全文获取类型
收费全文 | 12310篇 |
免费 | 1285篇 |
国内免费 | 979篇 |
专业分类
电工技术 | 257篇 |
综合类 | 1073篇 |
化学工业 | 647篇 |
金属工艺 | 2670篇 |
机械仪表 | 1901篇 |
建筑科学 | 948篇 |
矿业工程 | 176篇 |
能源动力 | 343篇 |
轻工业 | 232篇 |
水利工程 | 52篇 |
石油天然气 | 412篇 |
武器工业 | 147篇 |
无线电 | 307篇 |
一般工业技术 | 4271篇 |
冶金工业 | 578篇 |
原子能技术 | 92篇 |
自动化技术 | 468篇 |
出版年
2024年 | 39篇 |
2023年 | 198篇 |
2022年 | 262篇 |
2021年 | 339篇 |
2020年 | 468篇 |
2019年 | 421篇 |
2018年 | 364篇 |
2017年 | 460篇 |
2016年 | 545篇 |
2015年 | 606篇 |
2014年 | 706篇 |
2013年 | 733篇 |
2012年 | 751篇 |
2011年 | 809篇 |
2010年 | 595篇 |
2009年 | 662篇 |
2008年 | 561篇 |
2007年 | 673篇 |
2006年 | 627篇 |
2005年 | 556篇 |
2004年 | 519篇 |
2003年 | 430篇 |
2002年 | 374篇 |
2001年 | 350篇 |
2000年 | 352篇 |
1999年 | 307篇 |
1998年 | 246篇 |
1997年 | 264篇 |
1996年 | 255篇 |
1995年 | 176篇 |
1994年 | 159篇 |
1993年 | 136篇 |
1992年 | 118篇 |
1991年 | 90篇 |
1990年 | 90篇 |
1989年 | 70篇 |
1988年 | 61篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 33篇 |
1984年 | 38篇 |
1983年 | 35篇 |
1982年 | 35篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
本文考虑了焊接结构的几何形状、受载形式、应力比、残余应力、尺寸效应以及材料等因素对疲劳寿命的影响,利用Peterson公式和极值疲劳切口系数概念,建立了一般应力比时焊接结构S-N曲线的预估模型.文中对几类典型的焊接结构的S-N曲线进行了预测,预测值与实验结果符合较好.本文方法可以大量减少疲劳实验,具有一定的工程实用价值. 相似文献
52.
PZT铁电薄膜的制备及电学性能研究 总被引:6,自引:1,他引:5
使用硝酸锆作锆源的溶胶-凝胶方法制备PZT铁电薄膜。他们的电学性能被测试包括电滞回线,电流I(t)特性,漏电流,矫顽场疲劳和老化。测到的PZT薄膜剩余极化8.2μC/cm~2,矫顽场68kV/cm.簿膜的寿命可超过10~(11)周期。 相似文献
53.
This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and ‘metadelaminations’ between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a ‘meta-CDS’) was observed. It was found that woven composites have a unit area of damage accumulation (called a ‘unit cell’) and the damage of each unit cell and its distribution control the total fatigue damage of the material. 相似文献
54.
55.
Abstract— In response to the increasing structural applications in duplex steels for welded structures, fatigue behaviour of a SAF 2304 grade duplex stainless steel was investigated, considering both the base metal and GTAW welded joints. Fatigue curves and fatigue limits under rotary bending fatigue were obtained. The study focused attention on the microstructural features of fatigue crack propagation of the two series of experiments, thereby permitting an evaluation of the tortuous crack path of welded joints and the mechanisms related to threshold microstructural barriers. 相似文献
56.
C. M. Branco J. M. Ferreira M. O. W. Richardson P. Fael 《International Journal of Fatigue》1992,14(6):367-376
This paper presents results of a fatigue life investigations carried out in plate specimens of a fibre-glass-reinforced phenolic matrix composite. Tensile and Young's modulus data were obtained at four different testing temperatures (room temperature, 100, 150 and 200 °C). The fatigue S−N data were obtained at room temperature only and for two stress ratio values (R=0 and 0.4). Fatigue and tensile behaviour was assesesed in the composite with the fibres aligned in the longitudinal loading direction. The results were obtained for two values of volume fraction (0.28 and 0.42) and three different glass surface treatments. A detailed comparison of fatigue results is given taking into account several fatigue parameters and also the testing variables. Results of observations of SEM fracture surfaces are also presented. 相似文献
57.
58.
In-phase(IP) and out-of-phase(OP)thermal-mechanical fatigue(TMF) behavior of cast Ni-base superalloy K417 was studied.All experiments were carried out under total strain control with temperature cycling between 400-850℃.Both in-phase and out-of-phase TMF specimens exhibited cyclic hardening followed by cyclic softening at the minimum temperature.Besides,they cyclically hardened in the early stage of life followed by cyclic softening at the minimum temperature.Besides,they cyclically hardened in the early stage of life followed by cyclic softening at the maximum temperature.OP TMF life was longer than of IP TMF.Various damage mechanisms operating in different controlled strain ranges and phasing were discussed.A few life prediction methods for isothermal fatigue were used to handle TMF fatigue and their applicability to superalloy K417 was evaluated.The SEM analysis of the fracture surface showed that transgranular fracture was the principal cracking mode for both IP and OP TMF.Oxidation was the main damage mechanism in causing shorter fatigue life for IP TMF compared with OP TMF. 相似文献
59.
提高连续油管使用寿命的方法 总被引:2,自引:1,他引:1
从采用软件跟踪疲劳寿命 ,截断法 ,变径连续油管 ,反转使用连续油管 ,防止连续油管损伤 ,合理配置设备 6个方面讨论了控制管串疲劳 ,提高连续油管使用寿命的方法 ,并得出结论 :控制管串疲劳的方法中 ,最有效的方法是实际作业截断法。指出要尽量减少连续油管在带内压下工作 ,也要研究开发降阻性能好的工作液 ,以延长连续油管使用寿命、降低作业风险。 相似文献
60.
Crack propagation tests were carried out on 2024-T3 sheet specimens to study the effects of omitting low-amplitude cycles from the gust-dominated TWIST load sequence (MiniTWIST) and the removal of small load ranges from the manoeuvre-dominated FALSTAFF load sequence (short FALSTAFF). In other tests high-amplitude loads of TWIST and MiniTWIST were truncated at different levels. The results are compared with data from similar test programmes, including crack initiation. Attention is paid to unstationary crack growth retardation and a transient retardation during initial crack growth started by an artificial crack. 相似文献