全文获取类型
收费全文 | 867篇 |
免费 | 42篇 |
国内免费 | 6篇 |
专业分类
化学 | 650篇 |
晶体学 | 3篇 |
力学 | 16篇 |
数学 | 112篇 |
物理学 | 134篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 20篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 34篇 |
2015年 | 25篇 |
2014年 | 33篇 |
2013年 | 39篇 |
2012年 | 50篇 |
2011年 | 72篇 |
2010年 | 38篇 |
2009年 | 36篇 |
2008年 | 63篇 |
2007年 | 52篇 |
2006年 | 59篇 |
2005年 | 51篇 |
2004年 | 43篇 |
2003年 | 22篇 |
2002年 | 35篇 |
2001年 | 21篇 |
2000年 | 15篇 |
1999年 | 11篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1970年 | 4篇 |
1963年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有915条查询结果,搜索用时 156 毫秒
111.
Emilio López-Anreus Salvador Garrigues Migue de la Guardia 《Fresenius' Journal of Analytical Chemistry》1995,351(8):724-728
A simple and direct flow injection (FIA) procedure has been developed for the determination of the stabilizing agent ethanol in chloroform samples. The procedure is based on the use of the absorbance band of ethanol in the near-infrared (NIR) region at 2272 nm, measured in front of a reference sample of chloroform stabilized with amylene. The method developed provides a limit of detection of 0.0045% (v/v) and a dynamic range until 10% (v/v) with a typical variation coefficient of 0.4% for six independent analysis of a real sample containing approximately 1% (v/v) of ethanol. The sample injection frequency allowed by the method is 78 h–1. 相似文献
112.
113.
Claudio Gutierrez P. Salvador J.B. Goodenough 《Journal of Electroanalytical Chemistry》1982,134(2):325-334
The electrochemical behaviour of NiTiO3 has been studied. The interest in this mixed-metal oxide lays in its possible use for solar-energy conversion. Anodic oxidation of NiTi03 was very irreversible. The electrode became aged, probably due to formation of a porous film of an irreducible higher oxide. The stirring-independent Cottrell behaviour of the anodic oxidation of NiTiO3 should be due to current limitation by diffusion of a reaction product away from the NiTi03 surface through this irreducible higher oxide, which should be of a porous nature. The diffusion-limiting species could not be OH?, as the Cottrell slopes only increased by about five times for a pH increase from 3 to 14. Five and two processes were involved in the anodic oxidation of NiTiO3 at pH 14 and 3 respectively, as determined by chronopotentiometry. The same number of processes appeared upon inversion of the current. 相似文献
114.
115.
About one monolayer of Ti3+ species is detectable at the surface of reduced SrTiO3(111) single crystals by XPS and UPS. O2, H2 and H2O have been adsorbed in the dark and the decrease on the concentration of the Ti3+ species has been monitored as a function of the gas exposures. Subsequent band gap illumination partially restores the Ti3+ initial concentration in the cases of O2 and H2 exposures but not in the case of H2O. The Ti3+ photogeneration on the oxygen covered surface is associated with oxygen photodesorption as indicated by XPS and UPS. UPS measurements give evidence for surface hydroxylation resulting from water and hydrogen adsorption. The activity of the stoichiometric SrTiO3(111) crystal face for O2 and H2 adsorption is very low when compared with the reduced SrTiO3 samples. 相似文献
116.
Bermúdez-Saldaña JM Escuder-Gilabert L Villanueva-Camañas RM Medina-Hernández MJ Sagrado S 《Journal of chromatography. A》2005,1094(1-2):24-33
The retention factor is one of the most universally used parameters in chromatography. The errors associated with the conventional ways to determine the retention factor of compounds in liquid chromatography are studied and compared with those corresponding to new approaches. The later avoid the use of extra-column time and hold-up time values, which have proven to be tedious and ambiguous. Simulations and real data, used to examine the accuracy of four different approaches (two classic and two new), suggest that the new approaches could be considered more satisfactory than the classic ones. 相似文献
117.
Andresa JS Reis RM Gonzalez EP Santos LS Eberlin MN de Paula Nascente PA Tanimoto ST Machado SA Rodrigues-Filho UP 《Journal of colloid and interface science》2005,286(1):303-309
The present paper describes the one-pot procedure for the formation of self-assembled thin films of two silanes on the model oxidized silicon wafer, SiO2/Si. SiO2/Si is a model system for other surfaces, such as glass, quartz, aerosol, and silica gel. MALDI-TOF MS with and without a matrix, XPS, and AFM have confirmed the formation of self-assembled thin films of both 3-imidazolylpropyltrimethoxysilane (3-IPTS) and 4-(N-propyltriethoxysilane-imino)pyridine (4-PTSIP) on the SiO2/Si surface after 30 min. Longer adsorption times lead to the deposition of nonreacted 3-IPTS precursors and the formation of agglomerates on the 3-IPTS monolayer. The formation of 4-PTSIP self-assembled layers on SiO2/Si is also demonstrated. The present results for the flat SiO2/Si surface can lead to a better understanding of the formation of a stationary phase for affinity chromatography as well as transition-metal-supported catalysts on silica and their relationship with surface roughness and ordering. The 3-IPTS and 4-PTSIP modified SiO2/Si wafers can also be envisaged as possible built-on-silicon thin-layer chromatography (TLC) extraction devices for metal determination or N-heterocycle analytes, such as histidine and histamine, with "on-spot" MALDI-TOF MS detection. 相似文献
118.
119.
Salvador Ferrer Odile Robach Olivier Balmes Helena Isern Iona Popa Marcelo Ackerman 《Surface science》2010,604(21-22):1840-1844
Fe(001) surfaces of whiskers of good crystalline quality were oxidized in a pressure range from 10? 7 mbar to 1 bar at different temperatures. Epitaxial Fe3O4 and FeO thin films with negligible strain were grown depending on the oxidation temperatures. The kinetics of the oxide thickness growth was measured and compared with the predictions of the Fromhold–Cook theory for oxidation of metals. Some discrepancies were found and a possible explanation is presented. 相似文献
120.
This article proposes a dynamic Bayesian framework to analyze the leadership relationships between mutual funds. To this end, a two‐step procedure is proposed. First, a Bayesian rolling window based on the Capital Asset Pricing Model is used to estimate the evolution of mutual funds' market exposure over time. Then, a vector autoregressive (VAR) model is used to analyze the leader‐follower relationship between pair of mutual funds. Several leadership measures are studied. An application to Spanish mutual funds is carried out. In addition, the study examines the determining factors of mutual fund leadership. 相似文献