全文获取类型
收费全文 | 241篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
化学 | 93篇 |
晶体学 | 2篇 |
力学 | 14篇 |
综合类 | 1篇 |
数学 | 22篇 |
物理学 | 119篇 |
出版年
2023年 | 3篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 13篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 17篇 |
2008年 | 11篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1998年 | 12篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有251条查询结果,搜索用时 15 毫秒
181.
Mansor Bin Ahmad Kamyar Shameli Mei Yen Tay Mohd Zobir Hussein Jenn Jye Lim 《Research on Chemical Intermediates》2014,40(2):817-832
The purpose of this study was to investigate the antibacterial effect of silver nanoparticles in chitosan–poly(ethylene glycol) suspension. The silver nanoparticles (AgNPs) were prepared by use of an environmentally benign method from chitosan (Cts) and poly(ethylene glycol) (PEG) at moderate temperature and with stirring for different times. Silver nitrate (AgNO3) was used as the metal precursor and Cts and PEG were used as solid support and polymeric stabilizer, respectively. The antibacterial activity of silver–chitosan–poly(ethylene glycol) nanocomposites (Ag–Cts–PEG NCs) against Staphylococcus aureus, Micrococcus luteum, Pseudomonas aeruginosa, and Escherichia coli was tested by use of the Mueller–Hinton agar disk-diffusion method. Formation of AgNPs was determined by UV–visible spectroscopy; surface plasmon absorption maxima were observed at 415–430 nm in the UV–visible spectrum. The peaks in the XRD pattern confirmed that the AgNPs had a face-centered cubic structure; peaks of contaminated crystalline phases were not observed. Transmission electron microscopy (TEM) revealed that the AgNPs synthesized were spherical. The optimum stirring time for synthesis of the smallest particle size (mean diameter 5.50 nm) was 12 h. The AgNPs in Cts–PEG were effective against all the bacteria tested. Higher antibacterial activity was observed for AgNPs with smaller size. These results suggest that AgNPs can be used as an effective inhibitor of bacteria and can be used in medical applications. These results also suggest that AgNPs were successfully synthesized in Cts–PEG suspension at moderate temperature with different stirring times. 相似文献
182.
Madelyn Qin Yi Tay Dr. Yunpeng Lu Dr. Rakesh Ganguly Dr. Dragoslav Vidović 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6628-6631
Our recently synthesised phosphorus dication is observed to activate water (and methanol) under reactions conditions atypical for other systems containing a non‐metal centre. This particular activation described as oxidative addition is quite rare and has been reserved exclusively for a couple of metal‐based compounds. 相似文献
183.
G. Fu N.H. Loh S.B. Tor B.Y. Tay Y. Murakoshi R. Maeda 《Applied Physics A: Materials Science & Processing》2005,81(3):495-500
The micro powder injection molding (μPIM) process was used to fabricate metallic microstructures in this paper. The production of 316L stainless steel microstructures arrays with the dimensions of ∅ 100 μm×height200 μmand∅ 60 μm × height 191 μm is presented. Injection molding was conducted on a conventional injection molding machine and silicon mold inserts with vertical sidewall made by deep reactive ion etching (DRIE) were used. Molded parts with microstructures were well obtained after selecting suitable processing parameters based on the feedstock characteristics. Then the molded parts were debound catalytically and sintered. Sintering at different temperature was conducted under vacuum. The effects of sintering temperatures were evaluated based on the polished and etched micrographs of the sintered microstructures. Finally Young’s Modulus of sintered microstructure was evaluated using nano-indenter.PACS 81.20.Ev 相似文献
184.
L. Liu N.H. Loh B.Y. Tay S.B. Tor Y. Murakoshi R. Maeda 《Applied Physics A: Materials Science & Processing》2006,83(1):31-36
Micro metal injection molding (μMIM) is being developed by some researchers for possible mass production of metallic microcomponents. Knowledge of densification and grain growth of structures in the micrometer regime is important for the design of microcomponents due to their impacts on dimensional tolerance and mechanical properties. In this paper, the effects of sintering temperature and time on densification and grain growth of stainless steel microsize structures fabricated by μMIM were investigated. In particular, the density of the microsize structures was compared with that of the components, dimensions in the millimeter range, on which the microsize structures reside. Models proposed by Kang, Brook, and Zhao and Harmer were used to study the densification and grain growth kinetics of microsize structures of ∅100μmat the final stage of sintering. Dense layers were formed on the microsize structures. Thus, the density of the microsize structures is higher than that of the microstructured components. The thickness of the dense layers increased with either increasing temperature or time. Zhao and Harmer’s model for lattice diffusion controlled densification and Brook’s grain growth model for lattice diffusion controlled pore drag exhibited good fits for the experimental results of microsize structures. PACS 81.20.Ev 相似文献
185.
186.
Tiong-Seng Tay 《Discrete and Computational Geometry》1995,13(1):203-216
We give purely combinatorial proofs of the lower-bound theorems for pseudomanifolds with or without boundary. 相似文献
187.
188.
This paper represents an optical method which is based on speckle-shearing interferometry for the measurement of surface coordinates and slopes. The technique enables generation of carrier fringes which measure surface coordinates, or displacement derivative fringes which measure surface slope. The theory of the method as well as some experimental results are presented. 相似文献
189.
190.