全文获取类型
收费全文 | 78篇 |
免费 | 0篇 |
国内免费 | 15篇 |
专业分类
化学 | 39篇 |
晶体学 | 6篇 |
力学 | 1篇 |
数学 | 2篇 |
物理学 | 20篇 |
无线电 | 25篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2017年 | 6篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 9篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
排序方式: 共有93条查询结果,搜索用时 109 毫秒
51.
Careful NMR measurements on a very lightly-doped reference silicon sample provide a convenient highly precise and accurate secondary chemical shift reference standard for 29Si MAS-NMR applicable over a wide temperature range. The linear temperature-dependence of the 29Si chemical shift measured in this sample is used to refine an earlier presentation of the paramagnetic (high-frequency) 29Si resonance shifts in heavily-doped n-type silicon samples near the metal–nonmetal transition. The data show systematic decreases of the local magnetic fields with increasing temperature in the range 100–470 K for all samples in the carrier concentration range from 2×1018 cm−3 to 8×1019 cm−3. This trend is qualitatively similar to that previously observed for the two-orders of magnitude larger 31P impurity NMR resonance shifts in the same temperature and concentration ranges. The 29Si and 31P resonance shifts are not related by a simple scaling factor, however, indicating that impurity and host nuclei are affected by different subsets of partially-localized extrinsic electrons at all temperatures. 相似文献
52.
T. Yamaguchi T. Inagawa H. Nakazumi S. Irie M. Irie 《Molecular Crystals and Liquid Crystals》2013,570(1):861-866
Abstract Photochromic chiral compounds having two diarylethene units were synthesized in an attempt to use them as dopants for photoresponsive liquid crystals. Stable photoswitching of the photochromic dopants induced large pitch changes of chiral nematic liquid crystals composed of K-15 and a small amount of the chiral dopants. 相似文献
53.
《中国化学快报》2020,31(7):1839-1842
The chemical composition obviously affects the surface wettability of a three-dimensional (3D) graphene material apart from its surface energy and microstructure. In the hydrothermal preparation, the heteroatom doping changes the chemical composition and wettability of the 3D graphene material. To realize the controllable surface wettability of graphene materials, aminobenzene sulfonic acid (ABSA) was selected as a typical doping agent for the preparation of nitrogen and sulfur co-doped 3D graphene foam (SNGF) using a hydrothermal method. Different from using o-ABSA or p-ABSA as the dopant, SNGF with tunable surface wettability is obtained only when m-ABSA is used. This result indicates that the substituent position of -SO3H group in the benzene ring of ABSA is rather important for the tunable wettability. This work provides some theoretical foundations for dopant selection and some new insights in manipulating the properties of 3D graphene foams by adjusting the configuration of dopants. 相似文献
54.
Accomplishing a superior perovskite layer with better morphology, enhanced efficiency, and improved stability is one of the great challenges to researchers. In present work, we incorporated various side chain liquid crystal polymers (SCLCP) as dopants into the perovskite precursor to attain high efficiency and long-term stability of the perovskite solar cells (PSCs). Incorporation of SCLCP increases the grain size of the crystalline perovskite film by controlled solvent evaporation, decreased the grain boundaries and reduced charge recombination, which decelerates the material degradation. With the SCLCP doping, the PSC power conversion efficiency was expressively enhanced from 17.8% (non-doped) to 19.01% for the doped perovskite film with much improved stability. Furthermore, the atomic force microscopy measurements showed a better surface roughness for doped film by effective passivation of the perovskite grain surfaces. Field emission scanning electron microscope also showed better morphology with reduced grain boundaries. Especially, the SCLCP act as bridge between the crystal grains for efficient charge transfer from perovskite layer towards the electrode, which would moderately illustrate the increased efficiency and stability. 相似文献
55.
Emerging programs in a new field of technology that employs quantum mechanical principles in engineered devices has driven new approaches to atomic-scale fabrication. Of crucial importance is the capability to configure single atoms in silicon, diamond and other materials. These engineered materials form the foundations of quantum technology which includes the fields of quantum communication and quantum computing. Quantum technology exploits quantum superposition and entanglement in potentially scalable quantum devices. To insert donor atoms in a large-scale device methods for deterministic ion implantation have been developed. These methods potentially allow the standard techniques developed for engineering materials for the Information Technology industry to be employed to make devices that exploit the new technologies. This paper reviews the emerging new technologies for deterministic doping to address the challenges of engineering atoms in the solid state. 相似文献
56.
The continuous miniaturization in the semiconductor industry brings electronic devices with higher performance at lower cost. The doping of semiconductor materials plays a crucial role in tuning the electrical properties of the materials. Ion implantation is currently widely used. Yet, this technique faces challenges meeting the requirements for smaller devices. Monolayer doping (MLD) has been proposed as one of the alternative techniques for doping semiconductors. It utilizes dopant-containing organic molecules and grafts them onto semiconductor surfaces. The dopant atoms are subsequently driven into the substrate by high temperature annealing. MLD has shown the capability for ultra-shallow doping and the doping of 3-D structures without causing crystal damage. These features make this technique a promising candidate to dope future electronic devices. In this review the processes for monolayer formation and dopant incorporation by annealing will be discussed, as well as the applications of MLD in device fabrication. 相似文献
57.
