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   287篇
  免费   24篇
  国内免费   23篇
化学   200篇
晶体学   2篇
力学   22篇
数学   36篇
物理学   28篇
无线电   46篇
  2023年   12篇
  2022年   19篇
  2021年   28篇
  2020年   20篇
  2019年   25篇
  2018年   18篇
  2017年   12篇
  2016年   20篇
  2015年   14篇
  2014年   19篇
  2013年   19篇
  2012年   23篇
  2011年   23篇
  2010年   12篇
  2009年   15篇
  2008年   8篇
  2007年   9篇
  2006年   6篇
  2005年   11篇
  2004年   5篇
  2003年   1篇
  2002年   2篇
  2000年   2篇
  1995年   1篇
  1994年   1篇
  1991年   1篇
  1988年   1篇
  1987年   2篇
  1985年   4篇
  1983年   1篇
排序方式: 共有334条查询结果,搜索用时 0 毫秒
1.
Improved decoding of LDPC coded modulations   总被引:1,自引:0,他引:1  
A coded modulation belief propagation (CMBP) decoder is proposed for decoding LDPC codes with multilevel modulations. The decoder takes into account statistical dependencies among bits originating in the same symbol, providing better performance than the marginal BP (MBP) decoder. Asymptotically it converges to MAP decoding. The CMBP decoder is based on a single-level coding (SLC) scheme and does not suffer from practical disadvantages of multi-level coding (MLC) schemes. Furthermore, the CMBP decoder can close the capacity gap of the bit interleaved coded modulation (BICM) SLC scheme. The BICM capacity gap increases when the modulation size increases and in scenarios where gray mapping is not possible.  相似文献   
2.
Two novel tyrosinase mediated drug delivery pathways have been investigated for the selective delivery of cytotoxic units to melanocytes from urea and thiourea prodrugs. The synthesis of these prodrugs is reported, as well as oximetry data that illustrate that the targets are substrates for tyrosinase. The stability of each of the prodrugs in (i) phosphate buffer and (ii) bovine serum is discussed, and the urea prodrugs are identified as lead candidates for further studies. Finally, HPLC studies and preliminary cytotoxicity studies in a melanotic and an amelanotic cell line, that illustrate the feasibility of the approach, are presented.  相似文献   
3.
Carbohydrate chains in glycoprotein pharmaceuticals have important roles for the expression of their biological activities. Therefore, development of an assessment method for the carbohydrate chains is an important parameter for quality control of glycoprotein pharmaceuticals such as newly developed therapeutic antibodies. In this report, we applied capillary electrophoresis with laser-induced fluorescence detection to the analysis of carbohydrate chains after releasing with glycoamidase followed by derivatization with 3-aminobenzoic acid. We found that four major oligosaccharides present in antibody pharmaceuticals were successfully separated with good resolution. The present method showed good precision in both migration times and relative peak areas, and gave comparable accuracy with that using a derivatization method with 8-aminopyrene-1,3,6-trisulfonate.  相似文献   
4.
有机薄膜太阳电池作为一种新型光伏电池,近年来得到了迅猛发展。其制备工艺简单、价格低廉、柔性、质轻,为人类解决能源问题提供了一种崭新的途径。文章综述了近年来有机薄膜太阳电池的发展状况,结合有机薄膜太阳电池的发展历史,分析了单异质结、体异质结和叠层三种典型结构器件的工作原理和研究成果,探讨了各种器件结构的优缺点,并对有机薄膜太阳电池的发展趋势作了展望。  相似文献   
5.
The electrochemical synthesis of a copolymer electrolyte (PEO-PMMA) into titania nanotubes is described and studied. Compared with the electrochemical systems based on solid electrolytes deposited by top-down techniques, the copolymer/titania nanotube material reveals high electrochemical performance, opening new perspectives for the fabrication of 3D all-solid-state microbatteries.  相似文献   
6.
7.
8.
9.
10.
Cascade reactions of nitroallylic acetates with methanesulfonyl 2-aminoethanones affords either the 3-pyrrolines or the pyrroles in one pot depending on reaction solvents and temperature. A possible mechanism for the entire sequence is proposed.  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