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921.
Enzymatic or In Vivo Installation of Propargyl Groups in Combination with Click Chemistry for the Enrichment and Detection of Methyltransferase Target Sites in RNA
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922.
Dr. Jens Langer Dr. Andrea Hamza Dr. Imre Pápai 《Angewandte Chemie (International ed. in English)》2018,57(9):2455-2458
The synthesis of a new iridium(I) complex containing an enamido phosphine anion (dbuP?) and its unique reactivity with CO2 is reported. The complex binds two equivalents of CO2 and initiates a highly selective reaction cascade. The reaction leads to the reversible cleavage of CO2 and the enamido ligand as well. Computational analysis points to the existence of a relatively stable Ir‐CO2 complex as a reaction intermediate prior to CO2 cleavage, which was confirmed experimentally. The observed transformation resembles several aspects of enzymatic CO2 fixation by RuBisCO. 相似文献
923.
Maria Annunziata M. Capozzi Andrea Bottoni Matteo Calvaresi Cosimo Cardellicchio 《Tetrahedron》2018,74(16):2041-2047
Pentafluorobenzyl pentafluorophenyl sulfide is oxidised with moderate e.e. value and a low yield by the usually highly successful oxidation protocol based upon tert-butyl hydroperoxide (TBHP) in the presence of a titanium/hydrobenzoin complex. This disappointing result resisted until the present work, in which the switch of the oxidation agent (from TBHP to cumene hydroperoxide), suggested by our previous computations, yielded the enantiopure sulfoxide. This valuable chiral compound was obtained in good yields (76%) without resorting to a chromatographic separation. DFT computations uncovered that this favourable reactivity was originated by a stabilizing π?π?stacking between the phenyl group of the oxidant and the pentafluorophenyl moiety of the substrate. 相似文献
924.
925.
We deal with weighted inequalities of the type [formula] where: T is either the HardyLittlewood maximal operator or asingular integral operator; G is any measurable subset of Rn; f is any measurable function, vanishing outside G, such thatTf is well-defined; v and w are weights, that is, nonnegativelocally integrable functions on G; p, q(1, ). 1991 Mathematics Subject Classification 42B20, 42B25. 相似文献
926.
Mark Andrea A. de Cataldo 《Transactions of the American Mathematical Society》1997,349(6):2359-2370
We prove that there are only finitely many families of codimension two nonsingular subvarieties of quadrics which are not of general type, for and . We prove a similar statement also for the case of higher codimension.
927.
We give a complete characterization, including a Lévy–Itô decomposition, of Poincaré-invariant Markov processes on
, the relativistic phase space in 1+1 spacetime dimensions. Then, by means of such processes, we construct Poincaré-invariant Gaussian random fields, and we prove a no-go theorem for the random fields corresponding to Brownian motions on
. 相似文献
928.
Andrea Bandini 《Annali di Matematica Pura ed Applicata》1998,175(1):223-232
One of the generalizations of the Hilbert's Irreducibility Theorem states that if F(X, Y) is irreducible in
Q
p
[X, Y] then, for almost every n N, F(n, Y) is irreducible in
Q
p
[Y]. Let E{p, d} be the set of all the extensions of
Q
p
of degree d. We shall prove that for each subset S
E{p, d}there exist polynomials F(X, Y) such that the set of extensions of Q
p
generated by the roots of F (n, Y)is exactly S. Moreover we shall prove that all the functions f
are induced by polynomials F(X)
Z[X].M. S. C. N. 11S05, (11S15).The author would like to thank Prof. Roberto Dvornicich for several useful conversations and advices. 相似文献
929.
5,5-Di t-butyl-2,2-biphenyldiol (I), C20H26O2, crystallizes in the orthorhombic space group P212121 with a = 18.243(2), b = 9.947(2), c = 9.685(3) Å, and Z = 4; 5,5-dimethyl-2,2-biphenyldiol (II), C14H14O2, crystallizes in the monoclinic space group P21/c with a = 9.959(2), b = 7.932(3), c = 15.392(2) Å, = 105.43(2)°, and Z = 4. The aromatic rings are tilted by 52.7(1) and 43.8(1)° to each other in compounds (I) and (II), respectively. Strong intra- and inter-molecular H-bonds connect the molecules in the crystals. 相似文献
930.
Filtering, drying and aging of crystalline solids can affect crystalline phase(s) and therefore ex situ X-ray diffraction is not necessarily indicative of the in situ crystalline components. This paper examines some of the factors affecting the crystallised phase of aluminium hydroxides in highly caustic solutions. Caustic aluminate solutions were prepared using several different methodologies. Where solutions were prepared from aluminium metal, gibbsite and bayerite were observed to be the crystallisation products. Where gibbsite was used as the aluminium source in the liquors, the crystallised phase was found to be a function of solution conditioning. Solutions prepared at 100°C and at atmospheric pressure crystallised to form only gibbsite. These same solutions subsequently heated to 160°C for 16 h crystallised as gibbsite and bayerite. It has been concluded from these results that the caustic aluminate solutions made using gibbsite were not dissolved on the molecular scale (although optically clear) if the solutions were heated to only 100°C. Further heating at elevated temperatures completed the dissolution process so that the species in solution were similar to those found in solutions made from aluminium metal. Solutions seeded with either bayerite or gibbsite crystallised to form only gibbsite. Only crystallisation in the bulk solution and not on the seed surfaces was recorded. In some cases seeding altered the expected crystallisation products, i.e. from gibbsite and bayerite to only gibbsite. 相似文献