全文获取类型
收费全文 | 302篇 |
免费 | 18篇 |
专业分类
化学 | 183篇 |
数学 | 27篇 |
物理学 | 110篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 11篇 |
2013年 | 29篇 |
2012年 | 32篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 11篇 |
2008年 | 26篇 |
2007年 | 19篇 |
2006年 | 7篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有320条查询结果,搜索用时 31 毫秒
141.
Some S Kim Y Hwang E Yoo H Lee H 《Chemical communications (Cambridge, England)》2012,48(62):7732-7734
For the first time, stable aqueous dispersions of graphene sheets can be prepared via exfoliation/in situ reduction of graphene oxide in the presence of binol salt, a stabilizing surfactant that can be completely removed without affecting the properties of graphene sheets. 相似文献
142.
Rahul Ghosh Surajit Chattopadhyay Ujjal Debnath 《International Journal of Theoretical Physics》2012,51(2):589-603
This work is motivated by the work of Kim et al. (Mod. Phys. Lett. A 23:3049, 2008), which considered the equation of state parameter for the new agegraphic dark energy based on generalized uncertainty principle
coexisting with dark matter without interaction. In this work, we have considered the same dark energy interacting with dark
matter in emergent, intermediate and logamediate scenarios of the universe. Also, we have investigated the statefinder, kerk and lerk parameters in all three scenarios under
this interaction. The energy density and pressure for the new agegraphic dark energy based on generalized uncertainty principle
have been calculated and their behaviors have been investigated. The evolution of the equation of state parameter has been
analyzed in the interacting and non-interacting situations in all the three scenarios. The graphical analysis shows that the
dark energy behaves like quintessence era for logamediate expansion and phantom era for emergent and intermediate expansions
of the universe. 相似文献
143.
Ujjal Debnath Surajit Chattopadhyay Ibrar Hussain Mubasher Jamil Ratbay Myrzakulov 《The European Physical Journal C - Particles and Fields》2012,72(2):1875
In this work, we have considered the power-law correction of entropy on the horizon. If the flat FRW Universe is filled with
the n components fluid with interactions, the GSL of thermodynamics for apparent and event horizons have been investigated for
equilibrium and non-equilibrium cases. If we consider a small perturbation around the de Sitter spacetime, the general conditions
of the validity of GSL have been found. Also if a phantom dominated Universe has a pole-like type scale factor, the validity
of GSL has also been analyzed. Further we have obtained constraints on the power-law parameter α in the phantom and quintessence dominated regimes. Finally we obtain conditions under which GSL breaks down in a cosmological
background. 相似文献
144.
Jana S Berger RJ Fröhlich R Mitzel NW 《Chemical communications (Cambridge, England)》2006,(38):3993-3995
The first organometallic clusters of mixed hydrazide/hydroxylamide clusters of zinc, [Zn(MeZn)(4)(HNNMe(2))(2)(ONEt(2))(4)] and {Zn(EtZn)(4)[HNN(CH(2))(5)](2)(ONEt(2))(4)} were synthesized in one-pot synthesis protocols from dialkylzinc solutions, substituted hydrazines and N,N-diethylhydroxylamine; competing for the Zn atoms, the different binding properties of hydrazide and hydroxylamide ligands in these heteroleptic clusters are discussed. 相似文献
145.
Surajit Chattopadhyay Ujjal Debnath 《International Journal of Theoretical Physics》2010,49(7):1465-1480
The present work considers interaction between DBI-essence and other candidates of dark energies like modified Chaplygin gas,
hessence, tachyonic field, and new agegraphic dark energy. The potentials of the fields have been reconstructed under interaction
and their evolutions have been viewed against cosmic time t and scalar field φ. Equation of state parameters have also been obtained. The nature of potentials and the equation of state parameters of the
dark energies have been found graphically in presence of interaction (both small and large interaction). 相似文献
146.
