山地烟田不同植烟年限土壤养分的变化 总被引:1,自引:0,他引:1
为给陕南山地烟草生产布局及有针对性的施肥措施提供依据,分析了陕南山地烟田不同植烟年限(0~15年)与土壤养分含量的关系。结果表明:随着植烟年限延长,有机质线性下降,全氮和速效钾显著上升,有效磷先上升后下降;氯、有效铁、有效锰、有效硼和有效铜无显著变化或变化很小,有效锌则在第1年急剧下降,之后保持稳定,10年后再次显著下降。认为陕南山地烟区烟叶生产中应适当增加有机肥的施用而合理控制氮肥、磷肥和钾肥的施用,并要注意锌肥的补充。 相似文献
4.
现阶段的语义解析方法大部分都基于组合语义,这类方法的核心就是词典。词典是词汇的集合,词汇定义了自然语言句子中词语到知识库本体中谓词的映射。语义解析一直面临着词典中词汇覆盖度不够的问题。针对此问题,该文在现有工作的基础上,提出了基于桥连接的词典学习方法,该方法能够在训练中自动引入新的词汇并加以学习,为了进一步提高新学习到的词汇的准确度,该文设计了新的词语—二元谓词的特征模板,并使用基于投票机制的核心词典获取方法。该文在两个公开数据集(WebQuestions和Free917)上进行了对比实验,实验结果表明,该文方法能够学习到新的词汇,提高词汇的覆盖度,进而提升语义解析系统的性能,特别是召回率。 相似文献
5.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
6.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献
7.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards. 相似文献
8.
9.
10.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献