全文获取类型
收费全文 | 72557篇 |
免费 | 5557篇 |
国内免费 | 2725篇 |
专业分类
电工技术 | 3865篇 |
技术理论 | 6篇 |
综合类 | 4408篇 |
化学工业 | 12521篇 |
金属工艺 | 3924篇 |
机械仪表 | 4799篇 |
建筑科学 | 5152篇 |
矿业工程 | 2382篇 |
能源动力 | 2227篇 |
轻工业 | 4760篇 |
水利工程 | 988篇 |
石油天然气 | 5238篇 |
武器工业 | 460篇 |
无线电 | 7570篇 |
一般工业技术 | 9333篇 |
冶金工业 | 3789篇 |
原子能技术 | 750篇 |
自动化技术 | 8667篇 |
出版年
2024年 | 226篇 |
2023年 | 1198篇 |
2022年 | 1940篇 |
2021年 | 2860篇 |
2020年 | 2141篇 |
2019年 | 1904篇 |
2018年 | 2245篇 |
2017年 | 2469篇 |
2016年 | 2051篇 |
2015年 | 2681篇 |
2014年 | 3419篇 |
2013年 | 4194篇 |
2012年 | 4343篇 |
2011年 | 4852篇 |
2010年 | 4169篇 |
2009年 | 3949篇 |
2008年 | 3848篇 |
2007年 | 3709篇 |
2006年 | 3792篇 |
2005年 | 3430篇 |
2004年 | 2283篇 |
2003年 | 2082篇 |
2002年 | 1868篇 |
2001年 | 1636篇 |
2000年 | 1799篇 |
1999年 | 2035篇 |
1998年 | 1757篇 |
1997年 | 1406篇 |
1996年 | 1397篇 |
1995年 | 1176篇 |
1994年 | 938篇 |
1993年 | 709篇 |
1992年 | 539篇 |
1991年 | 420篇 |
1990年 | 323篇 |
1989年 | 249篇 |
1988年 | 220篇 |
1987年 | 138篇 |
1986年 | 101篇 |
1985年 | 89篇 |
1984年 | 59篇 |
1983年 | 35篇 |
1982年 | 42篇 |
1981年 | 28篇 |
1980年 | 22篇 |
1979年 | 13篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1945年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
931.
Dynamic surface control-backstepping based impedance control for 5-DOF flexible joint robots 总被引:1,自引:0,他引:1
A new impedance controller based on the dynamic surface control-backstepping technique to actualize the anticipant dynamic
relationship between the motion of end-effector and the external torques was presented. Comparing with the traditional backstepping
method that has “explosion of terms” problem, the new proposed control system is a combination of the dynamic surface control
technique and the backstepping. The dynamic surface control (DSC) technique can resolve the “explosion of terms” problem that
is caused by differential coefficient calculation in the model, and the problem can bring a complexity that will cause the
backstepping method hardly to be applied to the practical application, especially to the multi-joint robot. Finally, the validity
of the method was proved in the laboratory environment that was set up on the 5-DOF (degree of freedom) flexible joint robot.
Tracking errors of DSC-backstepping impedance control that were 2.0 and 1.5 mm are better than those of backstepping impedance
control which were 3.5 and 2.5 mm in directions X, Y in free space, respectively. And the anticipant Cartesian impedance behavior and compliant behavior were achieved successfully
as depicted theoretically. 相似文献
932.
武器装备RMS试验与评价是提高装备的战备完好性、提升我军装备作战性能的重要手段。本文引进了美军在RMS试验与评价方面先进的理论,分别分析了RMS试验与评价的过程、内容、组织机构和特点。最后结合我军的实际情况,总结了我军在RMS试验与评价方面的一些问题,并得出了几点启示,对我军今后开展装备RMS试验与评价工作提供借鉴和参考。 相似文献
933.
Based on the production practice of medium carbon thin slabs in the CSP plant,the reasons and influencing factors for the formation of longitudinal cracks were investigated,and some industrial measures were taken to eliminate the cracks.The results show that the efficient solutions to reduce longitudinal cracks are improving the performance of the mold powder,stabilizing the mold heat flux,and maintaining a proper taper of the mold during casting.Proper pouring temperature and secondary cooling also play... 相似文献
934.
