全文获取类型
收费全文 | 85807篇 |
免费 | 9499篇 |
国内免费 | 5273篇 |
专业分类
电工技术 | 12975篇 |
技术理论 | 13篇 |
综合类 | 6851篇 |
化学工业 | 9553篇 |
金属工艺 | 2878篇 |
机械仪表 | 4000篇 |
建筑科学 | 10517篇 |
矿业工程 | 2292篇 |
能源动力 | 12869篇 |
轻工业 | 2739篇 |
水利工程 | 1552篇 |
石油天然气 | 2711篇 |
武器工业 | 852篇 |
无线电 | 9581篇 |
一般工业技术 | 8936篇 |
冶金工业 | 3851篇 |
原子能技术 | 1761篇 |
自动化技术 | 6648篇 |
出版年
2024年 | 543篇 |
2023年 | 1814篇 |
2022年 | 2961篇 |
2021年 | 3251篇 |
2020年 | 3470篇 |
2019年 | 3087篇 |
2018年 | 2616篇 |
2017年 | 3196篇 |
2016年 | 3654篇 |
2015年 | 3582篇 |
2014年 | 5881篇 |
2013年 | 5618篇 |
2012年 | 6366篇 |
2011年 | 7124篇 |
2010年 | 5406篇 |
2009年 | 5450篇 |
2008年 | 4923篇 |
2007年 | 5490篇 |
2006年 | 4388篇 |
2005年 | 3494篇 |
2004年 | 2865篇 |
2003年 | 2474篇 |
2002年 | 2109篇 |
2001年 | 1851篇 |
2000年 | 1614篇 |
1999年 | 1285篇 |
1998年 | 1052篇 |
1997年 | 820篇 |
1996年 | 750篇 |
1995年 | 582篇 |
1994年 | 524篇 |
1993年 | 439篇 |
1992年 | 326篇 |
1991年 | 284篇 |
1990年 | 239篇 |
1989年 | 184篇 |
1988年 | 153篇 |
1987年 | 116篇 |
1986年 | 82篇 |
1985年 | 115篇 |
1984年 | 93篇 |
1983年 | 57篇 |
1982年 | 74篇 |
1981年 | 38篇 |
1980年 | 45篇 |
1979年 | 28篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1959年 | 9篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
本文提出励磁电流可自动控制的他励式双高调速系统设计方案。系统在提升特别是在下放重物时,具有较硬的机械性;在负载10-100%的变化范围内,可实现最大偏差Δnmax/nmin100%≤10%,调速范围D≥10;在满载运行条件下,可节约电能80%以上。 相似文献
32.
Packaging engineers need to be able to accurately determine the forces present in the shipping environment in order to protect packaged goods. The purpose of this study was to determine the vertical vibration levels measured in three separate truck-trailer suspension systems; conventional leaf-spring, conventional air-ride and damaged air-ride. The main conclusion reached in this study is that the air-ride suspension when maintained gives lower power density (PD) levels on all road surfaces studied. A damaged air-ride suspension and leaf-spring suspension are very similar in response frequencies, although the damaged air-ride produces higher vibration levels at lower frequencies. 相似文献
33.
反常声电光频谱分析器 总被引:4,自引:1,他引:3
介绍了一种新型的反常声电光频谱分析器,它可以采用外加电压的办法改变器件的中心频率,扩大器件的频带宽度,并改善器件在频带宽度范围内的频率响应特性。用LiNbO3制作了一个60MHz的反常声电光频谱分析器件,测试结果表明,器件中心频率可以由50MHz变到70MHz,频带宽度由原来的26MHz扩大到37MHz。 相似文献
34.
35.
This paper highlights the possibility of inverse gas chromatography for the surface characterization of common fillers (CaCO3, talc, SiO2,) for paints and coatings. Divided solids are described, on the one hand, by the dispersive component of their surface energy and, on the other, by a specific parameter indicating their acid-base interaction potential. The role of the surface morphology at a molecular level is also examined. It is demonstrated that steric effects play an important role in the adsorption of probes on lamellar solids like talc. The consequences of surface treatments as well as examples of practical applications are also reported. 相似文献
36.
In a survey of the practical wind energy resource present in the Tayside Region of Scotland it was estimated that over 1500 km2 of land is suitable for wind energy development in the Region after consideration of a range of physical, technical and institutional factors. Wind speed data for this survey was obtained from the Energy Technology Support Unit (ETSU) UK Wind Speed Data Package. To verify the wind speeds obtained from the ETSU package a representative sample of sites in and around the identified areas of potential in Tayside were modelled for mean annual wind speed using the Wind Atlas Analysis and Application Program (WAsP). The wind speeds for the sites obtained from the WAsP analysis were compared with those obtained from the ETSU UK Wind Speed Data Package and conclusions drawn as to the reliability of the Tayside wind energy survey and the general applicability of the ETSU package for broad wind energy resource assessment. 相似文献
37.
The analysis of recently collected wind data at five sites in Saudi Arabia namely, Dhulum, Arar, Yanbu, Gassim and Dhahran is presented. The five sites represent different geographically and climatologically conditions. The data collected over a period spanned between 1995 and 2002 with different collection periods for each site. Daily, monthly and frequency profiles of the wind speed at the sites showed that Dhulum and Arar sites have higher wind energy potential with annual wind speed average of 5.7 and 5.4 m/s and speeds higher than 5 m/s for 60 and 47% of the time, respectively. The two sites are candidates for remote area wind energy applications. The costal site's, i.e. Yanbu and Dhahran wind speed data indicated that the two sites have lower annual wind speed averages and wind blows at speed higher than 5 m/s during afternoon hours. That makes the two sites candidates for grid connected wind systems for electrical load peak shaving. The data of Gassim site showed that the site has the lowest wind energy potential compared to the others. The annual energy produced by a Nordex N43 wind machine is estimated to be 1080, 990, 730, 454 and 833 MWh for Dhulum, Arar, Yanbu, Gassim and Dhahran, respectively. The analysis showed that the estimated annual energy produced by the machine based on 10 min averaged data is 2.5% higher than the estimated energy based on 30 min averaged data. 相似文献
38.
论述了海洋钻井平台的功率因数及改善功率因数的重要意义和必要性,对实时无功功率动态补偿装置作了介绍,并对实施功率补偿后取得的效果和经济测算作了分析,提出了提高功率因数,进行功率补偿的推广应用建议。 相似文献
39.
Alberto Carpinteri Bernardino Chiaia Simone Puzzi 《Engineering Fracture Mechanics》2007,74(17):2892-2896
Aim of this letter to the Editor is at replying to the criticisms raised by Ba?ant and Yavari [Ba?ant ZP, Yavari A. Is the cause of size effect on structural strength fractal or energetic - statistical? Engng Fract Mech 2005;72:1-31] against the fractal approach to the size-scale effects on the mechanical properties of materials and the concept of the Multi-Fractal Scaling Law presented by Carpinteri [Carpinteri A. Scaling laws and renormalization groups for strength and toughness of disordered materials. Int J Solids Struct 1994;31:291-302]. These criticisms will be analysed thoroughly, showing how they also contain some mistakes and misunderstandings. The presented elucidations should redirect the discussion to a more correct scientific debate. 相似文献
40.