全文获取类型
收费全文 | 33545篇 |
免费 | 5485篇 |
国内免费 | 17652篇 |
专业分类
化学 | 36662篇 |
晶体学 | 954篇 |
力学 | 1620篇 |
综合类 | 1010篇 |
数学 | 4808篇 |
物理学 | 11628篇 |
出版年
2024年 | 202篇 |
2023年 | 1061篇 |
2022年 | 1178篇 |
2021年 | 1217篇 |
2020年 | 1191篇 |
2019年 | 1589篇 |
2018年 | 1057篇 |
2017年 | 1524篇 |
2016年 | 1710篇 |
2015年 | 1817篇 |
2014年 | 2668篇 |
2013年 | 2836篇 |
2012年 | 2986篇 |
2011年 | 2784篇 |
2010年 | 2666篇 |
2009年 | 2925篇 |
2008年 | 3328篇 |
2007年 | 3064篇 |
2006年 | 3294篇 |
2005年 | 2900篇 |
2004年 | 3042篇 |
2003年 | 2044篇 |
2002年 | 1250篇 |
2001年 | 1236篇 |
2000年 | 1066篇 |
1999年 | 1109篇 |
1998年 | 671篇 |
1997年 | 487篇 |
1996年 | 461篇 |
1995年 | 400篇 |
1994年 | 422篇 |
1993年 | 442篇 |
1992年 | 466篇 |
1991年 | 449篇 |
1990年 | 362篇 |
1989年 | 338篇 |
1988年 | 228篇 |
1987年 | 96篇 |
1986年 | 41篇 |
1985年 | 34篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1980年 | 1篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
3.
Majorana fermions induced fast-and slow-light in a hybrid semiconducting nanowire/superconductor device 下载免费PDF全文
We investigate theoretically Rabi-like splitting and Fano resonance in absorption spectra of quantum dots(QDs)based on a hybrid QD-semiconducting nanowire/superconductor(SNW/SC)device mediated by Majorana fermions(MFs).Under the condition of pump on-resonance and off-resonance,the absorption spectrum experiences the conversion from Fano resonance to Rabi-like splitting in different parametric regimes.In addition,the Fano resonances are accompanied by the rapid normal phase dispersion,which will indicate the coherent optical propagation.The results indicate that the group velocity index is tunable with controlling the interaction between the QD and MFs,which can reach the conversion between the fast-and slow-light.Fano resonance will be another method to detect MFs and our research may indicate prospective applications in quantum information processing based on the hybrid QD-SNW/SC devices. 相似文献
4.
5.
6.
7.
CdS/Si nanofilm heterojunctions based on amorphous silicon films:Fabrication,structures,and electrical properties 下载免费PDF全文
Shortening the distance between the depletion region and the electrodes to reduce the trapped probability of carriers is a useful approach for improving the performance of heterojunction.The CdS/Si nanofilm heterojunctions are fabricated by using the radio frequency magnetron sputtering method to deposit the amorphous silicon nanofilms and Cd S nanofilms on the ITO glass in turn.The relation of current density to applied voltage(I-V)shows the obvious rectification effect.From the analysis of the double logarithm I-V curve it follows that below~2.73 V the electron behaviors obey the Ohmic mechanism and above~2.73 V the electron behaviors conform to the space charge limited current(SCLC)mechanism.In the SCLC region part of the traps between the Fermi level and conduction band are occupied,and with the increase of voltage most of the traps are occupied.It is believed that Cd S/Si nanofilm heterojunction is a potential candidate in the field of nano electronic and optoelectronic devices by optimizing its fabricating procedure. 相似文献
8.
First-principles study of the co-effect of carbon doping and oxygen vacancies in ZnO photocatalyst 下载免费PDF全文
Although tuning band structure of optoelectronic semiconductor-based materials by means of doping single defect is an important approach for potential photocatalysis application,C-doping or oxygen vacancy(Vo)as a single defect in ZnO still has limitations for photocatalytic activity.Meanwhile,the influence of co-existence of various defects in ZnO still lacks sufficient studies.Therefore,we investigate the photocatalytic properties of ZnOx C0.0625(x=0.9375,0.875,0.8125),confirming that the co-effect of various defects has a greater enhancement for photocatalytic activity driven by visible-light than the single defect in ZnO.To clarify the underlying mechanism of co-existence of various defects in ZnO,we perform systematically the electronic properties calculations using density functional theory.It is found that the coeffect of C-doping and Vo in ZnO can achieve a more controllable band gap than doping solely in ZnO.Moreover,the impact of the effective masses of ZnOxC0.0625(x=0.9375,0.875,0.8125)is also taken into account.In comparison with heavy Vo concentrations,the light Vo concentration(x=0.875)as the optimal component together with C-doping in ZnO,can significantly improve the visible-light absorption and benefit photocatalytic activity. 相似文献
9.
采用溶剂热法,1,3,5-三(羧基甲氧基)苯为定向配体和乙酸镍反应构筑了一个新型的金属配位聚合物[Ni(TB)2(H2O)2]n·2H2O,其中H3TB=1,3,5-三(羧基甲氧基)苯,通过元素分析、IR及X射线单晶衍射对配合物结构进行表征,并研究其荧光性质、热稳定性及Hirshfeld表面作用力。单晶结构分析表明,该配合物属于三斜晶系,空间群$P \overline{1}$,配合物中心离子Ni(Ⅱ)分别与来自两个水分子上的氧原子及四个不同1,3,5-三(羧基甲氧基)苯配体的羧酸氧原子配位,形成六配位的NiO6八面体构型,并通过与1,3,5-三(羧基甲氧基)苯配体的氧原子配位不断延伸形成具有孔洞结构的一维链状构型。配合物具有良好的荧光性能和热稳定性。Hirshfeld表面作用分析表明配合物分子中O…H/H…O作用占主导且占比为39.0%,而H…H的作用力占比为25.9%,O…O的作用力占比为13.6%。 相似文献
10.
针对目标函数非光滑的稀疏约束优化问题,给出基本可行性和λ-平稳性两个必要最优性条件,利用所给出的必要最优性条件构造出稀疏次梯度投影算法.在理论上分析了算法的收敛性,证明了由该算法所产生序列的任意聚点都是λ-平稳点.最后,通过两个数值实例验证了算法的收敛性、有效性和优化能力. 相似文献