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61.
Cs salts of four of the title anions were prepared by fluorination of salts of partly methylated (n = 11, 10) or partly methylated and partly iodinated (n = 6, 5) CB(11)H(12)(-) anions. The CH vertex is acidic, and in the unhindered anion with n = 6 it has been alkylated. Neat Cs(+)[1-H-CB(11)(CF(3))(11)](-) is as treacherously explosive as Cs(+)[CB(11)(CF(3))(12)](-), but no explosions occurred with the salts of the other three anions. BL3YP/6-31G* gas-phase electron detachment energies of the title anions are remarkably high, 5-8 eV. Treated with NiF(3)(+) in anhydrous liquid HF at -60 °C, anions with n = 11 or 10 resist oxidation, whereas anions with n = 6 or 5 are converted to colored EPR-active species, presumably the neutral radicals [HCB(11)(CF(3))(n)F(11-n)](?). These are stable for hours at -60 °C after extraction into cold perfluorohexane or perfluorotri-n-butylamine solutions. On warming to -20 °C in a Teflon or quartz tube, the color and EPR activity disappear, and the original anions are recovered nearly quantitatively, suggesting that the radicals oxidize the solvent. 相似文献
62.
Stíbr B Holub J Bakardjiev M Pavlík I Tok OL Císarová I Wrackmeyer B Herberhold M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(10):2239-2244
The reaction of nido-[7,8,9-PC(2)B(8)H(11)] (1) with [[CpFe(CO)(2)](2)] (Cp=eta(5)-C(5)H(5) (-)) in benzene (reflux, 3 days) gave an eta(1)-bonded complex [7-Fp-(eta(1)-nido-7,8,9,-PC(2)B(8)H(10))] (2; Fp=CpFe(CO)(2); yield 38 %). A similar reaction at elevated temperatures (xylene, reflux 24 h) gave the isomeric complex [7-Fp-(eta(1)-nido-7,9,10-PC(2)B(8)H(10))] (3; yield 28 %) together with the fully sandwiched complexes [1-Cp-closo-1,2,4,5-FePC(2)B(8)H(10)] 4 a (yield 30%) and [1-Cp-closo-1,2,4,8-FePC(2)B(8)H(10)] 4 b (yield 5%). Compounds 2 and 3 are isolable intermediates along the full eta(5)-complexation pathway of the phosphadicarbaborane cage; their heating (xylene, reflux, 24 h) leads finally to the isolation of compounds 4 a (yields 46 and 52%, respectively) and 4 b (yields 4 and 5%, respectively). Moreover, compound 3 is isolated as a side product from the heating of 2 (yield 10%). The structure of compound 4 a was determined by an X-ray structural analysis and the constitution of all compounds is consistent with the results of mass spectrometry and IR spectroscopy. Multinuclear ((1)H, (11)B, (31)P, and (13)C), two-dimensional [(11)B-(11)B]-COSY, and (1)H[(11)B(selective)] magnetic resonance measurements led to complete assignments of all resonances and are in excellent agreement with the structures proposed. 相似文献
63.
Josef Loczka 《Fresenius' Journal of Analytical Chemistry》1910,49(6):329-340
Ohne Zusammenfassung 相似文献
64.
Josef Bitskei 《Fresenius' Journal of Analytical Chemistry》1956,150(4):267-271
Zusammenfassung Auf Grund der Gleichung: 3 ClO– + J–=3 Cl– + JO3
– wurde eine schnelle Methode zur Bestimmung von Jodid ausgearbeitet, die wie folgt ausgeführt wird: Die 10–40 mg Jodid-Jod enthaltende Lösung wird mit etwa 0,2 g KBr, ferner mit 1,9 g H3BO3 oder 2,3 g KHCO3 versetzt, mit wenig dest. Wasser verdünnt und auf eine Temperatur von annÄhernd 50–60 C erwÄrmt. Man gibt jetzt eine überschüssige, 25 ml Thiosulfatlösung Äquivalente Menge von 0,1 n NaOCl-Lösung zu und bringt die etwas abgekühlte Lösung über freier Flamme in 4–5 sec wieder auf 50–60 C. Nach 1–1,5 minutigem Stehen setzt man 10 ml 30%ige Natronlauge und 25 ml 0,1 n Na2S2O3-Lösung (die der verwendeten NaOCl-Lösung Äquivalent sind) zu und titriert mit 0,1 n NaOCl-Lösung unter Anwendung von je 1 Tr. 1%iger alkoholischer Brasilinlösung als Indicator und 1 Tr. 5%iger KJ-Lösung als Katalysator, bis die Farbe der Lösung von rosa nach gelblichgrün umschlÄgt. Die Methode ist auch in Anwesenheit von Chlorid und Bromid anwendbar, wobei besser KHCO3 statt BorsÄure zugesetzt wird. Wird bei der Bestimmung H3BO3 verwendet, so kann die zum Endpunkt titrierte Lösung — nach Zugabe von 1–2 g KJ und nach AnsÄuern mit wenig 20%iger SchwefelsÄure — in saurem Medium mit 0,1 n Na2S2O3-Lösung weiter titriert werden. Auf diese Art kann der Jodidgehalt in einer einzigen Probe bestimmt und auch kontrolliert werden.Ich fühle mich verpflichtet, Herrn Professor Dr. Johann Proszt, dem Leiter des Institutes, meinen aufrichtigsten Dank auch an dieser Stelle auszusprechen für die Liebenswürdigkeit, womit er meine Versuche ermöglicht hat. 相似文献
65.
