全文获取类型
收费全文 | 589篇 |
免费 | 28篇 |
国内免费 | 1篇 |
专业分类
化学 | 500篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 50篇 |
物理学 | 64篇 |
出版年
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 28篇 |
2014年 | 24篇 |
2013年 | 40篇 |
2012年 | 43篇 |
2011年 | 36篇 |
2010年 | 29篇 |
2009年 | 25篇 |
2008年 | 33篇 |
2007年 | 31篇 |
2006年 | 33篇 |
2005年 | 25篇 |
2004年 | 35篇 |
2003年 | 20篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 13篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1980年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1962年 | 2篇 |
1938年 | 1篇 |
1936年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有618条查询结果,搜索用时 31 毫秒
61.
Adam Neuba Dr. Sonja Herres‐Pawlis Oliver Seewald Janna Börner Andreas J. Heuwing Ulrich Flörke Prof. Dr. Gerald Henkel 《无机化学与普通化学杂志》2010,636(15):2641-2649
The transition metal complexes with the ligand 1,3‐bis(N,N,N′,N′‐tetramethylguanidino)propane (btmgp), [Mn(btmgp)Br2] ( 1 ), [Co(btmgp)Cl2] ( 2 ), [Ni(btmgp)I2] ( 3 ), [Zn(btmgp)Cl2] ( 4 ), [Zn(btmgp)(O2CCH3)2] ( 5 ), [Cd(btmgp)Cl2] ( 6 ), [Hg(btmgp)Cl2] ( 7 ) and [Ag2(btmgp)2][ClO4]2·2MeCN ( 8 ), were prepared and characterised for the first time. The stoichiometric reaction of the corresponding water‐free metal salts with the ligand btmgp in dry MeCN or THF resulted in the straightforward formation of the mononuclear complexes 1 – 7 and the binuclear complex 8 . In complexes with MII the metal ion shows a distorted tetrahedral coordination whereas in 8 , the coordination of the MI ion is almost linear. The coordination behavior of btmgp and resulting structural parameters of the corresponding complexes were discussed in an comparative approach together with already described complexes of btmgp and the bisguanidine ligand N1,N2‐bis(1,3‐dimethylimidazolidin‐2‐ylidene)‐ethane‐1,2‐diamine (DMEG2e), respectively. 相似文献
62.
Birgit Krimmel Friederike Swoboda Sonja Solar Gottfried Reznicek 《Radiation Physics and Chemistry》2010,79(12):1247-1254
The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement –OCH3 by ?OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC–UV and LC–ESI–MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed. 相似文献
63.
Based on Berreman's 4 × 4 matrix formalism [W. Berreman, J. Opt. Soc. Am. 62, 502 (1972)] we derive simplified expressions for the reflection formulas from the a-c crystal surface for non-normal incidence. The computational effort to apply the formulas was found to be only insignificantly higher than those for normal incidence, but considerably lower than for the general expressions. Consequently, the simplified formulas can be readily applied for dispersion analysis of spectra gained by spectroscopic ellipsometry or attenuated total reflection. 相似文献
64.
Anne Chartogne Marco Gaspari Sonja Jespersen Brigitte Buscher Elwin Verheij Robert van der Heijden Rv Ubbo Tjaden Jan van der Greef 《Rapid communications in mass spectrometry : RCM》2002,16(3):201-207
In the present work, we describe a collection system for the off-line coupling of capillary isoelectric focusing (CIEF) with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. In this system, the capillary effluent is directly deposited in fractions onto the MALDI target via the use of a sheath liquid. The collected fractions are subsequently supplemented with matrix and further analysed by MALDI-TOF mass spectrometry for mass assignment. The experimental set-up includes a fiber optic based UV detector operating at 280 nm, which allows the study of the influence of the sheath liquid composition on the CIEF separation. The influence of the carrier ampholyte concentration on the protein MALDI spectra was also evaluated and the feasibility of the collection method was finally demonstrated with a mixture of four standard proteins. 相似文献
65.
Sonja Kracht Dr. Matthias Messerer Dr. Matthieu Lang Dr. Sonja Eckhardt Dr. Miriam Lauz Prof. Bernard Grobéty Prof. Katharina M. Fromm Prof. Bernd Giese 《Angewandte Chemie (International ed. in English)》2015,54(10):2912-2916
Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag+ ions bound by peptides with histidine as the Ag+‐binding amino acid and tyrosine as photoinducible electron donor cannot be reduced to Ag nanoparticles (AgNPs) under ET conditions because the peptide prevents the aggregation of Ag atoms to form AgNPs. Only in the presence of chloride ions, which generate AgCl microcrystals in the peptide matrix, does the synthesis of AgNPs occur. The reaction starts with the formation of 100 nm Ag@AgCl/peptide nanocomposites which are cleaved into 15 nm AgNPs. This defined transformation from large nanoparticles into small ones is in contrast to the usually observed Ostwald ripening processes and can be followed in detail by studying time‐resolved UV/Vis spectra which exhibit an isosbestic point. 相似文献
66.
Kyoung-Soon Jang Roger R. Nani Anastasia Kalli Sergiy Levin Axel Müller Sonja Hess Sarah E. Reisman William M. ClemonsJr. 《Analytical and bioanalytical chemistry》2015,407(20):6181-6190
In Campylobacterales and related ε-proteobacteria with N-linked glycosylation (NLG) pathways, free oligosaccharides (fOS) are released into the periplasmic space from lipid-linked precursors by the bacterial oligosaccharyltransferase (PglB). This hydrolysis results in the same molecular structure as the oligosaccharide that is transferred to a protein to be glycosylated. This allowed for the general elucidation of the fOS-branched structures and monosaccharides from a number of species using standard enrichment and mass spectrometry methods. To aid characterization of fOS, hydrazide chemistry has often been used for chemical modification of the reducing part of oligosaccharides resulting in better selectivity and sensitivity in mass spectrometry; however, the removal of the unreacted reagents used for the modification often causes the loss of the sample. Here, we develop a more robust method for fOS purification and characterize glycostructures using complementary tandem mass spectrometry (MS/MS) analysis. A cationic cysteine hydrazide derivative was synthesized to selectively isolate fOS from periplasmic fractions of bacteria. The cysteine hydrazide nicotinamide (Cyhn) probe possesses both thiol and cationic moieties. The former enables reversible conjugation to a thiol-activated solid support, while the latter improves the ionization signal during MS analysis. This enrichment was validated on the well-studied Campylobacter jejuni by identifying fOS from the periplasmic extracts. Using complementary MS/MS analysis, we approximated data of a known structure of the fOS from Campylobacter concisus. This versatile enrichment technique allows for the exploration of a diversity of protein glycosylation pathways. 相似文献
67.
68.
69.