全文获取类型
收费全文 | 9957篇 |
免费 | 2103篇 |
国内免费 | 1732篇 |
专业分类
化学 | 5057篇 |
晶体学 | 99篇 |
力学 | 603篇 |
综合类 | 117篇 |
数学 | 1176篇 |
物理学 | 6740篇 |
出版年
2024年 | 20篇 |
2023年 | 100篇 |
2022年 | 214篇 |
2021年 | 240篇 |
2020年 | 307篇 |
2019年 | 220篇 |
2018年 | 218篇 |
2017年 | 267篇 |
2016年 | 327篇 |
2015年 | 397篇 |
2014年 | 534篇 |
2013年 | 787篇 |
2012年 | 589篇 |
2011年 | 733篇 |
2010年 | 659篇 |
2009年 | 738篇 |
2008年 | 799篇 |
2007年 | 820篇 |
2006年 | 719篇 |
2005年 | 663篇 |
2004年 | 492篇 |
2003年 | 544篇 |
2002年 | 481篇 |
2001年 | 398篇 |
2000年 | 379篇 |
1999年 | 359篇 |
1998年 | 279篇 |
1997年 | 235篇 |
1996年 | 207篇 |
1995年 | 153篇 |
1994年 | 155篇 |
1993年 | 111篇 |
1992年 | 112篇 |
1991年 | 94篇 |
1990年 | 49篇 |
1989年 | 73篇 |
1988年 | 43篇 |
1987年 | 43篇 |
1986年 | 21篇 |
1985年 | 48篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 34篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 14篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1974年 | 4篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Bound states of the Klein-Gordon and Dirac equations for scalar and vector harmonic oscillator potentials 下载免费PDF全文
We give the exact bound states of the Klein-Gordon and Dirac equations with equal scalar and vector harmonic oscillator potentials. 相似文献
132.
LI HongJian FU ShaoLi XIE SuXia XU HaiQing ZHOU Xin & WU JinJun College of Physics Science Technology Central South University Changsha China College of Materials Science Engineering 《中国科学:物理学 力学 天文学(英文版)》2010,(1)
We have numerically simulated the induced electric fields and the plasmonic interactions of a metallic nanotube near a thin metallic film. Our study shows that the energies and intensities of the plasmon resonances depend strongly on the aspect ratio (the ratio of the inner to outer radius) of the nanotube as well as the separation between the center of the nanotube and the upper surface of the metallic film and the thickness of the film. The enhancement of the induced electric field of this system reaches ... 相似文献
133.
普洱茶及其原料多糖分子组成及光谱学特性研究 总被引:4,自引:0,他引:4
研究了普洱茶发酵过程中多糖分子组成及光谱学特性的变化规律。结果显示,普洱茶及其原料多糖主要组分TPS1和TPS2的分子组成及光谱学特性差异显著。TPS2含有较高糖醛酸,而TPS1含有较高的中性糖和蛋白质。TPS1和TPS2均由半乳糖(Gal)、阿拉伯糖(Arb)、甘露糖(Man)、葡萄糖(Glu)、木糖(Xyl)、鼠李糖(Rha)六种单糖组成,其分子摩尔比分别为23.6∶5.9∶24.2∶1.1∶1.8∶3.2和26.9∶3.2∶19.3∶5.5∶1.3∶2.7。TPS2和TPS1的重均分子量分别为1.68×104和1.21×104道尔顿。TPS1和TPS2水溶液在200~400 nm之间无特征吸收峰。红外光谱图显示,TPS1和TPS2的信息基本相同,都是含有吡喃环的多糖。在三维AFM图中,TPS1形成的聚集体高度约为4 nm, 长宽约为0.2~0.4 μm,TPS2形成的聚集体高度约为40 nm,长宽约为0.5~0.8 μm。SEM图片显示,TPS1呈表面光滑的鳞片状聚集体,TPS2呈表面粗糙的片状聚集体。引起普洱茶及其原料多糖分子组成及光谱学性质发生变化的动力主要为微生物作用和湿热作用。 相似文献
134.
