全文获取类型
收费全文 | 2708篇 |
免费 | 3286篇 |
国内免费 | 365篇 |
专业分类
电工技术 | 944篇 |
综合类 | 1084篇 |
化学工业 | 147篇 |
金属工艺 | 459篇 |
机械仪表 | 188篇 |
建筑科学 | 251篇 |
矿业工程 | 1093篇 |
能源动力 | 27篇 |
轻工业 | 55篇 |
水利工程 | 328篇 |
石油天然气 | 367篇 |
武器工业 | 93篇 |
无线电 | 333篇 |
一般工业技术 | 232篇 |
冶金工业 | 128篇 |
原子能技术 | 50篇 |
自动化技术 | 580篇 |
出版年
2024年 | 1篇 |
2023年 | 355篇 |
2022年 | 889篇 |
2021年 | 877篇 |
2020年 | 644篇 |
2019年 | 289篇 |
2018年 | 168篇 |
2017年 | 131篇 |
2016年 | 265篇 |
2015年 | 126篇 |
2014年 | 29篇 |
2013年 | 120篇 |
2012年 | 47篇 |
2011年 | 77篇 |
2010年 | 99篇 |
2009年 | 188篇 |
2008年 | 85篇 |
2007年 | 172篇 |
2006年 | 244篇 |
2005年 | 256篇 |
2004年 | 201篇 |
2003年 | 129篇 |
2002年 | 71篇 |
2001年 | 311篇 |
2000年 | 271篇 |
1999年 | 200篇 |
1998年 | 31篇 |
1997年 | 25篇 |
1996年 | 14篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有6359条查询结果,搜索用时 31 毫秒
101.
L. H. Lang D. C. Kang S. H. Zhang Z. R. Wang S. J. Yuan K. B. Nielsen J. Dancket ) Department of Materials Engineering Harbin Institute of Technology Harbin China ) Aalberg University Denmark 《金属学报(英文版)》2000,13(2):476-480
1.~nonHydridapawhcdeepdrawing(HDD)belongstothefieldofsheetmetalfoeingandcanbeaPPliedinthefieldofautomotive,aerospace,drilitaryindustryetc.Ithasbeenrecognizedwidelyintheworld["'j.Fig.Ishowsitsprinciple:TheliqUidthatisfilledinthe~ngdiecavitywillbepressedwhenthepunchgoesdownsothattheeffectoffrictionkeepingandoverflowlubricatingcanbeformed,astherestilt,thefoeinglicitofsheetmetalwillbeimprovedareailvandthegualitVofthefinishedpartswillbeup~ed.BecauseofmanyadvantagesofHDDprocees,ithasbeenwidelys… 相似文献
102.
XIE Changsheng SUN Peizhen ZHAO Jiansheng CHEN Yuqiu Huazhong University of Science Technology Wuhan China XIE Changsheng Associate Professor Department of Mechanical Engineering No. Huazhong University of Science Technology Wuhan China 《金属学报(英文版)》1990,3(1):52-57
The microstructures of Fe-Mn-Ni-Cr steels with medium carbon and the effect of alloy ele-ments on them have been investigated by means of X-ray diffraction quantitative phase ana-lyses,metallography and hardness tests.The volume fraction of martensite in steels quenchedat 1100℃ can be expressed as:f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)Based on this expression,the quasi-equilibrium microstructure diagram has been obtained.Itis shown that the effect of Mn on the austenite stability is greater than that of Ni.The equiva-lent [Ni]=2.104Mn+Ni and equivalent [Cr]=Cr+Mo+V.The driving force for martensite transformation at M_s point has been calculated to hedrastically decreased by element Mn. 相似文献
103.
Advances in the research of nitrogen containing stainless steels 总被引:1,自引:0,他引:1
The current status of nitrogen containing stainless steels at home and aboard has been introduced. The function and existing forms of nitrogen in the stainless steels, influence of nitrogen on mechanical properties and anti-corrosion properties as well as the application of nitrogen containing cast stainless steels were discussed in this paper. It is clear that nitrogen will be a potential and important alloying element in stainless steels. And Argon Oxygen Decarbonization (AOD) refining can provide an advanced manufacture process for nitrogen containing stainless steels with ultra-low- carbon and high cleanliness. 相似文献
104.
