全文获取类型
收费全文 | 66982篇 |
免费 | 5861篇 |
国内免费 | 3035篇 |
专业分类
电工技术 | 3765篇 |
技术理论 | 2篇 |
综合类 | 4339篇 |
化学工业 | 11220篇 |
金属工艺 | 3786篇 |
机械仪表 | 4239篇 |
建筑科学 | 4887篇 |
矿业工程 | 2265篇 |
能源动力 | 1768篇 |
轻工业 | 4283篇 |
水利工程 | 1134篇 |
石油天然气 | 4009篇 |
武器工业 | 561篇 |
无线电 | 8217篇 |
一般工业技术 | 8179篇 |
冶金工业 | 3232篇 |
原子能技术 | 765篇 |
自动化技术 | 9227篇 |
出版年
2024年 | 365篇 |
2023年 | 1168篇 |
2022年 | 1930篇 |
2021年 | 2716篇 |
2020年 | 2064篇 |
2019年 | 1846篇 |
2018年 | 2003篇 |
2017年 | 2214篇 |
2016年 | 2017篇 |
2015年 | 2597篇 |
2014年 | 3213篇 |
2013年 | 3854篇 |
2012年 | 4302篇 |
2011年 | 4729篇 |
2010年 | 3925篇 |
2009年 | 3728篇 |
2008年 | 3564篇 |
2007年 | 3468篇 |
2006年 | 3809篇 |
2005年 | 3182篇 |
2004年 | 2221篇 |
2003年 | 1891篇 |
2002年 | 1673篇 |
2001年 | 1516篇 |
2000年 | 1602篇 |
1999年 | 1769篇 |
1998年 | 1567篇 |
1997年 | 1305篇 |
1996年 | 1171篇 |
1995年 | 977篇 |
1994年 | 859篇 |
1993年 | 590篇 |
1992年 | 441篇 |
1991年 | 382篇 |
1990年 | 273篇 |
1989年 | 219篇 |
1988年 | 197篇 |
1987年 | 129篇 |
1986年 | 104篇 |
1985年 | 63篇 |
1984年 | 33篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 17篇 |
1980年 | 26篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 21篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
针对“资产中心”模式对设备管理系统以及设备编码的要求,设计出松耦合的编码体系,并根据炼油化工企业的特点给出了主要的编码结构。解决了编码层次的固化与设备实际层次结构的多样化之间的矛盾,支持“资产中心”模式下设备管理对信息系统功能的需求。 相似文献
12.
Ultraviolet (UV) disinfection is becoming increasingly popular as an alternative disinfection technology to chlorination in recent years. In this study, we investigated the photoreactivation of Escherichia coli following medium-pressure (MP) UV disinfection of synthetic water by a bench-scale collimated beam apparatus. The UV doses ranged from 1.6 -19.7 mWs/cm2 and photoreactivation was investigated for 6 hours under fluorescent light. In addition, chloramination was applied after UV disinfection to investigate its ability to control photoreactivation. It was found that photoreactivation occurred for all UV doses tested and the increase in bacteria numbers ranged from 0.04 to 1.35 log10. However, the degree of photoreactivation decreased with increased UV doses. Chloramination experiments revealed that the addition of 0.5 mg/l of monochloramine resulted in suppression of photoreactivation for 1 hour only. An increased monochloramine dose of 1 mg/l was found to prevent photoreactivation for the entire duration of the experiment. The results of this study have shown that photoreactivation occurs even after MP UV disinfection, although it is of a lesser extent at higher UV doses. This study has also established that secondary chloramination can effectively suppress and eliminate photoreactivation with a chloramine dose of 1 mg/l. 相似文献
13.
14.
15.
By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed. 相似文献
16.
在语音时域挑选剩余可懂度低的可用置换集合,置换集合是语音TDS系统中不可缺少的重要环节,本文给出了可用置换选取的条件、客观评价标准和方法。 相似文献
17.
18.
Chun Hu Ji Zhao Li G.P. Liu P. Worley E. White J. Kjar R. 《Electron Device Letters, IEEE》1995,16(2):61-63
The effects of the plasma etching process induced gate oxide damages on device's low frequency noise behavior are investigated on MOSFET's fabricated with different field plate perimeter to gate area ratio antennas. Abnormal 1/f noise spectrum with a shoulder centered in the frequency range of 100 and to 1 kHz was frequently observed in small geometry devices, and it is attributable to a nonuniform distribution of oxide traps induced by plasma etching process 相似文献
19.
Assaderaghi F. Chen J. Solomon R. Chian T.-Y. Ko P.K. Hu C. 《Electron Device Letters, IEEE》1991,12(10):518-520
It has been found that the subthreshold currents of fully depleted silicon-on-insulator (SOI) MOSFETs show a transient behavior under certain front-gate and back-gate voltage conditions. The cause of this anomaly is explained, and applications for the phenomenon are pointed out. Particularly, a simple way to measure the silicon film thickness is suggested 相似文献
20.
InGaAs/GaAs(100) multiple-quantum-well-based inverted cavity asymmetric Fabry-Perot modulators are vertically integrated with GaAs/AlGaAs heterojunction phototransistors to yield all-optical photonic switches. The photonic switches using `normally on' modulator pixels exhibit an output on-off ratio of 12:1 with internal optical gain of 4 dB. The photonic switches using `normally off' modulator pixels yield similar contrast and gain, but exhibit intrinsic bistable behavior. The inverted cavity modulators employed permit utilizing the transparency of the GaAs substrate at the operating wavelength and offer advantages for fabricating large arrays for optical signal processing 相似文献