全文获取类型
收费全文 | 101246篇 |
免费 | 2640篇 |
国内免费 | 1628篇 |
专业分类
电工技术 | 2050篇 |
综合类 | 3545篇 |
化学工业 | 14200篇 |
金属工艺 | 5883篇 |
机械仪表 | 4134篇 |
建筑科学 | 3689篇 |
矿业工程 | 1088篇 |
能源动力 | 1661篇 |
轻工业 | 4839篇 |
水利工程 | 1568篇 |
石油天然气 | 1361篇 |
武器工业 | 141篇 |
无线电 | 11187篇 |
一般工业技术 | 18198篇 |
冶金工业 | 3393篇 |
原子能技术 | 594篇 |
自动化技术 | 27983篇 |
出版年
2024年 | 122篇 |
2023年 | 381篇 |
2022年 | 631篇 |
2021年 | 862篇 |
2020年 | 641篇 |
2019年 | 520篇 |
2018年 | 14936篇 |
2017年 | 13956篇 |
2016年 | 10430篇 |
2015年 | 1349篇 |
2014年 | 1131篇 |
2013年 | 1199篇 |
2012年 | 4211篇 |
2011年 | 10584篇 |
2010年 | 9305篇 |
2009年 | 6517篇 |
2008年 | 7776篇 |
2007年 | 8729篇 |
2006年 | 1135篇 |
2005年 | 2054篇 |
2004年 | 1723篇 |
2003年 | 1671篇 |
2002年 | 1051篇 |
2001年 | 572篇 |
2000年 | 697篇 |
1999年 | 547篇 |
1998年 | 395篇 |
1997年 | 326篇 |
1996年 | 355篇 |
1995年 | 248篇 |
1994年 | 203篇 |
1993年 | 135篇 |
1992年 | 128篇 |
1991年 | 118篇 |
1990年 | 53篇 |
1989年 | 57篇 |
1988年 | 45篇 |
1986年 | 34篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1963年 | 28篇 |
1960年 | 30篇 |
1959年 | 38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 15 毫秒
41.
42.
43.
44.
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
45.
46.
Keng Siau 《Requirements Engineering》2007,12(4):199-201
47.
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
48.
49.
50.
Hojjat Adeli Yaojun Ge 《International journal for numerical methods in engineering》1989,28(6):1265-1282
A dynamic programming (DP) method is presented for analysis of statically determinate and indeterminate bridges subjected to moving loads such as those specified by the American Association of State Highway and Transportation Officials (AASHTO) specifications. These loads consist of uniform lane loading, two-axle truck loading and two-axle truck plus one-axle semitrailer loading. The solution of the DP problem is based on the use of influence line diagrams and extremum functions. Recurrence formulae have been developed for various types of AASHTO live loads. The procedure presented in this article is quite general and can be applied to any type of structures with linear behaviour and any type of moving loads. Six examples are presented: a simply-supported beam, a simply-supported Pratt truss, an arch bridge, a continuous Pratt truss, a continuous frame and a cable-stayed bridge. 相似文献