全文获取类型
收费全文 | 143篇 |
免费 | 4篇 |
国内免费 | 7篇 |
专业分类
化学 | 109篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 20篇 |
物理学 | 16篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2018年 | 9篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 5篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 5篇 |
2007年 | 10篇 |
2006年 | 4篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有154条查询结果,搜索用时 15 毫秒
71.
NH4Fe(SO4)2 was found to be a mild and effective catalyst for the selective synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles under solvent‐free conditions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
72.
Ardeshir Khazaei Ahmad Reza Moosavi‐Zare Fatemeh Gholami Vahid Khakyzadeh 《应用有机金属化学》2016,30(8):691-694
Magnetic core–shell titanium dioxide nanoparticles (Fe3O4@SiO2@TiO2) were applied for the efficient preparation of 1,2,4,5‐tetrasubstituted imidazole derivatives by the one‐pot multi‐component condensation of benzil with aldehydes, primary amines and ammonium acetate under solvent‐free conditions. The catalyst was synthesized and studied using several techniques including X‐ray diffraction, transmission electron microscopy, field‐emission scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
73.
Knoevenagel‐Michael‐cyclocondensation Tandem Reaction of Malononitrile,Various Aldehydes and Dimedone Catalyzed by Sulfonic Acid Functionalized Pyridinium Chloride as a New Ionic Liquid and Catalyst 下载免费PDF全文
Mohammad Ali Zolfigol Ardeshir Khazaei Ahmad Reza Moosavi‐Zare Javad Afsar Vahid Khakyzadeh Omid Khaledian 《中国化学会会志》2015,62(5):398-403
New ionic liquid sulfonic acid functionalized pyridinium chloride [Pyridine–SO3H]Cl was used for the synthesis of tetrahydrobenzo[b]pyran derivatives by the one‐pot three component condensation reaction of various aldehydes, dimedone and malononitrile at 95 ºC under solvent‐free conditions. 相似文献
74.
Chemoselective oxidation of thiols to their corresponding disulfides with N‐bromosaccharin in a very short time and with high yields in dichloromathane under microwave irradiation conditions are described. 相似文献
75.
Ardeshir Khazaei Amin Rostami 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):555-557
ABSTRACT An efficient method for oxidation of thiol to their corresponding disulfides in high yields with N, N′-Dibromo-N,N′–1,2-ethanediyl bis (p-toluensulphonamide) in dichloromethane at room temperature is described. 相似文献
76.
We prove that Basic Arithmetic, BA, has the de Jongh property, i.e., for any propositional formula A(p 1,..., p n ) built up of atoms p 1,..., p n , BPC \({\vdash}\) A(p 1,..., p n ) if and only if for all arithmetical sentences B 1,..., B n , BA \({\vdash}\) A(B 1,..., B n ). The technique used in our proof can easily be applied to some known extensions of BA. 相似文献
77.
Structurally diverse aromatic aldehydes were thioacetalated in a clean and efficient reaction with ethane‐1, 2‐dithiol and thiophenol based on the use of I2 generated in situ from Fe(NO3)3.9H2O/NaI. The reaction occurs in good to high yield in dichloromethane at room temperature and the use of toxic and corrosive molecular iodine is avoided. 相似文献
78.
