全文获取类型
收费全文 | 71035篇 |
免费 | 8344篇 |
国内免费 | 2839篇 |
专业分类
电工技术 | 4137篇 |
技术理论 | 5篇 |
综合类 | 5503篇 |
化学工业 | 16368篇 |
金属工艺 | 6080篇 |
机械仪表 | 3417篇 |
建筑科学 | 7222篇 |
矿业工程 | 1106篇 |
能源动力 | 10001篇 |
轻工业 | 3354篇 |
水利工程 | 979篇 |
石油天然气 | 2833篇 |
武器工业 | 474篇 |
无线电 | 3416篇 |
一般工业技术 | 8549篇 |
冶金工业 | 3984篇 |
原子能技术 | 1391篇 |
自动化技术 | 3399篇 |
出版年
2024年 | 324篇 |
2023年 | 1117篇 |
2022年 | 2014篇 |
2021年 | 2288篇 |
2020年 | 2379篇 |
2019年 | 2006篇 |
2018年 | 1800篇 |
2017年 | 2092篇 |
2016年 | 2427篇 |
2015年 | 2473篇 |
2014年 | 4122篇 |
2013年 | 4516篇 |
2012年 | 4855篇 |
2011年 | 5334篇 |
2010年 | 3959篇 |
2009年 | 4072篇 |
2008年 | 3429篇 |
2007年 | 4502篇 |
2006年 | 4106篇 |
2005年 | 3703篇 |
2004年 | 3138篇 |
2003年 | 2853篇 |
2002年 | 2548篇 |
2001年 | 2028篇 |
2000年 | 1729篇 |
1999年 | 1365篇 |
1998年 | 1164篇 |
1997年 | 1033篇 |
1996年 | 852篇 |
1995年 | 732篇 |
1994年 | 585篇 |
1993年 | 494篇 |
1992年 | 435篇 |
1991年 | 309篇 |
1990年 | 264篇 |
1989年 | 256篇 |
1988年 | 177篇 |
1987年 | 133篇 |
1986年 | 114篇 |
1985年 | 82篇 |
1984年 | 109篇 |
1983年 | 77篇 |
1982年 | 69篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 9篇 |
1977年 | 5篇 |
1966年 | 7篇 |
1959年 | 29篇 |
1951年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
801.
802.
基于气溶胶中PM2.5微细颗粒物拟流体特性,对气液交叉流阵列中PM2.5在气溶胶流体传热传质边界层内热泳和扩散泳运动进行拟传质机理分析,与跟随气体的对流传质相叠加,建立了气液交叉流阵列PM2.5热泳和扩散泳拟传质模型,并进行了实验检验。实验在固定对流条件下,考察了不同气液相温度差导致的热泳、不同气相湿度差导致的扩散泳和颗粒粒径等因素对气液交叉流阵列PM2.5拟传质系数的影响。实验数据统计值与模型表达趋势一致,在初始温差40℃、初始湿度0.118 kg/kg条件下,100排气液交叉流阵列PM2.5拟传质系数模型预测值为3.33×10-3 m/s、实验值为3.75×10-3 m/s。 相似文献
803.
This paper presents a mathematical model based on a three-phase theory, which is used to describe the mass and heat transfer between the gas and solids phases in a batch fluidised bed dryer. In the model, it is assumed that the dilute phase (i.e., bubble) is plug flow while the interstitial gas and the solid particles are considered as being perfectly mixed. The thermal conductivity of wet particles is modelled using a serial and parallel circuit. The moisture diffusion in wet particles was simulated using a numerical finite volume method. Applying a simplified lumped model to a single solid particle, the heat and mass transfer between the interstitial gas and solid phase is taken into account during the whole drying process as three drying rate periods: warming-up, constant rate and falling-rate. The effects of the process parameters, such as particle size, gas velocity, inlet gas temperature and relative humidity, on the moisture content of solids in the bed have been studied by numerical computation using this model. The results are in good agreement with experimental data of heat and mass transfer in fluidised bed dryers. The model will be employed for online simulation of a fluidised bed dryer and for online control. 相似文献
804.
工业过程中的废热排放造成了可用能的损失 ,又造成热污染和环境污染。针对一种利用热管回收废热的LiBr制冷机 ,采用柴油机烟气废热制冷实测后 ,对该系统的实测结果进行了火用分析 ,分析结果表明了这种新型废热LiBr制冷机有效利用了柴油机烟气余热 ,提高了系统的火用效率 相似文献
805.
Boundary layer equations for free convection heat transfer along a semi-infinite horizontal plate are derived by giving more importance to the energy equation. The equations are obtained for low Prandtl number and two separate polynomials are used to approximate the temperature and velocity profiles in these regions. The rate of heat transfer is compared with the available analytical and numerical results based on conventional boundary layer equations. 相似文献
806.
The effect of recycle on heat (and mass) transfer in concentric circular tubes has been investigated by finite difference methods. Theoretical results show that recycle can enhance the heat transfer rate for large Graetz numbers compared with that in an open tube (without an inner tube inserted and without recycle). Competition between a preheating effect and a residence-time effect can be used to explain the heat transfer behavior. The heat transfer rate can be further augmented, with nearly no increase in total pressure drop, by employing flow pattern B instead of flow pattern A. 相似文献
807.
Heat transfer characteristics for a falling turbulent liquid film flow over a fin are analyzed using the conjugate convection-conduction theory. Numerical results are obtained from a simultaneous solution of the energy equations of the fluid and the fin. Results are presented for the fin temperature distribution, dimensionless heat transfer coefficients, local heat fluxes, and fin efficiencies. 相似文献
808.
Efficacy of tertiary butylhydroquinone on the storage and heat stability of liquid canola shortening 总被引:1,自引:0,他引:1
Z. J. Hawrysh P. J. Shand C. Lin B. Tokarska R. T. Hardin 《Journal of the American Oil Chemists' Society》1990,67(9):585-590
The sensory (odor and flavor) and physicochemical characteristics of tertiary butylhydroquinone (TBHQ) treated and butylated
hydroxyanisole/toluene (BHA/BHT) treated liquid canola shortenings, subjected to accelerated storage (Schaal oven test at
65°C) and deep fat heating (at 185°C), were determined. Data for the Schaal oven test indicate that TBHQ was effective in
retarding oxidative rancidity in liquid canola shortenings. However, addition of the commonly used mixture of BHA/BHT to canola
shortenings resulted in only a slight decrease in oxidation during schaal oven storage. The results obtained from deep fat
heating of canola liquid shortening show that neither TBHQ nor BHA/BHT was effective in enhancing oxidative and thermal stability
of this product. 相似文献
809.
瓷质砖湿坯对流干燥过程的传热传质研究 总被引:3,自引:0,他引:3
引用建立于Whitaker的体积平均方程和Darcy定律基础止的多孔介质内部热质传递的等效耦合扩散模型,寻出一组关于液体饱和度、温度和气相压力的新支配方程,应用该方程组对瓷质砖坯体干燥过程进行了数值分析和实验测定。在平均含湿饱和度的变化方面,数值解与实验结果十分吻合。还改变影响坯体干燥过程的一些因素进行计算机模拟计算,通过改变这些因素的大小来考察计算结果,以期获得某些定性或定量的结论,从而用以指导实际生产过程。 相似文献
810.