全文获取类型
收费全文 | 783篇 |
免费 | 178篇 |
国内免费 | 140篇 |
专业分类
化学 | 489篇 |
晶体学 | 91篇 |
力学 | 46篇 |
综合类 | 20篇 |
数学 | 13篇 |
物理学 | 442篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 81篇 |
2021年 | 62篇 |
2020年 | 24篇 |
2019年 | 29篇 |
2018年 | 29篇 |
2017年 | 22篇 |
2016年 | 51篇 |
2015年 | 34篇 |
2014年 | 43篇 |
2013年 | 67篇 |
2012年 | 52篇 |
2011年 | 52篇 |
2010年 | 49篇 |
2009年 | 52篇 |
2008年 | 47篇 |
2007年 | 64篇 |
2006年 | 61篇 |
2005年 | 39篇 |
2004年 | 48篇 |
2003年 | 28篇 |
2002年 | 30篇 |
2001年 | 27篇 |
2000年 | 24篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 15篇 |
1996年 | 4篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1981年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1101条查询结果,搜索用时 15 毫秒
1.
The possibility of realizing SASE Free Election Laser in x-ray waveband with EM-wave wiggler is studied in this paper. SASE effect including saturation length, saturation power and nonlinear process is explored through a 3-D simulation code. A utilization of seed light from laser plasma x-ray is also analyzed, which demonstrates the feature of shortening the interaction length for saturation. The results show that sizeable output power of x-ray laser would be generated with a middle energy electron beam. 相似文献
2.
A two-step swelling procedure was adopted to synthesize mono-dispersed and highly cross-linked poly (St-divinylbenzene) particles
with PSt micro-spheres (1.80 μm in diameter). The PSt micro-spheres were prepared by a dispersion polymerization method and
used as seeds. The effects of monomer concentration, ratio of ethanol to water, swelling reagents, crosslinking reagents,
swelling temperature and agitation speed on particle size were investigated in detail. The morphologies and size distributions
of these micro-spheres were examined by SEM and particle size analysis (PSA). The T
g of the micro-spheres was measured by DSC. The results indicate that the particles (6.20 μm in diameter) exhibit excellent
mono dispersed property and high crosslinking degree when the concentration of the swelling reagent was 25%, the concentration
of the crosslinking reagents was 23%, the swelling temperature was 30°C and the stirring speed was 150 r/min.
__________
Translated from Chinese Journal of Applied Chemistry, 2007, 24(11): 1289–1294 相似文献
3.
新疆野生黑加仑与马林果实的营养成分分析 总被引:2,自引:0,他引:2
通过对新疆野生黑加仑和野生马林的脂肪油,8种微量元素,17种氨基酸以及维生素C的含量进行测定得出:黑加仑脂肪油含量为17.9%,马林的脂肪油含量为22.3%,其中,黑加仑脂肪油中,r-亚麻酸的含量为19.02%,而马林中,其含量为9.40%,黑加仑中K,Na,Ca,Cu,Zn,Fe的含量比马林中的含量高,而Mn,Mg元素的含量却比马林含量低;马林的维生素C含量为16.22mg/g,黑加仑的含量为108mg/g,黑加仑的氨基酸的总量为1.63%,马林为1.14%。 相似文献
4.
本文对用C-V法提取SiC隐埋沟道MOSFET沟道载流子浓度的方法进行了理论和实验分析. pn结的存在所造成的埋沟MOS结构C-V曲线的畸变为沟道载流子浓度的提取带来一些问题. SiC/SiO2界面上界面态的存在也会使提取出的数值与实际数值产生偏差. 本文首先从理论上分别分析了沟道深度和界面态对沟道载流子浓度提取结果的影响,然后对两种沟道深度的埋沟MOS结构C-V曲线进行了测试,提取出了沟道掺杂浓度. 在测试中,采用不同的扫描速率,分析了界面态对提取结果的影响. 理论分析结果和实验测
关键词:
C-V法
SiC
隐埋沟道MOSFET
沟道载流子浓度 相似文献
5.
通过对气吹式精密播种机田间试验资料的相关分析,发现合格指数A与|D-M|(重播指数与漏播指数之差的绝对值)之间里极显著负相关(r=-0.9312)。在对数据作进一步回归分析的基础上,本文建立了一套“由排种粒数预测排种质量”的方法。 相似文献
6.
本文应用表面分析技术研究HL-1装置中SiC涂层的等离子体辐照性能。结果表明,SiC材料应用于孔栏和壁涂层有利于减少杂质和提高等离子体品质。 相似文献
7.
I. Tsiaoussis N. Frangis C. Manolikas T.A. Nguyen Tan 《Journal of Crystal Growth》2007,300(2):368-373
Pd thin films, grown on Si-rich 6H-SiC(0 0 0 1) substrates, were studied by atomic force microscopy, electron diffraction and high-resolution transmission electron microscopy. It is concluded that the growth is successful only when all the growth process takes place at room temperature. Under these conditions a very good epitaxial growth of Pd is achieved, despite the large misfit (about 8.6%) between Pd and the substrate and the existence of a semi-amorphous layer between the thin film and the substrate. A large number of twins appear in these films. 相似文献
8.
Balek V. Zeleňák V. Mitsuhashi T. Bakardjieva S. Šubrt J. Haneda H. 《Journal of Thermal Analysis and Calorimetry》2002,67(1):83-89
Results of emanation thermal analysis (ETA) characterizing microstructure changes of SiC based materials during heat treatment in argon are demonstrated. This method made it possible to reveal fine changes of the texture of SiC nano-sized powders, SiC micro-sized powders and SiC whiskers under in situconditions of the heating. ETA curves can serve as fingerprints of the respective samples.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
9.
用等离子体增强化学气相沉积(PECVD)的方法,以固定的氢气(H2)流量和不同的硅烷(SiH4)和甲烷(CH4)流量比沉积了一系列的氢化非晶SiC(a-Si,C1-x-H)膜。用这种宽带隙的a-SixC1-x-H材料作为掺铒的基体材料,通过离子注入的方法得到掺铒的a-SixC1-x-H(a-SixC1-x-H:Er)膜。注入以后的样品经过不同温度的退火。用X射线光电子能谱(XPS)、红外吸收光谱(IR)、拉曼散射谱(Raman)等技术研究不同的SiH4/CH4流量比和退火温度对a-SixC1-x-H:Er发光强度的影响。结果表明,高温退火引起了膜中C的分凝,对饵的发光是不利的。通过低温和室温下铒发光强度的比较,表明这种材料具有较弱的温度猝灭效应。 相似文献
10.
《Surface and interface analysis : SIA》2003,35(6):491-495
We performed a systematic study of ion‐implanted 6H‐SiC standards to find the optimal regimes for SIMS analysis. Relative sensitivity factors (RSFs) were acquired for operating conditions typical of practical SIMS applications. The experimental SiC RSFs were compared with those found for silicon: 1 the matrix effect was insignificant in most cases. It was found that the SiO? cluster ion cannot represent correctly the real oxygen distribution in SiC. The physics of the effect is discussed. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献