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111.
Sherrod L. Maxwell Brian K. Culligan Jay B. Hutchison 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1891-1901
A new rapid method for the determination of actinides in asphalt samples has been developed that can be used in emergency response situations or for routine analysis. If a radiological dispersive device, improvised nuclear device or a nuclear accident such as the accident at the Fukushima Nuclear Power Plant in March, 2011 occurs, there will be an urgent need for rapid analyses of many different environmental matrices, including asphalt materials, to support dose mitigation and environmental clean-up. The new method for the determination of actinides in asphalt utilizes a rapid furnace step to destroy bitumen and organics present in the asphalt and sodium hydroxide fusion to digest the remaining sample. Sample preconcentration steps are used to collect the actinides and a new stacked TRU Resin + DGA Resin column method is employed to separate the actinide isotopes in the asphalt samples. The TRU Resin plus DGA Resin separation approach, which allows sequential separation of plutonium, uranium, americium and curium isotopes in asphalt samples, can be applied to soil samples as well. 相似文献
112.
The first total synthesis of eutypoid A and a new synthesis of racemic microperfuranone and gymnoascolide A have been achieved. The key steps in our synthetic strategy involve a Suzuki coupling reaction to install the C3 aryl ring and a Mannich-type reaction for the construction of the 4-benzylbutenolide core. 相似文献
113.
Kenji Hirai Rie Takeda James A. Hutchison Hiroshi Uji‐i 《Angewandte Chemie (International ed. in English)》2020,59(13):5332-5335
Light‐molecule strong coupling has emerged within the last decade as a new method to control chemical reactions. A few years ago it was discovered that chemical reactivity could be altered by vibrational strong coupling (VSC). Only a limited number of reactions have been investigated under VSC to date, including solvolysis and deprotection reactions. Here the effect of VSC on a series of aldehydes and ketones undergoing Prins cyclization, an important synthetic step in pharmaceutical chemistry, is investigated. A decrease of the second‐order rate constant with VSC of the reactant carbonyl stretching groups is observed. We also observe an increased activation energy due to VSC, but proportional changes in activation enthalpy and entropy, suggesting no substantive change in reaction pathway. The addition of common cycloaddition reactions to the stable of VSC‐modified chemical reactions is another step towards establishing VSC as a genuine tool for synthetic chemistry. 相似文献
114.
115.
N. Yazidjoglou W. D. Hutchison H. R. Foster G. A. Stewart D. H. Chaplin 《Hyperfine Interactions》1992,75(1-4):283-290
Precision NMRON field shift studies have been carried out up to 8T on a54MnNi single crystal along a hard [100] direction and on a125SbFe single crystal along a hard [110] direction. For both systems, high field (B
app>-1T) and low field (0.3T<B
app<0.8T) data sets are obtained. The analysis reveals a significant discrepancy between the apparent Knight Shift dependent
on whether the low field or high field data set is utilised. For both systems, consideration of the high field data sets yield
a zero Knight Shift K(54MnNi)=+0.0(0.2)% and K(125SbFe)=+0.2(1.4)%, whereas the low field data sets yield K(54MnNi)=+7.5(3.9)% and K(125SbFe)=−5.4(3.3)% respectively. The field range dependence of K suggests that only Knight shifts measured in large fields (>-1T)
are meaningful for establishing systematics. This casts some doubt on the greater bulk of the literature’s NMRON Knight shift
studies, where predominantly low fields have been used to determine K. 相似文献
116.
A novel technique involving electrodeposition has been used to prepare an elemental silver specimen wherein radioactive110mAg probe nuclei are confined to a surface layer of approximately 0.1 μm depth. This specimen was then brute force oriented
in a field of 8T and the continuous wave (CW) nuclear magnetic resonance on oriented nuclei (NMRON) spectrum showed an integrated
destruction of some 58%. Moreover the transient NMRON techniques of single and modulated adiabatic passage were successfully
applied, resulting in a determination of the electric quadrupole interaction strength at the110mAg site in polycrystalline silver of P/h=+0.74(5)kHz with a FWHM of ΔP/h=0.75(8)kHz. The resulting mode electric field gradient
is Vzz=+1.87(23)×1018Vm−1. Analysis of the single passage data provides an estimate for the nuclear spin lattice relaxation constant in silver at 8T
of Ck=1.6(3)s.K. 相似文献
117.
Mark T McAuley Rose Anne Kenny Thomas BL Kirkwood Darren J Wilkinson Janette JL Jones Veronica M Miller 《BMC neuroscience》2009,10(1):26
Background
The hippocampus is essential for declarative memory synthesis and is a core pathological substrate for Alzheimer's disease (AD), the most common aging-related dementing disease. Acute increases in plasma cortisol are associated with transient hippocampal inhibition and retrograde amnesia, while chronic cortisol elevation is associated with hippocampal atrophy. Thus, cortisol levels could be monitored and managed in older people, to decrease their risk of AD type hippocampal dysfunction. We generated an in silicomodel of the chronic effects of elevated plasma cortisol on hippocampal activity and atrophy, using the systems biology mark-up language (SBML). We further challenged the model with biologically based interventions to ascertain if cortisol associated hippocampal dysfunction could be abrogated. 相似文献118.
119.
Davies GR Lurie DJ Hutchison JM McCallum SJ Nicholson I 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,148(2):289-297
There is growing interest in the use of magnetic resonance imaging (MRI) to examine solid materials where the restricted motion of the probed spins leads to broad lines and short T(2) values, rendering many interesting systems invisible to conventional 2DFT pulsed imaging methods. In EPR T(2) seldom exceeds 0.1 mus and continuous-wave methods are adopted for spectroscopy and imaging. In this paper we demonstrate the use of continuous-wave MRI to obtain 2-dimensional images of short T(2) samples. The prototype system can image samples up to 50 mm in diameter by 60 mm long and has been used to image polymers and water penetration in porous media. Typical acquisition times range between 10 and 40 min. Resolution of 1 to 2 mm has been achieved for samples with T(2) values ranging from 38 to 750 mus. There is the possibility of producing image contrast that is determined by the material properties of the sample. 相似文献
120.