全文获取类型
收费全文 | 8422篇 |
免费 | 1739篇 |
国内免费 | 1044篇 |
专业分类
化学 | 6399篇 |
晶体学 | 94篇 |
力学 | 405篇 |
综合类 | 88篇 |
数学 | 845篇 |
物理学 | 3374篇 |
出版年
2024年 | 10篇 |
2023年 | 185篇 |
2022年 | 207篇 |
2021年 | 307篇 |
2020年 | 420篇 |
2019年 | 463篇 |
2018年 | 366篇 |
2017年 | 333篇 |
2016年 | 496篇 |
2015年 | 473篇 |
2014年 | 560篇 |
2013年 | 694篇 |
2012年 | 873篇 |
2011年 | 826篇 |
2010年 | 616篇 |
2009年 | 502篇 |
2008年 | 584篇 |
2007年 | 544篇 |
2006年 | 437篇 |
2005年 | 340篇 |
2004年 | 244篇 |
2003年 | 226篇 |
2002年 | 268篇 |
2001年 | 242篇 |
2000年 | 137篇 |
1999年 | 173篇 |
1998年 | 113篇 |
1997年 | 77篇 |
1996年 | 71篇 |
1995年 | 54篇 |
1994年 | 55篇 |
1993年 | 57篇 |
1992年 | 48篇 |
1991年 | 47篇 |
1990年 | 40篇 |
1989年 | 33篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1959年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
测定了亚单层InGaAs/GaAs量子点-量子阱异质结构在5K下的时间分辨光致发光谱.亚单层量 子点的辐射寿命在500 ps 至 800 ps之间,随量子点尺寸的增大而增大,与量子点中激子的 较小的横向限制能以及激子从小量子点向大量子点的隧穿转移有关.光致发光上升时间强烈 依赖于激发强度密度.在弱激发强度密度下,上升时间为 35 ps,纵光学声子发射为主要的 载流子俘获机理.在强激发强度密度下,上升时间随激发强度密度的增加而减小,俄歇过程 为主要的载流子俘获机理.该结果对理解亚单层量子点器件的工作特性非常有用.
关键词:
亚单层
量子点-量子阱
时间分辨光致发光谱 相似文献
992.
993.
Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence φo. From the plot of the accumulated laser fluence Nφth(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation. 相似文献
994.
Dongfang Jia Bin Tan Zhaoying Wang Chunfeng Ge Tianxin Yang Wenjun Ni Shichen Li 《中国光学快报(英文版)》2006,4(6)
By using the amplified 10-GHz, 5.5-ps sech2 pulses with high quality and chirp-free from regeneratively mode-locked fiber laser (RMLFL) as the soliton source, 2-5 order optical soliton phenomena are observed successfully in a 4.28-km dispersion flattened fiber. The experimental results agree well with the theoretical calculation. 相似文献
995.
R. Jiang M. B. Hu B. Jia R. L. Wang Q. S. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):267-273
This paper studies a new model, which considers the effects of
drivers reaction delay in the Nagel-Schreckenberg model. We studied
the traffic flow properties in the new model under both periodic and
open boundary conditions. The fundamental diagram, spatio-temporal
patterns, density-density correlation functions, relaxation time,
and distance headway distribution are investigated. Several
interesting results are reported, for example, (i) the jam becomes
less condensed when the delay effect is considered; (ii) the
distance headway of the new model exhibits a multi-peak distribution
when randomization p is small; (iii) for large p, the
distribution of distance headway follows a power law in the new
model; (iv) under open boundary conditions, the existence of a
stationary jam near the left boundary will lower the flow rate. 相似文献
996.
X. G. Li Z. Y. Gao B. Jia R. Jiang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(3):385-391
Segregation effects commonly exist in granular mixtures
with difference in size, shape or density. In mixed traffic flow,
slow vehicle and fast vehicle, as two types of particles, have
different desired speed. We investigate the segregation along the
road in mixed traffic flow by using a symmetric two-lane cellular
automata model. A parameter D, which quantifies the degree of
segregation, is defined. We study the density dependency of the
parameter at different randomization probability. Simulation results
show that segregation is more obviously in free flow region. We
argue that the overtaking maneuvers have similar effect as
percolation in granular flow. 相似文献
997.
998.
Huang Xiao-Qin Wang Mian-Sen Jia Jun-Guo 《Journal of Applied Mathematics and Computing》2007,24(1-2):377-385
In this paper, by the equations of Mao [9] and Peng [5], we use the martingale method to establish the comparison theorems of backward stochastic differential equations (BSDEs). We generalize the results of Cao-Yan [1]. 相似文献
999.
A novel route for preparing PbWO4–TiO2 nanofilms on a glass substrate is firstly proposed. The collodion is used as a dispersant and film-forming agent. The nanofilms are characterized through SEM, XRD, TG/DTA, PL and IR, respectively. The results of XRD indicate PbWO4 particles with tetragonal scheelite structure and TiO2 particles with Anatase phase, and SEM shows they are well dispersed in the substrate. Compared with nanoparticles, when TiO2 nanoparticles are added in 5% ratio, the PL intensities at 395 nm of PbWO4 nanofilms are enhanced obviously. IR spectrum reveals a large absorption band between 750 and 870 cm−1, which is the W–O stretching vibration in WO4 tetrahedron. 相似文献
1000.