全文获取类型
收费全文 | 877篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 518篇 |
晶体学 | 2篇 |
力学 | 13篇 |
数学 | 71篇 |
物理学 | 294篇 |
出版年
2022年 | 29篇 |
2021年 | 20篇 |
2020年 | 23篇 |
2019年 | 12篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 18篇 |
2015年 | 28篇 |
2014年 | 33篇 |
2013年 | 70篇 |
2012年 | 49篇 |
2011年 | 68篇 |
2010年 | 49篇 |
2009年 | 70篇 |
2008年 | 48篇 |
2007年 | 38篇 |
2006年 | 46篇 |
2005年 | 27篇 |
2004年 | 38篇 |
2003年 | 20篇 |
2002年 | 24篇 |
2001年 | 20篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 15篇 |
1993年 | 3篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1956年 | 1篇 |
1955年 | 2篇 |
1953年 | 2篇 |
排序方式: 共有898条查询结果,搜索用时 0 毫秒
1.
In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate. 相似文献
2.
H.D. Fonseca Filho R. Prioli M.P. Pires A.S. Lopes P.L. Souza F.A. Ponce 《Applied Physics A: Materials Science & Processing》2007,89(4):945-949
Atomic-force nanolithography was used to control the nucleation sites of InAs nanostructures on InP substrates. Indentations
with a wide range of dimensions were produced on InP. InAs nanostructures were selectively grown by metal organic vapor phase
epitaxy. It is shown that the number of active nucleation sites depends on the normal force applied during nanoindentation.
Crystalline defects introduced by nanoindentation are shown to be nucleation sites for these nanostructures. The presence
of screw dislocations within the grown nanostructures further supports this observation.
PACS 81.07.-b; 68.37.Ps; 81.16.Nd 相似文献
3.
The phase diagram of the nematic mesophase present in the tetradecyltrimethylammonium bromide/sodium bromide/water ternary system was determined. A calamitic nematic mesophase (NC) was observed which extends to very high concentrations of electrolyte. The order parameters of the surfactant head group in the mesophases were studied by the NMR quadrupolar splitting of the deuterated surfactant. On increasing the temperature of nematic mesophases with low electrolyte concentrations, a phase separation occurs with the formation of a more highly ordered hexagonal phase and an isotropic phase. Diffusion measurements of the isotropic micellar solution by the NMR PFG method were used to estimate hydrodynamic radii at low surfactant concentrations and to study micelle diffusion as the concentration of the surfactant was increased to the liquid crystalline region. At higher surfactant concentrations, the diffusion coefficient reached a limiting value. The calamitic nematic mesophase in this surfactant/electrolyte/water system appears to be formed by long wormlike micelles. 相似文献
4.
5.
6.
Maria do Carmo Rangel Varela Milton Francisco de Jesus Filho Fernando Galembeck 《Hyperfine Interactions》1994,83(1):159-167
Mössbauer spectroscopy was used to follow the aging of ferrihydrite with different amounts of acetate, to achieve more crystalline products. Mössbauer spectra of fresh samples did not show any magnetic components. After two years aging, the solids presented crystalline fractions. Hematite formation was inhibited as acetate content increased in solids. For an acetate/iron molar ratio equal to 0.63 goethite was formed instead of hematite. X-ray diffraction confirmed these results. This work shows that synthetic samples can be used for elucidating the anti-hematitic effect of organic matter already detected in soils. 相似文献
7.
8.
Summary Spot tests have been described for calcium sulphate, lead sulphate, silver, thallium and formaldehyde based on the reaction with selenosulphate. In these reactions either red elemental selenium (CaSO4, CH2O) or black metal selenide (PbSO4 Tl, Ag) is formed. The limits of identification are: 0.2 mg of PbS04 or CaSO4, 2 g of Ag, 10 g of Tl, 0.2 g of CH2O.
This paper has been dedicated to Prof. Dr.Fritz Wessely, Vienna, on the occasion of his 70th birthday. 相似文献
Zusammenfassung Für Calciumsulfat, Bleisulfat, Silber, Thallium und Formaldehyd werden Tüpfelproben beschrieben, die auf Umsetzungen mit Selenosulfat beruhen. Hierbei -wird entweder rotes elementares Selen abgeschieden (CaSO4 CH2O) oder schwarze Selenide werden gebildet (PbSO4, Tl, Ag). Die Nachweisgrenzen betragen: 0,2 mg PbSO4 oder CaSO4, 2 g Ag, 10 g Tl, 0,2 g CH2O.
This paper has been dedicated to Prof. Dr.Fritz Wessely, Vienna, on the occasion of his 70th birthday. 相似文献
9.
10.