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81.
82.
E. Bateman 《Fresenius' Journal of Analytical Chemistry》1916,55(4):211-213
Ohne Zusammenfassung 相似文献
83.
Kevin P. Bateman Markus Kellmann Helmut Muenster Robert Papp Lester Taylor 《Journal of the American Society for Mass Spectrometry》2009,20(8):1441-1450
Current approaches to discovery-stage drug metabolism studies (pharmacokinetics, microsomal stability, etc. ) typically use
triple-quadrupole-based approaches for quantitative analysis. This necessitates the optimization of parameters such as Q1
and Q3 m/z values, collision energy, and interface voltages. These studies detect only the specified compound and information about
other components, such as metabolites, is lost. The ability to perform full-scan acquisition for quantitative analysis would
eliminate the need for compound optimization while enabling the detection of metabolites and other non-drug-related endogenous
components. Such an instrument would have to provide sensitivity, selectivity, dynamic range, and scan speed suitable for
discovery-stage quantitative studies. In this study, a prototype benchtop Orbitrap-based mass analyzer was used to collect
both quantitative and qualitative data from human microsomal incubation samples as well as rat plasma from pharmacokinetic
studies. Instrumental parameters such as scan speed, resolution, and mass accuracy are discussed in relation to the requirements
for a quantitative-qualitative workflow. The ability to perform highly selective quantitative analysis while simultaneously
characterizing metabolites from both in vitro and in vivo studies is discussed. 相似文献
84.
Lewin M Guilhaus M Wildgoose J Hoyes J Bateman B 《Rapid communications in mass spectrometry : RCM》2002,16(6):609-615
Ions experience small deflections in the vicinity of grids in accelerators and ion mirrors in time-of-flight (TOF) mass spectrometers. Recent experiments with an orthogonal acceleration (oa) TOF instrument have verified that the effect can significantly degrade resolution when ions approach grids at an angle deviating from 90 degrees. The phenomenon becomes significant only when ions have components of velocity at right angles to the wires of the grids. A model is presented in this study to predict this phenomenon for parallel wire grids. The fractional energy spread of ions (calculated in the static TOF-spectrometer frame of reference) scales directly with the approach angle of ions to the grid (as measured from normal approach). The energy spread also scales with the range of angles that is a consequence of the focusing effect in each gap between the wires of the grid. The equations imply that closely spaced parallel wire grids are best for deployment in oa-TOF systems where non-zero approach angles are unavoidable. Such grids are relatively impractical to manufacture and support but rectangular repeat cell grids with relatively few wires at right angles to the source axis are shown experimentally to introduce minimal energy spread. When these grids are rotated by 90 degrees, the resolution measured in a Q-TOF spectrometer is degraded in approximate agreement with the parallel wire model. A practical implication of this work is that grid transmissions in oa-TOF systems may be significantly increased without loss of resolution. Improvements of approximately 200% (V-mode) and approximately 400% (W-mode) in ion transmission were obtained in this study without compromising resolution. This was achieved with approximately 73% transmission grids and greater potential improvements in transmission are being realised since this study with approximately 89% transmission grids having similar geometry. 相似文献
85.
86.
Pascal Demange Andrew Bateman John K. Macleod Anne Dell Mohamed A. Abdallah 《Tetrahedron letters》1990,31(52):7611-7614
Two unusual natural amino acids have been identified in the pyoverdins occurring from two different strains ofPseudomonas fluorescens. They contain a 3,4,5,6-tetrahydropyrimidine moiety resulting from the condensation of 2,4-diaminobutyric acid with the car☐yl group of respectively serine and glutamine. 相似文献
87.
The set S consisting of those positive integers n which are uniquely expressible in the form n = a2 + b2 + c2, , is considered. Since n ∈ S if and only if 4n ∈ S, we may restrict attention to those n not divisible by 4. Classical formulas and the theorem that there are only finitely many imaginary quadratic fields with given class number imply that there are only finitely many n ∈ S with n = 0 (mod 4). More specifically, from the existing knowledge of all the imaginary quadratic fields with odd discriminant and class number 1 or 2 it is readily deduced that there are precisely twelve positive integers n such that n ∈ S and n ≡ 3 (mod 8). To determine those n ∈ S such that n ≡ 1, 2, 5, 6 (mod 8) requires the determination of the imaginary quadratic fields with even discriminant and class number 1, 2, or 4. While the latter information is known empirically, it has not been proved that the known list of 33 such fields is complete. If it is complete, then our arguments show that there are exactly 21 positive integers n such that n ∈ S and n ≡ 1, 2, 5, 6 (mod 8). 相似文献
88.
Fertilizer nitrogen isotope signatures 总被引:5,自引:0,他引:5
There has been considerable recent interest in the potential application of nitrogen isotope analysis in discriminating between organically and conventionally grown crops. A prerequisite of this approach is that there is a difference in the nitrogen isotope compositions of the fertilizers used in organic and conventional agriculture. We report new measurements of delta15N values for synthetic nitrogen fertilizers and present a compilation of the new data with existing literature nitrogen isotope data. Nitrogen isotope values for fertilizers that may be permitted in organic cultivation systems are also reported (manures, composts, bloodmeal, bonemeal, hoof and horn, fishmeal and seaweed based fertilizers). The delta15N values of the synthetic fertilizers in the compiled dataset fall within a narrow range close to 0 per thousand with 80% of samples lying between-2 and 2 per thousand and 98.5% of the data having delta15N values of less than 4 per thousand (mean=0.2 per thousand n=153). The fertilizers that may be permitted in organic systems have a higher mean delta15N value of 8.5 per thousand and exhibit a broader range in delta15N values from 0.6 to 36.7 per thousand (n=83). The possible application of the nitrogen isotope approach in discriminating between organically and conventionally grown crops is discussed in light of the fertilizer data presented here and with regard to other factors that are also important in determining crop nitrogen isotope values. 相似文献