全文获取类型
收费全文 | 86037篇 |
免费 | 1064篇 |
国内免费 | 411篇 |
专业分类
电工技术 | 818篇 |
综合类 | 2323篇 |
化学工业 | 12029篇 |
金属工艺 | 4818篇 |
机械仪表 | 3057篇 |
建筑科学 | 2343篇 |
矿业工程 | 568篇 |
能源动力 | 1168篇 |
轻工业 | 3804篇 |
水利工程 | 1291篇 |
石油天然气 | 348篇 |
无线电 | 9440篇 |
一般工业技术 | 16658篇 |
冶金工业 | 2924篇 |
原子能技术 | 278篇 |
自动化技术 | 25645篇 |
出版年
2023年 | 30篇 |
2022年 | 38篇 |
2021年 | 50篇 |
2020年 | 39篇 |
2019年 | 51篇 |
2018年 | 14488篇 |
2017年 | 13419篇 |
2016年 | 10011篇 |
2015年 | 668篇 |
2014年 | 308篇 |
2013年 | 305篇 |
2012年 | 3233篇 |
2011年 | 9534篇 |
2010年 | 8365篇 |
2009年 | 5628篇 |
2008年 | 6883篇 |
2007年 | 7870篇 |
2006年 | 199篇 |
2005年 | 1293篇 |
2004年 | 1187篇 |
2003年 | 1246篇 |
2002年 | 595篇 |
2001年 | 137篇 |
2000年 | 220篇 |
1999年 | 102篇 |
1998年 | 144篇 |
1997年 | 100篇 |
1996年 | 99篇 |
1995年 | 63篇 |
1994年 | 54篇 |
1993年 | 50篇 |
1992年 | 34篇 |
1991年 | 46篇 |
1988年 | 28篇 |
1986年 | 26篇 |
1985年 | 31篇 |
1984年 | 28篇 |
1969年 | 32篇 |
1968年 | 47篇 |
1967年 | 38篇 |
1966年 | 47篇 |
1965年 | 50篇 |
1963年 | 33篇 |
1960年 | 30篇 |
1959年 | 36篇 |
1958年 | 38篇 |
1957年 | 36篇 |
1956年 | 36篇 |
1955年 | 63篇 |
1954年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
In this paper, we argue that successful integration of knowledge across work domains in the short-term can mask the generation of long-term consequences. We explore a setting, the introduction of environmental considerations into semiconductor manufacturing, where the eventual adoption of common measurement artifacts and associated practices enabled knowledge integration, but failed to address significant underlying consequences. Drawing from observational, interview, and archival data we develop an understanding of the work practices of the Tech and EnviroTech groups as structured by the material world and broader collective conventions. We introduce the concept of knowledge regime to outline the differences in knowledge across these work domains. More specifically, we find that differences in the causal specificity and developmental time horizon of knowledge and the measurement artifacts that result contribute to the relative power of one knowledge regime over another. Understanding these sources of incompatibility provides insight into the design requirements of information systems as boundary objects for knowledge integration, but also specifies the potential limits to any design effort. 相似文献
85.
86.
87.
88.
Understanding consumer behaviour is of vital importance to consumer-oriented e-business models today. In this paper, we study the relationships between consumer perceptions of risk and trust and the attitude towards purchasing at a consumer-to-consumer electronic marketplace (EM). Typical for EM settings is that consumer behaviour is subject to perceptions of the selling party as well as of the institutional structures of the intermediary that is operating the EM. Building upon the well-established literature of trust, we consider the concepts of intermediary trust and seller trust. We extend this categorisation by introducing the concepts of intermediary risk and seller risk. We developed measurement instruments for intermediary risk and seller risk. All measurement scales have acceptable alphas and are unidimensional. An empirical study is conducted to explore the relationships between the risk and trust types and consumer purchase attitude. The results reveal significant, direct effects of seller trust and seller risk. Second-order effects of intermediary trust and intermediary risk are investigated and reported. The paper concludes with general observations and recommendations for research and practice. 相似文献
89.
90.
Shiqi He Qianchu Liu Yiu-Wing Mai Roland Bryant 《Journal of materials science. Materials in medicine》1996,7(10):611-616
Abrasive wear is a major problem in the application of dental composite resins. In this study the friction and wear behaviours of two types of dental composites: one containing relatively coarse filler particles and some microfillers (Estilux) and another containing only microfiller particles (Durafill), have been investigated by using a scratch testing machine. Experimental results show that the coefficients of friction in both composites are essentially constant for applied loads up to 20 N. The wear resistance of Durafill is better than Estilux. Under the same testing conditions, the size, shape and distribution of the filler particles are more important variables than applied load and sliding speed in controlling the wear mechanism. It is shown that for Estilux, plastic ploughing by the diamond indenter is the predominant mechanism. For Durafill, however, the formation and propagation of tensile cracks on the worn surface is the main wear mechanism. The effects of two different indenters, diamond and enamel, on the basic wear mechanisms are also discussed. 相似文献