全文获取类型
收费全文 | 574篇 |
免费 | 56篇 |
国内免费 | 37篇 |
专业分类
化学 | 388篇 |
晶体学 | 4篇 |
力学 | 15篇 |
数学 | 23篇 |
物理学 | 237篇 |
出版年
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 13篇 |
2020年 | 8篇 |
2019年 | 15篇 |
2018年 | 26篇 |
2017年 | 13篇 |
2016年 | 12篇 |
2015年 | 26篇 |
2014年 | 28篇 |
2013年 | 42篇 |
2012年 | 65篇 |
2011年 | 64篇 |
2010年 | 39篇 |
2009年 | 34篇 |
2008年 | 34篇 |
2007年 | 28篇 |
2006年 | 16篇 |
2005年 | 20篇 |
2004年 | 20篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1967年 | 5篇 |
排序方式: 共有667条查询结果,搜索用时 640 毫秒
51.
L. I. Men’shikov 《Journal of Experimental and Theoretical Physics》2005,100(2):410-421
A phase transition is discussed that can occur in a plasma with substantially different transverse and longitudinal temperatures of electrons moving in a magnetic field, ?. The Debye cloud surrounding an ion sharply contracts as T∥ decreases or the magnetic field increases. The effect of larger radiative electron-ion recombination cross sections compared with their theoretical values is explained; this effect is observed in storage rings with electron cooling systems (coolers). The role played by the phase transition in the crystallization of ion beams is discussed. 相似文献
52.
A mechanism of the interlayer exchange coupling in layered structures of the Fe/Cr(001) type with rough interfaces is proposed. The theory is based on a model of the charge-induced spin density wave (SDW) formed in the chromium layer. It is shown that the effective magnetic coupling between thick ferromagnetic layers arises due to variations of the SDW vector orientation in the antiferromagnetic layer over a characteristic length ζ determined by the exchange stiffness of chromium. A general expression for the effective magnetic coupling energy E(ψ) as a function of the angle ψ between magnetic moments of the ferromagnetic layers is obtained and numerically analyzed for an arbitrary value of the parameter ρζ, where ρ is the density of monoatomic steps on the interface. For ρζ?1, the form of E(ψ) is typical of a model with the “ biquadratic” interaction, while in the case of ρζ?1, the dependence obtained differs significantly. The proposed mechanism is used to interpret the results of measurements of the interlayer exchange coupling in Fe/Cr(001) structures. 相似文献
53.
Rodríguez-Fernández J López-Fernández R Pereiro R Menéndez M Tejerina JM Sicilia A Sanz-Medel A 《Talanta》2004,62(2):421-426
Volatile sulphur compounds (VSCs) and particularly hydrogen sulphide are considered as the predominant gases causing oral malodour. In this paper, a simple alarm sensor has been developed for VSCs determination in mouth air. The device consists of a glass tube packed with a solid sensing phase. The VSCs react with the sensing phase to produce a change in the colour of the sensor visible with a naked eye.Different “reagents” were investigated to develop the sensing phase (neocuproine + Cu(II), bathocuproine + Cu(II), resazurin, 2,6-dichlorophenolindophenol and lead acetate), finding the neocuproine + Cu(II) as the best for our purposes. Also, different substrates such as Amberlite XAD-4 and XAD-7 and different trademarks of silica gel were tested as solid supports, being selected the silica gel.A device consisting of a glass tube packed with the sensing phase was optimized and tested with halitosis patients as a rapid illness test and the results compared with those obtained with a commercially available instrument, the Halimeter™, used for the determination of VSCs in mouth air. The results exhibited acceptable agreement between the proposed “qualitative” alarm sensor and a commercially available technique selected as reference, showing the possibility of using this “visual sensor” to control the halitosis and its evolution with an eventual treatment, by the own patient. 相似文献
54.
A. Yu. Men’shikova Yu. O. Skurkis T. G. Evseeva Z. P. Shkarubskaya T. B. Tennikova S. S. Ivanchev 《Russian Journal of Applied Chemistry》2004,77(12):2011-2016
Adsorption and chemisorption of bovine serum albumin on polystyrene particles obtained by dispersion polymerization and containing graft polystyrene/polyvinylpyrrolidone copolymers and carboxy groups of the initiator in the surface layer were studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 12, 2004, pp. 2036–2041.Original Russian Text Copyright © 2004 by Menshikova, Skurkis, Evseeva, Shkarubskaya, Tennikova, Ivanchev. 相似文献
55.
N. Yu. Svechnikov V. G. Stankevich A. M. Lebedev K. A. Men’shikov B. N. Kolbasov V. V. Kriventsov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(1):13-17
Homogeneous deuterated hydrocarbon films redeposited from a deuterium plasma discharge inside the T-10 tokamak vacuum chamber are studied using photoluminescence methods; EXAFS, EPR, and IR spectroscopies; and temperature measurements. The photoluminescence excitation spectra of sp 3-sp 2 nanostructures of tokamak films are compared with those of sp 2 nanostructures of C60 fullerite films. The effect of defect states on photoluminescence and its temperature quenching is discussed. It is concluded that the model of temperature luminescence quenching for homogeneous deuterated tokamak films is similar to that for amorphous a-C:H films. 相似文献
56.
The possibility of cyclotron maser cooling of the transverse motion of electrons in a beam with the oblate velocity distribution characteristic of the setups with electron cooling has been analyzed. 相似文献
57.
58.
Shaoping Fu David Arráez‐Román Javier A. Menéndez Antonio Segura‐Carretero Alberto Fernández‐Gutiérrez 《Rapid communications in mass spectrometry : RCM》2009,23(1):51-59
In this work, rapid‐resolution liquid chromatography (RRLC) coupled to electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS) and ion trap multiple mass spectrometry (IT‐MSn) has been applied to separate and characterize eleven isomers of oleuropein aglycon in fourteen Spanish extra‐virgin olive oils. After the extra‐virgin olive oil sample had been dissolved in hexane and cleaned up by a diol‐bonded phase solid‐phase extraction (SPE) cartridge, the eluting extract was resolved in methanol and analyzed on an Angilent 1200 system with a 4.6 × 150 mm, 1.8 µm Zorbax Eclipse plus C18 column. Mass spectrometry was carried out on a Bruker Daltonics microTOF mass spectrometer and a Bruker Daltonics ion trap mass spectrometer. The characterization of isomers of oleuropein aglycon was based on accurate mass data and the isotope function of characteristic fragment ions in the studied compounds by TOF‐MS, and the fragment ions were further confirmed by IT‐MSn. The fragmentation pathway of oleuropein aglycon was successfully elucidated and all possible transformations among isomers of oleuropein aglycon were suggested. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
59.
短弧氙灯是一种发光强度高,具有从紫外到红外的连续光谱的点光源。本文介绍交流供电的短弧氙灯光源,用两电极短弧氙灯实现三电极短弧氙灯性能的方法。给出了用一个系统满足各种不同发光强度、不同调制波形、不同调制频率的要求,以及在制造和使用过程中应注意的事项。 相似文献
60.
A novel efficient synthetic method for 2,2',3,3'-biphenyltetracarboxylic dianhydride 总被引:1,自引:0,他引:1
A novel approach to the synthesis of 2,2',3,3'-biphenyltetracarboxylic dianhydride is described. The target compound was prepared by a nickel-catalyzed coupling reaction of dimethy 3-chlorophthalate (3-DMCP) for 4 h at 70-80℃, followed by subsequent hydrolysis of tetra-ester in acid solution and dehydration of tetra-acid, with overall yield of 68%. The structures of the products were characterized by IR, 1H NMR and 13C NMR respectively. 相似文献