全文获取类型
收费全文 | 83682篇 |
免费 | 7550篇 |
国内免费 | 3988篇 |
专业分类
电工技术 | 5192篇 |
技术理论 | 7篇 |
综合类 | 5888篇 |
化学工业 | 14030篇 |
金属工艺 | 4345篇 |
机械仪表 | 5396篇 |
建筑科学 | 6918篇 |
矿业工程 | 2550篇 |
能源动力 | 2520篇 |
轻工业 | 5895篇 |
水利工程 | 1609篇 |
石油天然气 | 4489篇 |
武器工业 | 749篇 |
无线电 | 9785篇 |
一般工业技术 | 9753篇 |
冶金工业 | 3766篇 |
原子能技术 | 985篇 |
自动化技术 | 11343篇 |
出版年
2024年 | 445篇 |
2023年 | 1576篇 |
2022年 | 2729篇 |
2021年 | 3695篇 |
2020年 | 2722篇 |
2019年 | 2351篇 |
2018年 | 2552篇 |
2017年 | 2799篇 |
2016年 | 2480篇 |
2015年 | 3389篇 |
2014年 | 4261篇 |
2013年 | 5028篇 |
2012年 | 5529篇 |
2011年 | 5675篇 |
2010年 | 5254篇 |
2009年 | 5040篇 |
2008年 | 4770篇 |
2007年 | 4410篇 |
2006年 | 4552篇 |
2005年 | 3788篇 |
2004年 | 2588篇 |
2003年 | 2248篇 |
2002年 | 2313篇 |
2001年 | 2022篇 |
2000年 | 1982篇 |
1999年 | 2061篇 |
1998年 | 1610篇 |
1997年 | 1388篇 |
1996年 | 1330篇 |
1995年 | 1028篇 |
1994年 | 889篇 |
1993年 | 635篇 |
1992年 | 529篇 |
1991年 | 395篇 |
1990年 | 296篇 |
1989年 | 247篇 |
1988年 | 175篇 |
1987年 | 107篇 |
1986年 | 79篇 |
1985年 | 60篇 |
1984年 | 42篇 |
1983年 | 34篇 |
1982年 | 40篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 9篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1959年 | 5篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Junwei?Xie Yurong?Shi Feng?ZhangEmail author Guoqiang?LiEmail author 《Journal of Materials Science》2016,51(16):7471-7479
993.
994.
995.
996.
997.
A method for measuring the multi-wavelength emissivity of a steel surface is proposed, and an applicable experimental apparatus is designed. Multi-wavelength radiant energy emitted from a sample was measured using a fiber-optic spectrometer and its temperature measured using a NiCrSi/NiSiMg thermocouple. Utilizing the unique vacuum control and background noise-shielding systems, we investigated the multi-wavelength emissivity of GCr15 steel at three different degrees of surface oxidation at temperatures ranging from 1000 \(^{\circ }\)C to \(1100\,^{\circ }\)C. The experimental results show that the multi-wavelength (0.7 \(\upmu \)m–0.9 \(\upmu \)m) emissivity increased substantially, from 0.409–0.565 to 0.609–0.702, once the steel was oxidized. In addition, the emissivity increased slightly with increasing temperature, but the trends for emissivity and wavelength were similar. To measure the surface temperature of casting billets based on multi-wavelength thermometry, the functional relationships between emissivity and wavelength at different extents of oxidation were determined. Temperature measurements based on our technique were compared with those from common colorimetric thermometry. Our approach reduced the temperature fluctuation from \(\pm 23\,^{\circ }\)C to \(\pm 3.5\,^{\circ }\)C, indicating that a reliable measurement of the multi-wavelength emissivity of GCr15 steel is obtained using this experimental apparatus. 相似文献
998.
Random and interval variables often coexist. Interval variables make reliability analysis much more computationally intensive. This work develops a new hybrid reliability analysis method so that the probability analysis (PA) loop and interval analysis (IA) loop are decomposed into two separate loops. An efficient PA algorithm is employed, and a new efficient IA method is developed. The new IA method consists of two stages. The first stage is for monotonic limit-state functions. If the limit-state function is not monotonic, the second stage is triggered. In the second stage, the limit-state function is sequentially approximated with a second order form, and the gradient projection method is applied to solve the extreme responses of the limit-state function with respect to the interval variables. The efficiency and accuracy of the proposed method are demonstrated by three examples. 相似文献
999.
Evaporation‐ and Solution‐Process‐Feasible Highly Efficient Thianthrene‐9,9′,10,10′‐Tetraoxide‐Based Thermally Activated Delayed Fluorescence Emitters with Reduced Efficiency Roll‐Off 下载免费PDF全文
1000.
A Significantly Twisted Spirocyclic Phosphine Oxide as a Universal Host for High‐Efficiency Full‐Color Thermally Activated Delayed Fluorescence Diodes 下载免费PDF全文