全文获取类型
收费全文 | 30740篇 |
免费 | 2661篇 |
国内免费 | 1840篇 |
专业分类
电工技术 | 2385篇 |
技术理论 | 1篇 |
综合类 | 2476篇 |
化学工业 | 4425篇 |
金属工艺 | 1749篇 |
机械仪表 | 2055篇 |
建筑科学 | 2478篇 |
矿业工程 | 811篇 |
能源动力 | 839篇 |
轻工业 | 2823篇 |
水利工程 | 752篇 |
石油天然气 | 1649篇 |
武器工业 | 322篇 |
无线电 | 3534篇 |
一般工业技术 | 2953篇 |
冶金工业 | 1300篇 |
原子能技术 | 502篇 |
自动化技术 | 4187篇 |
出版年
2024年 | 87篇 |
2023年 | 407篇 |
2022年 | 812篇 |
2021年 | 1149篇 |
2020年 | 816篇 |
2019年 | 644篇 |
2018年 | 730篇 |
2017年 | 932篇 |
2016年 | 807篇 |
2015年 | 1226篇 |
2014年 | 1608篇 |
2013年 | 1864篇 |
2012年 | 2137篇 |
2011年 | 2231篇 |
2010年 | 2129篇 |
2009年 | 2039篇 |
2008年 | 2048篇 |
2007年 | 1981篇 |
2006年 | 1848篇 |
2005年 | 1570篇 |
2004年 | 1196篇 |
2003年 | 1101篇 |
2002年 | 1109篇 |
2001年 | 969篇 |
2000年 | 787篇 |
1999年 | 674篇 |
1998年 | 488篇 |
1997年 | 357篇 |
1996年 | 346篇 |
1995年 | 277篇 |
1994年 | 230篇 |
1993年 | 154篇 |
1992年 | 149篇 |
1991年 | 89篇 |
1990年 | 68篇 |
1989年 | 65篇 |
1988年 | 40篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1959年 | 3篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
采用直流磁控溅射和后退火氧化工艺在p型GaAs单晶衬底上成功制备了n-VO_2/pGaAs异质结,研究了不同退火温度和退火时间对VO_2/GaAs异质结性能的影响,并分析其结晶取向、化学组分、膜层质量以及光电特性。结果表明,在退火时间2 h和退火温度693 K下能得到相变性能最佳的VO_2薄膜,相变前后电阻变化约2个数量级。VO_2/GaAs异质结在308 K、318 K和328 K温度下具有较好的整流特性,对应温度下的阈值跳变电压分别为6.9 V、6.6 V和6.2 V,该结果为基于VO_2相变特性的异质结光电器件的设计与应用提供了可行性。 相似文献
2.
3.
Chenglai Xin Rong Yuan Jiang Wu Qingyuan Wang Yanan Zhou 《Ceramics International》2021,47(3):3411-3420
A novel method for fabricating a nano-Cu/Si3N4 ceramic substrate is proposed. The nano-Cu/Si3N4 ceramic substrate is first fabricated using spark plasma sintering (SPS) with the addition of nanoscale multilayer films (Ti/TiN/Ti/TiN/Ti) as transition layers. The microstructures of the nano-Cu metal layer and the interface between Cu and Si3N4 are investigated. The results show that a higher SPS temperature increases the grain size of the nano-Cu metal layer and affects the hardness. The microstructure of the transition layer evolves significantly after SPS. Ti in the transition layer can react with Si3N4 and with nano-Cu to form interfacial reaction layers of TiN and Ti–Cu, respectively; these ensure stronger bonding between nano-Cu and Si3N4. Higher SPS temperatures improve the diffusion ability of Ti and Cu, inducing the formation of Ti3Cu3O compounds in the nano-Cu metal layer and Ti2Cu in the transition layer. This study provides an important strategy for designing and constructing a new type of ceramic substrate. 相似文献
4.
5.
Scientometrics - In traditional research, the application of quantitative measurement on the value and influence of uncited papers is not feasible owing to the lack of data. The rapid advancement... 相似文献
6.
7.
为检查工程质量,查找输水系统可能存在的问题并消除隐患,保障电站安全运行,福建仙游抽水蓄能电站在投产发电前,要对输水发电系统进行充水试验与放空排水试验,在试验过程中监测输水系统的应力、应变与渗漏水情况。本文以尾水系统为例,介绍了试验所应具备的工程条件、工作程序及技术要求、试验成果分析和存在问题处理等。试验表明,仙游抽水蓄能电站尾水系统设计合理,施工质量优良,结构可靠,可供同类工程参考与借鉴。 相似文献
8.
Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhaojun Ban Wenwen Wei Xiangzheng Yang Jianhua Feng Junfeng Guan Li Li 《International Journal of Food Science & Technology》2015,50(4):1019-1025
The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits. 相似文献
9.
10.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献