全文获取类型
收费全文 | 123篇 |
免费 | 1篇 |
专业分类
化学 | 93篇 |
力学 | 6篇 |
数学 | 10篇 |
物理学 | 15篇 |
出版年
2024年 | 1篇 |
2020年 | 1篇 |
2018年 | 4篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 6篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 8篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 7篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1934年 | 1篇 |
1885年 | 2篇 |
1874年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 78 毫秒
1.
2.
Zusammenfassung Die theoretischen und experimentellen Bedingungen für eine verbesserte Auswertung der Röntgenkleinwinkelstreuung von Hochpolymeren werden untersucht. Es wird gezeigt, daß genaue Messungen des Intensitätsverlaufes bei größeren Winkeln die Trennung der Kleinwinkelstreuung in eine reine Grenzflächenstreuung und eine Komponente der Dichteschwankungen innerhalb der Phasen ermöglicht.Diese Trennung erhöht die Genauigkeit der Bestimmung der Invarianten und gestattet die Berechnung der mittleren Durchschußlänge der kristallinen und amorphen Bereiche.Ein Vergleich dieses Längenparameters mit der Langperiode führt bei Annahme einer Lamellenstruktur zu einer Aussage über die Unebenheit der Grenzflächen.Der Absolutwert der Dichtefluktuation innerhalb der Phasen stellt einen zusätzlichen Strukturparameter dar, der besonders stark vom Unordnungsgrad der amorphen Bereiche abhängt.Ein Vergleich der experimentellen Ergebnisse mit Intensitätsverteilungen im Kleinwinkelbereich, die sich aus der Theorie des Parakristalls ergeben, zeigt, daß es nicht möglich ist, diese Theorie mit den Resultaten der Messungen in Einklang zu bringen.
Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung Berlin 1971 vom 9. bis 13. März des Regionalverbandes Physikalische Gesellschaft zu Berlin.
Wir danken Herrn Dr.H. Tompa für das Programm zur Berechnung der in Abb. 9 wiedergegebenen Interferenzfunktion, Herrn Prof. Dr.G. Rehage für die Polystyrolpräparate und HerrnJ. P. Pauwels, HerrnJ. Braibant und dem Personal unseres Rechenzentrums für die Mitarbeit. 相似文献
Summary The theoretical and experimental conditions for an improved method of evaluating the X-ray small-angle scattering of polymers are studied. It is shown that accurate measurements of the intensity distribution at wide angles makes it possible to decompose the small-angle scattering into a component due to the phase boundaries only and a component related to the density fluctuations within the phases.This separation increases the accuracy of the determination of the invariant and permits the calculation of the average length of segments of the crystalline and the amorphous regions.Assuming a lamellar structure, a comparison of this length parameter with the long period can be used to assess the planarity of the boundaries. The absolute value of the density fluctuations within the phases represents a supplementary structural parameter which is largely determined by the degree of disorder in the amorphous regions.A comparison of the experimental results with calculated intensity distributions in the small-angle region based on the theory of the paracrystal shows that it is impossible to bring this theory into agreement with the experimental results.
Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung Berlin 1971 vom 9. bis 13. März des Regionalverbandes Physikalische Gesellschaft zu Berlin.
Wir danken Herrn Dr.H. Tompa für das Programm zur Berechnung der in Abb. 9 wiedergegebenen Interferenzfunktion, Herrn Prof. Dr.G. Rehage für die Polystyrolpräparate und HerrnJ. P. Pauwels, HerrnJ. Braibant und dem Personal unseres Rechenzentrums für die Mitarbeit. 相似文献
3.
For some saline environments (e.g. deeply percolating groundwater, interstitial water in marine sediments, water sample collected after several steps of fractionation) the volume of water sample available is limited. A technique is presented which enables simultaneous determination of major and trace elements after preconcentration of only 60 mL sample on chelating resins. Chelex-100 and Chelamine were used for the preconcentration of trace elements (Cd, Cu, Pb, Zn, Sc) and rare earth elements (La, Ce, Nd, Yb) from saline water before their measurement by inductively coupled plasma mass spectrometry. Retention of the major elements (Na, Ca, Mg) by the Chelamine resin was lower than by Chelex; this enabled their direct measurement in the solution after passage through the resin column. For trace metal recoveries both resins yield the same mass balance. Only Chelex resin enabled the quantitative recovery of rare earth elements. The major elements, trace metals and rare earth elements cannot be measured after passage through one resin only. The protocol proposes the initial use of Chelamine for measurement of trace and major elements and then passage the same sample through the Chelex resin for determination of the rare earth elements. The detection limit ranged from 1 to 12 pg mL(-1). At concentrations of 1 ng mL(-1) of trace metals and REE spiked in coastal water the precision for 10 replicates was in the range of 0.3-3.4% (RSD). The accuracy of the method was demonstrated by analyzing two standard reference waters, SLRS-3 and CASS-3. 相似文献
4.
5.
