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Characterization of 4H-SiC substrates and epilayers by Fourier transform infrared reflectance spectroscopy 下载免费PDF全文
The infrared reflectance spectra of both 4H–SiC substrates and epilayers are measured in a wave number range from 400 cm 1 to 4000 cm 1 using a Fourier-transform spectrometer. The thicknesses of the 4H–SiC epilayers and the electrical properties, including the free-carrier concentrations and the mobilities of both the 4H–SiC substrates and the epilayers, are characterized through full line-shape fitting analyses. The correlations of the theoretical spectral profiles with the 4H–SiC electrical properties in the 30 cm 1 –4000 cm 1 and 400 cm 1 –4000 cm 1 spectral regions are established by introducing a parameter defined as error quadratic sum. It is indicated that their correlations become stronger at a higher carrier concentration and in a wider spectral region (30 cm 1 –4000 cm 1 ). These results suggest that the infrared reflectance technique can be used to accurately determine the thicknesses of the epilayers and the carrier concentrations, and the mobilities of both lightly and heavily doped 4H–SiC wafers. 相似文献
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文章主要研究对称(ITO/PZT/ITO)与非对称(Pt/PZT/ITO)势垒结构对锆钛酸铅(PZT)薄膜铁电及光伏性能的影响.实验发现,势垒对称性差异直接影响材料电滞回线,ITO/PZT/ITO结构的剩余极化强度(Pr)更大,对称性更好,饱和度更高.测试光照与暗态时两种结构Pr的变化,结果显示两种结构的Pr均增大,分析光照时Pr增大的原因,发现两种结构的漏电流在光照时均明显变大,但两种结构的净极化强度(△P)在光照时表现出差异,即对于ITO/PZT/ITO结构光照时△P基本不变,而Pt/PZT/ITO结构光照△P变小.因此得出光照时△P的变化受势垒对称性的影响,但光照时Pr的增大主要源于漏电流的增加而非△P.此外还对两种结构的光伏性能进行了研究,发现势垒的对称性同样影响材料的光伏特性,Pt/PZT/ITO结构的开路电压和短路电流密度明显高于ITO/PZT/ITO结构. 相似文献
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在机械波的教学中,学生往往会提出疑问:简谐波在介质中传播时,介质的质点究竟做什么运动?学生之所以会提出这个问题,是因为在文献[1]第25页,对机械波是这样阐述的:组成介质的质点之间有相互作用,一个质点的振动会引起相邻质点的振动.机械振动在介质中传播,形成了机械波. 相似文献
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随着高等教育不断的走向大众化,中国高等教育压力越来越大,面临着提高与普及的两方面压力。文章通过对大学物理和谐教育教学的应用研究,提出必须将和谐教育理念应用于我们大学物理的教学工作的指导中,通过和谐师生关系的创建以及对和谐教学过程的重视,实现学生高尚人格培养与知识技能掌握的和谐,培养出适应现代化要求的高素质人才。 相似文献
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The modulation of brain functional connectivity with manual acupuncture in healthy subjects:An electroencephalograph case study 下载免费PDF全文
Manual acupuncture is widely used for pain relief and stress control.Previous studies on acupuncture have shown its modulatory effects on the functional connectivity associated with one or a few preselected brain regions.To investigate how manual acupuncture modulates the organization of functional networks at a whole-brain level,we acupuncture at ST36 of a right leg to obtain electroencephalograph(EEG) signals.By coherence estimation,we determine the synchronizations between all pairwise combinations of EEG channels in three acupuncture states.The resulting synchronization matrices are converted into functional networks by applying a threshold,and the clustering coefficients and path lengths are computed as a function of threshold.The results show that acupuncture can increase functional connections and synchronizations between different brain areas.For a wide range of thresholds,the clustering coefficient during acupuncture and postacupuncture period is higher than that during the pre-acupuncture control period,whereas the characteristic path length is shorter.We provide further support for the presence of "small-world" network characteristics in functional networks by using acupuncture.These preliminary results highlight the beneficial modulations of functional connectivity by manual acupuncture,which could contribute to the understanding of the effects of acupuncture on the entire brain,as well as the neurophysiological mechanisms underlying acupuncture.Moreover,the proposed method may be a useful approach to the further investigation of the complexity of patterns of interrelations between EEG channels. 相似文献
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High-performance 4H-SiC junction barrier Schottky diodes with double resistive termination extensions 下载免费PDF全文
4H-SiC junction barrier Schottky (JBS) diodes with a high-temperature annealed resistive termination extension (HARTE) are designed, fabricated and characterized in this work. The differential specific on-state resistance of the device is as low as 3.64 m ·cm2 with a total active area of 2.46×10-3 cm2 . Ti is the Schottky contact metal with a Schottky barrier height of 1.08 V and a low onset voltage of 0.7V. The ideality factor is calculated to be 1.06. Al implantation annealing is performed at 1250℃ in Ar, while good reverse characteristics are achieved. The maximum breakdown voltage is 1000 V with a leakage current of 9×10-5 A on chip level. These experimental results show good consistence with the simulation results and demonstrate that high-performance 4H-SiC JBS diodes can be obtained based on the double HARTE structure. 相似文献
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