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101.
Oswald Riedel 《Fresenius' Journal of Analytical Chemistry》1964,201(4):253-262
Zusammenfassung Zur Reinheitsbestimmung schmelzbarer, vorwiegend organischer Proben wurde eine kryoskopische Apparatur nachSmit gebaut. Sie arbeitet oberhalb 99 Mol-% im Halbmikrobereich, wobei der Absolutwert der Reinheit auf ±0,05 Mol-% genau meßbar ist. Die Probe, die ständig unter strömendem Stickstoff gehalten wird, umgibt als dünne Schicht ein Platin-Widerstandsthermometer, das sich in der Mitte eines elektrisch geheizten Aluminiumzylinders befindet. Konstanz der Wärmezufuhr wird gesichert durch Regelung der Temperaturdifferenz gegen ein gleichartiges zweites Thermometer, das dicht am geheizten Zylindermantel eingesteckt ist. Die Thermometer brauchen nicht geeicht zu werden. Die Regelung wird durch eine Doppel-Wheatstonebrücke vermittelt, deren einer Ausgang auf den Schreiber und deren anderer auf die Heizung wirkt. Die graphische Auswertung ist aus dem Zweiphasen-Diagramm fest-flüssig abgeleitet. Als Bezugsstandard ist eine zweite Probe zu messen, die man durch Verunreinigung der ursprünglichen Substanz um einen bekannten Betrag erhält.
Unter Mitarbeit von F.Weigand und R.Baumgart.
Herrn Dr.Ebinger, AEG-Meßgerätefabrik Berlin-Reinickendorf und Herrn Dipl.-Ing. Lutz, AEG-Büro Mannheim, habe ich für ihre große Bereitwilligkeit zu danken, mit der sie auf die Wünsche zur Bauart der Brücke eingingen. — Für Anregungen danke ich Herrn Dr.Kienitz. 相似文献
Summary A cryoscopic apparatus for the purity assay of fusible, mostly organic samples was built afterSmit. It works in the half-micro scale above 99 mole%, where the absolute value of the purity will lie within ±0.05 mole%. The sample, which is always kept under streaming nitrogen, surrounds as a thin layer a platinum resistance thermometer that stands in the center of an electrically heated aluminium cylinder. A constant supply of heat is ensured by controlling the temperature difference against a second thermometer of the same kind, which is inserted near the heated periphery of the cylinder. It is not necessary to calibrate the thermometers. Control is mediated by a double Wheatstone bridge, the one output of which acts on the recording device, the other on the heater. The graphical evaluation of the records derives from the two-phase diagram solid-liquid. As a referential instance, a second sample has to be measured, which is obtained from the specimen through artificial contamination by a known amount.
Unter Mitarbeit von F.Weigand und R.Baumgart.
Herrn Dr.Ebinger, AEG-Meßgerätefabrik Berlin-Reinickendorf und Herrn Dipl.-Ing. Lutz, AEG-Büro Mannheim, habe ich für ihre große Bereitwilligkeit zu danken, mit der sie auf die Wünsche zur Bauart der Brücke eingingen. — Für Anregungen danke ich Herrn Dr.Kienitz. 相似文献
102.
Summary Different methods for removing interference by humic substances in the analysis of polar pollutants have been compared in
the analysis of environmental water by solid-phase extraction (SPE) with a chemically modified polymeric resin coupled on-line
to liquid chromatography with UV detection.
The methods were based on the use of chemical reagents. The best method was found to be addition of sodium sulphite to humic-containing
water before SPE. The appropriate amount of sulphite depends on the amount of humic substances dissolved in the sample—for
analysis of 50 mL tap and Ebro river water, respectively, 250 μL and 500 μL 10 % Na2SO3 solution had to be added. In both cases, the recovery values after chemical treatment were similar to those when a Milli-Q-quality
water standard was analysed. 相似文献
103.
Summary The acridines3,5, and6, as well as the dibenzo[b,f]-azepine4 were converted into the 3-oxo-derivatives7–10 using hypervalent iodine compounds (iodosylbenzene and bis-(trifluoroacetoxy)iodopentafluorobenzene).
Oxidation von Acridinen und Azepinen in ihre 3-Oxoderivate mit Hilfe von hypervalenten aromatischen Jodverbindungen (Kurze Mitt.)
Zusammenfassung Die Acridine3,5 und6 sowie das Dibenzo[b,f]azepin4 wurden mit Hilfe der beiden hypervalenten Jod-Verbindungen Jodosobenzol (1) und Bis-trifluoroacetoxyiodbenzol (2) zu den entsprechenden 3-Acridinonen7,9 und10 sowie zum Dibenzoazepin-3-on8 oxidiert.相似文献
104.
The spinels of the system LixMn1?xV2O4 (0 ? x ? 1) have been prepared at 700–750°C from LiV2O4 and MnV2O4. The lattice constants decrease linearly with increasing x. In the region x>0.75, the d-electrons of V should be delocalized as the VV distances are lower than the critical VV separation of 2.94 Å. Experimentally, the samples with x>0.6 show no IR absorption bands and the Seebeck coefficient is near zero. The Seebeck coefficient can be described with a model of intermediate polarons and can be expressed by the equation . 相似文献
105.
