全文获取类型
收费全文 | 6931篇 |
免费 | 663篇 |
国内免费 | 283篇 |
专业分类
电工技术 | 164篇 |
综合类 | 488篇 |
化学工业 | 2158篇 |
金属工艺 | 172篇 |
机械仪表 | 433篇 |
建筑科学 | 1333篇 |
矿业工程 | 214篇 |
能源动力 | 283篇 |
轻工业 | 280篇 |
水利工程 | 300篇 |
石油天然气 | 257篇 |
武器工业 | 47篇 |
无线电 | 447篇 |
一般工业技术 | 517篇 |
冶金工业 | 398篇 |
原子能技术 | 126篇 |
自动化技术 | 260篇 |
出版年
2024年 | 22篇 |
2023年 | 84篇 |
2022年 | 149篇 |
2021年 | 182篇 |
2020年 | 180篇 |
2019年 | 162篇 |
2018年 | 171篇 |
2017年 | 176篇 |
2016年 | 225篇 |
2015年 | 218篇 |
2014年 | 401篇 |
2013年 | 488篇 |
2012年 | 395篇 |
2011年 | 465篇 |
2010年 | 387篇 |
2009年 | 379篇 |
2008年 | 378篇 |
2007年 | 420篇 |
2006年 | 384篇 |
2005年 | 322篇 |
2004年 | 288篇 |
2003年 | 273篇 |
2002年 | 255篇 |
2001年 | 226篇 |
2000年 | 216篇 |
1999年 | 174篇 |
1998年 | 146篇 |
1997年 | 137篇 |
1996年 | 77篇 |
1995年 | 82篇 |
1994年 | 87篇 |
1993年 | 65篇 |
1992年 | 65篇 |
1991年 | 31篇 |
1990年 | 30篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1951年 | 7篇 |
排序方式: 共有7877条查询结果,搜索用时 9 毫秒
41.
从反应注射成型过程对混合器的结构设计、操作条件等的要求出发,对碰撞式混合器的设计和使用应注意的问题进行了分析探讨,并提出了相应的解决办法和处理措施。 相似文献
42.
含白炭黑胎面胶的混炼 总被引:1,自引:0,他引:1
以白炭黑作填充剂的轮胎具有滚动阻力低等优点。但是白炭黑在橡胶中不易分散。介绍了为提高含白炭黑的胎面胶的混炼质量,加速白炭黑在轮胎中的推广应用而采取的原材料、混炼工艺和混炼设备。 相似文献
43.
A characterisation of three commonly used impellers was made in this study by measuring local mean velocities and the fluctuations of these velocities with the LDV technique. The data was used to estimate volumetric flow, velocity fluctuations and turbulent intensity in the impeller region of the tank. The impellers investigated were a high flow impeller, a pitched blade turbine and a Rushton turbine. The cylindrical vessel used was made of Perspex, had a dished bottom (DIN 28013), was equipped with four baffles and had an inner diameter of 0.45 m. It was found that the bulk velocities could be scaled with the tip-speed of the impeller (ND). The flow rate at constant impeller speed increased in the order high flow impeller — Rushton turbine — pitched blade turbine. The corresponding order for the turbulence fluctuation is: high flow impeller — pitched blade turbine — Rushton turbine. The velocity profile of the flow out from the high flow impeller was furthermore, not as smooth as could be expected. 相似文献
44.
Radial gas mixing in a fluidized bed was studied using response surface methodology (RSM), which enables effect examinations of parameters with a moderate number of experiments. All experiments were conducted in a 0.29-m ID fluidized-bed cold model. The gas dispersion process within the bed is described using the dispersed plug flow model. Pure carbon dioxide was used as the tracer gas, continuously injected into the center of the bed by a point source. The downstream radial tracer concentration profile was measured using a gas chromatograph.The radial gas dispersion coefficient, Dr, was well correlated with operating parameters and the particle and gas properties: (U−Umf)/Umf, Hs/db, φd, and Ar, with a determination coefficient R2 of 0.966. Effect test indicates that the dimensionless characteristic velocity, (U−Umf)/Umf, has the most significant influence on Dr, while the static bed height to bed diameter ratio, Hs/db, is less remarkable. The interactions of (U−Umf)/Umf with the distributor open-area ratio, φd, and with the Archimedes number, Ar, both play important roles. An evolutive response surface model was proposed to describe the radial gas mixing in the bubbling/slugging fluidization regimes. 相似文献
45.
