全文获取类型
收费全文 | 572篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 317篇 |
晶体学 | 7篇 |
力学 | 16篇 |
数学 | 44篇 |
物理学 | 197篇 |
出版年
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 22篇 |
2012年 | 45篇 |
2011年 | 52篇 |
2010年 | 20篇 |
2009年 | 35篇 |
2008年 | 46篇 |
2007年 | 28篇 |
2006年 | 37篇 |
2005年 | 33篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有581条查询结果,搜索用时 15 毫秒
571.
S. Chattopadhyay S.K. Neogi A. Sarkar M.D. Mukadam S.M. Yusuf A. Banerjee S. Bandyopadhyay 《Journal of magnetism and magnetic materials》2011,323(3-4):363-368
Single phase Mn doped (2 at%) ZnO samples have been synthesized by the solid-state reaction technique. Before the final sintering at 500 °C, the mixed powders have been milled for different milling periods (6, 24, 48 and 96 h). The grain sizes of the samples are very close to each other (~32±4 nm). However, the defective state of the samples is different from each other as manifested from the variation of magnetic properties and electrical resistivity with milling time. All the samples have been found to be ferromagnetic with clear hysteresis loops at room temperature. The maximum value for saturation magnetization (0.11 μB/Mn atom) was achieved for 96 h milled sample. Electrical resistivity has been found to increase with increase in milling time. The most resistive sample bears the largest saturation magnetization. Variation of average positron lifetime with milling time bears a close similarity with that of the saturation magnetization. This indicates the key role played by open volume vacancy defects, presumably zinc vacancies near grain surfaces, in inducing ferromagnetic order in Mn doped ZnO. To attain optimum defect configuration favorable for ferromagnetism in this kind of samples proper choice of milling period and annealing conditions is required. 相似文献
572.
Chemical investigation of the gum resin of Ferula assa-foetida L. resulted in the isolation of a new sesquiterpenoid coumarin, 7-(((E)-5-((1S,3S,6S)-3,6-dihydroxy-2,2,6-trimethylcyclohexyl)-3-methylpent-2-en-1-yl)oxy)-2H-chromen-2-one (asimafoetidnol), together with several other known compounds. The structure of asimafoetidnol was established on the basis of spectroscopic analyses. Geometry optimization of the compound has been carried out using a DFT/B3LYP/3-21G* method. 相似文献
573.
Jadhav SV Bandyopadhyay A Benke SN Mali SM Gopi HN 《Organic & biomolecular chemistry》2011,9(11):4182-4187
A facile, efficient and racemization-free method for the synthesis of N-protected β-amino alcohols and peptaibols using N-hydroxysuccinimide active esters is described. Using this method, dipeptide, tripeptide and pentapeptide alcohols were isolated in high yields. The conformations in crystals of β-amino alcohol, dipeptide and tripeptide alcohols were analysed, with a well-defined type III β-turn being observed in the tripeptide alcohol crystals. This method is found to be compatible with Fmoc-, Boc- and other side-chain protecting groups. 相似文献
574.
Cyclophostin, a structurally unique and potent naturally occurring acetyl cholinesterase (AChE) inhibitor, and its unnatural diastereomer were prepared in 6 steps and 15% overall yield from hydroxymethyl butyrolactone. The unnatural diastereomer of cyclophostin was converted into cyclipostin P, a potent naturally occurring hormone sensitive lipase (HSL) inhibitor, using a one pot dealkylation-alkylation process. The inhibition [IC(50)] of human AChE by cyclophostin and its diastereomer are reported, as well as constituent binding (K(I)) and reactivity (k(2)) constants. 相似文献
575.
