全文获取类型
收费全文 | 6524篇 |
免费 | 398篇 |
国内免费 | 156篇 |
专业分类
电工技术 | 275篇 |
综合类 | 550篇 |
化学工业 | 507篇 |
金属工艺 | 1075篇 |
机械仪表 | 1307篇 |
建筑科学 | 350篇 |
矿业工程 | 316篇 |
能源动力 | 638篇 |
轻工业 | 260篇 |
水利工程 | 250篇 |
石油天然气 | 187篇 |
武器工业 | 129篇 |
无线电 | 141篇 |
一般工业技术 | 549篇 |
冶金工业 | 313篇 |
原子能技术 | 37篇 |
自动化技术 | 194篇 |
出版年
2024年 | 25篇 |
2023年 | 70篇 |
2022年 | 121篇 |
2021年 | 152篇 |
2020年 | 195篇 |
2019年 | 125篇 |
2018年 | 120篇 |
2017年 | 189篇 |
2016年 | 208篇 |
2015年 | 233篇 |
2014年 | 396篇 |
2013年 | 365篇 |
2012年 | 487篇 |
2011年 | 524篇 |
2010年 | 372篇 |
2009年 | 375篇 |
2008年 | 277篇 |
2007年 | 424篇 |
2006年 | 401篇 |
2005年 | 310篇 |
2004年 | 291篇 |
2003年 | 252篇 |
2002年 | 236篇 |
2001年 | 165篇 |
2000年 | 141篇 |
1999年 | 124篇 |
1998年 | 95篇 |
1997年 | 72篇 |
1996年 | 80篇 |
1995年 | 63篇 |
1994年 | 38篇 |
1993年 | 48篇 |
1992年 | 28篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有7078条查询结果,搜索用时 0 毫秒
1.
Abrasive water jet technology can be used for micro-milling using recently developed miniaturized nozzles. Abrasive water jet (AWJ) machining is often used with both the nozzle tip and workpiece submerged in water to reduce noise and contain debris. This paper compares the performance of submerged and unsubmerged abrasive water jet micro-milling of channels in 316L stainless steel and 6061-T6 aluminum at various nozzle angles and standoff distances. The effect of submergence on the diameter and effective footprint of AWJ erosion footprints was measured and compared. It was found that the centerline erosion rate decreased with channel depth due to the spreading of the jet as the effective standoff distance increased, and because of the growing effect of stagnation as the channel became deeper. The erosive jet spread over a larger effective footprint in air than in water, since particles on the jet periphery were slowed much more quickly in water due to increased drag. As a result, the width of a channel machined in air was wider than that in water. Moreover, it was observed that the instantaneous erosion rate decreased with channel depth, and that this decrease was a function only of the channel cross-sectional geometry, being independent of the type of metal, the jet angle, the standoff distance, and regardless of whether the jet was submerged or in air, in either the forward or backward directions. It is shown that submerged AWJM results in narrower features than those produced while machining in air, without a decrease in centerline etch rate. 相似文献
2.
董祥国 《机械制造与自动化》2002,(6):17-19
根据三角旋转活塞发动机运动几何原理 ,详细分析了缸体型线。缸体的实际型线是双弧外摆线的等距曲线 ,并由此导出其数学表达式。本文进一步说明了两种几何运动实现方式 ,分析了参数的几何意义 ,并给出其表达式。 相似文献
3.
4.
Kang Hai-gui 《水动力学研究与进展(B辑)》1994,(2)
HYDRODYNAMIC FORCE ON SMOOTH HORIZONTAL CYLINDER IN UNIFORM OSCILLATORY FLOWHYDRODYNAMICFORCEONSMOOTHHORIZONTALCYLINDERINUNIF... 相似文献
5.
Wang Jia-lu Department of Engineering Mechanics Tsinghua University Beijing P.R.ChinaSun Mao Lian Qi-xiang Institute of Fluid Mechanics Beijing University of Aeronautics Astronautics Beijing P.R.China 《水动力学研究与进展(B辑)》1993,(4)
The starting flow around a uniformly accelerated circular cylinder is investigatedby flow visualization techncque and solving N-S equations numerically in detail.The results ofthe starting flow are similar with those of the impulsively started one.At lower Re_α,numbers the“phenomenon a”is revealed;the“phenomenon β”appears at higher Re_α numbers,but withonly one secondary vortex.At the early stage of the starting vortex formation,the flow islaminar;at the later stage,the flow transforms into turbulent flow.The velocity distribution inthe flow field is measured with the multiwires installment.The calculational results are comparedwith the results of experiment,and both are in agreement with each other. 相似文献
6.
7.
8.
本文导出了线性波浪作用于上部可渗透的直立刚性圆柱体上的水动力的解析解。在线性有势流的假定下,用特征函数展开方法求出了内部和外部流场的解。给出了不同波浪要素及结构尺寸参数下的数值结果。由结果可知,提高可渗透性可以有效消减波幅。 相似文献
9.
水下物体运动引起扰动,会在海面产生尾迹。这种尾迹特征同运动物体的参数和下潜的深度以及海况有关。研究这种尾迹特征及其合成孔径雷达(SAR)成像,就有可能利用SAR来检测这个水下运动物体。本文给出了一种水下运动物体的伴流尾迹的快速模拟方法及其合成孔径雷达(SAR)成像仿真方法,并对模拟仿真的结果进行了讨论。 相似文献
10.
Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder 总被引:1,自引:0,他引:1
By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented. 相似文献