全文获取类型
收费全文 | 140篇 |
免费 | 2篇 |
专业分类
化学 | 76篇 |
晶体学 | 6篇 |
力学 | 5篇 |
数学 | 20篇 |
物理学 | 35篇 |
出版年
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2013年 | 17篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 1篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 15 毫秒
71.
The reduction of a theory with gauge group G to a theory which is gauge invariant with respect to a subgroup H of G is formulated in a geometrical language. It is assumed that among the physical fields considered as cross-sections of fibre bundles with structure group G there exists a section of the fibre bundle with fibre isomorphic to G/H — a Higgs field. The investigation of the broken gauge symmetry is based on the reduction theorem for structure groups of principal fibre bundles. The reduction of fields and their covariant derivatives is studied. 相似文献
72.
Prof. Dr. A. Z. Trifonov Dr. B. M. Nikolova Prof. Dr. M. D. Mikhailov Dr. B. K. Shishedjiev Dr. R. B. Kuzmanova 《Heat and Mass Transfer》1981,15(1):59-66
A method has been suggested for determining mass transfer coefficients at the liquid-liquid interface through the substance absorption in the attenuated total reflection (ATR) spectrum. The aim was achieved with a cuvette where one of the liquid phases was reduced to a 10–15 μm thick layer incorporated in a teflon membrane stuck to the optical prism and so immobilizing the liquid. The thickness indicated allows to consider the diffusion processes in both phases as one-dimensional. The mathematical model applied differs from that of A. Vignes [19] by the fact that the coupled diffusion system refers to domains with final sizes. The experimental data processing was done by computer on the basis of orthogonal expansion terms. The mathematical treatment includes the observation of the mass transfer coefficient at the interface simultaneously with that of the partition coefficient between both liquid phases. Compared with the existing direct physical methods the one suggested by us resorts to simple experimental tools and leads to quantitative results. 相似文献
73.
We consider the invariant linear connections in a multidimensional universe where a compact connected Lie groupG acts with a single orbit typeG/H. It is shown that every such connection reduces to a principal connection in a dimensionally-reduced fiber bundle over the four-dimensional spacetimeM and to a set of fields onM with a gauge group isomorphic toN/H × GL(4,R), whereN is the normalizer inG of the closed subgroupH. 相似文献
74.
Volume holograms are stored in KCl:Na crystals using the photoinduced reorientation of FA centers. The dependence of the diffraction efficiency on the directions of polarization of the recording and the reconstructing waves are shown. Experimental results are in good agreement with the calculated curves, predicted by the theory. 相似文献
75.
Zagranyarska Irena Kostova Kalina Zagranyarski Yulian Nikolova Rositsa Shivachev Boris Dimitrov Vladimir 《Molecular diversity》2020,24(4):1343-1353
Molecular Diversity - The utility of deoxy-isoequilenine synthesized from estrone as valuable 2-naphthol analogue is demonstrated in the three components Betti-condensation. A simple, efficient and... 相似文献
76.
A. S. Popov L. Hitova R. K. Atanasova S. L. Nikolova 《Crystal Research and Technology》1994,29(7):1021-1024
A special case of gas etching of GaAs substrates in the process of VPE in the presence of (Ga + In) source was investigated. The dependence of the etching rate on the source and the substrate temperature, and the AsCl3 content in the gas flow was studied. 相似文献
77.
The coordination ability of 2-oxo-2H-chromene-3-phosphonic acid with Pt(II) both in solution and in solid state is elucidated by means of conventional and linear-polarized IR spectroscopy of oriented colloid suspensions in nematic liquid crystal, 1H-, 13C-, and 31P-NMR, UV-Vis spectroscopy, positive and negative mass spectrometry (ESI and FAB), and TGV and DSC methods. A comparison with the spectroscopic data of ammonium salt of 2-oxo-2H-chromene-3-phosphonic acid is carried out as well. 相似文献
78.
Ivanov I Nikolova S Aladjov D Stefanova I Zagorchev P 《Molecules (Basel, Switzerland)》2011,16(8):7019-7042
A series of different 1-monosubstituted and 1,1-disubstituted 1,2,3,4-tetrahydro-isoquinolines was synthesized in high yields from different ketoamides. We have developed a convenient method for the synthesis of disubstituted derivatives by interaction of ketoamides with organomagnesium compounds, followed by cyclization in the presence of catalytic amounts of p-toluenesulfonic acid (PTSA). A number of substituents at the C-1 in the isoquinoline skeleton were introduced varying either carboxylic acid or organomagnesium compound. Some of the obtained 1,1-dialkyl-1,2,3,4-tetrahydro-isoquinolines possess contractile activity against guinea pig's gastric smooth muscle preparations. 相似文献
79.
L. Nedelchev A. Matharu L. Nikolova S. Hvilsted P. S. Ramanujam 《Molecular Crystals and Liquid Crystals》2013,570(1):563-575
When elliptically polarized light of appropriate wavelength corresponding to trans - cis - trans isomerisation process is incident on thin films of azobenzene polyesters, a helical structure is induced. We investigate the propagation of the exciting light beam (self-induced) as well as a probe light beam outside the absorption band through the polyester films. Investigations are carried out in one amorphous and one liquid crystalline polyester. We show that amorphous polyester after irradiation behaves like classical helical material. 相似文献
80.
D. Nikolova J. Krsti? L. Spasov D. Simeonov D. Lon?arevi? Pl. Stefanov D. Jovanovi? 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(13):2380-2385
The effect of the type of the silica gel pore structure on the surface properties of the Ni-silica gel catalyst precursors
for the vegetable oil hydrogenation process has been examined applying N2 sorption and X-ray photoelectron spectroscopy techniques. The nickel catalyst precursors with identical composition (SiO2/Ni = 1.0) has been synthesized by precipitation of Ni(NO3)2 · 6H2O solution with Na2CO3 solution on the three types of silica gel with different pore structures. It is shown that the usage of the silica gel supports
with different texture as source of SiO2 causes different location of Ni-species into the support pores and on the external surface area. The XPS data confirm the
formation of surface species with different strength of interaction and different dispersion. These surface characteristics
of the precursors will predetermine the formation of the active nickel metallic phase as well as the mass transfer of the
reactants and products to and from the catalytic sites. 相似文献