全文获取类型
收费全文 | 22781篇 |
免费 | 883篇 |
国内免费 | 83篇 |
专业分类
电工技术 | 293篇 |
综合类 | 44篇 |
化学工业 | 5146篇 |
金属工艺 | 478篇 |
机械仪表 | 460篇 |
建筑科学 | 1719篇 |
矿业工程 | 160篇 |
能源动力 | 686篇 |
轻工业 | 2137篇 |
水利工程 | 182篇 |
石油天然气 | 56篇 |
武器工业 | 1篇 |
无线电 | 1483篇 |
一般工业技术 | 4162篇 |
冶金工业 | 2769篇 |
原子能技术 | 137篇 |
自动化技术 | 3834篇 |
出版年
2023年 | 152篇 |
2022年 | 308篇 |
2021年 | 533篇 |
2020年 | 312篇 |
2019年 | 327篇 |
2018年 | 493篇 |
2017年 | 425篇 |
2016年 | 531篇 |
2015年 | 480篇 |
2014年 | 689篇 |
2013年 | 1506篇 |
2012年 | 1081篇 |
2011年 | 1518篇 |
2010年 | 1092篇 |
2009年 | 1043篇 |
2008年 | 1265篇 |
2007年 | 1098篇 |
2006年 | 939篇 |
2005年 | 865篇 |
2004年 | 774篇 |
2003年 | 688篇 |
2002年 | 660篇 |
2001年 | 392篇 |
2000年 | 377篇 |
1999年 | 412篇 |
1998年 | 409篇 |
1997年 | 371篇 |
1996年 | 340篇 |
1995年 | 295篇 |
1994年 | 301篇 |
1993年 | 297篇 |
1992年 | 250篇 |
1991年 | 214篇 |
1990年 | 201篇 |
1989年 | 230篇 |
1988年 | 186篇 |
1987年 | 177篇 |
1986年 | 174篇 |
1985年 | 239篇 |
1984年 | 214篇 |
1983年 | 184篇 |
1982年 | 168篇 |
1981年 | 195篇 |
1980年 | 130篇 |
1979年 | 147篇 |
1978年 | 143篇 |
1977年 | 127篇 |
1976年 | 138篇 |
1975年 | 120篇 |
1974年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
992.
Noshin Omar Hamid Gualous Justin Salminen Grietus Mulder Ahmadou Samba Yousef Firouz Mohamed Abdel Monem Peter Van den Bossche Joeri Van Mierlo 《Journal of Applied Electrochemistry》2014,44(4):509-522
This paper represents an assessment of the main ageing phenomena in electrical double-layer capacitors (EDLCs). In this study the cycle life of the EDLC cells with a rated capacitance of 1,600 F has been investigated at different ambient temperatures and current rates. From the experimental results we can observe that the impact of the high ambient temperature is significant on the cycle life of the cells. Moreover, the results also show the negative impact of the current rate. The internal resistance tests showed that the increase of the resistance is much higher than the decrease of the capacitance. Thus, the ageing of the EDLC during cycling was clearly non-linear. Further the EIS measurements indicated the higher increase of the imaginary part of the impedance at low frequencies during cycling, which indicates the capacitance fade. 相似文献
993.
Plasma electrolytic oxidation was undertaken on Zircaloy-4 in alkaline silicate and pyrophosphate electrolytes, with a square waveform AC current regime. The resultant coatings were examined using scanning electron spectroscopy, X-ray diffraction and nanoindentation. The coatings formed in silicate electrolyte comprised mainly a porous inner layer and a more compact outer layer, with characteristic solidification structures being evident following prolonged treatment. The coatings contained monoclinic and tetragonal ZrO2, the latter being mainly present in the outer layer, which was of hardness up to ∼8 GPa. In contrast, extensively cracked coatings resulted from use of pyrophosphate electrolyte; the coating integrity was improved by the addition of silicate to the pyrophosphate electrolyte. The different morphologies of the coatings appeared to be related to the differing nature of the microdischarges and to the incorporation of silicon species that enhanced the formation of t-ZrO2. 相似文献
994.
