全文获取类型
收费全文 | 361篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 235篇 |
晶体学 | 5篇 |
力学 | 5篇 |
数学 | 10篇 |
物理学 | 120篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2017年 | 2篇 |
2016年 | 14篇 |
2015年 | 10篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 16篇 |
2007年 | 14篇 |
2006年 | 23篇 |
2005年 | 32篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 3篇 |
1961年 | 2篇 |
1920年 | 2篇 |
1896年 | 2篇 |
1887年 | 2篇 |
排序方式: 共有375条查询结果,搜索用时 15 毫秒
1.
Received July 12, 2001 / Published online February 28, 2002 相似文献
2.
Marko D. Mihovilovic Bernhard Müller Markus Spina Arjumand I. Durrani Peter Stanetty Georg Dazinger Karl Kirchner 《Monatshefte für Chemie / Chemical Monthly》2006,137(6):785-794
Summary. Recombinant Escherichia coli overexpressing Pseudomonas sp. NCIMB 9872 cyclopentanone monooxygenase (CPMO, EC 1.14.13.16) and Acinetobacter sp. NCIMB 9871 cyclohexanone monooxygenase (CHMO, EC 1.14.13.22) have been utilized in whole-cell Baeyer-Villiger biotransformations of prochiral bicycloketones. A significant difference in substrate acceptance and stereoselectivity was
observed for bicyclo[3.3.0] and bicyclo[4.3.0] substrates. A plausible mechanism of these transformations was established
by means of high level DFT/B3LYP calculations suggesting an essential difference in electronic requirements for a successful
enzymatic conversion, which was similarly encountered in recombinant whole-cell mediated biooxidations. Some of the lactones
produced in the biocatalytic Baeyer-Villiger oxidation represent key intermediates for the synthesis of indole alkaloids. 相似文献
3.
4.
5.
Eva BeckerChristian Slugovc Eva RübaChristina Standfest-Hauser Kurt MereiterRoland Schmid Karl Kirchner 《Journal of organometallic chemistry》2002,649(1):55-63
The synthesis and some reactions of the Ru(II) and Ru(IV) half-sandwich complexes [RuCp(EPh3)(CH3CN)2]+ (E=P, As, Sb, Bi) and [RuCp(EPh3)(η3-C3H5)Br]+ have been investigated. The chemistry of this class of compounds is characterized by a competitive coordination of EPh3 either via a RuE or a η6-arene bond, where the latter is favored when the former is weaker, that is in going down the series. Thus in the case of Bi, the starting material [RuCp(CH3CN)3]+ does not react with BiPh3 to give [RuCp(BiPh3)(CH3CN)2]+ but instead gives only the η6-arene species [RuCp(η6-PhBiPh2)]+ and [(RuCp)2(μ-η6,η6-Ph2BiPh)]2+. Similarly, the EPh3 ligand can be replaced by an aromatic solvent or an arene substrate. Thus, the catalytic performance of [RuCp(EPh3)(CH3CN)2]+ for the isomerization of allyl-phenyl ethers to the corresponding 1-propenyl ethers is best with E=P, while the conversion drops significantly using the As and Sb derivatives. By the same token, only [RuCp(PPh3)(CH3CN)2]+ is stable in a non-aromatic solvent, whereas both [RuCp(AsPh3)(CH3CN)2]+ and [RuCp(SbPh3)(CH3CN)2]+ rearrange upon warming to [RuCp(η6-PhEPh2)]+ and related compounds. In addition, the potential of [RuCp(EPh3)(CH3CN)2]+ as precatalysts for the transfer hydrogenation of acetophenone and cyclohexanone has been investigated. Again aromatic substrates are clearly less suited than non-aromatic ones due to facile η6-arene coordination leading to catalyst's deactivation. 相似文献
6.
A convenient general method of preparing 4-acylpyridazines (4) is reported. It involves homolytic acylation of ethyl-4-pyridazinecarboxylate yielding ethyl-5-acyl-4-pyridazinecarboxylates (2) which easily can be converted to4 by alkaline hydrolysis followed by decarboxylation. The hitherto unknown pyridazino[4,5-d]pyridazine-1 (2H) ones bearing an alkyl- or arylsubstituent on C-4 (5a-g) were prepared in quantitative yields by reaction of2 with hydrazine.
10. Mitt.:G. Heinisch, A. Jentzsch undI. Kirchner, Tetrahedron Lett.1978, 619. 相似文献
7.
V. N. Fedoseyev Y. Jading O. C. Jonsson R. Kirchner K. -L. Kratz M. Krieg E. Kugler J. Lettry T. Mehren V. I. Mishin H. L. Ravn T. Rauscher F. Scheerer O. Tengblad P. Van Duppen A. Wöhr 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(1):9-10
The continuum part of the6Li (a,a)6Li (1.47–2.47 MeV) scattering data at Ea=50 MeV are extracted in two discretized bins. Coupled-channel calculations are carried out coupling the 1+ ground state of6Li with both the resonant, 3+
1 state, and two non-resonant continuum states. The discretized continuum of the6Li (p,p)6Li (1.75–3.25 MeV) scattering data at Ep=65 MeV are also analysed on the same footing. In both the cases the effect of coupling is found to be minimal. 相似文献
8.
9.
Robert F. Kirchner Gilda H. Loew Ulrich T. Mueller-Westerhoff 《Theoretical chemistry accounts》1976,41(1):1-6
An iterative extended Hückel molecular orbital calculation was used to obtain wave functions for the ground state of ferrocene and several low lying states of the ferrocenium ion. Photoemission spectra in terms of relative ionization potentials and the electric field gradient at the iron nucleus were calculated for ferrocene andg values and the electric field gradient were calculated for the ferrocenium ion. These values are in good agreement with experiment. The nature of the molecular orbitals was compared with results of previous semi-empirical andab initio calculations. 相似文献
10.
Search on ruggedness of fast gas chromatography-mass spectrometry in pesticide residues analysis 总被引:1,自引:0,他引:1
Kirchner M Matisová E Otrekal R Hercegová A de Zeeuwb J 《Journal of chromatography. A》2005,1084(1-2):63-70
In this study, suitability of fast gas chromatography-mass spectrometry (GC-MS) on a narrow-bore column with a programmed temperature vaporizer for the analysis of pesticide residues in non-fatty food was evaluated. The main objectives were ruggedness and stability of chromatographic system with regards to co-extractives injected. The chromatographic matrix induced response enhancement was found to be strongly dependent on the concentration of residues and is reaching up to 700% compared to the pesticides solutions in a neat solvent. However, the responses of pesticides in matrix-matched standards at different concentration levels do not significantly change during 130 injections. Response enhancement/or decrease is influenced by the sample preparation technique. External calibration with matrix-matched calibration standards should, therefore, provide results with good precision also at the concentration level of 0.005 mg kg(-1). Special attention is given to the performance of the chromatographic column and retention gap with regards to peak widths, peak tailing and different sample preparation methods. During approximately 460 matrix sample injections, the performance of the analytical column was acceptable. GC-MS set-up with 0.15 mm i.d. column can be successfully utilized for the pesticide residues analysis. 相似文献