全文获取类型
收费全文 | 30篇 |
免费 | 109篇 |
国内免费 | 9篇 |
专业分类
化学 | 12篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 3篇 |
物理学 | 131篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 11篇 |
2011年 | 11篇 |
2010年 | 20篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 13篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 31 毫秒
101.
A new analytical model for reverse characteristics of
4H--SiC merged PN--Schottky diodes (MPS or JBS) is developed. To
accurately calculate the reverse characteristics of the 4H--SiC MPS
diode, the relationship between the electric field at the Schottky
contact and the reverse bias is analytically established by solving
the cylindrical Poisson equation after the channel has pinched off.
The reverse current density calculated from the
Wentzel--Kramers--Brillouin (WKB) theory is verified by comparing it
with the experimental result, showing that they are in good
agreement with each other. Moreover, the effects of P-region spacing
(S) and P-junction depth (Xj) on the characteristics of 4H--SiC MPS
are analysed, and are particularly useful for optimizing the
design of the high voltage MPS diodes. 相似文献
102.
Efficient thermal analysis method for large scale compound semiconductor integrated circuits based on heterojunction bipolar transistor 下载免费PDF全文
In this paper, an efficient thermal analysis method is presented for large scale compound semiconductor integrated circuits based on a heterojunction bipolar transistor with considering the change of thermal conductivity with temperature.The influence caused by the thermal conductivity can be equivalent to the increment of the local temperature surrounding the individual device. The junction temperature for each device can be efficiently calculated by the combination of the semianalytic temperature distribution function and the iteration of local temperature with high accuracy, providing a temperature distribution for a full chip. Applying this method to the InP frequency divider chip and the GaAs analog to digital converter chip, the computational results well agree with the results from the simulator COMSOL and the infrared thermal imager respectively. The proposed method can also be applied to thermal analysis in various kinds of semiconductor integrated circuits. 相似文献
103.
104.
Spectroscopic and scanning probe analysis on large-area epitaxial graphene grown under pressure of 4 mbar on 4H-SiC (0001) substrates 下载免费PDF全文
We produced epitaxial graphene under a moderate pressure of 4 mbar(about 400 Pa) at temperature 1600℃. Raman spectroscopy and optical microscopy were used to confirm that epitaxial graphene has taken shape continually with slight thickness variations and regularly with a centimeter order of magnitude on 4H-SiC(0001) substrates. Then using X-ray photoelectron spectroscopy and Auger electron spectroscopy, we analyzed the chemical compositions and estimated the layer number of epitaxial graphene. Finally, an atomic force microscope and a scanning force microscope were used to characterize the morphological structure. Our results showed that under 4-mbar pressure, epitaxial graphene could be produced on a SiC substrate with a large area, uniform thickness but a limited morphological property. We hope our work will be of benefit to understanding the formation process of epitaxial graphene on SiC substrate in detail. 相似文献
105.
Raman analysis of epitaxial graphene grown on 4Hben SiC (0001) substrate under low pressure condition 下载免费PDF全文
In this paper, we report a feasible route of growing epitaxial graphene on 4H-SiC (0001) substrate in a low pressure of 4 mbar (1 bar=105 Pa) with an argon flux of 2 standard liters per minute at 1200, 1300, 1400, and 1500 ℃ in a commercial chemical vapour deposition SiC reactor. Using Raman spectroscopy and scanning electron microscopy, we confirm that epitaxial graphene evidently forms on SiC surface above 1300 ℃ with a size of several microns. By fitting the 2D band of Raman data with two-Lorentzian function, and comparing with the published reports, we conclude that epitaxial graphene grown at 1300 ℃ is four-layer graphene. 相似文献
106.
采用热重质谱(TG-MS)联用技术,考察杏壳、小麦秸秆与杨树木屑等典型农林生物质的热解行为及动力学。结果表明,组分差异使得三种生物质在主要反应区间内(200–450℃)表现出不同的特征。采用等转化率法计算发现,杏壳平均活化能为188.22 kJ/mol,秸秆平均活化能为220.77 kJ/mol,木屑平均活化能为175.87 kJ/mol。利用分布活化能模型(DAEM)法计算生物质中各组分的平均活化能,发现三种生物质中存在平均活化能较高的第四组分(杏壳297.44 kJ/mol、秸秆284.35 kJ/mol和木屑309.96 kJ/mol),而半纤维素与纤维素呈现“秸秆<杏壳<木屑”规律。各类动力学计算方法能够互为补充,等转化率方法的整体计算结果与单组分分布活化能模型法结果接近,方法更简便,而分布活化能模型法可以求得原料不同组分的动力学参数,弥补等转化率法的不足,综合使用可以形成对热解反应更为全面的认识。 相似文献
107.
用碘量法测定复杂含硒物料中常量硒并对测定条件做试验。试样经硝酸及硫酸溶解、蒸发至冒烟后,盐类溶于盐酸中。在酒石酸存在下加盐酸羟胺,于70℃保温1h,放置1.5h使硒还原为单质硒并陈化。过滤,将单质硒溶于盐酸中,溶解温度为90℃,溶解时间为5min,滴定时溶液酸度宜在0.2~0.5mol·L-1(盐酸介质)。滴定时采用分步滴加碘化钾溶液,随即用硫代硫酸钠标准溶液滴定至淀粉指示剂所显蓝色消失,至再次加入碘化钾无蓝色出现为终点。按所耗硫代硫酸钠标准溶液的体积计算试样的含硒量。 相似文献
108.
109.
110.