全文获取类型
收费全文 | 7044篇 |
免费 | 758篇 |
国内免费 | 1474篇 |
专业分类
化学 | 6459篇 |
晶体学 | 44篇 |
力学 | 471篇 |
综合类 | 68篇 |
数学 | 1028篇 |
物理学 | 1206篇 |
出版年
2024年 | 44篇 |
2023年 | 146篇 |
2022年 | 290篇 |
2021年 | 356篇 |
2020年 | 526篇 |
2019年 | 345篇 |
2018年 | 294篇 |
2017年 | 270篇 |
2016年 | 362篇 |
2015年 | 290篇 |
2014年 | 437篇 |
2013年 | 600篇 |
2012年 | 382篇 |
2011年 | 383篇 |
2010年 | 315篇 |
2009年 | 368篇 |
2008年 | 390篇 |
2007年 | 381篇 |
2006年 | 357篇 |
2005年 | 321篇 |
2004年 | 293篇 |
2003年 | 335篇 |
2002年 | 338篇 |
2001年 | 217篇 |
2000年 | 188篇 |
1999年 | 155篇 |
1998年 | 133篇 |
1997年 | 102篇 |
1996年 | 110篇 |
1995年 | 81篇 |
1994年 | 75篇 |
1993年 | 55篇 |
1992年 | 65篇 |
1991年 | 40篇 |
1990年 | 30篇 |
1989年 | 23篇 |
1988年 | 26篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 29篇 |
1984年 | 17篇 |
1983年 | 6篇 |
1982年 | 19篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1973年 | 5篇 |
1972年 | 3篇 |
排序方式: 共有9276条查询结果,搜索用时 15 毫秒
101.
《Electroanalysis》2006,18(7):649-654
For the first time, the voltammetry of an ensemble of immobilized benzonitrile microdroplets containing 5,10,15,20‐tetraphenyl‐21H,23H‐porphine iron (III) chloride, TPPFeCl immobilized at platinum electrodes immersed in various aqueous electrolytes has been explored. The reduction of TPPFeCl was observed with the voltammetric response seen to be highly dependent on the nature of ions in the surrounding aqueous phase. Unlike voltammetry in purely homogeneous solution the nature of the aqueous electrolyte can influence the voltammetry in the droplet phase. The electrochemical reduction of TPPFeCl contained within tetrabutylammonium chloride (TBACl) supported benzonitrile (PhCN) microdroplets immersed into an aqueous solution of TBACl was first studied. During TPPFeCl reduction the resulting [TPPFeCl]? species is stabilized due to the excess of chloride anions inside the oil droplet. Voltammograms of homogeneous solutions of PhCN supported with TBACl show similar chemically reversible process which is also attributed to the stable [TPPFeCl]? species. This anion stabilization was not observed when the oil droplets were supported with tetrabutylammonium perchlorate (TBAP) or when the PhCN solution bathing the microdroplet ensemble was supported with TBAP resulting in a chemically irreversible process. The voltammetry of unsupported droplets immobilized on a platinum electrode immersed in different aqueous electrolytes was also explored and the fate of the [TPPFeCl]? species formed considered during the reduction sweep. Similarities and difference to voltammetry in purely homogeneous media are noted and the use of droplet voltammetry provides complimentary information. 相似文献
102.
Cline Schneider Frdric Doucet Stanislav Strekopytov Christopher Exley 《Polyhedron》2004,23(18):3185-3191
Hydroxyaluminosilicates (HAS) are critical secondary mineral phases in the biogeochemical cycle of aluminium. They are formed from the reaction of silicic acid (Si(OH)4) with an aluminium hydroxide template and act as a geochemical control of the biological availability of Al. There are two main forms of HAS which we have called HASA and HASB and which of these will predominate will depend upon the Si(OH)4 to Al ratio in any one environment. In all but the most heavily weathered environments or those undergoing a progressive acidification Si(OH)4 will be present in significant excess to Al and HASB will be the dominant secondary mineral phase. We have tried to determine the solubility of HASB(s) so that its contribution to Al solubility control might be compared with other secondary minerals such as Al(OH)3(gibbsite). In preliminary experiments, the dissolution of HASB(s) was found to be non-congruent with almost no Al being released during 18 months ageing. We then demonstrated that HASB(s) was significantly less soluble than Al(OH)3(s) prepared under identical experimental conditions. We have used this information to describe a solubility expression for HASB(s) at a predefined quasi-equibrium and to calculate a solubility constant.
K*Al2Si2O5(OH)4=[Al2O4+][SiO2]2[OH-]4