Marc A. Rieffel 《Monatshefte für Mathematik》1978,85(2):149-162
LetG be a countable discrete group acting by measure-preserving automorphisms of a finite measure space (M, ) and let
(G,M) be the corresponding group measure space von Neumann algebra, which will be a finite von Neumann algebra. Necessary and sufficient conditions are given for
(G,M) to have a non-zero type I part, and the projection on the type I part is explicitly described.This research was supported in part by National Science Foundation Grant MCS 74-19876. 相似文献
106.
Attempted thallium triflate abstraction of chloride anions from the MCl(2) complexes of the unsaturated chelating diphosphines o-dimethyl-bis(diphenylphosphino)tetrathiafulvalene (P2) (M = Pd, Pt) and cis-1,2-bis(diphenylphosphino)ethylene (dppen) (M = Pd) affords, surprisingly, a Tl(OTf) adduct in the case of (P2)PdCl(2) and (P2)PtCl(2), with no chloride abstraction, and a dicationic bis(palladium) bis(triflate) salt in the case of (cis-dppen)PdCl(2), in which only one Cl anion was removed. The crystal structures of these complexes were determined by X-ray analysis, which established the formulations (P2)MCl(2).Tl(OTf) (M = Pd, Pt) and [(dppen)PdCl](2)(OTf)(2), respectively. These compounds can be seen as possible intermediates in the general chloride abstraction process between (P-P)MCl(2) (M = Pd, Pt) and thallium triflate. 相似文献
107.
Daniel Ammann Ren Bissig Marc Güggi Ern Pretsch Wilhelm Simon Irving J. Borowitz Louis Weiss 《Helvetica chimica acta》1975,58(6):1535-1548
The preparation of a series of non-cyclic, uncharged ligands able to selectively complex alkali and alkaline earth metal cations is described. These molecules are designed to be used as carriers for cations through membranes. Some of the compounds show high Ca2+ and Na+ selectivity, respectively, in liquid membrane electrodes. 相似文献
108.
109.
Moses S Brewer SH Lowe LB Lappi SE Gilvey LB Sauthier M Tenent RC Feldheim DL Franzen S 《Langmuir : the ACS journal of surfaces and colloids》2004,20(25):11134-11140
Single- and double-stranded deoxy ribonucleic acid (DNA) molecules attached to self-assembled monolayers (SAMs) on gold surfaces were characterized by a number of optical and electronic spectroscopic techniques. The DNA-modified gold surfaces were prepared through the self-assembly of 6-mercapto-1-hexanol and 5'-C(6)H(12)SH -modified single-stranded DNA (ssDNA). Upon hybridization of the surface-bound probe ssDNA with its complimentary target, formation of double-stranded DNA (dsDNA) on the gold surface is observed and in a competing process, probe ssDNA is desorbed from the gold surface. The competition between hybridization of ssDNA with its complimentary target and ssDNA probe desorption from the gold surface has been investigated in this paper using X-ray photoelectron spectroscopy, chronocoulometry, fluorescence, and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). The formation of dsDNA on the surface was identified by PM-IRRAS by a dsDNA IR signature at approximately 1678 cm(-)(1) that was confirmed by density functional theory calculations of the nucleotides and the nucleotides' base pairs. The presence of dsDNA through the specific DNA hybridization was additionally confirmed by atomic force microscopy through colloidal gold nanoparticle labeling of the target ssDNA. Using these methods, strand loss was observed even for DNA hybridization performed at 25 degrees C for the DNA monolayers studied here consisting of attachment to the gold surfaces by single Au-S bonds. This finding has significant consequence for the application of SAM technology in the detection of oligonucleotide hybridization on gold surfaces. 相似文献
110.
J. L. Bernal M. J. Nozal L. Toribio M. L. Serna F. Borrull R. M. Marcé E. Pocurull 《Chromatographia》1997,46(5-6):295-300
Summary The eleven Environmental Protection Agency (EPA) priority phenolic compounds have been determined by solid-phase extraction
(SPE) coupled on-line to supercritical-fluid chromatography (SFC) with diodearray detection. The variables affecting chromatographic
separation were optimized and the analytes were separated at 40 °C in two diol columns connected in series; a gradient of
methanol, as modifier, and CO2 was used as mobile phase. Under these conditions, all the compounds studied were separated to baseline in less than 13 min.
PLRP-S and LiChrolut EN were tested as sorbents in a 10×3 mm i.d. laboratory-packed precolumn for solid-phase extraction.
An ion-pair reagent, tetrabutylammonium bromide (TBA), was used in the extraction process to increase break-through volumes.
The performance of the method was checked with tap and river waters and the pre-concentration of 20 mL of sample in a PLRP-S
pre-column enabled phenolic compounds to be determined at low μg L−1 levels with limits of detection ranging between 0.4 and 2 μg L−1. The repeatability and reproducibility between days (n=3) for real samples spiked at 10 μg L−1 were lower than 10%. 相似文献