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931.
932.
933.
Coe BJ Jones LA Harris JA Brunschwig BS Asselberghs I Clays K Persoons A 《Journal of the American Chemical Society》2003,125(4):862-863
We have used several techniques, including hyper-Rayleigh scattering and Stark spectroscopy, to investigate the effects of polyene chain length on the optical properties of complexes containing ruthenium(II) electron donor groups and pyridinium electron acceptors. In marked contrast with all other known donor-acceptor polyenes, conjugation extension beyond a single double bond in the dipolar complexes studied leads to blue-shifting of the intramolecular charge-transfer absorptions. Furthermore, the static first hyperpolarizabilities beta0 become maximized with trans-1,3-butadienyl linkages and then decrease in complexes with three CH=CH bonds. Our results clearly demonstrate that the molecular engineering criteria for metal-containing nonlinear optical chromophores can differ dramatically from those for purely organic compounds. 相似文献
934.
Coe BJ Jones LA Harris JA Brunschwig BS Asselberghs I Clays K Persoons A Garín J Orduna J 《Journal of the American Chemical Society》2004,126(12):3880-3891
In this paper, we describe the extremely unusual optical properties of Ru(II)-based electron donor-acceptor (D-A) polyene and some closely related chromophores. For three different polyene series, the intense, visible d-->pi* metal-to-ligand charge-transfer bands unexpectedly blue-shift as the number of E-ethylene units (n) increases from 1 to 3, and the static first hyperpolarizabilities beta(0) determined via hyper-Rayleigh scattering and Stark spectroscopy maximize at n = 2, in marked contrast to other known D-A polyenes in which beta(0) increases steadily with n. Time-dependent density-functional theory and finite field calculations verify these empirical trends, which arise from the orbital structures of the complexes. This study illustrates that transition metal-based nonlinear optical chromophores can show very different behavior when compared with their more thoroughly studied purely organic counterparts. 相似文献
935.
Several polymethyl-1,10-phenanthrolines were synthesized by the use of 3-methyl-3-penten-2-one in Skraup reactions. The behavior of this ketone as well as that of 4-hydroxy-2-pentanone and 4-hydroxy-3-methyl-2-bulanone with various substituted anilines was studied. 相似文献
936.
The reactivity of the (PPN)2[Fe8S6(NO)8] and (PPN)2[Fe6S6(NO)6] clusters is explored and new derivative clusters have been synthesized and structurally characterized. The unique (PPN)2Fe4S4(NO)6 “open-cubane” cluster with a chair like Fe4S4 core is obtained along with the mixed metal pentandite-like clusters (PPN)2[Mo2Fe6S6(NO)6(CO)6], (PPr3)2Cu2Fe6S6(NO)6, (PPr3)4Cu4Fe4S6(NO)4, (PPr3)2Ni2Fe6S6(NO)6, (PPr3)3Ni3Fe4S6(NO)4. The rich electrochemistry of the mixed metal clusters is presented as well. 相似文献
937.
Carl B. Ziegler Nydia A. Kuck Sonja M. Harris Yang-I Lin 《Journal of heterocyclic chemistry》1988,25(5):1543-1546
1-Ethyl-6-fluoro-7-hydrazino-1,4-dihydro-4-oxoquinoline-3-carboxylic acid ( 8 ) has been prepared and served as a versatile intermediate from which a number of hydrazone, pyrazole and dihydropyridazine derivatives were synthesized. The in vitro biological activity of some of these derivatives is reported. 相似文献
938.
The total synthesis of the indole alkaloid (±) 20-epiuleine has been achieved starting from indole itself and the appropriate 2-cyano Δ3 piperidine . 相似文献
939.
Coe BJ Harris JA Brunschwig BS Garín J Orduna J Coles SJ Hursthouse MB 《Journal of the American Chemical Society》2004,126(33):10418-10427
In this article, we contrast the optical properties of dipolar chromophores having 4-(dimethylamino)phenyl electron donor (D) and pyridinium acceptor (A) groups with those of closely related cations having pyridyl-coordinated Ru(II) donors. A range of physical data, including that from Stark (electroabsorption) spectroscopy, permits unprecedented quantitative comparisons, most notably regarding the effects of extension of bridging polyene chains. The purely organic compounds display normal optical properties in that their intense, visible pi --> pi intramolecular charge-transfer (ICT) bands red-shift as the number of E-ethylene units (n) increases from 1 to 3 and the associated static first hyperpolarizabilities beta(0) increase steadily with n. The related Ru(II) complexes show intense, visible d --> pi metal-to-ligand charge-transfer (MLCT) bands, which are found to lower energy when compared with the ICT transitions of the corresponding organics. Abnormally, these MLCT bands blue-shift as n increases, and beta(0) maximizes at n = 2. Time-dependent density-functional theory and finite field calculations verify these empirical trends for both types of compound, which can be rationalized as arising from the differing orbital structures of the chromophores and the associated degrees of D-A electronic coupling. 相似文献
940.
Ritalin, [(+)-threo]methylphenidate hydrochloride, is a chiral drug substance with two chiral centers. The drug substance may contain three pairs of enantiomers, [(+)-threo], [(-)-threo], [(+)-erythro] and [(-)-erythro] isomers, and its degradation products, threoritalinic acid racemate. Determination of the optical purity of ritalin drug substance and the amount of its by-product isomers is a critical step in the single-isomer drug development. In order to efficiently recognize the three pairs of enantiomers by one method, capillary electrophoresis (CE) was employed for the separation. The three pairs of enantiomers in CE showed different enantioselectivities with eight different types of CDs. Only 2,6-di-o-methyl-beta-cyclodextrin (DM-beta-CD) and carboxymethyl-beta-cyclodextrin (CM-beta-CD) showed enantioselectivity to all these pairs of enantiomers. With respect to separation resolution and efficiency, DM-beta-CD was chosen as the chiral selector. For optimization of the separation conditions, the concentration of DM-beta-CD, pH of the buffer solution, and temperature of the capillary were further studied. 相似文献