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91.
Present work focuses on the effect of swift heavy ion (SHI) irradiation of 100 MeV F7+ ions by varying the fluencies in the range of 1 × 1012 to 1 × 1013 ions/cm2 on the morphological, structural and optical properties of polycrystalline thin films of Ga10Se90-xAlx (x = 0, 5). Thin films of ~300 nm thickness were deposited on cleaned Al2O3 substrates by thermal evaporation technique. X-ray diffraction pattern of investigated thin films shows the crystallite growth occurs in hexagonal phase structure for Ga10Se90 and tetragonal phase structure for Ga10Se85Al5. The further structural analysis carried out by Raman spectroscopy and scanning electron microscopy verifies the defects or disorder of the investigated material increases after SHI irradiation. The optical parameters absorption coefficient (α), extinction coefficient (K), optical band gap (Eg) and Urbach’s energy (EU) are determined from optical absorption spectra data measured from spectrophotometry in the wavelength range 200–1100 nm. It was found that the values of absorption coefficient and extinction coefficient increase while the value of optical band gap decreases with the increase in ion fluence. This post irradiation change in the optical parameters was interpreted in terms of bond distribution model. 相似文献
92.
Experimental Techniques - In this article, the design and development of a Fiber Bragg Grating (FBG) based displacement sensor package for submicron level displacement measurements are presented. A... 相似文献
93.
The present study focuses on the effects of gamma irradiation on structural and optical properties of polycrystalline Ga10Se85Sn5 thin films with a thickness of ~300?nm deposited by the thermal evaporation technique on cleaned glass substrates. X-ray diffraction patterns of the investigated thin films show that crystallite growth occurs in the orthorhombic phase structure. The surface study carried out by using the scanning electron microscope (SEM) confirms that the grain size increases with gamma irradiation. The optical parameters were estimated from optical transmission spectra data measured from a UV–vis-spectrophotometer in the wavelength range of 200–1100?nm. The refractive index dispersion data of the investigated thin films follow the single oscillator model. The estimated values of static refractive index n0, oscillator strength Ed, zero frequency dielectric constant ε0, optical conductivity σoptical and the dissipation factor increases after irradiation, while the single oscillator energy Eo decreases after irradiation. It was found that the value of the optical band gap of the investigated thin films decreases and the corresponding absorption coefficient increases continuously with an increase in the dose of gamma irradiation. This post irradiation changes in the values of optical band gap and absorption coefficient were interpreted in terms of the bond distribution model. 相似文献
94.
K. M. Abhirami P. Matheswaran B. Gokul R. Sathyamoorthy K. Asokan 《Applied Physics A: Materials Science & Processing》2013,111(4):1175-1180
SnO2 thin films grown on glass substrates at 300 °C by reactive thermal evaporation and annealed at 600 °C were irradiated by 120 MeV Ag9+ ions. Though irradiation is known to induce lattice disorder and suppression of crystallinity, we observe grain growth at a certain fluence of irradiation. X-ray diffraction (XRD) revealed the crystalline nature of the films. The particle size estimated by Scherrer’s formula for the irradiated films was in the range 10–25 nm. The crystallite size increases with increase in fluence up to 1×1012 ions?cm?2, whereas after that the size starts decreasing. Atomic force microscope (AFM) results showed the surface modification of nanostructures for films irradiated with fluences of 1×1011 ions?cm?2 to 1×1013 ions?cm?2. The UV–visible spectrum showed the band gap of the irradiated films in the range of 3.56 eV–3.95 eV. The resistivity decreases with fluence up to 5×1012 ions?cm?2 and starts increasing after that. Rutherford Backscattering (RBS) reveals the composition of the films and sputtering of ions due to irradiation at higher fluence. 相似文献
95.
Thermal analysis of Ge20Te80−xPbx (2≤x≤8) glasses has been undertaken using modulated differential scanning calorimetry (MDSC). The compositional dependence of thermal parameters is investigated. The crystallization temperatures (Tc) estimated from the total heat flow show detectable changes at compositions x=4, 6.5 and 7.5. Further, the heat capacity change at the glass transition temperature, measured from the reversible heat flow curve (ΔCpR), is found to exhibit a maximum and an inflexion at compositions x=4 and 6.5 and minimum at x=7.5, respectively. Also, the relaxation enthalpy, estimated from the area under the non-reversing heat flow curve (ΔHNR), exhibits similar features at the said compositions. From the observed MDSC results, it has been proposed that the compositions x=4 and x=6.5 denote to the onset and completion of rigidity percolation and x=7.5 corresponds to the chemical threshold of the system. 相似文献
96.
