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991.
The MINDO/2 prime method is applied to the study of the force field of the benzene molecule. Force constants are recorded and compared with the data of Duinker and Mills. The wavenumbers of vibration are calculated for both perhydro and perdeuterobenzene, and the values compared with experiment. 相似文献
992.
Bis(methyl)disulphide and the organometallic compound {(Cp)Mo(CO)3}2 in low oxidation state under photolysis give especially with the hexa-fluorobut-2 yne a 18-electron olefin complexe {(Cp)Mo(CO)3(CF3C2CF3SCH3)}. The new compounds are reported and the reaction discussed. 相似文献
993.
Normal vibrational modes which are broadened by a distribution of frequencies are coherently excited via transient stimulated Raman scattering. The dephasing time of a subgroup of molecules is observed using a new selective k-vector technique. In this way, one studies the homogeneous linewidth of an inhomogeneously broadened vibrational band. Results are reported on CH-stretching modes of methanol and ethylene glycol. 相似文献
994.
A general formulation has been developed for the evaluation of the total electron spin-spin contact interaction in many-electron atoms, including both the intra- and inter-shell contributions. Calculations have been carried out, using existing analytical Hartree-Fock functions, for the positive ions, neutral systems, and negative ions for all the atoms from He to Kr.
This work has been supported in part by the National Research Council of Canada. 相似文献
Zusammenfassung Es wird ein allgemeiner Formalismus zur Berechnung der gesamten Elektronen-Spin-Spin-Kontakt-Wechselwirkung in Vielelektronen-Atomen angegeben, der sowohl die Anteile der Wechselwirkung innerhalb einer Schale als auch zwischen einzelnen Schalen berücksichtigt. Berechnungen wurden unter Benutzung vorhandener analytischer Hartree-Fock-Funktionen für die positiven Ionen, die neutralen Systeme und die negativen Ionen aller Atome von He bis Kr durchgeführt.
This work has been supported in part by the National Research Council of Canada. 相似文献
995.
Zusammenfassung Die Ionisationskonstanten des Aniliniumions, der drei Chlor- und der drei Nitroaniliniumionen in Methanol bei 2°C, 15°C und 25°C werden mit Hilfe eines spektralphotometrischen Verfahrens bestimmt. Da die Amine im ultravioletten oder im sichtbaren Bereich starke Absorptionsbanden aufweisen, während die Ionenformen fast nicht absorbieren, ist es möglich, durch Messung der Extinktion von Lösungen, in, denen Anilin (substituiertes Anilin) mit Aniliniumion (substituiertem Aniliniumion) im Gleichgewicht steht, die Ionensationskonstante zu ermitteln.Es zeigt sich, daß die Basizität der untersuchten Amine in Methanol größer als in Wasser ist und daß die Einführung eines Chloratoms oder einer Nitrogruppe in den aromatischen Ring eine Abnahme der Basizität verursacht. Dieser Effekt ist bei den Nitroanilinen stärker als bei den Chloranilinen, und bei den o-Verbindungen stärker als bei den m- und p-Verbindungen ausgeprägt.Die Temperaturabhängigkeit der Ionisationskonstanten und damit auch die Ionisationsenthalpien der Aniliniumionen sind in Methanol ebenfalls größer als in Wasser.Mit 2 AbbildungenAus der Diplomarbeit vonW. Melhardt, Technische Hochschule Wien, 1962. 相似文献
996.
R. Imhof Frl. E. Gssinger W. Graf W. Schnüriger H. Wehrli 《Helvetica chimica acta》1971,54(8):2775-2785
The preparation of the title compounds 11 , 37 , and 39 is described. 37 will serve as starting material for a partial synthesis of the steroidal alkaloid batrachotoxinin A ( 1 ). 相似文献
997.
Dimethyl-diphenyl and dimethyl-dibenzyl-silane react in liqu. NH3 in the presence of KKH2 giving rise to the formation of H2N? Si(Me2)? NH? Si(Me3)? NHK (III); exclusively C6H5 and C6H5CH2 are split off and substituted by NH2. Reaction of the potassium compound III with the equivalent amount of NH4Cl brings about a mixture of octamethylcyclotetrasilazane and hexamethylcyclotrisilazane. 相似文献
998.
999.
It is shown that depolarized and inverse polarized bands dominate the resonance Raman spectrum of heme proteins when the scattering derives its intensity from different electronic transitions (the and Soret bands), while th polarized bands dominate the spectrum when the incident light is resonant with only the strong Soret band. 相似文献
1000.
Mechanistic studies were conducted on beta-hydrogen elimination from complexes of the general formula [Ir(CO)(PPh(3))(2)(OR)], which are square planar alkoxo complexes with labile ligands. The dependence of rate, isotope effect, and alkoxide racemization on phosphine concentration revealed unusually detailed information on the reaction pathway. The alkoxo complexes were remarkably stable, including those with a variety of electronically and sterically distinct groups at the beta-carbon. These complexes were much more stable than the corresponding alkyl complexes. Thermolysis of these complexes in the presence of PPh(3) yielded the iridium hydride [Ir(CO)(PPh(3))(3)H] and the corresponding aldehyde or ketone with rate constants that were affected little by the groups at the beta-carbon. The reactions were first order in iridium complexes. At low [PPh(3)], the reaction rate was nearly zero order in PPh(3), but reactions at high [PPh(3)] revealed an inverse dependence of reaction rate on PPh(3). The rate constants were similar in toluene, THF, and chlorobenzene. The y-intercept of a 1/k(obs) vs [PPh(3)] plot displayed a primary isotope effect, indicating that the y-intercept did not simply correspond to phosphine dissociation. These data and a dependence of alkoxide racemization on [PPh(3)] showed that the elementary beta-hydrogen elimination step was reversible. A mechanism involving reversible beta-hydrogen elimination followed by associative displacement of the coordinated ketone or aldehyde by PPh(3) was consistent with all of our data. This mechanism stands in contrast with the pathways proposed recently for alkoxide beta-hydrogen elimination involving direct elimination, protic catalysts, or binuclear mechanisms and shows that alkoxide elimination can follow pathways similar to those for beta-hydrogen elimination from alkyl complexes. 相似文献