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101.
Matthias HeydenreichAndreas Koch László LázárIstván Szatmári Reijo SillanpääErich Kleinpeter Ferenc Fülöp 《Tetrahedron》2003,59(11):1951-1959
Starting from the 1′- or 2′-phenyl-substituted 1-(2′-hydroxyethyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline diastereomers 3 and 6, 4-unsubstituted and 4-(p-nitrophenyl)- and 4-oxo-substituted 1-phenyl- and 2-phenyl-9,10-dimethoxy-2H,4H-1,6,7,11b-tetrahydro-1,3-oxazino[4,3-a]isoquinolines (7-12) were prepared. The relative configurations and the predominant conformations of the products were determined by NMR spectroscopy, by quantum chemical calculations and, for (2R∗,4S∗,11bR∗)-9,10-dimethoxy-4-(p-nitrophenyl)-2-phenyl-2H,4H-1,6,7,11b-tetrahydro-1,3-oxazino[4,3-a]isoquinoline (11), by X-ray diffraction. 相似文献
102.
103.
K. H. Koch und K. Ohls 《Fresenius' Journal of Analytical Chemistry》1969,247(3-4):239-243
Zusammenfassung Ein neues lösungsspektrographisches Zerstäubungsverfahren wird beschrieben, bei dem die Lösung so zerstäubt wird, daß sie die Graphitelektroden nicht berührt. Mit diesem Verfahren könnten 10–3 bis 10–5 % Al, B, Cr, Cu, Mg, Mn, Mo, Ni, Si, Sn, Ti, V und Zr in Eisen und Stahl bestimmt werden.Zur Bestimmung von Verunreinigungen oder Einschlüssen in Stahl wird ein spektrographisches Verfahren mit Preßlingselektroden empfohlen, das nur 0,1–1 mg Rückstand benötigt. Oxide von Al, B, Ca, Co, Cu, Cr, Fe, Mg, Mn, Mo, Nb, Ni, Pb, Si, Sn, Sr, Ti, V, Zn und Zr konnten bis herab zu etwa 10–7 g erfaßt werden.
Methods for the determination of trace elements from metallic samples
The principles of a new spectrographical atomizing-method of solution are described. The solution has to be atomized into a gap without contacting the surface of the graphite electrodes. In this way the exact determination of 10–3 to 10–5 % of Al, B, Cr, Cu, Mg, Mn, Mo, Ni, Si, Sn, Ti, V and Zr in iron and steel is possible.The microanalytical determination of impurities or inclusions in steel has been achieved by a spectrographical method with briquette electrodes. The necessary amount of isolation residue is only 0.1–1 mg. The oxides of Al, B, Ca, Co, Cu, Cr, Fe, Mg, Mn, Mo, Nb, Ni, Pb, Si, Sn, Sr, Ti, V, Zn and Zr can be accurately determined by this procedure. The limit of determination is about 10–7 g.相似文献
104.
O. G. Koch 《Fresenius' Journal of Analytical Chemistry》1977,286(1-2):14-19
Zusammenfassung Es wird eine automatisierte Apparatur zur schnellen, massenspektrometrischen Bestimmung von Sauerstoff und Stickstoff in Stahl beschrieben. Die Stahlprobe wird unter Argon im Gleichstrombogen geschmolzen und die extrahierten Gase Kohlenmonoxid und Stickstoff werden massenspektrometrisch bestimmt. Die relative Standardabweichung beträgt ±3–5% für Sauerstoff und ±3–8% für Stickstoff. Die Nachweisgrenzen liegen bei 10 pp106 O2 und 3 pp106 N2. Der Zeitbedarf für eine Analyse beträgt 85 s.Herrn H. Siffrin danke ich für die sorgfältige Durchführung der zahlreichen Versuche. 相似文献
105.
The optical constants in the photon energy range between 4 and 10.5 eV for E ?b on (001) and E ?L and E ⊥ L on the (010) plane are discussed. In particular the influence of macroscopic fields on the optical properties of anisotropic crystals is considered. For E ? a on the (001) plane reflection spectra have been measured at various angles of incidence. These data and results obtained recently by Hymowitz and Clark for several artificially prepared crystal faces are discussed on the basis of the frequency dependend dielectric functions. New information on the directional dispersion of exciton bands is thus obtained. 相似文献
106.
