全文获取类型
| 收费全文 | 1670篇 |
| 免费 | 91篇 |
| 国内免费 | 136篇 |
专业分类
| 电工技术 | 17篇 |
| 综合类 | 57篇 |
| 化学工业 | 69篇 |
| 金属工艺 | 637篇 |
| 机械仪表 | 84篇 |
| 建筑科学 | 14篇 |
| 矿业工程 | 16篇 |
| 能源动力 | 253篇 |
| 轻工业 | 17篇 |
| 水利工程 | 1篇 |
| 石油天然气 | 60篇 |
| 武器工业 | 18篇 |
| 无线电 | 18篇 |
| 一般工业技术 | 342篇 |
| 冶金工业 | 228篇 |
| 原子能技术 | 56篇 |
| 自动化技术 | 10篇 |
出版年
| 2025年 | 12篇 |
| 2024年 | 35篇 |
| 2023年 | 50篇 |
| 2022年 | 65篇 |
| 2021年 | 59篇 |
| 2020年 | 66篇 |
| 2019年 | 62篇 |
| 2018年 | 51篇 |
| 2017年 | 50篇 |
| 2016年 | 33篇 |
| 2015年 | 43篇 |
| 2014年 | 70篇 |
| 2013年 | 83篇 |
| 2012年 | 76篇 |
| 2011年 | 101篇 |
| 2010年 | 76篇 |
| 2009年 | 98篇 |
| 2008年 | 69篇 |
| 2007年 | 63篇 |
| 2006年 | 68篇 |
| 2005年 | 67篇 |
| 2004年 | 74篇 |
| 2003年 | 62篇 |
| 2002年 | 64篇 |
| 2001年 | 45篇 |
| 2000年 | 36篇 |
| 1999年 | 46篇 |
| 1998年 | 44篇 |
| 1997年 | 46篇 |
| 1996年 | 46篇 |
| 1995年 | 31篇 |
| 1994年 | 26篇 |
| 1993年 | 15篇 |
| 1992年 | 15篇 |
| 1991年 | 13篇 |
| 1990年 | 10篇 |
| 1989年 | 11篇 |
| 1988年 | 12篇 |
| 1987年 | 2篇 |
| 1984年 | 1篇 |
| 1959年 | 1篇 |
排序方式： 共有1897条查询结果，搜索用时 15 毫秒
31.
PC钢棒拉伸断口异常原因分析 总被引：1，自引：0，他引：1
用φ14 mm的45Si2Cr盘条生产1 420 MPa级φ13 mm光圆PC钢棒时,出现拉伸断口异常。分别对正常断口和异常断口进行宏观、微观形貌分析,正常断口为杯锥状,钢棒延伸率为8%,面缩率为41%;异常断口为脆性断口,钢棒延伸率为6%,面缩率为16%。正常断口微观形貌为韧窝状;异常断口为准解理,裂纹沿晶界分布。对正常断口和异常断口进行夹杂物分析,正常、异常断口处夹杂物直径分别为15,40μm,正常、异常断口的显微组织在边部、1/4部位差别不大,但异常断口心部组织较为粗大。钢中夹杂物和氢的共同作用是产生拉伸异常断口的主要原因。 相似文献
32.
33.
34.
