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   26646篇
  免费   3510篇
  国内免费   2723篇
化学   19720篇
晶体学   291篇
力学   1441篇
综合类   200篇
数学   3693篇
物理学   7534篇
  2024年   44篇
  2023年   419篇
  2022年   464篇
  2021年   796篇
  2020年   934篇
  2019年   926篇
  2018年   748篇
  2017年   766篇
  2016年   1191篇
  2015年   1150篇
  2014年   1397篇
  2013年   1826篇
  2012年   2389篇
  2011年   2493篇
  2010年   1729篇
  2009年   1517篇
  2008年   1825篇
  2007年   1694篇
  2006年   1613篇
  2005年   1323篇
  2004年   1067篇
  2003年   844篇
  2002年   792篇
  2001年   584篇
  2000年   449篇
  1999年   475篇
  1998年   352篇
  1997年   334篇
  1996年   363篇
  1995年   284篇
  1994年   244篇
  1993年   200篇
  1992年   206篇
  1991年   198篇
  1990年   161篇
  1989年   140篇
  1988年   98篇
  1987年   92篇
  1986年   95篇
  1985年   87篇
  1984年   74篇
  1983年   57篇
  1982年   40篇
  1981年   38篇
  1980年   41篇
  1979年   28篇
  1978年   31篇
  1977年   30篇
  1976年   27篇
  1973年   29篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
2.
3.
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with...  相似文献   
4.
In this paper,we first construct compact embeddedλ-hypersurfaces with the topology of torus which are calledλ-torus in Euclidean spaces?n^+1.Then,we give many compact immersedλ-hypersurfaces in Euclidean spaces?n^+1.  相似文献   
5.
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA.  相似文献   
6.
氧化铝晶体是一种优良的光学透明窗口材料,更是地球内部的重要组成物质.利用气炮加载结合冲击光谱测量,不仅能够获得其发光特征,并且根据光谱分布特征得到高压结构相变信息.在自主搭建的冲击光谱动态测试平台上,结合多通道辐射高温计以及ICCD瞬态光谱测试技术在40~120 GPa的压力区间,研究了c切向氧化铝晶体的辐射发光效应.在可见光波段400~700 nm区间获得了氧化铝晶体的发光光谱和辐射温度结果,证实了光谱的结构特征和表观温度值与该压力下氧化铝的结构相变存在明显的关联性.  相似文献   
7.
8.
A class of acceptor–donor–acceptor chromophoric small-molecule non-fullerene acceptors, 1–4, with difluoroboron(iii) β-diketonate (BF2bdk) as the electron-accepting moiety has been developed. Through the variation of the central donor unit and the modification on the peripheral substituents of the terminal BF2bdk acceptor unit, their photophysical and electrochemical properties have been systematically studied. Taking advantage of their low-lying lowest unoccupied molecular orbital energy levels (from −3.65 to −3.72 eV) and relatively high electron mobility (7.49 × 10−4 cm2 V−1 s−1), these BF2bdk-based compounds have been employed as non-fullerene acceptors in organic solar cells with maximum power conversion efficiencies of up to 4.31%. Moreover, bistable resistive memory characteristics with charge-trapping mechanisms have been demonstrated in these BF2bdk-based compounds. This work not only demonstrates for the first time the use of a boron(iii) β-diketonate unit in constructing non-fullerene acceptors, but also provides more insights into designing organic materials with multi-functional properties.

Boron(iii) β-diketonates have been demonstrated to serve as multi-functional materials in NFA-based OPVs and organic resistive memories.  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