全文获取类型
收费全文 | 9831篇 |
免费 | 695篇 |
国内免费 | 363篇 |
专业分类
电工技术 | 223篇 |
综合类 | 717篇 |
化学工业 | 1598篇 |
金属工艺 | 91篇 |
机械仪表 | 242篇 |
建筑科学 | 832篇 |
矿业工程 | 2805篇 |
能源动力 | 753篇 |
轻工业 | 66篇 |
水利工程 | 242篇 |
石油天然气 | 609篇 |
武器工业 | 11篇 |
无线电 | 287篇 |
一般工业技术 | 283篇 |
冶金工业 | 330篇 |
原子能技术 | 68篇 |
自动化技术 | 1732篇 |
出版年
2024年 | 6篇 |
2023年 | 92篇 |
2022年 | 191篇 |
2021年 | 252篇 |
2020年 | 370篇 |
2019年 | 250篇 |
2018年 | 257篇 |
2017年 | 225篇 |
2016年 | 284篇 |
2015年 | 268篇 |
2014年 | 457篇 |
2013年 | 489篇 |
2012年 | 541篇 |
2011年 | 810篇 |
2010年 | 629篇 |
2009年 | 547篇 |
2008年 | 504篇 |
2007年 | 635篇 |
2006年 | 687篇 |
2005年 | 584篇 |
2004年 | 515篇 |
2003年 | 489篇 |
2002年 | 302篇 |
2001年 | 208篇 |
2000年 | 193篇 |
1999年 | 228篇 |
1998年 | 155篇 |
1997年 | 131篇 |
1996年 | 121篇 |
1995年 | 82篇 |
1994年 | 95篇 |
1993年 | 71篇 |
1992年 | 48篇 |
1991年 | 24篇 |
1990年 | 25篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
The devolatilization and volatile combustion of a single coal particle in spouted and spout-fluid beds have been studied. The results showed that the flame extinction time increases with the particle diameter, and decreases with the bed temperature. When the bed temperature and the air flow rate were fixed, the operation modes (spouted or spout-fluid bed) showed less effect on the mean flame extinction time. A mathematical model of the spouted bed mode for preignition and postignition periods has also been developed assuming the devolatilization rate to be controlled by heat transfer and multireaction pyrolysis kinetics based on volatile products. Ignition, heat transfer back from the volatile flame to the particle surface, variation in flame temperature, and the hydrodynamics of SB are taken into account. The model predictions, with some adjusting parameters, were in good agreement with experimental results. 相似文献
43.
本文通过两栋不同加固方案的二层农村楼房抗采动现场试验结果的分析,对不同加固措施的作用机理、效果及其设置条件进行了研究探讨,并提出,在农村采动区兴建抗采动变形楼房,是解放村庄下压煤、节约耕地和降低加固费用的途径。 相似文献
44.
45.
非均相成核中间相炭微球的形成过程及其结构演变 总被引:15,自引:3,他引:12
以含有喹啉不溶物的煤焦油沥青为原料,在410℃、不同反应时间下获得一系列中间相炭微球(MCMB)和小于0.5μm的碳质颗粒(SCP)。通过对中间相沥青的软化点、族组成和MCMB、SCP的形貌及MCMB断面结构的分析,认为非均相成核MCMB的形成和生长过程不同于均相成核的融并生长过程,而是SCP碳质颗粒的构筑过程,我们称之为“球形基本单元构筑”过程。在MCMB生长过程中,体系的黏度对SCP的形成和MCMB的生长起着重要的作用。非均相成核MCMB的内部结构不是三种模型结构(“地球仪”型、“洋葱”型和“同心圆”型)中的任一种,而是炭层具有收缩点的复杂结构,并且球体的结构不具有“继承性”,即随着反应时间的延长而不断发生变化和调整。MCMB内部分子在球体生长过程中的主要变化趋势是分子的不断缩合长大,而不是分子片层的平行趋向。 相似文献
46.
面阵列封装器件在电子产品中的使用率逐年上升,如何实现其高速贴装是影响生产线效率的重要因素。从不同的角度论述了面阵列封装器件实现高速贴装的手段与技术。 相似文献
47.
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
48.
B. Basil Beamish 《Fuel》2008,87(1):125-130
Adiabatic self-heating tests have been conducted on subbituminous coal cores from the same seam profile, which cover a mineral matter content range of 11.2-71.1%. In all cases the heat release rate does not conform to an Arrhenius kinetic model, but can best be described by a third order polynomial. Assessment of the theoretical heat sink effect of the mineral matter in each of the tests reveals that the coal is less reactive than predicted using a simple energy conservation equation. There is an additional effect of the mineral matter in these cases that cannot be explained by heat sink alone. The disseminated mineral matter in the coal is therefore inhibiting the oxidation reaction due to physicochemical effects. 相似文献
49.
Composition and morphology of char particles of fly ashes from industrial burning of high-ash coals with different reactivity 总被引:1,自引:0,他引:1
A comparative investigation of the composition and the morphology of char particles was conducted: char particles were recovered from fly ashes of two power stations in Russia from burning of high- and low-reactivity high-ash coals; the known results of studies of char particles generated in laboratory conditions from coals characterized according to the ASTM D388-98a standard were also used. The composition of organic and mineral components of different fraction char particles was studied. An inverse correlation between the content of the organic substance and the iron content in char particles was identified. The morphology of the char particles for the three main types (Cenospheric, Network and Solid) and the influence of coal reactivity and temperature on char morphology were investigated. The morphology of the mineral component of char particles of the two varieties of coals was also studied. It was shown that the high-temperature of industrial burning of Ekibastuz coal results in melting of the mineral substance and forming of micron-scale microspheres located in the lamellar porous structure of the carbon matrix. 相似文献
50.
Çan, Çatala?z?, Seyitömer and Af?in-Elbistan thermal power plant fly ashes were used to investigate the sintering behavior of fly ashes. For this purpose, coal fly ash samples were sintered to form ceramic materials without the addition of any inorganic additives or organic binders. In sample preparation, 1.5 g of fly ash was mixed in a mortar with water. Fly ash samples were uniaxially pressed at 40 MPa to achieve a reasonable strength. The powder compacts were sintered in air. X-ray diffraction analysis revealed that quartz (SiO2), mullite (Al6Si2O13), anorthite (CaAl2Si2O8), gehlenite (Ca2Al2SiO7) and wollastonite (CaSiO3) phases occurred in the sintered samples. Scanning electron microscopy investigations were conducted on the sintered coal fly ash samples to investigate the microstructural evolution of the samples. Different crystalline structures were observed in the sintered samples. The sintered samples were obtained having high density, low water adsorption and porosity values. Higher Al2O3 + SiO2 contents caused to better properties in the sintered materials. 相似文献