全文获取类型
收费全文 | 7490篇 |
免费 | 1204篇 |
国内免费 | 624篇 |
专业分类
电工技术 | 199篇 |
技术理论 | 1篇 |
综合类 | 759篇 |
化学工业 | 1028篇 |
金属工艺 | 93篇 |
机械仪表 | 340篇 |
建筑科学 | 368篇 |
矿业工程 | 64篇 |
能源动力 | 247篇 |
轻工业 | 88篇 |
水利工程 | 141篇 |
石油天然气 | 128篇 |
武器工业 | 83篇 |
无线电 | 829篇 |
一般工业技术 | 719篇 |
冶金工业 | 234篇 |
原子能技术 | 78篇 |
自动化技术 | 3919篇 |
出版年
2024年 | 24篇 |
2023年 | 115篇 |
2022年 | 184篇 |
2021年 | 245篇 |
2020年 | 250篇 |
2019年 | 269篇 |
2018年 | 244篇 |
2017年 | 298篇 |
2016年 | 312篇 |
2015年 | 353篇 |
2014年 | 459篇 |
2013年 | 554篇 |
2012年 | 529篇 |
2011年 | 554篇 |
2010年 | 428篇 |
2009年 | 456篇 |
2008年 | 451篇 |
2007年 | 536篇 |
2006年 | 390篇 |
2005年 | 367篇 |
2004年 | 332篇 |
2003年 | 262篇 |
2002年 | 226篇 |
2001年 | 198篇 |
2000年 | 147篇 |
1999年 | 139篇 |
1998年 | 108篇 |
1997年 | 75篇 |
1996年 | 88篇 |
1995年 | 82篇 |
1994年 | 75篇 |
1993年 | 52篇 |
1992年 | 53篇 |
1991年 | 47篇 |
1990年 | 32篇 |
1989年 | 36篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 25篇 |
1984年 | 34篇 |
1983年 | 33篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1980年 | 34篇 |
1979年 | 38篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1951年 | 6篇 |
排序方式: 共有9318条查询结果,搜索用时 46 毫秒
81.
Alexander Van-Brunt Patrick E. Farrell Charles W. Monroe 《American Institute of Chemical Engineers》2022,68(5):e17599
We present the Onsager–Stefan–Maxwell thermodiffusion equations, which account for the Soret and Dufour effects in multicomponent fluids. Unlike transport laws derived from kinetic theory, this framework preserves the structure of the isothermal Stefan–Maxwell equations, separating the thermodynamic forces that drive diffusion from the force that drives heat flow. The Onsager–Stefan–Maxwell transport-coefficient matrix is symmetric, and the second law of thermodynamics imbues it with simple spectral characteristics. This new approach allows for heat to be considered as a pseudo-species and proves equivalent to both the intuitive extension of Fick's law and the generalized Stefan–Maxwell equations popularized by Bird, Stewart, and Lightfoot. A general inversion process facilitates the unique formulation of flux-explicit transport equations relative to any choice of convective reference velocity. Stefan–Maxwell diffusivities and thermal diffusion factors are tabulated for gaseous mixtures containing helium, argon, neon, krypton, and xenon. The framework is deployed to perform numerical simulations of steady three-dimensional thermodiffusion in a ternary gas. 相似文献
82.
Shashank S. Tiwari Swapnil V. Ghatage Jyeshtharaj B. Joshi Bo Kong 《American Institute of Chemical Engineers》2022,68(8):e17725
Multifluid model (MFM) simulations have been carried out on liquid–solid fluidized beds (LSFB) consisting of binary and higher-order polydisperse particle mixtures. The role of particle–particle interactions was found to be as crucial as the drag force under laminar and homogenous LSFB flow regimes. The commonly used particle–particle closure models are designed for turbulent and heterogeneous gas–solid flow regimes and thus exhibit limited to no success when implemented for LSFB operating under laminar and homogenous conditions. A need is perceived to carry out direct numerical simulations of liquid–solid flows and extract data from them to develop rational closure terms to account for the physics of LSFB. Finally, a recommendation flow regime map signifying the performance of the MFM has been proposed. This map will act as a potential guideline to identify whether or not the bed expansion characteristics of a given polydisperse LSFB can be correctly simulated using MFM closures tested. 相似文献
83.
