全文获取类型
收费全文 | 394篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 274篇 |
晶体学 | 28篇 |
力学 | 11篇 |
数学 | 43篇 |
物理学 | 45篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 29篇 |
2010年 | 31篇 |
2009年 | 28篇 |
2008年 | 40篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 29篇 |
2004年 | 22篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 4篇 |
1991年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有401条查询结果,搜索用时 15 毫秒
51.
52.
Sterically hindered salicylaldimine functionalized imidazolium salts 2 have been prepared. The structures of the synthesized compounds were determined by spectroscopic techniques. The reaction of these salts containing arylmethyl-N chain (aryl: phenyl (2a), 2,4,6-trimethylphenyl (2b), 2,3,4,5,6-pentamethylphenyl (2c)) with Pd(OAc)2 in boiling toluene afforded Pd(II) complexes 3 in high yields. The X-ray structure of 1-[3-(3,5-di-tert-butyl-2-oxophenyl)propyliminato]-3-(2,4,6-trimethylbenzyl)imidazol-2-ylidenebromopalladium(II) (3b) has been determined. The Suzuki-Miyaura reaction was used to investigate their activity as catalysts either prepared in situ or from well-defined complexes. They are efficient when activated arylbromides are used as substrates. 相似文献
53.
Abdurrahman Sengul Haydar Arslan Sevgi H. Bayari Orhan Buyukgungor 《Structural chemistry》2008,19(3):467-476
The molecular and crystal structures of 1,2-bis(3,4-dimethoxyphenyl)ethane-1,2-dione (TMBZ = tetramethoxybenzil) were determined by a single-crystal X-ray diffraction, 1H NMR, and FT-IR spectroscopy. The compound TMBZ (C18H18O6, M r = 330.32) crystallized in the orthorhombic Fdd2 space group wherein: a = 39.145(4), b = 18.167(2), c = 4.3139(5) Å and β = 90°, Z = 8. The packing of the molecules in the crystal lattice is stabilized by intermolecular C–H?O contacts in the herringbone arrangement. The molecular geometry and harmonic frequencies of TMBZ in the ground state were calculated utilizing density functional (B3LYP) method with the 6-311++G(d, p)-basis set. The density functional theory optimized the geometric structure, and vibrational wave numbers of TMBZ in gas phase were compared with the experimental data. A complete assignment of the fundamentals was proposed based on the total energy distribution calculation. 相似文献
54.
Bahri Ülküseven Tülay Bal-Demirci Mehmet Akkurt erife Pnar Yaln Orhan Büyükgüngr 《Polyhedron》2008,27(18):3646-3652
The reactions of 5-R-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazone {R: H (L1); Br (L2)} with [MII(PPh3)nCl2] (M = Ni, n = 2 and M = Ru, n = 3) in a 1:1 molar ratio have given stable solid complexes corresponding to the general formula [Ni(L)(PPh3)] and [Ru(HL)2(PPh3)2]. While the 1:1 nickel complexes are formed from an ONS donor set of the thiosemicarbazone and the P atom of triphenylphosphine in a square planar structure, the 1:2 ruthenium complexes consist of a couple from each of N, S and P donor atoms in a distorted octahedral geometry. These mixed-ligand complexes have been characterized by elemental analysis, IR, UV–Vis, APCI-MS, 1H and 31P NMR spectroscopies. The structures of [Ni(L2)(PPh3)] (II) and [Ru(L1H)2(PPh3)2] (III) were determined by single crystal X-ray diffraction. 相似文献
55.
Furkan Özen Suat Tekin Kenan Koran Süleyman Sandal Ahmet Orhan Görgülü 《Research on Chemical Intermediates》2016,42(12):7793-7805
A series of 2-(2,3,4-trimethoxyphenyl)-1-(substituted-phenyl)acrylonitrile (2–9) were designed and synthesized to develop new cancer drugs. The structures of synthesized compounds 2–9 were described by using melting point, mass (MALDI-TOF-MS), FT-IR, elemental analysis, 1H, 13C, 13C-APT and 2D NMR spectroscopy. The in vitro anticancer activities of 2–9 against human breast cancer (MCF-7), human prostate cancer (PC-3) and human ovarian cancer cells (A2780) were investigated by [3-(4,5-dimethylthiazol)-2-yl]-2,5-diphenyl-2H-tetrazolium bromide] (MTT) assay method. Additionally, the LogIC50 values of these compounds on A2780, MCF-7 and PC-3 cell lines were calculated by using inhibition % values by the GraphPad Prism 6 program on a computer. The results indicated that these compounds have high anticancer activity against MCF-7, PC-3 and A2780 cell lines (especially A2780 cell lines, p < 0.05). 相似文献
56.