With the transition from planar to three-dimensional device architectures, devices such as FinFETs, TFETs and nanowires etc. become omnipresent. This requires the dopant atom positioning relative to the gate edges and contacts with controlled 3D distribution, adequate conformality, appropriate concentrations and activation, all of which are important challenges which need to be resolved since they determine the device performance. Developing an appropriate doping technology for the next technology generation requires a concurrent effort in establishing adequate metrology such that appropriate feedback on process steps and the underlying physics can be generated in a timely manner and with sufficient resolution and accuracy. When assessing performance of such metrology tools and concepts for 3D devices and structures, one needs to address not only the ability to achieve 3D spatial resolution, but also the physical property which is probed, i.e. dopants versus carriers, as well as the complexity of the method used because this impacts on success rate, turn-around time, throughput, automation etc. An evaluation in terms of time to data is as important as the technical capabilities.Although techniques with inherently good 3D resolution (e.g. atom probe tomography) might appear to offer the ideal solution for these applications, routine application is still hampered by localization problems during sample preparation, reconstruction artefacts due to inhomogeneous evaporation and differential laser light absorption, limited sensitivity due to the reduced counting statistics, poor tip yield, small throughput, etc. Hence, complementary analysis using 1D methods like secondary ion mass spectrometry (SIMS) are being explored to provide dopant or composition analysis in 3D structures given its high degree of reproducibility, ease of application and industrial acceptance. Targeting carrier profiling in 3D structures and confined volumes as a complement to atom probe (or SIMS) dopant profiles, has led to the extension of scanning probe microscopy (SPM) methods (which are inherently 2D) toward 3D metrology by exploiting either dedicated test structures or through novel approaches such as Scalpel SPM.The application of these SPM methods for 3D structures and confined volumes has demonstrated that the changing surface/volume ratio in confined devices leads to various phenomena (e.g. dopant deactivation, enhanced diffusion,..) which are not observed in blanket sample experiments. More emphasis should therefore be placed on the analysis of devices and structures with the relevant dimensions relative to the exploration of blanket experiments. Thus, the metrology concepts addressed in this paper may be very useful for such investigations. 相似文献
58.
Nanoscale Sb doped titanium dioxide thin films photocatalyst (Ti1-xSbO2) were obtained from dip-coating sol-gel method. The influence of dopant Sb density on the crystal structure and the phase transformation of the thin films were characterized by X-ray diffraction (XRD) and Raman spectra. The results of XRD showed that as-prepared films were not only in anatase state but also in brookite. The crystalline size was estimated to be around 13.3-20 nm. Raman spectra indicated there coexisted other phases and a transformation from brookite to anatase in the samples doped with 0.2% Sb. After doping a proper amount of Sb, the crystallization rate and the content of the anatase Ti1?xSbO2 in the thin films was clearly enhanced because Sb replaced part of the Ti of TiO2 in the thin films. The anode current density (photocurrent density) and the first order reaction speed constant (k) of thin films doped with 0.2% Sb reached 42.49 1A/cm2 and 0.171 h/cm2 under 254 nm UV illumination, respectively, which is about 11 times and 2 times that of the non-doped TiO2 anode prepared by the same method respectively. 相似文献
59.
The effects of molar concentration on ZnSe and Zr-doped ZnSe thin films were studied after successful synthesis by electrochemical technique. 0.1 M zinc tetraoxosulphate (VI) heptahydrate (ZnSO4·7H2O) and 0.1 M selenium powder respectively served as the cationic and anionic precursors while 0.1 mol% of zirconium oxidchlorid (ZrOCl2·8H2O) was used as the dopant. The morphology, structure, elemental, light response, and electrical features of the samples were studied. The films exhibited uniform distribution of spherical balls with crystalline peaks at (220), (221), (300), and (310) planes. The elemental composition of the film confirmed the deposition of as-synthesized elements. Improved optical characteristics and reduced band gap energies of the films from 2.4 eV to 2.0 eV were gotten upon the addition of zirconium. Electrical results showed increased material conductivity at increasing dopant percentages. The synthesized materials are potentially applied in optoelectronics and photovoltaics. 相似文献
60.
We investigate the stability of boron dopants near the interface between crystalline Si and amorphous SiO2 through first-principles density functional calculations. An interstitial B is found to be more stable in amorphous SiO2 than in Si, so that B dopants tend to segregate to the interface. When defects exist in amorphous SiO2, the stability of B is greatly enhanced, especially around Si floating bond defects, while it is not significantly affected near Si–Si dimers, which are formed by O-vacancy defects. 相似文献