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811.
812.
There are not many studies on DDT with no obstacles and the initiation of DDT near the end of a closed tube. Therefore in the present study we experimentally investigate the mechanism of the combustion wave transition to a detonation wave when there are no obstacles. In particular, we show that a local explosion near the tube wall is necessary for the initiation of a detonation. Parameters that we varied are the wall configuration, distance between the ignition point and the wall, and initial filling pressure. The combustion waves and the compression waves are visualized using the Schlieren optical system. From the results, we found it is necessary for the combustion wave to reach four walls so that the detonation could be initiated by the local explosion. In the conditions of the present experiment, we exhibited that the local explosion did not occur in the vicinity of a single wall and four orthogonal walls; instead, the local explosion occurred in a situation with five orthogonal walls. The time of the local explosion and the detonation initiation is 2.6 ± 1.1 and 2.0 ± 0.1 times the characteristic time for the combustion wave to propagate hemispherically from an ignitor and reach the four walls.  相似文献   
813.
The internal behavior of fast ions interacting with magnetohydrodynamic bursts excited by energetic ions has been experimentally investigated in the compact helical system. The resonant convective oscillation of fast ions was identified inside the last closed-flux surface during an energetic-particle mode (EPM) burst. The phase difference between the fast-ion oscillation and the EPM, indicating the coupling strength between them, remains a certain value during the EPM burst and drives an anomalous transport of fast ions.  相似文献   
814.
The direct sum \({{\mathcal O}_{*}}\) of all Cuntz algebras has a non-cocommutative comultiplication \({\Delta_{\varphi}}\) such that there exists no antipode of any dense subbialgebra of the C*-bialgebra \({({\mathcal O}_{*},\Delta_{\varphi})}\). From states equations of \({{\mathcal O}_{*}}\) with respect to the tensor product, we construct an operator W for \({({\mathcal O}_{*},\Delta_{\varphi})}\) such that W* is an isometry, \({W(x\otimes I)W^{*}=\Delta_{\varphi}(x)}\) for each \({x\in {\mathcal O}_{*}}\) and W satisfies the pentagon equation.  相似文献   
815.
Optical absorption spectra of Cu2+ d–d transition peak in sodium borosilicate glasses and their melts were measured from room temperature to 1100 K. In the case of borate glass free from silicon, increase of the temperature above Tg shifts the peak position to the low energy side and decreases the peak height. Peak width is gradually increased with the increase in temperature. On the other hand, in the case of silicate glass free from boron, peak width is decreased with the increase in temperature from room temperature to liquidus temperature. In addition, peak height is slightly decreased with the temperature increase in this temperature range. Further increase of the temperature makes the peak width large. In borosilicate glasses, temperature dependence of the optical absorption spectra is different both from borate and from silicate, and the temperature dependences of the peak position and of the peak height are very small. Temperature dependence of the peak width depends on the boron/silicon ratio.  相似文献   
816.
Thermal conductivity of glass is one of the fundamental properties of it. However, that has not been studied enough. That of only less than 20 compositions has been measured below the room temperature. In this study, we measured the thermal conductivity of xNa2O · (100 ? x)SiO2 and (33 ? y)Na2O · yCs2O · 67SiO2 glasses by a transient heating method in the temperature range from about 150 K to room temperature. The conductivity of xNa2O · (100 ? x)SiO2 is found to decrease with the increase in alkali content. The dominant factor of this behavior is the decrease in phonon mean free path, which is due to the increase of non-bridge oxygen. Thermal conductivity of (33 ? y)Cs2O · yNa2O · 67SiO2 is decreased with the increase in Cs2O/(Na2O + Cs2O) ratio. The dominant factor of this behavior is the decrease of sound velocity. However, composition dependence of the phonon mean free path also affects the thermal conductivity. Phonon mean free path of 33Cs2O · 67SiO2 glass is longer than that of 33Na2O · 67SiO2 glass, and should be related to the change in distribution of structural unit in glass. In addition, phonon mean free path of mixed alkali glasses are shorter than that of single alkali glasses.  相似文献   
817.
