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81.
82.
For the spectrophotometric characterization of redox reactions, a logarithmic transformation is proposed by which it is possible to analyse indirectly the functions E = f (pH) and E = f (C) derived from experimental data. Besides the mechanism of the reaction the equilibrium constant can also be calculated. The method is generally usable for equimolar redox systems and also for non-equimolar ones if a single equilibrium exists in the range under examination. References to the evaluation are given and the practicability is demonstrated with the system Fe(3+)/SO(2-)(3). 相似文献
83.
Russell SC Czerwieniec G Lebrilla C Tobias H Fergenson DP Steele P Pitesky M Horn J Srivastava A Frank M Gard EE 《Journal of the American Society for Mass Spectrometry》2004,15(6):900-909
The appearance of informative signals in the mass spectra of laser-ablated bio-aerosol particles depends on the effective ionization probabilities (EIP) of individual components during the laser ionization process. This study investigates how bio-aerosol chemical composition governs the EIP values of specific components and the overall features of the spectra from the bio-aerosol mass spectrometry (BAMS). EIP values were determined for a series of amino acid, dipicolinic acid, and peptide aerosol particles to determine what chemical features aid in ionization. The spectra of individual amino acids and dipicolinic acid, as well as mixtures, were examined for extent of fragmentation and the presence of molecular ion dimers, which are indicative of ionization conditions. Standard mixtures yielded information with respect to the significance of secondary ion plume reactions on observed spectra. A greater understanding of how these parameters affect EIP and spectra characteristics of bio-aerosols will aid in the intelligent selection of viable future biomarkers for the identification of bio-terrorism agents. 相似文献
84.
K. H. Koch K. Ohls E. Sebastiani und G. Riemer 《Fresenius' Journal of Analytical Chemistry》1970,249(5):307-312
Zusammenfassung Die direkte Bestimmung von Kobalt in unterschiedlichen Substanzen im Gehaltsbereich von 0,001 bis 5% ist nach einem einfachen Verfahren möglich, wenn die Komplexbildungsreaktion und der tatsächliche Störeffekt durch andere Elemente bekannt sind. Die für eine Bestimmung benötigte Zeit beträgt 25 min. Die relative Standardabweichung liegt zwischen 0,02–20%.
Direct photometric determination of cobalt in iron, steels, ores and slags using nitroso-R-salt
A simple procedure without any separation is described; the complex formation and the interfering effects of other elements are studied. This method is suitable for the accurate determination of 0.001 to 5% of cobalt in several materials. The time required for one determination is 25 min only. The coefficients of variation are within 0.02–20%.相似文献
85.
Peter Xaver Iten Hana Mrki-Danzig Herbert Koch Conrad Hans Eugster 《Helvetica chimica acta》1984,67(2):550-569
Isolation and Structure Elucidation of Pteridines (Lumazines) from Russula sp. (Basidiomycetes) Extensive chromatogaphic separations and spectroscopic investigations have led to the isolation and identification of several water-soluble pteridines from Russula sp., the so-called russupteridines, namely: 1-(5-amino-2-6-dioxo-1,2,3,6-tetrahydeopyrimidin-4-yl)amino-1-deoxy-D -ribitol ( 1 ; a pro-lumazine; first identification in a basidiomycete(; l-deoxy-l-(6-methyl-2-4,7-trioxo-1,2,3,4,7,8-hexahydro-pteridin-8-yl)-D -ribitol ( 3 ) and l-deoxy-1-(2,4,7-trioxo-1,2,3,4,7,8-hexahydeopteridin-8-yl)-D -ribitol ( 4 ); both compounds found for the first time in higher fungi; they belong to the components with the strongest violet-blue fluorescence in Russula sp.; riboflavine ( 6 ; now recognized as an important yellow colorant in a great many of Russula sp.); russupteridine-yellow I (= l-(6-amino-7-(N-fromylimino)-2,4-dioxo-1,2,3,4,7,8-hexahydropteridin-8-yl)-1-deoxy-D -ribitol; 5 ; a component with very strong fluorescence; the first derivative of the novel 6,7-diamino-lamazine); russupteridine-yellow IV (= l-deoxy-1-)(2,6,8-trioxo-2,4,5,6,7,8-hexahydro-1H-imidazolo[4,5-g]pteridin-4-yl)-D -ribitol (7)). Two further yellow russupteridines (yellow II and Yellow V) with very strong fluorescence have been isolated and characterized. 相似文献
86.
Analysis of the total antimony in plant material was unsuccessful using the electrothermal atomic absorption spectrometry (ETAAS) conditions recommended by the instrument manufacturer. For this reason, an optimisation procedure utilising the Plackett-Burman method, simplex optimisation and visualisation of the generated response surface via principal components analysis, was carried out. The Plackett-Burman method was used to eliminate four of the initial variables chosen. Four variables (atomisation temperature, atomisation time, ash temperature and modifier concentration) were subsequently optimised using the composite modified simplex method and the results were visualised as a contour diagram, after reduction to two principal components. The optimised conditions were used for the analysis of both an acid digested pine needle standard reference material (NIST 1575) and a pond weed sample, collected from a contaminated site at Yellowknife Bay, Yellowknife, NWT, Canada. The total concentration of antimony present in the pine needles was statistically indistinguishable from the non-certified value, as was the value for the pond weed sample, compared with a value determined by neutron activation analysis (NAA). The results for the analysis of the pond weed sample by ETAAS agreed with those obtained from a subsequent analysis by inductively coupled plasma-mass spectrometry. 相似文献
87.
