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221.
Choudary BM Sridhar C Kantam ML Venkanna GT Sreedhar B 《Journal of the American Chemical Society》2005,127(28):9948-9949
We report the preparation of recyclable heterogeneous catalysts, copper-exchanged fluorapatite, and copper-exchanged tert-butoxyapatite by incorporating basic species F-/tBuO- in apatite in situ by coprecipitation and subsequent exchange with Cu(II). These basic copper catalysts catalyzed N-arylation of imidazoles and other heterocycles with chloroarenes and electron-poor fluoroarenes in good to excellent yields. Synthesis and characterization of some of the intermediates of the catalytic cycle gave some insight into the mechanism of the very important organic transformation. The necessity of basic sites for the activation of C-Cl and C-F bonds in the N-arylation of heterocycles with haloarenes is well-established. 相似文献
222.
223.
Priyadarsi DeD.N. Sathyanarayana P. SadasivamurthyS. Sridhar 《European Polymer Journal》2002,38(5):847-855
The copolyperoxides of indene with methyl methacrylate and methacrylonitrile have been synthesized by the free-radical-initiated oxidative copolymerization of indene and the monomers. The compositions of copolyperoxides, obtained from 1H and 13C NMR spectra, have been utilized to determine the reactivity ratios. The reactivity ratios indicate that the copolyperoxides contain a large proportion of the indene units in random placement. Thermal degradation studies of the copolyperoxides by differential scanning calorimetry and electron-impact mass spectroscopy support alternating peroxide units in the copolyperoxide chain. The energy of activation for thermal degradation suggests that the degradation is controlled by the dissociation of the peroxide (-O-O-) bonds in the copolyperoxide chain. The flexibility of copolyperoxide in terms of glass transition temperature (Tg) has also been examined. 相似文献
224.
A stereoselective method for alkylation of bicyclo[2.2.2]octenones and their 3,3-sigmatropic shift leading to cis-decalins containing various types of appendages is described. A simple and convenient method for the introduction of a butenyl chain onto the bicyclooctenones employing 1,4-dibromobutane as an equivalent of 4-bromobutene, was developed. 相似文献
225.
Substituted oxazoline amines have been prepared in high yield from beta-amino alcohols and Fmoc-protected alpha-amino acids using CCl(4), PPh(3), and Hünig's base in a one-pot procedure followed by base-mediated deprotection. [reaction: see text] 相似文献
226.
227.
K. Ravikumar B. Sridhar Harihara Krishnan A. N. Singh 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(12):o653-o656
Molecules of eletriptan hydrobromide monohydrate (systematic name: (1S,2R)‐1‐methyl‐2‐{5‐[2‐(phenylsulfonyl)ethyl]‐1H‐indol‐3‐ylmethyl}pyrrolidinium bromide monohydrate), C22H27N2O2S+·Br−·H2O, (I), and naratriptan hydrochloride (systematic name: 1‐methyl‐4‐{5‐[2‐(methylsulfamoyl)ethyl]‐1H‐indol‐3‐yl}piperidinium chloride), C17H26N3O2S+·Cl−, (II), adopt conformations similar to other triptans. The C‐2 and C‐5 substituents of the indole ring, both of which are in a region of conformational flexibility, are found to be oriented on either side of the indole ring plane in (I), whilst they are on the same side in (II). The N atom in the C‐2 side chain is protonated in both structures and is involved in the hydrogen‐bonding networks. In (I), the water molecules create helical hydrogen‐bonded chains along the c axis. In (II), the hydrogen bonding of the chloride ions results in macrocyclic R42(20) and R42(24) ring motifs that form sheets in the bc plane. This structural analysis provides an insight into the molecular structure–activity relationships within this class of compound, which is of use for drug development. 相似文献
228.
K. Ravikumar B. Sridhar Harihara Krishnan A. N. Singh 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(1):o15-o17
The crystal structures of almotriptan {systematic name: N,N‐dimethyl‐2‐[5‐(pyrrolidin‐1‐ylsulfonylmethyl)‐1H‐indol‐3‐yl]ethanamine}, C17H25N3O2S, and almotriptan malate {systematic name: N,N‐dimethyl‐2‐[5‐(pyrrolidin‐1‐ylsulfonylmethyl)‐1H‐indol‐3‐yl]ethanaminium malate, C17H26N3O2S+·C4H5O5−, a novel selective serotonin 1B/D agonist, have been determined in order to gain further insight into the structure–activity relationships of triptans. The two structures differ in the orientation of their sulfonylpyrrolidine side chains. A comparison with other triptans reveals that molecules of almotriptan, sumatriptan, zolmitriptan and rizatriptan can adopt two principal conformations. N—H...N, N—H...O and O—H...O hydrogen bonds are responsible for the molecular packing. 相似文献
229.
M. Sarangapani D. Sridhar M. Arjun M. Adharvana Chari 《Journal of heterocyclic chemistry》2008,45(4):1187-1190
230.
Mintlactone is synthesized in a concise and efficient way by using a highly diastereoselective intramolecular propargylic Barbier reaction, followed by an allenol cyclocarbonylation. Tin(II) chloride is found to be the most effective reagent for the Barbier reaction. 相似文献