全文获取类型
收费全文 | 276076篇 |
免费 | 24124篇 |
国内免费 | 13267篇 |
专业分类
电工技术 | 16987篇 |
技术理论 | 24篇 |
综合类 | 19475篇 |
化学工业 | 44356篇 |
金属工艺 | 16847篇 |
机械仪表 | 18182篇 |
建筑科学 | 21038篇 |
矿业工程 | 9722篇 |
能源动力 | 7877篇 |
轻工业 | 18850篇 |
水利工程 | 5193篇 |
石油天然气 | 18348篇 |
武器工业 | 2481篇 |
无线电 | 30015篇 |
一般工业技术 | 31257篇 |
冶金工业 | 14691篇 |
原子能技术 | 3046篇 |
自动化技术 | 35078篇 |
出版年
2024年 | 1328篇 |
2023年 | 4612篇 |
2022年 | 8543篇 |
2021年 | 11567篇 |
2020年 | 8962篇 |
2019年 | 7297篇 |
2018年 | 8120篇 |
2017年 | 9094篇 |
2016年 | 8136篇 |
2015年 | 11147篇 |
2014年 | 14060篇 |
2013年 | 16507篇 |
2012年 | 18269篇 |
2011年 | 19740篇 |
2010年 | 17388篇 |
2009年 | 16450篇 |
2008年 | 16239篇 |
2007年 | 15648篇 |
2006年 | 15460篇 |
2005年 | 13316篇 |
2004年 | 9135篇 |
2003年 | 7495篇 |
2002年 | 6644篇 |
2001年 | 5960篇 |
2000年 | 6261篇 |
1999年 | 6757篇 |
1998年 | 5502篇 |
1997年 | 4506篇 |
1996年 | 4235篇 |
1995年 | 3539篇 |
1994年 | 2844篇 |
1993年 | 1999篇 |
1992年 | 1561篇 |
1991年 | 1244篇 |
1990年 | 952篇 |
1989年 | 763篇 |
1988年 | 550篇 |
1987年 | 343篇 |
1986年 | 291篇 |
1985年 | 201篇 |
1984年 | 145篇 |
1983年 | 118篇 |
1982年 | 126篇 |
1981年 | 106篇 |
1980年 | 83篇 |
1979年 | 49篇 |
1978年 | 27篇 |
1977年 | 20篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
75.
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
76.
Lin Haicheng Huang Wantong Zhao Kun Qiao Shuang Liu Zheng Wu Jian Chen Xi Ji Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam... 相似文献
77.
Qi Yang Qilong Wu Yang Liu Shuiping Luo Xiaotong Wu Xixia Zhao Haiyuan Zou Baihua Long Wen Chen Yujia Liao Lanxi Li Pei Kang Shen Lele Duan Zewei Quan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(36):2002822
Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1−xBix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm−2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO. 相似文献
78.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
79.
Wireless Personal Communications - The traditional simultaneous wireless information and power transfer (SWIPT) system uses a part of signals to decode information, and the other part is used for... 相似文献
80.