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41.
42.
Prenesti E Fisicaro P Berto S Ferrara E Daniele PG 《Analytical and bioanalytical chemistry》2007,387(7):2595-2600
This paper reports evaluation of the behaviour of different combined glass electrodes applied to measurement of the pH of
a primary, 0.01 mol kg−1, tetraborate buffer. Measurements were first performed by use of a primary Harned cell (at 15, 25, and 37 °C); these results
were then compared with those obtained for the same solution by use of three combined glass electrodes (25 °C) with different
membranes and liquid-junction designs, calibrated by use of commercial pH-metric buffers. The pH of the same solution was
also measured in terms of the molal concentration of hydrogen ions, using acid–base titration to evaluate the formal potential
difference K of each cell at fixed ionic strength, I, adjusted by addition of KCl or Et4NI (tetraethylammonium iodide). The reference value from primary measurement, paH = 9.171, was slightly closer to the mean value obtained by determination of concentration, rather than that obtained by
direct measurement of activity; the differences were smaller than the extended uncertainty characteristics of the secondary
measurements. The importance of evaluation of the ionic strength of the solution under study is emphasised. We verified that
for tetraborate buffer slight modification of the value of I used to calculate γ
i
(the activity coefficient of a single ion) in the calculation of paH from the acidity function at zero molality of chloride can significantly affect the reference value of the calibrator tool.
This is true, in general, for low values of the ionic strength, such as those considered in this work; an approximate value
of I can then cause distortions along the pH traceability chain. Application of the concepts of thermodynamics to this traceability
chain is discussed. 相似文献
43.
Ferrara SD Nalesso A Castagna F Montisci M Vogliardi S Favretto D 《Rapid communications in mass spectrometry : RCM》2007,21(18):2944-2950
A method was developed to accurately quantify atracurium (a non-depolarizing skeletal muscle relaxant) and its metabolite laudanosine in post-mortem specimens. Analytes were isolated from blood and tissues by liquid/liquid extraction after adding vecuronium as an internal standard. Chromatographic separation was accomplished by gradient elution in a Synergy Max RP 150 x 2.1 mm column. Positive ion electrospray ionization and mass spectrometric analyses were carried out in an ion trap mass spectrometer under collision-induced dissociation conditions. The method proved selective and sensitive, and was validated in post-mortem blood, heart, lung and liver in the range of 1-2000 ng/mL (blood) and 5-5000 ng/g (tissues); the limits of quantification obtained were 1 ng/mL in blood and 5 ng/g in tissues. 相似文献
44.
In this paper we identify some properties on the point-line structure of Grassmannians which are useful tools to characterize the incidence geometry of Grassmann varieties and of their special quotients. 相似文献
45.
Jose G. Trujillo‐Ferrara Efrn V. García‐Bez Itzia I. Padilla‐Martínez Francisco J. Martínez‐Martínez Norberto Farfan‐García 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(6):o427-o430
In exo‐2‐(3,5‐dioxo‐10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)phenyl acetate, C16H13NO5, the plane of the acetoxy group lies almost perpendicular to that of the phenyl ring [dihedral angle = 89.8 (1)°], in contrast with the smaller deviations found in the para isomer exo‐4‐(3,5‐dioxo‐10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)phenyl acetate, C16H13NO5, these being 63.6 (1) and 37.0 (1)° for the two crystallographically independent molecules. Irrespective of the position of the acetoxy group, both compounds pack through soft C—H⋯X (X is O or phenyl) interactions, forming interlinked centrosymmetric tetramers in the bc plane. 相似文献
46.
Vogliardi S Favretto D Frison G Ferrara SD Seraglia R Traldi P 《Journal of mass spectrometry : JMS》2009,44(1):18-24
Matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry was used for the rapid detection of cocaine, benzoylecgonine and cocaethylene in hair. Different MALDI sample preparation procedures have been tested and the employment of a multi-layer 'graphite-sample-electrosprayed alpha-cyano-4-hydroxycinnamic acid (HCCA)' yielded the best results for standard solutions of the target analytes. The same approach was subsequently applied to hair samples that were known to contain cocaine, benzoylecgonine and cocaethylene, as determined by a classical GC-MS method. It was however necessary to extract hair samples by incubating them in methanol/trifluoroacetic acid for a short time (15 min) at 45 degrees C; 1 microl of the obtained supernatant was deposed on a metal surface treated with graphite, and HCCA was electrosprayed on it. This procedure successfully suppressed matrix peaks and was effective in detecting all the target analytes as their protonated species. The results obtained give further confirmation of the effectiveness of the MALDI for detecting drugs and their metabolites in complex biological matrices. The method can be useful as a fast screening procedure to detect the presence of cocaine and metabolites in hair samples. 相似文献
47.
48.
It is an elementary exercise to show that any non-trivial simple graph has two vertices with the same degree. This is not the case for digraphs and multigraphs. We consider generating irregular digraphs from arbitrary digraphs by adding multiple arcs. To this end, we define an irregular labeling of a digraph D to be an arc-labeling of the digraph such that the ordered pairs of the sums of the in-labels and out-labels at each vertex are all distinct. We define the strength of D to be the smallest of the maximum labels used across all irregular labelings. Similar definitions for graphs have been studied extensively and a different formulation of digraph irregularity was given in [H. Hackett, Irregularity strength of graphs and digraphs, Masters Thesis, University of Louisville, 1995]. Here we continue the study of irregular labelings of digraphs. We give a general lower bound on and determine exactly for tournaments, directed paths and cycles and the orientation of the path where all vertices have either in-degree 0 or out-degree 0. We also determine the irregularity strength of a union of directed cycles and a union of directed paths, the latter which requires a new result pertaining to finding circuits of given lengths containing prescribed vertices in the complete symmetric digraph with loops. 相似文献
49.
Giovanni Ferrara Tienan Jin Md. Akhtaruzzaman Ashraful Islam Liyuan Han Hua Jiang Yoshinori Yamamoto 《Tetrahedron letters》2012,53(15):1946-1950
A facile, efficient, and general synthetic method for iodo-substituted benzo[b]naphtho[2,1-d]thiophenes has been developed via a cascade cyclization of thioanisole-substituted aryldiynes using iodine. A new donor–π linker–acceptor (D–π–A) organic dye, G1, with the benzo[b]naphtho[2,1-d]thiophene moiety as an electron donor has been synthesized, and the performance of dye-sensitized solar cell based on G1 has been investigated. 相似文献
50.
Raman scattering experiments on CdI2 at high sensitivity give evidence of several new lines in addition to well known ones. The measurements performed at different temperatures allow us to distinguish between one phonon spectrum and two phonon one. The assignment of the new lines associated to one phonon scattering is also discussed. 相似文献