Premamoy Ghosh Dilip Kumar Chowdhury Arup Rat Bandyopadhyay 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5-6):549-555
Preliminary studies on the suitability of some organic acids and amines, separately and in combination with each other, as photo-initiators for the polymerization of methyl methacrylate were made. Combinations of maleic acid or phthalic acid with any of the tertiary amines–triethyl amine, demethyl aniline, and diethylaniline-proved to be interesting photoinitiator systems in view of the fact that the initiator components in each combination were ineffective as initiators when used separately. The rate of photopolymerization in each of the above acid-amine combination system was much enhanced and the respective inhibition period largely reduced when benzophenone was used as the photoinitiator. Aliphatic diamine or polyamines such as ethylene diamine, diethylene triamine, and tri-ethylene tetramine, were ineffective as photoinitiators when used alone or in combination with maleic acid, but became effective 相似文献
576.
Bandyopadhyay D Prashar D Luk YY 《Langmuir : the ACS journal of surfaces and colloids》2011,27(10):6124-6131
This work reports the resistance to protein adsorption and bacterial biofilm formation by chiral monolayers of polyol-terminated alkanethiols surrounding micrometer-sized patterns of methyl-terminated alkanethiols on gold films. We discover that patterned surfaces surrounded by chiral polyol monolayers can distinguish different stages of biofilm formation. After inoculation on the surfaces, bacteria first reversibly attached on the chiral polyol monolayers. Over time, the bacteria detached from the polyol surfaces, and attached on the hydrophobic micropatterns to form biofilms. Interestingly, while both enantiomers of gulitol- and mannonamide-terminated monolayer resisted adsorption of proteins (bovine serum albumin, lysozyme, and fibrinogen) and confined biofilms formed on the micropatterns, the monolayers formed by the racemic mixture of either pair of enantiomers exhibited stronger antifouling chemistry against both protein adsorption and biofilm formation than monolayers formed by one enantiomer alone. These results reveal the different chemistries that separate the different stages of biofilm formation, and the stereochemical influence on resisting biofoulings at a molecular-level. 相似文献
577.
578.
A new mechanism is proposed to explain the origin of negative differential resistance (NDR) in a strongly coupled single molecule-metal junction. A first-principles quantum transport calculation in a Fe-terpyridine linker molecule sandwiched between a pair of gold electrodes is presented. Upon increasing the applied bias, it is found that a new phase in the broken symmetry wave function of the molecule emerges from the mixing of occupied and unoccupied molecular orbitals. As a consequence, a nonlinear change in the coupling between the molecule and the lead is evolved resulting in NDR. This model can be used to explain NDR in other classes of metal-molecule junction devices. 相似文献
579.
Tanihata I Alcorta M Bandyopadhyay D Bieri R Buchmann L Davids B Galinski N Howell D Mills W Mythili S Openshaw R Padilla-Rodal E Ruprecht G Sheffer G Shotter AC Trinczek M Walden P Savajols H Roger T Caamano M Mittig W Roussel-Chomaz P Kanungo R Gallant A Notani M Savard G Thompson IJ 《Physical review letters》2008,100(19):192502
The p((11)Li, (9)Li)t reaction has been studied for the first time at an incident energy of 3A MeV at the new ISAC-2 facility at TRIUMF. An active target detector MAYA, built at GANIL, was used for the measurement. The differential cross sections have been determined for transitions to the (9)Li ground and first excited states in a wide range of scattering angles. Multistep transfer calculations using different (11)Li model wave functions show that wave functions with strong correlations between the halo neutrons are the most successful in reproducing the observation. 相似文献
580.
García Saiz E Gregori G Khattak FY Kohanoff J Sahoo S Naz GS Bandyopadhyay S Notley M Weber RL Riley D 《Physical review letters》2008,101(7):075003
We have investigated the angular variation in elastic x-ray scattering from a dense, laser-shock-compressed aluminum foil. A comparison of the experiment with simulations using an embedded atom potential in a molecular dynamics simulation shows a significantly better agreement than simulations based on an unscreened one-component plasma model. These data illustrate, experimentally, the importance of screening for the dense plasma static structure factor. 相似文献