Peter W. R. Beaumont 《The Journal of Adhesion》1974,6(1):107-137
This paper presents a review of the fracture processes which occur in brittle thermosetting resins containing long strong fibers of carbon, boron and glass. Important material variables affecting the fracture behavior of the fibrous composite include fiber strength and strength of the fiber-matrix interface. Other parameters which must be considered include component geometry, environment, loading mode and nondestructive inspection capability. The effects of microstructural features including fiber volume fraction, together with a consideration of the fiber-resin interface are discussed in relation to the fracture stress and toughness of the composite material. The influence of the fiber-resin interface and environment on slow crack growth in carbon fiber-reinforced epoxy resin is also reviewed. 相似文献
995.
996.
Fritz Theil Hans Schick Peter Nedkov Monika Bhme Barbara Hfner Sigfrid Schwarz 《Advanced Synthesis \u0026amp; Catalysis》1988,330(6):893-899
Subtilisin DY as well as alkaline protease from Bacillus licheniformis 41 p catalyze the hydrolysis of (1SR, 5RS, 6RS, 7RS)-7-acetoxy-6-acetoxymethyl-2-oxabicyclo[3.3.0]octan-3-one ( rac-1 ) with practically useful enantio- and regioselectivity. Under the hitherto found optimal conditions (1S, 5R, 6R, 7R)-7-hydroxy-6-hydroxymethyl-2-oxabicyclo[3.3.0]octan-3-one ( 4 ), an important intermediate in prostaglandin syntheses, could be prepared in a yield of 16% with an enantiomeric excess of 99%. The enantiomer ( ent-4 ) was obtained with the same enantiomeric excess in 20% yield. The chemical yields are related to the racemic starting material rac-1 . 相似文献
997.
广域保护中基于能量守恒原理的母线及输电线差动保护 总被引:3,自引:3,他引:0
提出一种基于能量守恒原理的纵联差动保护,对线路两端或母线各端的有功功率进行比较,若各端功率的和超出整定值,则判定为区内故障。在典型400 kV输电系统模型上,运用MATLAB仿真软件对所提出的原理进行了仿真验证。仿真结果表明,该方法比传统电流比率差动保护更加可靠且计算量小,因而可缩短动作时间。该方法能检测所有故障类型,适应于超高压远距离输电线路。 相似文献
998.
能效和中国的能源未来 总被引:1,自引:0,他引:1
1中国的经济增长、能源需求和对煤的依赖美国自然资源保护委员会(NRDC)深切关注能源问题,因为我们每一个人都是地球公民,我们在共享同一个地球、同一个自然环境。科学研究不断表明,我们这个星球上的 相似文献
999.
Sujin Cho On Hwang Iljea Lee Gayoung Lee Donghyuck Yoo Gilson Khang Peter M. Kang Dongwon Lee 《Advanced functional materials》2012,22(19):4038-4043
Hydrogen peroxide (H2O2) is one of essential oxygen metabolites in living organisms, but is generated in large amounts during inflammatory responses. Therefore, H2O2 has great potential as diagnostic and therapeutic markers of several inflammatory and life‐threatening diseases. Here, chemiluminescent and antioxidant micelles are reported as novel theranostic agents for H2O2‐associated inflammatory diseases. The chemiluminescent micelles composed of amphiphilic block copolymer Pluronic F‐127, hydroxybenzyl alcohol‐incorporated copolyoxalate (HPOX) and fluorescent dyes perform peroxalate chemiluminescence reactions to detect H2O2 as low as 100 nM and image H2O2 generated in inflamed mouse ankles. The micelles encapsulating HPOX reduce the generation of reactive oxygen species in lipopolysaccharide (LPS)‐activated macrophages by scavenging overproduced H2O2 and releasing antioxidant hydroxybenzyl alcohol (HBA). They also exert inhibitory effects on H2O2‐induced apoptosis. HPOX‐based chemiluminescent and antioxidant micelles have great potential as a theranostic agent for H2O2‐associated inflammatory diseases. 相似文献
1000.