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排序方式: 共有166条查询结果,搜索用时 15 毫秒
1.
G. P. Westphal 《Journal of Radioanalytical and Nuclear Chemistry》1994,179(1):55-59
By adapting noise filtering to individual pulse intervals, the Preloaded Filter (PLF) pulse processor (1) combines high resolution with optimum throughput efficiency. As a consequence, its output pulse interval distribution contains strong non-random components which render conventional ADC dead-time correction an impossibility. Quantitative correction of dead-time and pileup losses of the PLF processor may be achieved, however, with the Virtual Pulse Generator (2), together with a new, distribution-independent method of measuring ADC losses which is based on a pulse counting technique. 相似文献
2.
3.
4.
The solvation of the lithium and sodium ions in dimethyl sulfoxide solution was theoretically investigated using ab initio calculations coupled with the hybrid cluster-continuum model, a quasichemical theory of solvation. We have investigated clusters of ions with up to five dimethyl sulfoxide (DMSO) molecules, and the bulk solvent was described by a dielectric continuum model. Our results show that the lithium and sodium ions have four and five DMSO molecules into the first coordination shell, and the calculated solvation free energies are -135.5 and -108.6 kcal mol(-1), respectively. These data suggest a solvation free energy value of -273.2 kcal mol(-1) for the proton in dimethyl sulfoxide solution, a value that is more negative than the present uncertain experimental value. This and previous studies on the solvation of ions in water solution indicate that the tetraphenylarsonium tetraphenylborate assumption is flawed and the absolute value of the free energy of transfer of ions from water to DMSO solution is higher than the present experimental values. 相似文献
5.
Tânia Regina Silva Eduard Westphal Hugo Gallardo Iolanda Cruz Vieira 《Electroanalysis》2014,26(8):1801-1809
This paper describes the development of a new sensor based on an ionic organic film. The amphiphilic molecule, 4‐[(4‐decyloxyphenyl)‐ethynyl]‐1‐methylpyridinium iodide (10PyI), which has liquid‐crystalline properties, was synthesized and applied in the construction of a GCE/10PyI sensor. Analytical parameters for caffeic acid, repeatability (4.8 %), reproducibility (2.8 %), linearity (two ranges: 9.9×10?7 to 3.8×10?5 mol L?1 and 4.7×10?5 to 9.9×10?5 mol L?1) and detection limits (9.0×10?7 mol L?1 and 8.7×10?6 mol L?1), were determined. The method was successfully applied in the determination of total phenolic compounds (TPC) in mate herb extracts. 相似文献
6.
A LEED intensity analysis of Cu{0 0 1}c(2 × 2)-Cl has given an excellent fit of theory to experiment with Cl in the fourfold symmetrical hollows in a simple overlayer structure with a Cu-Cl bond length of 2.38 Å. This structure is consistent with an analysis of angle-resolved photoemission measurements made in the same experiments and published elsewhere. These results help confirm the LEED analysis of the analogous system Ag{0 0 1}c(2 × 2)-Cl which gave the same structure, but had been rejected by an independent photoemission analysis. 相似文献
7.
V. V. Nesvizhevsky A. K. Petukhov H. G. Börner T. A. Baranova A. M. Gagarski G. A. Petrov K. V. Protasov A. Yu Voronin S. Baeßler H. Abele A. Westphal L. Lucovac 《The European Physical Journal C - Particles and Fields》2005,40(4):479-491
We have studied neutron quantum states in the potential well formed by the earths gravitational field and a horizontal mirror. The estimated characteristic sizes of the neutron wave functions in the two lowest quantum states correspond to expectations with an experimental accuracy. A position-sensitive neutron detector with an extra-high spatial resolution of
m was developed and tested for this particular experiment, to be used to measure the spatial density distribution in a standing neutron wave above a mirror for a set of some of the lowest quantum states. The present experiment can be used to set an upper limit for an additional short-range fundamental force. We studied methodological uncertainties as well as the feasibility of improving further the accuracy of this experiment.Received: 31 July 2004, Published online: 7 March 2005PACS:
03.65, 28.20
Correspondence to: V. Nesvizhevsky 相似文献
8.
Bioengineered crops represent an important advancement for farmers who want to avoid losses caused by insect infestations or adverse environmental conditions. However, the use of modern biotechnology has raised questions regarding the safety of bioengineered foods because of the potential allergenicity of proteins expressed by the newly introduced genes. Standard approaches for safety assessment of these foods are still evolving. Animal models have been suggested as a tool that could help evaluate the potential allergenicity of such compounds. Several investigators are developing animal models to evaluate novel proteins, but none of these have yet been validated. This article reviews the published murine models, rat and mouse in particular, and the different methods used to evaluate parameters related to allergy. It also addresses the factors involved in the development of a model. Finally, it raises some questions that should be considered by the international community so that financial and intellectual efforts can be addressed in a unified manner. 相似文献
9.
C. Westphal 《Applied Physics A: Materials Science & Processing》2003,76(5):721-730
Angle- and energy-scanned photoelectron diffraction data can be used to investigate structures below surfaces. The modulations
in photoelectron intensity result from diffraction of the emitted electron wave at neighbor atoms. In the past, scanned-energy
photoelectron diffraction had been mainly used to determine the adsorption site of molecules at surfaces. Recent data show,
however, that the technique can also be employed to obtain information about the upper substrate layer(s). At low kinetic
energies, backward scattering is strong and in scanned-angle photoelectron diffraction the recorded patterns result from backward-
and multiple-scattering effects. For a structural analysis, the intensity modulations have to be compared with the results
for simulations performed for model clusters. As an example, recent angle-scanned photoelectron diffraction patterns recorded
for the technologically important silicon oxide/silicon interface were compared with simulations. At the Si(001) surface orientation,
the interface is extended over a few layers, whereas at the Si(111) surface orientation the transition is rather abrupt and
occurs within one or two layers.
Received: 9 September 2002 / Accepted: 2 October 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +49-231/755-3657, E-mail: carsten.westphal@physik.uni-dortmund.de 相似文献
10.
Local environments of Si suboxides at the interface between a thermally grown SiO2 film and Si(111) were studied by angle-scanned photoelectron diffraction. Si 2p core-level spectra containing chemically shifted components were recorded. The components were deconvoluted by least squares fitting and assigned to different Si oxidation states. The obtained diffraction patterns of the various suboxides exhibit different features. Comparison of these patterns with multiple scattering calculations including a multipole R-factor analysis shows that a simple chemical abrupt interface model describes well the environment of the suboxides and indicates ordered SiO2 close to the interface. 相似文献