全文获取类型
收费全文 | 1053篇 |
免费 | 11篇 |
国内免费 | 16篇 |
专业分类
化学 | 195篇 |
力学 | 36篇 |
综合类 | 1篇 |
数学 | 10篇 |
物理学 | 168篇 |
综合类 | 670篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 36篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 26篇 |
2015年 | 21篇 |
2014年 | 76篇 |
2013年 | 53篇 |
2012年 | 82篇 |
2011年 | 95篇 |
2010年 | 80篇 |
2009年 | 84篇 |
2008年 | 56篇 |
2007年 | 70篇 |
2006年 | 48篇 |
2005年 | 34篇 |
2004年 | 42篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2001年 | 18篇 |
2000年 | 20篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 17篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有1080条查询结果,搜索用时 31 毫秒
91.
92.
等离子发射光谱法测定煤中总硫的方法研究 总被引:5,自引:0,他引:5
本文提出以ICP-AES直接测定煤中总硫。通过对样品溶液的制备、光谱干扰等方面的研究,确定了最佳分析条件,建立了以ICP-AES测定煤中总硫的方法。方法快速、准确,测定结果与国标法一致。方法回收率在96%以上,六次测定相对标准偏差小于3%。 相似文献
93.
徐继来 《科技情报开发与经济》2006,16(16):247-248
阐述了成庄矿洗选厂原有模块选洗末煤技术存在的问题,介绍了对其进行改造的过程,通过经济效益分析,指出了对其进行技术改造的可行性。 相似文献
94.
Investigation of operational parameters for an industrial CFB combustor of coal, biomass and sludge 总被引:1,自引:0,他引:1
Manon Van de Velden Jan Baeyens Bill Dougan Alan McMurdo 《中国颗粒学报》2007,5(4):247-254
The combustion of coal and/or biomass (sludge, wood waste, RDF, etc.) in a circulating fluidized bed has been a commercial topper for over 20 years, and references to principles and applications are numerous and widespread although few data are presented concerning the operation of large scale CFB-units. The authors studied the CFB-combustion at UPM-Kymmene (Ayr), a major paper mill relying for its steam production upon the combustion of coal (80-85 %), wood bark (5-10%) and wastewater treatment sludge (5-10%). The maximum capacity of the CFB is 58 MWth. A complete diagnostic of the operation was made, and additional tests were performed to assess the operating mode. The plant schematics, relevant dimensions and process data are given. To assess the operation of the UPM-CFB, it is important to review essential design parameters and principles of CFB combustors, which will be discussed in detail to include required data, heat balance and flowrates, operating versus transport velocity, kinetics and conversion (including the possible effect of the Bouduard reaction if carbon is present). Since the residence time in the riser and the cyclone efficiency determine the burnout of circulating fuel-particles, the UPM-CFB was subjected to a stimulus response technique using nickel oxide as tracer. Results illustrate the efficiency of the cyclone separation and the number of recycle loops for particles of a given size. Results will also be used to assess the cyclone operation and efficiency and to comment upon expected and measured carbon conversion. 相似文献
95.
The characterisation of flow through porous media is important for all solid–liquid separation and fluid transport realms.
The permeability of porous media can be anisotropic and furthermore, the extent of anisotropy can be increased as a result
of an applied compressive force. However, the understanding of how anisotropy develops is incomplete. An overview of research
on permeability anisotropy is given and an expression for predicting anisotropy as a function of void ratio is offered. The
two underlying assumptions of the proposed model are: flow in different directions occurs within the same network of pores
and deformation is primarily due to the compression of the particles in the direction of the applied force rather than due
to particle rearrangement. The assumption of network connectivity allows permeability anisotropy to be described as a function
of flow path tortuosity only. Results are presented for hydraulic anisotropy measured in lignite that has been upgraded by
a compression dewatering method known as mechanical thermal expression. The lignite permeability is shown to be up to eight
times greater in the direction perpendicular to compression, suggesting that the rate of dewatering could be significantly
increased by choosing the drainage to also be perpendicular to the direction of the applied compressive force. It is illustrated
that the proposed anisotropy model can be used to accurately predict the experimentally determined permeability anisotropy
ratios for lignite, as well as for other materials including sand, clay and kaolin. 相似文献
96.
97.
用系统工程学的观点, 重新认识矿山岩体工程的特点。建立矿山岩体工程稳定性的系统的概念。提出地质模型、设计模型、施工模型的构思, 使工程地质、设计、施工三者密切结合, 共同解决矿山岩体工程稳定问题。通过动态监测和信息反馈, 在工程施工的动态过程中不断地获得新的认识, 以便对工程实施做出新的决策。 相似文献
98.
Proper design of operations encountered in preparation, transport and employment of suspensions like coal slurries and coal-oil mixtures require an accurate knowledge of their rheological behaviour.Such concentrated suspensions generally exhibit non-Newtonian behaviour (shearthinning) which is more pronounced at higher coal concentrations. The nature of the dispersing medium influences the aggregation state of the disperse phase and, consequently, affects the stability and the rheology of the systems. In the present paper coal suspensions prepared with different dispersing media and covering a wide range in solid phase concentration are studied, by using a rotational coaxial cylinders viscometer.Different models have been taken into consideration for correlating experimental data. In particular, in order to describe the dependence of viscosity on shear rate and solid phase concentration, the suitability of the model suggested by Smith and Bruce is evaluated. Accordingly, the aggregation state of the disperse phase as well as its dependence on shear rate and dispersing medium can be estimated. 相似文献
99.
100.
Xiaofang Zhang Li Dong Juwei Zhang Yajun Tian Guangwen Xu 《Journal of Analytical and Applied Pyrolysis》2011,91(1):241-250
Simulating the conditions of pyrolytic topping in a fluidized bed reactor integrated into a CFB boiler, the study was devoted to the reaction fundamentals of coal pyrolysis in terms of the production characteristics of pyrolysis oil in fluidized bed reactors, including pyrolysis oil yield, required reaction time and the chemical species presented in the pyrolysis oil. The results demonstrated that the maximal pyrolysis oil yield occurred on conditions of 873 K, with a reaction time of 3 min and in a reaction atmosphere gas simulating the composition of pyrolysis gas. Adding H2 and CO2 into the reaction atmosphere decreased the pyrolysis oil yield, while the oil yield increased with increasing the CO and CH4 contents in the atmosphere. TG-FTIR analysis was conducted to reveal the effects of reaction atmosphere on the chemical species present in the pyrolysis oil. The results clarified that the pyrolysis oil yield reached its maximum when the simulated pyrolysis gas was the reaction atmosphere, but there were slightly fewer volatile matters in the pyrolysis oil than the oil generated in the N2 atmosphere. All of these results are expected not only to reveal the composition characteristics of the pyrolysis oil from different conditions of the coal topping process but also to optimize the pyrolysis conditions in terms of maximizing the light pyrolysis oil yield and quality. 相似文献