全文获取类型
收费全文 | 77篇 |
免费 | 57篇 |
国内免费 | 44篇 |
专业分类
化学 | 61篇 |
晶体学 | 3篇 |
力学 | 11篇 |
综合类 | 2篇 |
数学 | 13篇 |
物理学 | 88篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 13篇 |
2014年 | 15篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 4篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有178条查询结果,搜索用时 250 毫秒
161.
The isovalent iron chalcogenides,FeSe_(0.5)Te_(0.5) and FeS,share similar lattice structures but behave very differently in superconducting properties.We study the underlying mechanism theoretically.By first principle calculations and tightbinding fitting,we find the spectral weight of the d_(X~2-Y~2) orbital changes remarkably in these compounds.While there are both electron and hole pockets in FeSe_(0.5)Te_(0.5) and Fe S,a small hole pocket with a mainly d_(X~2-Y~2) character is absent in FeS.We find the spectral weights of d_(X~2-Y~2) orbital change remarkably,which contribute to electron and hole pockets in FeSe_(0.5)Te_(0.5) but only to electron pockets in FeS.We then perform random-phase-approximation and unbiased singular-mode functional renormalization group calculations to investigate possible superconducting instabilities that may be triggered by electron-electron interactions on top of such bare band structures.For FeSe_(0.5)Te_(0.5) ,we find a fully gapped s~±-wave pairing that can be associated with spin fluctuations connecting electron and hole pockets.For Fe S,however,a nodal dxy(or d_(x~2-y~2) in an unfolded Broullin zone)is favorable and can be related to spin fluctuations connecting the electron pockets around the corner of the Brillouin zone.Apart from the difference in chacogenide elements,we propose the main source of the difference is from the d_(X~2-Y~2) orbital,which tunes the Fermi surface nesting vector and then influences the dominant pairing symmetry. 相似文献
162.
163.
Broadband tunability of surface plasmon resonance in graphene-coating silica nanoparticles
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Graphene decorated nanomaterials and nanostructures can potentially be used in military and medical science applications. In this article, we study the optical properties of a graphene wrapping silica core–shell spherical nanoparticle under illumination of external light by using the Mie theory. We find that the nanoparticle can exhibit surface plasmon resonance(SPR) that can be broadly tuned from mid infrared to near infrared via simply changing the geometric parameters. A simplified equivalent dielectric permittivity model is developed to better understand the physics of SPR, and the calculation results agree well qualitatively with the rigorous Mie theory. Both calculations suggest that a small radius of graphene wrapping nanoparticle with high Fermi level could move the SPR wavelength of graphene into the near infrared regime. 相似文献
164.
A side band power re-injection locked(SBPRIL) magnetron is presented in this paper. A tuning stub is placed between the external injection locked(EIL) magnetron and the circulator. Side band power of the EIL magnetron is reflected back to the magnetron. The reflected side band power is reused and pulled back to the central frequency. A phase-locking model is developed from circuit theory to explain the process of reuse of side band power in SBPRIL magnetron. Theoretical analysis proves that the side band power is pulled back to the central frequency of the SBPRIL magnetron, then the amplitude of the RF voltage increases and the phase noise performance is improved. Particle-in-cell(PIC) simulation of a 10-vane continuous wave(CW) magnetron model is presented. Computer simulation predicts that the frequency spectrum's peak of the SBPRIL magnetron has an increase of 3.25 d B compared with the free running magnetron. The phase noise performance at the side band offset reduces 12.05 d B for the SBPRIL magnetron. Besides, the SBPRIL magnetron experiment is presented. Experimental results show that the spectrum peak rises by 14.29% for SBPRIL magnetron compared with the free running magnetron. The phase noise reduces more than 25 d B at 45-k Hz offset compared with the free running magnetron. 相似文献
165.
166.
This research of bidirectional pedestrian flows at signalized crosswalks is divided into two parts: model and application. In the model part, a mixed survey including the questionnaire investigation and tracking investigation is conducted to gain the basic data about walking tendentiousness of a pedestrian crossing. Then, the forward, right-hand, outstripping,and influential coefficients are outlined to quantize walking tendentiousness of pedestrian crossing and estimate transition probabilities of pedestrians. At last, an improved cellular automation model is proposed to describe walking tendentiousness and crossing behaviors of pedestrians. In the application part, channelization research of bidirectional pedestrian flows is presented for real signalized crosswalk. In this process, the effects of right-side-walking and conformity behaviors on the efficiency of pedestrian crossing are thoroughly analyzed based on simulations and experiments to obtain a final channelization method to raise the efficiency of a pedestrian crossing at the crosswalk. 相似文献
167.
超声驱动下激励参数对单泡空化振动的影响 总被引:1,自引:0,他引:1
根据考虑了液体可压缩性的改进的微气泡动力学方程,采用改进的初始半径对单泡超声空化现象进行了数值计算研究.结果表明,微气泡振动对一些参量很敏感:微气泡振动半径与初始半径的比值随振动频率的增大而减小;提高声场声压会加剧气泡崩塌程度,但过高的声压又不能使微气泡崩塌;微气泡崩塌速率随气泡初始半径的增加而增大,在一定范嘲内能保证空化泡稳定振动,在初始半径为1.6μm处空化程度最强,如果继续增大初始半径则空化程度减弱、甚至消失;微气泡崩塌程度随黏滞系数和表面张力的增大而减弱,过大的黏滞系数和表面张力会使微气泡崩塌难以发生.计算结果与他人的实验数据相比,发现液体的可压缩性使单泡空化强度增强,对最佳空化区域范围的确定有较大的影响. 相似文献
168.
在表面活性剂十六烷基三甲基溴化铵(CTAB)存在时,合成了ZnS光催化剂。 采用X射线衍射和透射电子显微镜等测试技术结果表明,制得的ZnS粒子尺寸均一,无团聚现象,平均粒径约为3.5 nm。 研究了ZnS光催化剂在紫外光下对不同染料的光催化降解效率,结果表明,ZnS光催化剂对一些含-N=N-基团的偶氮类染料,如甲基橙(MO)、酸性嫩黄(AY)、酸性橙Ⅱ(AOⅡ)光催化降解效率高达88%以上,甲基红(MR)的光催化降解效率也达59.63%。 表明-N=N-基团容易降解。 染料分子本身的吸光性也起一定的作用,虽然二甲酚橙(XO)和亚甲基蓝(MB)分子中均不含-N=N-基团,但由于XO的最大吸收峰分布于430 nm的紫外光区,其光催化降解效率可达43.83%,而MB最大吸收峰分布于664 nm可见光区,因此,其光催化降解效率则非常低。 相似文献
169.
基于势能原理,根据梁单胞在单位弯矩作用下的静力特性分析,提出了一种允许单元内
部存在材料和几何性质不连续的新的梁特征单元,称之为弯矩梁特征单元. 与已有特征单元方法、
均匀化方法和一般有限元方法进行了数值比较和分析,位移、内力和频率结果说明了弯矩梁
特征单元在精度和效率方面的优越性. 弯矩梁特征单元具有双尺度特征,为构造编织等周期
性复合材料结构的宏细观力学行为分析提供了一种思想和方法. 相似文献
170.