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701.
A one-step efficacious method for the construction of a variety of substituted furano-, pyrano-, and pyrrolocoumarins and pyrroloquinolones in good to excellent yields has been developed. 相似文献
702.
SnCl4‐I2‐mediated cyclization of ortho‐cyclohexenyl phenol and ortho‐cyclohexenyl enol derivatives of coumarin, uracil, dimedone, and pyrone at room temperature for 1 h give the linear cyclized products in 78–90% yield, which, on treatment with 10% Pd‐C at 250°C for 1–2 h, afford corresponding aromatized products in 80–84% yield. 相似文献
703.
The bicyclic coumarin derivative-1, 3 propano-2-bromo-1,2-dihydro-3H-pyrano [2, 3-c] [1]benzo-pyran-5-one (8) was synthesised by a sequence of reaction viz. acetylation of 4-[2′-cyclohexenyl] -3-hydroxy [1] benzopyran-2-one (4), addition of bromine to cyclohexenyl double bond and treating the resulting acetyldi-bromo derivative (7) with 4% alcoholic KOH. Benzofuro [2, 3-c] [1] -benzopyran-6-one (10) was synthesised from 4 via oxymercuration with mercuric acetate in methanol followed by dehydrogenative damercuration with Pd-C in refluxing diphenyl ether. 相似文献
704.
Regioselective synthesis of 6a,7,8,12b‐tetrahydro‐6H‐chromeno[3,4‐c]quinolin‐6‐ones 4 in good to excellent yields from 3‐(2‐bromoanilinomethyl)coumarins 3 by aryl radical cyclization is described. The cyclization precursors 3 were prepared by the reaction of 3‐chloromethyl coumarin with different 2‐bromoaniline. 相似文献
705.
Synthesis of a number of hitherto unreported 4‐aryloxymethylene‐7‐methyl‐2,3‐dihydropyrano[3,2‐c]pyridine‐5‐ones 4a–h have been achieved in moderate yields by the thermal [3,3]sigmatropic rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐6‐methyl‐2‐pyridone. 相似文献
706.
Highly substituted indole derivatives have been prepared in good to excellent yields by a novel gold-catalyzed cyclization accompanied by [3,3]-migration of the allyl strategy. We have been able to introduce an allyl group at the C1 position of pyrano[3,2-e]indol-6(7H)-one and pyrrolo[3,2-f]quinolin-7(6H)-one moieties that provide a scope for further transformation. 相似文献
707.
Ahi S. Issever Gerd Diederichs Sharmila Majumdar Patrik Rogalla Bernd K. Hamm Axel Lange Michael Harwardt Manfred P. Hentschel Bernd R. Mueller 《Journal of synchrotron radiation》2008,15(5):525-527
Analyser‐based imaging expands the performance of X‐ray imaging by utilizing not only the absorption properties of X‐rays but also the refraction and scatter rejection (extinction) properties. In this study, analyser‐based computed tomography has been implemented on imaging an articular cartilage sample, depicting substructural variations, without overlay, at a pixel resolution of 3.6 µm. 相似文献
708.
Aggarwal MM Ahammed Z Angelis AL Antonenko V Arefiev V Astakhov V Avdeitchikov V Awes TC Baba PV Badyal SK Bathe S Batiounia B Baumann C Bernier T Bhalla KB Bhatia VS Blume C Bucher D Büsching H Carlén L Chattopadhyay S Decowski MP Delagrange H Donni P Majumdar MR El Chenawi K Dubey AK Enosawa K Fokin S Frolov V Ganti MS Garpman S Gavrishchuk O Geurts FJ Ghosh TK Glasow R Guskov B Gustafsson HA Gutbrod HH Hrivnacova I Ippolitov M Kalechofsky H Kamermans R Karadjev K Karpio K Kolb BW Kosarev I 《Physical review letters》2008,100(24):242301
Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at sqrt[S{NN}]=17.4 GeV at midrapidity (2.3 less than or approximately equal eta{lab} less than or approximately equal 3.0) over the range 0.7 less than or approximately equal p{T} less than or approximately equal 3.5 GeV/c. The spectra are compared to pi{0} spectra measured in Pb+Pb collisions at sqrt[S{NN}]=17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N{part} less than or approximately equal 300), the yield of pi{0}'s with p{T} greater than or approximately equal 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N{coll}), while for central Pb+Pb collisions with N{part}greater than or approximately equal 350, the pi{0} yield is suppressed. 相似文献
709.
Breakdown of Fourier's law in nanotube thermal conductors 总被引:1,自引:0,他引:1
We present experimental evidence that the room temperature thermal conductivity (kappa) of individual multiwalled carbon and boron-nitride nanotubes does not obey Fourier's empirical law of thermal conduction. Because of isotopic disorder, kappa's of carbon nanotubes and boron-nitride nanotubes show different length dependence behavior. Moreover, for these systems we find that Fourier's law is violated even when the phonon mean free path is much shorter than the sample length. 相似文献
710.
Padmini Sahoo Purva Chibde Satyabrata Das Subhrashis Banerjee Bhupendra P. Mali Dr. Kumar Vanka Dr. Rajesh G. Gonnade Prof. Dr. Cem. B. Yildiz Dr. Moumita Majumdar 《欧洲无机化学杂志》2023,26(29):e202300249
A 12-membered zwitterionic tetrastanna(II) cycle 1 having a crown ether-like topology has been isolated from the deprotonation of 1,1′-methylenediimidazole ( B ) with two equivalents of Sn[N(SiMe3)2]2 ( A ). The solid-state structure and NMR analysis confirms the tetrastanna(II) cycle 1 to be comprised of two stannate(II) and two stannyliumylidene ion pairs in alternating positions of the heterocycle. Computational analysis shows greater nucleophilicity at the proximally located stannate(II) centers. Nonetheless, the tetrastanna(II) cycle 1 remains poorly reactive due to engagement of SnII lone pair electrons in intramolecular donor-acceptor interactions. Simple deprotonation reaction between Sn[N(SiMe3)2]2 ( A ) and N-(diisopropylphenyl)imidazole ( C ) in equimolar ratio has led to a stannylene 2 , involving the formation of a Sn−C covalent bond with the anionic imidazol-2-yl carbon center along with the release of NH(SiMe3)2. Compound 2 exists as a dimer, where the unsubstituted ring nitrogen atom coordinated intermolecularly to the other stannylene center. 相似文献