全文获取类型
收费全文 | 10036篇 |
免费 | 922篇 |
国内免费 | 279篇 |
专业分类
电工技术 | 104篇 |
综合类 | 1136篇 |
化学工业 | 2292篇 |
金属工艺 | 134篇 |
机械仪表 | 247篇 |
建筑科学 | 3930篇 |
矿业工程 | 757篇 |
能源动力 | 102篇 |
轻工业 | 551篇 |
水利工程 | 155篇 |
石油天然气 | 484篇 |
武器工业 | 12篇 |
无线电 | 109篇 |
一般工业技术 | 595篇 |
冶金工业 | 233篇 |
原子能技术 | 131篇 |
自动化技术 | 265篇 |
出版年
2024年 | 22篇 |
2023年 | 109篇 |
2022年 | 201篇 |
2021年 | 283篇 |
2020年 | 270篇 |
2019年 | 240篇 |
2018年 | 220篇 |
2017年 | 304篇 |
2016年 | 329篇 |
2015年 | 325篇 |
2014年 | 576篇 |
2013年 | 670篇 |
2012年 | 792篇 |
2011年 | 800篇 |
2010年 | 549篇 |
2009年 | 567篇 |
2008年 | 518篇 |
2007年 | 626篇 |
2006年 | 568篇 |
2005年 | 495篇 |
2004年 | 398篇 |
2003年 | 352篇 |
2002年 | 291篇 |
2001年 | 270篇 |
2000年 | 225篇 |
1999年 | 198篇 |
1998年 | 153篇 |
1997年 | 256篇 |
1996年 | 112篇 |
1995年 | 102篇 |
1994年 | 66篇 |
1993年 | 57篇 |
1992年 | 64篇 |
1991年 | 45篇 |
1990年 | 38篇 |
1989年 | 40篇 |
1988年 | 36篇 |
1987年 | 20篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
J.F. Rejl T. Moucha E. Prokopová L. Valenz F. Hovorka 《Chemical engineering science》2006,61(18):6096-6108
Volumetric mass transfer coefficients in liquid and vapour phases in distillation column were measured by the method consisting of a fitting of the concentration profile of liquid phase along the column obtained by the integration of a differential model to the experimental one. The mathematical model of distillation process includes mass and energy balances and the heat and mass transfer equations. The film model flux expressions with the convective transport contributions have been considered in the transfer equations. Vapour and liquid phases are supposed to be at their saturated temperatures along the column. Effect of changes of phase flows and physical properties of phases on the mass transfer coefficients along the column and non-ideal thermodynamic behaviour of the liquid phase have been taken into account. The concentration profiles of liquid phase are measured in the binary distillation of the ethanol-water and methanol-ethanol systems at total reflux on metal Pall Rings and Intalox saddles 25 mm in the column with diameter of 150 mm. The distillation mass transfer coefficients obtained by the fitting procedure are compared with those calculated from absorption data using Onda's, Billet's and Linek's correlations. The distillation heat transfer coefficients calculated from the model assuming saturated temperatures in both phases are compared with those calculated from the Chilton-Colburn and penetration model analogy between mass and heat transfer. The results have confirmed an agreement neither between distillation and from absorption correlations calculated mass transfer coefficients nor between analogy and from enthalpy balance calculated heat transfer coefficients. Also the concentration profiles obtained by the integration of the differential model of the distillation column using the coefficients from absorption correlation have differed from the experimental profiles considerably. 相似文献
43.
44.
This paper presents a comparative study how reactor configuration, sludge loading and air flowrate affect flow regimes, hydrodynamics, floc size distribution and sludge solids-liquid separation properties. Three reactor configurations were studied in bench scale activated sludge bubble column reactor (BCR), air-lift reactor (ALR) and aerated stirred reactor (ASR). The ASR demonstrated the highest capacity of gas holdup and resistance, and homogeneity in flow regimes and shearing forces, resulting in producing large numbers of small and compact flocs. The fluid dynamics in the ALR created regularly directed recirculation forces to enhance the gas holdup and sludge flocculation. The BCR distributed a high turbulent flow regime and non-homogeneity in gas holdup and mixing, and generated large numbers of larger and looser flocs. The sludge size distributions, compressibility and settleability were significantly influenced by the reactor configurations associated with the flow regimes and hydrodynamics. 相似文献
45.
The transport of gellan gum microbeads as potential cell carriers was investigated in horizontal columns packed with different grain size classes of gravel (2–16 mm) and sand (0.25–2 mm). A suspension of microbeads was pulsed into each column for 6 h, followed by injection of water for 42 h. In general, the total amount of microbeads travelling across a given section of the column increased with injection time but decreased towards the column outlet, varying as a direct function of grain size. The results of this study demonstrate the feasibility of the transport of gellan gum microbeads through medium sand to medium gravel across distances up to 110 cm. 相似文献
46.
针对钢骨混凝土L形柱,提出了一种新型的钢骨形式.为了掌握该构件的受力特性,通过ANSYS软件,对腹板开洞率、配钢率、加载角、偏心距等影响因素进行理论分析.结果表明,在相对偏心距较大的情况下构件承载力会急剧下降,而且存在不利荷载角的问题;腹板开洞能有效地减少钢骨与混凝土之间的滑移,但对承载力的削弱有限,并就该构件的最佳配钢率提出建议. 相似文献
47.
A one‐dimensional steady‐state model is developed for the prediction of axial variation of the gas holdup in flotation column froths. Froth is considered as an inverse fluidized bed of bubbles and hence the frictional pressure gradient is obtained based on the energy balance. Pressure gradient can also be obtained from the Ergun equation with adjustable constants. The model correctly captures the effect of superficial gas velocity, superficial liquid velocity and bubble diameter on the variation of the gas holdup along the froth height. The predictions of the model are in agreement with the experimental data from the literature. 相似文献
48.
Acicular goethite particles were synthesized by oxidation of an alkaline suspension of ferrous hydroxide using a bubble column with draft tubes of different diameters at a constant temperature of 40°C. The oxidation rate increased with decreasing draft tube diameter. The mean size based on the major axis of acicular particle decreased with increasing oxidation rate and decreasing draft tube diameter. The major axis was found to grow preferentially compared with the minor axis. The mean size of major axis was correlated well to the modified reaction rate defined as a product of the reaction rate per unit volume of the reactor multiplied by the ratio of the column diameter to the draft tube diameter, irrespective of the draft tube diameter. 相似文献
49.
50.
通过对钻孔以及强干扰区进行参数试验,确定了发射边框、发射频率、发射电流、采样延迟、高压线影响等施工布置参数;结合野外实测数据和钻孔测井资料,进行数据处理和反演,得出采区内的煤系地层与上下围岩有着明显的电性差异;采区北部富水性相对较强,中部和南部富水性相对较弱,F66断层和X26、X35、X79陷落柱是各煤层和奥灰岩的垂向导水通道。 相似文献