全文获取类型
收费全文 | 260篇 |
免费 | 8篇 |
专业分类
化学 | 219篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 13篇 |
物理学 | 31篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 22篇 |
2020年 | 14篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 20篇 |
2012年 | 19篇 |
2011年 | 19篇 |
2010年 | 10篇 |
2009年 | 14篇 |
2008年 | 16篇 |
2007年 | 15篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1990年 | 3篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
排序方式: 共有268条查询结果,搜索用时 15 毫秒
61.
Sandra Paszkiewicz Iman Taraghi Daria Pawlikowska Anna Szymczyk Izabela Irska Rafal Stanik Amelia Linares Tiberio A. Ezquerra Elbieta Piesowicz 《先进技术聚合物》2019,30(12):2983-2992
In this article, postconsumer poly (ethylene glycol‐co‐1,4‐cyclohexanedimethanol terephthalate) (PET‐G) foils have been modified with three types of carbon nanofillers that differ in size and shape, ie, multiwalled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNP), and nanosized carbon black (nCB), thus enabling the reusage of recyclate in receiving new functional materials. The series of polymer hybrid nanocomposites have been prepared via a two‐stage polycondensation process, be means of glycolysis of postconsumer PET‐G foil, followed by polycondensation in the presence of carbon nanofillers. The scanning electron microscopy revealed that nanoadditives were uniformly dispersed into the whole volume of polymer matrix. The results present the synergistic effect of hybrid system of nanofillers in improving tensile properties of PET‐G. It has been found that the incorporation of three types of carbon nanofillers has not affected the glass transition temperature of the polymer matrix. Moreover, the incorporation of carbon nanofillers, and the mixture of two, or even three of those, caused an improvement in thermal conductivity and thermal stability. 相似文献
62.
Jerzy Radecki Izabela Grzybowska Ahmed Hameurlaine Wim Dehaen 《Analytical sciences》2004,20(11):1599-1603
Oligocarbazoles have been applied as new ionophores in liquid membrane electrodes (ISEs) destined for lead(II) determination in water samples. The oligocarbazole-containing ISEs demonstrated a close-to-Nernstian potentiometric response towards Pb2+ in the activity range 10(-7)-10(-2) M. The selectivity coefficients measured by the matched potential method (MPM) confirmed their good selectivity against common interfering mono- and doubly charged cations. The oligocarbazole-containing ISEs do not respond towards protons. Their applicability has been checked by performing the recovery test while using a sample of wastewater. 相似文献
63.
Jacek Jachymski Izabela Jó?wik 《Journal of Mathematical Analysis and Applications》2004,300(1):147-159
Recently Kirk introduced the notion of asymptotic contractions on a metric space and using ultrapower techniques he obtained an asymptotic version of the Boyd-Wong fixed point theorem. In this paper we extend this result and moreover, we give a constructive proof of it. Furthermore, we obtain a complete characterization of asymptotic contractions on a compact metric space. As a by-product we establish a separation theorem for upper semicontinuous functions satisfying some limit condition. 相似文献
64.
An efficient and simple method of modification of "inverted" porphyrin is provided by reactions of 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrinatonickel(II) 2 with dihalogenalkanes under basic conditions. The substituents are bound to the internal carbon or external nitrogen of the inverted pyrrole depending on dihalogenalkane and basic catalyst. The monomeric 2- or 21-ethoxymethyl-substituted species are formed in the reaction of 2 with dihalomethanes and sodium ethoxide or ethanol in the presence of K(2)CO(3). A novel, dimeric 21,21'-ethylene-linked derivative 11 is obtained from 2 and ethylene bromide in dichloromethane in the presence of potassium carbonate end ethanol, while application of potassium tert-butoxide promotes formation of N-bromoethyl-substituted monomer 12. Reaction of 2 with propylene bromide in the presence of proton scavenger efficiently leads to the 21-allyl-substituted monomer 14 that is a product of the HBr elimination from a transient 21-bromopropyl-substituted species. The new compounds have been identified and characterized by means of mass spectrometry and optical and NMR spectroscopies. A single-crystal X-ray analysis performed for 12 allows discussion of structural parameters concerning the macrocycle and coordination core. Formation of deprotonated species [2](-), which is proposed as a key intermediate in the alkylation reaction, has been observed spectroscopically. Chirality of the N-substituted derivatives induced by protonation of the internal carbon is observed by NMR at low temperatures. 相似文献
65.
