全文获取类型
收费全文 | 340篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
综合类 | 11篇 |
化学工业 | 120篇 |
金属工艺 | 2篇 |
机械仪表 | 3篇 |
建筑科学 | 3篇 |
矿业工程 | 7篇 |
能源动力 | 24篇 |
轻工业 | 5篇 |
水利工程 | 5篇 |
石油天然气 | 56篇 |
无线电 | 24篇 |
一般工业技术 | 54篇 |
冶金工业 | 2篇 |
原子能技术 | 3篇 |
自动化技术 | 18篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 25篇 |
2012年 | 9篇 |
2011年 | 24篇 |
2010年 | 18篇 |
2009年 | 21篇 |
2008年 | 19篇 |
2007年 | 18篇 |
2006年 | 16篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
排序方式: 共有344条查询结果,搜索用时 15 毫秒
11.
���������IPR���̵����� 总被引:6,自引:0,他引:6
对比了Mishra&.Caudle相关式、二次式和指数式三类无因次IPR方程的处理方法、性能特点和无因次采气指数。重点讨论了二次式特征参数α的物理意义及其影响因素。利用陕8井的四点试井数据进行了实例分析,指出了经验相关式和统计参数对于单点产能测试的局限性。 相似文献
12.
具有井筒相分离和层间窜流的层状油藏渗流井底压力精确解 总被引:6,自引:3,他引:6
关于具有窜流的多层油藏井底压力解,国内外有不少学者进行了研究,D.Bourdet提出的双渗模型最具实用性,但该模型在表皮系数为负时,数值计算极不稳定,应用受到限制,本文首次用有效井径概念,导出了一个数值计算相当稳定的双渗模型,另外还考虑了井筒相分离影响,本模型解大大扩大了Bourdet模型的应用范围。 相似文献
13.
Complex permittivity and related AC conductivity measurements in the frequency range between 10−4 and 107 Hz are presented for composites of polycarbonate (PC) filled with different amounts of multiwalled carbon nanotubes (MWNT) varying in the range between 0.5 and 5 wt%. The composites were obtained by diluting a PC based masterbatch containing 15 wt% MWNT by melt mixing using a Micro Compounder. From DC conductivity measurements it was found that for samples processed at a mixing screw speed of 150 rpm for 5 min, the percolation occurs at a threshold concentration (pc) between 1.0 and 1.5 wt% MWNT. For concentrations of MWNT near the percolation threshold, the processing conditions (screw speed and mixing time) were varied. The differences in the dispersion of the MWNT in the PC matrix could be detected in the complex permittivity and AC conductivity spectra, and have been explained by changes in pc. The AC conductivity and permittivity spectra are discussed in terms of charge carrier diffusion on percolation clusters and resistor-capacitor composites. 相似文献
14.
Luis A. Segura 《Drying Technology》2013,31(9-11):2007-2019
Abstract Simulation results of pore-level drying of non-hygroscopic, non-rigid, liquid-wet porous media are presented. Two- and three-dimensional pore networks represent pore spaces. Two kinds of mechanisms are considered: evaporation and hydraulic flow. The process is considered under isothermal conditions. Capillary forces thus dominate over viscous forces and the drying is considered as a modified form of invasion percolation. Liquid in pore corners allows for hydraulic connection throughout the network. During drying, liquid is replaced by vapor by two fundamental mechanisms: evaporation and pressure gradient–driven liquid flow. The development of capillary pressure as menisci turn concave induces shrinkage of the matrix, which contributes to the pressure gradient that drives liquid toward the surface of the network. Using Monte Carlo simulation, we find evaporation and drainage times; the shortest calculated indicates the controlling mechanism. Here we report distributions of liquid and vapor as drying time advances. For the calculation of transport properties, details of pore space and displacement are subsumed in pore conductances. Solving for the pressure field in each phase, vapor and liquid, we find a single effective conductance for each phase as a function of liquid saturation. Along with the effective conductance for the liquid-saturated network, the relative permeability of liquid and diffusivity of vapor are calculated. 相似文献
15.
