全文获取类型
收费全文 | 432篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
化学 | 245篇 |
力学 | 18篇 |
数学 | 70篇 |
物理学 | 111篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 19篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 34篇 |
2012年 | 29篇 |
2011年 | 37篇 |
2010年 | 24篇 |
2009年 | 14篇 |
2008年 | 24篇 |
2007年 | 10篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 13篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有444条查询结果,搜索用时 15 毫秒
341.
342.
Neumann M. Abdallah B. Holzer L. Willot F. Schmidt V. 《Transport in Porous Media》2019,128(1):179-200
Transport in Porous Media - We compare two conceptually different stochastic microstructure models, i.e., a graph-based model and a pluri-Gaussian model, that have been introduced to model the... 相似文献
343.
New Schiff base (H2L) ligand is prepared via condensation of o-phthaldehyde and 2-aminobenzoic acid in 1:2 ratio. Metal complexes are prepared and characterized using elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, 1H NMR, ESR and thermal analysis (TGA). From the elemental analyses data, the complexes were proposed to have the general formulae [MCl(L)(H2O)]·2H2O (where M = Cr(III) and Fe(III)); [M(L)]·yH2O (where M = Mn(II), Ni(II), Cu(II) and Zn(II), y = 1–2) and [M(L)(H2O)n]·yH2O (where M = Co(II) (n = y = 2), Co(II) (n = y = 1), Ni(II) (n = 2, y = 1). The molar conductance data reveal that all the metal chelates were non-electrolytes. IR spectra show that H2L is coordinated to the metal ions in a bi-negative tetradentate manner with NOON donor sites of the azomethine-N and carboxylate-O. The 1H NMR spectral data indicate that the two carboxylate protons are also displaced during complexation. From the magnetic and solid reflectance spectra, it was found that the geometrical structure of these complexes are octahedral (Cr(III), Fe(III), Co(II) and Ni(II)), square planar (Cu(II)), trigonal bipyramidal (Co(II)) and tetrahedral (Mn(II), Ni(II) and Zn(II)). The thermal behaviour of these chelates showed that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the ligand molecule in the subsequent steps. The biological activity data show that the metal complexes to be more potent/antibacterial than the parent Shciff base ligand against one or more bacterial species. 相似文献
344.
Analytical and environmental aspects of the flame retardant tetrabromobisphenol-A and its derivatives 总被引:2,自引:0,他引:2
Covaci A Voorspoels S Abdallah MA Geens T Harrad S Law RJ 《Journal of chromatography. A》2009,1216(3):346-363
The present article reviews the available literature on the analytical and environmental aspects of tetrabromobisphenol-A (TBBP-A), a currently intensively used brominated flame retardant (BFR). Analytical methods, including sample preparation, chromatographic separation, detection techniques, and quality control are discussed. An important recent development in the analysis of TBBP-A is the growing tendency for liquid chromatographic techniques. At the detection stage, mass-spectrometry is a well-established and reliable technology in the identification and quantification of TBBP-A. Although interlaboratory exercises for BFRs have grown in popularity in the last 10 years, only a few participating laboratories report concentrations for TBBP-A. Environmental levels of TBBP-A in abiotic and biotic matrices are low, probably due to the major use of TBBP-A as reactive FR. As a consequence, the expected human exposure is low. This is in agreement with the EU risk assessment that concluded that there is no risk for humans concerning TBBP-A exposure. Much less analytical and environmental information exists for the various groups of TBBP-A derivatives which are largely used as additive flame retardants. 相似文献
345.
346.
347.
348.
Fu Hailing Theodossiades Stephanos Gunn Ben Abdallah Imad Chatzi Eleni 《Nonlinear dynamics》2020,101(4):2131-2143
Nonlinear Dynamics - Harvesting ultra-low frequency random vibration, such as human motion or turbine tower oscillations, has always been a challenge, but could enable many potential self-powered... 相似文献
349.
Khadijah A. Jabal Hossam M. Abdallah Gamal A. Mohamed Ibrahim A. Shehata Mohammad Y. Alfaifi Serag Eldin I. Elbehairi 《Natural product research》2020,34(15):2167-2172
AbstractThe CHCl3 fraction of MeOH extract of Periploca somaliensis (family Asclepiadaceae) fruits afforded a new scalarane sesterterpene, namely perisomalien A (1), along with lupeol acetate (2), β-amyrin (3), cycloart-23Z-ene-3β,25-diol (4), and β-sitosterol-3-O-β-D-glucopyranoside (5). Their chemical structures were established by various spectroscopic analyses, in addition to comparison with the formerly reported data. Moreover, the cytotoxic activity of these metabolites was assessed towards MCF-7, HepG2, and HCT-116 tumour cell lines using sulforhodamine B (SRB) assay. Compound 4 showed the most potent cytotoxic profile with IC50 9.0?µM towards MCF-7, compared to doxorubicin (IC50 0.18?µM). Also, 1 and 4 possessed the most potent effect towards HepG2 with IC50s 26.7 and 25.9?μM, respectively. In addition, all tested compounds showed cytotoxic effects with IC50 values ranging from 19.9 to 39.3?µM against HCT-116. 相似文献
350.