全文获取类型
收费全文 | 629512篇 |
免费 | 7450篇 |
国内免费 | 2022篇 |
专业分类
电工技术 | 11583篇 |
综合类 | 656篇 |
化学工业 | 95614篇 |
金属工艺 | 25295篇 |
机械仪表 | 19822篇 |
建筑科学 | 14294篇 |
矿业工程 | 3683篇 |
能源动力 | 16928篇 |
轻工业 | 49711篇 |
水利工程 | 6754篇 |
石油天然气 | 12999篇 |
武器工业 | 44篇 |
无线电 | 73080篇 |
一般工业技术 | 126155篇 |
冶金工业 | 116625篇 |
原子能技术 | 14267篇 |
自动化技术 | 51474篇 |
出版年
2021年 | 5538篇 |
2020年 | 4291篇 |
2019年 | 5308篇 |
2018年 | 9144篇 |
2017年 | 9019篇 |
2016年 | 9761篇 |
2015年 | 6250篇 |
2014年 | 10310篇 |
2013年 | 29461篇 |
2012年 | 16504篇 |
2011年 | 22309篇 |
2010年 | 17892篇 |
2009年 | 20324篇 |
2008年 | 20832篇 |
2007年 | 20477篇 |
2006年 | 18269篇 |
2005年 | 16608篇 |
2004年 | 15637篇 |
2003年 | 15465篇 |
2002年 | 14875篇 |
2001年 | 14665篇 |
2000年 | 13864篇 |
1999年 | 14342篇 |
1998年 | 35955篇 |
1997年 | 25493篇 |
1996年 | 19687篇 |
1995年 | 14759篇 |
1994年 | 13132篇 |
1993年 | 13007篇 |
1992年 | 9592篇 |
1991年 | 9153篇 |
1990年 | 9040篇 |
1989年 | 8753篇 |
1988年 | 8491篇 |
1987年 | 7266篇 |
1986年 | 7214篇 |
1985年 | 8198篇 |
1984年 | 7630篇 |
1983年 | 6968篇 |
1982年 | 6496篇 |
1981年 | 6612篇 |
1980年 | 6218篇 |
1979年 | 6072篇 |
1978年 | 6191篇 |
1977年 | 7053篇 |
1976年 | 9095篇 |
1975年 | 5429篇 |
1974年 | 5096篇 |
1973年 | 5228篇 |
1972年 | 4432篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
A model is developed for the analysis of factors influencing organizational and technological changes associated with CAD and CAD/CAM (computer-aided design/computer-aided manufacture). Different pressures for adoption and the sociopolitical environment of the organization and related to managerial strategies and their impact on skills, tasks, training, and changes in work organization. Opportunities are illustrated through the experiences of seven British engineering companies implementing the technologies. Six of the companies are in manufacturing and one is an engineering services organization. Four of the companies are of small to medium size (under 500 employees) and the other three are large, multisite organizations. Key elements of the technological change are identified, and the position of the seven companies in relation to these elements is summarized and discussed 相似文献
912.
913.
An assessment is made of the technical contents of flight-vehicle structures curricula at 41 U.S. universities with accredited aerospace engineering programs. The assessment is based on the technical needs for the new and projected aeronautical and space systems as well as on the likely characteristics of the aerospace engineering work environment. A number of deficiencies and areas of concern are identified and recommendations are presented for enhancing the effectiveness of flight-vehicle structures education. A number of government supported programs that can help aerospace engineering education are listed in the appendix. 相似文献
914.
G. H. Palmir 《Journal of the Institute of Brewing》1987,93(4):332-333
The aleurone cells of barley, wheat, rice, rye, oats and triticale contained, comparatively, higher percentages of phosphorus than the aleurone cells of sorghum, maize or millet. The aleurone tissues of barley, wheat and rice had more phosphate than corresponding tissues of sorghum and maize. Phosphate was not detected in the aleurone tissue of maize but was found in trace amounts in the aleurone tissue of sorghum. 相似文献
915.
916.
917.
918.
Autoscan: a scan design without external scan inputs or outputs 总被引:1,自引:0,他引:1
Pomeranz I. Reddy S.M. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2005,13(9):1087-1095
We propose a design-for-testability technique for synchronous sequential circuits called autoscan. Autoscan uses scan chains similar to conventional scan. However, it gives up the external scan inputs and outputs in order to eliminate the test data volume associated with them. Scan operations under autoscan improve the circuit testability by allowing the circuit state to be modified through shifting. Due to the removal of the scan inputs and outputs, synthesis of scan chains under autoscan does not have to satisfy all the constraints imposed on conventional scan chains. We describe a synthesis procedure for autoscan chains, and demonstrate that autoscan allows us to detect almost all the faults that are detectable using conventional scan. We use random sequences in order to show that sequential test generation is not necessary under autoscan. We also describe a test generation procedure, and discuss the effect of autoscan on fault diagnosis. 相似文献
919.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method. 相似文献
920.
As feature size of electronic devices decreases, fast and accurate capacitance extraction has become increasingly critical for verification and analysis as regard as electromagnetic compatibility and signal integrity issues. The partial element equivalent circuit method is implemented for three-dimensional capacitance extraction of interconnects and very large-scale integration circuits with multiple dielectrics. The electric field coupling due to free and bound charges are analysed and modelled separately thus allowing to distinguish their contribution. The proposed approach provides physical insight, totally compatible fast methods for accelerating matrix-vector products, allows an easy treatment of lossy and dispersive dielectrics and is well suited for applying model order reduction techniques 相似文献