流体驱动旋转装备在能量转换及能量回收等过程中应用广泛。近年来,流体驱动旋转装备新结构不断涌现,其应用也得到了拓展,逐步与海水淡化、制冷、混合、测速等过程结合。在此发展过程中,计算流体力学为流体驱动旋转装备的设计优化提供了新途径。本文综述了流体驱动旋转装备在能源工程、化学工程等领域的应用,总结了流体驱动旋转装备数值模拟方法研究进展,对比了主动旋转及被动旋转两种模拟方法,指出被动旋转模拟在流体驱动旋转装备研究中的意义,展望了流体驱动旋转技术在超重力装备中的应用前景。 相似文献
84.
建立U形导流板换热器和扭转流换热器全截面周期模型,利用计算流体力学(CFD)方法对两种换热器壳程性能进行数值研究。相较于扭转流换热器,U形导流板换热器的壳程压降降低45.3%~47.5%,传热系数降低9.9%~13.5%,均匀性提高2.4%~4.0%,综合性能提高4.0%~14.6%。场协同结果表明,U形导流板换热器壳程流体速度与压力梯度的协同性优于扭转流换热器,而流体速度与温度梯度的协同性不如扭转流换热器。本文利用激光多普勒测速仪(LDV)验证了模拟方法准确性和模拟结果的可靠性;分析了U形导流板结构参数及布置方式对换热器壳程压降和传热性能的影响。结果表明,U形导流板的布置角度和布置方式对性能影响显著,导流板宽度和导流板间距的影响较小。 相似文献
85.
热失控是化工过程中常见的安全风险之一。在间歇釜式反应器中,桨叶的机械转动可以增强流体的循环流动、湍流强度、混合程度以及传热,进而有效防范热失控。防控效果与反应器结构和搅拌桨型密切相关。针对丙酸异丙酯酯化反应,采用计算流体力学模拟研究了桨型(Rushton桨、30o PBT桨及60o PBT桨)、转动方向和挡板对釜式反应器内温度演化的影响,从流动结构方面分析了原因。基于散度的失控判据比较了三种搅拌桨抑制热失控的能力,抑制能力为Rushton桨>30° PBTD桨>60° PBTD桨。本研究可为搅拌反应器热失控的优化设计提供一定的理论依据。 相似文献
86.
Xuesong Lu Xiaojiao Luo Warren A. Thompson Jeannie Z.Y. Tan M. Mercedes Maroto-Valer 《Frontiers of Chemical Science and Engineering》2022,16(7):1149
The production of solar fuels via the photoreduction of carbon dioxide to methane by titanium oxide is a promising process to control greenhouse gas emissions and provide alternative renewable fuels. Although several reaction mechanisms have been proposed, the detailed steps are still ambiguous, and the limiting factors are not well defined. To improve our understanding of the mechanisms of carbon dioxide photoreduction, a multiphysics model was developed using COMSOL. The novelty of this work is the computational fluid dynamic model combined with the novel carbon dioxide photoreduction intrinsic reaction kinetic model, which was built based on three-steps, namely gas adsorption, surface reactions and desorption, while the ultraviolet light intensity distribution was simulated by the Gaussian distribution model and Beer-Lambert model. The carbon dioxide photoreduction process conducted in a laboratory-scale reactor under different carbon dioxide and water moisture partial pressures was then modeled based on the intrinsic kinetic model. It was found that the simulation results for methane, carbon monoxide and hydrogen yield match the experiments in the concentration range of 10−4 mol·m–3 at the low carbon dioxide and water moisture partial pressure. Finally, the factors of adsorption site concentration, adsorption equilibrium constant, ultraviolet light intensity and temperature were evaluated. 相似文献
87.
88.
Kriksunov É. Z. Perel'muter A. V. Perel'muter M. A. Cementsov A. I. Fedorovskii V. G. 《Soil Mechanics and Foundation Engineering》2002,39(1):10-12
Soil Mechanics and Foundation Engineering - 相似文献
89.
90.