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   1585984篇
  免费   32219篇
  国内免费   8370篇
化学   696687篇
晶体学   20906篇
力学   76176篇
综合类   113篇
数学   246344篇
物理学   387109篇
无线电   199238篇
  2021年   14822篇
  2020年   17403篇
  2019年   17544篇
  2018年   17137篇
  2017年   15654篇
  2016年   31264篇
  2015年   22138篇
  2014年   32808篇
  2013年   78615篇
  2012年   43277篇
  2011年   43507篇
  2010年   42815篇
  2009年   47253篇
  2008年   45825篇
  2007年   44076篇
  2006年   46425篇
  2005年   41332篇
  2004年   40985篇
  2003年   37850篇
  2002年   37973篇
  2001年   36764篇
  2000年   32283篇
  1999年   29317篇
  1998年   27587篇
  1997年   27384篇
  1996年   26965篇
  1995年   24689篇
  1994年   24189篇
  1993年   23561篇
  1992年   23374篇
  1991年   23542篇
  1990年   22369篇
  1989年   22015篇
  1988年   21246篇
  1987年   19925篇
  1986年   18726篇
  1985年   25236篇
  1984年   26398篇
  1983年   22332篇
  1982年   23679篇
  1981年   22877篇
  1980年   22120篇
  1979年   22066篇
  1978年   23326篇
  1977年   22893篇
  1976年   22476篇
  1975年   21172篇
  1974年   20802篇
  1973年   21319篇
  1972年   15494篇
排序方式: 共有10000条查询结果,搜索用时 15 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