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   357619篇
  免费   2363篇
  国内免费   971篇
化学   151743篇
晶体学   5094篇
力学   20847篇
综合类   6篇
数学   71920篇
物理学   111343篇
  2021年   1670篇
  2020年   1845篇
  2019年   2032篇
  2018年   18823篇
  2017年   19291篇
  2016年   12189篇
  2015年   3802篇
  2014年   4039篇
  2013年   9532篇
  2012年   14023篇
  2011年   27936篇
  2010年   17041篇
  2009年   17312篇
  2008年   22739篇
  2007年   27750篇
  2006年   8215篇
  2005年   14458篇
  2004年   10939篇
  2003年   10544篇
  2002年   7750篇
  2001年   6858篇
  2000年   5539篇
  1999年   4019篇
  1998年   3300篇
  1997年   3245篇
  1996年   3158篇
  1995年   2877篇
  1994年   2699篇
  1993年   2568篇
  1992年   2895篇
  1991年   2844篇
  1990年   2754篇
  1989年   2567篇
  1988年   2641篇
  1987年   2631篇
  1986年   2443篇
  1985年   3143篇
  1984年   3393篇
  1983年   2790篇
  1982年   2972篇
  1981年   2937篇
  1980年   2795篇
  1979年   2890篇
  1978年   2997篇
  1977年   2909篇
  1976年   2992篇
  1975年   2770篇
  1974年   2734篇
  1973年   2923篇
  1972年   1838篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
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   
123.
124.
125.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
126.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
127.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
128.
The European Physical Journal E - The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron...  相似文献   
129.
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual polytope.  相似文献   
130.
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