88.
Nernst R Antreasyan D Aschman D Besset D Bienlein JK Bloom ED Brock I Cabenda R Cartacci A Cavalli-Sforza M Clare R Conforto G Cooper S Cowan R Coyne D de Judicibus D Edwards C Engler A Folger G Fridman A Gaiser J Gelphman D Godfrey G Heimlich FH Hofstadter R Irion J Jakubowski Z Keh S Kilian H Kirkbride I Kloiber T Koch W König AC Königsmann K Kraemer RW Lee R Leffler S Lekebusch R Lezoch P Litke AM Lockman W Lowe S Lurz B Marlow D Maschmann W Matsui T Messing F Metzger WJ Monteleoni B 《Physical review letters》1985,54(20):2195-2198
89.
90.
Zusammenfassung Die beiden wichtigsten Verfahren zur quantitativen Analyse der Gefügebestandteile heterogener Legierungen sind die potentiostatische Isolierung und die Lokalanalyse mit der Elektronenstrahlmikrosonde. Manganstähle mit Carbiden definierter Zusammensetzung und Größe boten die Möglichkeit, erstmalig die quantitativen Aussagen dieser beiden Methoden miteinander zu vergleichen.Dabei erbrachte die Isolierung durch die gleichzeitige analytische Erfassung größerer Mengen der Matrix und der Carbidphasen sehr genaue Angaben ihrer durchschnittlichen Zusammensetzung. Örtliche Konzentrationsänderungen in derselben Phase werden jedoch nicht erfaßt. Dagegen zeigte sich, daß die lokale Röntgenspektralanalyse zwar vergleichbare Ergebnisse lieferte, aber auch bei Anregung mit einem feinfokussierten Elektronenstrahl (Durchmesser <1) die Genauigkeit der Werte bei Teilchengrößen <5 durch Anregung von Nachbarbereichen merkbar beeinflußt wird.Zerlegung und Phasenanalyse einerseits sowie Lokalanalyse mit der Elektronenstrahlmikrosonde anderseits haben ihren eigenständigen Anwendungsbereich. Unter Berücksichtigung der gegebenen Grenzen können sich beide Methoden zur Analyse metallischer Werkstoffe sinnvoll ergänzen.
Vortrag anläßlich des Kolloquiums für metallkundliche Analyse mit besonderer Berücksichtigung der Elektronenstrahl-Mikroanalyse, Wien, 22. Oktober 1964. 相似文献
Summary The two most important procedures for the quantitative analysis of the structural constituents of heterogeneous alloys are the potentiostatic isolation and the local analysis by means of the electron beam microsonde. Manganese steels with carbides of definite composition and magnitude offered the possibility for securing quantitative statements for the first time with respect to the comparative merits of these two methods.The isolation gave very precise information concerning the average composition through the concurrent analytical involvement of larger amounts of the matrix and the carbide phases. However, local alterations in the concentration within the same phase were not revealed. On the other hand, it was found that though the local X-ray spectral analysis yielded comparable results, the accuracy of the values at particle sizes <5 is markedly influenced through excitation of neighboring regions when the excitation was due to a fine-focused electron beam (Ø <1).Decomposition and phase analysis on one hand and local analysis with the electron beam-microsonde on the other have their individual fields of application. If the given limitations are taken into account, both methods may contribute judiciously to the analysis of metallic industrial materials.
Résumé L'isolement potentiostatique et l'analyse locale par la microsonde électronique représentent les deux procédés les plus importants pour l'analyse quantitative des constituants entrant dans la texture des alliages hétérogènes. Les aciers au manganèse avec carbures en composition et quantité définies offrent la possibilité, pour la première fois, de comparer entre elles les indications quantitatives de ces deux méthodes.L'isolement par détermination analytique simultanée de plus grandes quantités de matrice et de la phase carbure a rendu des données très précises de leur composition moyenne. Les modifications de concentration locale dans la même phase n'ont pourtant pas été atteintes. Par contre, il s'est avéré que l'analyse spectrale locale par rayons X conduisait à des résultats comparables, mais en excitant par un faisceau d'électrons finement focalisé (Ø<1), l'exactitude de la valeur pour les particules de dimensions inférieures à 5 se trouve influencée de façon notable par excitation des régions voisines.La séparation et l'analyse des phases d'une part, l'analyse locale par la microsonde à faisceau d'électrons d'autre part, ont leur domaine d'application propre. En tenant compte des limites données, les deux méthodes peuvent se compléter d'une manière judicieuse pour l'analyse des produits métalliques oeuvrés.
Vortrag anläßlich des Kolloquiums für metallkundliche Analyse mit besonderer Berücksichtigung der Elektronenstrahl-Mikroanalyse, Wien, 22. Oktober 1964. 相似文献