全文获取类型
收费全文 | 113138篇 |
免费 | 13265篇 |
国内免费 | 8823篇 |
专业分类
电工技术 | 9587篇 |
综合类 | 11538篇 |
化学工业 | 14355篇 |
金属工艺 | 7819篇 |
机械仪表 | 7925篇 |
建筑科学 | 8638篇 |
矿业工程 | 5180篇 |
能源动力 | 3076篇 |
轻工业 | 11908篇 |
水利工程 | 3325篇 |
石油天然气 | 4776篇 |
武器工业 | 1732篇 |
无线电 | 11806篇 |
一般工业技术 | 10577篇 |
冶金工业 | 4799篇 |
原子能技术 | 1903篇 |
自动化技术 | 16282篇 |
出版年
2024年 | 670篇 |
2023年 | 2092篇 |
2022年 | 4681篇 |
2021年 | 6130篇 |
2020年 | 4510篇 |
2019年 | 3375篇 |
2018年 | 3422篇 |
2017年 | 3924篇 |
2016年 | 3466篇 |
2015年 | 5541篇 |
2014年 | 6524篇 |
2013年 | 7662篇 |
2012年 | 9315篇 |
2011年 | 9530篇 |
2010年 | 8851篇 |
2009年 | 8389篇 |
2008年 | 8481篇 |
2007年 | 8159篇 |
2006年 | 7085篇 |
2005年 | 5648篇 |
2004年 | 4162篇 |
2003年 | 2844篇 |
2002年 | 2681篇 |
2001年 | 2348篇 |
2000年 | 1947篇 |
1999年 | 1019篇 |
1998年 | 512篇 |
1997年 | 403篇 |
1996年 | 367篇 |
1995年 | 299篇 |
1994年 | 241篇 |
1993年 | 166篇 |
1992年 | 146篇 |
1991年 | 120篇 |
1990年 | 94篇 |
1989年 | 74篇 |
1988年 | 59篇 |
1987年 | 49篇 |
1986年 | 48篇 |
1985年 | 18篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 26篇 |
1980年 | 31篇 |
1979年 | 15篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1959年 | 18篇 |
1951年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
21.
Chuntao Lan Haiyang Zou Longfei Wang Meng Zhang Shuang Pan Ying Ma Yiping Qiu Zhong Lin Wang Zhiqun Lin 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2005481
Despite recent rapid advances in metal halide perovskites for use in optoelectronics, the fundamental understanding of the electrical-poling-induced ion migration, accounting for many unusual attributes and thus performance in perovskite-based devices, remain comparatively elusive. Herein, the electrical-poling-promoted polarization potential is reported for rendering hybrid organic–inorganic perovskite photodetectors with high photocurrent and fast response time, displaying a tenfold enhancement in the photocurrent and a twofold decrease in the response time after an external electric field poling. First, a robust meniscus-assisted solution-printing strategy is employed to facilitate the oriented perovskite crystals over a large area. Subsequently, the electrical poling invokes the ion migration within perovskite crystals, thus inducing a polarization potential, as substantiated by the surface potential change assessed by Kelvin probe force microscopy. Such electrical-poling-induced polarization potential is responsible for the markedly enhanced photocurrent and largely shortened response time. This work presents new insights into the electrical-poling-triggered ion migration and, in turn, polarization potential as well as into the implication of the latter for optoelectronic devices with greater performance. As such, the utilization of ion-migration-produced polarization potential may represent an important endeavor toward a wide range of high-performance perovskite-based photodetectors, solar cells, transistors, scintillators, etc. 相似文献
22.
World Wide Web - The wide spread use of positioning and photographing devices gives rise to a deluge of traffic trajectory data (e.g., vehicle passage records and taxi trajectory data), with each... 相似文献
23.
在新型二次电池产业的发展中,氢镍电池市场不断萎缩,锂离子电池市场正处于黄金时代。通过对日本和中国新型二次电池产业发展历程分析,我国主要针对低端市场,高端市场为日本占据,并从日本发展经验中提出了可供我国锂离子电动车电池发展的借鉴之处。 相似文献
24.
25.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
26.
The fracture behaviour and morphologies of high-strength boron steel were investigated at different temperatures at a constant strain rate of 0.1 s-1 based on isothermal tensile tests. Fracture mechanisms were also analyzed based on the relationship between microstructure transformation and continuous cooling transformation(CCT) curves. It is found that 1) fractures of the investigated steel at high temperatures are dimple fractures; 2) the deformation of high-strength boron steel at high temperatures accelerates diffusion transformations; thus, to obtain full martensite, a higher cooling rate is needed; and 3) the investigated steel has the best plasticity when the deformation temperature is 750 °C. 相似文献
27.
28.
大数据时代的到来,改变了人们的生活方式、思想方式和工作方式,也为国际服务外包产业带来了新的发展机遇。本文首先介绍了WTO透明度原则和我国加入WTO后在法律法规翻译方面应承担的义务及履行情况;其次,从法律流程外包(Legal Process Outsourcing,LPO)的概念、内容和特征出发,分析了大数据技术条件下我国政府法律法规译审外包的必要性,并根据大数据应用的可实时性、可解释性、数据准确性稳定性等基本原则,探讨了大数据技术条件下我国政府法律法规译审外包的运行模式及主要举措;最后,讨论了法律流程外包在我国的发展前景。 相似文献
29.
随着城市建设规模的不断发展,为满足不断增长的城市供热需求并全面落实国家生态保护、清洁供暖、可持续发展等政策,减少城市环境治理的压力,城市供热热源逐步远离城市,形成许多以长距离供暖和大规模供热为特征的长距离供热管线.由于热源和城市的位置关系,长距离供热管线往往会穿越复杂的障碍区域.以富拉尔基发电厂向齐齐哈尔市长距离供热管网项目穿越行洪区段管网作为案例,从管线穿越障碍区域设计、防洪设计及施工便道设计三个方面对供热管网穿越行洪区时的难点进行分析总结. 相似文献
30.