全文获取类型
收费全文 | 850篇 |
免费 | 45篇 |
国内免费 | 109篇 |
专业分类
化学 | 310篇 |
晶体学 | 11篇 |
力学 | 285篇 |
综合类 | 41篇 |
数学 | 139篇 |
物理学 | 218篇 |
出版年
2024年 | 5篇 |
2023年 | 16篇 |
2022年 | 23篇 |
2021年 | 18篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 19篇 |
2014年 | 29篇 |
2013年 | 45篇 |
2012年 | 38篇 |
2011年 | 54篇 |
2010年 | 39篇 |
2009年 | 53篇 |
2008年 | 50篇 |
2007年 | 66篇 |
2006年 | 57篇 |
2005年 | 51篇 |
2004年 | 48篇 |
2003年 | 37篇 |
2002年 | 38篇 |
2001年 | 27篇 |
2000年 | 24篇 |
1999年 | 16篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 15篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1004条查询结果,搜索用时 9 毫秒
51.
52.
1 INTRODUCTION The bimetallic nanoclusters are of standing inte- rest since they can exhibit catalytic, electronic and optical properties distinct from those of corre- sponding pure nanoclusters[1~4]. Palladium and pla- tinum, well known for their catalytic properties, are often used as the catalyst in different fuel cells[5~8]. Several experimental results illustrate that for the oxygen reduction reaction (ORR), which is one of the primary reactions taking place in many fuel cells and… 相似文献
53.
Four new copper (II)‐manganese (II) heterobinuclear complexes bridged byN, N'‐bis[2‐(dimethylamino)ethyl)]oxamido dianion (dmoxæ) and end‐capped with 1, 10‐phenanthroline (phen), 5‐methyl‐1, 10‐phenanthroline (Mephen), diaminoethane (en) or 1,3‐di‐aminopropane (pn). respectively, namely, [Cu(dmoxae)MnL2] (CIO4)2 (L=phen, Mephen, en, pn), have been synthesized and characterized by elemental analyses, IR, electronic spectral studies, and molar conductivity measurements. The electronic reflectance spectrum indicates the presence of spin exchange‐coupling interaction between bridged copper(II) and manganese (II) ions. The cryomagnetic measurements (4.2‐300 K) of [Cu(dmoxae)Mn(phen)2](CIO4)2 (1) and [Cu(dmoxae)Mn(Mephen)2](CIO4)2(2) complexes demonstrated an antiferromagnetic interaction between the adjacent manganese(II) and copper (II) ions through the oxamido‐bridge within each molecule. On the basis of spin Hamiltonian, H= ‐ 2JS1. S2. the magnetic analysis was carried out for the two complexes and the spin‐coupling constant (J) was evaluated as ?35.9 cm?1 for 1 and ‐ 32.6 cm?1 for 2. The influence of methyl substitutions in the amine groups of the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed. 相似文献
54.
Yu. V. Mironov S. F. Solodovnikov V. E. Fedorov Yu. V. Gatilov 《Journal of Structural Chemistry》2004,45(5):874-878
The reaction of a water solution of K4Re6Te8(CN)6 with a solution of Mn(NO3)2 in 0.02M hydrochloric acid in the presence of DMF gave crystals of a cluster rhenium complex [{ Mn(H2O)2(DMF)}2Re6Te8(CN)6]·2H2O. The structure of the compound was determined by single crystal X-ray diffraction (a = 12.6679(9) Å, b = 17.4524(12) Å, c = 9.7882(6) Å, β = 105.570(6)°, V = 2084.6(3) Å3, Z = 2, space group P21/n, R = 0. 0389). In the complex, the [Re6Te8(CN)6]4− cluster anions are linked to Mn2+ cations by the cyanide bridges, the manganese cations being additionally coordinated by the DMF molecule and two water molecules. The neighboring clusters are joined by Re-C-N-Mn bridges into a three-dimensional framework possessing cavities filled with doubly disordered water molecules.Original Russian Text Copyright © 2004 by Yu. V. Mironov, S. F. Solodovnikov, V. E. Fedorov, and Yu. V. Gatilov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 918–922, September–October, 2004. 相似文献
55.
