全文获取类型
收费全文 | 2360篇 |
免费 | 328篇 |
国内免费 | 252篇 |
专业分类
电工技术 | 361篇 |
综合类 | 337篇 |
化学工业 | 72篇 |
金属工艺 | 71篇 |
机械仪表 | 188篇 |
建筑科学 | 124篇 |
矿业工程 | 66篇 |
能源动力 | 60篇 |
轻工业 | 44篇 |
水利工程 | 28篇 |
石油天然气 | 106篇 |
武器工业 | 40篇 |
无线电 | 474篇 |
一般工业技术 | 121篇 |
冶金工业 | 67篇 |
原子能技术 | 14篇 |
自动化技术 | 767篇 |
出版年
2024年 | 1篇 |
2023年 | 20篇 |
2022年 | 21篇 |
2021年 | 34篇 |
2020年 | 42篇 |
2019年 | 29篇 |
2018年 | 43篇 |
2017年 | 66篇 |
2016年 | 101篇 |
2015年 | 75篇 |
2014年 | 145篇 |
2013年 | 116篇 |
2012年 | 194篇 |
2011年 | 205篇 |
2010年 | 172篇 |
2009年 | 190篇 |
2008年 | 186篇 |
2007年 | 208篇 |
2006年 | 184篇 |
2005年 | 182篇 |
2004年 | 117篇 |
2003年 | 125篇 |
2002年 | 84篇 |
2001年 | 72篇 |
2000年 | 49篇 |
1999年 | 52篇 |
1998年 | 33篇 |
1997年 | 33篇 |
1996年 | 19篇 |
1995年 | 33篇 |
1994年 | 29篇 |
1993年 | 18篇 |
1992年 | 20篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有2940条查询结果,搜索用时 31 毫秒
1.
The symmetrical and asymmetrical electrodes made of Mg were studied in 0.1-M NaCl electrolyte adjusted at pH 12. The statistical and wavelet methods were employed for analyzing the electrochemical current noise (ECN) signals. The asymmetric configuration was used for electrochemical detection of filiform corrosion on Mg electrode. The real time scale of the dominant transients of the asymmetric electrodes was detected on the basis of the maximum peak in the SDPS plots. The SDPS values of the real time scale crystals of the ECN signals resulting from asymmetrical electrodes increased with the increase in immersion time due to the onset of filiform corrosion. 相似文献
2.
《Ceramics International》2022,48(2):1889-1897
SiC fiber reinforced ceramic matrix composites (SiCf-CMCs) are considered to be one of the most promising materials in the electromagnetic (EM) stealth of aero-engines, which is expected to achieve strong absorption and broad-band performance. Multiscale structural design was applied to SiCf/Si3N4–SiOC composites by construction of micro/nanoscale heterogeneous interfaces and macro double-layer impedance matching structure. SiCf/Si3N4–SiOC composites were fabricated by using SiC fibers with different conductivities and SiOC–Si3N4 matrices with gradient impedance structures to improve impedance matching effectively. Owing to its unique structure, SiCf/Si3N4–SiOC composites (A3-composites) achieved excellent EM wave absorption performance with a minimum reflection coefficient (RCmin) of ?25.1 dB at 2.45 mm and an effective absorption bandwidth (EAB) of 4.0 GHz at 2.85 mm in X-band. Moreover, double-layer SiCf/Si3N4–SiOC with an improved impedance matching structure obtained an RCmin of ?56.9 dB and an EAB of 4.2 GHz at 3.00 mm, which means it can absorb more than 90% of the EM waves in the whole X-band. The RC is less than ?8 dB at 2.6–2.8 mm from RT to 600 °C in the whole X-band, displaying excellent high-temperature absorption performance. The results provide a new design opinion for broad-band EM absorbing SiCf-CMCs at high temperatures. 相似文献
3.
This study investigates the impact of lighting colors on subjective judgments of fabric: in particular, whether the influence of lighting varies depending on fabric types and color combinations. We conducted two visual assessments. In Study 1 (N = 44), eight illuminants and six types of fabric were presented as cloth stimuli. Derived from the literature review, four sets of adjectives (humble-luxurious, cool-warm, old-new, and not preferred-preferred) were used as metrics. In Study 2 (N = 41), five sets of fabric color combination swatches were assessed under lighting conditions that were identical to those of Study 1. Three bipolar scales (ordinary-characterful, classic-modern, and soft-rigid), were employed from factor analysis along with three unipolar scales (luxurious, preferred, harmonious with lighting). The results showed that hue characteristics of lighting and cloth types influenced participants' perceptions of the fabric. Overall, white lighting with 4000 K was the most preferred and luxurious lighting across various types of clothes, while a pinkish white with 4700 K (duv = −0.0127) was the best matched in every color combination. In addition, there were interaction effects between lighting colors, clothes types, and fabric color combinations with regard to each of the perceptual qualities. This study provides empirical evidence for optimally match lighting colors with fabric in the presentation of fabric goods. 相似文献
4.
在当前Web服务海量增加、现有Web服务选择算法低效、用户匹配度差的基础上,针对K中心点算法存在的质点偏移、准确率低和容易发生畸变等问题,提出一种大数据环境下基于K中心点优化算法的Web服务组合方法。该方法是在大数据环境下,根据不同用户需求满意度及Web服务QoS参数,对基于优化初始聚类中心的K中心点算法的Web服务选择及最优Web服务组合进行研究。同时针对不同的选择方法对服务动态选择及组合的准确度、迭代更新次数、候选集选择时间及选择总时间进行实验分析,验证了本文研究方法的有效性和可靠性。 相似文献
5.
6.
Natalia S Serkhacheva Nikolay I Prokopov Elena V Chernikova Elena Y Kozhunova Inna O Lebedeva Oleg V Borisov 《Polymer International》2019,68(7):1303-1314
Emulsifier‐free batch emulsion polymerization of n‐butyl acrylate and its semi‐batch copolymerization with 2,2,3,3,4,4,5,5‐octafluoropentyl acrylate and 2,2,3,4,4,4‐hexafluorobutyl acrylate both mediated by poly(acrylic acid) containing the trithiocarbonate group in the chain was employed to produce amphiphilic triblock copolymers. The polymerization‐induced self‐assembly of these copolymers in aqueous media gave rise to spherical core–shell particles. Irrespective of the experimental conditions, the polymeric product was characterized by a bimodal molecular weight distribution. The apparent violation of the reversible addition–fragmentation chain transfer polymerization mechanism may be attributed to restricted accessibility of the trithiocarbonate group in the self‐assembled block copolymers for propagating radicals that enter into the particle. Mean‐field theoretical arguments were employed to explain the exclusively spherical morphology of the particles observed in the experiment. © 2019 Society of Chemical Industry 相似文献
7.
8.
9.
对混凝土试样实施温度跟踪养护,可以模拟混凝土在某种保温环境中,在自身水化热的影响下,其水化产物、体积稳定性和力学性能的变化规律.基于虚拟仪器的思想,研制了混凝土温度跟踪养护仪.试验结果表明:该温度跟踪养护仪可依据设定的温度变化历程很好地完成对混凝土试样的养护,同时,相对于恒温(T=20℃)条件下养护的混凝土试样,对混凝土试样实施温度跟踪养护可提高其抗压、抗折强度和弹性模量. 相似文献
10.