全文获取类型
收费全文 | 43517篇 |
免费 | 5728篇 |
国内免费 | 7364篇 |
专业分类
化学 | 30220篇 |
晶体学 | 3092篇 |
力学 | 991篇 |
综合类 | 162篇 |
数学 | 252篇 |
物理学 | 12443篇 |
无线电 | 9449篇 |
出版年
2024年 | 92篇 |
2023年 | 297篇 |
2022年 | 719篇 |
2021年 | 856篇 |
2020年 | 1112篇 |
2019年 | 1089篇 |
2018年 | 1099篇 |
2017年 | 1469篇 |
2016年 | 1831篇 |
2015年 | 1615篇 |
2014年 | 2146篇 |
2013年 | 3846篇 |
2012年 | 2620篇 |
2011年 | 2719篇 |
2010年 | 2414篇 |
2009年 | 2674篇 |
2008年 | 2870篇 |
2007年 | 3087篇 |
2006年 | 3115篇 |
2005年 | 2812篇 |
2004年 | 2712篇 |
2003年 | 2130篇 |
2002年 | 1814篇 |
2001年 | 1402篇 |
2000年 | 1398篇 |
1999年 | 1248篇 |
1998年 | 1090篇 |
1997年 | 999篇 |
1996年 | 1042篇 |
1995年 | 914篇 |
1994年 | 838篇 |
1993年 | 674篇 |
1992年 | 607篇 |
1991年 | 372篇 |
1990年 | 232篇 |
1989年 | 151篇 |
1988年 | 128篇 |
1987年 | 77篇 |
1986年 | 41篇 |
1985年 | 58篇 |
1984年 | 45篇 |
1983年 | 21篇 |
1982年 | 26篇 |
1981年 | 24篇 |
1980年 | 9篇 |
1979年 | 18篇 |
1976年 | 12篇 |
1975年 | 12篇 |
1974年 | 8篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
采用顶部籽晶提拉法(TSSG)生长出Yb:KY(WO4)2(Yb:KYW)激光晶体.对预烧后的原料及晶体进行了XRD分析,结果表明,分别在920℃和600℃预烧8h后的熔质和助熔剂基本上形成一相,抑止了实验中的挥发问题;所生长的晶体为β-Yb:KYW,计算其晶格常数为a=1.063nm,b=1.034nm,c=0.755nm,β=130.75°.测得不同厚度样品的吸收光谱,结果表明样品在933nm和981nm有较强的吸收峰,计算出主峰981nm的吸收截面σ关键词:
Yb:KYW
TSSG法
晶体结构
光谱参数 相似文献
52.
53.
High index of refraction via quantum interference in a three-level system of Er^3+-doped yttrium aluminium garnet crystal
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A simple three-level system is proposed to produce high index of refraction with zero absorption in an Er^3+-doped yttrium aluminium garnet (YAG) crystal, which is achieved for a probe field between the excited state 4I13/2 and ground state 4I15/2 by adjusting a strong coherent driving field between the upper excited state 4I11/2 and 4I15/2. It is found that the changes of the frequency of the coherent driving field and the concentration of Er^3+ ions in the YAG crystal can maximize the index of refraction accompanied by vanishing absorption. This result could be useful for the dispersion compensation in fibre communication, laser particle acceleration, high precision magnetometry and so on. 相似文献
54.
55.
The consequences of Ge deposition on Br-terminated Si(1 0 0) were studied with scanning tunneling microscopy at ambient temperature after annealing at 650 K. One monolayer of Br was sufficient to prevent the formation of Ge huts beyond the critical thickness of 3 ML. This is possible because Br acts as a surfactant whose presence lowered the diffusivity of Ge adatoms. Hindered mobility was manifest at low coverage through the formation of short Ge chains. Further deposition resulted in the extension and connection of the Ge chains and gave rise to the buildup of incomplete layers. The deposition of 7 ML of Ge resulted in a rough surface characterized by irregularly shaped clusters. A short 800 K anneal desorbed the Br and allowed Ge atoms to reorganize into the more energetically favorable “hut” structures produced by conventional Ge overlayer growth on Si(1 0 0). 相似文献
56.
Cheul-Ro Lee 《Journal of Electronic Materials》2002,31(4):327-331
We have investigated the growth characteristics of n-Al0.15Ga0.85N:Si/GaN and the electronic properties of Au/n-Al0.15Ga0.85N:Si diode structures grown by metal-organic chemical vapor deposition (MOCVD) with various Si incorporations. The Al0.15Ga0.85N:Si layers were grown on undoped GaN/sapphire (0001) epitaxial layers in a horizontal MOCVD reactor at the reduced pressure
of 300 torr. The mirrorlike surface, free of defects, such as cracks or hillocks, can be seen in the undoped Al0.15Ga0.85N epilayer, which was grown without any intentional flow of SiH4. However, many cracks are observed in the n-Al0.15Ga0.85N:Si, which was grown with Si incorporation above 1.0 nmol/min. While Au/n-Al0.15Ga0.85N:Si diodes having low incorporation of Si showed retively good rectifying behavior, the samples having high Si incorporation
exhibited leaky current-voltage (I-V) behavior. Particularly, the Au/n-Al0.15Ga0.85N:Si structure grown with Si incorporation above 1.0 nmol/min cannot be used for electrical rectification. Both added tunneling
components and thermionic emission influence the current transport at the Au/n-Al0.15Ga0.85N:Si barrier when Si incorporation becomes higher. 相似文献
57.
58.
59.
许多实验对用CsI(Tl)闪烁晶体作为探测器来寻找和探测暗物质的可行性进行了研究.本工作利用8MeV单能中子轰击CsI(Tl)晶体探测器来研究Cs核和I核的QuenchingFactor.在数据处理中,运用脉冲形状甄别(PSD)方法来分辨反冲核信号和本底信号.实验结果表明,在7keV到132keV的能区中,Quench ingFactor随着反冲核能量的减少而增加.在探测暗物质的实验中,这一性质对于CsI(Tl)晶体探测器获得较低的能量阈值是很有利的. 相似文献
60.
A simple simulation scheme that simultaneously describes the growth kinetics of SiO2 films at the nanometer scale and the SiOx/Si interface dynamics (its extent, and spatial/temporal evolution) is presented. The simulation successfully applies to experimental data in the region above and below 10 nm, reproduces the Deal and Grove linear-parabolic law and the oxide growth rate enhancement in the very thin film regime (the so-called anomalous region). According to the simulation, the oxidation is governed mainly by two processes: (a) the formation of a transition suboxide layer and (b) its subsequent drift towards the silicon bulk. We found that it is the superposition of these two processes that produces the crossover from the anomalous oxidation region behavior to the linear-parabolic law. 相似文献