全文获取类型
收费全文 | 1418篇 |
免费 | 192篇 |
国内免费 | 66篇 |
专业分类
电工技术 | 88篇 |
综合类 | 103篇 |
化学工业 | 151篇 |
金属工艺 | 15篇 |
机械仪表 | 91篇 |
建筑科学 | 119篇 |
矿业工程 | 13篇 |
能源动力 | 12篇 |
轻工业 | 333篇 |
水利工程 | 30篇 |
石油天然气 | 24篇 |
武器工业 | 8篇 |
无线电 | 373篇 |
一般工业技术 | 162篇 |
冶金工业 | 28篇 |
原子能技术 | 16篇 |
自动化技术 | 110篇 |
出版年
2024年 | 11篇 |
2023年 | 45篇 |
2022年 | 68篇 |
2021年 | 84篇 |
2020年 | 75篇 |
2019年 | 60篇 |
2018年 | 54篇 |
2017年 | 70篇 |
2016年 | 70篇 |
2015年 | 75篇 |
2014年 | 95篇 |
2013年 | 88篇 |
2012年 | 129篇 |
2011年 | 106篇 |
2010年 | 63篇 |
2009年 | 65篇 |
2008年 | 71篇 |
2007年 | 69篇 |
2006年 | 60篇 |
2005年 | 50篇 |
2004年 | 42篇 |
2003年 | 26篇 |
2002年 | 49篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 14篇 |
1997年 | 17篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1676条查询结果,搜索用时 31 毫秒
31.
收集了某个谐波污染较重的110 kV变电所的实测数据,量化分析了并联电容器装置在各种负荷条件、运行方式下受到谐波影响的情况,指出其在运行中存在烧毁的危险性,并由此提出保证电容器装置安全运行、提高电能质量的治理措施。 相似文献
32.
33.
34.
C. Fourcade-Dutin 《Journal of Modern Optics》2017,64(5):500-506
We numerically investigate the modulation instability generated in a dispersion oscillating fibre pumped by a chirped pulse with a broad bandwidth. We highlight that the side bands are wide, not symmetric in frequency about the pump and several instantaneous side bands can spectrally overlap with each other in one side, while they are well located in the other side. We also show that the spectral distribution can be intuitively explained with an analogy in which the fibre is pumped by a tuneable continuous wave. 相似文献
35.
36.
《Food Control》2014
This study describes for the first time the application of helicase-dependent amplification (HDA) to authenticate botanical species and processed products. Asian ginseng (Panax ginseng) and American ginseng (Panax quinquefolius) are consumed worldwide as functional food and health remedies. The two herbs share similar morphological appearance but have different pharmacological effects. In this work, a novel isothermal amplification mediated DNA method was applied to authenticate the two ginseng species. Internal control and P. ginseng specific primers were designed based on the ribosomal external transcribed spacer (ETS) region. The amplification results were confirmed by real-time monitoring, gel electrophoresis and DNA sequencing. The screened retail samples included dried ginseng root, ginseng powder, ginseng tea granules as well as a four-herb formulation. Our HDA protocol worked well on both purified DNA and crude water extract. In conclusion, HDA is a highly sensitive and specific approach for differentiating Asian ginseng from American ginseng and it has the potential for on-site authentication of herbal products. 相似文献
37.
Asymmetric autocatalysis with amplification of enantiomeric excess is found in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde using pyrimidyl alkanol as an asymmetric autocatalyst. Asymmetric autocatalysis has been employed as a method for clarifying the origin of homochirality. Circularly polarized light, inorganic chiral crystals and statistical fluctuation of enantiomeric imbalance act as chiral initiators in asymmetric autocatalysis to afford highly enantioenriched products. We have investigated asymmetric autocatalysis using chiral crystals formed from achiral and racemic compounds as an origin of chirality. Absolute control of the crystal chirality of cytosine was achieved by the removal of crystal water. Enantioselective carbon-carbon bond formation at the enantiotopic crystal face of aldehydes was established using diisopropylzinc vapor. In addition, asymmetric autocatalysis triggered by chiral compounds arising from H, C and O isotope substitution has been achieved. 相似文献
38.
Chi‐Wu Mao 《中国工程学刊》2013,36(3):179-185
Abstract A special method has been found and used for the rapid finding of the contours in a natural image. A reference contour image was thus formed by a subjective test. The reference contour image can be further adopted as an objective criterion for other contour‐finding algorithms. 相似文献
39.
《Measurement》2014
Bridge-type micro-displacement amplifier with flexure hinges is a classic displacement amplification mechanism. Existing theoretic models cannot predict its amplification ratio and input stiffness accurately and make it very difficult to confirm the amplifier’s performance and error compensation by means of these models, which is very significant in ultra-precision positioning. This paper focuses on the development of design equations that can accurately calculate the ideal displacement amplification ratio and input stiffness of the amplifier based on the thought of statically indeterminate structure. Force Method, Maxwell–Mohr Method, principle of superposition and deformation compatibility are used together to establish uncanonical linear homogeneous equations. The analytical results are verified by FEA simulations. The influence of the geometric parameters on the amplifier performance is investigated. It is noted that amplifier performance is more sensitive to the longitudinal distance of flexure hinges. Besides, two same-sized amplifiers with the opposite output directions can be clearly differentiated by these equations. 相似文献
40.
新型瓦斯检测系统硬件设计 总被引:1,自引:1,他引:0
针对矿用瓦斯检测系统中使用传感器的特点以及工作环境,加入温度、湿度数据采集环节,在软件算法方面提高测量准确度。设计中主要采用高共模抑制比的差分放大电路、开关电容滤波器提高信号源的精确度,同时抑制电源噪声以提高系统抗干扰性。 相似文献