全文获取类型
收费全文 | 900182篇 |
免费 | 136879篇 |
国内免费 | 98558篇 |
专业分类
电工技术 | 88365篇 |
技术理论 | 1篇 |
综合类 | 101258篇 |
化学工业 | 109655篇 |
金属工艺 | 73557篇 |
机械仪表 | 59194篇 |
建筑科学 | 66898篇 |
矿业工程 | 44271篇 |
能源动力 | 25279篇 |
轻工业 | 97567篇 |
水利工程 | 31854篇 |
石油天然气 | 37470篇 |
武器工业 | 13646篇 |
无线电 | 100591篇 |
一般工业技术 | 83256篇 |
冶金工业 | 37792篇 |
原子能技术 | 13161篇 |
自动化技术 | 151804篇 |
出版年
2024年 | 6754篇 |
2023年 | 15463篇 |
2022年 | 32862篇 |
2021年 | 41542篇 |
2020年 | 33218篇 |
2019年 | 30544篇 |
2018年 | 32632篇 |
2017年 | 37809篇 |
2016年 | 35211篇 |
2015年 | 47397篇 |
2014年 | 55778篇 |
2013年 | 62903篇 |
2012年 | 75758篇 |
2011年 | 76380篇 |
2010年 | 72459篇 |
2009年 | 67853篇 |
2008年 | 68216篇 |
2007年 | 66374篇 |
2006年 | 56638篇 |
2005年 | 46506篇 |
2004年 | 36880篇 |
2003年 | 25207篇 |
2002年 | 23691篇 |
2001年 | 21335篇 |
2000年 | 17655篇 |
1999年 | 9193篇 |
1998年 | 5271篇 |
1997年 | 4545篇 |
1996年 | 4231篇 |
1995年 | 4127篇 |
1994年 | 3352篇 |
1993年 | 3117篇 |
1992年 | 2911篇 |
1991年 | 2172篇 |
1990年 | 1754篇 |
1989年 | 1655篇 |
1988年 | 1215篇 |
1987年 | 461篇 |
1986年 | 407篇 |
1985年 | 291篇 |
1984年 | 208篇 |
1983年 | 184篇 |
1982年 | 220篇 |
1981年 | 282篇 |
1980年 | 298篇 |
1979年 | 188篇 |
1976年 | 301篇 |
1975年 | 203篇 |
1972年 | 236篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management. 相似文献
22.
Timothy Thomasma Kurt Hilbrecht 《International Journal of Flexible Manufacturing Systems》1991,3(3-4):231-250
Good methods are needed to specify, test, and debug material-handling control logic. This article surveys a number of representative methods for defining and describing control algorithms for programmable material-handling equipment used in flexible manufacturing systems. The methods are evaluated with regard to their suitability for communication between people and as bases for interfaces to automatic program generators. It is concluded that no single method is entirely satisfactory. Three methods (position diagrams, function block diagrams, and operation networks) have potential to be combined into an effective hybrid approach that minimizes the need for the user to switch between various conceptual models. 相似文献
23.
The bonding of β'-Al2O3 and pyrex glass to Al matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope (SEM), energy dispersive X-ray fluorescence spectrometer (EDX). It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding. 相似文献
24.
25.
超低密度硬胶极压型油包水乳化钻井液在广安002-H9井的应用 总被引:2,自引:1,他引:1
在超低密度钻井液的使用方面,传统的油基钻井液和油包水钻井液存在易着火、安全性差的问题,而最近使用的美国3M公司的中空玻璃微珠聚磺钻井液又存在固控困难、钻井液费用很高等难题。为此,从选择合适的润湿反转剂和阻燃剂入手,在室内对获得的超低密度硬胶极压型油包水乳化钻井液成果配方进行了全面评价,并应用在广安002 H9井水平段欠平衡钻井中取得了良好效果。室内研究与现场应用表明,超低密度硬胶极压型油包水乳化钻井液能够很好地满足广安构造水平井段欠平衡钻井的需要。该钻井液体系具有防塌、润滑、携砂能力强,密度容易控制,钻井液单位成本合理并可重复使用,安全性好等显著特点,适合在类似广安构造的水平井段中推广应用。 相似文献
26.
27.
29.
30.
This paper examines Total Quality Management (TQM) as defined by Dr. W. Edwards Deming including Deming's fourteen points and explains how the United States' Department of Defense (DOD) defines TQM and why TQM is necessary. It also covers how the DOD is planning on implementing TQM and the policy that has been established as guidance in the implementation process. 相似文献