首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   589篇
  免费   21篇
  国内免费   2篇
电工技术   3篇
化学工业   74篇
金属工艺   10篇
机械仪表   31篇
建筑科学   23篇
矿业工程   1篇
能源动力   30篇
轻工业   49篇
水利工程   4篇
石油天然气   6篇
无线电   59篇
一般工业技术   89篇
冶金工业   170篇
原子能技术   3篇
自动化技术   60篇
  2023年   3篇
  2022年   4篇
  2021年   9篇
  2020年   7篇
  2019年   12篇
  2018年   22篇
  2017年   12篇
  2016年   20篇
  2015年   15篇
  2014年   14篇
  2013年   40篇
  2012年   19篇
  2011年   21篇
  2010年   20篇
  2009年   24篇
  2008年   27篇
  2007年   20篇
  2006年   16篇
  2005年   16篇
  2004年   16篇
  2003年   11篇
  2002年   10篇
  2001年   3篇
  2000年   9篇
  1999年   7篇
  1998年   34篇
  1997年   18篇
  1996年   14篇
  1995年   18篇
  1994年   10篇
  1993年   18篇
  1992年   10篇
  1991年   6篇
  1990年   3篇
  1989年   6篇
  1988年   7篇
  1987年   7篇
  1986年   6篇
  1985年   5篇
  1984年   3篇
  1983年   3篇
  1982年   6篇
  1981年   5篇
  1980年   5篇
  1978年   7篇
  1977年   7篇
  1976年   9篇
  1974年   3篇
  1972年   3篇
  1957年   3篇
排序方式: 共有612条查询结果,搜索用时 31 毫秒
1.
2.
Ten wells (EW-4, EW-5, EW-6, EW-7, EW-8, EW-9, EW-10, EW-12, EW-13 and EW-15) were interpreted using the composite well logs, data of core analysis, gamma-ray logs, formation micro-imager logs (FMI), and 3D seismic data in SEGY format to understand the stratigraphy of the onshore, Nile Delta, Egypt.The amplitude analysis of 3-D seismic horizon slice of Lower Abu Madi rock unit together with the lithostratigraphic correlation through the study area depending on the gamma-ray log “HSGR” (left to right increasing), and the identification of type of bed geometry, nature of bed contacts, type of the sedimentary structures and the dominant formative paleocurrents by using some available borehole micro-resistivity images (FMI) and core photos. All of these techniques are used together to define the different depositional facies and depositional environment of the Messinian clastics (Lower Abu Madi rock unit), which is considered to be the main reservoir in the El-Wastani gas field, onshore Nile Delta, Egypt.The present study of depositional pattern of the Upper Miocene clastics reservoir (Lower Abu Madi rock unit) revealed that it is represented by high sinuous meandering channels or paleo-valley and three types of fluvial facies were defined; channel fill, channel margin, and floodplain basin.  相似文献   
3.
Wireless Networks - The Internet of Things (IoT) technology has recently experienced popularity and growth in every facet of life, and it has been applied to every industry in recent years. The...  相似文献   
4.
Chemical engineering systems often involve a functional porous medium, such as in catalyzed reactive flows, fluid purifiers, and chromatographic separations. Ideally, the flow rates throughout the porous medium are uniform, and all portions of the medium contribute efficiently to its function. The permeability is a property of a porous medium that depends on pore geometry and relates flow rate to pressure drop. Additive manufacturing techniques raise the possibilities that permeability can be arbitrarily specified in three dimensions, and that a broader range of permeabilities can be achieved than by traditional manufacturing methods. Using numerical optimization methods, we show that designs with spatially varying permeability can achieve greater flow uniformity than designs with uniform permeability. We consider geometries involving hemispherical regions that distribute flow, as in many glass chromatography columns. By several measures, significant improvements in flow uniformity can be obtained by modifying permeability only near the inlet and outlet.  相似文献   
5.
Synthesis of carboxymethyl cellulose‐g‐methacrylic acid/acrylamide Poly(CMC/MAAc:AAm) hydrogel was carried out using direct radiation copolymerization technique at ambient temperature. The gel (%) increased with increasing the content of AAm till level off at Poly(CMC/MAAc:AAm) (1/50:50 wt%) hydrogel and the swelling behavior found to be increased with increasing MAAc content in the hydrogel composition up to Poly(CMC/MAAc:AAm) (1/60:40 wt%). The grafting yield, grafting ratio, swelling behavior, and the thermal stability of Poly(CMC/MAAc:AAm) binary system are higher than those reported in our previous study by the same author which described the individual grafting of acrylamide (AAm) and methacrylic acid (MAAc) with different concentration onto carboxymethyl cellulose (CMC) using direct radiation grafting technique. The swelling kinetics and diffusion mechanism indicate that the water penetration obey non‐Fickian transport mechanism. The characterization of the prepared hydrogel was evaluated using Fourier transform infrared, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The analyses by different analytical tools confirmed the successful grafting of both MAAc and AAm onto CMC. The adsorption capacity of Poly(CMC/MAAc:AAm) (1/60:40 wt%) hydrogel toward metal ions such as Cu+2 and Co+2, dyes such as acid blue dye and methyl green have been investigated. J. VINYL ADDIT. TECHNOL., 25:E35–E43, 2019. © 2017 Society of Plastics Engineers  相似文献   
6.
This research presents a discrete-time transmission line model based on the propagation of travelling waves. In this approach, the transmission line is emulated by means of many interconnected unit delay cells implemented with switched-capacitor (SC) circuits. The accuracy and limitations of this method is compared to existing transconductance–capacitor solutions and is evaluated in the frame of a novel power network fault location method based on the electromagnetic time-reversal principle. The impact of the non-ideal effects associated to analog CMOS SC circuits, such as amplifier finite gain, offset and switch charge injection is evaluated in the same context. A possible application of the model for the simulation of interconnected or multi-conductor lines is also discussed. After an AMS 0.35 µm process implementation, it is shown that the present method allows a fault location within 1% resolution and is a hundred times faster than nowadays digital solutions. This speed improvement allows a fault location within 160 ms, making thus real-time applications realistic.  相似文献   
7.
Ma  Cui-Xia  Song  Jian-Cheng  Zhu  Qian  Maher  Kevin  Huang  Ze-Yuan  Wang  Hong-An 《计算机科学技术学报》2020,35(3):576-591
Journal of Computer Science and Technology - Emotion plays a crucial role in gratifying users’ needs during their experience of movies and TV series, and may be underutilized as a framework...  相似文献   
8.
In compressive sampling theory, the least absolute shrinkage and selection operator (LASSO) is a representative problem. Nevertheless, the non-differentiable constraint impedes the use of Lagrange programming neural networks (LPNNs). We present in this article the -LPNN model, a novel algorithm that tackles the LASSO minimization together with the underlying theory support. First, we design a sequence of smooth constrained optimization problems, by introducing a convenient differentiable approximation to the non-differentiable -norm constraint. Next, we prove that the optimal solutions of the regularized intermediate problems converge to the optimal sparse signal for the LASSO. Then, for every regularized problem from the sequence, the -LPNN dynamic model is derived, and the asymptotic stability of its equilibrium state is established as well. Finally, numerical simulations are carried out to compare the performance of the proposed -LPNN algorithm with both the LASSO-LPNN model and a standard digital method.  相似文献   
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号