收费全文 | 8753篇 |
免费 | 762篇 |
国内免费 | 393篇 |
电工技术 | 1002篇 |
综合类 | 728篇 |
化学工业 | 428篇 |
金属工艺 | 337篇 |
机械仪表 | 1347篇 |
建筑科学 | 398篇 |
矿业工程 | 182篇 |
能源动力 | 347篇 |
轻工业 | 134篇 |
水利工程 | 79篇 |
石油天然气 | 215篇 |
武器工业 | 88篇 |
无线电 | 1718篇 |
一般工业技术 | 425篇 |
冶金工业 | 203篇 |
原子能技术 | 132篇 |
自动化技术 | 2145篇 |
2024年 | 59篇 |
2023年 | 138篇 |
2022年 | 225篇 |
2021年 | 258篇 |
2020年 | 219篇 |
2019年 | 140篇 |
2018年 | 160篇 |
2017年 | 188篇 |
2016年 | 239篇 |
2015年 | 336篇 |
2014年 | 599篇 |
2013年 | 554篇 |
2012年 | 722篇 |
2011年 | 766篇 |
2010年 | 527篇 |
2009年 | 490篇 |
2008年 | 522篇 |
2007年 | 677篇 |
2006年 | 558篇 |
2005年 | 495篇 |
2004年 | 437篇 |
2003年 | 331篇 |
2002年 | 232篇 |
2001年 | 222篇 |
2000年 | 159篇 |
1999年 | 132篇 |
1998年 | 86篇 |
1997年 | 103篇 |
1996年 | 82篇 |
1995年 | 55篇 |
1994年 | 51篇 |
1993年 | 38篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1958年 | 6篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1951年 | 1篇 |
For the undegraded state of the module, the efficiency model allowed us to deduce the efficiency at Standard Test Conditions, STC, and its temperature coefficient at STC, which were 11.58% and minus 0.050%/°C, respectively. The output of the undegraded module under STC was found to be 42.4 W, i.e., 6% higher than specified by the manufacturer (40 W). Furthermore, the efficiency does not decrease with increasing air mass. At a cell temperature of 25 °C and a relative air mass of 1.5, the module has a maximum in efficiency of 12.0% at an irradiance of about 650 W/m2. This indicates that the series-resistance losses become significant at higher irradiances. Hence, improving the transparent conducting oxide (TCO) electrode on the front side of the cells might lead to a higher output at high irradiances.
Identical testing and modeling were repeated after having exposed the module to real weather conditions for one year. We found that the STC efficiency was reduced by 9.0%, from 11.58 down to 10.54%. The temperature coefficient of the efficiency had changed from minus 0.050 %/°C to minus 0.039%/°C. These results indicate possible chemical changes in the semiconductor film. The output of the module at STC was reduced by 9.0% from 42.4 W down to 38.6 W.
Using meteorological data from a sunny site in the South of Jordan (Al Qauwairah) and the efficiency model presented here allows us to predict the yearly electricity yield of the CIS module in that area. Prior to degradation, the yield was found to be 362 kWh/m2 for the Sun-tracked module; and 265 kWh/m2 for the fix-installed module (South-oriented, at an inclination angle of 30°). After degradation the corresponding yields were found to be 334 and 241 kWh/m2; meaning losses of 8.4% and 9.5%, respectively. (Note: all units of energy, kWh, are referred to the active cell area.) Having available efficiency models for other module types, similar predictions of the yield can be made, facilitating the comparisons of the yearly yields of different module types at the same site. This in turn allows selecting the best module type for a particular site. 相似文献