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291.
Hashim PK Thomas R Tamaoki N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(26):7304-7312
New phototriggered molecular machines based on cyclic azobenzene were synthesized in which a 2,5‐dimethoxy, 2,5‐dimethyl, 2,5‐difluorine or unsubstituted‐1,4‐dioxybenzene rotating unit and a photoisomerizable 3,3′‐dioxyazobenzene moiety are bridged together by fixed bismethylene spacers. Depending upon substitution on the benzene moiety and on the E/Z conformation of the azobenzene unit, these molecules suffer various degrees of restriction on the free rotation of the benzene rotor. The rotation of the substituted benzene rotor within the cyclic azobenzene cavity imparts planar chirality to the molecules. Cyclic azobenzene 1 , with methoxy groups at both the 2‐ and 5‐positions of the benzene rotor, was so conformationally restricted that free rotation of the rotor was prevented in both the E and Z isomers and the respective planar chiral enantiomers were resolved. In contrast, compound 2 , with 2,5‐dimethylbenzene as the rotor, demonstrated the property of a light‐controlled molecular brake, whereby rotation of the 2,5‐dimethylbenzene moiety is completely stopped in the E isomer (brake ON, rotation OFF), while the rotation is allowed in the Z isomer (brake OFF, rotation ON). The cyclic azobenzene 3 , with fluorine substitution on the benzene rotor, was in the brake OFF state regardless of E/Z photoisomerization of the azobenzene moiety. More interestingly, for the first time, we demonstrated the induction of molecular chirality in a simple monocyclic azobenzene by circular‐polarized light. The key characteristics of cyclic azobenzene 2 , that is, stability of the chiral structure in the E isomer, fast racemization in the Z isomer, and the circular dichroism of enantiomers of both E and Z isomers, resulted in a simple reversible enantio‐differentiating photoisomerization directly between the E enantiomers. Upon exposure to r‐ or l‐circularly polarized light at 488 nm, partial enrichment of the (S)‐ or (R)‐enantiomers of 2 was observed. 相似文献
292.
Plasma waves are oscillations of electron density in time and space, and in deep submicron field effect transistors, typical plasma frequencies, ωp, lie in the terahertz (THz) range and do not involve any quantum transitions. Hence, using plasma wave excitation for detection and/or generation of THz oscillations is a very promising approach. In this paper, the investigation of plasma wave interaction between the plasma waves propagating in a short-channel High-Electron-Mobility Transistor (HEMT) and the radiated electromagnetic waves was carried out. Experimentally, we have demonstrated the detection of the terahertz (THz) radiation by an AlGaAs/GaAs HEMT up to third harmonic at room temperature and their resonant responses show very good agreement with the calculated results. 相似文献
293.
Shahizat Amir Nor Sabirin Mohamed Siti Aishah Hashim Ali 《Central European Journal of Physics》2010,8(1):150-156
Normally polymer electrolyte membranes are prepared and studied for applications in electrochemical devices. In this work,
polymer electrolyte membranes have been used as the media to culture fractals. In order to simulate the growth patterns and
stages of the fractals, a model has been identified based on the Brownian motion theory. A computer coding has been developed
for the model to simulate and visualize the fractal growth. This computer program has been successful in simulating the growth
of the fractal and in calculating the fractal dimension of each of the simulated fractal patterns. The fractal dimensions
of the simulated fractals are comparable with the values obtained in the original fractals observed in the polymer electrolyte
membrane. This indicates that the model developed in the present work is within acceptable conformity with the original fractal. 相似文献
294.
Tania Jahanbin Mansor Hashim Khamirul Amin Mantori 《Journal of magnetism and magnetic materials》2010,322(18):2684-580
The magnetic and physical properties of ferrites are very sensitive to microstructure, which in turn critically depends on the manufacturing process. In this study, nickel zinc ferrite powder with composition Ni0.8Zn0.2Fe2O4 has been prepared via conventional ceramic processing and co-precipitation methods. The toroidal and pellet form samples were sintered at various temperatures such as 1100, 1200 and 1300 °C. The microstructure, magnetic and dielectric properties of both samples were studied. The X-ray diffraction patterns confirm the formation of single-phase cubic spinel structure for the co-precipitation technique after sintering. The microstructure studies of Ni0.8Zn0.2Fe2O4 show the grain size increases and the porosity decreases with temperature for both methods. The controlled permeability with small loss and wide operational frequency range are found in the co-precipitation samples. Dielectric constants decrease with increase of frequency and increase with sintering temperature in both methods. Consequently, the homogenous microstructure with the low-loss high-performance of nickel zinc ferrite has been discovered by means of co-precipitation method. 相似文献
295.
Hao K. Shen Kiyoshi Morishita Dr. P. K. Hashim Prof. Dr. Kou Okuro Daiki Kashiwagi Ayumi Kimura Dr. Haruaki Yanagisawa Prof. Dr. Masahide Kikkawa Prof. Dr. Tatsuya Niwa Prof. Dr. Hideki Taguchi Prof. Dr. Takuzo Aida 《Angewandte Chemie (International ed. in English)》2023,62(31):e202304894
Herein, we report an ATP-responsive nanoparticle (GroELNP) whose surface is fully covered with the biomolecular machine “chaperonin protein GroEL”. GroELNP was synthesized by DNA hybridization between a gold NP with DNA strands on its surface and GroEL carrying complementary DNA strands at its apical domains. The unique structure of GroELNP was visualized by transmission electron microscopy including under cryogenic conditions. The immobilized GroEL units retain their machine-like function and enable GroELNP to capture denatured green fluorescent protein and release it in response to ATP. Interestingly, the ATPase activity of GroELNP per GroEL was 4.8 and 4.0 times greater than those of precursor cysGroEL and its DNA-functionalized analogue, respectively. Finally, we confirmed that GroELNP could be iteratively extended to double-layered NP. 相似文献