全文获取类型
收费全文 | 7501篇 |
免费 | 568篇 |
国内免费 | 127篇 |
专业分类
电工技术 | 237篇 |
综合类 | 130篇 |
化学工业 | 1643篇 |
金属工艺 | 300篇 |
机械仪表 | 461篇 |
建筑科学 | 197篇 |
矿业工程 | 41篇 |
能源动力 | 372篇 |
轻工业 | 590篇 |
水利工程 | 55篇 |
石油天然气 | 46篇 |
武器工业 | 9篇 |
无线电 | 1243篇 |
一般工业技术 | 1637篇 |
冶金工业 | 354篇 |
原子能技术 | 81篇 |
自动化技术 | 800篇 |
出版年
2024年 | 12篇 |
2023年 | 92篇 |
2022年 | 126篇 |
2021年 | 206篇 |
2020年 | 199篇 |
2019年 | 188篇 |
2018年 | 226篇 |
2017年 | 252篇 |
2016年 | 261篇 |
2015年 | 220篇 |
2014年 | 333篇 |
2013年 | 434篇 |
2012年 | 521篇 |
2011年 | 630篇 |
2010年 | 446篇 |
2009年 | 482篇 |
2008年 | 472篇 |
2007年 | 391篇 |
2006年 | 309篇 |
2005年 | 300篇 |
2004年 | 253篇 |
2003年 | 256篇 |
2002年 | 277篇 |
2001年 | 227篇 |
2000年 | 175篇 |
1999年 | 136篇 |
1998年 | 156篇 |
1997年 | 133篇 |
1996年 | 96篇 |
1995年 | 82篇 |
1994年 | 49篇 |
1993年 | 50篇 |
1992年 | 29篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1974年 | 2篇 |
排序方式: 共有8196条查询结果,搜索用时 46 毫秒
991.
992.
993.
994.
995.
Piezoelectric cable is a commercial electronic sensor that incorporates the piezoelectric polymer polyvinylidene fluoride. This paper investigated a potential application of piezoelectric cable for energy harvesting. A method for testing the electrical output using the tensile load was developed and used to determine the output properties of the cable. A design for a piezoelectric cable fiber composite is presented, along with recommendations for potential applications and further research. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
996.
Kim Ye Jin Lee Jong Un Kim Sang-Hoon Yoon Jonghun Kim Young Min Park Sung Hyuk 《Metals and Materials International》2019,25(6):1541-1547
Metals and Materials International - This study demonstrates that the size of an individual grain in a rolled AZ31 alloy is significantly related to the crystallographic orientation of the grain... 相似文献
997.
在醇酸涂料中的纳米TiO2分散性及涂层耐磨性 总被引:2,自引:1,他引:2
在制备涂料中,颜料的分散是非常重要的,本文选择了一种非离子型的表面活性剂作为纳米TiO2在醇酸涂料中的分散剂,用激光粒度仪得到了涂料体系中的TiO2的粒度分布曲线.并结合TEM照片观察到了在有分散剂和没有分散剂时,纳米粉TiO2的分散状态.同时比较了含有不同含量TiO2(mass%)及含有普通钛白粉的涂层耐磨性,结果表明,有4%的纳米TiO2涂层耐磨性最好.
相似文献
998.
O. A. EI-Samni Hyun Sik Yoon Ho Hwan Chun 《Journal of Mechanical Science and Technology》2005,19(9):1801-1810
The effect of longitudinal thin rectangular riblets aligned with the flow direction on turbulent channel flow has been investigated
using direct numerical simulation. The thin riblets have been modeled using the immersed boundary method (IBM) where the velocities
at only one set of vertical nodes at the riblets positions are enforced to be zeros. Different spacings, ranging between 11
and 43 wall units, have been simulated aiming at getting the optimum spacing corresponding to the maximum drag reduction while
keeping the height/spacing ratio at 0.5. Reynolds number based on the friction velocityuτ and the channel half depth δ is set to 150. The flow is driven by adjusted pressure gradient so that the mass flow rate is
kept constant in all the simulations. This study shows similar trend of the drag ratio to that of the experiments at the different
spacings. Also, this research provides an optimum spacing of around 17 wall units leading to maximum drag reduction as experimental
data. Explanation of drag increasing/ decreasing mechanism is highlighted. 相似文献
999.
Yang -Hann Kim Soo Hyun Kim Byoung Duk Lim Yoon Keun Kwak 《Journal of Mechanical Science and Technology》1988,2(2):125-132
For the measurement of transmission loss of the silencers which have mean flow, the noise levels of signals depicted by microphone
usually prohibit accurate measurements of the transmission loss. To overcome this difficulty, static pressure compensation
technique has been developed to increase the dynamic range of the microphones, resulting accurate measurement of transmission
loss in the presence of high noise level. Series of experiments to investigate the acoustic characteristics of expansion chamber
with mean flow has been performed using the pressure compensated microphones. Results demonstrate: (1) frequency shift due
to the presence of mean flow, (2) effect of length, diameter, offset length and twisting angles to the transmission loss of
expansion chamber with and without mean flow (up to 50m/sec), (3) relation between the proposed parameter ‘aspect ratio’ and
number of peaks of transmission loss in low frequency region. 相似文献
1000.
An efficient procedure to obtain the optimal stacking sequence and the minimum weight of stiffened laminated composite curved
panels under several loading conditions and stiffener layouts has been developed based on the finite element method and the
genetic algorithm that is powerful for the problem with integer variables. Often, designing composite laminates ends up with
a stacking sequence optimization that may be formulated as an integer programming problem. This procedure is applied for a
problem to find the stacking sequence having a maximum critical buckling load factor and the minimum weight. The object function
in this case is the weight of a stiffened laminated composite shell. Three different types of stiffener layouts with different
loading conditions are investigated to see how these parameters influence on the stacking sequence optimization of the panel
and the stiffeners. It is noticed from the results that the optimal stacking sequence and lay-up angles vary depending on
the types of loading and stiffener spacing. 相似文献