全文获取类型
收费全文 | 99篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 75篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 12篇 |
物理学 | 15篇 |
出版年
2024年 | 1篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有105条查询结果,搜索用时 31 毫秒
1.
In this paper we show the existence of a solution, on any time intervals, in suitable Sobolev spaces for the 2D compressible
Euler equation in the exterior domain, when the Mach number is sufficiently small. We shall extend results obtained in [8]
in the case of an infinity velocity different from zero.
Sunto In questo lavoro proviamo l'esistenza di una soluzione, su ogni intervallo temporale, in opportuni spazi di Sobolev per le equazioni di Eulero 2D comprimibili in un dominio esterno, quando il numero di Mach è sufficientemente piccolo. Estenderemo i risultati ottenuti in [8] al caso di velocità all'infinito diversa da zero.相似文献
2.
3.
R. A. Dewberry S. R. Salaymeh V. R. Casella F. S. Moore 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(3):515-531
Summary This paper contains a summary of the holdup and material control and accountability (MC&A) assays conducted for the determination
of highly enriched uranium (HEU) in the deactivation and decommissioning (D&D) of the Reactor Fuel Fabrication Facility at
the Savannah River Site (SRS). The facility was used to fabricate HEU fuel assemblies, lithium-aluminum target tubes, neptunium
assemblies, and miscellaneous components for the SRS production reactors. The facility operated for more than 35 years. During
this time thousands of uranium-aluminum alloy (U-Al) production reactor fuel tubes were produced. After the facility ceased
operations in 1995, all of the easily accessible U-Al was removed from the building, and only residual amounts remained. The
bulk of this residue was located in the equipment that generated and handled small U-Al particles and in the exhaust systems
for this equipment (e.g., chip compactor, casting furnaces, log saw, lathes A & B, cyclone separator, Freon?cart, riser crusher,
…, etc). The D&D project is likely to represent an important example for D&D activities across SRS and across the Department
of Energy weapons complex. The Savannah River National Laboratory was tasked to conduct holdup assays to quantify the amount
of HEU on all components removed from the facility prior to placing in solid waste containers. The 235U holdup in any single component of process equipment must not exceed 50 g in order to meet the container limit. This limit
was imposed to meet criticality requirements of the low level solid waste storage vaults. Thus, the holdup measurements were
used as guidance to determine if further decontamination of equipment was needed to ensure that the quantity of 235U did not exceed the 50 g limit and to ensure that the waste met the Waste Acceptance Criteria (WAC) of the solid waste storage
vaults. Since HEU is an accountable nuclear material, the holdupassays and assays of recovered residue were also important
for material control and accountability purposes. In summary, the results of the holdup assays were essential for determining
compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to ensure that administrative criticality
safety controls were not exceeded. This paper discusses theg-ray assay measurements conducted and the modeling of the acquired
data to obtain measured holdup in process equipment, exhaust components, and fixed geometry scrap cans. It also presents development
work required to model new acquisition configurations and to adapt available instrumentation to perform the assays. 相似文献
4.
A nickel-catalysed chemically modified electrode is described which seems to represent a convenient compromise between ease of preparation, reproducibility, precision and detection limits for the determination of carbohydrates in biological matrices. 相似文献
5.
Casella L Monzani E Fantucci P Gullotti M De Gioia L Strini A Chillemi F 《Inorganic chemistry》1996,35(2):439-444
The effect of strain in the axial coordination of imidazole to the heme has been studied in the chelate complexes deuterohemin-histidine (DH-His) and deuterohemin-alanylhistidine (DH-AlaHis). Molecular mechanics calculations indicate that three types of distortion of the axial ligand occur in DH-His, due to the relatively short length of the arm carrying the donor group: tilting off-axis, tipping, and inclination of the imidazole plane with respect to the axial Fe-N bond. The effects of tilting (Deltagamma approximately 10 degrees ) and inclination of the imidazole ring (Deltadelta approximately 17 degrees ) are dominant, while tipping is small and is probably of little importance here. By contrast, the axial imidazole coordination is normal in DH-AlaHis and other computed deuterohemin-dipeptide or -tripeptide complexes where histidine is the terminal residue, the only exception being DH-ProHis, where the rigidity of the proline ring reduces the flexibility of the chelating arm. The distortion in the axial iron-imidazole bond in DH-His has profound and negative influence on the binding and catalytic properties of this complex compared to DH-AlaHis. The former complex binds more weakly carbon monoxide, in its reduced form, and imidazole, in its oxidized form, than the latter. The catalytic efficiency in peroxidative oxidations is also reduced in DH-His with respect to DH-AlaHis. The activity of the latter complex is similar to that of microperoxidase-11, the peptide fragment incorporating the heme that results from hydrolytic cleavage of cytochrome c. 相似文献
6.
