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   275409篇
  免费   6210篇
  国内免费   736篇
电工技术   4200篇
综合类   407篇
化学工业   45415篇
金属工艺   11610篇
机械仪表   8363篇
建筑科学   6336篇
矿业工程   2334篇
能源动力   6539篇
轻工业   23902篇
水利工程   3626篇
石油天然气   8057篇
武器工业   33篇
无线电   25584篇
一般工业技术   56018篇
冶金工业   48878篇
原子能技术   7009篇
自动化技术   24044篇
  2022年   2213篇
  2021年   3927篇
  2020年   2964篇
  2019年   3588篇
  2018年   6092篇
  2017年   6118篇
  2016年   6459篇
  2015年   4061篇
  2014年   6225篇
  2013年   13424篇
  2012年   9427篇
  2011年   11301篇
  2010年   9000篇
  2009年   9474篇
  2008年   9523篇
  2007年   9115篇
  2006年   7549篇
  2005年   6892篇
  2004年   6414篇
  2003年   6189篇
  2002年   5944篇
  2001年   5695篇
  2000年   5186篇
  1999年   5254篇
  1998年   14957篇
  1997年   10323篇
  1996年   7618篇
  1995年   5401篇
  1994年   4617篇
  1993年   4920篇
  1992年   3380篇
  1991年   3441篇
  1990年   3268篇
  1989年   3198篇
  1988年   3224篇
  1987年   2815篇
  1986年   2867篇
  1985年   3191篇
  1984年   2938篇
  1983年   2737篇
  1982年   2523篇
  1981年   2535篇
  1980年   2592篇
  1979年   2522篇
  1978年   2524篇
  1977年   2845篇
  1976年   3491篇
  1975年   2321篇
  1974年   2153篇
  1973年   2278篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
Transmission electron microscopy (TEM) is an important analysis technique to visualize (bio)macromolecules and their assemblies, including collagen fibers. Many protocols for TEM sample preparation of collagen involve one or more washing steps to remove excess salts from the dispersion that could hamper analysis when dried on a TEM grid. Such protocols are not standardized and washing times as well as washing solvents vary from procedure to procedure, with each research group typically having their own protocol. Here, we investigate the influence of washing with water, ethanol, but also methanol and 2-propanol, for both mineralized and unmineralized collagen samples via a protocol based on centrifugation. Washing with water maintains the hydrated collagen structure and the characteristic banding pattern can be clearly observed. Conversely, washing with ethanol results in dehydration of the fibrils, often leading to aggregation of the fibers and a less obvious banding pattern, already within 1 min of ethanol exposure. As we show, this process is fully reversible. Similar observations were made for methanol and propanol. Based on these results, a standardized washing protocol for collagenous samples is proposed.  相似文献   
3.
4.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
5.
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   
6.
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   
7.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
8.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
9.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  相似文献   
10.
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C.  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