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   1455篇
  免费   58篇
  国内免费   5篇
电工技术   10篇
综合类   5篇
化学工业   380篇
金属工艺   86篇
机械仪表   24篇
建筑科学   76篇
矿业工程   6篇
能源动力   49篇
轻工业   163篇
水利工程   13篇
无线电   78篇
一般工业技术   257篇
冶金工业   140篇
原子能技术   17篇
自动化技术   214篇
  2023年   10篇
  2022年   18篇
  2021年   22篇
  2020年   10篇
  2019年   17篇
  2018年   19篇
  2017年   23篇
  2016年   31篇
  2015年   38篇
  2014年   41篇
  2013年   49篇
  2012年   87篇
  2011年   95篇
  2010年   74篇
  2009年   70篇
  2008年   79篇
  2007年   75篇
  2006年   47篇
  2005年   43篇
  2004年   42篇
  2003年   33篇
  2002年   39篇
  2001年   23篇
  2000年   34篇
  1999年   29篇
  1998年   34篇
  1997年   39篇
  1996年   16篇
  1995年   24篇
  1994年   21篇
  1993年   24篇
  1992年   14篇
  1991年   16篇
  1990年   24篇
  1989年   19篇
  1988年   20篇
  1987年   10篇
  1986年   12篇
  1985年   14篇
  1984年   20篇
  1983年   23篇
  1982年   11篇
  1981年   14篇
  1980年   19篇
  1979年   12篇
  1978年   16篇
  1977年   11篇
  1975年   8篇
  1973年   9篇
  1971年   9篇
排序方式: 共有1518条查询结果,搜索用时 15 毫秒
41.
Electronic Markets - Physical inactivity is a global public health problem that poses health risks to individuals and imposes financial burdens on already strained healthcare systems. Wearables...  相似文献   
42.
43.
Calcination is a thermo-chemical process, widely used in the cement industry, where limestone is converted by thermal decomposition into lime CaO and carbon dioxide CO2. The focus of this paper is on the implementation and validation of the endothermic calcination reaction mechanism of limestone in a commercial finite volume based CFD code. This code is used to simulate the turbulent flow field, the temperature field, concentrations of the reactants and products, as well as the interaction of particles with the gas phase, by solving the mathematical equations, which govern these processes. For calcination, the effects of temperature, decomposition pressure, diffusion and pore efficiency were taken into account. A simple three-dimensional geometry of a pipe reactor was used for numerical simulations. To verify the accuracy of the modelling approach, the numerical predictions were compared with experimental data, yielding satisfying results and proper trends of physical parameters influencing the process.  相似文献   
44.
45.
46.
47.
48.
Manufacturing of chemical‐pharmaceutical products is moving increasingly fast on a global scale. Therefore, developing and starting up production facilities fast, with high quality, and at reasonable costs has become extremely challenging. Engineering concepts like modularization, standardization and simultaneous/parallel engineering are discussed as methods for speeding up process design and filing for regulatory approval. Transfer from batch to continuous operation mode of production is pointed out as the key‐issue in such strategies.  相似文献   
49.
Microencapsulation aims to protect polyunsaturated fatty acids against oxidation by embedding oil droplets in a solid matrix. In such a system the internal (dissolved and entrapped) and external (in the environment) oxygen can be differentiated. The study aims to quantify the impact of both oxygen sources on the oxidation of microencapsulated fish oil. The impact of the solubilized oxygen in bulk fish oil is investigated by saturating the oil with nitrogen, synthetic air, and pure oxygen. Even though more dissolved oxygen results in more oxidation products, the difference between the oxidation of the nitrogen and air saturated oil is significant but low. For encapsulated fish oil powders, the internal oxygen is modified by preparing oil‐in‐water emulsions under atmospheric and inert conditions. The feed is atomized and spray dried with either nitrogen or air. Powders are stored under vacuum and in vials and the hydroperoxides and anisidine value are determined in the total‐ and encapsulated oil. The internal oxygen has a minor impact, whereas the external oxygen is the main determinant for autoxidation. Apart from oxidizing the non‐encapsulated oil, the external O2 penetrates into the particle and reacts with the encapsulated oil. Practical Applications: Comparing the contribution of the internal and external oxygen to the oxidative stability shows that the internal O2 plays a minor role and can be neglected. This means that the emulsion preparation as well as the spray drying process can be conducted under ambient conditions. An inert production is not extending the shelf life significantly as long as the external O2 determines oxidation. The focus should be on optimizing the diffusion barrier properties of the wall matrix to reduce the penetration of the external oxygen into the particle system. Alternatively, packaging solution reducing the external O2 will extend the shelf life of the microencapsulated oil.  相似文献   
50.
Mineral oil hydrocarbons (MOH) are present in many fats and oils as well as foods prepared thereof. A survey of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in different types of vegetable fats and oils is reported. Contents of MOSH/MOAH were quantified using liquid chromatography online‐coupled to gas chromatography with flame‐ionization detection (LC‐GC‐FID). Cocoa butter (n = 142) showed levels from <LOQ (2.5 mg kg?1) to 162 mg kg?1 ΣMOSH (sum of C10–C50) and <LOQ to 55 mg kg?1 ΣMOAH, in palm oil (n = 21) ΣMOSH were quantified from <LOQ to 124 mg kg?1 and ΣMOAH from <LOQ to 39 mg kg?1. Sunflower oil showed lower levels: ΣMOSH were determined in the range of <LOQ to 17 mg kg?1 and MOAH were not observed at all. A possible influence of deodorization and a subsequent minimization of MOSH/MOAH was investigated. Systematic model‐experiments were performed on laboratory scale using spiked cocoa butter. Significant minimization of volatile MOH subfractions ≤C24 were observed at a deodorization temperature of 210 °C. Deodorization can be considered as an important processing step to reduce or even remove volatile MOSH/MOAH ≤C24. Practical Applications: Regardless of their possible entry routes into the food chain, volatile fractions of MOSH/MOAH can be removed by deodorizing vegetable fats and oils. This model‐study identifies the temperatures of deodorization that provide a significant improvement toward minimization of undesired MOSH/MOAH.  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