全文获取类型
收费全文 | 7754篇 |
免费 | 459篇 |
国内免费 | 242篇 |
专业分类
化学 | 5771篇 |
晶体学 | 64篇 |
力学 | 333篇 |
综合类 | 17篇 |
数学 | 975篇 |
物理学 | 1295篇 |
出版年
2024年 | 17篇 |
2023年 | 110篇 |
2022年 | 365篇 |
2021年 | 374篇 |
2020年 | 321篇 |
2019年 | 322篇 |
2018年 | 285篇 |
2017年 | 233篇 |
2016年 | 405篇 |
2015年 | 292篇 |
2014年 | 314篇 |
2013年 | 686篇 |
2012年 | 524篇 |
2011年 | 577篇 |
2010年 | 340篇 |
2009年 | 299篇 |
2008年 | 382篇 |
2007年 | 367篇 |
2006年 | 273篇 |
2005年 | 244篇 |
2004年 | 217篇 |
2003年 | 196篇 |
2002年 | 204篇 |
2001年 | 116篇 |
2000年 | 107篇 |
1999年 | 88篇 |
1998年 | 53篇 |
1997年 | 69篇 |
1996年 | 58篇 |
1995年 | 43篇 |
1994年 | 55篇 |
1993年 | 42篇 |
1992年 | 45篇 |
1991年 | 34篇 |
1990年 | 54篇 |
1989年 | 27篇 |
1988年 | 29篇 |
1987年 | 30篇 |
1986年 | 30篇 |
1985年 | 36篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 29篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1975年 | 7篇 |
排序方式: 共有8455条查询结果,搜索用时 0 毫秒
171.
Tailoring of carboxyl‐decorated magnetic latex particles using seeded emulsion polymerization 下载免费PDF全文
Talha Jamshaid Mohamed M. Eissa Quentin Lelong Anne Bonhommé Geraldine Augsti Nadia Zine Abdelhamid Errachid Abdelhamid Elaissari 《先进技术聚合物》2017,28(9):1088-1096
In this research, submicron and carboxyl‐functionalized magnetic latex particles were elaborated by using seeded emulsion polymerization technique in presence of oil‐in‐water (o/w) magnetic emulsion as seed. The polymerization conditions were optimized in order to get well‐defined latex particles with magnetic core and polymer shell bearing carboxylic (–COOH) functionality. Starting from (o/w) magnetic emulsion as seed, synthesis process was performed by copolymerization of styrene (St) monomer with the cross‐linker divinylbenzene (DVB) in presence of 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as a carboxyl‐bearing initiator. The prepared magnetic latex particles were first characterized in terms of particle size, chemical composition, morphology, magnetic properties, magnetic content, and colloidal stability using various techniques, e.g. particle size analyzer using dynamic light scattering (DLS) technique, Fourier transform infrared, transmission electron microscopy, vibrating sample magnetometer, thermogravimetric analysis, and zeta potential measurements as a function of pH of the dispersion media, respectively. The prepared magnetic latex particles were then used as second seed for further functionalization with methacrylic acid (MAA) in order to enhance carboxylic groups on the magnetic particle's surface. The results showed that final magnetic latex particles possessed spherical morphology with core‐shell structure and enriched carboxylic acid functionality. More importantly, they exhibited superparamagnetism with high magnetic content (58.42 wt%) and high colloidal stability, which considered as the main requirements for their application in the biomedical diagnostic domains. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
172.
A parametric investigation of the friction performance of PC‐ABS parts processed by FDM additive manufacturing process 下载免费PDF全文
The friction performance is an important factor of parts processed by fused deposition modeling (FDM) for various engineering applications. It is one type of failure made of surface contact. The proper use of FDM process parameters can bring a significant reduction in friction and the amount of wear, thereby leading to a reduction in the material waste. To date, very little studies have been performed in this area. This paper investigates the effect of FDM manufacturing parameters on the friction performance of polycarbonate‐acrylonitrile butadiene styrene prototypes processed by FDM using definitive screening design and partial least squares method. The observation of surface morphology was obtained by the scanning electron microscopy to examine the effect of process parameters on the microstructure. The experimental results have shown that layer thickness, air gap, raster angle, and build orientation are the most influential factors affecting the friction performance of FDM manufactured parts. The proposed approach presented in this study provides an impetus to develop analytical modeling and functional relationships between FDM manufacturing parameters and friction performance. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
173.
174.
175.
176.
177.
178.
179.
Mohamed Amara Camara Miaomiao Tian Xiaoxia Liu Xin Liu Yujia Wang Jiqing Yang Li Yang 《Biomedical chromatography : BMC》2016,30(8):1210-1215
Natural herbal medicines are an important source of enzyme inhibitors for the discovery of new drugs. A number of natural extracts such as green tea have been used in prevention and treatment of diseases due to their low‐cost, low toxicity and good performance. The present study reports an online assay of the activity and inhibition of the green tea extract of the Glucose 6‐phosphate dehydrogenase (G6PDH) enzyme using multilayer capillary electrophoresis based immobilized enzyme microreactors (CE‐IMERs). The multilayer CE‐IMERs were produced with layer‐by‐layer electrostatic assembly, which can easily enhance the enzyme loading capacity of the microreactor. The activity of the G6PDH enzyme was determined and the enzyme inhibition by the inhibitors from green tea extract was investigated using online assay of the multilayer CE‐IMERs. The Michaelis constant (Km) of the enzyme, the IC50 and Ki values of the inhibitors were achieved and found to agree with those obtained using offline assays. The results show a competitive inhibition of green tea extract on the G6PDH enzyme. The present study provides an efficient and easy‐to‐operate approach for determining G6PDH enzyme reaction and the inhibition of green tea extract, which may be beneficial in research and the development of natural herbal medicines. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
180.
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