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61.
Linearly related functions have been derived which enable mixtures of three weak acids or bases in solution to be analysed by means of pH-titration data. This theory has been tested with data from the titration of a variety of mixtures of acids. The data required for the functions are pH, volume of titrant, the equilibrium constants relevant to the mixture, and an independently determined equivalence volume. This may be the equivalence volume for one of the components of the mixture or the sum of the equivalence volumes for any two or all three of the components. It is immaterial how this equivalence volume is obtained, but it is usually possible to obtain the total equivalence volume from data in another part of the same titration curve (when a large excess of titrant has been added). 相似文献
62.
Upper critical fields, Hc2(T), for superconducting LaMo6Se8, La0.8Eu0.2Mo6Se8, La0.8Ce0.2Mo6Se8 and PrMo6Se8 were measured. For the best material, LaMo6Se8, Tc = 11.3 K, (dHc2/dT)T=Tc=70 kG/K and and Hc2 (4.2 K) = 370 kG. These selenide compounds show promise as very high field superconductors. 相似文献
63.
Summary A linear titration plot method has been derived for the determination of partially neutralized weak acids or weak bases from pH-titration data. A FORTRAN program calculates the total concentration of acid or base in solution as well as the fraction remaining to be neutralized. The program also detects the presence of strong acid with a weak acid or a strong base with a weak base. The weak acid or base may be polyfunctional with overlapping dissociation steps. Activity coefficients are calculated iteratively.
Lineare Titrationskurven für die potentiometrische Titration von teilweise neutralisierten schwachen Säuren und Basen
Zusammenfassung Lineare Titrationskurven werden für potentiometrische Titrationen von schwachen Säuren und Basen, die bereits teilweise neutralisiert sind, abgeleitet. Eine Fortran-Prozedur berechnet sowohl die Gesamtkonzentration der Säure oder Base als auch den Neutralisationsgrad. Das Rechenprogramm erfaßt auch die Anwesenheit einer starken Säure zusammen mit einer schwachen Säure oder einer starken Base zusammen mit einer schwachen Base. Die schwache Säure oder Base darf mehrere überlappende Dissoziationsstufen aufweisen. Aktivitätskoeffizienten werden mittels eines Iterationsverfahrens berechnet.相似文献
64.
The hitherto unknown tribenzotetracene(V) was synthesized and fitted into the series: heptacene(I), benzohexacene(II), the dibenzopentacenes III and IV, tribenzotetracene(V) and tetrabenzanthracene (VI). It is obvious that in the series I → VI the stability increases and the absorption bands shift to shorter wavelength with the number of benzenoid rings (marked with circles). In contrast to this the absorption spectra of the benzotetracenes show little change in the annellation series VII → V → VIII because the benzenoid rings were fused to double bond which are already localized. 相似文献
65.
66.
Zhengwen Xiao Gerald G. Miller Theresa J. McCallum Kevin M. Brown J. William Lown John Tulip Ronald B. Moore 《Photochemistry and photobiology》1998,67(5):573-583
Photodynamic therapy (PDT) has been considered as a potential therapy for superficial bladder carcinomas. Cutaneous photosensitivity and reduction of bladder capacity are the two well-known complications following systemic administration of the commonly used photosensitizer, Photofrin II® (PII). The objective of the present study was to evaluate whether intravesical. (i.b.) instillation of photosensitizers for PDT of bladder cancer might be a more suitable treatment method. Female Fischer rats were utilized to develop orthotopic and heterotopic bladder tumor models. Rats bearing orthotopic bladder tumors were treated either intravesically or intravenously with graded doses of 5-aminolevulinic acid (ALA) or PII. Normal rats received the same doses of ALA or PII. As well, rats bearing heterotopic tumor were studied for comparison. The biodistribution times (times allowed for tissue uptake and bioconversion following drug administration) were 2, 4 or 6 h. Porphyrin fluorescence intensities within tumor, urothelium, submucosa, bladder muscularis and abdominal muscle were quantitated by confocal laser scanning microscopy. Following intravenous (i.v.) injection of ALA, tumor protoporphyrin IX (PpIX) levels peaked at 4 h and diminished by 6 h. The PpIX ratios of tumor-to-bladder mucosa, submucosa and muscle layers were 3:1, 5:1 and 8:1, respectively, 4 h following 1000 mg/kg ALA injection. After ALA instillation, the optimal biodistribution time appeared to be 4 h. Bladder instillation provided comparable tumor labeling with the i.v. route, but lost selectivity of PpIX accumulation between tumor and normal urothelium. The PpIX ratio of tumor-to-bladder muscularis was 5:1. After i.b. instillation of PII, porphyrin fluorescence was detected only within tumor and urothelium, while porphyrin fluorescence was mainly located in bladder submucosa following i.v. injection. Intravesical administration of ALA or PII might be feasible for PDT of superficial bladder cancers. 相似文献
67.
William G. McCallum 《Mathematische Annalen》1992,294(1):503-511
This research was supported in part by National Science Foundation grant DMS-9002095 相似文献
68.
The γ-radiation following the decay of 112Ag has been studied with a Ge(Li) detector. A total of 76 γ-rays was observed. The γ-γ coincidence and angular correlation relations involving the 617 keV 2+-0+ transition have been measured using Ge(Li)-NaI(Tl) and NaI(Tl)-NaI(Tl) detectors. These results have been used to confirm spins and parities of some levels of 112Cd in the proposed decay scheme. Cross sections for 112Ag production by 115In(n,α) and 112Cd(n, p) reactions have been measured; the 112Ag half-life has been determined as 3.14 ± 0.02 h. 相似文献
69.
McCallum JE Kuniyoshi CY Foote CS 《Journal of the American Chemical Society》2004,126(51):16777-16782
The photosensitized oxidation of 2',3',5'-tris-(O-tert-butyldimethylsilyl)-8-oxo-7,8-dihydroguanosine (8-oxoG) with singlet oxygen was studied by low-temperature NMR. A stable intermediate was characterized at -60 degrees C by (13)C, 2D NMR HMBC spectra, and chemical shifts calculated by hybrid Hartree-Fock density functional theory which agreed with the structure 5-hydroperoxy-8-oxo-7,8-dihydroguanosine. Reduction of this intermediate at low temperature afforded the corresponding alcohol, the long-postulated 5-hydroxy-8-oxo-7,8-dihydroguanosine, the last intermediate in the formation of spiroiminodihydantoin. Upon warming to room temperature, this alcohol rearranges to form the spiroiminodihydantoin in good yield within 2 h. 相似文献
70.
R.W. McCallum W.A. Kalsbach T.S. Radhakrishnan F. Pobell R.N. Shelton P. Klavins 《Solid State Communications》1982,42(11):819-822
Magnetization measurements in a static field as a function of temperature (2.5–20K) and pressure to 14 kbar are reported for a series of well characterized samples of EuMo6+xS8?y. From these d.c. magnetization data, we find no evidence for bulk superconductivity in any of our samples, although some of them exhibit a strong diamagnetic anomaly in the a.c. susceptibility under pressure, similar to that reported in the literature. An explanation for this anomaly is presented in terms of the presence of a granular superconducting impurity on the grain boundaries of the Chevrel phase compound EuMo6S8. 相似文献