Z. Aghajani H. Aghabozorg E. Sadr-Khanlou A. Shokrollahi S. Derki M. Shamsipur 《Journal of the Iranian Chemical Society》2009,6(2):373-385
The Cr(III) and Ca(II) complexes (dmpH)[Cr(pydc)2]?H2O (1) and [Ca2(pydc)2(H2O)6].2pydcH2 (2) were synthesized by reaction of 2,9-dimethyl-1,10-phenanthroline (dmp) and pyridine-2,6-dicarboxylic acid (pydcH2) with Cr(NO3)3 and Ca(NO3)2, respectively, and characterized using IR spectroscopy, single crystal X-ray diffraction method and solution studies. The space group and crystal system of these two compounds are P2 1/c and monoclinic. The crystal dimensions are a = 9.785(3) Å, b = 25.671(4) Å, c = 9.3402(16) Å, β = 90.790(17)° for (1) and a = 9.1319(4) Å, b = 14.8430(8) Å, c = 12.2449(7) Å, β = 98.227(5)° for (2). In complex (1), a water molecule presents in the crystal packing, linking the anionic and cationic fragments together by hydrogen bonding and thus increases the stabilization of crystal lattices. In complex (2), the coordinated water molecules relate each dimer to adjacent dimers forming infinite molecular ribbons by strong hydrogen bondings. Hydrogen bonding and ion pairing play an important role in stabilizing these crystals. The complexation reactions of pydc, dmp and pydc+dmp with Cr3+ and Ca2+ ions in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed were evaluated. 相似文献
79.
H. Aghabozorg E. Sadr-khanlou A. Shokrollahi M. Ghaedi M. Shamsipur 《Journal of the Iranian Chemical Society》2009,6(1):55-70
The homonuclear water-soluble and air stable compounds (dmpH) (H5O2) au][M(pydc)2].0.5H2O (M = Ni(II) (1), Cu(II) (2), Zn(II) (3); pydcH2 = pyridine-2,6-dicarboxylic acid, dipicolinic acid, dmp = 2,9-dimethyl-1,10-phenanthroline) have been prepared by self-assembly synthesis in aqueous solution at room temperature, and characterized by IR, 1H NMR, 13C NMR, elemental analysis and X-ray diffraction single crystal analyses for 1, 2 and 3. The complexes 1–3 represent the isostructural features. Extensive hydrogen bonding interactions involving all aqua ligands, dipicolinate oxygens and lattice water molecules further stabilize the complex units by linking them to form three dimensional polymeric networks. The stoichiometry and stability of the all three complexes in aqueous solution were investigated by potentiometric pH titration. 相似文献
80.
H. Aghabozorg S. Daneshvar E. Motyeian F. Manteghi R. Khadivi M. Ghadermazi A. Shokrollahi M. Ghaedi S. Derki M. Shamsipur 《Journal of the Iranian Chemical Society》2009,6(3):620-637
Novel metal organic frameworks including {(pipzH2)[Mn(py-2,3-dc)2]·7.75H2O}n, 1, {(pipzH2)[Zn(py-2,3-dc)2]·4H2O}n, 2, [Cd(py-2,3-dc)(H2O)3]n, 3 and {(pipzH2)[Hg4Cl10]}n, 4, in which pipz is piperazine and py-2,3-dcH2 is pyridine-2,3-dicarboxylic acid were synthesized applying a proton transfer ion pair i.e. (pipzH2)(py-2,3-dcH)2 and corresponding metallic salts and studied by IR, 1H NMR, 13C NMR spectroscopy and single crystal X-ray diffractometry. The space group of compounds 1 and 4 are P21/c and C2/c of monoclinic system, respectively. The crystal dimensions are a = 20.108(2) Å, b = 19.910(2) Å, c = 12.997(1) Å, β = 94.354(2)° for 1 and a = 15.940(1) Å, b = 11.2690(9) Å, c = 11.1307(9) Å, β = 90.685(2)° for 4. The crystal structures of 2 and 3 have been reported previously. However, their solution studies are discussed here. The compounds had all polymeric structures. Although ZnII, CdII and HgII were elements of the same group, their behavior against the ion pair was essentially different. Various supramolecular interactions mainly hydrogen bonds of the type O-H?O, N-H?O, C-H?O, N-H…Cl and C-H?Cl were observed in the structures. There was an unusual and huge water cluster in the structure of compound 1. The solution states of compounds 1–4 were studied and reported. The protonation constants of pipz and py-2,3-dc, the py-2,3-dc/pipz proton transfer equilibrium constants and stoichiometry and stability of the system with Mn2+, Zn2+, Cd2+ and Hg2+ ions in aqueous solution were investigated by potentiometric pH titrations. 相似文献