Alessandra Gentili Fulvia Caretti Giuseppe D’Ascenzo Lucia Mainero Rocca Stefano Marchese Stefano Materazzi Daniela Perret 《Chromatographia》2007,66(9-10):669-676
Two new methods of analysis, based on liquid chromatography–tandem mass spectrometry, for simultaneous determination of trichothecenes A, B, and D in maize flour and oil have been developed and validated in accordance with European Commission decision 2002/657/EC (recovery, CCα, CCβ, and precision). The trichothecenes were extracted from maize flour by matrix solid-phase dispersion, with recoveries ≥79%, and from maize oil by liquid–liquid extraction, with recoveries ≥78%. Limits of quantitation ranged between 0.03 and 50 μg kg?1, depending on the electrospray response to each analyte and on the matrix. Monitoring of flour and oil samples with this HPLC–MS–MS method revealed the presence of deoxynivalenol, T-2 toxin, and diacetoxyscirpenol at very low concentrations. 相似文献
6.
Marchese S Curini R Gentili A Perret D Rocca LM 《Rapid communications in mass spectrometry : RCM》2004,18(3):265-272
A simple and rapid method using reversed-phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene in human urine specimens and standard solutions is described. A hybrid quadrupole/time-of-flight (QqTOF) mass spectrometer was compared for the determination of metabolite of aromatic solvents in urine samples. The metabolites selected were: trans,trans-muconic acid, hippuric acid, o-, m- and p-methylhippuric acid and phenylglyoxylic acid. The compounds were well separated from each other on narrow-bore 1-mm i.d. reversed-phase LC C-18 columns. Average recoveries for loading 100 microL of urine samples varied from 88-110% and the quantification limits were less than 30 ng/mL for each analyte (3 ng/mL for trans,trans-muconic acid). The qualitative information obtained (mass accuracy, resolution and full-scan spectra) with the QqTOF mass spectrometer allows a secure identification of analytes in biological matrices. 相似文献
7.
E.P. Kündig C. Perret S. Spichiger G. Bernardinelli 《Journal of organometallic chemistry》1985,286(2):183-200
Di-η6-naphthalenechromium(0) (1) reacts at 150°C with benzene to yield (η6-naphthalene)(η6-benzene)chromium(0) (3) in 76% yield. In the presence of THF, 1 undergoes Lewis base catalyzed arene exchange at 80°C. Reactions of 1 with substituted arenes yield the mixed sandwich complexes 4 and 6–10 (arene = 1,4-C6H4Me2, 1,3,5-C6H3Me3, C6Me6, 1,4-C6H4(OMe)2, 1,4-C6H4F2 and 1,4-C10H6Me2). In all but one case (with 1,4-dimethylnaphthalene) exchange of a single naphthalene ligand is observed. In marked contrast to the lability of 1, dimesitylenechromium(0) (5) is inert to arene displacement in benzene up to 240°C. The molecular structure of 3 has been determined by X-ray crystallography. The crystal data are as follows: a 7.784(1), b 13.411(2), c 22.772(5) Å, Z = 8, space group Pbca. The structure was refined to a Rw value of 0.043. The naphthalene ligand in 3 is nearly planar and parallel to the approximately eclipsed benzene ring. Metal atom-ring distances are 1.631(9) and 1.611(4) Å for naphthalene and benzene, respectively. Catalyzed and uncatalyzed naphthalene exchanges in the sandwich complex are compared to the analogous reactions with the Cr(CO)3 complex 2. Naphthalene exchange in 2 in benzene is 103 to 104 times faster than arene exchange in other arenetricarbonylchromium compounds. The mild conditions for Lewis base catalyzed naphthalene exchange make 2 a good precursor of other arenetricarbonylchromium compounds. Examples include the Cr(CO)3 complexes of styrene, benzocyclobutene, 1-ethoxybenzocyclobutene, 1,8-dimethoxy-9,10-dihydroanthracene and 1,4-dimethylnaphthalene. 相似文献
8.
A combination of energy filtered transmission electron microscopic (EF-TEM) procedures is proposed for the non-perturbing physico-chemical characterization of submicron mineral and organic colloids in aquatic systems. Synthetic hematite microparticles and xanthan polysaccharides were used as well-characterized model colloids in order to determine the optimum EF-TEM analysis conditions. In this paper, it is demonstrated that (i) our model colloids are morphologically representative of naturally occurring mineral/organic associations, (ii) EF-TEM allows the detection of fine xanthan ultrastructures without artefacts of conventional staining methods and (iii) submicron hematite particles can be specifically visualized and spectrometrically measured by EF-TEM within a hematite/xanthan mixture. This EF-TEM procedure appears to be appropriate for the characterization of real aquatic samples. 相似文献
9.
Nitrogen and carbon monoxide are physically adsorbed on polyvinylchloride between 78 and 86 K, without hysteresis. At higher temperatures, carbon dioxide (195 K), sulfur dioxide (273 and 293 K) and chloroethane (293 K) are strongly absorbed by the solid, with hysteresis. The possibility of trapping CO inside the solid indicates that PVC has an open structure at higher temperatures. The effect of heating on the polymer was also investigated. 相似文献
10.