Wojciech J. Kinart Cezary M. Kinart Izabela Tylak 《Journal of organometallic chemistry》1999,590(2):1441-260
The effect of the influence on the increase of polarity of the solvent on the selectivity and rate of metalloene reactions of different allyltin compounds with singlet oxygen, 4-phenyl-1,2,4-triazoline-3,5-dione (TD) and diethyl azodicarboxylate has been studied. 相似文献
66.
Comparative Analysis of Acyclovir Esters Stability in Solutions: The Influence of the Substituent Structure,Kinetics, and Steric Effects 下载免费PDF全文
Monika A. Lesniewska Michał Gola Zbigniew Dutkiewicz Izabela Muszalska 《国际化学动力学杂志》2015,47(11):724-733
Reversed‐phase high‐performance liquid chromatography has been applied to the determination of acyclovir (ACV) esters such as acetate, isobutyrate, pivalate, ethoxycarbonate, and nicotinate. All analyses were carried out at laboratory temperature using a column LiChrospher RP‐18 (250 × 4 mm, 5 µm) and a proper mobile phase consisting of acetonitrile and phosphate buffer (pH 6 or 6.7) or acetonitrile and potassium dihydrogen phosphate, and acetic acid. The methods were validated by the determination of the following parameters: selectivity, precision, accuracy, and linearity. Kinetic studies on the hydrolysis were investigated in solutions at 310 K over the pH range 0.42–1.38. The pH‐profiles indicated specific acid‐catalyzed and spontaneous water‐catalyzed degradation. The stability of the studied ACV esters were determined not only by steric factors. In the case of ethoxycarbonyl ester of ACV, the hydrolysis was a two‐step reaction. 相似文献
67.
68.
Michał Gacki Karolina Kafarska Anna Pietrzak Izabela Korona-Glowniak Wojciech M. Wolf 《Journal of Saudi Chemical Society》2019,23(3):346-354
Three metal complexes with empirical formulae [Mn(theop)2(H2O)4] (1), [Co(theop)2(H2O)4] (2), [Ni(theop)2(H2O)4] (3), (where: theop?=?theophylline) were synthesized and characterized by elemental analysis, FTIR- spectroscopy and thermal decomposition techniques. Their crystal structures were determined by single crystal Xray diffraction analysis. Complexes are isomorphous and crystallise in the monocyclic space group P21/c. Their thermal behavior was studied by TGA methods under non-isothermal condition in air. Upon heating all compounds decompose progressively to metal oxides, which are the final products of pyrolysis. Furthermore, antimicrobial and antioxidant activity of the complexes was examined. 相似文献
69.
70.
Izabela Jurewicz Alice A. K. King Patnarin Worajittiphon Piyapong Asanithi Eric W. Brunner Richard P. Sear Thomas J. C. Hosea Joseph L. Keddie Alan B. Dalton 《Macromolecular rapid communications》2010,31(7):609-615
Natural materials, such as bone and spider silk, possess remarkable properties as a result of sophisticated nanoscale structuring. They have inspired the design of synthetic materials whose structure at the nanoscale is carefully engineered or where nanoparticles, such as rods or wires, are self‐assembled. Although much work has been done in recent years to create ordered structures using diblock copolymers and template‐assisted assembly, no reports describe highly ordered, three‐dimensional nanotube arrays within a polymeric material. There are only reports of two‐dimensional network structures and structures on micrometer‐size scales. Here, we describe an approach that uses plasticized colloidal particles as a template for the self‐assembly of carbon nanotubes (CNTs) into ordered, three‐dimensional networks. The nanocomposites can be strained by over 200% and still retain high conductivity when relaxed. The method is potentially general and so may find applications in areas such as sensing, photonics, and functional composites.