全文获取类型
收费全文 | 32838篇 |
免费 | 4422篇 |
国内免费 | 727篇 |
专业分类
电工技术 | 2326篇 |
技术理论 | 2篇 |
综合类 | 2236篇 |
化学工业 | 7935篇 |
金属工艺 | 186篇 |
机械仪表 | 464篇 |
建筑科学 | 1301篇 |
矿业工程 | 16043篇 |
能源动力 | 2474篇 |
轻工业 | 53篇 |
水利工程 | 177篇 |
石油天然气 | 825篇 |
武器工业 | 6篇 |
无线电 | 178篇 |
一般工业技术 | 479篇 |
冶金工业 | 1887篇 |
原子能技术 | 37篇 |
自动化技术 | 1378篇 |
出版年
2024年 | 46篇 |
2023年 | 166篇 |
2022年 | 697篇 |
2021年 | 1141篇 |
2020年 | 1286篇 |
2019年 | 699篇 |
2018年 | 766篇 |
2017年 | 698篇 |
2016年 | 969篇 |
2015年 | 1197篇 |
2014年 | 2459篇 |
2013年 | 2116篇 |
2012年 | 3545篇 |
2011年 | 2921篇 |
2010年 | 2082篇 |
2009年 | 2100篇 |
2008年 | 1888篇 |
2007年 | 2081篇 |
2006年 | 1782篇 |
2005年 | 1516篇 |
2004年 | 1164篇 |
2003年 | 1108篇 |
2002年 | 857篇 |
2001年 | 847篇 |
2000年 | 676篇 |
1999年 | 535篇 |
1998年 | 374篇 |
1997年 | 360篇 |
1996年 | 297篇 |
1995年 | 253篇 |
1994年 | 194篇 |
1993年 | 105篇 |
1992年 | 105篇 |
1991年 | 57篇 |
1990年 | 41篇 |
1989年 | 28篇 |
1988年 | 39篇 |
1987年 | 30篇 |
1986年 | 22篇 |
1985年 | 187篇 |
1984年 | 223篇 |
1983年 | 169篇 |
1982年 | 145篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The present paper will outline the main aspects of the design and construction of cooling towers in Germany in the last decade. As part of electricity generating power plants, cooling towers play a significant role for the availability of reliable energy supplies, in a manner compatible with environmental requirements. They definitely belong to the largest and thinnest concrete structures at present. Because of the combined action of wind, thermal and moisture effects, special care has to be taken with regard to fatigue, cracking and corrosion to ensure an adequate level of safety and durability. Such a design strategy has been employed for the world’s tallest cooling tower at the Niederaussem power plant in Germany, with an overall height of 200 m and thickness values of 22–24 cm. Special considerations included the realistic non-axisymmetric distribution of soil characteristics, wind action due to interference effects (as determined by wind-tunnel tests), optimisation of the shell shape to improve structural and dynamic behaviour, injection of the cleaned flue-gas into the cooling tower, and the use of high-performance concrete (85 MPa) to improve shell resistance against acid attack by the cleaned flue-gas. The paper will present some results of an actual research project on this problem, which was conducted at the University of Wuppertal, to explore the use of high-performance concrete on design, stability and durability of cooling tower shells. 相似文献
72.
73.
介绍65t/h煤粉炉的基本概况和存在的问题,详细阐述了采用水平浓缩煤粉燃烧技术对原燃烧器的改造过程,对改造前后运行参数及经济效益进行了对比。 相似文献
74.
75.
Relationship Between Coal Powder and Its Combustibility 总被引:1,自引:1,他引:0
Coal‘s volatile component ,ash and fixed carbon content have different function in different stages of a combustion process,but the traditional coal classification can precisely show its combustion property.In this experiment coal‘s evaluation indeves(ignition index Di),(burn off index Df) were used to qualitatively show the ignition property and combustion ending property of coal samples.Meanwhile,considering actual heating circumstances in calciner(in cement plants),this thesis established the relationship among the ignition index,burn off index and coal‘s industrial analysis value,which makes it possible for the user to predict the quality of coal before using it and is very valuable in practice. 相似文献
76.
The medium coking coal fines of − 0.5 mm from Jharia coal field were taken for this investigation. The release analysis of the composite coal reveals that yield is very low at 10.0% ash, about 25% at 14% ash and 50% at 17% ash level. The low yield is caused by the presence of high ash finer fraction. The size-wise ash analysis of − 0.5 mm coal indicated that − 0.5 + 0.15 mm fraction contains less ash than − 0.15 mm fraction. Thus, the composite feed was split into − 0.5 + 0.15 mm and − 0.15 mm fractions and subjected to flotation separately. The low ash bearing fraction (− 0.5 + 0.15 mm) was subjected to two stages collectorless flotation to achieve the concentrate with 10% ash. The cleaner concentrate (18.9%) with 10% ash was recovered which has an application in metallurgical industries. The concentrate of 30.2% yield with 12.5% ash could be achieved in one stage collectorless flotation which is suitable for use in coke making as sweetener. As the − 0.15 mm fraction contains relatively high ash, collector aided flotation using sodium silicate was performed to get a concentrate of 23.6% yield with about 17% ash. The blending of this product with cleaner tail obtained from − 0.5 + 0.15 mm produces about 35.0% yield with 17% ash and that can be utilized for coke making. The reject from the two fractions can be used for conventional thermal power plant or cement industries using a 23.5% ash after one stage collector aided flotation and the final tailings produced content ash of 61.6% can be used for fluidization combustion bed (FBC). This eventually leads to complete utilization of coal. 相似文献
77.
采空区治理工程中注浆管的起拔及重复利用 总被引:1,自引:1,他引:0
以某采空区治理工程为例,介绍了采用正反丝连接注浆管的新方法,成功地解决了注浆管的起拔及重复利用问题,并对新法与不拔管及常规拔管方法的经济性进行了分析比较。 相似文献
78.
79.
《Fuel Processing Technology》1994,40(2-3):269-275
The annual SO2 emission is approx. 0.6 million tons in Hungary because of the high amount of sulphur in the power plant coals. Since Hungary has signed the European Environmental Agreement, the high sulphur emission has to be gradually reduced. To overcome the acid rain problem, the biodesulphurization of Hungarian power plant coals has also been started in Hungary. The R&D programe of biodesulphurization has been launched in 1990. According to our findings the biodesulphurization process is a suitable tool for reducing the pyritic sulphur content in lignite and sub-bituminous coal. 相似文献
80.
Trace element evaporation during coal gasification based on a thermodynamic equilibrium calculation approach 总被引:1,自引:0,他引:1
《Fuel》2003,82(2):137-145
Thermodynamic equilibrium calculations using the HSC-Chemistry program were performed to determine the distribution and mode of occurrence of potentially toxic and corrosive trace elements in gases from coal gasification processes. The influence of temperature, pressure and gas atmospheres on equilibrium composition was evaluated. In these reducing conditions, the behaviour of the trace elements is complex, but some form of organization can be attempted. Elements were classified into three groups. Group A includes those elements that, according to thermodynamic data at equilibrium, could probably be condensed in coal gasification. Mn is classified in this group. Group B contains those elements that could be totally or partially in gas phase in gas cleaning conditions, and can be divided into two subgroups, depending on whether the cleaning conditions are hot or cold. Co, Be, Sb, As, Cd, Pb, Zn, Ni, V, Cr are elements in this group. Group C contains those elements that could be totally in gas phase in all the possible conditions, including flue gas emissions. Se, Hg and B are the elements that make up this group. 相似文献