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171.
D. Gao A. K. Ray 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):497-503
The electronic and geometrical properties of bulk americium and square and
hexagonal americium monolayers have been studied with the full-potential
linearized augmented plane wave (FP-LAPW) method. The effects of several
common approximations are examined: (1) non-spin polarization (NSP) vs. spin
polarization (SP); (2) scalar-relativity (no spin-orbit coupling (NSO)) vs.
full-relativity (i.e., with spin-orbit (SO) coupling included); (3)
local-density approximation (LDA) vs. generalized-gradient approximation
(GGA). Our results indicate that both spin polarization and spin orbit
coupling play important roles in determining the geometrical and electronic
properties of americium bulk and monolayers. A compression of both americium
square and hexagonal monolayers compared to the americium bulk is also
observed. In general, the LDA is found to underestimate the equilibrium
lattice constant and give a larger total energy compared to the GGA
calculations. While spin orbit coupling shows a similar effect on both
square and hexagonal monolayer calculations regardless of the model, GGA
versus LDA, an unusual spin polarization effect on both square and hexagonal
monolayers is found in the LDA results as compared with the GGA results. The
5f delocalization transition of americium is employed to explain our observed
unusual spin polarization effect. In addition, our results at the LDA level
of theory indicate a possible 5f delocalization could happen in the americium
surface within the same Am II (fcc crystal structure) phase, unlike the
usually reported americium 5f delocalization which is associated with crystal
structure change. The similarities and dissimilarities between the
properties of an Am monolayer and a Pu monolayer are discussed in detail. 相似文献
172.
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174.
在由S和D核子关联对构成的原子核集体运动态中,存在由辛弱数混合造成的伪态成份. 给出了计算这种伪态成份的公式,并进行计算和讨论. 相似文献
175.
密度矩阵重正化群方法(DMRG)在求解一维强关联格点模型的基态时可以获得较高的精度,在应用于二维或准二维问题时,要达到类似的精度通常需要较大的计算量与存储空间.本文提出一种新的DMRG异构并行策略,可以同时发挥计算机中央处理器(CPU)和图形处理器(GPU)的计算性能.针对最耗时的哈密顿量对角化部分,实现了数据的分布式存储,并且给出了CPU和GPU之间的负载平衡策略.以费米Hubbard模型为例,测试了异构并行程序在不同DMRG保留状态数下的运行表现,并给出了相应的性能基准.应用于4腿梯子时,观测到了高温超导中常见的电荷密度条纹,此时保留状态数达到104,使用的GPU显存小于12 GB. 相似文献
176.
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179.
Summary Statistical topography involves the study of the geometrical properties of the iso-sets (contour lines or surfaces) of a random potential (r). Previous work [1,2] has addressed coastlines on a random relief (x, y) that possess a single characteristic spatial scale with topography belonging to the universality class of the random percolation problem. In the present paper this previous analytical approach is extended to the case of a multiscale random function with a power spectrum of scales,
H
, in a wide range of wavelengths, 0 < <
m
. It is found that the pattern of the coastline differs significantly from that of a monoscale landscape provided that –3/4 <H < 1, with the case –3/4 <H < 0 corresponding to the long-range correlated percolation and 0 <H < 1 to the fractional Brownian relief. The expression for the fractal dimension of an individual coastline is derived,D
h
= (10 – 3H)/7, the maximum value of whichD
h = 7/4, corresponds to the monoscale relief. The distribution functionF(a) of level lines over their sizea is calculated:F(a) a
–4(1-H)/7, for 0 a
m
. A comparison of the theoretical results with geographical data is presented. 相似文献
180.
Fluorescence Blinking Beyond Nanoconfinement: Spatially Synchronous Intermittency of Entire Perovskite Microcrystals 下载免费PDF全文
Nithin Pathoor Ansuman Halder Amitrajit Mukherjee Jaladhar Mahato Dr. Shaibal K. Sarkar Dr. Arindam Chowdhury 《Angewandte Chemie (International ed. in English)》2018,57(36):11603-11607
Abrupt fluorescence intermittency or blinking is long recognized to be characteristic of single nano‐emitters. Extended quantum‐confined nanostructures also undergo spatially heterogeneous blinking; however, there is no such precedent in dimensionally unconfined (bulk) materials. Herein, we report multi‐level blinking of entire individual organo–lead bromide perovskite microcrystals (volume=0.1–3 μm3) under ambient conditions. Extremely high spatiotemporal correlation (>0.9) in intracrystal emission intensity fluctuations signifies effective communication amongst photogenerated carriers at distal locations (up to ca. 4 μm) within each crystal. Fused polycrystalline grains also exhibit this intriguing phenomenon, which is rationalized by correlated and efficient migration of carriers to a few transient nonradiative traps, the nature and population of which determine blinking propensity. Observation of spatiotemporally correlated emission intermittency in bulk semiconductor crystals opens the possibility of designing novel devices involving long‐range (mesoscopic) electronic communication. 相似文献