全文获取类型
收费全文 | 151422篇 |
免费 | 14830篇 |
国内免费 | 8160篇 |
专业分类
电工技术 | 10643篇 |
技术理论 | 8篇 |
综合类 | 10758篇 |
化学工业 | 23512篇 |
金属工艺 | 9096篇 |
机械仪表 | 10591篇 |
建筑科学 | 12366篇 |
矿业工程 | 5301篇 |
能源动力 | 4512篇 |
轻工业 | 10457篇 |
水利工程 | 3131篇 |
石油天然气 | 9784篇 |
武器工业 | 1569篇 |
无线电 | 17542篇 |
一般工业技术 | 16504篇 |
冶金工业 | 6817篇 |
原子能技术 | 1822篇 |
自动化技术 | 19999篇 |
出版年
2024年 | 751篇 |
2023年 | 2676篇 |
2022年 | 5051篇 |
2021年 | 6961篇 |
2020年 | 5257篇 |
2019年 | 4190篇 |
2018年 | 4555篇 |
2017年 | 5178篇 |
2016年 | 4781篇 |
2015年 | 6700篇 |
2014年 | 8146篇 |
2013年 | 9645篇 |
2012年 | 10843篇 |
2011年 | 11322篇 |
2010年 | 9986篇 |
2009年 | 9478篇 |
2008年 | 9136篇 |
2007年 | 8680篇 |
2006年 | 8636篇 |
2005年 | 7215篇 |
2004年 | 4769篇 |
2003年 | 4098篇 |
2002年 | 3898篇 |
2001年 | 3386篇 |
2000年 | 3052篇 |
1999年 | 3127篇 |
1998年 | 2393篇 |
1997年 | 1966篇 |
1996年 | 1919篇 |
1995年 | 1607篇 |
1994年 | 1282篇 |
1993年 | 811篇 |
1992年 | 726篇 |
1991年 | 487篇 |
1990年 | 393篇 |
1989年 | 334篇 |
1988年 | 248篇 |
1987年 | 162篇 |
1986年 | 139篇 |
1985年 | 80篇 |
1984年 | 66篇 |
1983年 | 50篇 |
1982年 | 50篇 |
1981年 | 35篇 |
1980年 | 38篇 |
1979年 | 28篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 18篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Zhao Jiandong Lei Wei Li Zijian Zhao Dongfeng Han Mingmin Hou Xiaoqing 《Multimedia Tools and Applications》2022,81(4):4753-4780
Multimedia Tools and Applications - The crowding in bus is an important factor affecting passenger satisfaction and bus dispatching level. However, how to use video images to detect crowding... 相似文献
2.
Wireless Networks - Geolocation is important for many emerging applications such as disaster management and recommendation system. In this paper, we propose a multilayer recognition model (MRM) to... 相似文献
3.
Sinan Zhang Yadonga Zhao Xueshuang Yao Zhenhong Zheng Chuyao Zheng Zhuo Jiang 《International Journal of Food Science & Technology》2022,57(7):4245-4253
Ripe carambolas are hard to store and transport, while freeze-dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze-drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g−1, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g−1. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze-drying time. This work guides the application of HHP technology for drying food processing. 相似文献
4.
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
5.
燕麦为西藏自治区典型牧草之一,由于种植区地域辽阔,灌溉试验结果受限,西藏燕麦主要种植区的灌溉定额尚不明确。本文在西藏燕麦主要种植区内选取28个典型站点进行资料收集,遵循农业气候相似原则进行区域划分,基于水量平衡法揭示了西藏燕麦主要种植区灌溉定额的空间分布特征,并根据统计学原理分析了其影响因素。研究表明:燕麦主要种植区的灌溉定额呈由西藏中部至东部呈现先递增后递减的趋势,50%水文年下的燕麦灌溉定额在56~265 mm之间变化。降雨量是影响研究区内燕麦灌溉定额的主要因素(R2为0.515),ET0次之(R2为0.152);其它气象因素中,日照时数对研究区燕麦灌溉定额影响较大(R2为0.462),且呈正相关关系;相对湿度对燕麦灌溉定额影响较小。西藏燕麦主要种植区的灌溉定额及其空间分布可为西藏自治区灌溉用水管理提供支撑。 相似文献
6.
Applied Composite Materials - In this paper, the low-velocity impact deformation behavior of biaxial warp-knitted flexible composite was investigated. A simplified finite element model (FEM) of the... 相似文献
7.
8.
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
9.
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
10.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献