High‐abrasion furnace black (HAF, grade N330)–filled powdered styrene butadiene rubber [P(SBR/HAF)] was prepared and the particle size distribution, mixing behavior in a laboratory mixer, and mechanical properties of P(SBR/HAF) were studied. A carbon black–rubber latex coagulation method was developed for preparing carbon black–filled free‐flowing, noncontact staining SBR powders, with particle diameter less than 0.9 mm, under the following conditions: carbon black content > 40 phr, emulsifier/carbon black ratio > 0.02, and coating resin content > 2.5 phr. Over the experimental range, the mixing torque τα of P(SBR/HAF) was not as sensitive to carbon black content and mixing temperature as that of HAF‐filled bale SBR (SBR/HAF), whereas the temperature build‐up ΔT showed little dependency on carbon black content. Compared with SBR/HAF, P(SBR/HAF) showed a 20–30% mixing energy reduction with high carbon black content (>30 phr), which confers to powdered SBR good prospects for internal mixing. Carbon black and the rubber matrix formed a macroscopic homogenization in P(SBR/HAF), and the incorporation step is not obvious in the internal mixing processing results in these special mixing behaviors of P(SBR/HAF). A novel mixing model of carbon black–filled powdered rubber, during the mixing process in an internal mixer, was proposed based on the special mixing behaviors. P(SBR/HAF) vulcanizate showed better mechanical properties than those of SBR/HAF, dependent primarily on the absence of free carbon black and a fine dispersion of filler on the rubber matrix attributed to the proper preparation conditions of noncontact staining carbon black–filled powdered SBR. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2494–2508, 2004 相似文献
46.
The effects of the non-Newtonian properties on the effective deformation rate, mixing and circulation times and flow behaviour have been investigated in the transition flow regime of mixing systems. Based on the equivalent Couette flow, three models are proposed and are shown to predict similar and drastic increases of the effective deformation rate with the impeller rotational speed in the transition regime. The predictions are shown to fit very well data obtained for various non-Newtonian fluids mixed with helical ribbon agitators, and with literature data for anchor, blade turbine and flat disc agitators. The elasticity along with shear-thinning properties appear to have slight effects on the dimensionless mixing and circulation times in the transition regime, whereas their effects in the laminar regime are quite drastic, as reported by others. 相似文献
47.
Isaias Ochoa 《Powder Technology》2005,153(2):108-118
The effects of the lubricant physical properties on the processing of polytetrafluoroethylene (PTFE) fine powder resins are studied. Lubricants having different surface tension and viscosity were used; the two properties changed independently. These effects were studied by using dies of various contraction angle and reduction ratio for resins having a variety of molecular architecture. It was found that the wettability (surface tension) of the lubricant strongly affects the pressure needed to extrude the PTFE pastes. The viscosity of the lubricant was also found to play a significant role in the process since a lubricant with a low viscosity causes the paste to be extruded at a lower pressure. These effects of the physical properties on the extrusion pressure influence significantly the mechanical properties of the final extrudates. The latter are functions of the degree of fibrillation, which is significantly influenced by the wettability and viscosity of lubricants. Finally, the effects of die geometry on extrusion pressure and mechanical properties of extrudates were also assessed in order to determine the geometrical characteristics and operation conditions for the optimization of the process. 相似文献
48.
49.
50.
High‐pressure vapour‐liquid equilibria for binary and ternary high polar and asymmetric systems are calculated using the Peng‐Robinson‐Stryjek‐Vera equation of state coupled with the Twu‐Coon (TWMR), the Orbey‐Sandler (OSMR) and the Wong‐Sandler (WSMR) mixing rules. Modified UNIFAC model is used for determining the activity coefficient and excess Gibbs free energy. The calculated results are compared with the experimental data and good agreement is observed. The average absolute deviation percents (AAD%)s indicated that the WSMR has less AAD% than other mixing rules in most of cases. 相似文献