《International Journal of Hydrogen Energy》2020,45(33):16890-16908
The coarse grain heat affected zone (CG-HAZ) of welds produced in a quenched and tempered 42CrMo4 steel was simulated by means of a laboratory heat treatment consisting in austenitizing at 1200 °C for 20 min, oil quenching and finally applying a post weld heat treatment at 700 °C for 2 h (similar to the tempering treatment previously applied to the base steel). A tempered martensite microstructure with a prior austenite grain size of 150 μm and a hardness of 230 HV, similar to the aforementioned CG-HAZ weld region, was produced. The effect of the prior austenite grain size on the hydrogen embrittlement (HE) behaviour of the steel was studied comparing this coarse-grained microstructure with that of the fine-grained base steel, with a prior austenite grain size of 20 μm.The specimens used in this study were charged with hydrogen gas in a reactor at 19.5 MPa and 450 °C for 21 h. Cylindrical specimens were used to determine hydrogen uptake and hydrogen desorption behaviour. Smooth and notched tensile specimens tested under different displacement rates were also used to evaluate HE.Embrittlement indexes, EI, were generally quite low in the case of hydrogen pre-charged tensile tests performed on smooth tensile specimens. However, very significant embrittlement indexes were obtained with notched tensile specimens. It was observed that these indexes always increase as the applied displacement rate decreases. Moreover, hydrogen embrittlement indexes also increase with increasing prior austenite grain size. In fact, the embrittlement index related to the reduction in area, EI(RA), reached values of over 20% and 50% for the fine and coarse grain size steels, respectively, when tested under the lowest displacement rates (0.002 mm/min).A comprehensive fractographic analysis was performed and the main operative failure micromechanisms due to the presence of internal hydrogen were determined at different test displacement rates. While microvoids coalescence (MVC) was found to be the typical ductile failure micromechanism in the absence of hydrogen in the two steels, brittle decohesion mechanisms (carbide-matrix interface decohesion, CMD, and martensitic lath interface decohesion, MLD) were observed under internal hydrogen. Intergranular fracture (IG) was also found to be operative in the case of the coarse-grained steel tested under the lowest displacement rate, in which hydrogen accumulation in the process zone ahead of the notch tip is maximal. 相似文献
35.
Morris M. Satin;W. Steven Johnson;Richard W. Neu; 《Fatigue & Fracture of Engineering Materials & Structures》2024,47(4):1395-1416
Thermomechanical fatigue (TMF) crack growth of Alloy 718 when the cycle includes long high-temperature tensile dwells is often accelerated because sustained-load crack growth occurs during the dwells and a temperature affected zone (TAZ) develops ahead of a crack tip that reduces fatigue crack growth resistance upon application of a cycle after the long dwell. This paper presents new TMF and sustained-load tests that aim to study and characterize the TAZ development and growth ahead of semi-elliptical and single-edge cracks. The influence of constraint on crack growth is assessed. This investigation focuses on a coarse-grained (CG) Alloy 718 at 650°C. By comparing the crack growth behavior between a fine-grained and CG microstructure after a long tensile dwell, a modification of the TAZ growth prediction model that includes the influence of grain size is proposed. Using this improved model for TAZ growth and acceleration, the TMF crack growth prediction of surface cracks is improved. 相似文献
36.
37.
在对原有冷轧平整液废水处理工艺分析的基础上,提出采用电催化氧化技术,验证其预处理平整液废水的可行性。试验结果表明,平整液废水COD、油的质量浓度分别为12000～20000、800～1000mg/L,BOD与COD的质量比小于0.35,经处理后,BOD与COD的质量比为0.5～0.6,COD的质量浓度为3000～5200mg/L,油的质量浓度小于70mg/L。电催化氧化处理冷轧平整液废水,出水稳定,可生化性好,满足生化处理的进水要求。 相似文献
38.
39.
40.
为了探明电化学修复对钢筋疲劳性能的影响,开展电化学除氯和双向电迁处理后钢筋的轴向拉伸疲劳试验. 基于断裂力学原理及断口微观形貌分析,揭示电化学修复技术引起钢筋疲劳性能变化的机理. 结果表明,电化学除氯会引起钢筋疲劳裂纹门槛值的减小及疲劳弹性模量的退化,宏观表现为钢筋疲劳寿命减小;电化学除氯后钢筋疲劳裂纹起源于钢中白点,裂纹扩展区疲劳辉纹间距增大,瞬断区韧窝变小变浅. 掺入阻锈剂的双向电迁方法对钢筋疲劳性能的负面影响较小,双向电迁修复后钢筋的疲劳断口微观形貌相对于普通钢筋未见明显变化. 相似文献