全文获取类型
收费全文 | 2673篇 |
免费 | 45篇 |
国内免费 | 249篇 |
专业分类
化学 | 2586篇 |
晶体学 | 21篇 |
力学 | 3篇 |
综合类 | 1篇 |
物理学 | 356篇 |
出版年
2023年 | 69篇 |
2022年 | 27篇 |
2021年 | 23篇 |
2020年 | 62篇 |
2019年 | 99篇 |
2018年 | 41篇 |
2017年 | 83篇 |
2016年 | 58篇 |
2015年 | 60篇 |
2014年 | 67篇 |
2013年 | 76篇 |
2012年 | 293篇 |
2011年 | 150篇 |
2010年 | 116篇 |
2009年 | 174篇 |
2008年 | 163篇 |
2007年 | 192篇 |
2006年 | 144篇 |
2005年 | 132篇 |
2004年 | 131篇 |
2003年 | 97篇 |
2002年 | 82篇 |
2001年 | 84篇 |
2000年 | 67篇 |
1999年 | 46篇 |
1998年 | 76篇 |
1997年 | 52篇 |
1996年 | 49篇 |
1995年 | 27篇 |
1994年 | 22篇 |
1993年 | 27篇 |
1992年 | 20篇 |
1991年 | 33篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有2967条查询结果,搜索用时 15 毫秒
51.
《Electroanalysis》2006,18(8):814-822
Holm oak (Quercus ilex) is the dominant tree growing on serpentine soils of northeast Portugal, characterized by elevated soil concentrations of Ni and Mg, combined with low Ca concentrations. Apparently Q. ilex does not suffer from excessive concentrations of Ni in the soil. In this work we report a complexation study of nickel by the relevant ligands present in xylem sap: histidine, aspartic acid, oxalic and citric acids, at 0.10 M ionic strength and pH 5.5. Single and mixed complexes were characterized. To validate the proposed complexation model, diluted solutions of Q. ilex xylem sap were titrated with nickel. All studies were done using square‐wave voltammetry (SWV) at a hanging mercury drop electrode. Due to the dynamic nature of SWV, it is possible to obtain the conditional stability constants of the complexes formed but also to have knowledge on the kinetics of the interconversion of the species present. 相似文献
52.
53.
Harry Adams Sarah A Morris Jeffrey C Motley 《Journal of organometallic chemistry》2004,689(3):522-527
Transfer of dithiolene ligands from [Ni(S2C2Ph2)2] to the dimolybdenum complex [Mo2(μ-C2R2)(CO)4Cp2] (R=CO2Me, Cp=η-C5H5) affords the first example of a dithiolene alkyne complex, [Mo2(μ-C2R2)(μ-S2C2Ph2)2Cp2], together with [Mo2(μ-SCRCR)(μ-SCPhCPh)Cp2] in which sulfur transfer from dithiolene to alkyne has occurred. 相似文献
54.
研究了高效液相色谱-火焰原子吸收光谱联用系统分析信号处理方法,比较了各种处理方法的优缺点,用积分与适应平滑法综合处理色谱峰分析信号,不仅能有效地消除噪声,而且能使分析信号得到加强,以测定镍为例,经积分与适应平滑法综合处理后,检出限改善了2.7倍。 相似文献
55.
Inmaculada Beloso Paulo Prez‐Lourido Jesús Castro Jos A. García‐Vzquez Jaime Romero 《无机化学与普通化学杂志》2005,631(11):2101-2106
Heteroleptic nickel(II) complexes [NiL2L′] of a series of monoanionic and potentially bidentate N‐2‐pyridyl‐sulfonamide ligands [HL] and 2,2′‐bipyridine or 1,10‐Phenanthroline (L′) have been prepared by electrochemical oxidation of a nickel anode in an acetonitrile solution of the ligands. The complexes have been characterized by microanalysis, IR and electronic spectroscopy, magnetic measurements and LSI mass spectrometry. The crystal structure of [Ni(Ms6mepy)2(bipy)] has been determined by x‐ray diffraction and shows the metal in an octahedral NiN6 environment. Octahedral structures are also proposed for the other complexes with the N‐2‐pyridyl‐sulfonamide ligands acting as N,N′ or N, O bidentate systems, depending on the position of the methyl substituent on the pyridine ring. 相似文献
56.