Donor–radical acceptor systems have recently attracted much attention as efficient doublet emitters that offer significant advantages for applications such as OLEDs. We employed an alkylbenzene (mesityl group) as the simplest donor to date and added it to a diphenylpyridylmethyl radical acceptor. The (3,5-difluoro-4-pyridyl)bis[2,6-dichloro-4-(2,4,6-trimethylphenyl)phenyl]methyl radical (Mes2F2PyBTM) was prepared in only three steps from commercially available reagents. A stable radical composed of only one pyridine ring, four benzene rings, methyl groups, halogens, and hydrogens showed fluorescence of over 60% photoluminescence quantum yield (PLQY) in chloroform, dichloromethane, and PMMA. The key to high fluorescence efficiency was benzene rings perpendicular to the diphenylpyridylmethyl radical in the doublet ground (D0) state. The relatively low energy of the β-HOMO and the electron-accepting character of the radical enabled the use of benzenes as electron donors. Furthermore, the structural relaxation of the doublet lowest excited (D1) state was minimized by steric hindrance of the methyl groups. The reasons for this high efficiency include the relatively fast fluorescence transition and the slow internal conversion, both of which were explained by the overlap density between the D1 and D0 states.

By adding mesityl donors to a diphenylpyridyl radical acceptor, a highly luminescent stable radical was prepared in three steps from commercially available reagents. The photoluminescence quantum yield was as much as 69% in chloroform.  相似文献   
818.
Two krypton-chloride germicidal excimer lamp units (Care222 TRT-104C11-UI-U3, USHIO Inc.) were installed in the examination room of an ophthalmology department. The irradiation dose was set not to exceed the former (i.e., before 2022) threshold limit value (TLV) (22 mJ cm−2/8 h) recommended by the ACGIH. Section 1: The eyes and lids of the six ophthalmologists (5 wore glasses for myopic correction) who worked in the room for a mean stay of 6.7 h week−1 were prospectively observed for 12 months. Slitlamp examinations revealed neither acute adverse events such as corneal erosion, conjunctival hyperemia, and lid skin erythema nor chronic adverse events such as pterygium, cataract, or lid tumor. The visual acuity, refractive error, and corneal endothelial cell density remained unchanged during the study. Section 2: The irradiation of samples placed on the table or floor using the same fixtures in the room (5–7.5 mJ cm−2) was associated with >99% inhibition of φX174 phage and >90% inhibition of Staphylococcus aureus. In conclusion, no acute or chronic health effects in human participants was observed in a clinical setting of full-room ultraviolet germicidal irradiation by 222-nm lamp units, and high efficacy in deactivation of microorganisms was determined in the same setting.  相似文献   
819.
The stopped‐flow polymerization of propylene was carried out using an internal donor‐free MgCl2‐supported Ziegler catalyst in the absence or presence of external electron donors. The variation in the isospecific active sites was investigated based on the isotacticity distribution of the poly(propylene) analyzed by the TREF method. Highly isospecific active sites derived from the highest isotactic fraction (elution temperature by TREF: >112 °C) exist in the electron donor‐free catalyst system. The addition of external electron donors converted parts of the aspecific into isospecific active sites, but showed no effects on the highest isospecific active sites. The external electron donor sterically affects a coordination vacancy of each aspecific titanium species and, consequently, transfers it into an isospecific active site of high, but not highest isospecificity.  相似文献   
820.
The formation, variation and conversion of isospecific active sites were investigated, based on the isotacticity distribution of the polypropenes analyzed by the temperature rising elution fractionation (TREF) method. Stopped-flow polymerization of propene was carried out with a MgCl2-supported Ziegler catalyst in the absence or presence of an internal or external electron donor so that the effects and roles of the electron donors could be clarified. The results showed that various kinds of active sites with different isospecificities, including the highest isospecific active sites responsible for producing the highest isotactic fraction (elution temperature: > 112°C) existed, even in the electron donor-free catalyst system. The isospecificity of the active sites in the donor-free catalyst might have originated from a surface monolayer multinuclear titanium species, namely an “island” of titanium species. The addition of the external electron donor converted a part of the aspecific and/or low isospecific active sites into the second highest isospecific active sites, but showed no effect on the formation of the highest isospecific active sites, whereas the addition of an internal donor played an important role in creating the highest isospecific active sites as well as suppressing the formation of the aspecific active sites.  相似文献   
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