Yi SS Reichert EL Holthausen MC Koch W Weisshaar JC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(12):2232-2245
A pulsed beam of Co+(3F4) crosses a pulsed beam of C3H8 or C3D8 gas under single collision conditions at collision energies of 0.01 eV and 0.21 eV. After a variable time delay t(ext) = 1-8 micros a fast high voltage pulse extracts product ions into a field-free flight tube for mass analysis. Consistent with earlier work, we observe prompt CoC3H6+ +H2 elimination products in 3:1 excess over CoC2H4+ +CH4 products at 0.21 eV on a 2-10 micros time scale. Long-lived CoC3H8+ complexes fragment predominantly back to Co+ +C3H8 reactants and to H2 elimination products on a 6-24 micros time scale. Density functional theory (B3LYP) calculations provide energies, geometries, and harmonic vibrational frequencies at key stationary points for use in a statistical rate model of the reaction. By adjusting two key multicenter transition state (MCTS) energies downward by 4-7 kcal mol(-1), we obtain good agreement with our decay time results and with the cross section versus collision energy of Armentrout and co-workers from 0.1-1.0 eV. B3LYP theory succeeds in finding relative energies of the MCTSs leading to CH4 and H2 in the proper order to explain the different product branching ratio for Co+ (which favors H2 over CH4) compared with its nearest neighbors Fe+ and Ni+ (which favor CH4 over H2). 相似文献
107.
G. Czerwenka R. Koch und E. Scheubeck 《Fresenius' Journal of Analytical Chemistry》1976,279(4):269-273
Zusammenfassung Die Anwendung einer chloridionensensitiven Elektrode für die direktpotentiometrische Chloridbestimmung in galvanischen BÄdern wird beschrieben und eine genaue Arbeitsvorschrift sowie drei verschiedene Auswerteverfahren angegeben. Die Messungen wurden in einem Bereich von 30–250 mg Cl– je Liter Badlösung an Modellösungen durchgeführt. Die einzelnen Methoden ergaben eine Standardabweichung von ±2,1 mg bei Verwendung einer Eichkurve, ±2,2 mg beim Standardzusatzverfahren und ±3,6 mg bei der Direktablesung auf einer logarithmisch geteilten Skala eines mV-Meters. Ebenso wurden Messungen an einer Reihe von Badproben durchgeführt.Für wertvolle Anregungen und Diskussionen danken wir Herrn Schwank, Siemens AG, Abt. Informationselektronik. 相似文献
108.
Wiest O Harrison CB Saettel NJ Cibulka R Sax M König B 《The Journal of organic chemistry》2004,69(24):8183-8185
Two new artificial photolyase models that recognize pyrimidine dimers in protic and aprotic organic solvents as well as in water through a combination of charge and hydrogen-bonding interactions and use a mimic of the flavine to achieve repair through reductive photoinduced electron transfer are presented. Fluorescence and NMR titration studies show that it forms a 1:1 complex with pyrimidine dimers with binding constants of approximately 10(3) M(-1) in acetonitrile or methanol, while binding constants in water at pH 7.2 are slightly lower. Excitation of the complex with visible light leads to clean and rapid cycloreversion of the pyrimidine dimer through photoinduced electron transfer catalysis. The reaction in water is significantly faster than in organic solvents. The reaction slows down at higher conversions due to product inhibition. 相似文献
109.
C. Kelbch R. Koch S. Hagmann K. Ullmann H. Schmidt-Böcking C. O. Reinhold D. R. Schultz R. E. Olson G. Kraft 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,22(4):713-721
Double differential cross sections for the emission of Delta-electrons have been measured in fast uranium-rare gas collisions. The well-known Binary Encounter peak reveals unexpected structures for certain observation angles and its intensity increases towards smaller angles, which is in contradiction to results and scaling laws obtained by experiments with light ion impact. The observed dependencies are fairly well described by recent calculations in the framework of IA and CTMC. From systematic experimental as well as theoretical studies we can derive that the potential of the partially stripped projectile ion gives rise to rainbow and glory scattering of the target electron in the field of the projectile. The rainbow scattering is observed in the laboratory frame as pronounced interference structures, whereas the glory scattering is responsible for the steep increase of the cross sections for binary-encounter electrons towards small laboratory ejection angles. The observed effects have a dramatic influence on the commonq 2 scaling laws derived from experiments with light ions. Furthermore, since the binary-encounter electrons ejected at forward angles have approximately twice the projectile velocity, these new phenomena have an important influence on the electronic stopping power of heavy ions and therefore have to be taken into account for the investigation of radiation damage by these ions e.g. in biological matter. 相似文献
110.
2-Mercapthoethanol undergoes carbonylation in pyridine solution in the presence of oxygen and of [Ni(CO)3Pyl as a catalyst to give cyclic O, S-ethylelnethiorcarbonate. The isolation of thiolatonickel compound [Ni(SCH2CH2OH)2] by the oxidation of a solution containing [Ni(CO)3Py] and 2-mercaptoethanol, and its reaction with carbon monoxide to give the cyclic thiocarbonate and [Ni(CO)3Py] prove that the reaction proceeds in at least two steps. 相似文献