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   27912篇
  免费   4920篇
  国内免费   4056篇
化学   20497篇
晶体学   302篇
力学   1656篇
综合类   251篇
数学   3115篇
物理学   11067篇
  2024年   108篇
  2023年   636篇
  2022年   1063篇
  2021年   1157篇
  2020年   1216篇
  2019年   1188篇
  2018年   1036篇
  2017年   990篇
  2016年   1439篇
  2015年   1438篇
  2014年   1626篇
  2013年   2129篇
  2012年   2369篇
  2011年   2361篇
  2010年   1689篇
  2009年   1581篇
  2008年   1777篇
  2007年   1586篇
  2006年   1465篇
  2005年   1341篇
  2004年   1016篇
  2003年   863篇
  2002年   896篇
  2001年   707篇
  2000年   632篇
  1999年   656篇
  1998年   523篇
  1997年   465篇
  1996年   456篇
  1995年   382篇
  1994年   351篇
  1993年   296篇
  1992年   229篇
  1991年   227篇
  1990年   246篇
  1989年   153篇
  1988年   116篇
  1987年   83篇
  1986年   92篇
  1985年   96篇
  1984年   45篇
  1983年   48篇
  1982年   38篇
  1981年   26篇
  1980年   14篇
  1979年   6篇
  1977年   3篇
  1957年   5篇
  1936年   4篇
  1916年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Herein, we propose the construction of a sandwich-structured host filled with continuous 2D catalysis–conduction interfaces. This MoN-C-MoN trilayer architecture causes the strong conformal adsorption of S/Li2Sx and its high-efficiency conversion on the two-sided nitride polar surfaces, which are supplied with high-flux electron transfer from the buried carbon interlayer. The 3D self-assembly of these 2D sandwich structures further reinforces the interconnection of conductive and catalytic networks. The maximized exposure of adsorptive/catalytic planes endows the MoN-C@S electrode with excellent cycling stability and high rate performance even under high S loading and low host surface area. The high conductivity of this trilayer texture does not compromise the capacity retention after the S content is increased. Such a job-synergistic mode between catalytic and conductive functions guarantees the homogeneous deposition of S/Li2Sx, and avoids thick and devitalized accumulation (electrode passivation) even after high-rate and long-term cycling.  相似文献   
2.
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants...  相似文献   
3.
4.
5.
JPC – Journal of Planar Chromatography – Modern TLC - A new high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of...  相似文献   
6.
7.
8.
Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO2‐NH2) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO2‐NH2 catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO2‐NH2 catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
9.
10.
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting.  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