全文获取类型
收费全文 | 9293篇 |
免费 | 1859篇 |
国内免费 | 987篇 |
专业分类
化学 | 7092篇 |
晶体学 | 36篇 |
力学 | 882篇 |
综合类 | 49篇 |
数学 | 372篇 |
物理学 | 3708篇 |
出版年
2024年 | 18篇 |
2023年 | 109篇 |
2022年 | 212篇 |
2021年 | 235篇 |
2020年 | 333篇 |
2019年 | 357篇 |
2018年 | 394篇 |
2017年 | 356篇 |
2016年 | 404篇 |
2015年 | 509篇 |
2014年 | 700篇 |
2013年 | 862篇 |
2012年 | 667篇 |
2011年 | 735篇 |
2010年 | 584篇 |
2009年 | 663篇 |
2008年 | 625篇 |
2007年 | 561篇 |
2006年 | 563篇 |
2005年 | 508篇 |
2004年 | 464篇 |
2003年 | 433篇 |
2002年 | 281篇 |
2001年 | 200篇 |
2000年 | 201篇 |
1999年 | 157篇 |
1998年 | 147篇 |
1997年 | 137篇 |
1996年 | 108篇 |
1995年 | 124篇 |
1994年 | 87篇 |
1993年 | 71篇 |
1992年 | 56篇 |
1991年 | 19篇 |
1990年 | 43篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 27篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 22篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1971年 | 4篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
4fN-15d energy levels of lanthanides: aquasi-angular-momentum approach and its application to Cs2NaYF6:Er3+ 下载免费PDF全文
<正>The spin-orbit interaction of the 5d electron needs to be taken into account to give the proper energy structure for the 4fN-15d configuration of heavy lanthanide ions occupying a site with ligands forming an octahedron.This paper derives theoretical results for the energy structure by treating the t2 orbitals as quasi p orbitals and then using angular-momentum coupling techniques.An analytic expression for the electric dipole absorption line strengths between 4fN multiplets and 4fN-15d states is given in terms of various angular-momentum quantum numbers and re-coupling coefficients.The result is then applied to interpret the excitation spectrum of Cs2NaYF6:Er3+.The high-spin and low-spin states of Cs2NaYF6:Er3+ are discussed in terms of the wavefunctions obtained by using the developed theoretical model. 相似文献
92.
Path coupling is a useful technique for simplifying the analysis of a coupling of a Markov chain. Rather than defining and analysing the coupling on every pair in Ω×Ω, where Ω is the state space of the Markov chain, analysis is done on a smaller set SΩ×Ω. If the coefficient of contraction β is strictly less than one, no further analysis is needed in order to show rapid mixing. However, if β=1 then analysis (of the variance) is still required for all pairs in Ω×Ω. In this paper we present a new approach which shows rapid mixing in the case β=1 with a further condition which only needs to be checked for pairs in S, greatly simplifying the work involved. We also present a technique applicable when β=1 and our condition is not met. 相似文献
93.
Patrik Andersson Arto Annila Gottfried Otting 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,133(2):364-367
A generalized version of the TROSY experiment allows the spin-state selective editing of the four multiplet components of15N–1H cross peaks of amide groups in proteins into four different subspectra, with no penalty in sensitivity. An improvement by
in sensitivity results, if only two of the four multiplet components are selected. Use of the experiment for the measurement of1JHNcoupling constants is discussed. A water flip-back version of the experiment is demonstrated with a 45 kDa fragment of15N/2H labeledStaphylococcus aureusgyrase B. 相似文献
94.
《Physics letters. A》2020,384(20):126512
Recent simulation results imply the lowering of the ground-state correlation energy per counterion at a charged planar wall, compared with that of the 2D and 3D one-component plasma systems. Our aim is to correctly evaluate the ground-state energy of strongly-coupled counterion systems by considering a quasi-2D bound state where bound counterions are confined to a layer of molecular thickness. We use a variational approach based on the Gibbs-Bogoliubov inequality for the lower-bound free energy so that the liquid-state theory can be incorporated into the formulations. The soft mean spherical approximation demonstrates that the lowered ground-state energy can be reproduced by the obtained analytical form of a quasi-2D bound state. 相似文献
95.
We first study the basic coupling and obtain an equation between total variation norm and the basic coupling. Then by use this equation we investigate the ergodicity property of continuous time Markov processes in general state space. For an ergodic continuous-time Markov processes, adding condition π(f) < ∞, by using the coupling method, there exists the full absorption set, such that the continuous time Markov processes are f-ergodic on it. © 2022 Chinese Academy of Sciences. All rights reserved. 相似文献
96.
We investigate the coherent control of spin tunneling for a spin–orbit (SO) coupled boson trapped in a driven triple well. In the high-frequency limit, the quasienergies of the system are obtained analytically and the fine energy band structures are shown. By regulating the driving parameters, we reveal that the directed spin-flipping or spin-conserving tunneling of an SO-coupled boson occurs along different pathways and in different directions. The analytical results are demonstrated by numerical simulations and good agreements are found. Further, an interesting scheme of quantum spin tunneling switch with or without spin-flipping is presented. The results may have potential applications in the design of spintronic devices. 相似文献
97.
Mirosław Gałązka 《Phase Transitions》2013,86(11-12):1125-1132
An equation of state accounting for coupling of the primary order parameter (here the polarization) with a secondary order parameter (here a strain ?) is used to describe the temperature dependences of the spontaneous polarization and of the electric susceptibility on external biasing field. A new scaling invariant and its explicit expression are given. The theory is exemplified by the effective critical behavior of the molecular ferroelectric crystals (CH3NH3)5Bi2Cl11 (MAPCB) and (CH3NH3)5Bi2Br11 (MAPBB). 相似文献
98.
根据微波网络理论,将单耦合口输出回路的冷测模拟物理模型进行扩展,使其适用于双耦合口回路。并在此模型的基础上提出了计算双间隙双耦合口输出回路间隙阻抗频率特性的冷测模拟方法。运用该方法,结合软件仿真,计算分析了某S波段双间隙双耦合口输出腔,分别得到该回路工作在2模式下的阻抗实部与虚部的频率特性,并对计算结果的合理性作了论证。最后通过将计算结果与采用场分析法及散射参数方法得到的结果进行比较和分析,进一步验证该冷测模拟方法的可靠性。 相似文献
99.
100.
Lingyan Shen 《Phase Transitions》2013,86(8):755-771
In this paper, temperature evolution in shape-memory TiNi alloys was in situ measured in the process of phase transition under shock loading tests. It was shown that the temperature increased during loading, while unloading, it would keep the maximum value constant or decreased, depending on the strain rate. The corresponding dynamic response indicated that the hardening property is related to phase transition strain and the transformation path has remarkable strain-rate effect. The reason for this phenomenon is essentially due to the temperature dependence of the phase transformation stress. Moreover, the evolution of temperature was consistent with the change of stress, suggesting that this dynamic phase transition deformation is uniform. The theoretical calculation shows that the mechanism of temperature evolution results from the release of latent heat and the hysteresis dissipated energy. The results of this investigation provide insight into intriguing strain-rate-dependent phenomena intrinsic of TiNi alloys. 相似文献