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排序方式: 共有69条查询结果,搜索用时 15 毫秒
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Erik J. Faber Dr. Wouter Sparreboom Wilrike Groeneveld Louis C. P. M. de Smet Dr. Johan Bomer Wouter Olthuis Dr. Han Zuilhof Dr. Ernst J. R. Sudhölter Prof. Piet Bergveld Prof. Albert van den Berg Prof. 《Chemphyschem》2007,8(1):101-112
The electrochemical behavior of Si--C linked organic monolayers is studied in electrolyte-insulator-Si devices, under conditions normally encountered in potentiometric biosensors, to gain fundamental knowledge on the behavior of such Si electrodes under practical conditions. This is done via titration experiments, Mott-Schottky data analysis, and data fitting using a site-binding model. The results are compared with those of native SiO(2) layers and native SiO(2) layers modified with hexamethyldisilazane. All samples display pH sensitivity. The number of Si--OH groups on the alkylated samples is calculated to be less than 0.7 % of that of a pure SiO(2) insulator, which still causes a pH sensitivity of approximately 25 mV per pH unit in the pH range: 4-7. The alkylated samples hardly suffer from response changes during up- and down-going titrations, which indicates that very little oxide is additionally formed during the measurements. The pK(a) values of all samples with monolayers (4.0-4.4) are lower than that of native SiO(2) (6.0). The long-term drift (of approximately 1 mV h(-1)) is moderate. The results indicate that biosensors composed of alkylated Si substrates are feasible if a cross-sensitivity towards pH in the sensor signal is taken into account. 相似文献
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R. P. H. Garten K. O. Groeneveld und K. -H. König 《Fresenius' Journal of Analytical Chemistry》1977,288(3):171-179
Zusammenfassung Zum Vergleich der Leistungsfähigkeit von zerstörungsfreien Verfahren der Rastermikroanalyse wurden Lanthanoiden-Standardproben für die energiedispersive Röntgenspektralanalyse auf der Basis von synthetischem Ca-Al-Silicat-Glas mit je 3–5 Lanthanoidenelementen (3–4 Gew.-%) hergestellt. Mit protoneninduzierter Röntgenspektralanalyse wurden bei einer Analysenzeit von 60 s Nachweisgrenzen von 100–400 g/g an diesen dicken Proben bestimmt. Diese Nachweisgrenzen sind um den Faktor 2 bis 15 günstiger als die unter vergleichbaren Bedingungen mit wellenlängendispersiver Elektronenmikroanalyse bestimmten Nachweisgrenzen. Messungen mit energiedispersiver Röntgenspektranalyse am Rasterelektronenmikroskop zeigen, daß die Protonenanregung gegenüber der Elektronenanregung an diesen dicken Proben ein um den Faktor 20 besseres Signal/Untergrund-Verhältnis liefert.Wir danken der Deutschen Forschungsgemeinschaft für die Gewährung von Sach- und Personalmitteln für die Durchführung dieser Arbeit. 相似文献
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Tobias G. Brevé Mike Filius Sven Weerdenburg Stefan J. van der Griend Tim P. Groeneveld Dr. Antonia G. Denkova Dr. Rienk Eelkema 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(10):e202103523
Stimuli-responsive soft materials enable controlled release of loaded drug molecules and biomolecules. Controlled release of potent chemotherapeutic or immunotherapeutic agents is crucial to reduce unwanted side effects. In an effort to develop controlled release strategies that can be triggered by using Cerenkov luminescence, we have developed polymer hydrogels that can release bovine serum albumin and immunoglobulin G by using light (254 nm–375 nm) as a trigger. We describe the synthesis and photochemical characterization of two light sensitive phenacyl bis-azide crosslinkers that are used to prepare transparent self-supporting hydrogel patches. One crosslinker was designed to optimize the overlap with the Cerenkov luminescence emission window, bearing an π-extended phenacyl core, resulting in a high quantum yield (14 %) of photocleavage when irradiated with 375 nm light. We used the extended phenacyl crosslinker for the preparation of protein-loaded dextran hydrogel patches, which showed efficient and selective dosed release of bovine serum albumin or immunoglobulin G after irradiation with 375 nm light. Cerenkov-triggered release is as yet inconclusive due to unexpected side-reactivity. Based on the high quantum yield, efficient release and large overlap with the Cerenkov window, we envision application of these photosensitive soft materials in radiation targeted drug release. 相似文献
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McCormack DA Kroes GJ Olsen RA Groeneveld JA van Stralen JN Baerends EJ Mowrey RC 《Faraday discussions》2000,(117):109-32; discussion 161-89
