全文获取类型
收费全文 | 63182篇 |
免费 | 5236篇 |
国内免费 | 2726篇 |
专业分类
电工技术 | 3559篇 |
技术理论 | 7篇 |
综合类 | 4213篇 |
化学工业 | 10629篇 |
金属工艺 | 3534篇 |
机械仪表 | 3922篇 |
建筑科学 | 5388篇 |
矿业工程 | 1825篇 |
能源动力 | 1865篇 |
轻工业 | 4011篇 |
水利工程 | 1146篇 |
石油天然气 | 4423篇 |
武器工业 | 450篇 |
无线电 | 6988篇 |
一般工业技术 | 7886篇 |
冶金工业 | 3011篇 |
原子能技术 | 717篇 |
自动化技术 | 7570篇 |
出版年
2024年 | 97篇 |
2023年 | 972篇 |
2022年 | 1409篇 |
2021年 | 2291篇 |
2020年 | 1837篇 |
2019年 | 1590篇 |
2018年 | 1829篇 |
2017年 | 2058篇 |
2016年 | 1858篇 |
2015年 | 2344篇 |
2014年 | 3192篇 |
2013年 | 3645篇 |
2012年 | 4085篇 |
2011年 | 4422篇 |
2010年 | 3878篇 |
2009年 | 3683篇 |
2008年 | 3610篇 |
2007年 | 3511篇 |
2006年 | 3564篇 |
2005年 | 3083篇 |
2004年 | 2088篇 |
2003年 | 1872篇 |
2002年 | 1635篇 |
2001年 | 1585篇 |
2000年 | 1628篇 |
1999年 | 1739篇 |
1998年 | 1367篇 |
1997年 | 1154篇 |
1996年 | 1033篇 |
1995年 | 931篇 |
1994年 | 763篇 |
1993年 | 546篇 |
1992年 | 423篇 |
1991年 | 334篇 |
1990年 | 310篇 |
1989年 | 222篇 |
1988年 | 170篇 |
1987年 | 101篇 |
1986年 | 98篇 |
1985年 | 54篇 |
1984年 | 39篇 |
1983年 | 20篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
51.
Repair and replacement of offshore wind turbine blades are necessary for current and future offshore wind turbines. To date, repair activities are often conducted using huge jack‐up crane vessels and by applying a reverse installation procedure. Because of the high costs associated with installation and removal of offshore wind turbine components and the low profit margin of the offshore wind industry, alternative methods for installation and removal are needed. This paper introduces a novel concept for replacement or installation of offshore wind turbine blades. The concept involves a medium‐sized jack‐up crane vessel and a tower climbing mechanism. This mechanism provides a stable platform for clamping, lowering, and lifting of a blade. A case study of a 5‐MW offshore wind turbine is shown, where common engineering practices were applied and numerical simulations of the marine operations were carried out using finite element and multibody simulation tools. Operational limits for wave and wind actions were established to demonstrate the technical feasibility of the proposed concept. 相似文献
52.
Real‐time thermal states monitoring of absorber tube for parabolic trough solar collector with non‐uniform solar flux 下载免费PDF全文
With the world energy shortage problem becoming increasingly prominent, more and more attentions have been paid to the development of renewable energies. Among these sources, solar energy has received extensive attention with its excellent characteristics. The thermal state affects the safety of the solar heat collection system. In this paper, real‐time monitoring of the input heat flux on the inside wall and the temperature field simultaneously of an absorber tube for parabolic trough solar collector were studied. Based on the measured temperatures on the outside wall, the fuzzy adaptive Kalman filter coupled with weighted recursive least squares algorithm (WRLSA) was employed to monitor the heat states of the absorber tube inversely, in which WRLSA was used to acquire the heat flux while fuzzy adaptive Kalman filter was adopted to monitor the temperature field. The method showed strong robustness to resist the ill‐posedness. Accurate monitoring results also can be acquired when there are random disturbances of the heat transfer condition on the inner wall. 相似文献
53.
Iranian Polymer Journal - A novel class of photochromic copolymer based on spironaphthoxazine (SO) moieties was smoothly prepared through the copolymerization of methyl methacrylate (MMA), butyl... 相似文献
54.
应力测试是起重机安全评估中必须进行的一项检测。目前在安全评估工作中常采用应变电测法来采集起重机工作过程中的应力时程数据,由于该方法只能采集到结构由于载荷变化产生的应力,而无法采集到结构因自重产生的应力,导致应力测试无法获取结构的完整应力。利用起重机金属结构自重应力在总应力中占有的权重,分析其对应力测试实验结果的影响大小,试验结果表明在危险截面自重应力大小占总应力大小可达60%,此时不考虑自重应力进行结构安全性的判定是不全面的。可考虑利用仿真技术获取自重应力[1,2],从而使得安全评估应力测试实验结论更加准确。 相似文献
55.
Zu Guoqing Lu Yukuan Yan Yi Zhang Xiaoming Zhao Jingwei Du Wei Ran Xu Jiang Zhengyi 《Metals and Materials International》2020,26(2):248-259
Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500... 相似文献
56.
An-guo Wang Zhou-hua Jiang Yan-chun Lou Ji Tang Yun-long Xiong Yan-wu Dong Yan-wu Dong Fu-bin Liu Jing-chang Cheng Rui Chen 《中国铸造》2020,(1):48-55
Electroslag casting(ESC)is an important method to produce high quality castings.In this study,the ESC up-pulling inner mold method(EUPIM)was used to produce hollow cylindrical castings with the multiple consumable electrodes.The radial deformation,the axial and radial internal stress of the inner mold,and the axial internal stress of the slag shell were analyzed using the finite element method(FEM)with the aid of ANSYS software.The ProCAST software was used to calculate the specific heat,heat conductivity and density curve of Cu.Simulation results show that the radial deformation,the axial and radial internal stress of the inner mold,and the axial internal stress of the slag shell near the slag-metal interface of hollow cylndrical casting gradually increase from 0 s to 360 s after the ESC starting(slagging)process but before applying the up-pulling force.The suitable initial up-pulling moment of the inner mold is at around 180-198 s after the starting process. 相似文献
58.
59.
本文主要研究了Mg-40Al与Mg-20Ce固液界面在475°C, 500°C和525°C下保温5min至30min的界面反应和扩散层的生长动力学。结果发现,在扩散层中由于Al元素和Ce元素反应生成Al11Ce3, Al3Ce and Al2Ce金属化合物。金属化合物的体积分数随着扩散温度的升高而增加。扩散层的生长满足抛物线生长规律,扩散层的扩散激活能为42±3.7kJ/mol。实验研究的固液扩散为理解合金熔炼过程中金属化合物的形成提供了理论基础。 相似文献
60.
为了分析疏水引力在煤泥浮选过程中的作用机理,将-0.074mm的不同密度细粒煤泥混入粗粒煤泥中进行浮选试验,研究不同密度细粒煤泥对可燃体回收率的影响;进行了EDLVO理论计算,分析各作用能的作用效果和疏水引力的成因。结果表明:1.3~1.4 g/cm~3密度级细粒煤泥容易罩盖于粗粒精煤表面疏水部分;水中两个相互接近的疏水表面间的作用以疏水作用为主,疏水引力的产生是由于水中疏水表面相互接近到一定距离时自发形成了纳米气泡桥;浮选调浆的强度应适中,在破坏煤泥颗粒间疏水引力的同时而不破坏煤泥与气泡的附着。 相似文献