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91.
We show that for any positive integer k?4, if R is a (2k-1)×(2k-1) partial Latin square, then R is avoidable given that R contains an empty row, thus extending a theorem of Chetwynd and Rhodes. We also present the idea of avoidability in the setting of partial r-multi Latin squares, and give some partial fillings which are avoidable. In particular, we show that if R contains at most nr/2 symbols and if there is an n×n Latin square L such that δn of the symbols in L cover the filled cells in R where 0<δ<1, then R is avoidable provided r is large enough. 相似文献
92.
93.
Communications in Mathematical Physics - In recent works by Isett (Hölder continuous Euler flows in three dimensions with compact support in time, pp 1–173, 2012), and later by... 相似文献
94.
Gereon Meyer Tristan Crecelius Günter Kaindl Andreas Bauer 《Journal of magnetism and magnetic materials》2002,240(1-3):76-78
We have developed a UHV system for in situ studies of magnetic domains and magnetization reversal of thin films in the presence of external magnetic fields and at variable temperature. The system comprises a setup for magneto-optical Kerr effect measurements of magnetization curves, a Kerr-microscope for far-field magnetic-domain imaging, and a magneto-optical scanning near-field microscope in combination with a Sagnac interferometer (Sagnac-SNOM) for high-resolution imaging on a sub-μm scale. All components have successfully been tested, and the feasibility of studying ultrathin films has been demonstrated. 相似文献
95.
96.
Macroscopic fractal aggregates of cobalt are obtained by thermal evaporation of cobalt metal in an argon atmosphere and subsequent
deposition on a silicon substrate heated to 1000 K. It is established that the fractal structure is formed by diffusion-limited
aggregation of cobalt particles. The macroscopic fractal cobalt aggregates are ferromagnetic.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 556–558 (25 October 1997) 相似文献
97.
We study the method of polynomial deformations that is used in the physics literature to determine the Hodge numbers of Calabi-Yau manifolds as well as the related Yukawa couplings. We show that the argument generally presented in the literature in support of these computations is seriously misleading, give a correct proof which applies to all the cases we found in the literature, and present examples which show that the method is not universally valid. We present a general analysis which applies to all Calabi-Yau manifolds embedded as complete intersections in products of complex projective spaces, yields sufficient conditions for the validity of the polynomial deformation method, and provides an alternative computation of all the Hodge numbers in many cases in which the polynomial method fails. 相似文献
98.
Hardacre C Holbrey JD Mullan CL Nieuwenhuyzen M Youngs TG Bowron DT 《The journal of physical chemistry. B》2008,112(27):8049-8056
The liquid structure of 1-methyl-4-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, a prototypical ionic liquid containing an electron-withdrawing group on the cation, has been investigated at 368 K. Experimental neutron scattering combined with empirical potential structure refinement analysis of the data and classical molecular dynamics simulations have been used to probe the liquid structure in detail. Both techniques generated highly consistent results that provide valuable validation of the force fields and refinement approaches. A significant degree of apparent charge ordering is found in the liquid structure, although the nonspherical shape of the ions results in interpenetration of cations into the first shell of adjacent cations, with much shorter closest contact distances than the averaged center-of-mass cation-cation and cation-anion separations. 相似文献
99.
Bin Wu Tianxiao Sun Ya You Haibing Meng Dulce M. Morales Mailis Lounasvuori Abbas Beheshti Askari Li Jiang Feng Zeng Baoshan Hu Xiangzhi Zhang Renzhong Tai Zhichuan J. Xu Tristan Petit Liqiang Mai 《Angewandte Chemie (International ed. in English)》2023,62(27):e202219188
Metal/nitrogen-doped carbons (M−N−C) are promising candidates as oxygen electrocatalysts due to their low cost, tunable catalytic activity and selectivity, and well-dispersed morphologies. To improve the electrocatalytic performance of such systems, it is critical to gain a detailed understanding of their structure and properties through advanced characterization. In situ X-ray absorption spectroscopy (XAS) serves as a powerful tool to probe both the active sites and structural evolution of catalytic materials under reaction conditions. In this review, we firstly provide an overview of the fundamental concepts of XAS and then comprehensively review the setup and application of in situ XAS, introducing electrochemical XAS cells, experimental methods, as well as primary functions on catalytic applications. The active sites and the structural evolution of M−N−C catalysts caused by the interplay with electric fields, electrolytes and reactants/intermediates during the oxygen evolution reaction and the oxygen reduction reaction are subsequently discussed in detail. Finally, major challenges and future opportunities in this exciting field are highlighted. 相似文献
100.
Selmihan Sahin Olivier N. Lemaire Mélissa Belhamri Julia M. Kurth Cornelia U. Welte Tristan Wagner Ross D. Milton 《Angewandte Chemie (International ed. in English)》2023,62(45):e202311981
Massive efforts are invested in developing innovative CO2-sequestration strategies to counter climate change and transform CO2 into higher-value products. CO2-capture by reduction is a chemical challenge, and attention is turned toward biological systems that selectively and efficiently catalyse this reaction under mild conditions and in aqueous solvents. While a few reports have evaluated the effectiveness of isolated bacterial formate dehydrogenases as catalysts for the reversible electrochemical reduction of CO2, it is imperative to explore other enzymes among the natural reservoir of potential models that might exhibit higher turnover rates or preferential directionality for the reductive reaction. Here, we present electroenzymatic catalysis of formylmethanofuran dehydrogenase, a CO2-reducing-and-fixing biomachinery isolated from a thermophilic methanogen, which was deposited on a graphite rod electrode to enable direct electron transfer for electroenzymatic CO2 reduction. The gas is reduced with a high Faradaic efficiency (109±1 %), where a low affinity for formate prevents its electrochemical reoxidation and favours formate accumulation. These properties make the enzyme an excellent tool for electroenzymatic CO2-fixation and inspiration for protein engineering that would be beneficial for biotechnological purposes to convert the greenhouse gas into stable formate that can subsequently be safely stored, transported, and used for power generation without energy loss. 相似文献