We perform six-dimensional (6D) quantum wavepacket calculations for H2 dissociatively adsorbing on Cu(100) from a variety of rovibrational initial states. The calculations are performed on a new potential energy surface (PES), the construction of which is also detailed. Reaction probabilities are in good agreement with experimental findings. Using a new flux analysis method, we calculate the reaction probability density as a function of surface site and collision energy, for a variety of initial states. This approach is used to study the effects of rotation and vibration on reaction at specific surface sites. The results are explained in terms of characteristics of the PES and intrinsically dynamic effects. An important observation is that, even at low collision energies, reaction does not necessarily proceed predominantly in the region of the minimum potential barrier, but can occur almost exclusively at a site with a higher barrier. This suggests that experimental control of initial conditions could be used to selectively induce reaction at particular surface sites. Our predictions for site-reactivity could be tested using contemporary experimental methods: The calculations predict that, for reacting molecules, there will be a dependence of the quadrupole alignment of j on the incident vibrational state, v. This is a direct result of PES topography in the vicinity of the preferred reaction sites of v = 0 and v = 1 molecules. Invoking detailed balance, evidence for this difference in preferred reaction site of v = 0 and 1 molecules could be obtained through associative desorption experiments. 相似文献
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R. P. H. Garten G. Schneeweis B. Steinbrech K. -H. König und K. O. Groeneveld 《Fresenius' Journal of Analytical Chemistry》1982,313(3):193-199
Zusammenfassung Die Elementanalyse wäßriger Lösungen und ihrer Konzentrate mit protoneninduzierter Röntgen-emissionsspektroskopie (PIXE) wird durch Vorschalten der Dünnschicht-Chromatographie (DC) als Trennschritt in ihrer Leistungsfähigkeit wesentlich gesteigert. Spektrale Überlagerungen können durch die Vortrennung in Elementgruppen beseitigt werden, wobei als spezifischer Vorteil die Möglichkeit der ortsaufgelösten Rasteranalyse mit PIXE gezielt genutzt wird. Die Vorteile mit der Kombination DC + PIXE werden am Beispiel von Chelatkomplexen der 8. Nebengruppe untersucht. Die Eichung mit Verdünnungsreihen und die Korrektur der PIXE-Signalintensität, die von den chromatographischen Laufstrecken abhängig ist, führen zu einem quantitativen Verfahren für die Simultanbestimmung von Nebengruppenelementen mit Absolutmengen im Nanogrammbereich. Der zusätzliche Aufwand für die Vortrennung mit DC vor der PIXE-Analyse ist vernachlässigbar.
Combination of Thin-Layer Chromatography (TLC) and Proton Induced X-ray Emission (PIXE) for elemental analysis of solutions
Summary Proton Induced X-ray Emission (PIXE) analysis is relatively widely used in the analysis of water and metal ion preconcentration preparations from water samples. In this field the efficiency of PIXE is strongly enhanced by taking advantage of the Thin-Layer Chromatography (TLC) as a separation step prior the PIXE.Spectral interferences from multielement samples are overcome by the TLC group-separation following chemical aspects. The potentials of the locally resolved and scanned PIXE analysis are employed gaining specific advantages in multielement analysis. The benefits of the combined TLC-PIXE technique are exemplified on some metal chelates of the 8th auxiliary group.A quantitative determination procedure is established for the simultaneous analysis of auxiliary group elements of absolute amounts within the nanogramme-range by calibration using series of graduated dilution and by correction for the dependence of the PIXE-signal intensity on the chromatographic migration length. The additional effort concerning the preseparation by TLC prior to PIXE is negligible.相似文献
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J. Schader R. Latz M. Burkhard H. J. Frischkorn D. Hofmann P. Koschar K. O. Groeneveld D. Berényi A. Kövér Gy. Szabó 《Il Nuovo Cimento D》1986,7(2):219-240
Summary Absolute double differential cross-sections for target ionization and projectile electron loss were determined in collisions
of H+, H2
+,3He+ and3He++ ions (0.4 to 2.0 Me V/u) with He and Ar gas targets at electron emission angles from 0° up to 60°. The experimental results
are qualitatively well described by plane-wave Born approximations including screening of the projectile in target ionization
and of the target atom in the case of electron loss.
Riassunto Sono state determinate le sezioni d’urto doppie differenziali assolute per la ionizzazione del bersaglio e la perdita dell’elettrone proiettile in collisioni di ioni H+, H 2 + ,3He+ e3He++ (da 0.4 a 2.0 Me V/u) con bersagli di gas He e Ar ad angoli di emissione degli elettroni da 0° a 60°. I risultati sperimentali sono qualitativamente ben descritti dalle approssimazioni di Born per onde piane che comprendono la schermatura del proiettile nella ionizzazione del bersaglio e dell’atomo bersaglio nel caso di perdita dell’elettrone.
Резюме Определяются абсолютные дважды дифференшиальные поперечные сечения для ионизации мишени и потери электровов налетающими частишами при соударениях ионов H+, H 2 + ,3He+ и3He++ (от 0.4 до 2.0 Me V/u) в случае газовых Не и Ar мишеней при углах эмиссии электронов от 0° до 60°. Экспериментальные результаты качественно хорощо описываются с помощью плоско-волнового борновского приближения, включая экранирование налетающей частицы при ионизации мишени в случае потери электрона.相似文献
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Summary A short introduction into the phenomenon of kinetic ioninduced secondary electron emission from solids is given. The basic
features of proton-induced secondary electron spectra from thin foils in forward-(beam-) direction are briefly discussed.
Summarium Post brevem introductionem in phaenomenon emissionis cineticae electroniorum secundariorum ioniis inductae e corporibus solidis structurae praevalentes spectrorum energiae electroniorum secundariorum ex foliis tenibus protoniis inductorum prorsus rectorum, id est in directionem radii, proponuntur.相似文献