全文获取类型
收费全文 | 4760篇 |
免费 | 1258篇 |
国内免费 | 444篇 |
专业分类
化学 | 1277篇 |
晶体学 | 44篇 |
力学 | 54篇 |
综合类 | 29篇 |
数学 | 75篇 |
物理学 | 2663篇 |
无线电 | 2320篇 |
出版年
2024年 | 34篇 |
2023年 | 101篇 |
2022年 | 160篇 |
2021年 | 160篇 |
2020年 | 159篇 |
2019年 | 143篇 |
2018年 | 142篇 |
2017年 | 174篇 |
2016年 | 209篇 |
2015年 | 252篇 |
2014年 | 360篇 |
2013年 | 349篇 |
2012年 | 388篇 |
2011年 | 350篇 |
2010年 | 283篇 |
2009年 | 301篇 |
2008年 | 372篇 |
2007年 | 344篇 |
2006年 | 342篇 |
2005年 | 269篇 |
2004年 | 245篇 |
2003年 | 221篇 |
2002年 | 181篇 |
2001年 | 147篇 |
2000年 | 140篇 |
1999年 | 97篇 |
1998年 | 102篇 |
1997年 | 79篇 |
1996年 | 67篇 |
1995年 | 48篇 |
1994年 | 37篇 |
1993年 | 37篇 |
1992年 | 39篇 |
1991年 | 24篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有6462条查询结果,搜索用时 15 毫秒
981.
采用第一性原理的含时密度泛函理论,系统地研究了少周期高强度飞秒脉冲驱动氩晶体固体产生孤立阿秒脉冲的脉宽、强度随驱动脉冲波形、偏振方向的变化规律.结果发现:1)固体产生的孤立阿秒脉冲对驱动脉冲波形和偏振十分敏感;2)在最优的驱动脉冲波形和偏振情况下,固体产生的孤立阿秒脉冲的宽度与原子气相比没有明显增大的同时,其强度比原子气产生的强度大了接近4倍.结果对固体孤立阿秒脉冲产生及其调控的探索是有帮助的. 相似文献
982.
Xiao-Fang Ouyang 《中国物理 B》2022,31(7):77304-077304
Exploring the half-metallic nanostructures with large band gap and high carrier mobility is a crucial solution for developing high-performance spintronic devices. The electric and magnetic properties of monolayer zigzag black-phosphorene nanoribbons (ZBPNRs) with various widths are analyzed by means of the first-principles calculations. Our results show that the magnetic ground state is dependent on the width of the nanoribbons. The ground state of narrow nanoribbons smaller than 8ZBPNRs prefers ferromagnetic order in the same edge but antiferromagnetic order between two opposite edges. In addition, we also calculate the electronic band dispersion, density of states and charge density difference of 8ZBPNRs under the action of out-of-plane electric field. More interesting, the addition of out-of-plane field can modulate antiferromagnetic semiconductor to the half metal by splitting the antiferromagnetic degeneracy. Our results propose a new approach to realize half-metal in phosphorene, which overcomes the drawbacks of graphene/silicene with negligible band gap as well as the transitional metal sulfide (TMS) with low carrier mobility. 相似文献
983.
Hai-Long Liu 《中国物理 B》2022,31(11):110306-110306
A single-photon interferometer is a fundamental element in quantum information science. In most previously reported works, single-photon interferometers use an active feedback locking system to stabilize the relative phase between two arms of the interferometer. Here, we use a pair of beam displacers to construct a passively stable single-photon interferometer. The relative phase stabilization between the two arms is achieved by stabilizing the temperature of the beam displacers. A purely polarized single-photon-level pulse is directed into the interferometer input port. By analyzing and measuring the polarization states of the single-photon pulse at the output port, the achieved polarization fidelity of the interferometer is about 99.1 ±0.1%. Our passively stabilized single-photon interferometer provides a key element for generating high-fidelity entanglement between a photon and atomic memory. 相似文献
984.
