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91.
Ulrike Mohr 《Optics Communications》1982,41(1):21-26
The change of photon statistics of a nearly coherent single-mode light beam travelling through a saturable m-photon-amplifying or absorbing medium (m = 1, 2, …) is theoretically investigated. With the help of an approximation scheme valid for ? 1, Δn2 ? 2 ( mean value and Δn2 variance of the photon number) an analytical expression is derived for the quantity Δn2/. The results holds for arbitrary values of the initial population inversion and of the degree of saturation. It turns out that for both amplification and attenuation processes after sufficiently strong interaction Δn2/ tends to an asymptotic value. 相似文献
92.
93.
94.
A previous approximation scheme [6] which allowed to calculate, in a simple manner, the quantity Δn2/n (n mean value and Δn2 variance of the photon number) in the course of a multi-photon absorption process, is extended to study the change of the shape of the photon distribution, too. It turns out that there is a tendency to symmetrize the distribution. Moreover, an approximative expression for the asymptotic distribution to which the distribution tends after a sufficiently strong absorption, irrespective of the initial distribution, is found in form of a Gaussian. 相似文献
95.
96.
The activation of the catalytic persulphate oxidation of sulphanilic acid when the catalyst, silver(I), is suitably complexed, is discussed. 2,2'-Bipyridyl is proposed as activator as it accelerates the rate-determining step of the process-the oxidation of silver(I) to silver(II). The mechanism of activation is investigated and discussed in detail. On the basis of these investigations a catalytic method has been developed for the determination of silver(I), with a sensitivity of 4 x 10(-4)mug ml and +/-7.6% relative error. 相似文献
97.
98.
The syntheses and properties of the iodotrisilanes (IH2Si)2SiH2, (IH2Si)2SiHI, I3SiSiI2SiH3, (I3Si)2SiH2 and Si3I8 are reported. All trisilanes were synthesized from the appropriate phenyltrisilanes and hydrogen iodide, with the exception of I5Si3H3, which was prepared by thermolysis of I3SiSiH3. The 29 Si-chemical shifts and 29Si29Si-coupling constants are reported. ab]Die Synthesen und Eigenschaften der Iodtrisilane (IH2Si)2SiH2, (IH2Si)2SiHI, I3SiSiI2SiH3, (I3Si)2SiH2 und Si3I8 werden beschrieben. Bis auf I5Si3H3, das während der Thermolyse von I3SiSiH3, entstand, wurden alle Iodtrisilane aus den entsprechenden Phenyltrisilanen mit Iodwasserstoff hergestellt. Die 29Si-Verschiebungen und 29Si29Si-Kopplungskonstanten werden mitgeteilt. 相似文献
99.
Neumann H Strübing D Lalk M Klaus S Hübner S Spannenberg A Lindequist U Beller M 《Organic & biomolecular chemistry》2006,4(7):1365-1375
Corollosporine is an antimicrobial metabolite, which was isolated from the marine fungus Corollospora maritima. Owing to its basic 4-hydroxyphthalic acid anhydride structure, it has become an attractive target for a structure/activity relationship modelling of derived compounds with potential antibiotic activity. In this regard we report on the straightforward synthesis of hetero analogous corollosporines, which were easily prepared by a three-step reaction sequence, taking advantage of a novel multicomponent reaction (AAD-reaction) and a subsequent aromatization/Grignard reaction protocol. Furthermore, the obtained products were tested in several biological assays to evaluate their antimicrobial activity. 相似文献
100.
Schweizer E Hoffmann-Röder A Olsen JA Seiler P Obst-Sander U Wagner B Kansy M Banner DW Diederich F 《Organic & biomolecular chemistry》2006,4(12):2364-2375
Two series of tricyclic inhibitors of the serine protease thrombin, imides (+/-)-1-(+/-)-8 and lactams (+/-)-9-(+/-)-13, were analysed to evaluate contributions of orthogonal multipolar interactions with the backbone C=O moiety of Asn98 to the free enthalpy of protein-ligand complexation. The lactam derivatives are much more potent and more selective inhibitors (K(i) values between 0.065 and 0.005 microM, selectivity for thrombin over trypsin between 361- and 1609-fold) than the imide compounds (Ki values between 0.057 and 23.7 microM, selectivity for thrombin over trypsin between 3- and 67-fold). The increase in potency and selectivity is explained by the favorable occupancy of the P-pocket of thrombin by the additional isopropyl substituent in the lactam derivatives. The nature of the substituent on the benzyl ring filling the D pocket strongly influences binding potency in the imide series, with Ki values increasing in the sequence: F < OCH2O < Cl < H < OMe < OH < N(pyr)< Br. This sequence can be explained by both steric fit and the occurrence of orthogonal multipolar interactions with the backbone C[double bond, length as m-dash]O moiety of Asn98. In contrast, the substituent on the benzyl ring hardly affects the ligand potency in the lactam series. This discrepancy was clarified by the comparison of X-ray structures solved for co-crystals of thrombin with imide and lactam ligands. Whereas the benzyl substituents in the imide inhibitors are sufficiently close (< or =3.5 Angstroms) to the C=O group of Asn98 to allow for attractive orthogonal multipolar interactions, the distances in the lactam series are too large (> or =4 Angstroms) for attractive dipolar contacts to be effective. 相似文献