全文获取类型
收费全文 | 414篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
化学 | 221篇 |
晶体学 | 4篇 |
力学 | 39篇 |
数学 | 80篇 |
物理学 | 88篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 24篇 |
2017年 | 17篇 |
2016年 | 39篇 |
2015年 | 12篇 |
2014年 | 34篇 |
2013年 | 47篇 |
2012年 | 33篇 |
2011年 | 35篇 |
2010年 | 28篇 |
2009年 | 24篇 |
2008年 | 15篇 |
2007年 | 20篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 6篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有432条查询结果,搜索用时 15 毫秒
101.
Mir Ali?FarajzadehEmail author Mortaza?Ebrahimi Ali?Ranji Elham?Feyz Vali?Bejani Ramin?Maleki 《Mikrochimica acta》2005,150(2):173-177
This study describes the sample preparation and two chromatographic techniques for determination of Tinuvin 622 in polyethylene. The first part of the two methods consisting of dissolving the polyethylene in boiling xylene is followed by addition of a methanolic solution of potassium hydroxide. The polymeric light stabilizer, Tinuvin 622, is thereby saponified to 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (diol). Addition of the methanolic solution of the saponification reagent simultaneously precipitates the polyethylene matrix. Then the diol is quantified using either gas chromatography (GC) or high performance liquid chromatography (HPLC). For GC, a Macherey Nagel Optima-17 capillary column (30m×0.25mm ID, film thickness 0.25µm) is used. Nitrogen is used as carrier gas and make-up gas. The detection system is a flame ionization detector. For HPLC, an octadecyl silane (ODS) column (30cm×4mm, particle size 5µm) and a mobile phase methanol: water mixture (3:97, v/v) are used. Detection of analyte is carried out at 215nm. Both methods can be used to determine Tinuvin 622 in polyethylene in the concentration range of 0.02–1%, which represents the usual application concentration. 相似文献
102.
J. Hadian A. Sonboli S. Nejad Ebrahimi M. H. Mirjalili 《Chemistry of Natural Compounds》2006,42(2):175-177
The essential oil of Nepeta satureioides Boiss. from Iran was isolated by hydrodistillation in yield of 0.06% (w/w). The chemical composition of the essential oil
was analyzed by GC and GC-MS. Forty-five compounds accounting for 97.4% of the total oil were identified. The major components
were linalool (23.8%), (Z,E)-farnesol (14.7%), linalyl acetate (11.1%), β-caryophyllene (6.6%), lavandulol acetate (6.6%), caryophyllene oxide (6.4%), and (Z)-β-farnesene (3.4%). Oxygenated terpenoids were the main group of compounds.
Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 144–145, March–April, 2006. 相似文献
103.
P. Hashemi M. M. Abolghasemi A. R. Fakhari S. N. Ebrahimi S. Ahmadi 《Chromatographia》2007,66(3-4):283-286
A new, simple hydrodistillation–solvent microextraction (HD–SME) technique has been used for analysis of the volatile components
of the aerial parts of Artemisia aucheri. The components were collected in a single microdrop, and this was injected directly for gas chromatographic–mass spectrometric
(GC–MS) analysis. The effects on extraction efficiency of extraction solvent, sample mass, microdrop volume, and extraction
time were optimized by use of a simplex method. The identities of the components of HD–SME extracts were confirmed according
to their retention indexes and mass spectra with those of standards. Forty components were extracted and identified by use
of the method; 1,8-cineol (22.8%), chrysanthenone (18.16%), α-pinene (8.33%), and mesitylene (7.41%) were the major constituents.
The results obtained from the microextraction method were compared with those obtained by conventional hydrodistillation. 相似文献
104.
105.
106.
Enhanced properties of photovoltaic devices tailored with novel supramolecular structures based on reduced graphene oxide nanosheets grafted/functionalized with thiophenic materials
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Samira Agbolaghi Sara Ebrahimi Bakhshali Massoumi Saleheh Abbaspoor Raana Sarvari Farhang Abbasi 《Journal of Polymer Science.Polymer Physics》2017,55(24):1877-1889
For verifying the influence of donor–acceptor supramolecules on photovoltaic properties, different hybrids were designed and used in organic solar cells. In this respect, reduced graphene oxide (rGO) was functionalization with 2‐thiophene acetic acid (rGO‐f‐TAA) and grafted with poly(3‐dodecylthiophene) (rGO‐g‐PDDT) and poly(3‐thiophene ethanol) (rGO‐g‐PTEt) to manipulate orientation of poly(3‐hexylthiophene) (P3HT) assemblies. Face‐on, edge‐on, and flat‐on orientations were detected for assembled P3HTs on rGO and its functionalized and grafted derivatives, respectively. Alteration of P3HT orientation from face‐on to flat‐on enhanced current density (J sc), fill factor (FF), and power conversion efficiency (PCE) and thus J sc = 7.11 mA cm?2, FF = 47%, and PCE = 2.14% were acquired. By adding phenyl‐C71‐butyric acid methyl ester (PC71BM) to active layers composed of pre‐designed P3HT/rGO, P3HT/rGO‐f‐TAA, P3HT/rGO‐g‐PDDT, and P3HT/rGO‐g‐PTEt hybrids, photovoltaic characteristics further improved, demonstrating that supramolecules appropriately mediated in P3HT:PC71BM solar cells. Phase separation was more intensified in best‐performing photovoltaic systems. Larger P3HT crystals assembled onto grafted rGOs (95–143 nm) may have acted as convenient templates for the larger and more intensified phase separation in P3HT:PCBM films. The best performances were reached for P3HT:P3HT/rGO‐g‐PDDT:PCBM (J sc = 9.45 mA cm?2, FF = 54%, and PCE = 3.16%) and P3HT:P3HT/rGO‐g‐PTEt:PCBM (J sc = 9.32 mA cm?2, FF = 53%, and PCE = 3.11%) photovoltaic systems. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1877–1889 相似文献
107.
Structural Chemistry - Acidity changes of p-aminobenzoic acid (pABA) after π-stacking with substituted benzenes (SB) have been investigated using quantum mechanical calculations at the... 相似文献
108.
Farzaneh Tajfirooz Abolghasem Davoodnia Mehdi Pordel Mahmoud Ebrahimi Amir Khojastehnezhad 《应用有机金属化学》2018,32(1)
New functionalized magnetic core–shell nanoparticles, CuFe2O4@SiO2‐OP2O5H, were prepared by grafting of phosphorus pentoxide on CuFe2O4@SiO2 nanoparticles and characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, inductively coupled plasma optical emission spectrometry and vibrating sample magnetometry. The catalytic activity of CuFe2O4@SiO2‐OP2O5H as a novel catalyst was evaluated in the synthesis of 1,8‐dioxo‐octahydroxanthenes under solvent‐free conditions. The results showed that the catalyst has high activity and the desired products are obtained in high yields within short reaction times. The catalyst is readily recovered using magnetic decantation and can be used at least four times without noticeable deterioration in catalytic activity. 相似文献
109.
110.
It is known that although the Baer Criterion for injectivity holds for modules over rings with unit, it is not true for acts over an arbitrary monoid. Seeking a characterization for the Baer Criterion to hold for acts over a monoid, in this article, using the notion of completeness introduced by Giuli, we find some classes of monoids such that for acts over them the Baer Criterion holds. 相似文献