全文获取类型
收费全文 | 84716篇 |
免费 | 966篇 |
国内免费 | 415篇 |
专业分类
电工技术 | 822篇 |
综合类 | 2316篇 |
化学工业 | 11577篇 |
金属工艺 | 4822篇 |
机械仪表 | 3027篇 |
建筑科学 | 2159篇 |
矿业工程 | 562篇 |
能源动力 | 1140篇 |
轻工业 | 3650篇 |
水利工程 | 1269篇 |
石油天然气 | 341篇 |
无线电 | 9363篇 |
一般工业技术 | 16524篇 |
冶金工业 | 2920篇 |
原子能技术 | 274篇 |
自动化技术 | 25331篇 |
出版年
2022年 | 14篇 |
2021年 | 25篇 |
2020年 | 17篇 |
2019年 | 16篇 |
2018年 | 14454篇 |
2017年 | 13388篇 |
2016年 | 9982篇 |
2015年 | 610篇 |
2014年 | 253篇 |
2013年 | 249篇 |
2012年 | 3162篇 |
2011年 | 9432篇 |
2010年 | 8297篇 |
2009年 | 5582篇 |
2008年 | 6812篇 |
2007年 | 7809篇 |
2006年 | 149篇 |
2005年 | 1241篇 |
2004年 | 1154篇 |
2003年 | 1196篇 |
2002年 | 556篇 |
2001年 | 112篇 |
2000年 | 206篇 |
1999年 | 85篇 |
1998年 | 170篇 |
1997年 | 97篇 |
1996年 | 100篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 41篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1988年 | 18篇 |
1984年 | 17篇 |
1976年 | 15篇 |
1969年 | 25篇 |
1968年 | 44篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 45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 15 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.
48.
Shuzo Ueda Ryoichi Kurihara Noriyuki Miyazaki Toshikuni Isozaki 《International Journal of Pressure Vessels and Piping》1985,18(3):161-176
The purpose of pipe rupture studies in JAERI is to perform model tests on pipe whip, restraint behavior, jet impingement and jet thrust force, and to establish a computational method for analyzing these phenomena. This report presents the analytical results of 4-inch pipe whip tests under BWR LOCA conditions.Dynamic response analyses were performed using the general-purpose finite element program ADINA. The test pipe was modelled by straight beam elements and the four restraints were modelled by a single truss element. The analytical results were compared with the experimental results. Impact time and maximum total restraint force showed good agreement with experimental results. On the other hand, pipe strain and pipe deflection could not be predicted so well. The reason for this is that the sliding of the restraint during the pipe whip movement cannot be considered in the analyses. 相似文献
49.
50.
Frantz Rowe 《欧洲信息系统杂志》2006,15(3):244-248