全文获取类型
收费全文 | 21962篇 |
免费 | 3616篇 |
国内免费 | 643篇 |
专业分类
电工技术 | 631篇 |
综合类 | 1075篇 |
化学工业 | 1091篇 |
金属工艺 | 11252篇 |
机械仪表 | 3497篇 |
建筑科学 | 890篇 |
矿业工程 | 445篇 |
能源动力 | 382篇 |
轻工业 | 289篇 |
水利工程 | 130篇 |
石油天然气 | 1362篇 |
武器工业 | 186篇 |
无线电 | 689篇 |
一般工业技术 | 2685篇 |
冶金工业 | 1113篇 |
原子能技术 | 105篇 |
自动化技术 | 399篇 |
出版年
2024年 | 90篇 |
2023年 | 289篇 |
2022年 | 419篇 |
2021年 | 444篇 |
2020年 | 569篇 |
2019年 | 602篇 |
2018年 | 640篇 |
2017年 | 908篇 |
2016年 | 939篇 |
2015年 | 889篇 |
2014年 | 1366篇 |
2013年 | 1930篇 |
2012年 | 1393篇 |
2011年 | 1601篇 |
2010年 | 1209篇 |
2009年 | 1187篇 |
2008年 | 997篇 |
2007年 | 1454篇 |
2006年 | 1520篇 |
2005年 | 1149篇 |
2004年 | 1129篇 |
2003年 | 967篇 |
2002年 | 828篇 |
2001年 | 731篇 |
2000年 | 596篇 |
1999年 | 486篇 |
1998年 | 396篇 |
1997年 | 341篇 |
1996年 | 303篇 |
1995年 | 217篇 |
1994年 | 169篇 |
1993年 | 102篇 |
1992年 | 96篇 |
1991年 | 71篇 |
1990年 | 59篇 |
1989年 | 58篇 |
1988年 | 29篇 |
1987年 | 19篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
连续驱动摩擦焊动态扭矩检测的新方法──VCMM法刘金合,罗键连续驱动摩擦焊扭矩是一个重要的工艺参数。摩擦焊扭矩是动态扭矩,具有时变性、速变性以及变化范围大等特点。现有的检测摩擦焊扭矩的方法均有一定的局限性’‘-’‘,本文提出了通过驱动主电机定子电压和... 相似文献
43.
对省煤器开裂管进行了化学成分及宏、微观分析。分析结果表明,在高温高压条件下,在其焊缝溶合区出现粗大的魏氏组织,管材中的珠光体组织产生了不同程度的球化,而母材组织又存在严重的带状组织。在过热条件下熔合区极易出现裂纹,并由此快速扩展,造成省煤器管开裂。 相似文献
44.
以莱钢万力H型钢有限公司抽柱换梁工程为例,介绍行车梁拼装、柱加固拆除及托粱吊装前后的测量观测。 相似文献
45.
G. Biallas Dr.‐Ing. C. Sick J. Schneider K.‐H. Trautmann 《Materialwissenschaft und Werkstofftechnik》2007,38(9):705-711
Biaxial fatigue of friction stir welded stiffened panels Within the framework of the European WelAir project, cruciform specimens made from stiffening FSW overlap joints were fatigued in the DLR biaxial test rig. To resemble the loading situation of pressurized fuselage structures, proportional loading without any phase shift, but with different load ratios λ between the loading components in both directions was applied.Natural crack initiation and subsequent crack growth were governed by the stiffness gradient caused by introducing the stringer. Cracks initiated and propagated at run‐in and run‐out locations in a direction perpendicular to the weld seam. The shortest fatigue life was observed for uniaxial loading in welding direction (λ = 0). An additional stress component perpendicular to the joint line (λ > 0) resulted in a higher number of cycles to failure. Similar to single stringer panels, increasing the load ratio also increased the number of cycles to failure for FSW clip‐stringer structural members, but additionally gives a different location of the fatal crack. 相似文献
46.
47.
Influence of Ni Interlayers on the Mechanical Properties of Ti6Al4V/(WC-Co) Friction Welds 总被引:2,自引:0,他引:2
M. Shamanian M. Salehi A. Saatchi T. H. North 《Materials and Manufacturing Processes》2003,18(4):581-598
Ni interlayers were introduced prior to dissimilar friction welding of Ti6Al4V base material to three cemented carbide substrates. The fracture strength of Ti6Al4V/(WC-6 wt% Co) welds were poor and were markedly improved when 20-µm thick Ni interlayers were introduced prior to dissimilar friction welding. These results were only produced when the (WC-6 wt% Co) cermet was electroplated prior to friction welding. When the Ti6Al4V alloy was electroplated prior to friction welding, fractured WC particles and cracking were observed in the (WC-Co) carbide substrate. The fracture strengths of Ti6Al4V/(WC-11 wt% Co) and Ti6Al4V/(WC-24 wt% Co) welds were not improved when 20-µm thick Ni interlayers were introduced prior to friction welding. During mechanical testing, the Ni layer retained at the dissimilar joint interface created a region of weakness. 相似文献
48.
49.
Shallow turbulent flows were produced in a tank of small thickness to study the friction effects on large-scale turbulent motion of small depth. The tank was constructed of two parallel walls. The space between the parallel walls (4.4, 1.57, and 0.59 cm) was small compared with the height (107 cm) and the width (212 cm) of the tank, and was varied during the experiments for different friction effects. Turbulent flows were produced by the injection of water in the form of starting jets into the tank filled with water. The large-scale turbulent flow in the small space between the walls of the tank is confined to essentially two-dimensional motion, and the motion is retarded by the force of friction. Dye was injected with the source fluid as the tracer for the highly unsteady and quasitwo-dimensional turbulent motion. From the initiation of the turbulent motion at the source to the final interaction of the jets with the tank bottom, the entire sequence of events was recorded by a pair of video cameras. The depth-averaged concentration of the dye was analyzed using the recorded video images. 相似文献
50.