全文获取类型
收费全文 | 75952篇 |
免费 | 6176篇 |
国内免费 | 3709篇 |
专业分类
电工技术 | 1314篇 |
技术理论 | 5篇 |
综合类 | 6016篇 |
化学工业 | 5636篇 |
金属工艺 | 18246篇 |
机械仪表 | 3481篇 |
建筑科学 | 18567篇 |
矿业工程 | 2012篇 |
能源动力 | 1132篇 |
轻工业 | 1653篇 |
水利工程 | 969篇 |
石油天然气 | 2503篇 |
武器工业 | 384篇 |
无线电 | 516篇 |
一般工业技术 | 7547篇 |
冶金工业 | 14616篇 |
原子能技术 | 545篇 |
自动化技术 | 695篇 |
出版年
2024年 | 186篇 |
2023年 | 800篇 |
2022年 | 1846篇 |
2021年 | 2120篇 |
2020年 | 2250篇 |
2019年 | 1725篇 |
2018年 | 1477篇 |
2017年 | 2296篇 |
2016年 | 2423篇 |
2015年 | 2743篇 |
2014年 | 4774篇 |
2013年 | 4317篇 |
2012年 | 5540篇 |
2011年 | 6368篇 |
2010年 | 4778篇 |
2009年 | 4941篇 |
2008年 | 3976篇 |
2007年 | 5095篇 |
2006年 | 4566篇 |
2005年 | 3826篇 |
2004年 | 3190篇 |
2003年 | 2743篇 |
2002年 | 2341篇 |
2001年 | 1976篇 |
2000年 | 1716篇 |
1999年 | 1404篇 |
1998年 | 1110篇 |
1997年 | 1188篇 |
1996年 | 906篇 |
1995年 | 684篇 |
1994年 | 593篇 |
1993年 | 414篇 |
1992年 | 383篇 |
1991年 | 261篇 |
1990年 | 222篇 |
1989年 | 195篇 |
1988年 | 141篇 |
1987年 | 75篇 |
1986年 | 46篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1980年 | 47篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1975年 | 4篇 |
1959年 | 10篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
This paper studies a Kansas Department of Transportation welded plate girder bridge that developed fatigue cracks at small web gaps close to the girder top flange. Repair had been previously performed by softening the connection plate end with a slot retrofit, but cracks were recently found to have reinitiated at some of the repaired details and are again propagating. A comprehensive finite-element method study was performed to investigate the cracking behavior observed in the bridge and to recommend appropriate measures for future bridge retrofit. The analytical results show that stresses developed at the top flange web gaps could exceed yielding under the loading of an HS15 fatigue truck. The current slot repair used in the bridge was found to have introduced higher magnitude fatigue stresses in the web gap. To achieve a permanent repair of the bridge, it is recommended that a welded connection plate to flange attachment be used during future bridge retrofit. The web gap details should be able to withstand unlimited number of load cycles once this additional repair is performed. 相似文献
103.
R. RODRÍGUEZ-MARTÍN I. OCAÑA A. MARTÍN-MEIZOSO 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(7):664-670
High-strength steels are used to increase the load carrying capacity of components. However, to guarantee a safe design, it is also necessary to combine high strength with adequate fracture toughness. In this paper, fracture toughness of three high-strength steels with yield strengths ranging from 460 to 890 MPa has been studied at very low temperatures. Taking into account experimental evidence, a new mechanism of cleavage at very low temperatures is proposed. This mechanism considers the possibility of reaching the ideal strength (the stress at which the lattice of a single crystal losses its stability) in the immediate vicinity of the fatigue crack tip. Moreover, a computational model able to calculate the external load needed to produce a catastrophic failure of these steels has been developed. 相似文献
104.
105.
对唐钢薄板坯连铸机生产的SS400钢的生产工艺进行了分析,认为薄板坯连铸机生产的SS400钢,在采取了精炼站在线定氧,将钢水全氧控制在25×10~(-6)左右,同时连铸采取保护浇注和轻压下等技术后,能够确保薄板坯连铸SS400钢的顺利浇注,轧制的板带材表面质量良好,机械性能符合要求。 相似文献
106.
25Cr3Mo3NiNb二次硬化钢中的碳化物 总被引:1,自引:0,他引:1
利用TEM和萃取相分析方法,研究了25Cr3Mo3NiNb二次硬化钢淬火回火组织中的碳化物。结果表明,随淬火奥氏体化温度的升高,M6C型碳化物逐渐溶解。于1050℃奥氏体化时M6C型碳化物全部溶解,淬火态试样中只有少量的Nb(C,N)颗粒和自回火M3C型碳化物。随回火温度的升高,先后析出ε、M3C、M2C和M7C3等类型的碳化物。Nb(C,N)颗粒可以阻止淬火奥氏体晶粒的异常长大,而高温回火析出的M2C碳化物有二次硬化作用,从而提高回火稳定性和高温强韧性。 相似文献
107.
梁昔明 《中南工业大学学报(英文版)》2005,12(1):93-96
An active set truncated-Newton algorithm (ASTNA) is proposed to solve the large-scale bound constrained sub-problems. The global convergence of the algorithm is obtained and two groups of numerical experiments are made for the various large-scale problems of varying size. The comparison results between ASTNA and the subspace limited memory quasi-Newton algorithm and between the modified augmented Lagrange multiplier methods combined with ASTNA and the modified barrier function method show the stability and effectiveness of ASTNA for simultaneous optimization of distillation column. 相似文献
108.
本文主要阐述了通过爆炸焊接和热轧的方法,研制成功可焊性良好的且具有较好强度、韧性与综合性能的双相耐应力腐蚀的不锈复合钢板。还将热轧与热处理的两种试验作了较全面的常规、特殊检验试验,结果完全达到使用要求。 相似文献
109.
StudyonHotDeformationCracksofSteelD2UsingProcesingMapGaoShan,LiuXianghua,WangGuodongABSTRACTThehotdeformationbehaviorsofsteel... 相似文献
110.
R. Knockaert I. Doghri Y. Marchal T. Pardoen F. Delannay 《International Journal of Fracture》1996,81(4):383-399
Double-edge notched (DENT) steel plates were pulled until complete fracture and several experimental observations were made (using profilometry and scanning electron microscopy). The essential work of fracture (EWF) model was found to be well verified. Numerical simulations—up to the maximum load only—of some experiments were performed using the finite element method (FEM), and incorporating geometric and material non-linearities (large deformation elasto-plasticity). Some experimental measurements were compared with the corresponding numerical computations and excellent agreement was found. 相似文献