全文获取类型
收费全文 | 22040篇 |
免费 | 1568篇 |
国内免费 | 882篇 |
专业分类
电工技术 | 625篇 |
综合类 | 1455篇 |
化学工业 | 1271篇 |
金属工艺 | 4957篇 |
机械仪表 | 2552篇 |
建筑科学 | 1412篇 |
矿业工程 | 397篇 |
能源动力 | 573篇 |
轻工业 | 1660篇 |
水利工程 | 287篇 |
石油天然气 | 548篇 |
武器工业 | 141篇 |
无线电 | 406篇 |
一般工业技术 | 2027篇 |
冶金工业 | 5251篇 |
原子能技术 | 234篇 |
自动化技术 | 694篇 |
出版年
2024年 | 81篇 |
2023年 | 308篇 |
2022年 | 638篇 |
2021年 | 778篇 |
2020年 | 819篇 |
2019年 | 573篇 |
2018年 | 497篇 |
2017年 | 703篇 |
2016年 | 745篇 |
2015年 | 741篇 |
2014年 | 1310篇 |
2013年 | 1130篇 |
2012年 | 1444篇 |
2011年 | 1609篇 |
2010年 | 1218篇 |
2009年 | 1306篇 |
2008年 | 860篇 |
2007年 | 1420篇 |
2006年 | 1372篇 |
2005年 | 1136篇 |
2004年 | 905篇 |
2003年 | 794篇 |
2002年 | 737篇 |
2001年 | 649篇 |
2000年 | 584篇 |
1999年 | 461篇 |
1998年 | 337篇 |
1997年 | 287篇 |
1996年 | 275篇 |
1995年 | 197篇 |
1994年 | 151篇 |
1993年 | 106篇 |
1992年 | 70篇 |
1991年 | 43篇 |
1990年 | 54篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1962年 | 1篇 |
1959年 | 3篇 |
1958年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
71.
M. E. Stevenson S. L. Lowrie R. D. Bowman B. A. Bennett 《Journal of Failure Analysis and Prevention》2002,2(4):55-60
Cold cracking of structural steel weldments is a well-characterized, well-documented, and well-understood failure mechanism.
Extensive effort has been put forth to recognize the welding and materials selection parameters that are conducive to cold
cracking; however, these engineering efforts have not fully eliminated the occurrence of such failures. This article describes
cold cracking failure specifically related to the construction industry. This particular failure was successfully identified
prior to final erection of the structural member, and the weld was successfully reworked. These actions potentially prevented
a serious catastrophic event that could have occurred have occurred either later in the construction process or possibly during
the use of the building. Individual welding parameters, such as electrode/wire selection, joint design, and pre/postheating,
played a role in the failure, and a number of human factors relating to the actual fabrication practices also contributed
to the failure process. 相似文献
72.
73.
介绍一种小型全内腔脉冲Ar+激光管的设计和结构。并对不同阴极,放电管直径,激励电压及Ar气压等对输出功率及激光管寿命的影响作了一系列的实验,试制出结构简单,使用方便,价格便宜的有一定实用价值的小型全内脏脉冲Ar+激光管。 相似文献
74.
报导一种全新冷却方式的双椭圆泵浦腔,具有较高的泵浦效率和光学均匀性。1.06μm调Q脉冲输出能量总转换效率η>0.75% 相似文献
75.
加氢裂化反应器新型冷氢箱的研究与工程设计 总被引:6,自引:1,他引:5
报道了加氢加化反应器新型旋流式冷氢箱的研究设计及实用效果,催化剂床层径向温差不大于5℃。 相似文献
76.
Effect of thermomechanical treatment on mechanical properties and electrical conductivity of a CuCrZr alloy 总被引:3,自引:0,他引:3
The CuCrZr alloy undergoes processes of precipitation during ageing. Besides precipitation hardening the strength is affected
by cold deformation which is performed before and after ageing.
The cold deformation (D
1) before ageing accelerates the process of strength hardening, since it induces higher rate of precipitation from the saturated
a-sold solution. Cold deformation (D
2) after ageing primarily affects the alloy strength.
In this paper the results of the effect of thermomechanical treatment on mechanical properties and electrical conductivity
of a CuCrZr alloy are presented. The aim of the paper was to evaluate the most suitable combination of thermomechanical treatment
and alloy properties. 相似文献
77.
R. Gnanamoorthy N. Rajiv K. Gopinath Y. Miyahsita Y. Mutoh 《Journal of Failure Analysis and Prevention》2002,2(4):71-75
Powder-metal-processed bearings and gears are finding increasing application because of their economical and technical advantages.
The residual pores from the sintering operatives act as lubricant pockets and dampen sound and vibration. However, porosity
also decreases the mechanical strength and reduces the life of components fabricated by powder processing relative to similar
wrought components. The rolling contact fatigue behavior of sintered and heat treated steel rollers was investigated using
a fatigue test machine designed and fabricated for that purpose. The powder-metal-processed and the wrought steel rollers
that were tested had similar composition and hardness and were mated against wrought steel rollers of high hardness. The contact
stress versus number of cycles to failure data showed that the wrought steel had a very high endurance limit under rolling
contact fatigue compared to the sintered steels investigated. Rolling contact fatigue behavior was found to depend on the
porosity present in the material. Large surface peeling failures and pitting type fatigue failures were observed in the sintered
and hardened steels, while only pitting type failures were observed in the wrought steels 相似文献
78.
Ti-23Al-14Nb-3V合金氩弧焊接头的显微组织及其力学性能 总被引:6,自引:1,他引:5
研究了预热对Ti-23Al-14Nb-3V合金焊接性,特别是对消除氩弧焊冷裂纹的作用以及对接头显微组织和力学性能的影响。结果表明,焊前预热可有效降低该合金的冷裂倾向。经预热处理后,焊缝区的结晶层状线消失,热影响区的硬度峰得到缓和,整个焊缝的显微硬度分布趋于均匀,但焊缝区的枝晶发生粗化,热影响区有所扩大。焊件接头的拉伸试验表明,预热可使焊缝区的接头强度系数增加,但无论预热与否,接头强度均低于母材强度,且不显示宏观塑性。 相似文献
79.
本文首先介绍国内和日本、德国、俄罗斯等国冷轧薄钢板及镀锌薄钢板的牌号、标记识别及生产地及与我国家标准薄钢板牌号的相互之间的关系,并比较具体地介绍冷轧板的实效性、镀锌薄钢板的锌层特性等诸多方面的状况。从而帮助我们在设计、制造家电产品中,比较正确地选择合适的板材。 相似文献
80.