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   2030547篇
  免费   68643篇
  国内免费   29420篇
电工技术   66475篇
技术理论   70篇
综合类   45228篇
化学工业   356002篇
金属工艺   94508篇
机械仪表   78205篇
建筑科学   91475篇
矿业工程   30548篇
能源动力   64662篇
轻工业   145834篇
水利工程   25566篇
石油天然气   73426篇
武器工业   4771篇
无线电   252227篇
一般工业技术   337936篇
冶金工业   183432篇
原子能技术   39254篇
自动化技术   238991篇
  2022年   20618篇
  2021年   35558篇
  2020年   26983篇
  2019年   26747篇
  2018年   29242篇
  2017年   30887篇
  2016年   35385篇
  2015年   38171篇
  2014年   55185篇
  2013年   118616篇
  2012年   70060篇
  2011年   85576篇
  2010年   76042篇
  2009年   82341篇
  2008年   75564篇
  2007年   71782篇
  2006年   76007篇
  2005年   67059篇
  2004年   59074篇
  2003年   56946篇
  2002年   54922篇
  2001年   50270篇
  2000年   49258篇
  1999年   49849篇
  1998年   53585篇
  1997年   47420篇
  1996年   43793篇
  1995年   38141篇
  1994年   34961篇
  1993年   32494篇
  1992年   29697篇
  1991年   25874篇
  1990年   25621篇
  1989年   24263篇
  1988年   22599篇
  1987年   20391篇
  1986年   19534篇
  1985年   22634篇
  1984年   22677篇
  1983年   20510篇
  1982年   19473篇
  1981年   19487篇
  1980年   18107篇
  1979年   18670篇
  1978年   17616篇
  1977年   17360篇
  1976年   18536篇
  1975年   15848篇
  1974年   15398篇
  1973年   15473篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
41.
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   
42.
Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology.  相似文献   
43.
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   
44.
Yang  Annan  Li  Bo  Yang  Mao  Yan  Zhongjiang  Xie  Yi 《Wireless Networks》2021,27(1):809-823
Wireless Networks - In this paper, a grouping-based uplink orthogonal frequency division multiple access (OFDMA) random access method is studied which can improve users’ satisfaction in the...  相似文献   
45.
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   
46.
47.
48.
49.
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   
50.
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