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   1587516篇
  免费   32309篇
  国内免费   8389篇
化学   697539篇
晶体学   20919篇
力学   76246篇
综合类   114篇
数学   246495篇
物理学   387280篇
无线电   199621篇
  2021年   14913篇
  2020年   17497篇
  2019年   17630篇
  2018年   17274篇
  2017年   15731篇
  2016年   31360篇
  2015年   22180篇
  2014年   32874篇
  2013年   78735篇
  2012年   43370篇
  2011年   43605篇
  2010年   42871篇
  2009年   47304篇
  2008年   45842篇
  2007年   44121篇
  2006年   46469篇
  2005年   41350篇
  2004年   41009篇
  2003年   37879篇
  2002年   38007篇
  2001年   36788篇
  2000年   32292篇
  1999年   29324篇
  1998年   27596篇
  1997年   27390篇
  1996年   26973篇
  1995年   24699篇
  1994年   24194篇
  1993年   23566篇
  1992年   23388篇
  1991年   23547篇
  1990年   22372篇
  1989年   22020篇
  1988年   21257篇
  1987年   19929篇
  1986年   18736篇
  1985年   25241篇
  1984年   26406篇
  1983年   22335篇
  1982年   23686篇
  1981年   22886篇
  1980年   22124篇
  1979年   22069篇
  1978年   23332篇
  1977年   22898篇
  1976年   22479篇
  1975年   21174篇
  1974年   20804篇
  1973年   21323篇
  1972年   15495篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
71.
The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3, by cyanostar macrocycles that are size-complementary to the inorganic BF4 progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R−BF3 anions.  相似文献   
72.
Wireless Personal Communications - Besides anti-malware usage for the eradication of malicious attacks, researchers have developed epidemic models in order to gain more insights into the spread...  相似文献   
73.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy...  相似文献   
74.
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   
75.
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically...  相似文献   
76.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  相似文献   
77.
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   
78.
Mobile Networks and Applications - Project MindCatcher is an art/research project which has the intention to explore the potential of interactive artistic environments for measuring and a better...  相似文献   
79.
Sohrabi  M. 《Analysis Mathematica》2021,47(2):421-435
Analysis Mathematica - In this paper, we discuss measure theoretic characterizations for Moore-Penrose inverse of Lambert conditional operators, denoted by (MwEMu)?, in some operator classes...  相似文献   
80.
Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.  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