全文获取类型
收费全文 | 1426篇 |
免费 | 390篇 |
国内免费 | 163篇 |
专业分类
化学 | 327篇 |
晶体学 | 5篇 |
力学 | 1篇 |
综合类 | 4篇 |
数学 | 16篇 |
物理学 | 1182篇 |
无线电 | 444篇 |
出版年
2024年 | 7篇 |
2023年 | 24篇 |
2022年 | 23篇 |
2021年 | 40篇 |
2020年 | 54篇 |
2019年 | 52篇 |
2018年 | 45篇 |
2017年 | 61篇 |
2016年 | 58篇 |
2015年 | 70篇 |
2014年 | 76篇 |
2013年 | 98篇 |
2012年 | 93篇 |
2011年 | 114篇 |
2010年 | 97篇 |
2009年 | 75篇 |
2008年 | 114篇 |
2007年 | 114篇 |
2006年 | 89篇 |
2005年 | 59篇 |
2004年 | 61篇 |
2003年 | 77篇 |
2002年 | 60篇 |
2001年 | 76篇 |
2000年 | 71篇 |
1999年 | 54篇 |
1998年 | 29篇 |
1997年 | 31篇 |
1996年 | 38篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1979条查询结果,搜索用时 109 毫秒
201.
纳米混合分子聚集体材料中弗兰克尔激子迁移的相位弛豫 总被引:1,自引:0,他引:1
在有机染料PIC-1中引入其衍生物azaPIC-I形成能量势垒,改变在混合分子聚集体中PIC-I的J-聚集体的实体长度。用双调制外差检测的累积光子回波技术研究了相干弗兰克尔激子失相过程。观测到激子失相时间T2随azaPIC-1克分子数的增大从60ps变为224ps。 相似文献
202.
The general dynamical equations for perfect fluid filled spheres with an outward flux of photons are derived. The vital role
played by the energy density of the free gravitational field in accelerating photon production has been emphasized. It is
pointed out that even when the material energy density is finite, the energy density of the free gravitational field can take
infinitely large values resulting in vanishing surface area of the star. A generalized Schwarzschild interior solution with
conformally flat geometry but with photon emission has been obtained. It is pointed out that the interior conformal coordinate
system bears a strong resemblance to the exterior Krushkal coordinates. It is shown that for spherical star the invariant
velocity of the fluid particles, falling towards the centre, is proportional to its radius suggesting that the outer envelopes
collapse at a faster rate than the core part. It is shown that the interior radiating solution can be matched with generalized
Schwarzchild exterior solution. 相似文献
203.
首次合成了肽键桥连的四苯卟啉-蒽醌(TPP-AQ)化合物,以此作为研究光合成电子传递的模型化合物,用时间相关单光子荧光技术研究了该化合物在不同溶剂中分子内的电子转移。 相似文献
204.
光子计数技术及其在弱光计量中的应用 总被引:1,自引:0,他引:1
从光子计数原理出发,介绍光子计数系统的构成,分析光电倍增管的脉冲幅度分布,并叙述光子计数技术在弱光计量中的实际应用。 相似文献
205.
Wu Shi-fa 《Frontiers of Physics in China》2006,1(3):263-274
This review has introduced a new near-field optical microscope (NOM)—atomic force microscope combined with photon scanning
tunneling microscope (AF / PSTM). During scanning, AF/PSTM could get two optical images of refractive index image and transmissivity
image, and two AFM images of topography image and phase image. A reflected near-field optical microscope (AF/RSNOM) has also
been developed on AF/PSTM platform. The NOM has been reviewed in this paper and the comparison between AF/PSTM & RSNOM and
the commercial A-SNOM & RNOM has also been discussed. The functions of AF/PSTM & RSNOM are much better than A-SNOM & RNOM. 相似文献
206.
Martin Land 《Foundations of Physics》2003,33(8):1157-1175
In relativistic classical and quantum mechanics with Poincaré-invariant parameter, particle worldlines are traced out by the evolution of spacetime events. The formulation of a covariant canonical framework for the evolving events leads to a dynamical theory in which mass conservation is demoted from a priori constraint to the status of conserved Noether current for a certain class of interactions. In pre-Maxwell electrodynamics—the local gauge theory associated with this framework —events induce five local off-shell fields, which mediate interactions between instantaneous events, not between the worldlines which represent entire particle histories. The fifth field, required to compensate for dependence of gauge transformations on the evolution parameter, enables the exchange of mass between particles and fields. In the equilibrium limit, these pre-Maxwell fields are pushed onto the zero-mass shell, but during interactions there is no mechanism regulating the mass that photons may acquire, even when event trajectories evolve far into the spacelike region. This feature of the off-shell formalism requires the application of some ad hoc mechanism for controlling the photon mass in two opposite physical domains: the low energy motion of a charged event in classical Coulomb scattering, and the renormalization of off-shell quantum electrodynamics. In this paper, we discuss a nonlocal, higher derivative correction to the photon kinetic term, which provides regulation of the photon mass in a manner which preserves the gauge invariance and Poincaré covariance of the original theory. We demonstrate that the inclusion of this term is equivalent to an earlier solution to the classical Coulomb problem, and that the resulting quantum field theory is renormalized. 相似文献
207.
应用PCS和AFM研究单价阳离子和通道功能状态对兔骨骼肌ryanodine受体(钙释放通道)相互作用的影响 总被引:1,自引:0,他引:1
Ryanodine受体(RyR)是位于细胞内钙库膜上的一种钙释放通道。对骨骼肌和心肌的肌浆网的电镜研究表明RyR在膜上相互连接在一起,形成大片规则的二维晶格排列。近年来理论模型和试验证据表明,排列在一起的RyR在通道打开和关闭时存在协同效应,即具有“门控偶联”的调控机制。研究RyR之间相互作用的基本规律及其调控因素对于深入了解这种机制具有重要意义。在我们的工作中,主要采用两种互补的手段:光子相关光谱法(PCS)和原子力显微镜(AFM)来研究溶液中RyR的相互作用。初步的研究主要集中在细胞内两种主要的单价阳离子Na’和K’,以及RyR的功能状态对该通道相互作用的影响。 相似文献
208.
本文用噪音微扰场讨论了三光子吸收效应对光纤放大器的增益噪音和误码率的影响.由此得到三光子吸收效应能抑制该类噪音和减小误码率而有利于光孤子通信的结论. 相似文献
209.
理论分析了线偏振光波的偏振方向对GaAs半导体双光子吸收的影响,实现了GaAs半导体材料中不同偏振方向的双光子吸收限幅,提高了双光子吸收光限幅的性能。 相似文献
210.
Summary Based on a theoretical model worked out previously, an analysis is reported of triplet and double differential cross-section
of hydrogen atom ionization by electron impact in the presence of a single-mode, homogeneous, linearly polarized, off-resonance
laser field. In particular, calculations are carried out to investigatea) the dependence of the cross-sections on the field strength,b) the average number of exchanged photons,c) the limits of validity of a known sum rule. The reported results improve considerably the present knowledge of this kind
of elementary stimulated atomic process.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献