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排序方式: 共有614条查询结果,搜索用时 15 毫秒
61.
基于石英球面弯曲晶体的X射线成像研究 总被引:1,自引:0,他引:1
为了诊断惯性约束聚变的聚爆靶的尺寸、形状、分布和均匀性等情况,利用X射线布拉格衍射理论,搭建了基于球面弯曲晶体的X射线背光成像系统。其核心元件是α-石英球面弯晶,α-石英晶体性质稳定,结构完整,反射率和分辨率高。弯曲晶体尺寸为65mm×20mm,弯曲半径为143.3mm。利用该背光成像系统进行了单色X射线背光成像实验。成像物体为3×3阵列的正方形不锈钢网格,利用接收装置磷屏成像板,得到清晰的Cr KαX射线背光源二维空间分辨,在9.6mm×28.7mm的视场范围内,其像的空间分辨率大约为83.3μm。实验结果表明α-石英球面弯曲晶体适合于X射线的背光诊断研究。 相似文献
62.
Characterizing the coating and size-resolved oxidative stability of carbon-coated aluminum nanoparticles by single-particle mass-spectrometry 总被引:1,自引:0,他引:1
Aluminum nanoparticles are of significant interest in enhancing the rate of energy release from propellants. One of the major impediments to their use is that bare aluminum is highly reactive, while oxide coated aluminum significantly decreases overall performance. We investigate creating aluminum nanoparticles with a thin carbon coating using either a laser induced plasma or a DC plasma-arc. The carbon coating was created by injecting ethylene (C2H4) directly downstream of the plasma. The elemental composition of the coated aluminum nanoparticles was measured in real time with a recently developed quantitative single particle mass spectrometer (SPMS). We found that the aluminum nanoparticles were coated with a carbon layer of thickness around 1–3 nm.The thermal and oxidative stability of these particles was determined by passing the aerosols through a heated flow reactor in a carrier flow of either air or argon, and measuring the aluminum, carbon and oxygen content in the particles with the single particle mass spectrometer. We found that below 700°C the coating was stable, but that the coating oxidized above ∼
∼800°C. In contrast the carbon coating was thermally stable above ∼
∼900°C. These results indicate that a carbon coating may be a suitable passivating agent. 相似文献
63.
64.
Joachim W. Walewski Anders Elmqvist 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,91(4):415-436
In laser-assisted combustion diagnostics it is a recurring task to predict molecular transitions whose signal strength depends only weakly on variations in temperature. The signal strength is proportional to the Boltzmann fraction of the level probed and the amplitude of the absorption line profile. In the past investigations have been presented in which this task was attack by detailed numerical calculations of the temperature dependence of pertinent physical properties of the molecule. Another widely applied approach relies on an analytical formula for the Boltzmann fraction of hetero-nuclear diatomic molecules and the neglect of line shape effects. The analytical approach experiences a continuing popularity in laser-assisted combustion diagnostics, which is why we compared both approaches with each other. The objective of this comparison was to assess the accuracy of the analytical approach and to reveal its potential pitfalls. Our comparison revealed that the analytical approach suffers from mediocre accuracy, which makes it unfit for practical applications. One cause is the neglect of higher lying vibrational levels, which show a non-negligible population for typical flame temperatures. Another reason is the neglect of fine structure splitting in molecules with non-zero orbit angular momentum in the ground state. Another reason for the observed inaccuracy is the neglect of line shape effects quenching, which were found to have a significant effect on the temperature sensitivity of a line. Because of its insufficient accuracy due to both oversimplified models of the molecular energy levels and the neglect of line shape effects and quenching we discourage from applying the analytical approach and recommend the use of detailed numerical approaches that are free of the above limitations. 相似文献
65.
本文对CCD摄象技术、等离子体诊断和脉冲辐射摄影的国内外最新发展作了评述,并涉及到在高技术领域的应用。 相似文献
66.
67.
S V Deshmukh 《Pramana》1978,11(6):755-760
The effect of Gaunt factor correction on temperature estimation over a range 100 to 1500 eV had been studied. Greene’s analytical
expression for the quantum mechanical Gaunt factor averaged over Maxwellian distribution is used. Transmission ratios are
calculated with and without Gaunt factor for various combinations of beryllium foils, taking into account x-ray emission due
to free-free transitions. A significant difference (≳ 15%) is observed between the temperatures estimated from classical and
quantum mechanical curves, above 600 eV. Selection of foil combinations useful for estimating higher temperatures is also
discussed. 相似文献
68.
T. Okada S. Inoue T. Ohga K. Muraoka M. Akazaki 《International Journal of Infrared and Millimeter Waves》1985,6(9):883-892
A D2O laser has been developed for collective Thomson scattering measurements of ion temperature in high temperature plasmas. A pulse duration and a spectral width of a high power D2O laser has been successfully controlled for this purpose, by using a TEA CO2 laser injection-locked by an etalon-tuned TEA CO2 laser as a pump source. 相似文献
69.
70.
Bertolini A Carelli G Francesconi F Francesconi M Marchesini L Marsili P Sorrentino F Cristoforetti G Legnaioli S Palleschi V Pardini L Salvetti A 《Analytical and bioanalytical chemistry》2006,385(2):240-247
Laser-induced breakdown spectroscopy (LIBS) is a promising technique for in situ elemental analysis. A new mobile instrument
for LIBS analysis, developed in a collaboration between Marwan Technology s.r.l. and the Applied Laser Spectroscopy Laboratory
in Pisa, is presented, and some applications of it and results from it are outlined. The innovative experimental set-up, based
on the use of two suitably retarded laser pulses and a standardless analysis procedure, which overcomes problems related to
matrix effects, greatly improves the potential of this technique for accurate quantitative analysis.
相似文献