降压型、升压型和升压-降压型DC-DC变换器是应用广泛的基本开关DC-DC变换器.电流模式控制开关DC-DC变换器在较宽的电路参数范围内具有两个边界,基于开关切换前后电感电流的上升和下降斜率,建立了斜坡补偿电流模式控制开关DC-DC变换器的统一模型.该模型进行无量纲归一化处理后只有三个参数,可有效展示开关DC-DC变换器在电感电流连续传导模式(CCM)和电感电流不连续传导模式(DCM)时的动力学特性.利用此模型,导出了轨道状态发生转移时的两个分界线方程,由此确定了开关DC-DC变换器的稳定周期1域、CCM鲁棒混沌域和DCM弱混沌强阵发域三个工作状态区域.开关DC-DC变换器二维参数映射图和电流模式控制降压型DC-DC变换器的电路实验观察验证了由两条分界线划分工作状态域的正确性. 相似文献
135.
This paper utilizes the brightness-voltage waveform curve
to investigate the primary electron in solid state
cathodoluminescence. The results indicate that the primary electron
is from the interface state of SiO2/MEH-PPV
(Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) under
the lower electric field which contributes to the 580-nm emission.
With increasing the electric field, the 405-nm emission is obtained,
and under this condition, the origin of the primary electron is mainly
from tunneling. 相似文献
136.
Temporal electronic structure of non-resonant Raman excited virtual state of P-nitroaniline by 514 nm excitation via bond polarisabilities 下载免费PDF全文
We have studied the temporal bond polarisabilities of para-nitroaniline from the Raman intensities by the algorithm proposed by Wu et al.in 1987 (Tian B,Wu G,Liu G 1987 J.Chem.Phys.87 7300).The bond polarisabilities provide much information concerning the electronic structure of the non-resonant Raman excited virtual state.At the initial moment by the 514.5 nm excitation,the tendency of the excited electrons (mapped out by the bond polarisabilities) is to spread to the molecular periphery,and the electronic structure of the Raman virtual state is close to the pseudo-quinonoidic state.When the final stage of relaxation is approached,the bond polarisabilities of those peripheral bonds relax faster than those closer to the molecular core,the phenyl ring.The molecule is in the benzenoidic form as demonstrated by the bond polarisabilities after relaxation. 相似文献
137.
The coherent-intermediate-entangled state |α, x)λ,v is proposed in the two-mode Fock Space, which exhibits both the properties of the coherent and entangled states. The |α, x)λ,v makes up a new quantum mechanical representation, and the completeness relation of |α, x)λ,v is proved by virtue of the technique of integral within an ordered product of operators. The corresponding squeezing operators are derived. Furthermore, Generalized P-representation is constructed in the coherent-intermediate-entangled state |α, x)λ,v and the Schmidt decomposition of |α, x)λ,v is investigated. 相似文献
138.
We present a new quantum protocol for solving detectable Byzantine agreement problem between three parties by employing one quantum key distribution protocol. The protocol is suggested by a special four-qubit entangled state instead of singlet states, which shows that singlet states are not necessary to achieve detectable Byzantine agreement. 相似文献
139.
A tripartite single-photon state shared through noisy quantum channels is considered for three different system configurations. The quantum teleportation of a single-photon state between two parties is investigated in cases with and without the assistance of a third party. The condition that the quantum teleportation is superior to the classical one is provided in terms of the damping rate and detector efficiency. 相似文献
140.
Aalok 《International Journal of Theoretical Physics》2009,48(2):522-534
The geometry of the symplectic structures and Fubini-Study metric is discussed. Discussion in the paper addresses geometry
of Quantum Mechanics in the classical phase space. Also, geometry of Quantum Mechanics in the projective Hilbert space has
been discussed for the chosen Quantum states. Since the theory of classical gravity is basically geometric in nature and Quantum
Mechanics is in no way devoid of geometry, the explorations pertaining to more and more geometry in Quantum Mechanics could
prove to be valuable for larger objectives such as understanding of gravity. 相似文献