全文获取类型
收费全文 | 701篇 |
免费 | 39篇 |
国内免费 | 2篇 |
专业分类
化学 | 607篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 74篇 |
物理学 | 52篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 3篇 |
2021年 | 46篇 |
2020年 | 15篇 |
2019年 | 15篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 31篇 |
2015年 | 24篇 |
2014年 | 25篇 |
2013年 | 38篇 |
2012年 | 44篇 |
2011年 | 47篇 |
2010年 | 29篇 |
2009年 | 31篇 |
2008年 | 43篇 |
2007年 | 50篇 |
2006年 | 44篇 |
2005年 | 39篇 |
2004年 | 30篇 |
2003年 | 34篇 |
2002年 | 24篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有742条查询结果,搜索用时 46 毫秒
731.
Stefania Pragliola Chiara Costabile Francesca Di Bartolomeo Pasquale Longo 《Macromolecular rapid communications》2004,25(10):995-999
Summary: Copolymerizations of propene and buta‐1,3‐diene performed in the presence of rac‐[CH2(3‐tert‐butyl‐1‐indenyl)2]ZrCl2 and methylaluminoxane (MAO) have been investigated. Buta‐1,3‐diene gives prevailingly primary coordination to the metal, producing overall 1,2 units. Cyclopropane and cyclopentane rings, although in low amounts, are also obtained. The presence of butadiene would be responsible for some regioirregular 2,1‐inserted propene units, which at high temperatures give rearrangement to 3,1 units.
732.
733.
734.
735.
Luciano Di Maio Pio Iannelli Stefania Pragliola Antonio Roviello Augusto Sirigu 《Journal of Polymer Science.Polymer Physics》1998,36(3):433-438
Preliminary results on the synthesis and characterization of anisotropic networks, oriented on a macroscopic scale, are reported. Fiber samples of segmented thermotropic liquid-crystalline polymers bearing the oxypentenyl lateral substituent have been crosslinked via thermally activated radical reaction. This was made possible by immersion of fiber samples in dichloromethane containing t-butylperoxybenzoate as activating agent, thus allowing its diffusion in the samples. Subsequent annealing at 145°C brings us to an anisotropic network with no loss of the original orientation. A mesophase is stabilized and no structural modification is observed by heating samples from room temperature up to 400°C, where thermal decomposition takes place. Crosslinked fibers exhibit good tensile properties, at both room temperature and at 150°C. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 433–438, 1998 相似文献
736.
Francesca Pescosolido Luca Montaina Rocco Carcione Sara Politi Roberto Matassa Felicia Carotenuto Stefania Annarita Nottola Paolo Di Nardo Emanuela Tamburri 《Macromolecular bioscience》2023,23(11):2300132
Conductive hybrid xanthan gum (XG)–polyaniline (PANI) biocomposites forming 3D structures able to mimic electrical biological functions are synthesized by a strong-acid free medium. In situ aniline oxidative chemical polymerizations are performed in XG water dispersions to produce stable XG–PANI pseudoplastic fluids. XG–PANI composites with 3D architectures are obtained by subsequent freeze-drying processes. The morphological investigation highlights the formation of porous structures; UV–vis and Raman spectroscopy characterizations assess the chemical structure of the produced composites. I–V measurements evidence electrical conductivity of the samples, while electrochemical analyses point out their capability to respond to electric stimuli with electron and ion exchanges in physiological-like environment. Trial tests on prostate cancer cells evaluate biocompatibility of the XG–PANI composite. Obtained results demonstrate that a strong acid-free route produces an electrically conductive and electrochemically active XG–PANI polymer composite. The investigation of charge transport and transfer, as well as of biocompatibility properties of composite materials produced in aqueous environments, brings new perspective for exploitation of such materials in biomedical applications. In particular, the developed strategy can be used to realize biomaterials working as scaffolds that require electrical stimulations for inducing cell growth and communication or for biosignals monitoring and analysis. 相似文献
737.
In this work, analysis of the response to vibrations of a small building equipped with an electromechanical vibration absorber is investigated. The case of harmonic excitation with constant or time dependent frequencies is considered. The interaction between the structure and the energy source is analyzed via the Sommerfeld effect inside the resonance region. The resonance capture and the vibration reduction are displayed by the time history displacement of the last story. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
738.
Dr. Matteo Corrieri Dr. Lucia De Crescentini Prof. Fabio Mantellini Dr. Giacomo Mari Dr. Stefania Santeusanio Prof. Gianfranco Favi 《European journal of organic chemistry》2023,26(21):e202300242
An oxidative cyclization of electron-rich α-arylhydrazones promoted by phenyliodine bis(trifluoroacetate) (PIFA) has been accomplished. This metal-free, chemoselective transformation allows to obtain synthetically and medicinally important N-amino-1H-indoles, obviating the need for pre-functionalization of substrates. 相似文献
739.
Stefania Pragliola Elio Forlenza Pasquale Longo 《Macromolecular rapid communications》2001,22(10):783-786
C2‐symmetric zirconocenes activated by methylaluminoxane were utilized as catalysts in the polymerization of 1,3‐diolefins. The results indicate that the most crowded catalytic precursor rac[CH2(3‐tert‐butyl‐1‐indenyl)2]ZrCl2 ( 1 ) is also the most active one, giving 1,4‐polymerization of 1,3‐butadiene and (Z)‐1,3‐pentadiene and 1,2‐polymerization of (E)‐1,3‐pentadiene and 4‐methyl‐1,3‐pentadiene. Probably, the different behavior of 1 with respect to other C2‐symmetric zirconocenes utilized is due to the different stability of the bond between the last inserted monomer unit and the metal, as well as to the coordination of incoming monomer. 相似文献
740.
Maurizio Penco Luciana Sartore Stefania Della Sciucca Alberto D'Amore 《Macromolecular Symposia》2005,228(1):255-262
Mass-variation measurements were carried out on carbon black (CB)-poly(vinyl chloride) (PVC) composite film with 40% by weight of di(2-ethylhexyl)-phthalate (DOP), cast on resonant piezo-layer (RPL) elements of lead zirconat titanate (PZT). Even if anomalous diffusion is predicted by fitting the data with Mt/M∞=ktα, the fractional uptake Mt/M∞ is linear with the square root of the time up to Mt/M∞=0.6, suggesting Fickian behavour. The anomalous values of α are probably due to experimental time lag. A dependence of the diffusion on the morphology of the material and the penetrant shape and flexibility has been found. 相似文献