首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   91798篇
  免费   8076篇
  国内免费   4533篇
电工技术   5438篇
技术理论   10篇
综合类   6614篇
化学工业   14401篇
金属工艺   5351篇
机械仪表   6024篇
建筑科学   7606篇
矿业工程   3127篇
能源动力   2583篇
轻工业   6761篇
水利工程   1930篇
石油天然气   5276篇
武器工业   1016篇
无线电   10482篇
一般工业技术   10675篇
冶金工业   4424篇
原子能技术   1160篇
自动化技术   11529篇
  2024年   171篇
  2023年   1438篇
  2022年   2497篇
  2021年   3594篇
  2020年   2902篇
  2019年   2343篇
  2018年   2519篇
  2017年   2835篇
  2016年   2540篇
  2015年   3633篇
  2014年   4516篇
  2013年   5434篇
  2012年   6291篇
  2011年   6583篇
  2010年   5885篇
  2009年   5586篇
  2008年   5661篇
  2007年   5452篇
  2006年   5384篇
  2005年   4644篇
  2004年   3246篇
  2003年   2566篇
  2002年   2437篇
  2001年   2211篇
  2000年   2062篇
  1999年   2115篇
  1998年   1838篇
  1997年   1474篇
  1996年   1410篇
  1995年   1094篇
  1994年   1031篇
  1993年   712篇
  1992年   549篇
  1991年   437篇
  1990年   326篇
  1989年   260篇
  1988年   233篇
  1987年   138篇
  1986年   101篇
  1985年   75篇
  1984年   33篇
  1983年   33篇
  1982年   41篇
  1981年   26篇
  1980年   24篇
  1979年   8篇
  1976年   1篇
  1973年   1篇
  1959年   9篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
31.
Brown rice noodles (RN) are typical whole-grain products with health benefits. This study investigated the effects of rice bran fermented with Lactobacillus plantarum on palatability, volatile profiles, and antioxidant activity of brown RN. Three kinds of RN, including RN, brown RN (BRN), and bran fermented RN (BFRN), were involved in this study. The results indicated that bran fermentation reduced the cooking loss of BFRN and improved the elongation and the sensory attributes of brown RN. After fermentation, aldehydes were significantly decreased while alcohols increased, and more pleasant flavours were shown in BFRN. Fermentation increased the content of free phenolics and decreased the content of bound phenolics. Among the four major phenolics detected in this study, ferulic acid was the most abundant one in all three RN samples. The DPPH radical scavenging activity and the ferric reducing antioxidant power of free phenolics in BFRN increased significantly compared to BRN. This study proved that rice bran fermentation is an effective approach to improve palatability, enrich the flavour as well as enhance the antioxidant activity of brown RN, which may facilitate the development of processing technology for brown RN.  相似文献   
32.
Palladium-based catalysts have been widely employed in the electro-Fenton process for in situ generation of H2O2. However, the process is still far from being practical on a large scale. In this work, a series of ClxFePd/γ-Al2O3/Al catalysts were prepared by a three-step-impregnation method. They exhibited excellent activity in H2O2 in situ synthesis and high efficiency in phenol degradation. The characterization results showed that Cl could assist in increasing the content of Pd0 and reducing the isoelectric point of catalysts, which led to the drastic promotion in the synthesis of H2O2. Theoretical calculations further demonstrated that Cl doping could facilitate the main reaction in H2O2 synthesis, as well as inhibit side reactions such as dissociation of the O O bond. Furthermore, kinetic models were proposed and fitted. A plausible reaction mechanism as well as degradation pathways were elaborated based on electron spin resonance and gas chromatography–mass spectrometry results. These findings illustrate the value of palladium-based ClxFePd/γ-Al2O3/Al catalysts for their application in the electro-Fenton process.  相似文献   
33.
Molecular dynamics simulations are performed to investigate the solid surface-induced microstructure and friction coefficient of glycerol aqueous solutions with different water contents confined in graphene and FeO nanoslits. Results show that the friction coefficient of glycerol aqueous solutions confined in both nanoslits presents similar nonlinear variation tendencies with increasing water content, but their lowest value and the corresponding water contents differ. Distinctive microstructures of the near-surface liquid layer induced by surfaces with different hydrophilicity are responsible for their difference in lubrication. The sliding primarily occurs at the solid–liquid interface for the hydrophobic graphene nanoslit owing to almost the same velocity difference in fluid molecules. By contrast, the sliding mainly occurs at the liquid–liquid interface for the hydrophilic FeO nanoslit because of the large velocity difference in fluid molecules. The weaker the interaction force at the sliding position, the lower the friction coefficient.  相似文献   
34.
Aqueous film-forming foams (AFFFs) are an important for fire extinguishing, and their key ingredient is fluorinated surfactant. In recent years, traditional long-chain fluorinated surfactants have been banned by most countries because of their persistence, bio-accumulation and toxicity. Therefore, increased attention has been paid to the research and development of short-chain fluorinated surfactants. As is well known, the introduction of hydrophilic or hydrophobic groups in a surfactant affects its surface activity, and therefore, the fire extinguishing performance of AFFFs. In this work, a series of short-chain fluorosurfactant-based AFFFs with different hydrophobic chain lengths were prepared. The physicochemical performance of mixed systems (fluorinated surfactant plus sodium hexanesulfonate), including surface activity, spreading ability, foam expansion, drainage time, and the fire extinguishing and burn-back performance of AFFFs were studied. The results show that the critical micelle concentration (CMC) and the surface tension (γCMC) at the CMC of mixed systems at 25°C are lower than 7.68 mmol/L and 16.51 mN/m, respectively. For mixed systems, the average spreading rate is more than 1.09 cm/s, the foam expansion is over 7.1, and the drainage time is greater than 3.28 min. The fire extinguishing time of AFFFs on fuels is less than 51 s while the burn-back time is more than 15.18 min. The results imply a potential application prospect of the short-chain fluorinated surfactants in AFFFs.  相似文献   
35.
根据剪切解络-超滤过程中金属离子的动态浓度关系和质量守恒定律,采用CodeBlocks17.12软件编写程序,建立了剪切解络-超滤工艺关键指标预测模型,实现了金属离子浓度、回收率、体积稀释倍数等指标的预测,并用实验加以验证。依次在转速800 r/min、1 400 r/min、3 000 r/min下回收模拟废水中43 μg/L的Co2+、995 μg/L的Ni2+和88 μg/L的La3+,3种金属的回收率均达99.8%以上时,超滤过程体积稀释倍数的预测值分别为7.0、7.5、5.75,实验值分别为7.5、7.25、6.25,可见预测值与实验值基本一致。本模型对研究方案制定和调整有实际指导意义。  相似文献   
36.
Ding  Haomiao  Zhang  Yuzhe  Zha  Yue  Zhou  Sijia  Cao  Chaoqing  Zhu  Huajian  Xu  Feng  Zhang  Xiuqiang  Wang  Caisheng 《Food science and biotechnology》2022,31(13):1741-1751
Food Science and Biotechnology - The cytoprotective and potential molecular mechanisms of Hylocereus polyrhizus protein (RFPP) were investigated on the hydrogen peroxide (H2O2)-triggered damage in...  相似文献   
37.
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   
38.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
39.
International Journal of Thermophysics - The addition of nanoparticles to base fuel may bring about remarkable changes in a thermodynamic process such as evaporation, due to the intensified...  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号