全文获取类型
收费全文 | 20644篇 |
免费 | 3181篇 |
国内免费 | 3958篇 |
专业分类
化学 | 16213篇 |
晶体学 | 438篇 |
力学 | 944篇 |
综合类 | 377篇 |
数学 | 2410篇 |
物理学 | 7401篇 |
出版年
2024年 | 22篇 |
2023年 | 171篇 |
2022年 | 509篇 |
2021年 | 524篇 |
2020年 | 556篇 |
2019年 | 614篇 |
2018年 | 540篇 |
2017年 | 557篇 |
2016年 | 773篇 |
2015年 | 897篇 |
2014年 | 1072篇 |
2013年 | 1529篇 |
2012年 | 1632篇 |
2011年 | 1702篇 |
2010年 | 1381篇 |
2009年 | 1380篇 |
2008年 | 1696篇 |
2007年 | 1537篇 |
2006年 | 1437篇 |
2005年 | 1242篇 |
2004年 | 1096篇 |
2003年 | 954篇 |
2002年 | 1090篇 |
2001年 | 870篇 |
2000年 | 735篇 |
1999年 | 543篇 |
1998年 | 339篇 |
1997年 | 316篇 |
1996年 | 270篇 |
1995年 | 251篇 |
1994年 | 211篇 |
1993年 | 220篇 |
1992年 | 180篇 |
1991年 | 145篇 |
1990年 | 134篇 |
1989年 | 119篇 |
1988年 | 86篇 |
1987年 | 85篇 |
1986年 | 56篇 |
1985年 | 45篇 |
1984年 | 43篇 |
1983年 | 33篇 |
1982年 | 31篇 |
1981年 | 40篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Optimizing Optoelectronic Properties of Pyrimidine‐Based TADF Emitters by Changing the Substituent for Organic Light‐Emitting Diodes with External Quantum Efficiency Close to 25 % and Slow Efficiency Roll‐Off 下载免费PDF全文
Kailong Wu Tao Zhang Lisi Zhan Dr. Cheng Zhong Prof. Shaolong Gong Prof. Nan Jiang Prof. Zheng‐Hong Lu Prof. Chuluo Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10860-10866
A series of green butterfly‐shaped thermally activated delayed fluorescence (TADF) emitters, namely PXZPM , PXZMePM , and PXZPhPM , are developed by integrating an electron‐donor (D) phenoxazine unit and electron‐acceptor (A) 2‐substituted pyrimidine moiety into one molecule via a phenyl‐bridge π linkage to form a D –π–A–π–D configuration. Changing the substituent at pyrimidine unit in these emitters can finely tune their emissive characteristics, thermal properties, and energy gaps between the singlet and triplet states while maintaining frontier molecular orbital levels, and thereby optimizing their optoelectronic properties. Employing these TADF emitters results in a green fluorescent organic light‐emitting diode (OLED) that exhibits a peak forward‐viewing external quantum efficiency (EQE) close to 25 % and a slow efficiency roll‐off characteristic at high luminance. 相似文献
982.
983.
984.
Inside Back Cover: Stepwise Assembly of MII7 Clusters Revealed by Mass Spectrometry,EXAFS, and Crystallography (Chem. Eur. J. 51/2016) 下载免费PDF全文
985.
Liqing Liu Kunquan Hong Xing Ge Mingxiang Xu 《Applied Physics A: Materials Science & Processing》2014,115(4):1147-1150
Copper oxide (CuO) is a p-type semiconductor with a band gap of 1.2 eV, which is well known in high-temperature superconductor and antiferromagnetic (AFM) materials through Cu–O–Cu super-exchange interaction. In this paper, we report the strong anisotropic ferromagnetism (FM) in aligned CuO nanorod arrays synthesized by a microwave-assisted hydrothermal method. The transmission electron microscopy (TEM) image shows that the CuO nanorod consists of a large number of smaller nanorods with almost the same growth direction. The X-ray diffraction (XRD) pattern indicates that the CuO nanorods are well crystallized with highly preferred orientation of the [020] direction. These CuO nanorod arrays show room-temperature ferromagnetism, with strong magnetic anisotropy when the magnetic field is applied perpendicular or parallel to the rod axis. This phenomenon of room-temperature ferromagnetism in those aligned CuO nanorods might originate from uncompensated surface spins and shape anisotropy of the nanorods. 相似文献
986.
987.
988.
989.
Infrastructure systems such as power and water supplies make up the cornerstone of modern society which is essential for the functioning of a society and its economy. They become more and more interconnected and interdependent with the development of scientific technology and social economy. Risk and vulnerability analysis of interdependent infrastructures for security considerations has become an important subject, and some achievements have been made in this area. Since different infrastructure systems have different structural and functional properties, there is no universal all-encompassing ‘silver bullet solution’ to the problem of analyzing the vulnerability associated with interdependent infrastructure systems. So a framework of analysis is required. This paper takes the power and water systems of a major city in China as an example and develops a framework for the analysis of the vulnerability of interdependent infrastructure systems. Four interface design strategies based on distance, betweenness, degree, and clustering coefficient are constructed. Then two types of vulnerability (long-term vulnerability and focused vulnerability) are illustrated and analyzed. Finally, a method for ranking critical components in interdependent infrastructures is given for protection purposes. It is concluded that the framework proposed here is useful for vulnerability analysis of interdependent systems and it will be helpful for the system owners to make better decisions on infrastructure design and protection. 相似文献
990.
<正>Two new terpenes,wilfornine H(1) and triptobenzene Q(2) were isolated from Tripterygium wilfordii,as well as 11 terpenes. Their structures were elucidated by spectroscopic methods.Compounds 5,9-13 showed significant immunosuppressive activities. 相似文献