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91.
92.
Chen LJ Shah SS Silangcruz J Eller MJ Verkhoturov SV Revzin A Schweikert EA 《International journal of mass spectrometry》2011,303(2-3):97-102
Cluster C(60) ToF-SIMS (time-of-flight secondary ion mass spectrometry) operated in the event-by-event bombardment-detection method has been applied to: a) quantify the binding density of Au nanoparticles (AuNPs)-antiCD4 conjugates on the cell surface; b) identify the binding sites between AuNPs and antibody. Briefly, our method consists of recording the secondary ions, SIs, individually emitted from a single C(60) (1,2+) impact. From the cumulative mass spectral data we selected events where a specific SI was detected. The selected records revealed the SIs co-ejected from the nanovolume impacted by an individual C(60) with an emission area of ~ 10nm in diameter as an emission depth of 5-10 nm. The fractional coverage is obtained as the ratio of the effective number of projectile impacts on a specified sampling area (N(e)) to the total number of impacts (N(0)). In the negative ion mass spectrum, the palmitate (C(16)H(31)O(2) (-)) and oletate (C(18)H(33)O(2) (-)) fatty acid ions present signals from lipid membrane of the cells. The signals at m/z 197 (Au(-)) and 223 (AuCN(-)) originate from the AuNPs labeled antibodies (antiCD4) bound to the cell surface antigens. The characteristic amino acid ions validate the presence of antiCD4. A coincidence mass spectrum extracted with ion at m/z 223 (AuCN(-)) reveals the presence of cysteine at m/z 120, documenting the closeness of cysteine and the AuNP. Their proximity suggests that the binding site for AuNP on the antibody is the sulfur-terminal cysteine. The fractional coverage of membrane lipid was determined to be ~23% of the cell surfaces while the AuNPs was found to be ~21%. The novel method can be implemented on smaller size NPs, it should thus be applicable for studies on size dependent binding of NP-antibody conjugates. 相似文献
93.
Samad N. Ebrahimi Frank Gafner Giorgio Dell'Acqua Kuno Schweikert Matthias Hamburger 《Helvetica chimica acta》2011,94(1):38-45
Phytochemical profiling of a MeOH extract from Haberlea rhodopensis by a combination of liquid/liquid extraction, and preparative and semi‐preparative HPLC afforded three new flavone C‐glycosides, hispidulin‐8‐C‐(2″‐O‐syringoyl)‐β‐glucopyranoside ( 3 ), hispidulin 8‐C‐(6‐O‐acetyl‐β‐glucopyranoside) ( 4 ), and hispidulin 8‐C‐(6‐O‐acetyl‐2‐O‐syringoyl‐β‐glucopyranoside) ( 5 ), along with two known phenolic glycosides, myconoside ( 1 ) and paucifloside ( 2 ). The structures were established by extensive spectroscopic analyses including 1D‐ and 2D‐NMR (COSY, HSQC, and HMBC), and HR‐ESI‐TOF‐MS, and by comparison with published data. 相似文献
94.
A. N. McGinley E. A. Schweikert 《Journal of Radioanalytical and Nuclear Chemistry》1979,52(1):101-110
Procedures for instrumental neutron activation analysis have been developed and used on flint samples collected from the Edwards
Formation in Texas. Each of the samples was analyzed for Mn, Ca, V, Al, Sc, Co, Fe, As, and K. USGS standard rocks AUG-1,
GSP-1, and G-2 were also analyzed in order to test the reliability of this technique. Means and standard deviations of each
element determined were calculated. The elemental values ranged from 0.03 ppm for scandium to 1500 ppm for aluminium. Based
on relative elemental abundances, the rocks could be classified into two types of flint. This information suggests elemental
inhomogeneity in the Edwards Formation. 相似文献
95.
G. Gauglitz S. Krebs M. Reichert H. J. Roth R. Schubert und L. Schweikert 《Fresenius' Journal of Analytical Chemistry》1988,330(4-5):406-407
Ohne Zusammenfassung
Kinetic examinations of pharma-lipid-interactions by measurements of absorbance of dispersed material相似文献
96.
