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991.
992.
S.F. Son B.W. Asay E.M. Whitney H.L. Berghout 《Proceedings of the Combustion Institute》2007,31(2):2063-2070
There is little flame spread data for homogeneous energetic materials and no data for nitramines. We report the results of flame spread experiments of PBX 9501 (HMX (cyclotetramethylenetetranitramine) based explosive). The horizontal flame spread rate, Sf, is of the same order of magnitude as normal deflagration and varies nearly as the square root of pressure, as our scaling analysis presented here predicts. In the vertical orientation, the flame propagation downward was observed to be slightly faster than horizontal flame spread, presumably because of the melt layer flowing downward on the sample. In an accident scenario, a charge may be fractured or the surface roughened. Consequently, we also examined the effect of roughness. Minor roughness created by explosives machining was found to have a negligible affect on flame spread. However, more significant roughness can increase the rate between two and three times over normal flame spread for the conditions considered here. In addition we examine the effect of sample edges and configuration. Corners result in more favorable heat loss and therefore affect flame spread rate. We argue that the increased spread rate on edges and rough surfaces is because of favorable heat transfer convergence. 相似文献
993.
Yong-Taek Lee Changyoung Jung In-Soo Myeong Sang-Hyun Lee Jin-Seok Kim Won-Hun Ham 《Tetrahedron》2018,74(4):506-511
Stereoselective allylation of N-p-methoxyphenyl (PMP)-substituted α-hydroxy aldimines is described. Several Lewis acids (BF3·OEt2, SnCl4, TiCl4, ZnCl2, and MgBr2·OEt2) were employed to mediate the allylation reactions. The addition of the allyl group generates a new stereocenter and affords the syn vicinal amino alcohol. Formal synthesis of (?)-β-conhydrine (1) was accomplished via syn-selective allyl addition to N-PMP-substituted α-hydroxy aldimine. 相似文献
994.
A novel scheme for fast conformational search has been developed by combining the replica exchange method (REM) with the generalized effective potential concept. The new method, referred to Q-REM [S. Jang et al. Phys. Rev. Lett. 91, 058305 (2003)], is expected to provide a useful alternative to the conventional REM for effective conformational sampling of complex systems. The authors have performed folding simulations of the Trp-cage miniprotein using Q-REM. All atom level simulations with generalized Born solvent access-area solvation model show that successful folding can be observed with much smaller number of replicas in Q-REM compared to the conventional REM. It can be concluded that the new method has potential to significantly improve sampling efficiency, allowing simulations of more challenging systems. 相似文献
995.
Hoang Viet Long Nguyen Thi Kim Son Nguyen Thi My Ha Le Hoang Son 《Fuzzy Optimization and Decision Making》2014,13(4):435-462
Fuzzy hyperbolic partial differential equation, one kind of uncertain differential equations, is a very important field of study not only in theory but also in application. This paper provides a theoretical foundation of numerical solution methods for fuzzy hyperbolic equations by considering sufficient conditions to ensure the existence and uniqueness of fuzzy solution. New weighted metrics are introduced to investigate the solvability for boundary valued problems of fuzzy hyperbolic equations and an extended result for more general classes of hyperbolic equations is initiated. Moreover, the continuity of the Zadeh’s extension principle is used in some illustrative examples with some numerical simulations for \(\alpha \) -cuts of fuzzy solutions. 相似文献
996.
Doumy G Roedig C Son SK Blaga CI DiChiara AD Santra R Berrah N Bostedt C Bozek JD Bucksbaum PH Cryan JP Fang L Ghimire S Glownia JM Hoener M Kanter EP Krässig B Kuebel M Messerschmidt M Paulus GG Reis DA Rohringer N Young L Agostini P DiMauro LF 《Physical review letters》2011,106(8):083002
The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of Ne(9+) is observed at x-ray frequencies below the Ne(8+), 1s(2) absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the two-photon ionization of Ne(8+) ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross section is orders of magnitude higher than expected from previous calculations. 相似文献
997.
Kaiser AM Gray AX Conti G Son J Greer A Perona A Rattanachata A Saw AY Bostwick A Yang S Yang SH Gullikson EM Kortright JB Stemmer S Fadley CS 《Physical review letters》2011,107(11):116402
Standing-wave-excited photoemission is used to study a SrTiO3/LaNiO3 superlattice. Rocking curves of core-level and valence band spectra are used to derive layer-resolved spectral functions, revealing a suppression of electronic states near the Fermi level in the multilayer as compared to bulk LaNiO3. Further analysis shows that the suppression of these states is not homogeneously distributed over the LaNiO3 layers but is more pronounced near the interfaces. Possible origins of this effect and its relationship to a previously observed metal-insulator-transition in ultrathin LaNiO3 films are discussed. 相似文献
998.
Junho Je Jongrok Kim Massoud Kaviany Sang Young Son MooHwan Kim 《Journal of synchrotron radiation》2011,18(5):743-746
Liquid water produced in a polymer electrolyte membrane fuel cell experiences a freeze/thaw cycle when the cell is switched off and on while operating at ambient temperatures below freezing. This freeze/thaw cycle permanently deforms the polymer electrolyte membrane fuel cell capillary structures and reduces both the cell life and its ability to generate electric power. The X‐ray tomography facility at the Pohang Accelerator Laboratory was used to observe the freeze/thaw effects on the gas diffusion layer (GDL), which is the thickest capillary layer in the cell. Morphological changes in the GDL under a water freeze/thaw cycle were observed. A scenario in which freeze/thaw cycles affect fuel cell performance is suggested based on images from X‐ray tomography. 相似文献
999.
The statistical model for describing network-forming systems, developed in our previous works, is applied to study of metallic alloys with chemical bonding. The model is based on the representation of the sum of statistical weights over all possible configurations for a thermoreversible network in the form of a functional integral over a scalar field. The mean-field solution of the model is derived, and for particular case of a binary alloy having single element of chemical short-range order A2B-type, thermodynamic and structural properties have been analyzed. This analysis allows to plot the temperature-concentration phase diagram of the model representing two immiscibility gap meeting in the distectic point. It is shown that at some temperatures and concentrations, geometry percolation of the network of chemical bonds and thus a sol-gel transition may take place. The critical percolation line was plotted in common with phase diagram. Then, the structural transitions, glass-forming ability and magnetic properties of Al-R alloys are discussed in the frames of this conception. It is proposed that the range of easy glass formation is confined on the left by the minimal concentration for the sol-gel transition and on the right by the concentration corresponding to the fractal-to-Euclidian crossover in the structure of percolation cluster. Finally, the abnormal growth of Al-REM magnetic susceptibility occurring above melting point of Al2R compound is also explained. 相似文献
1000.
Hee-Wook You Jung-Woo Son Won-Ju Cho 《Applied Physics A: Materials Science & Processing》2011,102(4):921-926
In this paper, the engineered tunnel barrier technology is introduced by using the engineered tunnel barrier of VARIOT type
(SiO2/Si3N4/SiO2) and CRESTED type (Si3N4/SiO2/Si3N4) with Si3N4 and high-k HfO2 layers as charge trapping layers, respectively. In addition, the high-k stacked VARIOT type of SiO2/HfO2/Al2O3 and Al2O3/HfO2/Al2O3 are compared with O/N/O tunnel barrier memory. As a result, the engineered tunnel barrier memory device showed excellent
memory characteristics compared to the single SiO2 tunnel barrier memory device, such as very high P/E (program/erase) speed, good retention time and no degradation in endurance
characteristics. 相似文献