全文获取类型
收费全文 | 11288篇 |
免费 | 658篇 |
国内免费 | 934篇 |
专业分类
电工技术 | 283篇 |
综合类 | 599篇 |
化学工业 | 202篇 |
金属工艺 | 289篇 |
机械仪表 | 651篇 |
建筑科学 | 363篇 |
矿业工程 | 145篇 |
能源动力 | 95篇 |
轻工业 | 54篇 |
水利工程 | 50篇 |
石油天然气 | 111篇 |
武器工业 | 61篇 |
无线电 | 1394篇 |
一般工业技术 | 351篇 |
冶金工业 | 147篇 |
原子能技术 | 63篇 |
自动化技术 | 8022篇 |
出版年
2024年 | 4篇 |
2023年 | 35篇 |
2022年 | 80篇 |
2021年 | 113篇 |
2020年 | 120篇 |
2019年 | 84篇 |
2018年 | 132篇 |
2017年 | 186篇 |
2016年 | 216篇 |
2015年 | 312篇 |
2014年 | 582篇 |
2013年 | 476篇 |
2012年 | 696篇 |
2011年 | 904篇 |
2010年 | 713篇 |
2009年 | 688篇 |
2008年 | 819篇 |
2007年 | 919篇 |
2006年 | 893篇 |
2005年 | 873篇 |
2004年 | 662篇 |
2003年 | 704篇 |
2002年 | 500篇 |
2001年 | 367篇 |
2000年 | 368篇 |
1999年 | 293篇 |
1998年 | 208篇 |
1997年 | 157篇 |
1996年 | 154篇 |
1995年 | 113篇 |
1994年 | 84篇 |
1993年 | 73篇 |
1992年 | 61篇 |
1991年 | 42篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 15篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Because of the widespread increasing application of Web services and autonomic computing, self-adaptive software is an area gaining increasing importance. Control theory provides a theoretical foundation for self-adaptive software. In this paper, we propose the use of the supervisory control theory of discrete event dynamic systems (DEDS) to provide a rigorous foundation for designing software for reactive systems. This paper focuses in particular on design of software with an attractivity requirement. It studies this problem using the polynomial dynamic system (PDS) model of DEDS. A necessary and sufficient condition for software existence and two algorithms for such software design are presented. 相似文献
62.
63.
Michael Khl Gary Jorgensen Stefan Brunold Bo Carlsson Markus Heck Kenneth Mller 《Solar Energy》2005,79(6):618-623
The economic viability of solar collector systems for domestic hot water (DHW) generation is strongly linked to the cost of such systems. Installation and hardware costs must be reduced by 50% to allow significant market penetration. An attractive approach to cost reduction is to replace glass and metal parts with less expensive, lighter weight polymeric components. Weight reduction decreases the cost of shipping, handling, and installation. The use of polymeric materials also allows the benefits and cost savings associated with well established manufacturing processes, along with savings associated with improved fastening, reduced part count, and overall assembly refinements. A key challenge is to maintain adequate system performance and assure requisite durability for extended lifetimes. Results of preliminary and ongoing screening tests for a large number of candidate polymeric glazing materials are presented. Based on these results, two specific glazings with moderate and poor weathering stability are selected to demonstrate how a service lifetime methodology can be applied to accurately predict the optical performance of these materials during in-service use. A summary is given for data obtained by outdoor exposure and indoor testing of polyvinyl chloride (PVC) and high temperature modified polycarbonate copolymer (coPC) materials, and an initial risk analysis is given for the two materials. Screening tests and analyses for service lifetime prediction are discussed. A methodology that provides a way to derive correlations between degradation experienced by materials exposed to controlled accelerated laboratory exposure conditions and materials exposed to in-service conditions is given, and a validation is presented for the methodology based upon durability test results for PVC and coPC. 相似文献
64.
为了适应MMS(多媒体短信息业务)的发展,提出了一个基于图像扭曲的变形动画生成机制。该机制不仅能够实时地产生效果新奇、富于戏剧性的GIF动画,而且能够根据不同终端的特点实现图像的自适应处理,从而使在无线网络上传输丰富多彩的图像文件变得更为方便。 相似文献
65.
Boiler tubes in power plants have finite life because of prolonged exposure to high temperature, stress and aggressive environment. Service-exposed platen superheater and reheater tubes (148,900 h) made of 2.25Cr-1 Mo steels in a 120 MW boiler of a thermal power plant were evaluated for remnant life. The investigation included hot tensile tests, hardness measurement, dimensional measurement, microscopy and creep tests. Experimentally determined yield and ultimate tensile strength, and estimated 10,000–100,000 h rupture strength in the temperature range 520–580 °C, exhibited a decreasing trend with increasing temperature. Microstructural study did not reveal any significant degradation in terms of creep cavities, cracks, graphitization, etc. Analysis of tensile and stress rupture data revealed that although there was degradation of the tubes due to prolonged service exposure in terms of the ultimate tensile strength values, stress rupture plots showed that the service exposed superheater and reheater tubes could remain in service for a length of more than 10 years at the operating hoop stress of 40 MPa/540 °C, provided no localised damage in the form of cracks or dents develop. 相似文献
66.
67.
微机MIS集成构造系统的研究与实践 总被引:2,自引:0,他引:2
微机MIS集成构造系统是基于软件重用理论,采用应用描述语言,扩展数据字典和标准预制软构件快速构造信息处理系统的一种应用开发工具环境。本文主要介绍其设计思想,基本结构,构造原理,设计原则和实际使用情况。 相似文献
68.
多版本软件通过设计相异性实现了软件容错。为了对这种方法进行研究,我们的课题实现了一个三版本软件系统,称之为SFTMP(SoftwareFault-TolerantMultiProcessor)。本文描述了SFTMP的硬件结构和软件执行支持环境,该环境包括同步、表决和监控功能、版本间的通讯及故障的恢复和重构。 相似文献
69.
文中讨论了一种基于窗口的对象用户界面设计思想及方法,详细描述了各种类的定义。在DOS环境下运用WatcomC++语言在微机上开发运行。它可以使用户方便地进行再开发工作,界面运用事件处理方式由窗口、弹出菜单、图标、按钮等组成。效果良好。 相似文献
70.
本文主要介绍Sun Openwindows Developer’s Guide3.0.1软件的简单使用和主要特点。 相似文献