Josef Jankovský 《Fresenius' Journal of Analytical Chemistry》1964,201(5):325-330
Zusammenfassung In komplizierten Erzmaterialien wird Antimon mit Hilfe des Freiberger Aufschlusses in Lösung gebracht und von vielen Begleitelementen getrennt. Die Sulfosalze werden mit Wasserstoffperoxid oxydiert und Sbv danach mit Sulfit zu SbIII reduziert. Nach Zugabe von Weinsäure und ÄDTA wird Sb bei pH 9 mit Natriumdiäthyldithiocarbamidat gefällt und mit Chloroform extrahiert. Aus der organischen Phase wird Antimon(III) mit Cadmium verdrängt, rückextrahiert und in der wäßrigen Phase mit einer Jod-Maßlösung titriert.
Ein ähnliches Verfahren zur Zinkbestimmung vgl. Jankvoský, J.: diese Z. 201, 330 (1964). 相似文献
Summary For the determination of antimony in complicated ores the sample is fused with potassium carbonate and sulphur. In this way a separation from many accompanying elements is achieved. The thiosalts are oxidized by hydrogen peroxide, whereupon antimony is reduced from the quin quevalent to the trivalent state by means of sodium sulphite. After addition of tartaric acid and EDTA antimony is precipitated at pH 9 with sodium diethyldithiocarbamidate and extracted with chloroform. From the organic phase antimony is reextracted by displacement with cadmium salt and titrated with a standard iodine solution.
Ein ähnliches Verfahren zur Zinkbestimmung vgl. Jankvoský, J.: diese Z. 201, 330 (1964). 相似文献
66.
Zusammenfassung Aus potentiometrischen Daten wurde die Konstante der Entstehungsgeschwindigkeit des Zinktartrates bei 18° berechnet. Ihr durchschnittlicher Wert beträgt 1,3·102 mol·min–1 und der Wert der Zerfallsgeschwindigkeitskonstante beläuft sich im Durchschnitt auf 7,5·10–2 mol·min–1. 相似文献
67.
The shape of the steady-state three-dimensional flow velocity profile established in carrier liquid flowing inside the rectangular cross-sectional channel for field-flow fractionation should be taken into account to optimize the separation. The central parts of this profile in the planes parallel to the main channel walls are flat with almost identical flow velocities which drop down to zero at the side walls. The separated species transported by the flow in the close-to-side walls regions move with lower average velocities compared to the species transported in the central part of the channel and are undesirably broadened. The hydrodynamic splitting of the carrier liquid at the entry of the channel where the sample is injected only into the central part of the channel eliminates the excessive zone broadening. The aspect ratio of the breadth to the thickness of the channel ratio can thus be reduced. The effect of various aspect ratios on the shape of the flow velocity profile is calculated and the results are used to optimize the aspect ratio of microfluidic channels. The experiments carried out by microthermal field-flow fractionation confirmed that the aspect ratio cannot be reduced to a value of 1, proposed by other authors. 相似文献
68.
