全文获取类型
收费全文 | 57篇 |
免费 | 0篇 |
国内免费 | 5篇 |
专业分类
化学 | 22篇 |
力学 | 1篇 |
数学 | 4篇 |
物理学 | 35篇 |
出版年
2018年 | 1篇 |
2017年 | 2篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有62条查询结果,搜索用时 62 毫秒
22.
针对时间延时积分电荷耦合器件积分级数对成像质量的影响,提出了一种航天遥感相机中时间延时积分电荷耦合器件积分级数的最优选择方法.构造了典型成像系统的信噪比与积分级数关系模型和调制传递函数与卫星姿态角和积分级数的函数模型;以信噪比和调制传递函数的容许值为约束条件,推导出了任意条件下时间延时积分电荷耦合器件的可选积分级数区间并给出了最优的积分级数解,给出了对应的增益设置指导函数.运用仿真实验对该方法进行验证,并与传统方法进行比较,结果表明:该方法能够选取最优的积分级数,从而获得满足信噪比和调制传递函数指标的最佳成像质量;若该值不存在,依然能获取相对最佳的折中值和视觉效果;同时,本文成像效果优于传统方法. 相似文献
23.
基于面阵CCD的时间延时积分模式的空间相机自动对焦 总被引:1,自引:0,他引:1
空间面阵相机在轨运动会产生运动模糊,影响自动对焦准确率。为解决该问题,提出行间转移面阵CCD的时间延时积分(TDI)模式实现去运动模糊。选取行间转移面阵CCD KAI-1003作为成像器件,利用可编程逻辑器件(PLD)控制时序信号,匹配CCD的行转移速度与目标运动速度,实现去运动模糊。实验表明该成像系统不仅能去运动模糊而且还大幅提高图像信噪比。去运动模糊后,根据较短时间间隔内空间相机拍摄的图像有重叠区域的特点提出一种空间相机自动对焦方法。通过配准算法找出序列图像间的重叠区域,并计算重叠区域的清晰度评价值,然后根据传递特性将评价值映射到同一个评价体系中,最后找到最佳对焦位置。实验表明该成像系统对高速运动的目标能够实现自动对焦。 相似文献
24.
通过甲苯二异氰酸酯(TDI)改性多壁羟基碳纳米管并用已内酰胺封端,采用单体浇铸的方法制备MC尼龙6、改性碳纳米管纳米复合材料.红外光谱(FTIR)结果证明TDI改性后碳纳米管上成功接有异氰酸酯基团.X射线衍射(XRD)结果表明,改性碳纳米管的加入没有改变MC尼龙6结晶的品型结构;而未改性碳纳米管的加入则抑制了其α2晶的... 相似文献
25.
A series of polyurethane elastomers (PUE) incorporating TDI (toluene diisocyanate) trimer were synthesized via an in-situ polymerization and prepolymer process. It was found that for the sample with 10 wt% or less TDI trimer, the stress–strain curves of PUE exhibited the characteristics of a ductile failure with relatively high tensile strength and elongation at break. However, with incorporation 20~30 wt% of TDI trimer, the samples changed to brittle fracture. All PUE samples exhibited a loss peak corresponding to the glass transition temperature (Tg ) of the soft-segments, which shifted to higher temperature and decreased in peak height by incorporation of the three-functional isocyanurate rings. Although the TDI trimer modified PUE showed only slightly higher onset and peak degradation values than that of PUE in the absence of TDI trimer, there were still big differences in the end temperatures of the second stage. The value of activation energy and frequency factor fluctuated for varying samples, indicating that the thermal stability of PUE can be improved to a certain degree by incorporation of TDI trimer, but not so remarkably. 相似文献
26.
TDI CCD光子响应非均匀性噪音分析与测量 总被引:1,自引:0,他引:1
探测器光子响应非均匀性噪音会降低低照度情况下遥感成像系统的成像质量.针对这一现象,本文首先结合探测器的物理性质,对各种噪音源进行了研究;建立了TDI CCD不同级数下的光子响应非均匀性噪音模型,随着曝光量的增加,光子响应非均匀性噪音也线性增加.其次根据曝光级数越多TDI CCD对非均匀性噪音的平滑效应越明显这一现象,提出一种光子响应非均匀性系数与曝光级数之间的关系式,并给出了利用TDI CCD输出图像提取光子响应非均匀性噪音的方法.最后建立了试验系统,通过试验对测试获得的光子响应非均匀性噪音与理论分析计算得出的结果进行了分析. 相似文献
27.
28.
Leonid Mashlyakovskiy Vladimir Zaiviy Giovanni Simeone Claudio Tonelli 《Journal of polymer science. Part A, Polymer chemistry》1999,37(5):557-570
Urethane reactions of cycloaliphatic and aromatic diisocyanates with hydroxy‐terminated fluoropolyethers (FPEs) of various molecular weights and structure, at NCO : OH = 2, have been studied by monitoring, by IR analysis, the rate of decrease in NCO absorbance at 2264–2268 cm−1. Different diisocyanates have been tested, among them the following: 4,4′‐dicyclohexylmethane diisocyanate (H12MDI); 5‐isocyanato‐1,3,3‐trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate (IPDI); 2,4‐toluene diisocyanate (TDI). Ethyl acetate (EA), methyl isobutyl ketone (MIBK), and hexafluoroxylene (HFX) have been used as solvents in presence of dibutyltin dilaurate (DBTDL) or 1,4‐diazabicyclo[2.2.2]octane (DABCO) as catalysts. These reactions gave rise to NCO‐end‐capped FPE–oligourethanes. Preliminary solubility tests for HO‐terminated FPEs in various solvents made it possible to select proper candidates for carrying out reaction in homogeneous conditions at high concentrations of reagents (30–50% w/w). The second‐order kinetic mechanism was shown to be valid. Positive deviations from linearity for the second‐order kinetics around 40–80% conversion, found for most of the FPE diols, were attributed to the autocatalysis of the isocyanate–hydroxyl reaction by the arising urethane groups. Uncatalyzed reactions with cycloaliphatic diisocyanates are very slow at 40°C. The tertiary amine DABCO is a much less effective catalyst than DBTDL. FPEs having terminal OH groups separated from the perfluorinated main molecular chain by (OCH2CH2)n segments (n = 1–2) are generally more reactive than FPEs with end CH2OH groups. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 557–570, 1999 相似文献
29.
A. Sultan Nasar S. Subramani Ganga Radhakrishnan 《Journal of polymer science. Part A, Polymer chemistry》1999,37(12):1815-1821
N-Methylaniline-, diphenylamine-, and N-phenylnaphthylamine-blocked toluene diisocyanates (TDI) were prepared and characterized by IR, NMR spectroscopy, and nitrogen content analyses. The structure–property relationship of these adducts was established by reacting with hydroxyl-terminated polybutadiene (HTPB). The cure rate of the adduct increases from the N-phenylnaphthylamine- to diphenylamine- and to N-methylaniline-blocked TDI adduct. Simultaneous TGA/DTA results also confirm this trend, and the thermal stability of the adduct decreases in the following order: N-phenylnaphthylamine–TDI > diphenylamine–TDI > N-methylaniline–TDI. The gas chromatogram of the amine-blocked isocyanate confirms that the thermolysis products are the blocking agent and isocyanate. The solubilities of the adducts were carried out in polyether, polyester, and hydrocarbon polyols, and it was found that the N-methylaniline–TDI adduct shows higher solubility than the rest and also found that the polyester polyol shows higher solvating power against the adducts than the polyether and hydrocarbon polyols. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1815–1821, 1999 相似文献
30.