A cobalt oxyhydroxide film dispersed on a carbon electrode surface was characterized and proposed as an amperometric sensor for determination of alditols and carbohydrates in flowing streams. Complex mixtures of carbohydrates were separated by anion-exchange chromatography using a moderately alkaline solution as mobile phase. The cobalt modified electrode (GC-Co) was employed under a constant applied potential of 0.5 V (vs Ag/AgCl). Under these experimental conditions the detection limits (S/N=3) for all analyzed electroactive molecules ranged between 0.3 micromol L(-1) and 1.5 micromol L(-1) and the dynamic linear ranges spanned generally three orders of magnitude above the relevant detection limits. Analytical determinations of carbohydrates and alditols in red and white wines, are reported. 相似文献
7.
The effect of nitrite in the sulfoxidation of organic sulfides catalyzed by myoglobin (Mb) in the presence of hydrogen peroxide has been investigated. A general improvement in enantioselectivity was found for the reaction catalyzed by horse heart metMb and a series of sperm whale metMb derivatives including the wild type protein, the active site mutants T67K Mb, T67R Mb, T67R/S92D Mb, and the T67K Mb derivative reconstituted with the modified prosthetic group protohemin-l- histidine methyl ester. 相似文献
8.
An electrochemical detection method for short-chain saturated and unsaturated aliphatic aldehydes separated by liquid chromatography in moderately acidic medium is described. A triple-step waveform of the potentials applied to the polycrystalline platinum electrode, is proposed for sensitive detection of aliphatic aldehydes in flowing streams avoiding tedious pre- or post-column derivatization and/or cleanup procedures. The influences of the perchloric acid concentration and dissolved oxygen in the mobile phase, on the amperometric and chromatographic performance were evaluated and considered in terms of sensitivity and selectivity. Under the optimised experimental conditions (i.e., deoxygenated 50mM HClO4) the proposed analytical method allowed detection limits between 0.2 microM for acrolein and 2.5 microM for valeraldehyde. Regression analysis of calibration data indicates that responses for all investigated compounds are linear over about 2 orders of magnitude above the LOD, with correlation coefficients >0.990. The method was successfully applied to the determination of formaldehyde, acetaldehyde, propionaldehyde and acrolein in real matrices such as spiked water and red wines with good mean recoveries (81-97%). 相似文献
9.
A Non‐Enzymatic Carbohydrate Sensor Based on Multiwalled Carbon Nanotubes Modified with Adsorbed Active Gold Particles
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The voltammetric behavior of a glassy carbon electrode modified with multiwalled carbon nanotubes (MWCNTs) and Au particles was studied in alkaline medium towards the electrooxidation of some carbohydrates used as model compounds. The influence of carbohydrate concentration and scan rate on peak potentials, peak currents, etc., observed at the modified electrode was evaluated and critically discussed. The Au particles dispersed into multiwalled carbon nanotubes structures showed favorable electrocatalytic and analytical properties towards the electrooxidation of xylose and glucose molecules. Atomic force microscopy performed on the resulting modified electrode showed a well‐efficient 3D distribution of Au active particles having sharp‐edged and elongated grains along bundles of the MWCNTs. The three‐dimensional MWCNT‐Au composite structure of the catalyst act as a promoter to enhance the diffusive character of recorded currents and probably also increases the rate of the heterogeneous electron transfer of the electrooxidation process considered. 相似文献
10.
Bruno Casella Gareth Roberts Osnat Stramer 《Methodology and Computing in Applied Probability》2011,13(4):835-854
A broad class of implicit or partially implicit time discretizations for the Langevin diffusion are considered and used as
proposals for the Metropolis–Hastings algorithm. Ergodic properties of our proposed schemes are studied. We show that introducing
implicitness in the discretization leads to a process that often inherits the convergence rate of the continuous time process.
These contrast with the behavior of the naive or Euler–Maruyama discretization, which can behave badly even in simple cases.
We also show that our proposed chains, when used as proposals for the Metropolis–Hastings algorithm, preserve geometric ergodicity
of their implicit Langevin schemes and thus behave better than the local linearization of the Langevin diffusion. We illustrate
the behavior of our proposed schemes with examples. Our results are described in detail in one dimension only, although extensions
to higher dimensions are also described and illustrated. 相似文献