全文获取类型
收费全文 | 1084篇 |
免费 | 31篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 50篇 |
综合类 | 59篇 |
化学工业 | 197篇 |
金属工艺 | 74篇 |
机械仪表 | 64篇 |
建筑科学 | 63篇 |
矿业工程 | 41篇 |
能源动力 | 98篇 |
轻工业 | 23篇 |
水利工程 | 9篇 |
石油天然气 | 67篇 |
武器工业 | 2篇 |
无线电 | 62篇 |
一般工业技术 | 105篇 |
冶金工业 | 27篇 |
原子能技术 | 29篇 |
自动化技术 | 179篇 |
出版年
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 22篇 |
2020年 | 24篇 |
2019年 | 17篇 |
2018年 | 18篇 |
2017年 | 23篇 |
2016年 | 28篇 |
2015年 | 26篇 |
2014年 | 54篇 |
2013年 | 43篇 |
2012年 | 47篇 |
2011年 | 91篇 |
2010年 | 72篇 |
2009年 | 66篇 |
2008年 | 59篇 |
2007年 | 64篇 |
2006年 | 59篇 |
2005年 | 46篇 |
2004年 | 41篇 |
2003年 | 49篇 |
2002年 | 33篇 |
2001年 | 23篇 |
2000年 | 13篇 |
1999年 | 33篇 |
1998年 | 22篇 |
1997年 | 23篇 |
1996年 | 21篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1149条查询结果,搜索用时 15 毫秒
1.
ABSTRACT Design and implementation of an effective dissemination programme for decentralised renewable energy system necessitate an accurate estimate of its utilisation potential. Hence, in this study, an attempt has been made to develop frameworks to estimate the utilisation potential of decentralised renewable energy systems in the state of Uttarakhand in India. Estimations imply large resource, technical and economic potentials of the domestic solar water heater, solar home system, solar lantern, family size biogas plant and improved biomass cookstove in Uttarakhand. With higher impact on the purchasing power of households, prevailing soft loan scheme has been found to be more appropriate than a capital subsidy for promoting the usage of decentralised renewable energy systems. 相似文献
2.
3.
李振涛 《导弹与航天运载技术》1993,(5):16-26
本文给出了一组不仅能用于卫星轨道计算,同时也能用于导弹自由飞行轨道的中间轨道计算公式。引组公式的解与二体问题解有很好的可比性。由于导弹轨道与卫星轨道有很大不同,故计算中的各使用常数的取值范围也有很大不同。 相似文献
4.
Air cleaning as a means of mitigating the risks arising from exposure to indoor radon progeny has been evaluated in a single-family house in the north eastem US. using an automated, semi-continuous activity-weighted size distribution measurement system. The measurements included radon concentration, condensation nuclei count, and activity-weighted size distribution of radon decay products. Measurements were made in the house with and without an operating air filtration system and with various particle sources common to normal indoor activities operating. Aerosols were generated by running water in a shower, candle burning, cigarette smoking, vacuuming, opening doors, and cooking. Using a room model, the changes in attachment rates, average attachment diameters, and deposition rates of the unattached fraction with and without the air cleaning system were calculated. In the presence of active aerosol sources, the air filtration unit typically reduced the concentration of particles within the hour following the end of particle generation. After candle burning, cigarette smoking, and vacuuming in the bedroom, the reductions of PAEC by air filtration are about 60% with the air filtration system operating in the bedroom. During cooking in the kitchen, the reductions of PAEC in the bedroom with the air filtration system were about 40%. However, for all cases the dose reductions were smaller than the particle and PAEC reductions. For those particles that were generated within the bedroom, there was a 20% to 50% reduction in dose. In the case of cooking where the door was open and particles infiltrated from the rest of the house, the dose reduction was only 5% on average and appears to be insignificant. Thus, the dose reductions were h e r than the reductions in activity concentration, but there were no cases where the estimated dose actually increased. 相似文献
5.
6.
从理论和实验两方面对静电感应晶体管(BSIT)的开关时间进行了分析和测量,提出了简单的分析方法,将影响BSIT开关时间的各个因素归结为结构因子和材料因子,从而简化了分析影响BSIT开关时间的因素,对于BSIT的实际工艺,结构设计有指导意义。 相似文献
7.
8.
The anodic oxidation of 3,3′-dimethoxybenzidine and its derivatives were studied by cyclic voltammetry, voltammetry at a rotating platinum electrode, chronopotentiometry and constant potential coulometry. The exhaustive oxidation of 3,3′-dimethoxybenzidine led at the potential of the first oxidation peak and second oxidation peak, respectively, to a stable cation radical salt (characterized by ESR spectroscopy) and to a quinone-diimine. Whereas, 3,3′-dimethoxy-N,N,N′,N′-tetramethylbenzidine afforded directly a dication salt owing to potential inversion 3,3′-dimethoxy-N,N,N′,N′-tetraethylbenzidine gave the corresponding soluble cation radical salt. 相似文献
9.
10.
Poroussilicon(PS)wasfoundtoemitvisibleluminescenceatroomtemperaturebyCanhamin1990[1].Thisphenomenonimpliedapotentialapplicati... 相似文献