全文获取类型
收费全文 | 99586篇 |
免费 | 18525篇 |
国内免费 | 11527篇 |
专业分类
化学 | 69755篇 |
晶体学 | 1085篇 |
力学 | 6444篇 |
综合类 | 720篇 |
数学 | 11667篇 |
物理学 | 39967篇 |
出版年
2024年 | 111篇 |
2023年 | 2133篇 |
2022年 | 2286篇 |
2021年 | 3342篇 |
2020年 | 4301篇 |
2019年 | 3888篇 |
2018年 | 3461篇 |
2017年 | 3141篇 |
2016年 | 5027篇 |
2015年 | 4766篇 |
2014年 | 5890篇 |
2013年 | 7495篇 |
2012年 | 9113篇 |
2011年 | 9565篇 |
2010年 | 6453篇 |
2009年 | 6307篇 |
2008年 | 6795篇 |
2007年 | 5915篇 |
2006年 | 5550篇 |
2005年 | 4494篇 |
2004年 | 3580篇 |
2003年 | 2802篇 |
2002年 | 2784篇 |
2001年 | 2383篇 |
2000年 | 2049篇 |
1999年 | 2138篇 |
1998年 | 1796篇 |
1997年 | 1705篇 |
1996年 | 1681篇 |
1995年 | 1429篇 |
1994年 | 1263篇 |
1993年 | 1094篇 |
1992年 | 913篇 |
1991年 | 842篇 |
1990年 | 678篇 |
1989年 | 528篇 |
1988年 | 402篇 |
1987年 | 330篇 |
1986年 | 344篇 |
1985年 | 277篇 |
1984年 | 159篇 |
1983年 | 131篇 |
1982年 | 110篇 |
1981年 | 67篇 |
1980年 | 48篇 |
1979年 | 19篇 |
1978年 | 7篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1957年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The biodegradability of phtalic acid esters in marine and freshwater environments was characterized by their binding free energy with corresponding degrading enzymes. According to comprehensive biodegradation effects weights, the binding free energy values were converted into dimensionless efficacy coefficient using ratio normalization method. Then, considering comprehensive dual biodegradation effects value and the structural parameters of PAEs in both marine and freshwater environments, a 3D-QSAR pharmacophore model was constructed, five PAE derivatives (DBP−COOH, DBP−CHO, DBP−OH, DINP−NH2, and DINP−NO2) were screened out based on their environmental friendliness, functionality and stability. The prediction of biodegradation effects on five PAE derivatives by biodegradation models in marine and freshwater environment increased by 15.90 %, 15.84 %, 27.21 %, 12.33 %, and 8.32 %, and 21.57 %, 15.21 %, 20.99 %, 15.10 %, and 9.74 %, respectively. By simulating the photodegradation path of the PAE derivative molecular, it was found that DBP−OH can generate .OH and provides free radicals for the photodegradation of microplastics in the environment. 相似文献
62.
Wang Dong Ming Fei Song Xue-Ke Ye Liu Chen Jing-Ling 《The European Physical Journal C - Particles and Fields》2020,80(8):1-16
The European Physical Journal C - We study the isentropic evolution of the matter produced in relativistic heavy-ion collisions for various values of the entropy-per-baryon ratio of interest for... 相似文献
63.
This minireview describes the strategies for synthesis of fiuorinated surfactants potentially nonbioaccumulable.Various strategies have been focused on(Ⅰ) reducing the length of the perfluorocarbon chain,(Ⅱ) introducing hetero atoms into the fluorocarbon chain,(Ⅲ) introducing branch(herein and after branch means the fluoro-carbon chain section is not straight).In most cases,the surface tensions versus the surfactant concentrations have been assessed.These above strategies led to various highly fiuorinated(perfluorinated or not perfluorinated) surfactants whose chemical changes enabled to obtain novel alternatives to perfluorooctanoic acid(PFOA) and perfluorooctane sulphonate(PFOS). 相似文献
64.
65.
66.
67.
68.
69.
Synthesis and Photophysical Properties of a Sc3N@C80‐Corrole Electron Donor–Acceptor Conjugate 下载免费PDF全文
Bin Liu Hongyun Fang Prof. Xiaofang Li Wenting Cai Lipiao Bao Marc Rudolf Fabian Plass Prof. Louzhen Fan Prof. Xing Lu Prof. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):746-752
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics. 相似文献
70.