全文获取类型
收费全文 | 23918篇 |
免费 | 2499篇 |
国内免费 | 893篇 |
专业分类
电工技术 | 1966篇 |
技术理论 | 1篇 |
综合类 | 1849篇 |
化学工业 | 5701篇 |
金属工艺 | 933篇 |
机械仪表 | 1146篇 |
建筑科学 | 1825篇 |
矿业工程 | 560篇 |
能源动力 | 2694篇 |
轻工业 | 3424篇 |
水利工程 | 442篇 |
石油天然气 | 730篇 |
武器工业 | 155篇 |
无线电 | 792篇 |
一般工业技术 | 2455篇 |
冶金工业 | 739篇 |
原子能技术 | 403篇 |
自动化技术 | 1495篇 |
出版年
2024年 | 104篇 |
2023年 | 322篇 |
2022年 | 684篇 |
2021年 | 854篇 |
2020年 | 844篇 |
2019年 | 761篇 |
2018年 | 762篇 |
2017年 | 968篇 |
2016年 | 1008篇 |
2015年 | 932篇 |
2014年 | 1466篇 |
2013年 | 2545篇 |
2012年 | 1583篇 |
2011年 | 1843篇 |
2010年 | 1197篇 |
2009年 | 1194篇 |
2008年 | 1095篇 |
2007年 | 1329篇 |
2006年 | 1222篇 |
2005年 | 1049篇 |
2004年 | 892篇 |
2003年 | 773篇 |
2002年 | 679篇 |
2001年 | 602篇 |
2000年 | 427篇 |
1999年 | 419篇 |
1998年 | 309篇 |
1997年 | 285篇 |
1996年 | 224篇 |
1995年 | 185篇 |
1994年 | 139篇 |
1993年 | 111篇 |
1992年 | 101篇 |
1991年 | 77篇 |
1990年 | 68篇 |
1989年 | 49篇 |
1988年 | 36篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 23篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1961年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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
102.
A model for building integrated photovoltaic systems has been developed and implemented in a dynamic simulation tool. This tool takes into account the thermal interactions between the PV collector and the building. The influence of the type of integration upon the PV collector efficiency has been evaluated and hybrid PV/air collectors have been studied. An overall efficiency is defined, including the production of electricity and heat. A case study has been performed on two different typical buildings. In the case of a multi-crystalline silicon PV collector integrated on the roof of a single family house located in Paris, the efficiency of unventilated PV modules fixed on the roof is 14%. If the PV collector is used to preheat the ventilation air, the efficiency reaches 20%. A proper building integration also improves the environmental balance of PV technologies over their life cycle. 相似文献
103.
Alfalfa juice was extracted from plants during the graving phases of the first and second crops. The alfalfa juice was dried and solute concentrations were measured periodically during the process using freezing point depression (FPD) as an indicator. Solute/solvent weight ratios were calculated from the freezing point depression of fresh unconcentrated 'uice extracted from both firsc and second crops. At the time of harvest, tie FPD was a function of this ratio. The first and second crops behaved distinctively different during the drying process, with the second having a larger soluce concentration and a greater FPD at a given moisture content. The appearance of preci itate during the drying process and the general1 large FPD makes this materiay a questionable product for drying vitg low temperature processes. 相似文献
104.
数字加速度传感器ADXL210在轨检仪中的应用 总被引:2,自引:0,他引:2
介绍了一种轨道检测仪及其重要传感器数字加速度传感器ADXL210的工作原理、功能、应用,并给出了ADXL210与MCS-51单片机的接口硬件电路和软件程序。 相似文献
105.
Comparison of different absorption heat cycles is not always made on the correct manner. This also includes comparison of an ideal absorption cycle with a mechanical analogy. A new Carnot model operating with two heat engines and two mechanical heat pumps is defined to be the correct and logical way to describe the mechanical analogy for an absorption heat pump and an absorption heat transformer. General equations for the Carnot coefficient of performance, COPr, are exemplified and simulated for an absorption heat pump and an absorption heat transformer, and an entropy flow fraction diagram is introduced. The important fact that the absorption heat cycles must operate under the same conditions when they are compared is discussed. 相似文献
106.
107.
108.
Elena Crespi Antonio Capolongo Davide Fissore Antonello A. Barresi 《Drying Technology》2008,26(3):349-356
The aim of this article is to develop an experiment and a procedure to investigate the restoration of water-damaged paper and archival materials using freeze drying in order to allow a reproducible test and comparison of the influence of different operating conditions on drying time and restored paper quality. Firstly, a reproducible method for the preparation of soaked samples simulating water-damaged paper has been developed. Then, the samples have been freeze-dried in a laboratory-scale apparatus that allowed monitoring the temperature as well as the weight of the samples. The technique of evaporative freezing, which reduces the drying time required, has been used in this case. An innovative procedure for the visualization of the progress of the drying process has been validated, thus allowing the validation of a simple phenomenological model of the time evolution of the ice core volume; in addition, data on the residual moisture of the dried paper sheets in different zones have been given. Finally, optimization of this particular drying process by using simple or more sophisticated approaches has been discussed. 相似文献
109.
110.
本文对混合工质R407C与R12的物理和热力性质进行了比较分析,并针对汽车空调制冷系统的特点,对两种工质在变工况下进行了制冷系统的理论循环分析,阐明了在汽车空调制冷系统中使用R407C的可行性。 相似文献