Impact of AlxGa1-xN barrier thickness and Al composition on electrical properties of ferroelectric HfZrO/Al2O3/AlGaN/GaN MFSHEMTs 下载免费PDF全文
Ferroelectric (FE) HfZrO/Al$_{2}$O$_{3}$ gate stack AlGaN/GaN metal-FE-semiconductor heterostructure high-electron mobility transistors (MFSHEMTs) with varying Al$_{x}$Ga$_{1-x}$N barrier thickness and Al composition are investigated and compared by TCAD simulation with non-FE HfO$_{2}$/Al$_{2}$O$_{3}$ gate stack metal-insulator-semiconductor heterostructure high-electron mobility transistors (MISHEMTs). Results show that the decrease of the two-dimensional electron gas (2DEG) density with decreasing AlGaN barrier thickness is more effectively suppressed in MFSHEMTs than that in MISHEMTs due to the enhanced FE polarization switching efficiency. The electrical characteristics of MFSHEMTs, including transconductance, subthreshold swing, and on-state current, effectively improve with decreasing AlGaN thickness in MFSHEMTs. High Al composition in AlGaN barrier layers that are under 3-nm thickness plays a great role in enhancing the 2DEG density and FE polarization in MFSHEMTs, improving the transconductance and the on-state current. The subthreshold swing and threshold voltage can be reduced by decreasing the AlGaN thickness and Al composition in MFSHEMTs, affording favorable conditions for further enhancing the device. 相似文献
985.
实现自由调控电磁波不仅具有重要的科学研究意义,而且是通讯、能源、国防等领域的迫切需求。为了解决自然材料调控电磁波能力受限的问题,人们提出了人工超构材料这一新概念,实现了负折射、光学隐身等奇异的电磁效应。然而,经过多年的发展,超构材料仍存在结构复杂、损耗偏高、难以集成调谐等挑战。最近,本团队与国际同行一起提出了超构表面的新概念。超构表面基于电磁波在平面微结构上散射时获得的界面相位突变,充分利用人工微结构的"排列序构"这一自由度,实现了对电磁波振幅、相位、偏振及波前分布的有效调控,克服了超构材料遇到的瓶颈问题。本文主要回顾了本团队在偏振调控、波前调控及动态调控等方面开展的创新性研究。 相似文献
986.
The effect of plasma polarization around a negatively charged dust particle is investigated with the help of Monte Carlo simulation of ion trajectories in the electric field of the dust particle and an external electric field. The induced dipole moment of such a system was estimated in a wide range of dust particle and plasma parameters. It is shown that the dipole moment is very large, and has a non‐monotonous dependence on the external electric field. For a small external electric field, it weakly depends on the charge of the dust particle. The dipole moment reduces with the decrease of ion mean free path (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
987.
988.
989.
State of polarization (SOP) and polarization mode dispersion (PMD) are stochastic in nature due to changes in the properties of the optical fibres and its positions because of both intrinsic and extrinsic perturbations. With 184 PMD values obtained by use of the FTB-5700 single-ended dispersion analyzer, the predicted theoretical Gaussian fit was obtained with a mean of 0.47 ps and standard deviation of 0.08 ps. This small standard deviation was justification for its accuracy in measuring PMD of aerial optical fibres. A comparison is also made on the accuracy of the GINTY and the FTB-5700 on measurement of PMD of aerial optical fibres with results showing that the latter is more accurate compared to the former. The time scale over which to compensate PMD in aerial optical fibres was determined and it is slightly higher than 400 s; the decorrelation time obtained for SOPs on a particular windy and hot day. This is because the changes of the PMD vector are known to be slower than SOP changes. 相似文献
990.
《Physics and Chemistry of Liquids》2012,50(6):753-762
Abstract A new expression for the excess molar polarization in binary mixture of polar and nonpolar liquids has been proposed. An experimental assessment of the proposed equation has been made by comparison with an earlier equation in the binary mixtures of amines in nonpolar liquids. The proposed equation for excess molar polarization is found to be more appropriate for detailed study of molecular association in the liquid mixtures. 相似文献