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71.
Mechanical properties of silicon nanobeams with an undercut evaluated by combining the dynamic resonance test and finite element analysis 下载免费PDF全文
Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications.A numerical experimental method of determining resonant frequencies and Young’s modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper.Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process,which inevitably generates the undercut of the nanobeam clamping.In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut,dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L,which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data.By using a least-square fit expression including △L,we finally extract Young’s modulus from the measured resonance frequency versus effective length dependency and find that Young’s modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon.This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm. 相似文献
72.
Mechanical properties an undercut evaluated resonance test and of silicon nanobeams with by combining the dynamic finite element analysis 下载免费PDF全文
Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications. A numerical experimental method of determining resonant frequencies and Young's modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper. Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process, which inevitably generates the undercut of the nanobeam clamping. In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut, dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L, which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data. By using a least-square fit expression including △L, we finally extract Young's modulus from the measured resonance frequency versus effective length dependency and find that Young's modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon. This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm. 相似文献
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74.
本文讨论了一类Banach空间上的非光滑半线性发展系统的时间最优控制问题,在适当的条件下证明了相应的Pontryagin型最大值原理. 相似文献
75.
稀土络合催化苯乙炔直接成膜聚合——Ⅱ.稀土聚苯乙炔膜的结构与性能 总被引:2,自引:1,他引:2
本文采用红外光谱、荧光光谱、热分析、顺磁共振、核磁共振氢谱、凝胶渗透色谱、X-射线衍射、背散射能谱、透射及扫描电子显微镜分析及测定电阻率和软化点等,对稀土聚苯乙炔膜的结构与性能进行了研究。稀土聚苯乙炔膜为高顺式结构,顺式含量在90%以上,具有高分子量,高软化点,高结晶性等特点,较其它体系有好的耐氧化性和结构稳定性,有序-无序转变温度为160℃,并有顺磁性和半导体特性,电阻率为10~(6~9)Ω·cm。本文首次获得清晰的聚苯乙炔膜电子显微图象。 相似文献
76.
Influences of surface effects and large deformation on the resonant properties of ultrathin silicon nanocantilevers 下载免费PDF全文
The purpose of the present work is to quantify the influences of the discrete nature, the surface effects, and the large deformation on the bending resonant properties of long and ultrathin 〈100〉 silicon nanocantilevers. We accomplish this by using an analytical semi-continuum Keating model within the framework of nonlinear, finite deformation kinematics. The semi-continuum model shows that the elastic behaviors of the silicon nanocantilevers are size-dependent and surface-dependent, which agrees well with the molecular dynamics results. It also indicates that the dominant effect on the fundamental resonant frequency shift of the silicon nanocantilever is adsorption-induced surface stress, followed by the discrete nature and surface reconstruction, whereas surface relaxation has the least effect. In particular, it is found that a large deformation tends to increase the nonlinear fundamental frequency of the silicon nanocantilever, depending not only on its size but also on the surface effects. Finally, the resonant frequency shifts due to the adsorption-induced surface stress predicted by the current model are quantitatively compared with those obtained from the experimental measurement and the other existing approach. It is noticed that the length-to-thickness ratio is the key parameter that correlates the deviations in the resonant frequencies predicted from the current model and the empirical formula. 相似文献
77.
影响范围计算(Incidence Calculus)理论主要是用来解决纯数值不精确推理中固有的各种难题。它具有纯数值机制所缺乏的许多优点,加它能表示命题间的独立性,具有真值函数性,而数值机制却不具有这些特点。影响范围的计算理论可以提供一种真正的概率推理。 相似文献
78.
合成了窄分子量分布低聚壳聚糖(CS20)修饰的四(4-羧基苯基)锰(Ⅱ)卟啉(Mn-TCPP)功能配合物(Mn-TCPP-CS20)作为一种潜在的磁共振成像(MRI)造影剂。发现该锰基卟啉-壳聚糖配合物(Mn-TCPP-CS20)有良好的水溶性和分子结构稳定性。通过红外(FTIR)、紫外(UV-Vis)、质谱(MS)及电感耦合等离子体发射仪(ICP-AES)对其结构进行了表征。表明,低聚壳聚糖CS20通过酰胺键与Mn-TCPP共价链接。初步研究了功能配合物Mn-TCPP-CS20作为潜在的MRI造影剂的体外弛豫性能,发现其纵向弛豫率r1 (6.11 mmol-1·l·s-1)高于商用的MRI造影剂Gd-DTPA (r1=3.59 mmol-1·l·s-1),且在同等条件下体外成像效果更优。Mn-TCPP-CS20可作为潜在的具有组织靶向性的MRI造影剂。 相似文献
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80.
介观RLC电路的量子效应 总被引:1,自引:0,他引:1
将介观电容器看作介观隧道结,对介观RLC电路作了相应的量子力学处理.研究了介观RLC电路系统的量子态演化.研究表明:考虑介观电容耦合效应的影响,介观RLC电路系统将由初始的Fock态演化到压缩Fock态,并讨论了电荷及磁通在压缩Fock态下的量子涨落. 相似文献