全文获取类型
收费全文 | 206篇 |
免费 | 15篇 |
国内免费 | 16篇 |
专业分类
化学 | 28篇 |
力学 | 4篇 |
综合类 | 5篇 |
数学 | 11篇 |
物理学 | 39篇 |
无线电 | 150篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 11篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 12篇 |
2012年 | 8篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 14篇 |
2008年 | 11篇 |
2007年 | 26篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
排序方式: 共有237条查询结果,搜索用时 15 毫秒
1.
Patricia C DamianiMariano D Borraccetti Alejandro C Olivieri 《Analytica chimica acta》2002,471(1):87-96
A direct method for the simultaneous determination of naproxen and salicylate in human serum is reported, based on a combination of spectrofluorometric measurements with two multivariate calibration techniques: partial least-squares (PLS-1) and the novel net analyte preprocessing (NAP). The method is rapid, selective and sensitive, and is based on the measurement of the fluorescence spectra of NH3 alkalinized whole human sera at the excitation wavelength of 315 nm. It can be applied within the ranges of concentrations 50-200 ng ml−1 for naproxen and 100-300 ng ml−1 for salicylate. The employed chemometric techniques have been compared on the basis of the statistical indicators for calibration and validation. Reproducibility and interference studies in abnormal sera have also been carried out. 相似文献
2.
3.
4.
本文采用一种自动条纹分析的预处理方法,对噪音相应图中的莫尔条纹密度和方向的估计进行了分析研究。这些信息能用来构造相位-跳转-保存-过滤方法,提高二维展开相位法的性能以及可以使用坚固片断的相位数据。这种方法的特点是:对噪音反应非常灵敏,测试和参数的估算都要在在傅里叶范围内进行并可以做成模型用于估算研究。 相似文献
5.
6.
图像去噪是图像处理中的重要组成部分.目前,针对点目标检测,人们已经发展了一系列比较成熟的滤波预处理算法.本文通过对红外点目标图像预处理方法的研究,给出了两种基于差分的背景抑制算法.最后针对仿真结果,对这两种背景抑制方法的去噪性能进行了分析比较. 相似文献
7.
8.
提出了一种基于Daubechies小波软阈值的近红外光谱预处理方法,并用该方法处理了两类不同苹果的近红外光谱数据。该方法选用归一化相关系数(Normalized Correlation,NC)和峰值信噪比(Peak Signal to Noise Ratio,PSNR)作为定量分析指标.与常用的矢量归一化法(Vector Normalization,VN)和标准正态变量校正法(Standard normal Variate,SNV)相比,该方法优势明显,既能有效去除噪声,又能很好地保留光谱的特征细节信息,提高了后续光谱分析过程中建模的稳健性和模型预测的精确度. 相似文献
9.
Johanne Heitmann Solheim Boris Zimmermann Valeria Tafintseva Simona Dzurendov Volha Shapaval Achim Kohler 《Molecules (Basel, Switzerland)》2022,27(6)
Extended multiplicative signal correction (EMSC) is a widely used preprocessing technique in infrared spectroscopy. EMSC is a model-based method favored for its flexibility and versatility. The model can be extended by adding constituent spectra to explicitly model-known analytes or interferents. This paper addresses the use of constituent spectra and demonstrates common pitfalls. It clarifies the difference between analyte and interferent spectra, and the importance of orthogonality between model spectra. Different normalization approaches are discussed, and the importance of weighting in the EMSC is demonstrated. The paper illustrates how constituent analyte spectra can be estimated, and how they can be used to extract additional information from spectral features. It is shown that the EMSC parameters can be used in both regression tasks and segmentation tasks. 相似文献
10.
Kristoffer Laursen Søren Søndergaard Frederiksen Casper Leuenhagen Rasmus Bro 《Journal of chromatography. A》2010,1217(42):6503-6510
It is common practice in chromatographic purity analysis of pharmaceutical manufacturing processes to assess the quality of peak integration combined by visual investigation of the chromatogram. This traditional method of visual chromatographic comparison is simple, but is very subjective, laborious and seldom very quantitative. For high-purity drugs it would be particularly difficult to detect the occurrence of an unknown impurity co-eluting with the target compound, which is present in excess compared to any impurity. We hypothesize that this can be achieved through Multivariate Statistical Process Control (MSPC) based on principal component analysis (PCA) modeling. In order to obtain the lowest detection limit, different chromatographic data preprocessing methods such as time alignment, baseline correction and scaling are applied. Historical high performance liquid chromatography (HPLC) chromatograms from a biopharmaceutical in-process analysis are used to build a normal operation condition (NOC) PCA model. Chromatograms added simulated 0.1% impurities with varied resolutions are exposed to the NOC model and monitored with MSPC charts. This study demonstrates that MSPC based on PCA applied on chromatographic purity analysis is a powerful tool for monitoring subtle changes in the chromatographic pattern, providing clear diagnostics of subtly deviating chromatograms. The procedure described in this study can be implemented and operated as the HPLC analysis runs according to the process analytical technology (PAT) concept aiming for real-time release. 相似文献