We report on the growth of horizontal and straight Si nanowires (NWs) on Si substrate using sputter deposition of the Si layer followed by thermal annealing at 1000 °C and above. The growth of horizontal NWs was achieved without the use of any metal catalyst. Uniform cylindrical shaped Si NWs with a diameter in the range of 50–60 nm and a length of up to 8 μm were synthesized. The as-synthesized Si NWs have a Si core covered with a thin amorphous native oxide layer, as revealed by high resolution transmission electron microscopy. The aspect ratio of these Si NWs is in the range of 100–160. Micro-Raman studies on the NWs reveal a tensile strain on the Si NW core due to presence of a thin oxide layer. From the Raman shift, we calculate a strain of 1.0% for the catalyst free Si NW. FTIR analysis indicates the presence of interstitial oxygen atoms in the Si NWs, as expected from oxidation of Si NWs. For comparison, metal catalyst (Au) assisted Si NWs have also been grown on Si(100) substrate by a similar process. These NWs have a similar diameter and a marginally higher aspect ratio. A model for the growth mechanism of horizontal NWs is presented. This represents one of the first examples of direct horizontal growth of straight Si NWs on commonly used Si substrates suitable for nanoelectronic device fabrication. 相似文献
147.
148.
Hans Raj Bhat Anup Masih Anshul Shakya Surajit Kumar Ghosh Udaya Pratap Singh 《Journal of heterocyclic chemistry》2020,57(1):390-399
A series of 4-aminoquinoline 1,3,5-triazine derivatives were synthesized and evaluated for anticancer activity against cancer cell lines HeLa, MCF-7, HL-60, HepG2 where these derivatives exert significant anticancer activity. The molecules found nontoxic against MCF-12A. The molecules also showed potent inhibition of EGFR-TK as compared to eroltinib in enzyme-based assay. The newly synthesized derivatives were screened for their in vitro antibacterial and antifungal activity against Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Proteus vulgaris, Escherichia coli, Pseudomonas aeruginosa and Candida albicans, Aspergillus niger, Aspergillus fumigatus using cefixime and fluconazole as standard. Antibacterial screening results suggest that compound 7c showed potent activity against S. aureus, P. aeruginosa, and P. vulgaris. In antifungal screening, compound 7b showed significant activity against A. niger, A. fumigatus and moderate activity against C. albicans. 相似文献
149.
Ultrafast FRET to Study Spontaneous Micelle‐to‐Vesicle Transitions in an Aqueous Mixed Surface‐Active Ionic‐Liquid System
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sarthak Mandal Jagannath Kuchlyan Debasis Banik Surajit Ghosh Chiranjib Banerjee Vijaykant Khorwal Nilmoni Sarkar 《Chemphyschem》2014,15(16):3544-3553
The spontaneous micelle‐to‐vesicle transition in an aqueous mixture of two surface‐active ionic liquids (SAILs), namely, 1‐butyl‐3‐methylimidazolium n‐octylsulfate ([C4mim][C8SO4]) and 1‐dodecyl‐3‐methylimidazoium chloride ([C12mim]Cl) is described. In addition to detailed structural characterization obtained by using dynamic light scattering, transmission electron microscopy (TEM), and cryogenic TEM techniques, ultrafast fluorescence resonance energy transfer (FRET) from coumarin 153 (C153) as a donor (D) to rhodamine 6G (R6G) as an acceptor (A) is also used to study micelle–vesicle transitions in the present system. Structural transitions of SAIL micelles ([C4mim][C8SO4] or [C12mim]Cl micelles) to mixed SAIL vesicles resulted in significantly increased D –A distances, and therefore, increased timescale of FRET. In [C4mim][C8SO4] micelles, FRET between C153 and R6G occurs on an ultrafast timescale of 3.3 ps, which corresponds to a D –A distance of about 15 Å. As [C4mim][C8SO4] micelles are transformed into mixed micelles upon the addition of a 0.25 molar fraction of [C12mim]Cl, the timescale of FRET increases to 300 ps, which suggests an increase in the D –A distance to 31 Å. At a 0.5 molar fraction of [C12mim]Cl, unilamellar vesicles are formed in which FRET occurs on multiple timescales of about 250 and 2100 ps, which correspond to D –A distances of 33 and 47 Å. Although in micelles and mixed micelles the obtained D –A distances are well correlated with their radius, in vesicles the obtained D –A distance is within the range of the bilayer thickness. 相似文献
150.