全文获取类型
收费全文 | 246篇 |
免费 | 10篇 |
专业分类
化学 | 176篇 |
晶体学 | 1篇 |
力学 | 11篇 |
数学 | 18篇 |
物理学 | 50篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 14篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 10篇 |
2013年 | 22篇 |
2012年 | 33篇 |
2011年 | 20篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 18篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2002年 | 2篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有256条查询结果,搜索用时 15 毫秒
71.
S. Halder T. Schneller R. Waser 《Applied Physics A: Materials Science & Processing》2007,87(4):705-708
Almost all platinized substrates manufactured presently use an TiO2 adhesion layer to improve the adhesion between the SiO2 and the Pt. These substrates however are stable till only 800 °C. We show that simply by replacing the TiO2 with Al2O3, the stability of the electrodes can be increased to 1000 °C and more. These substrates can be used for high temperature
depositions which standard platinized substrates cannot withstand. Further we show that dielectric thin films of BaTiO3 and (Ba,Sr)TiO3 crystallized at higher temperatures show almost a threefold increase in permittivity on these high temperature stable platinized
silicon substrates.The large increase in permittivity is attributed to an increase in grain size at high temperatures.
PACS 61.82.Fk; 68.35.Np; 68.60.Dv; 77.55.+f; 81.20.Fw 相似文献
72.
Complementary new routes to both enantiomers of N-protected pipecolic acid and the corresponding 4,5-dihydroxylated derivatives are developed, which involve stereo-divergent allylation of a chiral N-allylimine and ring-closing metathesis as key steps. 相似文献
73.
74.
The reaction of GaMe3 and InMe3 (Me = CH3) with equimolar amounts of α-tropolone forms dimethylgallium tropolonate and dimethylindium tropolonate, respectively, in high yields. Both compounds are monomeric in solution, almost planar 7-/5-ring bicyclic structures of C2v symmetry can be discussed. According to the X-ray structure determination of Me2GaTrop (Trop = C7H5O2) this compound is dimeric in the solid state and crystallizes in the monoclinic space group P21/c with 4 formula units (2 dimers) per unit cell. Me2SnTrop2 is formed by the interaction of Me2SnCl2 with LiTrop in a molar ratio. This ditropolonate is monomeric not only in solution but also in the solid state. The compound crystallizes in the triclinic space group P (Z = 4), and the molecules have a cis-structure of approximate C2-symmetry. The vibrational and NMR spectra of all compounds were measured and are partly assigned. 相似文献
75.
76.
Generation of fluorescent adducts of malondialdehyde and amino acids: toward an understanding of lipofuscin 总被引:2,自引:0,他引:2
Chowdhury PK Halder M Choudhury PK Kraus GA Desai MJ Armstrong DW Casey TA Rasmussen MA Petrich JW 《Photochemistry and photobiology》2004,79(1):21-25
Lipofuscin is a yellow-brown, highly fluorescent pigment that undergoes an age-related progressive accumulation in animal cells, mainly in postmitotic cells. It is a heterogeneous, high-molecular weight material associated with proteins, lipids and nucleic acids. Lipofuscin is implicated in many aspects of human health, including aging, oxidative stress, macular degeneration, lipid peroxidation, atherosclerosis, dementia (Alzheimer's Disease) and diseases associated with prions. Although the fluorescent properties of lipofuscin have long been recognized, neither histologists nor chemists have yet isolated the pigments themselves or characterized their optical properties. We have prepared lipofuscinlike species by reacting malondialdehyde (MDA) with cysteine (Cys). MDA:Cys adducts 3:2 and 2:2 are two of those that have been identified among the many that were present in the reaction. Whereas previous attempts to synthesize lipofuscinlike species resulted in compounds that were either nonfluorescent or emitted principally in the blue, the MDA:Cys adducts reported in this study are not only fluorescent but also emit over a broader range. 相似文献
77.
We study quantum feedback cooling of atomic motion in an optical cavity. We design a feedback algorithm that can cool the atom to the ground state of the optical potential with high efficiency despite the nonlinear nature of this problem. An important ingredient is a simplified state-estimation algorithm, necessary for a real-time implementation of the feedback loop. We also describe the critical role of parity dynamics in the cooling process and present a simple theory that predicts the achievable steady-state atomic energies. 相似文献
78.
79.
Sushobhan Chowdhury Tanmoy Chanda Suvajit Koley B. Janaki Ramulu Keshav Raghuvanshi Maya Shankar Singh 《Tetrahedron》2014
β-Allyl-β-hydroxy dithioesters have been employed in the synthesis of hitherto unreported and synthetically demanding 2H-thiopyrans via regioselective intramolecular annulation strategy. Lewis acid BF3·Et2O efficiently mediates the regioselective dehydration followed by intramolecular thioannulation at room temperature. The attractive features of this protocol include mild conditions, high atom-economy and excellent yields with the elimination of water as the only by-product. 相似文献
80.
Differential pair distribution function analysis was applied to resolve, with crystallographic detail, the structure of catalytic sites on the surface of nanoscale γ-Al(2)O(3). The structure was determined for a basic probe molecule, monomethylamine (MMA), bound at the minority Lewis acid sites. These active sites were found to be five-coordinate, forming distorted octahedra upon MMA binding. This approach could be applied to study the interaction of molecules at surfaces in dye-sensitized solar cells, nanoparticles, sensors, materials for waste remediation, and catalysts. 相似文献