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901.
Carter JD Qu Y Porter R Hoang L Masiel DJ Guo T 《Chemical communications (Cambridge, England)》2005,(17):2274-2276
We present here the synthesis of silicon-based nanowires directly from silicon wafers at high temperatures and in the presence of cobalt nanoparticles and hydrogen gas. All three ingredients were critical to the growth of Si-based nanowires, which were between 5-60 nm in diameter and microm-mm long. Both heavily coiled and straight Si-based nanowires were made. Experimental evidence suggested that the sources of silicon for the nanowires growth were in the gas phase. 相似文献
902.
Edgar M Carter VJ Tunstall DP Grewal P Favre-Nicolin V Cox PA Lightfoot P Wright PA 《Chemical communications (Cambridge, England)》2002,(8):808-809
The structure of a novel layered aluminium methylphosphonate, formula Al2(CH3PO3)3, has been solved from laboratory X-ray powder diffraction data by simulated annealing of five independent structural sub-units, revealing a combination of four- and five-fold coordinated aluminiums within the inorganic lamellae that is unique for this kind of solid. 相似文献
903.
Bowman JM Huang X Carter S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(4):839-848
We report full dimensional calculations of vibrational energies of H3O+ and D3O+ using two implementations of the code MULTIMODE. In one implementation, the reference geometry is the minimum of the potential (the standard choice for MULTIMODE). This implementation is not able to readily describe splittings in the vibrational energies due to motion through the inversion barrier. A second implementation, in which the reference geometry is the inversion saddle point, is able to describe the splittings. These full dimensional calculations are done using the realistic, though not spectroscopically accurate, potential of Ojamae, Singer and Shavitt, and the results are compared with experiment. 相似文献
904.
[reaction: see text] Synthesis of a spirocyclization precursor with a truncated D ring has been accomplished. Subsequent bis-spirocyclization induced the formation of equal amounts of the natural transoidal 10R,13R bis-spirocycle and its cisoidal 10R,13S epimer under an apparent thermodynamically controlled process. 相似文献
905.
First-principles periodic slab density-functional theory (DFT) calculations with a plane-wave basis are used to predict the properties of S, Pt, and Hf adsorption on NiAl(1 1 0). Stable adsorption sites are identified, and adsorbate binding energies and structures are predicted. We find that while S adsorbs in a threefold site, the metals prefer to adsorb in the Ni-Ni twofold bridge site. The latter finding is consistent with scanning tunneling microscopy experiments for adsorption of various transition metals on NiAl(1 1 0) by Ho and coworkers. S is predicted to easily diffuse between threefold sites. We find that Pt and Hf both induce significant changes in the local surface structure, changing twofold bridge sites into fourfold coordination sites by drawing next-nearest-neighbor atoms nearly equidistant with the nearest-neighbor atoms. We find Pt favors interaction with Al slightly more than Ni, while Hf shows a particularly strong affinity for Ni compared to Al. We also predict that Hf may diffuse one-dimensionally along Ni rows with a barrier of ≈0.6 eV. 相似文献
906.
J. Carter A. A. Cowley H. Diesener R. W. Fearick S. V. Frtsch M. N. Harakeh J. J. Lawrie S. J. Mills P. von Neumann-Cosel R. T. Newman J. V. Pilcher A. Richter K. Schweda F. D. Smit G. F. Steyn S. Strauch D. M. Whittal 《Nuclear Physics A》1998,630(3-4)
The 40Ca(p,p′ α) reaction has been studied at an incident proton energy Ep = 99.5 MeV for proton laboratory scattering angles Θplab = 17°, 23° and 27°. Emission of α particles coincident with the scattered proton has been measured for an angular range Θα 0° − 180° relative to the recoil axis. A multipole decomposition for the α0-decay channel to the 36Ar ground state has been performed from the angular-correlation functions. The energy distribution of the dominating E2 strength deduced in the excitation energy range Ex = 11–21 MeV agrees reasonably well with the results from electron and α-induced α0-decay investigations. The exhaustion of the E2 energy-weighted sum rule in this channel up to an energy of 17 MeV is 16.1(4.0)%, in accord with the study of the (α, α′ α0) reaction. However, this value is twice what is found in the (e,e′ α0) experiment in the same energy region. Thus, the puzzling discrepancy in the E2 strengths derived from electromagnetic and hadronic probes remains unsolved. 相似文献
907.
908.
Phase shift solutions are presented at pion kinetic energies from 88 to 292 MeV where new measurements of the differential elastic cross section are available, and at 310 MeV. The resulting phase shifts are fitted to effective-range formulae. The resonant P33 phase shift is allowed to take different values for π+p and π?p scattering. There are differences in mass and width between these charge states of the resonance of M0 ? M++ = 1.4 ± 0.4 MeV/c2 and Γ0 ? Γ++ = 10.3 ± 1.3 MeV/c2. The difference in width can be accounted for largely but not entirely by the Coulomb barrier, the channel π?p → γn, and the difference in phase space between π?p → π0n and π+p → π+p. 相似文献
909.
S. H. Chen C. B. Carter P. Enquist 《Applied Physics A: Materials Science & Processing》1987,44(2):143-151
Films of GaAs, heavily doped with Sn, which have been grown by molecular-beam epitaxy are found to contain single-crystal Sn particles situated in the nearsurface region of the epilayer GaAs. The morphology and chemical composition of the particles have been examined by using cross-section transmission electron microscopy combined with energy-dispersive x-ray spectroscopy. Different growth conditions were used to study the Sn-particle formation and high-resolution transmission electron microscopy was used to investigate microstructures. The observations are discussed in terms of several models previously proposed for these phenomena. 相似文献
910.
A vanadium-catalyzed method for the oxidation of prochiral aryl, allylic selenides with tandem [2,3] sigmatropic rearrangement has been developed. This protocol has been screened on a series of substrates to test for its generality and effectiveness. The applicability of this methodology to the synthesis of enantiomerically enriched allylic alcohols has been studied on a series of chiral oxazole-containing systems with a diastereomeric ratio (d.r.) of up to 85 : 15. The chiral transfer observed in the allyl alcohol products is the result of a net 1,9- and/or 1,10-induction. Finally, the first example of a selenium-oxygen nonbonding interaction in oxazole-containing selenide appears to have been observed via X-ray crystal analysis. 相似文献