全文获取类型
收费全文 | 1265篇 |
免费 | 264篇 |
国内免费 | 120篇 |
专业分类
化学 | 411篇 |
晶体学 | 16篇 |
力学 | 59篇 |
综合类 | 9篇 |
数学 | 88篇 |
物理学 | 486篇 |
无线电 | 580篇 |
出版年
2023年 | 8篇 |
2022年 | 29篇 |
2021年 | 44篇 |
2020年 | 60篇 |
2019年 | 56篇 |
2018年 | 56篇 |
2017年 | 69篇 |
2016年 | 52篇 |
2015年 | 84篇 |
2014年 | 79篇 |
2013年 | 100篇 |
2012年 | 78篇 |
2011年 | 83篇 |
2010年 | 84篇 |
2009年 | 73篇 |
2008年 | 78篇 |
2007年 | 79篇 |
2006年 | 73篇 |
2005年 | 49篇 |
2004年 | 40篇 |
2003年 | 53篇 |
2002年 | 42篇 |
2001年 | 60篇 |
2000年 | 48篇 |
1999年 | 36篇 |
1998年 | 27篇 |
1997年 | 22篇 |
1996年 | 20篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有1649条查询结果,搜索用时 312 毫秒
71.
72.
近红外光谱技术作为一种新型的分析检测技术,正在获得越来越广泛的应用。本文阐述了近红外光谱技术的基本原理、具体检测步骤和国内近红外光谱技术在牛奶及乳制品质量分析方面应用的最新研究进展。对目前研究存在的问题进行了分析,对以后进一步的研究进行了展望,并提出了一些建议。 相似文献
73.
74.
近红外快速水份检测技术的应用 总被引:1,自引:0,他引:1
近红外检测技术是目前发展最快和最具有前景的分析技术之一,简要介绍了近红外检测技术的发展、优点和原理.利用该技术设计了豆类产品的水份检测仪器.并对近红外技术在水果、蔬菜、奶制品、制药和化工等方面的应用前景做了展望. 相似文献
75.
76.
77.
Advances in vibrational spectroscopy have propelled new insights into the molecular composition and structure of biological tissues. In this review, we discuss common modalities and techniques of vibrational spectroscopy, and present key examples to illustrate how they have been applied to enrich the assessment of connective tissues. In particular, we focus on applications of Fourier transform infrared (FTIR), near infrared (NIR) and Raman spectroscopy to assess cartilage and bone properties. We present strengths and limitations of each approach and discuss how the combination of spectrometers with microscopes (hyperspectral imaging) and fiber optic probes have greatly advanced their biomedical applications. We show how these modalities may be used to evaluate virtually any type of sample (ex vivo, in situ or in vivo) and how “spectral fingerprints” can be interpreted to quantify outcomes related to tissue composition and quality. We highlight the unparalleled advantage of vibrational spectroscopy as a label-free and often nondestructive approach to assess properties of the extracellular matrix (ECM) associated with normal, developing, aging, pathological and treated tissues. We believe this review will assist readers not only in better understanding applications of FTIR, NIR and Raman spectroscopy, but also in implementing these approaches for their own research projects. 相似文献
78.
79.
Organic Crystals with Near‐Infrared Amplified Spontaneous Emissions Based on 2′‐Hydroxychalcone Derivatives: Subtle Structure Modification but Great Property Change
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xiao Cheng Kai Wang Shuo Huang Dr. Houyu Zhang Prof. Dr. Hongyu Zhang Prof. Dr. Yue Wang 《Angewandte Chemie (International ed. in English)》2015,54(29):8369-8373
A series of highly efficient deep red to near‐infrared (NIR) emissive organic crystals 1 – 3 based on the structurally simple 2′‐hydroxychalcone derivatives were synthesized through a simple one‐step condensation reaction. Crystal 1 displays the highest quantum yield (Φf) of 0.32 among the reported organic single crystals with an emission maximum (λem) over 710 nm. Comparison between the bright emissive crystals 1 – 3 and the nearly nonluminous compounds 4 – 7 clearly gives evidence that a subtle structure modification can arouse great property changes, which is instructive in designing new high‐efficiency organic luminescent materials. Notably, crystals 1 – 3 exhibit amplified spontaneous emissions (ASE) with extremely low thresholds. Thus, organic deep red to NIR emissive crystals with very high Φf have been obtained and are found to display the first example of NIR fluorescent crystal ASE. 相似文献
80.
《Analytical letters》2012,45(13):2447-2464
Abstract In this mini‐review we highlight two aspects of ionic liquids that to date have either no or limited studies. They are (1) exploitation of unique features of ionic liquids to develop novel spectroscopic methods and (2) development of novel spectroscopic methods, for the sensitive and accurate determination of thermal physical properties of ionic liquids. In the first category, we will describe several novel methods which were developed utilizing unique properties of ionic liquids for measurements which are not possible otherwise. They include the sensitive and accurate method to determine enantiomeric compositions of a variety of pharmaceutical products with different size, shape, and functional groups. This method is based on the use of a chiral IL which serves both as a solvent and also as a chiral selector. Ionic liquids have also been successfully used to substantially enhance the sensitivity of thermal lens measurements. In the second category, we will describe recent development in which transient grating technique and thermal lens technique have been successfully used for the sensitive, accurate, nondestructive determination of thermal physical properties of ILs. 相似文献