全文获取类型
收费全文 | 138篇 |
免费 | 3篇 |
专业分类
化学 | 98篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 41篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 11篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 13篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1923年 | 1篇 |
排序方式: 共有141条查询结果,搜索用时 62 毫秒
51.
By using the neutral bidentate nitrogen-containing ligand, bis(3,5-diisopropyl-1-pyrazolyl)methane (L1' '), the copper(I) complexes [Cu(L1' ')2](CuCl2) (1CuCl2), [Cu(L1' ')2](ClO4) (1ClO4), [Cu(L1' ')]2(ClO4)2 (2ClO4), [Cu(L1' ')]2(BF4)2 (2BF4), [Cu(L1' ')(NCMe)](PF6) (3PF6), [Cu(L1' ')(PPh3)](ClO4) (4ClO4), [Cu(L1' ')(PPh3)](PF6) (4PF6), [{Cu(L1' ')(CO)}2(mu-ClO4)](ClO4) (5ClO4), and the copper(II) complexes [{Cu(L1' ')}2(mu-OH)2(mu-ClO4)2] (6), and [Cu(L1' ')Cl2] (7) were systematically synthesized and fully characterized by X-ray crystallography and by IR and 1H NMR spectroscopy. In the case of copper(II), ESR spectroscopy was also applied. In comparison with the related neutral tridentate ligand L1', bis-chelated copper(I) complexes and binuclear linear-coordinated copper(I) complexes are easy to obtain with L1' ', like 1CuCl2, 1ClO4, 2ClO4, and 2BF4. Importantly, stronger and bulkier ligands such as acetonitrile (3PF6) and especially triphenylphosphine (4ClO4 and 4PF6) generate three-coordinate structures with a trigonal-planar geometry. Surprisingly, for the smaller ligand carbon monoxide, a mononuclear three-coordinate structure is very unstable, leading to the formation of a binuclear complex (5ClO4) with one bridging perchlorate anion, such that the copper(I) centers are four-coordinate. The same tendency is observed for the copper(II) bis(mu-hydroxo) compounds 6, which is additionally bridged by two perchlorate anions. Both copper(II) complexes 6 and 7 were obtained by molecular O2 oxidation of the corresponding copper(I) complexes. A comparison of the new copper(I) triphenylphosphine complexes 4ClO4 and 4PF6 with corresponding species obtained with the related tridentate ligands L1' and L1 (8ClO4 and 9, respectively) reveals surprisingly small differences in their spectroscopic properties. Density functional theory (DFT) calculations are used to shed light on the differences in bonding in these compounds and the spectral assignments. Finally, the reactivity of the different bis(pyrazolyl)methane complexes obtained here toward PPh3, CO, and O2 is discussed. 相似文献
52.
Sempombe J Galinato MG Elmore BO Fan W Guillemette JG Lehnert N Kirk ML Feng C 《Inorganic chemistry》2011,50(15):6859-6861
We have obtained low-temperature magnetic circular dichroism (MCD) spectra for ferric cyano complexes of the wild type and E546N mutant of a human inducible nitric oxide synthase (iNOS) oxygenase/flavin mononucleotide (oxyFMN) construct. The mutation at the FMN domain has previously been shown to modulate the MCD spectra of the l-arginine-bound ferric iNOS heme (Sempombe, J.; et al. J. Am. Chem. Soc. 2009, 131, 6940-6941). The addition of l-arginine to the wild-type protein causes notable changes in the CN(-)-adduct MCD spectrum, while the E546N mutant spectrum is not perturbed. Moreover, the MCD spectral perturbation observed with l-arginine is absent in the CN(-) complexes incubated with N-hydroxy-L-arginine, which is the substrate for the second step of NOS catalysis. These results indicate that interdomain FMN-heme interactions exert a long-range effect on key heme axial ligand-substrate interactions that determine substrate oxidation pathways of NOS. 相似文献
53.
The reduction of nitrite to nitric oxide in dissimilatory denitrification is carried out by copper nitrite reductases (CuNIRs) via a type 2 copper site. Extended studies on CuNIRs in combination with model complexes have allowed for the establishment of two potential mechanisms for this transformation. Recent experimental and computational results have revealed further details of this process. In addition, the interaction of NO with copper sites has recently gained much attention. This review discusses recent results in the context of the known coordination chemistry of CuNIRs. 相似文献
54.
