全文获取类型
收费全文 | 35930篇 |
免费 | 1786篇 |
国内免费 | 1852篇 |
专业分类
电工技术 | 2022篇 |
技术理论 | 5篇 |
综合类 | 2490篇 |
化学工业 | 1521篇 |
金属工艺 | 1278篇 |
机械仪表 | 4408篇 |
建筑科学 | 2610篇 |
矿业工程 | 839篇 |
能源动力 | 1284篇 |
轻工业 | 809篇 |
水利工程 | 626篇 |
石油天然气 | 773篇 |
武器工业 | 316篇 |
无线电 | 3173篇 |
一般工业技术 | 1335篇 |
冶金工业 | 821篇 |
原子能技术 | 521篇 |
自动化技术 | 14737篇 |
出版年
2024年 | 26篇 |
2023年 | 149篇 |
2022年 | 306篇 |
2021年 | 422篇 |
2020年 | 437篇 |
2019年 | 316篇 |
2018年 | 375篇 |
2017年 | 472篇 |
2016年 | 614篇 |
2015年 | 820篇 |
2014年 | 1834篇 |
2013年 | 1711篇 |
2012年 | 2225篇 |
2011年 | 2942篇 |
2010年 | 2132篇 |
2009年 | 1974篇 |
2008年 | 2076篇 |
2007年 | 2660篇 |
2006年 | 2631篇 |
2005年 | 2470篇 |
2004年 | 2015篇 |
2003年 | 1973篇 |
2002年 | 1719篇 |
2001年 | 1226篇 |
2000年 | 960篇 |
1999年 | 969篇 |
1998年 | 776篇 |
1997年 | 627篇 |
1996年 | 527篇 |
1995年 | 447篇 |
1994年 | 332篇 |
1993年 | 286篇 |
1992年 | 226篇 |
1991年 | 180篇 |
1990年 | 125篇 |
1989年 | 126篇 |
1988年 | 98篇 |
1987年 | 55篇 |
1986年 | 31篇 |
1985年 | 50篇 |
1984年 | 50篇 |
1983年 | 36篇 |
1982年 | 31篇 |
1981年 | 25篇 |
1980年 | 18篇 |
1979年 | 16篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 6篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Visakha K. Nanayakkara Yasuyuki Ikegami Haruo Uehara 《International Journal of Refrigeration》2002,25(6)
This paper presents a novel neural network (NN) to control an ammonia refrigerant evaporator. Inspired by the latest findings on the biological neuron, a dynamic synaptic unit (DSU) is proposed to enhance the information processing capacity of artificial neurons. Treating the dynamic synaptic activity after the nonlinear somatic activity helps to capture the dynamics demarcated by the Gaussian activation pertaining to the input space. This practice leads to a remarkable reduction in curse of dimensionality. The proposed NN architecture has been compared with two other conventional architectures; one with dynamic neural units (DNUs) and the other with nonlinear static functions as perceptrons. The objective is to control evaporator heat flow rate and secondary fluid outlet temperature while keeping the degree of refrigerant superheat in the range 4–7 K at the evaporator outlet by manipulating refrigerant and evaporator secondary fluid flow rates. The drawbacks of conventional approaches to this problem are discussed, and how the novel method can overcome them are presented. An evolutionary approach is adopted to optimize the parameters of the NN controllers. Then evaporator process model is accomplished as a combination of governing equations and a sub NN resulting in a simple and sufficiently accurate model. The effectiveness of the proposed dynamic NN controller for the evaporator system model is validated using experimental data from the ammonia refrigeration plant. 相似文献
122.
企业网络信息管理系统的总体设计 总被引:1,自引:0,他引:1
介绍了企业网络信息管理系统总体设计方案,提出了软、硬件的设计方案和实现方法。该系统可以实时掌握控制各职能部门的运营状况,有效地调配企业资源,提高企业的市场竞争能力。 相似文献
123.
124.
The objective, strategy, and implementation details of a new undergraduate course, Internet-based Instrumentation and Control, are presented. The course has a companion laboratory that is supported by the National Science Foundation and industry. The combination is offered to senior-level undergraduate engineering students interested in sensing, instrumentation, control, and web programming that want to learn more about the integration of these technologies for solving real-world engineering problems. The course will also be offered to gifted high school seniors with similar interests and can serve as a vehicle to attract them to engineering disciplines. Preliminary assessment of the first offering of the course is encouraging and has shown that the course has achieved success in helping students understand concepts and master basic technologies for developing Internet-based automatic systems. 相似文献
125.
Ricardo Lima Author Vitae Author Vitae Claudio Reineri Author Vitae Author Vitae 《Computers & Electrical Engineering》2008,34(6):520-530
This paper presents a novel concept for power quality hardware and software architecture. Software tools related to detection, classification and characterization of power quality events can be integrated into a Distribution Control Center in which the interconnection between different subsystems is being carried out through the Internet allowing flexibility to the system. This system is implemented using wavelet analysis applied in all proposed algorithms. Different power quality events are taken as examples to illustrate the capabilities of the proposed method. The obtained results reveal that the proposed architecture is feasible to be implemented as an integral part of a control center system.The proposed system has the property of fast and accurate detection and classification of any power quality disturbance event and introduces a new PQ index determination that allows characterizing any type of disturbance including the non-periodic signals. 相似文献
126.
本文分析了造成ora-01555错误的原因,并提出解决办法。ora-01555错误一直是DBA与developer争论的焦点,解决其问题应是双方协调的结果。 相似文献
127.
鉴于目前电信的声讯系统中竞争的激烈性,它们急需要提高自身的系统集成度及高可用性,保证以最小的投资获得最丰厚的回报,由此出现了CompactPCI的系列产品,它不仅可以大大提高系统的集成度,同时对于系统的高可用性也进行了充分的考虑。本文将就声讯系统中基于CompactPCI的应用进行分析。 相似文献
128.
L. K. Isaev 《Measurement Techniques》2007,50(11):1214-1217
The main prerequisites are considered in a historical aspect and steps ate taken in creating a world-wide metrology system
with the aim of providing conditions for the mutual recognition of measurement results.
__________
Translated from Izmeritel’naya Tekhnika, No. 11. pp. 59–62, November, 2007. 相似文献
129.
一种数字电视条件接收系统的设计与实现 总被引:2,自引:2,他引:0
为支撑业务的安全开展,有线数字电视系统需提供一个安全可靠的加密系统,即条件接收系统。条件接收系统是对数字电视节目进行加密,以实现有线电视运营商对用户进行管理和收费。本文介绍了一种数字电视系统中的条件接收系统实现方案。 相似文献
130.
随着广播电视技术的不断发展 ,模拟信号传输向数字信号传输的转换已成为必然。介绍模数转换系统中放大器的性能、关键技术 ,并就放大器的选择作详细探讨。 相似文献