全文获取类型
收费全文 | 188522篇 |
免费 | 18142篇 |
国内免费 | 10203篇 |
专业分类
电工技术 | 14161篇 |
技术理论 | 9篇 |
综合类 | 19322篇 |
化学工业 | 18613篇 |
金属工艺 | 7696篇 |
机械仪表 | 16719篇 |
建筑科学 | 23972篇 |
矿业工程 | 7308篇 |
能源动力 | 8090篇 |
轻工业 | 14310篇 |
水利工程 | 7923篇 |
石油天然气 | 9592篇 |
武器工业 | 2131篇 |
无线电 | 10488篇 |
一般工业技术 | 19159篇 |
冶金工业 | 7640篇 |
原子能技术 | 2578篇 |
自动化技术 | 27156篇 |
出版年
2024年 | 848篇 |
2023年 | 2465篇 |
2022年 | 4854篇 |
2021年 | 5658篇 |
2020年 | 5966篇 |
2019年 | 4958篇 |
2018年 | 4850篇 |
2017年 | 5854篇 |
2016年 | 7023篇 |
2015年 | 7401篇 |
2014年 | 12059篇 |
2013年 | 12142篇 |
2012年 | 13957篇 |
2011年 | 15327篇 |
2010年 | 11081篇 |
2009年 | 11265篇 |
2008年 | 10528篇 |
2007年 | 12705篇 |
2006年 | 11000篇 |
2005年 | 9242篇 |
2004年 | 7865篇 |
2003年 | 6675篇 |
2002年 | 5342篇 |
2001年 | 4486篇 |
2000年 | 3836篇 |
1999年 | 3174篇 |
1998年 | 2709篇 |
1997年 | 2315篇 |
1996年 | 1914篇 |
1995年 | 1574篇 |
1994年 | 1378篇 |
1993年 | 1051篇 |
1992年 | 953篇 |
1991年 | 697篇 |
1990年 | 603篇 |
1989年 | 516篇 |
1988年 | 421篇 |
1987年 | 293篇 |
1986年 | 246篇 |
1985年 | 240篇 |
1984年 | 267篇 |
1983年 | 252篇 |
1982年 | 204篇 |
1981年 | 98篇 |
1980年 | 109篇 |
1979年 | 67篇 |
1978年 | 54篇 |
1977年 | 48篇 |
1976年 | 44篇 |
1959年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
广州地铁一号线隧道结构变形监测及成果分析 总被引:5,自引:0,他引:5
介绍了广州地铁一号线运营以来的全线隧道结构变形监测 ,分析了隧道结构的安全状况和各种变化规律 ,并对其变形原因进行有益的探讨 相似文献
74.
75.
前向反冲分析和非卢瑟福背散射 总被引:1,自引:0,他引:1
赵国庆 《理化检验(物理分册)》2002,38(2):88-91
介绍了弹性散射分析中的另外两种分析方法——前向反冲分析和非卢瑟福背散射分析。前向反冲分析适用于材料中H和He同位素分析。高能质子和He离子背散射分析可提高对重基体中C,N和O等轻元素分析的灵敏度。给出了这两种分析方法的应用实例。 相似文献
76.
结合凤山实业总公司硫酸车间 SO2 转化系统的具体工艺流程 ,分析近几年转化系统出现温度不正常的原因 ,提出解决方法 相似文献
77.
The failure of the conductor of the 460 kV overhead transmission line located along the crossing of the Paraná River was investigated. As a result of this failure, a blackout took place in the southern states of Brazil in January of 2002, reaching approximately 67 million inhabitants. Investigation of the external aluminium layer of the ACSR conductor near the fracture showed typical static deformation marks and dynamic fretting wear tangential marks, both associated with the presence of Al2O3 debris. Additionally, encrusted silicon particles were observed on the external surface of the strands. The internal Al layer showed elliptical deformation marks also associated with Al2O3 debris. Both Al2O3 and Si particles are efficient abrasive material, which associated with slight relative motion of metallic surfaces (clamp/strand and strand/strand) can promote fretting wear. Two types of fracture surface of the Al strands were identified: 45° and quasi-normal surfaces, the former being the predominant type. Delamination and particle detachment were the mechanisms of superficial degradation observed on the Al strands, indicating that the rupture of the strands occurred under a gross slip fretting regime induced by sub-conductor oscillation. Inspection of the internal surface of as-cast Al–10%Si spacer clamps revealed different stages of intense circumferential wear caused by the preferential cracking and particle detachment of the eutectic constituent of the as-cast microstructure. This intense wear reduces the clamping contact pressure, which allows higher displacement amplitude and leads to the critical fretting regime. Finally, a few suggestions are discussed to minimise the occurrence of future failures. 相似文献
78.
从范围、原材料要求、组分要求、物理力学性能等方面对比分析了我国现行油毡瓦标准与欧美标准的区别,提出了我国制订沥青油毡瓦国家标准的的原则。 相似文献
79.
80.
The use of light gauge steel framing is increasing rapidly. New methods for joining frames are being sought. One of the most promising methods is clinching. Clinching has been used for almost 20 years. There has been much research into the method, the tools, suitable materials and applications. Few articles have been published concerning clinching of high strength structural steels, which are currently the most relevant materials for house construction.This study included 11 different clinching methods. In total, 469 test pieces were produced. Despite the high strength of the materials, all the clinching methods that were examined could be used satisfactorily. The most significant result was that a round tool is appropriate for all the materials tested. In fact, in comparison with results obtained using other types of tool, when the methods were ranked by maximum shear load capacity, the round design appeared in the top three classes seven times out of nine. 相似文献