Dieter Froning Gerd Gaiselmann Uwe Reimer Jan Brinkmann Volker Schmidt Werner Lehnert 《Transport in Porous Media》2014,103(3):469-495
The relationship between the 3D morphology of gas-diffusion layers (GDL) of HT-PEFCs and their functionality is analyzed. A stochastic model describing the microstructure of paper-type GDL is combined with the Lattice-Boltzmann method (LBM) to simulate gas transport within the GDL microstructure. Virtual 3D microstructures representing paper-type GDL are generated by a stochastic model, where the binder morphology is systematically modified. On these structures, single phase single component gas flow is computed by the LBM. Quality criteria evaluating the spatial homogeneity of gas supply are introduced and related to the binder morphology. The spatial homogeneity of the gas supply is analyzed by a parametrized stochastic model describing the gas flow at the exit of the GDL. This approach gives insight into the spatial structure of the gas flow at the GDL exit. The quality of gas supply is quantified by characterizing size and arrangement of regions with high gas supply. This stochastic gas flow model predicts the quality of gas supply for further binder morphologies. Analyzing the quality criteria and the stochastic evaluation of the spatial structure of the gas flow field at the GDL exit, it is found that the binder morphology has an essential influence on the gas supply. 相似文献
55.
Ralf Lehnert 《Hyperfine Interactions》2012,209(1-3):29-33
Various approaches to physics beyond the Standard Model can lead to small violations of CPT invariance. Since CPT symmetry can be measured with ultra-high precision, CPT tests offer an interesting phenomenological avenue to search for underlying physics. We discuss this reasoning in more detail, comment on the connection between CPT and Lorentz invariance, and review how CPT breaking would affect the (anti)hydrogen spectrum. 相似文献
56.
H. Edel D. Erber R. Lehnert W. Buscher K. Cammann 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):292-294
The evaluation of accuracy and efficiency of the frequency-modulated simultaneous Atomic Absorption Spectrometry (FremsAAS) has been extended to an arrangement with EDL as light sources. Fundamental calibrations have been worked out for As, Se and Sb using a graphite furnace as well as hydride generation in combination with a heated quartz tube as atomization unit. The characteristic data are in good agreement with results obtained by conventional single-channel AAS instruments. Determinations in three standard reference materials with different complex matrices resulted in complete agreement with the certified values. 相似文献
57.
W. Lehnert 《Tetrahedron》1973,29(4):635-638
In the presence of titanium tetrachloride and pyridine in THF, diethyl malonate undergoes condensation with aliphatic and aromatic ketones. The yields of the resulting α,β-unsaturated compounds are good even in cases, where other condensation methods are unsuccessful. Products, resulting from α-mono-, α,α-, α,α′-di- and α,α,α-trihalogeno ketones are probably of special interest as useful intermediates for the preparation of heterocycles. 相似文献
58.
Alexander Schrder Klaus Wippermann Jürgen Mergel Werner Lehnert Detlef Stolten Tilman Sanders Thorsten Baumhfer Dirk U. Sauer Ingo Manke Nikolay Kardjilov Andr Hilger Jana Schloesser John Banhart Christoph Hartnig 《Electrochemistry communications》2009,11(8):1606-1609
The current and fluid distribution in Direct Methanol Fuel Cells (DMFCs) was investigated in situ by means of combined high resolution neutron radiography and locally resolved current distribution measurements. The used neutron radiography set-up allows high spatial resolutions down to 70 μm at the full test cell area. A local formation of water droplets in the cathode flow field channels could be observed. Strongly inhomogeneous current distributions during cathodic flooding processes result in a performance loss of up to 30% of the initial value. Single CO2 bubbles can be observed at low current densities. The water and current distribution during bi-functional operation of a DMFC was measured for the first time. 相似文献
59.
A.?Keane T.?Dahms J.?Lehnert S.A.?Suryanarayana P.?H?vel E.?Sch?llEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(12):407
We use a generic model for type-I excitability (known as the SNIPER or SNIC model) to describe the local dynamics of nodes within a network in the presence of non-zero coupling delays. Utilising the method of the Master Stability Function, we investigate the stability of the zero-lag synchronised dynamics of the network nodes and its dependence on the two coupling parameters, namely the coupling strength and delay time. Unlike in the FitzHugh-Nagumo model (a model for type-II excitability), there are parameter ranges where the stability of synchronisation depends on the coupling strength and delay time. One important implication of these results is that there exist complex networks for which the adding of inhibitory links in a small-world fashion may not only lead to a loss of stable synchronisation, but may also restabilise synchronisation or introduce multiple transitions between synchronisation and desynchronisation. To underline the scope of our results, we show using the Stuart-Landau model that such multiple transitions do not only occur in excitable systems, but also in oscillatory ones. 相似文献
60.