全文获取类型
收费全文 | 26188篇 |
免费 | 4320篇 |
国内免费 | 2698篇 |
专业分类
化学 | 18626篇 |
晶体学 | 318篇 |
力学 | 1582篇 |
综合类 | 132篇 |
数学 | 3035篇 |
物理学 | 9513篇 |
出版年
2024年 | 14篇 |
2023年 | 540篇 |
2022年 | 608篇 |
2021年 | 819篇 |
2020年 | 1128篇 |
2019年 | 1110篇 |
2018年 | 905篇 |
2017年 | 821篇 |
2016年 | 1285篇 |
2015年 | 1247篇 |
2014年 | 1419篇 |
2013年 | 1910篇 |
2012年 | 2500篇 |
2011年 | 2574篇 |
2010年 | 1697篇 |
2009年 | 1610篇 |
2008年 | 1752篇 |
2007年 | 1586篇 |
2006年 | 1427篇 |
2005年 | 1192篇 |
2004年 | 875篇 |
2003年 | 670篇 |
2002年 | 599篇 |
2001年 | 448篇 |
2000年 | 434篇 |
1999年 | 511篇 |
1998年 | 424篇 |
1997年 | 427篇 |
1996年 | 446篇 |
1995年 | 354篇 |
1994年 | 303篇 |
1993年 | 233篇 |
1992年 | 234篇 |
1991年 | 201篇 |
1990年 | 170篇 |
1989年 | 142篇 |
1988年 | 95篇 |
1987年 | 109篇 |
1986年 | 88篇 |
1985年 | 82篇 |
1984年 | 47篇 |
1983年 | 43篇 |
1982年 | 35篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
Tailorable PC71BM Isomers: Using the Most Prevalent Electron Acceptor to Obtain High‐Performance Polymer Solar Cells
下载免费PDF全文
Xin‐Xing Zhan Xin Zhang Si‐Min Dai Shu‐Hui Li Xu‐Zhai Lu Dr. Lin‐Long Deng Prof. Su‐Yuan Xie Prof. Rong‐Bin Huang Prof. Lan‐Sun Zheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18709-18713
Despite being widely used as electron acceptor in polymer solar cells, commercially available PC71BM (phenyl‐C71‐butyric acid methyl ester) usually has a “random” composition of mixed regioisomers or stereoisomers. Here PC71BM has been isolated into three typical isomers, α‐, β1‐ and β2‐PC71BM, to establish the isomer‐dependent photovoltaic performance on changing the ternary composition of α‐, β1‐ and β2‐PC71BM. Mixing the isomers in a ratio of α/β1/β2=8:1:1 resulted in the best power conversion efficiency (PCE) of 7.67 % for the polymer solar cells with PTB7:PC71BM as photoactive layer (PTB7=poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]]). The three typical PC71BM isomers, even though sharing similar LUMO energy levels and light absorption, render starkly different photovoltaic performances with average‐performing PCE of 1.28–7.44 % due to diverse self‐aggregation of individual or mixed PC71BM isomers in the otherwise same polymer solar cells. 相似文献
73.
A Self‐Assembled Superhydrophobic Electrospun Carbon–Silica Nanofiber Sponge for Selective Removal and Recovery of Oils and Organic Solvents 下载免费PDF全文
Ming Hang Tai Benny Yong Liang Tan Jermyn Juay Dr. Darren D. Sun Prof. James O. Leckie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5395-5402
An oil spill needs timely cleanup before it spreads and poses serious environmental threat to the polluted area. This always requires the cleanup techniques to be efficient and cost‐effective. In this work, a lightweight and compressible sponge made of carbon–silica nanofibers is derived from electrospinning nanotechnology that is low‐cost, versatile, and readily scalable. The fabricated sponge has high porosity (>99 %) and displays ultra‐hydrophobicity and superoleophilicity, thus making it a suitable material as an oil adsorbent. Owing to its high porosity and low density, the sponge is capable of adsorbing oil up to 140 times its own weight with its sorption rate showing solution viscosity dependence. Furthermore, sponge regeneration and oil recovery are feasible by using either cyclic distillation or mechanical squeezing. 相似文献
74.
75.
Gold‐Catalyzed Fluorination–Hydration: Synthesis of α‐Fluorobenzofuranones from 2‐Alkynylphenol Derivatives 下载免费PDF全文
Qiang Wang Yu Jiang Run Sun Prof. Dr. Xiang‐Ying Tang Prof. Dr. Min Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14739-14745
The AuI‐catalyzed fluorination–hydration of 2‐alkynylphenol derivatives in the presence of Selectfluor [1‐chloromethyl‐4‐fluoro‐1,4‐diazoniabicyclo‐[2.2.2]octane bis(tetrafluoroborate)] has been developed. This method provides straightforward access to α‐fluorobenzofuranones with the construction of C?O, C=O, and C?F bonds in a single step on the basis of an AuI/AuIII redox catalytic cycle. Several control experiments, including the asymmetric variant of this reaction, were also conducted to gain insight into the reaction mechanism. 相似文献
76.
77.
78.
79.
The traditional passive absorber is fully effective within a narrow and certain frequency band.To solve this problem,a time-delayed acceleration feedback is introduced to convert a passive absorber into an active one.Both the inherent and the intentional time delays are included.The former mainly comes from signal acquiring and processing,computing,and applying the actuation force,and its value is fixed.The latter is introduced in the controller,and its value is actively adjustable.Firstly,the mechanical model is established and the frequency response equations are obtained.The regions of stability are delineated in the plane of control parameters.Secondly,the design scheme of control parameters is performed to help select the values of the feedback gain and time delay.Thirdly,the experimental studies are conducted.Effects of both negative and positive feedback control are investigated.Experimental results show that the proper choices of control parameters may broaden the effective frequency band of vibration absorption.Moreover,the time-delayed absorber greatly suppresses the resonant response of the primary system when the passive absorber totally fails.The experimental results are in good agreement with the theoretical predictions and numerical simulations. 相似文献
80.