《Arabian Journal of Chemistry》2020,13(2):4126-4133
Three biscoumarin dyes bridged by polycyclic aromatic bridges (anthracen, pyrene and dibenzo[g,p]chrysene) were prepared as the emissive materials for the application of organic light-emitting devices. The relationship between their structures, photophysical properties, electrochemical properties and performances of organic light-emitting devices are described. The multilayered doped devices with a configuration of ITO/NPB (20 nm)/TBADN: biscoumarin compound (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method. All the devices showed green emission with high electroluminescent efficiencies. Especially, the device based on the compound containing pyrene as a bridge group at 7% doping concentration showed the best performance with a maximum brightness of 10552 cd/m2, maximum luminous efficiency of 5.39 cd/A and maximum external quantum efficiency (EQE) of 2.35%. 相似文献
56.
水分子与甘氨酸作用会导致甘氨酸羧基上的质子迁移到氨基上,质子可以通过水分子链进行迁移。采用密度泛函理论的B3LYP/6-31++g**方法研究了水分子链的逐渐增长(1~5个水分子)对质子迁移的影响,发现水分子数少于5时,质子迁移一步完成;水分子数为5时,质子迁移经由一个中间体,需两步完成;水分子链的增长使质子迁移反应的自由能越来越低,但是反应的活化能越来越高,即在热力学上有利于质子迁移反应,在动力学上不利于质子迁移反应。 相似文献
57.
LI Yan-Tuan LIAO Dai-Zheng JIANG Zong-Hui WANG Geng-LinDepartment of Chemistry Nankai University Tianjin China 《中国化学》1995,(3)
Six novel μ-oxamido heterobinuclear complexes, namely Cu(oxae)Ln(Me2bpy)2-(ClO4)3 (Ln=La, Nd, Gd, Tb, Ho, Er), where oxae denotes N, N'-bis(2-aminoethyl)oxamido dian-ion, Me2bpy is 4,4'-dimethyl-2,2'-bipyridyl, have been synthesized and characterized by elemental analyses, IR, conductivity measurements and electronic spectra. The temperature dependence of the magnetic susceptibility of Cu(oxae)Gd(Me2bpy)2(ClO4)3 has been meaured over the range 4-300 K. The least-squares fit of the experimental susceptibilities yielded J - 1.87 cm-1.The observed Gd(Ⅲ)-Cu(Ⅱ) coupling is ferromagnetic. One plausible mechanism that can cause a ferromagnetic coupling between Gd(Ⅲ) and Cu(Ⅱ) is discussed in terms of spin-polarization. 相似文献
58.
Treatment of RuHCl(CO)(PPh3)3 with (3E,5E,7E,9E,11E)-HCC-(CHCH)5- CCH produces [RuCl(CO)(PPh3)2]2[μ-(CHCH)7]. The later complex reacts with PMe3 to give [RuCl(CO)(PMe3)3]2[μ-(CHCH)7], the structure of which has been confirmed by X-ray diffraction. The through-space distance from one Ru to the other is 19.88 Å. 相似文献
59.
Evidence for ion–ion interactions between peptides and anions (HSO4− or ClO4−) derived from high‐acidity acids 下载免费PDF全文
Xiaohua Liu Jean‐Claude Tabet Richard B. Cole 《Journal of mass spectrometry : JMS》2014,49(6):490-497
The existence of gas‐phase electrostatic ion–ion interactions between protonated sites on peptides ([Glu] Fibrinopeptide B, Angiotensin I and [Asn1, Val5]‐Angiotensin II) and attaching anions (ClO4? and HSO4?) derived from strong inorganic acids has been confirmed by CID MS/MS. Evidence for ion–ion interactions comes especially from the product ions formed during the first dissociation step, where, in addition to the expected loss of the anion or neutral acid, other product ions are also observed that require covalent bond cleavage (i.e. H2O loss when several carboxylate groups are present, or NH3 loss when only one carboxylate group is present). For [[Glu] Fibrinopeptide B + HSO4]?, under CID, H2O water loss was found to require less energy than H2SO4 departure. This indicates that the interaction between HSO4? and the peptide is stronger than the covalent bond holding the hydroxyl group, and must be an ion–ion interaction. The strength and stability of this type of ion‐pairing interaction are highly dependent on the accessibility of additional mobile charges to the site. Positive mobile charges such as protons from the peptide can be transferred to the attaching anion to possibly form a neutral that may depart from the complex. Alternatively, an ion–ion interaction can be disrupted by a competing proximal additional negatively charged site of the peptide that can potentially form a salt bridge with the positively charged site and thereby facilitate the attaching anion's departure. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
60.