全文获取类型
收费全文 | 96531篇 |
免费 | 11987篇 |
国内免费 | 4588篇 |
专业分类
电工技术 | 50115篇 |
技术理论 | 3篇 |
综合类 | 7445篇 |
化学工业 | 2869篇 |
金属工艺 | 1797篇 |
机械仪表 | 4008篇 |
建筑科学 | 3020篇 |
矿业工程 | 1980篇 |
能源动力 | 7954篇 |
轻工业 | 1035篇 |
水利工程 | 2513篇 |
石油天然气 | 755篇 |
武器工业 | 601篇 |
无线电 | 14106篇 |
一般工业技术 | 3186篇 |
冶金工业 | 1687篇 |
原子能技术 | 2121篇 |
自动化技术 | 7911篇 |
出版年
2024年 | 384篇 |
2023年 | 1167篇 |
2022年 | 2288篇 |
2021年 | 2740篇 |
2020年 | 3141篇 |
2019年 | 2562篇 |
2018年 | 2294篇 |
2017年 | 3369篇 |
2016年 | 3611篇 |
2015年 | 4200篇 |
2014年 | 7180篇 |
2013年 | 5700篇 |
2012年 | 8122篇 |
2011年 | 8774篇 |
2010年 | 6419篇 |
2009年 | 6360篇 |
2008年 | 6242篇 |
2007年 | 7190篇 |
2006年 | 6378篇 |
2005年 | 5082篇 |
2004年 | 4123篇 |
2003年 | 3327篇 |
2002年 | 2542篇 |
2001年 | 2199篇 |
2000年 | 1827篇 |
1999年 | 1316篇 |
1998年 | 867篇 |
1997年 | 693篇 |
1996年 | 671篇 |
1995年 | 509篇 |
1994年 | 455篇 |
1993年 | 273篇 |
1992年 | 242篇 |
1991年 | 146篇 |
1990年 | 120篇 |
1989年 | 109篇 |
1988年 | 76篇 |
1987年 | 58篇 |
1986年 | 38篇 |
1985年 | 36篇 |
1984年 | 59篇 |
1983年 | 49篇 |
1982年 | 52篇 |
1981年 | 24篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1959年 | 13篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
121.
PMM8731是日本三洋电机公司生产的步进电机脉冲分配器。而SI-7300则是日本三青公司生产的高性能步进电机集成功率放大器。它们和单片机一起可构成一种高效电机控制驱动电路。文中介绍了PMM8713与SI-7300的功能 ,给出了由它们组成的功率驱动电路及其在步进电机上的应用方法 相似文献
122.
D.H.R. Price J.A. Sharp 《International Journal of Electrical Power & Energy Systems》1985,7(3):131-137
Peak demand forecasts obtained from six different univariate forecasting methods, under a range of conditions, were used to drive a capacity acquisition model of a large electrical supply system; and the resulting physical and financial performance of the model was observed for each set of forecasts. The results obtained are discussed in the context of their implications for the choice of load forecasting method used in capacity acquisition planning by a power supply undertaking. 相似文献
123.
分析了电石法PVC生产链中电石炉烟气及电厂烟气二氧化硫的排放情况,指出利用电石炉烟气中的CO合成氨、再将合成氨用于燃煤电厂烟气的"氨法"脱硫是具有较大应用潜力的循环经济产业链。 相似文献
124.
Sirisha Nerella Debendra K. Das Godwin A. Chukwu Abhijit Y. Dandekar Santanu Khataniar Shirish L. Patil 《Petroleum Science and Technology》2003,21(7):1275-1294
Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations. 相似文献
125.
126.
127.
128.
嵌入式Web服务器在中小水电信息采集系统中的应用 总被引:1,自引:1,他引:0
中小水电站大多数建在偏远山区,并网管理难度非常大,解决中小水电站的信息传输是主要的技术难点之一。随着计算机技术的发展,嵌入式Web服务器技术在远程监控和实时通信系统中的应用越来越广泛。将Web技术引入中小水电站信息采集系统中,可以实现对中小水电站基于浏览器方式的远程监控。文中结合中小水电站通信结构,介绍了嵌入式Web服务器技术在中小水电站信息采集系统中的应用。 相似文献
129.
We have previously investigated effects of radiation levels on power quality of a number PV-grid interactive systems in Thailand, in terms of harmonics and voltage variation at the point of common coupling (PCC). In this paper, we focus on the nature of components of complex power (actual, reactive and apparent power) of inverter output of a PV-grid interactive system due to low radiation, below 400 W/m2. The system being investigated has an array of 4.2 kWp and representative of roof top units. It is observed that a PV array supplies increasing real power, in magnitude and as percentage of complex power, at high values of radiation. At low radiation level when the array does not provide enough output power, reactive power is drawn from distribution transformer and fed into an inverter and loads. Based on results from the test site and long term radiation data of Bangkok, we then estimate energy available from low radiation from a hypothetical PV-grid interactive unit in Bangkok of a similar size. It can be seen that for a tropical climate like Thailand a significant amount of energy, 20–30% of radiation energy, is in the form of reactive power. Methods must be devised to capture this low radiation energy and converted into real power form. 相似文献
130.
Seog Geun Kang 《ETRI Journal》2006,28(2):235-238
In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR. 相似文献