全文获取类型
收费全文 | 74828篇 |
免费 | 2976篇 |
国内免费 | 1959篇 |
专业分类
电工技术 | 2219篇 |
综合类 | 1973篇 |
化学工业 | 12179篇 |
金属工艺 | 4604篇 |
机械仪表 | 3273篇 |
建筑科学 | 3858篇 |
矿业工程 | 761篇 |
能源动力 | 2459篇 |
轻工业 | 4306篇 |
水利工程 | 833篇 |
石油天然气 | 3190篇 |
武器工业 | 210篇 |
无线电 | 7960篇 |
一般工业技术 | 14888篇 |
冶金工业 | 8908篇 |
原子能技术 | 1214篇 |
自动化技术 | 6928篇 |
出版年
2023年 | 511篇 |
2022年 | 903篇 |
2021年 | 1419篇 |
2020年 | 1115篇 |
2019年 | 1090篇 |
2018年 | 1449篇 |
2017年 | 1585篇 |
2016年 | 1590篇 |
2015年 | 1634篇 |
2014年 | 2238篇 |
2013年 | 4225篇 |
2012年 | 3340篇 |
2011年 | 3987篇 |
2010年 | 3258篇 |
2009年 | 3555篇 |
2008年 | 3346篇 |
2007年 | 3462篇 |
2006年 | 3147篇 |
2005年 | 2796篇 |
2004年 | 2267篇 |
2003年 | 2043篇 |
2002年 | 2027篇 |
2001年 | 1922篇 |
2000年 | 1857篇 |
1999年 | 1968篇 |
1998年 | 3051篇 |
1997年 | 2426篇 |
1996年 | 2195篇 |
1995年 | 1609篇 |
1994年 | 1246篇 |
1993年 | 1221篇 |
1992年 | 904篇 |
1991年 | 796篇 |
1990年 | 745篇 |
1989年 | 636篇 |
1988年 | 493篇 |
1987年 | 493篇 |
1986年 | 436篇 |
1985年 | 432篇 |
1984年 | 348篇 |
1983年 | 331篇 |
1982年 | 333篇 |
1981年 | 315篇 |
1980年 | 367篇 |
1979年 | 351篇 |
1978年 | 301篇 |
1977年 | 425篇 |
1976年 | 641篇 |
1975年 | 313篇 |
1973年 | 319篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
In Malaysia, no long-term daylight data are measured. It was only recently that the need to measure the availability of daylight became urgent when the importance of daylighting in buildings was rediscovered. The hourly daylight availability has been simulated for the Malaysian sky using daylight modelling techniques based on empirical and measured solar irradiation and cloud cover data. This paper presents the techniques involved in producing exterior illuminance data. These data were then compared with measured illuminance at Shah Alam and Bangi, Malaysia. The global illuminance levels are generally high, with values exceeding 80,000 lux at noon during the months when solar irradiation is highest. Even during the months when the ground receives less solar irradiation, the peak illuminance can reach 60,000 lux. Applications and uses of such data are in daylighting design, both for visual and thermal comfort, task illuminance and energy-conscious design of buildings. Recommendations are made at the end of the paper on the various climatic data that are required to be measured for overall daylighting design applications. 相似文献
153.
A novel combline filter is proposed for cellular‐radio base stations. The Q‐factor is significantly improved. The eigenvalue equation is expressed with the single‐team approximation in the gap region of the combline resonator. A two‐pole combline filter is designed. The calculation, simulation, and experiment results are presented and are in good agreement. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. 相似文献
154.
提出企业培训中心的本质特征,并以此为基点阐述企业培训中心的六个主要特征;通过对企业培训中心的使命、培训对象的确定、培养目标、培训内容、组织设置、组织发展的分析,力求揭示企业培训中心组织构建和发展的自身规律。 相似文献
155.
156.
Sung D. Kwon Sung J. Song Dong H. Bae Young Z. Lee 《Journal of Mechanical Science and Technology》2002,16(9):1084-1092
The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward
radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency
dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded
specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual
stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of
the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris’ law that can predict the
crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound
as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion. 相似文献
157.
158.
关于广义函数δ(x)的讨论 总被引:1,自引:0,他引:1
沈永朝 《电气电子教学学报》2002,24(1):28-31
本文应用《电气子教学学报》之邀约而写,旨在针对一些读者对该韩过去刊出的有关广义函数δ(x)的文章中的质疑,从数学角度提供一些有助于正确认识、处理和运用广义函数的辅助材料。 相似文献
159.
D. C. Peets R. Liang C. Stock W. J. L. Buyers Z. Tun L. Taillefer R. J. Birgeneau D. A. Bonn W. N. Hardy 《Journal of Superconductivity and Novel Magnetism》2002,15(6):531-534
We have grown cubic centimeter-size crystals of YBa2Cu3O x suitable for neutron studies, by a top-seeded melt-growth technique. Growth conditions were optimized with an eye toward maximizing phase purity. It was found that the addition of 2% Y2BaCuO5 and 0.5% Pt (by mass) were required to prevent melt loss and to obtain the highest crystallinity. A neutron diffraction study on a mosaic of six such crystals found that the final Y2BaCuO5 concentration was 5%, while other impurity phases comprised less than 1% by volume. The oxygen content was set to x = 6.5, the crystals were detwinned, and then carefully annealed to give the well-ordered ortho-II phase. The neutron study determined that 70% of the mosaic's volume was in the majority orthorhomic domain. The neutron (006) and (110) rocking curve widths were ~1° per crystal and ~2.2° for the mosaic, and the oxygen chain correlation lengths were >100 Å in the a- and b-directions and ~50 Å in the c-direction. 相似文献
160.
介绍了天线近场测量的基本原理和HD-1型平面近场测试系统,并对近场测量在实际天线测试中的应用情况、发展方向和应用前景等作了简单的描述。 相似文献