Raif Kurtaran Cengiz Arici Kaan C. Emregül Diner Ülkü Orhan Atakol Mustafa Tatekin 《无机化学与普通化学杂志》2003,629(9):1617-1621
A homo‐dinuclear NiII complex was prepared from 2, 6‐bis(3, 5‐dimethylpyrazolyl)pyridine (Me4‐bpp) and azide ions in nonaqueous media. It was characterized by single crystal X‐ray structural analysis, IR spectroscopy, and elemental analysis. In addition, the electrochemical properties of the compound were determined with cyclic voltammetry in DMF. The title compound crystallizes in the P21/n monoclinic space group, with unit cell parameters a = 8.978(1), b = 12.459(1), c = 17.764(1) Å, ß =100.603(3)°, V = 1953.0(3) Å3, Z = 2. The Ni2+ ion has a distorted octahedral environment involving three nitrogen atoms of the Me4‐bpp ligand, two nitrogen atoms from the bridged azide group, and one nitrogen atom from the terminal azide group. The Ni···Ni distance is 3.273(5) Å. 相似文献
57.
A study of the electrocatalytic oxidation of aspirin on a nickel hydroxide-modified nickel electrode
The electrocatalytic oxidation of aspirin has been investigated on a nickel oxide-modified nickel electrode in alkaline solution.
The process of oxidation and its kinetics have been investigated by using cyclic voltammetry, chronoamperometry, and electrochemical
impedance spectroscopy techniques and also steady-state polarization measurements. Voltammetric studies have indicated that
in the presence of aspirin, the anodic peak current of low-valence nickel species increases, followed by a decrease in the
corresponding cathodic current. This indicates that aspirin was oxidized on the redox mediator immobilized on the electrode
surface via an electrocatalytic mechanism. The rate constant of the catalytic oxidation of aspirin and the electron transfer
coefficient have been found to be 1.15×105 cm3 mol−1s−1 and 0.49, respectively. Impedance measurements show that aspirin is diffused into the bulk of the modifier film, and the
oxidation process of aspirin occurs in the bulk of nickel oxide film. It has been shown that by using this modified electrode,
aspirin can be determined with a detection limit of 4.8×10−5 and successfully applied for determination of aspirin in tablet. 相似文献
58.
合成了双[水杨醛(对硝基苯)亚胺]合镍催化剂A和双[水杨醛(对甲氧基苯)亚胺]合镍催化剂B.该两种双[N,O]配体合镍配合物/MAO催化体系能有效地催化极性单体甲基丙烯酸甲酯(MMA)聚合,催化活性可高达105gPMMA/(molNi.h).其中配体对位含有硝基吸电子(共轭)效应的催化剂A/MAO体系有相对较高的聚合反应热稳定性,温度达50℃时仍具有高催化活性.配体对位含有甲氧基推电子(共轭)效应的催化剂B/MAO则在30℃和Al/Ni摩尔比为600时表现出最高的催化活性.催化剂B/MAO体系催化得到PMMA的链序列结构以间规为主(含高达73.2%rr三元组),具有较高的玻璃化转变温度(Tg=106.4℃). 相似文献
59.
60.
The electrochemical behavior of a nickel electrode with limited volume (LVE) electrodeposited as a thin layer on gold has
been studied. The influence of the gold matrix on the electrochemical Ni electrode behavior has been considered. The electrosorption
and oxidation of carbon monoxide on the Ni surface and its influence on hydrogen sorption has also been demonstrated.
Received: 21 May 1997 / Accepted: 9 June 1997 相似文献