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81.
This paper reports the performance of our modified adaptive optics system for solar observations. This system operates at a frame rate of about 400 Hz and has the closed-loop cutoff frequency at 105 Hz. The results of the laboratory experiments show that this system compensates for a temporal wavefront-variation of less than 99 Hz and improves the Strehl ratio by a factor of five.  相似文献   
82.
Stellar speckle spectroscopy is a speckle interferometric method enabling us to separate point by point spectra on a stellar object with a diffraction-limited spatial resolution of a telescope. We describe observational results obtained with our system for speckle spectroscopy. Data of two binary stars, of which separations are closer than seeing disc, were taken and processed by cross-correlation method. In each object, spectral images of two component stars around the Hα line (656.3 nm) were spatially resolved with nearly diffraction-limited resolution. The separated spectra of ADS940 reveal different spectral types of the component stars. These results demonstrate the ability of the speckle spectroscopic method.Presented at the International Commission of Optics Topical Meeting, Kyoto, 1994.  相似文献   
83.
We have studied simple empirical equations to estimate light absorption loss αv due to harmonics of molecular vibrations of transparent amorphous polymers used in plastic optical fibers (POFs). In the visible region, absorption involves two losses. One is αv, and the other is the electronic transition absorption loss, αe. Of the two, αv is considerably larger than αe in the wavelength region used for optical communication with POFs. We have clarified relationships between chemical structure of repeat units of polymers and αv. We find that αv is proportional to the concentration of specific chemical bonds (C? H, N? H, and Obond;H bonds) in the polymer solid, and we propose empirical equations to estimate αv from the polymer density and the chemical structure of the repeat unit. These equations are used to estimate αv of several polymers [i.e., poly(methyl methacrylate), polystyrene, and polycarbonate]. The estimated values are nearly equal to the experimental or reference values. Furthermore, to minimize the attenuation in the POF, we conclude that the POF core polymer should have no N? H, O? H, or aliphatic C? H bonds in its repeat unit.  相似文献   
84.

Background  

The irregular formation of cytoskeletal fibers in spaceflown experimental cells has been observed, but the disorganization process of fibers is still poorly understood. It is well known that the activation of the small GTPase Rho leads to actin stress fibers assembly. This study was performed to evaluate the effect of simulated microgravity on the activation of Rho that is involved in actin fiber remodeling in cells.  相似文献   
85.
The limiting molar conductances ° of potassium deuteroxide KOD in D2O and potassium hydroxide KOH in H2O were determined at 5 and 45°C as a function of pressure to clarify the difference in the temperature, pressure and isotope effects on the proton jump between an OD (OH) and a D3O+ (H3O+) ion. The excess conductances of the OD ion in D2O and the OH ion in H2O, E 0 (OD-) and E 0 (OH-), increase with increasing temperature and pressure as in the case of the excess deuteron and proton conductances, E 0 (D+) and E 0 (H+). However, the temperature effect on the excess conductance is larger for the OD(OH) ion than for the D3O+ (H3O+) ion but the pressure effect is much smaller for the OD (OH) ion than for the D3O+ (H3O+) ion. These findings are correlated with larger activation energies and less negative activation volumes found for the OD (OH) ion than for the D3O+ (H3O+) ion. Concerning the isotope effect, the value of E 0 (OH-)/ E 0 (OD-) deviates considerably from at each temperature and pressure in contrast with that of E 0 (H+)/ E 0 (D+), although both of them decrease with increasing temperature and pressure. These results are discussed mainly in terms of the difference in repulsive force between the OD (OH) or the D3O+ (H3O+) ion and the adjacent water molecule, the difference in strength of hydrogen bonds in D2O and H2O, and their variations with temperature, pressure, and isotope.  相似文献   
86.
The electroreduction of chiral aromatic alpha-imino esters prepared from (S)-alpha-amino acids, such as (S)-valine, (S)-leucine, and (S)-phenylalanine, in the presence of chlorotrimethylsilane and triethylamine afforded four-membered cyclized products, mixed ketals of cis-2,4-disubstituted azetidine-3-ones, stereospecifically (>99% de, 85-99% ee). The best result of the electroreductive cyclization was obtained using Bu(4)NClO(4) as a supporting electrolyte and a Pt cathode. The absolute stereochemistry of the obtained single stereoisomers was confirmed to be 2R,3R,4S by X-ray crystallography. Calculations for the transition states of the cyclization support the stereospecific formation of the (2R,3R,4S)-isomers.  相似文献   
87.
p-Isopropenylphenyl glycidyl ether (IPGE), a monomer of dual cationic functionality (isopropenyl and epoxy), was polymerized by a variety of initiators, and optimum conditions were established for its selective vinyl cationic polymerization. The hydrogen iodide/iodine (HI/I2) initiating system or iodine polymerized selectively the isopropenyl group in CH2Cl2 at a low temperature (?78°C), to produce soluble poly(IPGE) with epoxy pendants. Under these conditions, the number-average molecular weight of the polymers was inversely proportional to the initial initiator concentration, indicating the formation of long-lived propagating species. Soluble poly(IPGE) was also obtained at ?15 and ?40°C by HI/I2 or iodine. However, at these higher temperatures, transfer and/or termination reactions took place to give olefin-terminated polymers, in which some of the pendant epoxy groups were consumed. BF3OEt2 (a metal halide) and CF3SO3H (a strong protonic acid) polymerized both epoxy and isopropenyl groups of IPGE and yielded crosslinked insoluble polymers.  相似文献   
88.
To confirm the surface activity of myristic acid in the dispersion polymerization of vinyl monomers in scCO2, the interfacial tension (IFT) at the polymer/supercritical carbon dioxide (scCO2) interface has been measured. For the IFT measurements, a high-pressure pendant drop apparatus was constructed. The IFT data was obtained by the axisymmetric drop shape analysis of melt polymer droplets formed at the tip of a capillary. The reliability of the apparatus was confirmed by measuring the IFT of polystyrene (PS)/scCO2 and polypropylene (PP)/CO2 systems. The IFT of the poly(methyl methacrylate) (PMMA)/scCO2 system with and without myristic acid was also measured. The IFT decreased on addition of myristic acid. The magnitude of the IFT depression due to the myristic acid was comparable to that of PS/scCO2 systems with the block copolymer surfactant, PS-b-poly(fluorooctyl acrylate). The surface activity of the myristic acid was confirmed by the decrease of IFT.  相似文献   
89.
Synthetic utility of microreactors and highly stereoselective isomerization (>99:<1) of terminal difluoromethylated alkenes to (E)-difluoromethylated alkenes with TBAF in DMF, are described.  相似文献   
90.
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