Dr. Gerd M. Ballmann Dr. Thomas X. Gentner Dr. Alan R. Kennedy Prof. Dr. Eva Hevia Prof. Dr. Robert E. Mulvey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(55):e202201716
Rare examples of heavier alkali metal manganates [{(AM)Mn(CH2SiMe3)(N‘Ar)2}∞] (AM=K, Rb, or Cs) [N‘Ar=N(SiMe3)(Dipp), where Dipp=2,6-iPr2-C6H3] have been synthesised with the Rb and Cs examples crystallographically characterised. These heaviest manganates crystallise as polymeric zig-zag chains propagated by AM⋅⋅⋅π-arene interactions. Key to their preparation is to avoid Lewis base donor solvents. In contrast, using multidentate nitrogen donors encourages ligand scrambling leading to redistribution of these bimetallic manganate compounds into their corresponding homometallic species as witnessed for the complete Li - Cs series. Adding to the few known crystallographically characterised unsolvated and solvated rubidium and caesium s-block metal amides, six new derivatives ([{AM(N‘Ar)}∞], [{AM(N‘Ar)⋅TMEDA}∞], and [{AM(N‘Ar)⋅PMDETA}∞] where AM=Rb or Cs) have been structurally authenticated. Utilising monodentate diethyl ether as a donor, it was also possible to isolate and crystallographically characterise sodium manganate [(Et2O)2Na(nBu)Mn[(N‘Ar)2], a monomeric, dinuclear structure prevented from aggregating by two blocking ether ligands bound to sodium. 相似文献
69.
Dr. Jana Hudecová Dr. Josef Kapitán Prof. Martin Dračínský Pavel Michal Dr. Václav Profant Prof. Petr Bouř 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(59):e202202045
The histidine residue has an exceptional affinity for metals, but solution structure of its complexes are difficult to study. For zinc and nickel complexes, Raman and Raman optical activity (ROA) spectroscopy methods to investigate the link between spectral shapes and the geometry were used. The spectra were recorded and interpreted on the basis of ionic equilibria, molecular dynamics, ab initio molecular dynamics, and density functional theory. For zwitterionic histidine the dominant tautomer was determined by the decomposition of experimental spectra into calculated subspectra. An octahedral structure was found to prevail for the ZnHis2 complex in solution, in contrast to a tetrahedral arrangement in the crystal phase. The solution geometry of NiHis2 is more similar to the octahedral structure found by X-ray. The Raman and ROA structural determinations of metal complexes are dependent on extensive computations, but reveal unique information about the studied systems. 相似文献
70.
Emmanouil Veroutis Steffen Merz Rüdiger-A. Eichel Josef Granwehr 《Chemphyschem》2022,23(1):e202100602
Choline-based electrolytes have been proposed as environmentally friendly and low-cost alternatives for secondary zinc air batteries. Choline acetate [Ch]+[OAc]− in protic (D2O) and aprotic (DMSO-d6) solvents has been studied by means of concentration-dependent 1H NMR, viscosity, and density measurements. The viscosities have been calculated on the basis of the Jones-Dole equation and showed that the dominant contribution originates from short-range ion-solvent interactions. Site-specific association affinities were assigned from NMR chemical shift titrations. In DMSO-d6, the hydroxyl group of choline was found to have the smallest dissociation constant followed by the methyl group of acetate. The corresponding Gibbs energies at low concentration were found to be in agreement with a solvent-separated ion pair (2SIP) configuration, whereas at concentrations above 300 mM, a solvent-shared ion pair (SIP) configuration was assigned. For [Ch]+[OAc]− in D2O, association effects were found to be weaker, attributed to the high dielectric constant of the solvent. On time scales on the order of 100 ms, NMR linewidth perturbations indicated a change in the local rotational dynamics of the ions, attributed to short-range cation-solvent interactions and not to solvent viscosity. At 184 mM, 40 % of the cations in DMSO-d6 and 10 % in D2O were found to exhibit short-range interactions, as indicated by the linewidth perturbations. It was found that at about 300 mM, the ions in DMSO-d6 exhibit a transition from free to collective translational dynamics on time scales on the order of 400 ms. In DMSO-d6, both ions were found to be almost equally solvated, whereas in D2O solvation of acetate was stronger, as indicated by the obtained effective hydrodynamic radii. For [Ch]+[OAc]− in DMSO-d6, the results suggest a solvent-shared ion association with weak H-bonding interactions for concentrations between 0.3–1 M. Overall, the extent of ion association in solvents such as DMSO is not expected to significantly limit charge transport and hinder the performance of choline-based electrolytes. 相似文献