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   1408473篇
  免费   29782篇
  国内免费   7678篇
化学   714270篇
晶体学   20661篇
力学   76062篇
综合类   107篇
数学   246855篇
物理学   387978篇
  2021年   13486篇
  2020年   15980篇
  2019年   16102篇
  2018年   14278篇
  2016年   28716篇
  2015年   21082篇
  2014年   30570篇
  2013年   74720篇
  2012年   41984篇
  2011年   41915篇
  2010年   39442篇
  2009年   41137篇
  2008年   40170篇
  2007年   36753篇
  2006年   40769篇
  2005年   34239篇
  2004年   34263篇
  2003年   31555篇
  2002年   32177篇
  2001年   32053篇
  2000年   27059篇
  1999年   23587篇
  1998年   21519篇
  1997年   21399篇
  1996年   21299篇
  1995年   19325篇
  1994年   18752篇
  1993年   18316篇
  1992年   18676篇
  1991年   18922篇
  1990年   18109篇
  1989年   18080篇
  1988年   17701篇
  1987年   17575篇
  1986年   16567篇
  1985年   22958篇
  1984年   24067篇
  1983年   20176篇
  1982年   21833篇
  1981年   21026篇
  1980年   20357篇
  1979年   20684篇
  1978年   21913篇
  1977年   21536篇
  1976年   21300篇
  1975年   20034篇
  1974年   19739篇
  1973年   20205篇
  1972年   14685篇
  1967年   12819篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
841.
Bryostatins are a class of naturally occurring macrocyclic lactones with a unique fast developing portfolio of clinical applications, including treatment of AIDS, Alzheimer's disease, and cancer. This comprehensive account summarizes the recent progress (2014–present) in the development of bryostatins, including their total synthesis and biomedical applications. An emphasis is placed on the discussion of bryostatin 1 , the most-studied analogue to date. This review highlights the synthetic and biological challenges of bryostatins and provides an outlook on their future development.  相似文献   
842.
Monatshefte für Chemie - Chemical Monthly - A comparative analysis is performed on the stability constants $${\upbeta }_{1yn}$$ and intramolecular redox decomposition rate constants $$k_{n\; =...  相似文献   
843.
844.
Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - A method for studying the magnetic dynamics of endofullerenes M@C2n (2n = 60, 70, …) and their derivatives,...  相似文献   
845.
Tunneled metal oxides such as α-Mn8O16 (hollandite) have proven to be compelling candidates for charge-storage materials in high-density batteries. In particular, the tunnels can support one-dimensional chains of K+ ions (which act as structure-stabilizing dopants) and H2O molecules, as these chains are favored by strong H-bonds and electrostatic interactions. In this work, we examine the role of water molecules in enhancing the stability of K+-doped α-Mn8O16 (cryptomelane). The combined experimental and theoretical analyses show that for high enough concentrations of water and tunnel-ions, H2O displaces K+ ions from their natural binding sites. This displacement becomes energetically favorable due to the formation of K2+ dimers, thereby modifying the stoichiometric charge of the system. These findings have potentially significant technological implications for the consideration of cryptomelane as a Li+/Na+ battery electrode. Our work establishes the functional role of water in altering the energetics and structural properties of cryptomelane, an observation that has frequently been overlooked in previous studies.

Water displaces potassium ions and initiates the formation of a homonuclear dimer ion (K2+) in the tunnels of hollandite.  相似文献   
846.
847.
848.
849.
850.
Thin films (monolayer and bilayer) of cylinder forming polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) were shear aligned by the swelling and deswelling of a crosslinked PDMS pad that was physically adhered to the film during solvent vapor annealing. The nanostructures formed by self‐assembly were exposed to ultraviolet‐ozone to partially oxidize the PDMS, followed by calcination in air at 500 °C. In this process, the PS segments were fully decomposed, while the PDMS yielded silica nanostructures. The highly aligned PDMS cylinders were thus deposited as silica nanolines on the silicon substrate. Using a bilayer film, the center‐to‐center distance of these features were effectively halved from 38 to 19 nm. Similarly, by sequential shear‐alignment of two distinct layers, a rhombic array of silica nanolines was fabricated. This methodology provides a facile route to fabricating complex topographically patterned nanostructures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1058–1064  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