此文以京剧戏衣中的"旗装"为例,探讨了它演变的过程和演变背后的契因,目的在于通过服饰--这种无声的戏曲发展史--反思了京剧的审美进程,也辉映出其在20世纪--京剧真正意义的黄金时代--的发展历程. 相似文献
935.
本文是在国际服饰文化与教育研讨会期间,本栏目主持人、我校服装艺术与工程学院讲师孙雪飞对日本著名时装设计师小筱弘子进行访谈的整理. 相似文献
936.
Xiao-ming Liu ) Heng-hu Sun ) Xiang-peng Feng ) Na Zhang ) ) School of Resource Safety Engineering China University of Mining & Technology Beijing China ) School of Engineering Computer Science University of the Pacific Stockton CA USA ) Shougang Environmental Protection Industry Department Beijing China ) Department of Civil Environmental Engineering University of Wisconsin Madison WI USA 《北京科技大学学报(英文版)》2010,17(1):108-115
A systematic study was conducted to comprehend the mechanism of thermal activation of silica-alumina materials by using 29 Si and 27 Al magnetic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy.The reaction performance of silica-alumina-based materials with different molar ratios of Si/Al,which were thermally activated,was also investigated.With the increase in calcining temperature,the coordination of Al in metakaolin becomes four,five,and six firstly,and then transforms completely to four ... 相似文献
937.
The effects of chromium on the corrosion and the electrochemical behaviors of ultra high strength steels were studied by the salt spray test and electrochemical methods. The results show that ultra high strength steels remain martensite structures and have anodic dissolu-tion characteristic with an increase of chromium content There is no typical passive region on the polarization curves of an ultra high strength stainless steel, AerMet 100 steel, and 300M steel However, chromium improves the corrosion resistance of the stainless steel re-markably. It has the slowest corrosion rate in the salt spray test, one order of magnitude less than that of AerMet 100 and 300M steels. With the increase of chromium content, the polarization resistance becomes larger, the corrosion potential shifts towards the positive direction with a value of 545 mV, and the corrosion current density decreases in electrochemical measures in 3.5wr% NaCl solutions. Because of the higher content of chromium, the ultra high strength stainless steel has a better corrosion resistance than AerMet 100 and 300M steels. 相似文献
938.
质量关系着整个工程的成败,也关系到国家和人民的生命财产安全。因此,质量管理在建筑工程实施中至关重要。如何建立运行质量保证体系和管理规章制度、加强操作人员和施工原材料的基础性、优化施工方法、重视环境等,是质量管理必须解决的问题。 相似文献
939.
本文首先介绍了开关磁阻电动机的工作原理及常用控制方式,有电流斩波、脉宽调制方式和角度位置控制方式,其次介绍了开关磁阻电动机调速系统的基本组成,其中对功率变换器、位置检测器、电流检测器、控制器的作用进行了简单的阐述,最后介绍了开关磁阻电动机调速系统的应用。 相似文献
940.
康明 《武汉理工大学学报(材料科学英文版)》2009,24(1):20-24
Ca(NO3)2·4H2O, Eu(NO3)3 and H2C2O4·2H2O were adopted to synthesize CaO: Eu3+ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3+ doping concentration on the phosphor structure and its luminescent properties were investigated by TG-SDTA, XRD, and PL-PLE.
The results confirm that the Eu3+ ions as luminescent centers substitutes Ca2+ sites without changing the crystal structure of cubic CaO. The optimum calcination temperature and the optimum concentration
of Eu3+ are 1 100 ° and 1 mol%, respectively, under which the best crystallinity and highest PL intensity appeared. The maximum emission
wavelength is 592 nm (5D0→7F1) which is excited by xenon lamp with the wavelength of 200–280 nm, indicating that the Eu3+ ion mainly locates in the symmetric position (Oh) in the crystal lattice of CaO.
Funded by the Science and Technology Bureau of Sichun Province(No. 2006J13-059) and Education Bureau of Sichun Province (No.
2006A094) 相似文献