全文获取类型
收费全文 | 384篇 |
免费 | 1篇 |
专业分类
化学 | 177篇 |
晶体学 | 14篇 |
力学 | 21篇 |
数学 | 25篇 |
物理学 | 148篇 |
出版年
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 10篇 |
2009年 | 12篇 |
2008年 | 25篇 |
2007年 | 9篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 9篇 |
1994年 | 3篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 6篇 |
1969年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有385条查询结果,搜索用时 31 毫秒
31.
32.
The optical effect in a liquid crystal cell containing a homeotropic layer of nematic liquid crystal (NLC) is analyzed. An
NLC layer, located between crossed polaroids and opaque in the absence of external effect, is cleared after irradiation by
an ultrasonic beam with a sharp spatial boundary. This enlightenment is suggested to be caused by the reorientation of crystal
molecules in the acoustic flows that arise under the binary effect of the layer compression in the irradiated region and the
viscous waves propagating from the layer boundaries. The flows were calculated taking into account the stress caused by the
velocity convection and crystal structure relaxation. An expression is derived for the cell transparency, and the relative
role of the convection and relaxation processes in the effect is determined. 相似文献
33.
S.V. Kozhevnikov A. RühmF. Ott N.K. PleshanovJ. Major 《Physica B: Condensed Matter》2011,406(12):2463-2466
A neutron waveguide is a three-layer structure in which a guiding layer with low optical potential is placed between two cladding layers with high optical potential. Under proper operation conditions, the neutron density is resonantly enhanced inside the guiding layer. In our experimental scheme, the neutron beam enters through the surface of the top layer at glancing angle and goes out from the edge of the guiding layer, with an angular distribution corresponding to Fraunhofer diffraction from a narrow slit. The incident neutron beam is relatively wide (0.1 mm) and highly collimated (0.01°). The outgoing sub-micron beam is extremely narrow at the outlet (0.1 μm) and more divergent (0.1°). So far only the production of unpolarized sub-micron neutron beams has been reported. Here we present first experiments on polarized sub-micron neutron beams. For these studies a polarized incident beam was used and two types of magnetic waveguides were investigated: a polarizing magnetic waveguide Fe(20 nm)/Cu(140 nm)/Fe(50 nm)//glass and a non-polarizing magnetic waveguide Py(10 nm)/Al(140 nm)/Py(50 nm)//glass (Py is permalloy). The waveguide samples were characterized by polarized neutron reflectometry. 相似文献
34.
35.
General elliptic boundary value problems with the spectral parameter appearing linearly both in the elliptic equation and in boundary conditions are considered. It is proved that the corresponding matrix operator from the Boutet de Monvel algebra is similar to an almost diagonal operator. This result is applied to prove the completeness and the summability (in the sense of Abel) of the root vectors of this operator.The support of the Rashi Foundation is gratefully acknowledged.The support of the Israel Ministry of Science and Technology is gratefully acknowledged. 相似文献
36.
Frank W. Lewis Laurence M. Harwood Michael J. Hudson Andreas Geist Valery N. Kozhevnikov Petr Distler Jan John 《Chemical science》2015,6(8):4812-4821
We report the first examples of hydrophilic 6,6′-bis(1,2,4-triazin-3-yl)-2,2′-bipyridine (BTBP) and 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) ligands, and their applications as actinide(iii) selective aqueous complexing agents. The combination of a hydrophobic diamide ligand in the organic phase and a hydrophilic tetrasulfonated bis-triazine ligand in the aqueous phase is able to separate Am(iii) from Eu(iii) by selective Am(iii) complex formation across a range of nitric acid concentrations with very high selectivities, and without the use of buffers. In contrast, disulfonated bis-triazine ligands are unable to separate Am(iii) from Eu(iii) in this system. The greater ability of the tetrasulfonated ligands to retain Am(iii) selectively in the aqueous phase than the corresponding disulfonated ligands appears to be due to the higher aqueous solubilities of the complexes of the tetrasulfonated ligands with Am(iii). The selectivities for Am(iii) complexation observed with hydrophilic tetrasulfonated bis-triazine ligands are in many cases far higher than those found with the polyaminocarboxylate ligands previously used as actinide-selective complexing agents, and are comparable to those found with the parent hydrophobic bis-triazine ligands. Thus we demonstrate a feasible alternative method to separate actinides from lanthanides than the widely studied approach of selective actinide extraction with hydrophobic bis-1,2,4-triazine ligands such as CyMe4-BTBP and CyMe4-BTPhen. 相似文献
37.
Prokhorov AM Slepukhin PA Rusinov VL Kalinin VN Kozhevnikov DN 《Chemical communications (Cambridge, England)》2011,47(27):7713-7715
Novel B,N,N-cyclometallated Pt(II) complexes of 2,2'-bipyridin-6-yl carboranes exhibit absorption and emission similar to relative Pt(II) complexes of aromatic C,N,N-ligands: the same transitions but lower intensities. DFT calculations suggest the former emits from the (3)MLCT state while for the latter the mixed (3)ICT-MLCT transitions should be considered. 相似文献
38.
In the present work, a theoretical model considering the processes of generation and losses of charged particles in the cathode
region of a glow discharge in the drift approximation for ion and electron motion is developed. Exact analytical solutions,
which can be used to calculate the current-voltage characteristics of the glow discharge in an arbitrary gas with the known
Townsend ionization coefficient, are derived. The calculated parameters of the normal glow discharge (the current density,
discharge burning voltage, and width of the space charge region) for different gases are in good agreement with the available
experimental data.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 71–77, February, 2006. 相似文献
39.
V. I. Anikeev A. Ermakova A. M. Chibiryaev I. V. Kozhevnikov P. E. Mikenin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(5):711-716
The experimental data obtained were used to construct a kinetic model of the isomerization of α-pinene in supercritical ethanol. The model took into account the influence of both temperature and pressure on the rate and selectivity of the reaction. 相似文献
40.