全文获取类型
收费全文 | 78499篇 |
免费 | 8170篇 |
国内免费 | 4269篇 |
专业分类
电工技术 | 13356篇 |
技术理论 | 13篇 |
综合类 | 5571篇 |
化学工业 | 9127篇 |
金属工艺 | 2644篇 |
机械仪表 | 3158篇 |
建筑科学 | 11161篇 |
矿业工程 | 2164篇 |
能源动力 | 13068篇 |
轻工业 | 2163篇 |
水利工程 | 1807篇 |
石油天然气 | 2209篇 |
武器工业 | 611篇 |
无线电 | 5713篇 |
一般工业技术 | 7787篇 |
冶金工业 | 3896篇 |
原子能技术 | 1249篇 |
自动化技术 | 5241篇 |
出版年
2024年 | 501篇 |
2023年 | 1699篇 |
2022年 | 2760篇 |
2021年 | 3002篇 |
2020年 | 3241篇 |
2019年 | 2822篇 |
2018年 | 2376篇 |
2017年 | 2854篇 |
2016年 | 3207篇 |
2015年 | 3161篇 |
2014年 | 5597篇 |
2013年 | 5165篇 |
2012年 | 5812篇 |
2011年 | 6485篇 |
2010年 | 5046篇 |
2009年 | 5042篇 |
2008年 | 4508篇 |
2007年 | 4934篇 |
2006年 | 3942篇 |
2005年 | 3030篇 |
2004年 | 2495篇 |
2003年 | 2152篇 |
2002年 | 1918篇 |
2001年 | 1661篇 |
2000年 | 1394篇 |
1999年 | 1113篇 |
1998年 | 892篇 |
1997年 | 708篇 |
1996年 | 646篇 |
1995年 | 465篇 |
1994年 | 417篇 |
1993年 | 336篇 |
1992年 | 247篇 |
1991年 | 228篇 |
1990年 | 187篇 |
1989年 | 147篇 |
1988年 | 130篇 |
1987年 | 95篇 |
1986年 | 66篇 |
1985年 | 96篇 |
1984年 | 82篇 |
1983年 | 52篇 |
1982年 | 71篇 |
1981年 | 33篇 |
1980年 | 42篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1959年 | 5篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
多缝式烧嘴点火器具有燃烧效率高,火焰长度易调,炉膛温度分布合理等优点,经工业试验证明,该点火器能满足攀钢烧结点火工艺要求,并有明显节能效果。 相似文献
92.
93.
Yasuhiro Kobayashi Toshiyuki Sawa Toshiyuki Furukawa Shigeru Kawamoto 《Electrical Engineering in Japan》2002,138(2):49-58
This paper describes a load dispatch method which minimizes power cost—[fuel cost]/[electric output]—for a power system with thermal plants and energy storage facilities. The proposed method employs fractional programming to convert a minimization problem with fractional objective function to a series of quadratic minimization problems, and semidefinite programming to solve converted problems. The method provides the optimum time‐dependent power output/input and storage level of energy storage facilities as well as time‐dependent power output of thermal plants. The method has been applied to a power system with five thermal plants, two energy storage facilities of various performances, and five load demands. The optimum load scheme of four time mesh points is obtained for the thermal plants and energy storage facilities. The fractional programming successfully converges the optimal scheme through a few iterations. The semidefinite programming deals with a variable matrix of 164 dimensions, and 185 inequality constraints. © 2001 Scripta Technica, Electr Eng Jpn, 138(2): 49–58, 2002 相似文献
94.
关于空调水系统节能的探讨 总被引:6,自引:0,他引:6
以空调冷冻水系统的节能为例 ,探讨空调系统节能的途径、存在的问题及解决办法 相似文献
95.
Because of its high–temperature chemical stability, SiC ceramic is a promising material for high-temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction. An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC. The microstructure of the FGM is classified into three regions: the SiC-Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC-Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC-Si FGM at the cold junction, at room temperature, was 108 times higher than that of a nongradient SiC ceramic. 相似文献
96.
本文就水库灌区多方位的水资源浪费状况。提出了水库应采用汛限分级方法多蓄水的观点;结合降雨,作物需水等建立了水库供水、渠道输配水的高效节水模型;同时对水库——渠道——田间灌水等全程节水技术进行了探讨。 相似文献
97.
The influence of alloying of Pt with 20 at.% of Ni, Co and Fe has been studied in the hydrogenation of 1,3 butadiene. Iron induces the more important modifications, with both higher activity and selectivity. The results are discussed in terms of the surface segregation, the local order in surface and the electronic properties measured by photoemission of core levels. 相似文献
98.
本文运用“软科学”一即通过建立数学模型,进行系统分析和系统优化,阐述对蒸汽管网优化运行的方法及原理,达到提高供热效率及节能降耗的目的. 相似文献
99.
100.
The environmental and socio‐economic impacts of biomass utilization by co‐firing with brown coal in an existing thermoelectric unit in Greece or through its pure combustion in a new plant were studied and evaluated in this work. The 125 MWe lignite‐fired power plant in Ptolemais Power Station (Western Macedonia) was used as reference system. The environmental benefits of the alternative biomass exploitation options were quantified based on the life cycle assessment methodology, as established by SETAC, while the BIOSEM technique was used to carry out socio‐economic calculations. The obtained results showed clear environmental benefits of both biomass utilization alternatives in comparison with the reference system. In addition, co‐firing biomass with lignite in an existing unit outperforms the combustion of biomass exclusively in a new plant, since it exhibits a better environmental performance and it is a low risk investment with immediate benefits. A biomass combustion unit requires a considerably higher capital investment and its benefits are more evident in the long run. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献