Cs. Mészáros Á. Bálint I. Kirschner K. Gottschalk I. Farkas 《Drying Technology》2013,31(7-8):1297-1304
A twofold refinement of the basic mathematical model for describing a coupled heat and mass transfer taking place in porous media is presented. The common application of irreversible thermodynamics and fluctuation theory of phase transitions is proposed for calculating the moisture level and temperature. Instead of parabolic partial differential equations, hyperbolic type partial differential equations are used. The relaxation time constants, whose percolation state-dependence is also taken into account, are incorporated into this formalism. Some possible new research domains in mathematical and statistical physics are also indicated. 相似文献
16.
17.
The polyamide-6/attapulgite nanocomposites were prepared via an in situ polymerization route with attapulgites pre-modified with cetyltrimethylammonium bromide (CTAB) and toluene-2,4-diisocyanate (TDI). Morphology observation showed that the exfoliated attapulgite fibers were well dispersed in the polyamide-6 matrix on a nanometer scale and formed a percolation network structure. The rheological behaviors of such polymer/fibrous clay nanocompostie samples were investigated by an ARES rheometer with parallel plate geometry. The storage moduli (G′), loss moduli (G″), and dynamic viscosities of these samples increased monotonically with attapulgite content at low frequencies. The presence of attapulgites caused these nanocomposite melts to have solid-like behaviors and slower relaxation. This behavior can be explained in terms of the development of a grafting-percolated fibrous-silicate network structure. Monte Carlo simulations were performed to determine the critical threshold for attapulgites fibers in 3D. The calculated critical threshold from simulations fitted the results of our rheological experiments very well. 相似文献
18.
Solubilization of water and aqueous NaCl in mixed reverse micelles (RMs) comprising sodium bis(2‐ethylhexyl) sulfosuccinate (AOT), and polyoxyethylene (20) sorbitan trioleate or polyoxyethylene (20) sorbitan monooleate has been studied at different compositions (Xnonionic = 0–1.0) at a total surfactant concentration, ST = 0.10 × 103 mol m?3 in biocompatible oils of different chemical structures; viz., ethyl oleate (EO), isopropyl myristate (IPM) and isopropyl palmitate (IPP) at 303 K. The enhancement in water solubilization (i.e., synergism) has been evidenced by the addition of nonionic surfactant to dioctyl sulfosuccinate/oil(s)/water systems. Addition of NaCl in these systems at different Xnonionic enhances their solubilization capacities further until a maximum, ωNaCl,max is reached. ωNaCl,max and [NaCl]max (concentration at which maximization of NaCl solubilization occurs) depend on type of nonionic surfactant, its content (Xnonionic) and oil. A new solubilization efficiency parameter (SP*water or SP*NaCl) has been proposed to compare solubilization phenomena in these oils. The energetic parameters of the desolubilization process of water or aqueous NaCl in single and mixed RMs have been estimated. Energetically, the water dissolution process in oil has been found to be more exothermic as well as more organized in IPP. Overall, the dissolution of water and aqueous NaCl in mixed RMs is entropically driven process. Conductance behavior of these systems in the presence of NaCl has been investigated under different [NaCl] at 303 K. An attempt has been made to give an insight to the mechanism of solubilization phenomena, percolation in conductance and microstructures vis‐à‐vis role of biocompatible oils in these systems. 相似文献
19.
油井酸压后三维渗流动态预测 总被引:5,自引:0,他引:5
本文综述考虑了影响酸压裂缝导流能力的诸因素:生产压降变化、非达西效应、油藏污染、裂缝几何尺寸、和导流能力沿缝变化等;推导并建立了三维酸压油井生产动态预测模型。 相似文献
20.
王建国 《深圳大学学报(理工版)》1990,(Z1)
本文介绍了研究无规凝聚体系的重要理论工具——分形及渗流理论的基本原理,并举例分析评述了分形及渗流在材料科学中的应用. 相似文献