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   225199篇
  免费   17499篇
  国内免费   8850篇
电工技术   12444篇
技术理论   20篇
综合类   12749篇
化学工业   38544篇
金属工艺   11759篇
机械仪表   13406篇
建筑科学   18078篇
矿业工程   5579篇
能源动力   6440篇
轻工业   14235篇
水利工程   3589篇
石油天然气   12220篇
武器工业   1485篇
无线电   27844篇
一般工业技术   29121篇
冶金工业   11810篇
原子能技术   2356篇
自动化技术   29869篇
  2024年   627篇
  2023年   3410篇
  2022年   5271篇
  2021年   8406篇
  2020年   6329篇
  2019年   5448篇
  2018年   5990篇
  2017年   6804篇
  2016年   6268篇
  2015年   8151篇
  2014年   10653篇
  2013年   13613篇
  2012年   13843篇
  2011年   15634篇
  2010年   12933篇
  2009年   12725篇
  2008年   12213篇
  2007年   11775篇
  2006年   12136篇
  2005年   10668篇
  2004年   7262篇
  2003年   6413篇
  2002年   5942篇
  2001年   5264篇
  2000年   5388篇
  1999年   6196篇
  1998年   5724篇
  1997年   4685篇
  1996年   4265篇
  1995年   3588篇
  1994年   3039篇
  1993年   2358篇
  1992年   1807篇
  1991年   1366篇
  1990年   1078篇
  1989年   923篇
  1988年   712篇
  1987年   515篇
  1986年   397篇
  1985年   328篇
  1984年   209篇
  1983年   190篇
  1982年   172篇
  1981年   145篇
  1980年   138篇
  1979年   97篇
  1978年   67篇
  1977年   66篇
  1976年   81篇
  1975年   40篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
1.
Feng  Wenran  Li  Zhen  Chen  Yingying  Chen  Jinyang  Lang  Haoze  Wan  Jianghong  Gao  Yan  Dong  Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in...  相似文献   
2.
Multimedia Tools and Applications - With the advancement of technology and the spread of the COVID19 epidemic, learning can no longer only be done through face-to-face teaching. Numerous digital...  相似文献   
3.
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   
4.
5.
6.
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results.  相似文献   
7.
The purpose of this study was to increase the water solubility and potential bioavailability of quercetin by encapsulation in whey protein isolate (WPI) based on a green, efficient pH-driven method. According to the results, the water solubility of quercetin increased by 346.9: times after loading into WPI nanoparticles. When the initial quercetin concentration was 0.25 mg mL−1 and WPI was 2% w/v, the encapsulation efficiency reached 94.1%, the Z-average diameter was 36.63 nm, and the zeta potential was −36.4 mV at pH 7.0. The fluorescence spectroscopy assay suggested the molecular complexation of quercetin and WPI at pH 12.0. X-ray diffraction assay indicated the enclosure of amorphous quercetin in WPI. Correspondingly, the bioaccessibility increased from 2.76% to 31.23% and the Caco-2 cell monolayer uptake increased from 0% to 2.12% after nanoencapsulation. This work confirmed that the pH-driven method is an effective approach to prepare WPI–quercetin nanocapsules to improve physical and potentially biological properties of quercetin.  相似文献   
8.
Mangiferin (MGF) is a phenolic compound isolated from mango, but its poor solubility significantly limits its use. In this study, MGF was embedded into the inner aqueous phase of W1/O/W2 emulsions. Firstly, the dissolution method of MGF was determined. MGF remained stable in solution with pH 13 at 30 min, and its solubility reached 10 mg mL−1. When the pH of MGF solutions was adjusted from pH 13 to pH 6, MGF did not immediately crystallise, providing sufficient time to construct the MGF-loaded W1/O/W2 emulsions. Subsequently, the MGF-loaded W1/O/W2 emulsions were constructed using polyglycerol polyricinoleate (PGPR) and calcium caseinate (CAS). The formation and stability of the W1/O/W2 emulsions were investigated. The MGF-loaded W1/O/W2 emulsions stabilised with 1% PGPR and 1% – 3% CAS exhibited a low viscosity, limited loading capacity, and poor stability. Conversely, the MGF-loaded W1/O/W2 emulsions stabilised by 3%PGPR–3%CAS exhibited optimal loading capacity (encapsulation efficiency = 95.31% and loading efficiency = 0.91%) and stability, which was attributed to the fact that high viscosity and gel state retarded the migration of inner aqueous phase. These results indicated that the W1/O/W2 emulsions stabilised by PGPR and CAS may be a potential alternative for encapsulating mangiferin.  相似文献   
9.
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   
10.
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   
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