For studies on functional genomics, small RNAs, especially microRNAs (miRNAs), have emerged as a hot topic due to their importance in cellular and developmental processes. Identification of insect miRNAs largely depends on the availability of genomic sequences in the public domain. The large milkweed bug, Oncopeltus fasciatus (Dallas) is a hemimetabolous insect which has become a model hemipteran system for various molecular studies. In this study, we identified 96 candidate mature miRNAs from O. fasciatus genome using a blast search with the previously reported animal miRNAs. The secondary structure of predicted miRNA sequences was determined online using “mfold” web server and verified by calculating the minimal free energy index (MFEI). Six miRNAs let-7e, miR-133c, miR-219b, mir-466d, mir-669f, and mir-669l are reported for the first time in Insecta. Comparison of O. fasciatus mir-2 and mir-71 family clusters to those of diverse insect species showed that they are highly conserved. The phylogenetic analysis of miRNAs revealed the evolutionary relationship of conserved miRNAs of O. fasciatus with other insect species. Using a classical rule-based algorithm method, we predicted the possible targets of the new miRNAs. Our study not only identified the list of miRNAs in O. fasciatus but also provides a basic platform for developing novel pest management strategies based on artificial miRNAs. 相似文献
97.
Abstract The electrical resistivity measurements have been carried out on bulk AsxTe100-x-ySey (30 ≤ ′ ≤ 50; 10 ≤ y ≤ 25) glasses up to 8 Gpa pressure, and temperature down to 77 K. All the As-Te-Se glasses are found to exhibit a continuous semiconductor to metal transition under pressure. However, glasses with a mean coordination number Z ≥ 2.4 show an initial plateau in resistivity, followed by a continuous decrease. This behaviour is consistent with the earlier observation on the As-Te glasses and is explained in terms of the changes in the local structure of the chalcogenide glasses with the composition. 相似文献
98.
Bulk Ge15Te85 ? xSnx and Ge17Te83 ? xSnx glasses, are found to exhibit memory type electrical switching. The switching voltages (Vt) and thermal stability of Ge15Te85 ? xSnx and Ge17Te83 ? xSnx glasses are found to decrease with Sn content. The composition dependence of Vt has been understood on the basis of the decrease in the OFF state resistance and thermal stability of these glasses with tin addition. X-ray diffraction studies reveal that no elemental Sn or Sn compounds with Te or Ge are present in thermally crystallized Ge–Te–Sn samples. This indicates that Sn atoms do not interact with the host matrix and form a phase separated network of its own, which remains in the parent glass matrix as an inclusion. Consequently, there is no enhancement of network connectivity and rigidity. The thickness dependence of switching voltages of Ge15Te85 ? xSnx and Ge17Te83 ? xSnx glasses is found to be linear, in agreement with the memory switching behavior shown by these glasses. 相似文献
99.
G. Sreevidya Varma M.S.R.N. Kiran D.V.S. Muthu U. Ramamurty A.K. Sood S. Asokan 《Journal of Non》2012,358(23):3103-3108
Nanoindentation studies on Ge15Te85 ? xInx glasses indicate that the hardness and elastic modulus of these glasses increase with indium concentration. While a pronounced plateau is seen in the elastic modulus in the composition range 3 ≤ x ≤ 7, the hardness exhibits a change in slope at compositions x = 3 and x = 7. Also, the density exhibits a broad maximum in this composition range. The observed changes in the mechanical properties and density are clearly associated with the thermally reversing window in Ge15Te85 ? xInx glasses in the composition range 3 ≤ x ≤ 7. In addition, a local minimum is seen in density and hardness around x = 9, the chemical threshold of the system. Further, micro-Raman studies reveal that as-quenched Ge15Te85 ? xInx samples exhibit two prominent peaks, at 123 cm? 1 and 155 cm? 1. In thermally annealed samples, the peaks at 120 cm? 1 and 140 cm? 1, which are due to crystalline Te, emerge as the strongest peaks. The Raman spectra of polished samples are similar to those of annealed samples, with strong peaks at 123 cm? 1 and 141 cm? 1. The spectra of lightly polished samples outside the thermally reversing window resemble those of thermally annealed samples; however, the spectra of glasses with compositions in the thermally reversing window resemble those of as-quenched samples. This observation confirms the earlier idea that compositions in the thermally reversing window are non-aging and are more stable. 相似文献
100.
Parmod Kumar Jitendra Pal Singh Yogesh Kumar Anurag Gaur Hitendra K. Malik K. Asokan 《Current Applied Physics》2012,12(4):1166-1172
The present work reports on the synthesis of the Zn1?xMgxO (x = 0, 0.02, 0.05, 0.10, 0.15 and 0.20) samples by sol–gel method and the investigations on their structural, morphological and optical properties. X-ray diffraction (XRD) data analysis confirms the formation of pure ZnO phase below 10% Mg doping and MgO related phases appears in 10% doped sample indicating that phase segregation of MgO starts at x ≥ 0.10 samples. The phase segregation observed through XRD analysis is also supported by results from Scanning Electron Microscopy (SEM), Raman spectroscopy and photoluminescence studies. Furthermore, the enhancement in optical band gap, with Mg doping, from 3.1 ± 0.1 eV to 3.5 ± 0.1 eV has been observed through UV–Vis spectroscopic analysis. Above results have been discussed on the basis of defects level observed through Raman and photoluminscence studies. 相似文献