全文获取类型
收费全文 | 533827篇 |
免费 | 23745篇 |
国内免费 | 11166篇 |
专业分类
电工技术 | 19333篇 |
技术理论 | 31篇 |
综合类 | 17466篇 |
化学工业 | 89549篇 |
金属工艺 | 31878篇 |
机械仪表 | 28461篇 |
建筑科学 | 26763篇 |
矿业工程 | 13176篇 |
能源动力 | 11802篇 |
轻工业 | 26312篇 |
水利工程 | 8813篇 |
石油天然气 | 32976篇 |
武器工业 | 2262篇 |
无线电 | 51180篇 |
一般工业技术 | 96604篇 |
冶金工业 | 46914篇 |
原子能技术 | 13984篇 |
自动化技术 | 51234篇 |
出版年
2023年 | 4686篇 |
2022年 | 8985篇 |
2021年 | 13931篇 |
2020年 | 10430篇 |
2019年 | 9768篇 |
2018年 | 13404篇 |
2017年 | 14748篇 |
2016年 | 13893篇 |
2015年 | 14112篇 |
2014年 | 18978篇 |
2013年 | 26410篇 |
2012年 | 25015篇 |
2011年 | 28271篇 |
2010年 | 23991篇 |
2009年 | 23963篇 |
2008年 | 23576篇 |
2007年 | 22904篇 |
2006年 | 22293篇 |
2005年 | 19678篇 |
2004年 | 14503篇 |
2003年 | 13179篇 |
2002年 | 12414篇 |
2001年 | 11407篇 |
2000年 | 12003篇 |
1999年 | 12702篇 |
1998年 | 13962篇 |
1997年 | 11591篇 |
1996年 | 9825篇 |
1995年 | 8112篇 |
1994年 | 7134篇 |
1993年 | 6215篇 |
1992年 | 5320篇 |
1991年 | 4927篇 |
1990年 | 4621篇 |
1989年 | 4275篇 |
1988年 | 4000篇 |
1987年 | 3746篇 |
1986年 | 3509篇 |
1985年 | 3547篇 |
1984年 | 3411篇 |
1983年 | 3250篇 |
1981年 | 3128篇 |
1980年 | 3138篇 |
1979年 | 3281篇 |
1978年 | 3492篇 |
1977年 | 3460篇 |
1976年 | 3911篇 |
1975年 | 3209篇 |
1974年 | 3293篇 |
1973年 | 3341篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Peiying Wang Juanli Zhao Yun Fan Wei Zhang Yuanyuan Cui Liangmiao Zhang Bin Liu Hongqiang Nian Yiran Li 《Ceramics International》2021,47(11):15023-15029
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by first-principles calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity. 相似文献
12.
Neural Processing Letters - The boundedness and the global Mittag-Leffler synchronization (GMLS) of fractional-order inertial Cohen–Grossberg neural networks (CGNNS) with time delays are... 相似文献
13.
以“创新、协调、绿色、开放、共享”为内核的新发展理念,是对马克思主义发展理念的继承和发扬,极具时代精神,富含问题意识,为高校思想政治教育发展、教育教学改革实践提供了强大的理论支撑。本文以“通信原理”为例,阐述了新发展理念在课程改革中的思路和方法,实现了思想政治教育与专业基础课程有机融合,为深化高校教学改革、创新人才培养模式提供了思路。 相似文献
14.
15.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献
16.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
18.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
19.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。 相似文献
20.
Jiao Zhang Junjie Li Ayesha Murtaza Aamir Iqbal Lijuan Zhu Shinawar Waseem Ali Muhammad Usman Roshan Yameen Siyi Pan Wanfeng Hu 《International Journal of Food Science & Technology》2022,57(2):963-973
This work evaluated the synergistic effects of combined high-intensity ultrasound (HIU) with β-cyclodextrin (β-CD) treatments on inhibiting browning of apple juice and explored the mechanism through simulation system. The combined treatment of 300 W HIU with 0.006 g mL−1 β-CD had a synergistic impact on maintaining juice colour, resulting in a 39.06% reduction in browning degree, only a 36.64% decrease in total phenolic content, and a 17.82% reduction in PPO activity. The inhibition of enzymatic browning in simulated system revealed that HIU suppressed the enzyme (Polyphenol oxidase, PPO) and β-CD inhibited enzyme (PPO) and embedded substrate (polyphenol). The results of spectroscopic analysis showed that the particle-size distribution of PPO narrowed, the content of α-helix in the secondary structure increased, the fluorescence intensity increased, and the maximum wavelength was red-shifted after HIU and β-CD treatment. Changes in structure could further result in PPO activity loss. Hence, the combined treatment could synthetically alleviate the browning of apple juice. 相似文献