Okan Zafer Yeşilel Dr. Hümeyra Paşaoğlu Kamber Akdağ Orhan Büyükgüngör 《无机化学与普通化学杂志》2007,633(10):1731-1734
The new orotate complex of cadmium(II) with quinoxaline, mer‐[Cd(HOr)(H2O)3(QX)]·2H2O, was synthesized and characterized by elemental analysis, FT–IR spectroscopy, thermal analysis and single crystal X–ray diffraction techniques. The complex crystallizes in the triclinic system, space group . The Cd2+ ion exhibits a distorted octahedral coordination by one bidentate orotate, one monodentate quinoxaline and three aqua ligands. The uncoordinated water molecules link the orotate, quinoxaline and aqua ligands via O–H···O, O–H···N hydrogen bonds. Thus, an extensive network of hydrogen bonds stabilizes the crystal structure and form an infinitive three dimensional lattice. The decomposition reaction takes place in the temperature range 20–700 °C in the static air atmosphere. 相似文献
57.
Günseli Turgut Metin Zora Mustafa Odabaolu Cem Cüneyt Ersanl Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(5):o321-o323
The crystal structure of the title compound, C2H10N2O2+·2Cl−, is built up from one 2‐hydroxyethylhydrazinium(2+) cation and two Cl− anions. The molecular structure is stabilized by O—H⋯Cl and N—H⋯Cl hydrogen bonds. The crystal structure is stabilized by one N—H⋯O and three N—H⋯Cl interactions, and the three‐dimensional network of hydrogen bonds stabilizes the crystal packing. All five hydrazinium H atoms are involved in hydrogen bonds to Cl− anions. The Cl⋯H contact distances range from 2.122 (15) to 2.809 (14) Å. 相似文献
58.
Ahmet Karadag Ahmet Bulut Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(8):m402-m404
The crystal structure of the title compound, [Ni(NCS)2(C4H12N2O)2], has two crystallographically independent half‐molecules in the asymmetric unit, with each Ni atom residing on a centre of symmetry. The two molecules exhibit similar coordination geometry but display differences with regard to other structural features. Each NiII centre is octahedrally coordinated by two mutually trans chelating hydroxyethylethylenediamine ligands and two mutually trans isothiocyanate ions. The two independent molecules form chains through different types of non‐covalent interactions. In the case of one of the molecules, only NCS and free OH groups participate in hydrogen bonding, while in the chain based on the second molecule, the NCS, NH, NH2 and free OH groups are involved in intermolecular hydrogen bonding. The two chains interact with one another through hydrogen bonding, forming planar sheets. The third packing direction is mediated only by van der Waals interactions. 相似文献
59.
Ahmet Bulut brahim Uar Okan Zafer Yeilel Hasan budak Halis
lmez Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(10):m526-m528
The title mononuclear [Cu(sq)(phen)2]·3H2O complex [sq is squarate (C4O4) and phen is 1,10‐phenanthroline (C12H8N2)] has been synthesized and the structure consists of a neutral mononuclear [Cu(sq)(phen)2] unit and three solvate water molecules. The CuII ion has distorted square‐pyramidal coordination geometry, comprised of one carboxylate O atom from a monodentate squarate ligand and four N atoms from two chelating phen ligands. An extensive three‐dimensional network of OW—H⋯O/OW hydrogen bonds, face‐to‐face π–π interactions between the 1,10‐phenanthroline aromatic rings and a weak π–ring interaction are responsible for crystal stabilization. 相似文献
60.
Fatma Tezcan Hümeyra Paaolu Okan Z. Yeilel Halis
lmez Hasan Ibudak Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(7):m335-m337
In the crystal structure of the title compound, [Ni(C6H6N2O)2(H2O)2](C7H4NO3S)2·4H2O or [Ni(pia)2(H2O)2](sac)2·4H2O (pia is picolinamide or pyridine‐2‐carboxamide, and sac is the saccharinate anion), the Ni2+ cation, located on a centre of symmetry, is coordinated by two symmetry‐related aqua ligands together with a pair of symmetry‐related bidentate pia molecules and exhibits a distorted octahedral environment. The unique unligated sac anion in the asymmetric unit resides on a general position and has a single negative charge. The coordinated water molecules link the sac ions to the metal complex via O—H⋯O hydrogen bonds. In addition, the sac ions are linked to the metal complex via intermolecular π–π interactions between the benzene ring of the sac ion and the pyridine ring of a pia ligand. Each uncoordinated water molecule is hydrogen bonded to sac moieties through O—H⋯O and O—H⋯N hydrogen bonds. 相似文献