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   1753351篇
  免费   42283篇
  国内免费   14278篇
电工技术   44805篇
技术理论   14篇
综合类   17342篇
化学工业   296315篇
金属工艺   74379篇
机械仪表   55524篇
建筑科学   62925篇
矿业工程   16269篇
能源动力   55409篇
轻工业   134596篇
水利工程   19128篇
石油天然气   46851篇
武器工业   1479篇
无线电   218503篇
一般工业技术   319953篇
冶金工业   212278篇
原子能技术   35928篇
自动化技术   198214篇
  2021年   22702篇
  2020年   17215篇
  2019年   19210篇
  2018年   20987篇
  2017年   21025篇
  2016年   26848篇
  2015年   24342篇
  2014年   37751篇
  2013年   99162篇
  2012年   49378篇
  2011年   63955篇
  2010年   54249篇
  2009年   61812篇
  2008年   57442篇
  2007年   54533篇
  2006年   56882篇
  2005年   50176篇
  2004年   49421篇
  2003年   48515篇
  2002年   46821篇
  2001年   43726篇
  2000年   42051篇
  1999年   42310篇
  1998年   61334篇
  1997年   49910篇
  1996年   41185篇
  1995年   36238篇
  1994年   33336篇
  1993年   32265篇
  1992年   27974篇
  1991年   25012篇
  1990年   24994篇
  1989年   23846篇
  1988年   22305篇
  1987年   20324篇
  1986年   19880篇
  1985年   23178篇
  1984年   22846篇
  1983年   20754篇
  1982年   19507篇
  1981年   19596篇
  1980年   18265篇
  1979年   18817篇
  1978年   17957篇
  1977年   18622篇
  1976年   21189篇
  1975年   16098篇
  1974年   15657篇
  1973年   15732篇
  1972年   13292篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
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   
32.
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   
33.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
34.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
35.
Multimedia Tools and Applications - Endometriosis is a common gynecologic condition typically treated via laparoscopic surgery. Its visual versatility makes it hard to identify for non-specialized...  相似文献   
36.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
37.
《药物分析学实验》是药学专业的一门独立必修课程,是药学科学领域中的一个重要组成部分,具有较强的实践性和综合性,旨在培养学生综合运用所学知识分析药品质量的能力.综合设计性实验作为《药物分析学实验》的重要组成部分,对学生实践操作能力,发现问题、分析问题、解决问题的能力,创新能力,应用能力,团结协作能力,劳动素养等综合能力的培养具有极其重要的意义.  相似文献   
38.
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   
39.
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   
40.

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

  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