全文获取类型
收费全文 | 84046篇 |
免费 | 967篇 |
国内免费 | 408篇 |
专业分类
电工技术 | 788篇 |
综合类 | 2317篇 |
化学工业 | 11555篇 |
金属工艺 | 4788篇 |
机械仪表 | 3031篇 |
建筑科学 | 2158篇 |
矿业工程 | 562篇 |
能源动力 | 1118篇 |
轻工业 | 3623篇 |
水利工程 | 1266篇 |
石油天然气 | 341篇 |
无线电 | 9264篇 |
一般工业技术 | 16364篇 |
冶金工业 | 2628篇 |
原子能技术 | 283篇 |
自动化技术 | 25335篇 |
出版年
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2018年 | 14470篇 |
2017年 | 13382篇 |
2016年 | 9961篇 |
2015年 | 606篇 |
2014年 | 242篇 |
2013年 | 213篇 |
2012年 | 3148篇 |
2011年 | 9408篇 |
2010年 | 8286篇 |
2009年 | 5553篇 |
2008年 | 6782篇 |
2007年 | 7784篇 |
2006年 | 125篇 |
2005年 | 1226篇 |
2004年 | 1140篇 |
2003年 | 1195篇 |
2002年 | 556篇 |
2001年 | 107篇 |
2000年 | 186篇 |
1999年 | 67篇 |
1998年 | 59篇 |
1997年 | 38篇 |
1996年 | 58篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 18篇 |
1992年 | 20篇 |
1991年 | 26篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1986年 | 7篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
This paper reports the findings of a detailed study of Web-based systems design (WBSD) practices in Ireland based on data
collected over a 3-year period (2002–2005), the objectives of which were to (1) contribute towards a richer understanding
of the current “real-world” context of WBSD by characterising the profile of a typical project (team size, timeframe, nature
of requirements, etc.) and identifying the key challenges, constraints, and imperatives (i.e. “mediating factors”) faced by
Web-based system designers, and (2) understand how those contextual parameters and mediating factors influence the activity
of WBSD as regards the selection and enactment of whatever design practices are therefore engaged (i.e. the use of methods,
procedures, etc.). Data was gathered through a survey which yielded 165 usable responses, and later through a series of semi-structured
qualitative interviews. Using grounded theory, an explanatory conceptual framework is derived, based on an extension of the
“method-in-action” model, the application of which to WBSD has not been previously investigated in depth. It is proposed that
this framework of WBSD issues is valuable in a number of ways to educators, researchers, practitioners, and method engineers. 相似文献
44.
45.
Keng Siau 《Requirements Engineering》2007,12(4):199-201
46.
Phase-change read-and-write memory (PRAM) is a promising memory that can solve the problems of conventional memory—scalability, read/write speed, and reliability. We will review the opportunities and technical challenges of PRAM. The most important challenge of PRAM is the reduction of the writing current. Various approaches to reduce the writing current will be reviewed and the prospects of PRAM are discussed. 相似文献
47.
Tohru Morii Hiroyuki Hamada Muriel Desaeger Akihiko Gotoh Atsushi Yokoyama Ignaas Verpoest Zen-ichiro Maekawa 《Composite Structures》1995,32(1-4):133-139
This study deals with the impact property and damage tolerance of matrix hybrid composite laminates with different laminate constitution. The matrix hybrid composite laminates consisted of the laminae with a conventional epoxy resin and the laminae with a flexible epoxy resin modified from the conventional resin to avoid the interlaminar delamination. The impact energy absorption ratio greatly depended on the matrix resin placed at the impact face. The energy absorption was almost constant if the conventional resin was placed at the impact surface layer, while it increased exponentially with the increasing fraction of the flexible resin if the flexible resin was placed at the impact face. The impact energy was absorbed by the damage development and propagation in the laminate with conventional resin laminae as the impacted face, while it was absorbed by both the recoverable deformation of the flexible resin and the damage propagation in the laminate with flexible resin laminae as the impacted face. 相似文献
48.
49.
50.
Frantz Rowe 《欧洲信息系统杂志》2006,15(3):244-248