全文获取类型
收费全文 | 183篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 101篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 25篇 |
物理学 | 62篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 11篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 11篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有196条查询结果,搜索用时 484 毫秒
61.
Dkhissi A Estève A Jeloaica L Estève D Rouhani MD 《Journal of the American Chemical Society》2005,127(27):9776-9780
Quantum chemical calculations have been carried out on the grafting of chain organosilane compounds on SiO(2)-hydroxylated solid surfaces. It is shown that a single molecule interacting with the surface lies flat to it, inhibiting further homogeneous film growth. This adsorption exhibits two molecule/surface interactions: a covalent bond on one side of the molecule and a hydrogen bond on the other side. We then investigate the possible preorganization of the molecules before grafting due to the presence of water molecules either in the gas/liquid phase or near the surface. This gives rise to the formation of dimerized chains. We then demonstrate that this preorganization process prevents subsequent lying flat of the molecules to the substrate after grafting. Energetics and associated configurations of the overall deposition process are discussed in detail and provide new insights on the understanding of the formation of self-assembled homogeneous organic films on microelectronics-type substrates. 相似文献
62.
Zahida Shirin Brian S. Hammes Chris R. Warthen Carl J. Carrano 《Journal of chemical crystallography》2003,33(5-6):431-436
Reaction of the Zn, Cd, or Co nitrate salts with the deprotonated ligand (2-hydroxy-3-t-butyl-methylphenyl)bis(3,5-dimethylpyrazolyl)methane (L1O–) in methanol produced the following complexes: [(L1OH)Zn(NO3)2] in two isomorphs, a = 40.983(8) Å, b = 9.571(2) Å, c = 15.667(8) Å, = 90, = 106.38(1), = 90, C2/c, and a = 13.027(3) Å, b = 14.781(4) Å, c = 16.107(3) Å, = 90, = 105.30(1), = 90, P21/n; [(L1OH)Cd(pz)(NO3)2] a = 14.7476(2) Å, b = 13.5411(2) Å, c = 16.7223(2) Å, = 90, = 110.3840(10), = 90, P21/c; and [(L1O)Co(pz)(NO3)] a = 11.4240(2) Å, b = 13.4498(2) Å, c = 13.8056(2) Å, = 105.2080(10), = 105.8130(10), = 112.7470(10), P
. The Zn adopts a pseudotetrahedral four-coordinate geometry where the potentially tridentate ligand is actually bidentate with a protonated and uncoordinated phenoxy arm. The Co complex is pseudooctahedral six-coordinate where the phenoxy arm is deprotonated and coordinated. Finally the Cd complex is seven-coordinate but the metal is not coordinated through the phenoxy group that is again protonated. 相似文献
63.
64.
B. Djafari Rouhani Y. Pennec E. H. El Boudouti J. O. Vasseur Y. El Hassouani C. Li A. Akjouj D. Bria 《Applied Physics A: Materials Science & Processing》2011,103(3):735-739
We discuss the simultaneous existence of phononic and photonic band gaps in two types of phononic crystals slabs, namely periodic
arrays of nanoholes in a Si membrane and of Si nanodots on a SiO2 membrane. In the former geometry, we investigate in detail both the boron nitride lattice and the square lattice with two
atoms per unit cell (these include the square, triangular and honeycomb lattices as particular cases). In the latter geometry,
some preliminary results are reported for a square lattice. 相似文献
65.
Mina Saeedi Shirin Ansari Mohammad Mahdavi Reyhaneh Sabourian Tahmineh Akbarzadeh Alireza Foroumadi 《合成通讯》2013,43(20):2311-2318
A novel series of 1,2,3-triazole-dihydro[3,2-c]chromenone derivatives were synthesized through an efficient three-step reaction starting from 4-hydroxybenzaldehyde. All the newly synthesized compounds were characterized by infrared and NMR spectroscopy as well as elemental analysis and evaluated for their acetylcholinesterase inhibitory activity. 相似文献
66.
Ali Ramazani Behnaz Abdian Fatemeh Zeinali Nasrabadi Morteza Rouhani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):642-648
Abstract Reaction of N-isocyaniminotriphenylphosphorane with biacetyl in the presence of (E)-cinnamic acids proceeds smoothly at room temperature and under neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and straightforward under mild conditions and no side reactions are observed. 相似文献
67.
68.
Yoffi Segall Ezra Shirin Itshak Granoth 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):243-254
Abstract Derivatives of the novel dibenzo[b,f]phosphepin system are prepared from 10,11-dihydro-5-phenyl-5H-bibenzo[b,f]phosphepin 5-oxide (2). New members in the 10,11-dihydro-5H-dibenzo[b,f]phosphepin series, including phosphorus analogues (7, 10) of the andidepressant drug imipramine (30), are also reported. Products of nucleophilic substitution at tetrahedral phosphorus in 2 appear to be determined by the relative apicophilicity of the nucleophile. Conformational analysis based on 1H NMR data suggests folded (“butterfly”) conformation for the tricyclic compounds. The twisted boat conformation of the central ring in the 10,11-dihydro compounds bears a pseudo-equatorial P[dbnd]O oxygen or a P[dbnd]S sulfur, in solution. Symmetric AA‘BB’ spin systems are found in 4,5 and 7, and their solution conformations appear to be similar to those of analogous 10,11-dihydrodibenzo[b,f]azepine derivatives. The interaction of some compounds with NMR shift reagents and their mass spectral fragmentations are discussed. 相似文献
69.
Lobat Tayebi Masoud Mozafari Rita El‐khouri Parvaneh Rouhani Daryoosh Vashaee 《Photochemistry and photobiology》2014,90(3):517-521
Light induced cis/trans isomerization in the family of merocyanine (MC) dyes offers a recyclable proton pumping ability which can potentially be used in hybrid bio‐electronic devices. In this article, a hexadecyl MC dye is embedded in lipid molecules to make a macromolecular configuration of a lipid/hexadecyl MC membrane. Lipid molecules play a critical role in stabilizing the dye in a membrane structure for practical use in energy devices. In this study, we first examined the proton pumping characteristic of the lipid/hexadecyl MC membrane in a conventional photoelectrochemical cell. Next, a major modification in the cell was introduced by eliminating I2/I‐electrolyte which resulted in a two‐fold increase in the open circuit voltage compared with that of the conventional cell. In addition, the charging time in the new cell was reduced approximately four orders of magnitude. This research demonstrated that the newly designed lipid‐ MC cell can act as a promising bioelectronic device based on the green energy of photoinduced MC dye proton pumping. 相似文献
70.
We propose an analytical model for the statistical mechanics of shuffled two-dimensional foams with moderate bubble size polydispersity. It predicts without any adjustable parameters the correlations between the number of sides n of the bubbles (topology) and their areas A (geometry) observed in experiments and numerical simulations of shuffled foams. Detailed statistics show that in shuffled cellular patterns n correlates better with √A (as claimed by Desch and Feltham) than with A (as claimed by Lewis and widely assumed in the literature). At the level of the whole foam, standard deviations Δn and ΔA are in proportion. Possible applications include correlations of the detailed distributions of n and A, three-dimensional foams, and biological tissues. 相似文献