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   15834篇
  免费   779篇
  国内免费   184篇
化学   9845篇
晶体学   125篇
力学   660篇
综合类   3篇
数学   1609篇
物理学   2603篇
无线电   1952篇
  2024年   45篇
  2023年   167篇
  2022年   702篇
  2021年   693篇
  2020年   605篇
  2019年   683篇
  2018年   699篇
  2017年   549篇
  2016年   868篇
  2015年   601篇
  2014年   809篇
  2013年   1525篇
  2012年   1118篇
  2011年   1094篇
  2010年   748篇
  2009年   636篇
  2008年   691篇
  2007年   651篇
  2006年   474篇
  2005年   478篇
  2004年   307篇
  2003年   300篇
  2002年   253篇
  2001年   171篇
  2000年   124篇
  1999年   134篇
  1998年   80篇
  1997年   93篇
  1996年   109篇
  1995年   88篇
  1994年   79篇
  1993年   61篇
  1992年   80篇
  1991年   83篇
  1990年   57篇
  1989年   65篇
  1988年   67篇
  1987年   69篇
  1986年   69篇
  1985年   78篇
  1984年   61篇
  1983年   52篇
  1982年   52篇
  1981年   31篇
  1980年   53篇
  1979年   42篇
  1978年   50篇
  1977年   42篇
  1976年   33篇
  1974年   24篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
In present study, a simultaneous derivatization and air‐assisted liquid–liquid microextraction method combined with gas chromatography–nitrogen phosphorous detection has been developed for the determination of some phenolic compounds in biological samples. The analytes are derivatized and extracted simultaneously by a fast reaction with 1‐flouro‐2,4‐dinitrobenzene under mild conditions. Under optimal conditions low limits of detection in the range of 0.05–0.34 ng mL?1 are achievable. The obtained extraction recoveries are between 84 and 97% and the relative standard deviations are less than 7.2% for intraday (n = 6) and interday (n = 4) precisions. The proposed method was demonstrated to be a simple and efficient method for the analysis of phenols in biological samples. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
3.
4.
5.
Wireless Networks - The original version of this article unfortunately contained a mistake in the title. The correct title has been published with this erratum.  相似文献   
6.
In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of the one dimensional free particle propagator has been evaluated explicitly. With this propagator in hand, it has been shown that, even in free particle case, normal generalized uncertainty principle and doubly special relativity show very much different result.  相似文献   
7.
8.
The modulation of electron density is an effective option for efficient alternative electrocatalysts. Here, p‐n junctions are constructed in 3D free‐standing FeNi‐LDH/CoP/carbon cloth (CC) electrode (LDH=layered double hydroxide). The positively charged FeNi‐LDH in the space‐charge region can significantly boost oxygen evolution reaction. Therefore, the j at 1.485 V (vs. RHE) of FeNi‐LDH/CoP/CC achieves ca. 10‐fold and ca. 100‐fold increases compared to those of FeNi‐LDH/CC and CoP/CC, respectively. Density functional theory calculation reveals OH? has a stronger trend to adsorb on the surface of FeNi‐LDH side in the p‐n junction compared to individual FeNi‐LDH further verifying the synergistic effect in the p‐n junction. Additionally, it represents excellent activity toward water splitting. The utilization of heterojunctions would open up an entirely new possibility to purposefully regulate the electronic structure of active sites and promote their catalytic activities.  相似文献   
9.
10.
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