YANG Sheng LU Xiaoquan XUE Zhonghua FENG Xiaoqiang WANG Xiaofeng) Department of Chemistry Tianshui Teacher College Tianshui China) Institute of Chemistry Northwest Normal University Lanzhou China 《稀有金属(英文版)》2003,22(4)
A differential pulse voltammetric method was developed for the sensitive and selective determination of Cu(Ⅱ) at 4-methoxy-2,6-bis(3,5-dimethylpyrazoyl)-l,3,5-triazine modified carbon paste electrode in 0.05 mol/L KHC8H4O4 solution (pH = 4.02). The oxidation peak of Cu(Ⅱ) was observed at 0.065 V(vs Ag/AgCl) by scanning the potential in positive direc-tion. The analysis procedure consisted of an open circuit accumulation step in stirred sample solution. It was followed by medium exchange to a clean solution and subsequently an anodic potential scan was affected to obtain the voltammetric peak. The current was proportional to the concentration of the Cu(Ⅱ) ion in a range of 1× 10-7-1×10-4 mol/L for 6 min accumulation; the most of metal ions did not interfere with the determination. The developed method was applied to Cu(Ⅱ) determination in coal-ash sample, the results agreed with that of atomic adsorption spectroscopy(AAS). 相似文献
105.
Jing Jiang~) Jing-she Li~) Hua-jie Wu~) Shu-feng Yang~) Tao Li~) Hai-yan Tang~) ) School of Metallurgical Ecological Engineering University of Science Technology Beijing Beijing China ) Engineering Research Institute China 《北京科技大学学报(英文版)》2010,17(2):143-148
Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments.It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence inhibitor.It dramatically increases the peak concentration time,and greatly decreases the dead volume,and reduces the minimum residence time.The gas blowing location,gas flow rate,and porous plug area greatly influence the flow characteristics in the tundish;the gas blowing location near t... 相似文献
106.
Ming-ji Huang ) Xiu-ping Dong ) Guo-quan Liu ) ) School of Mechanical Engineering University of Science Technology Beijing Beijing China ) School of Mechanical Engineering Beijing Technology Business University Beijing China ) School of Materials Science Engineering China 《北京科技大学学报(英文版)》2010,17(1):75-79
Based on the analysis of the preparation of metal rubber (MR) and two pivotal hypotheses,the uniform distribution and the unaltered topological structure of wires in the radial direction of columns in the punch process,a 3D parametrical model was established based on four approaches:helix-making,planar roughcast-weaving,planar roughcast-rolling,and 3D roughcast punching.In the modeling process,5 lattice types of weave patterns in planar roughcast were put forward,and 10 quantificational modeling parameters ... 相似文献
107.
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
108.
Bai-song Liu ) Guo-sen Zhu ) Huan-xi Li ) Ben-hai Li ) Yang cui ) Ai-min Cui ) ) School of Material Science Engineering Beihang University Beijing China ) Shougang Research Institute of Technology Beijing China ) Qian'an Iron Steel Company Qian'an China 《北京科技大学学报(英文版)》2010,17(1):22-27
The decarburization behaviors of ultra low carbon steel in a 210-t RH vacuum degasser were investigated under practical operating conditions.According to the apparent decarburization rate constant (KC) calculated by the carbon content in the samples taken from the hot melt in a ladle at an interval of 1-2 min,it is observed that the total decarburization reaction period in RH can be divided into the quick decarburization period and the stagnant decarburization period,which is quite different from the tradit... 相似文献
109.
Yong-jin Yang ) Ke-wei Gao ) Chang-feng Chen ) ) School of Materials Science Engineering University of Science Technology Beijing Beijing China ) Department of Materials Science Technology China University of Petroleum Beijing China 《北京科技大学学报(英文版)》2010,17(1):58-62
The effect of hydrogen on the fracture behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing (SSRT).Hydrogen was introduced into the sample by electrochemical charging.The results show that surface microcracks form gradually during aging at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm 2 for 24 h.SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density inc... 相似文献
110.
Particle simulation of the failure process of brittle rock under triaxial compression 总被引:1,自引:0,他引:1
Ming Xia ) Ke-ping Zhou) ) School of Resources Safety Engineering Central South University Changsha China ) Ma’anshan Institute of Mining Research Ma’anshan China 《北京科技大学学报(英文版)》2010,17(5):507-513
In order to investigate the failure process of brittle rock under triaxial compression through both experimental and numerical approaches, the particle simulation method was used in numerical simulations and the simulated results were compared with those of the experiment. The numerical simulation results, such as fracture propagation, microcrack distribution, stress-strain response, and damage patterns, were discussed in detail. The simulated results under various confining pressures (0-60 MPa) are in good... 相似文献