A. Q. Sanni N. G. Roché H. J. Dowell E. A. Schweikert T. H. Ramsey 《Journal of Radioanalytical and Nuclear Chemistry》1984,81(1):125-129
Carbon and oxygen impurities in silicon have been determined by 7.00 MeV3He activation analysis. The detection limits obtained for interference-free conditions are 0.1 ppb (wt) for carbon and 1.0 ppb (wt) for oxygen in silicon. 相似文献
97.
R. L. Betts M. A. Park E. Lynn Shirey E. A. Schweikert 《Journal of mass spectrometry : JMS》1994,29(11):679-683
The plasma desorption of hydrogen loss fragment ions from frozen films of several classes of aliphatic volatile hydrocarbons was investigated with 252Cf plasma desorption mass spectrometry. A time-of-flight instrument suitable for the reproducible sampling and analysis of volatile hydrocarbons in the solid state was designed for this study. Representative compounds from the n-alkanes and cycloalkanes were analyzed. For all the compounds studied, radical molecular ions. M+., and hydrogen loss fragment ions, [M ? mH]+ with m varying from 1 to 10, were produced. The length of the alkane chain, the size of the alkane rings and the stability of the resulting H-loss ions affected the number and abundance of these ions. Smaller molecules underwent proportionally more hydrogen loss than larger molecules of the same class. 相似文献
98.
J. B. Shapiro W. D. James E. A. Schweikert 《Journal of Radioanalytical and Nuclear Chemistry》1995,192(2):275-280
Fast neutron activation analysis (FNAA) was investigated as a possible on-site preliminary screening technique for metal contamination of soil. Two metals, Cu and Zn, were used in a laboratory setting to evaluate the possibility of detecting metal contamination of soil at or below the maximum permissible metal concentration in soil. Varying quantities of compounds of the selected metals were mixed into a prepared soil column for analysis of signal intensity as a function of concentration in the soil. Experiments were conducted with a sealed tube neutron generator and a germanium gamma-ray detector. Both metals produced signal levels distinguishable from background soil concentrations at the maximum permissible level. 相似文献
99.
Chen LJ Shah SS Verkhoturov SV Revzin A Schweikert EA 《Surface and interface analysis : SIA》2011,43(1-2):555-558
Micropatterning is used widely in biosensor development, tissue engineering and basic biology. Creation of biological micropatterns typically involves multiple sequential steps that may lead to cross-contamination and may contribute to sub-optimal performance of the surface. Therefore, there is a need to develop novel strategies for characterizing location-specific chemical composition of biological micropatterns. In this paper, C(60) (+) ToF-SIMS operating in the event-by-event bombardment-detection mode was used for spatially resolved chemical analysis of micropatterned indium tin oxide (ITO) surfaces. Fabrication of the micropatterns involved multiple steps including self-assembly of poly (ethylene glycol) (PEG)-silane, patterning of photoresist, treatment with oxygen plasma and adsorption of collagen (I). The ITO surfaces were analyzed with 26 keV C(60) (+)SIMS run in the event-by-event bombardment-detection mode at different steps of the modification process. We were able to evaluate the extent of cross-contamination between different steps and quantify coverage of the immobilized species. The methodology described here provides a novel means for characterizing the composition of biological micropatterns in a quantitative and spatially-resolved manner. 相似文献
100.
A novel approach is proposed for extracting a maximum of information from secondary ions ejected when surfaces are bombarded with keV mono or polyatomic ions. It is known that the event-by-event bombardment-detection mode allows identification of spatiotemporal relationships among individual secondary ions which in turn reveal surface composition within nanometric dimensions. We have devised a procedure for identifying spatiotemporal relationships among individual secondary ions without the requirement of pulsed sample interrogation (one single projectile at a time). The consequence of "mass separated time-of-flight mass spectrometry" is a much improved measurement duty cycle. 相似文献