全文获取类型
收费全文 | 225篇 |
免费 | 7篇 |
国内免费 | 39篇 |
专业分类
化学 | 209篇 |
力学 | 22篇 |
数学 | 7篇 |
物理学 | 33篇 |
出版年
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 20篇 |
2012年 | 14篇 |
2011年 | 22篇 |
2010年 | 11篇 |
2009年 | 19篇 |
2008年 | 15篇 |
2007年 | 21篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 1篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
排序方式: 共有271条查询结果,搜索用时 15 毫秒
1.
2.
Lida Ren Zhihao Ming Wei Zhang Yangwei Liao Xiaofeng Tang Bei Yan Huimin Lv Xianjin Xiao 《中国化学快报》2022,33(6):3043-3048
Enzyme assisted DNA probes are powerful tools in molecular diagnostics for their simplicity, rapidity,and low detection limit. However, cost of probes, difficulty in optimization and disturbance of secondary structure hindered the wider application of enzyme assisted DNA probes. To solve the problems, we designed a new system named shared-probe system. By introducing two unlabeled single stranded DNA named Sh1 and Sh2 as the bridge between probe and the substrate, the same sequence of dually lab... 相似文献
3.
《中国化学快报》2023,34(4):107742
A novel diterpenoid with an unprecedented 5/6/5/7 tetracyclic system, rhodauricanol A (1), five new grayanane-derived diterpenoids, dauricanols A?E (2?6), and five known ones (7?11) were isolated from the flowers of Rhododendron dauricum. Rhodauricanol A (1) possesses a unique 5/6/5/7 tetracyclic ring system featuring a 16-oxa-tetracyclo[11.2.1.01,5.07,13]hexadecane core. Dauricanols A?C (2?4) are the first 1,3-dioxolane conjugates of grayanane diterpenoids and 5-hydroxymethylfurfural and vanillin, respectively, and dauricanols D (5) and E (6) represent the first examples of 6-deoxy-1,5-seco-grayanane diterpenoids. Their structures were determined by spectroscopic methods, quantum chemical calculation including 13C NMR-DP4+ analysis and ECD calculation, and single-crystal X-ray diffraction analysis. Plausible biosynthetic pathways for 1?4 were proposed. All the isolates showed significant analgesic activities, and dauricanols B (3) and C (4) showed more potent analgesic activities than the positive control, morphine. 相似文献
4.
Many composite parts, such as laminated panels and grid-like shells, operate under high mechanical loading. Evaluation of their structural integrity is crucial to ensure the long-lasting operation of critical components. Since testing a structure under full or “proof” load might be dangerous for personnel, it would be preferable to use a remote, rapid inspection technique. This paper describes a practical application of IR thermography to the inspection of large composite parts used in the aerospace industry. This work has used just one cycle of increasing load from zero load to failure, and this was done for both for tensile and compressive loads. It is shown that, during the formation of micro-defects in polymeric composites, about 40 % of the total dissipated energy is expended for material heating, while about 60 % is related to material damage accompanied by an increase in the defect concentration. Non-uniform composite deformation causes temperature anomalies, whose amplitude may reach 1.5–2.5 °C at a load of about 50–60 % of the limit load. 相似文献
5.
6.
冲蚀与气蚀复合磨损试验研究 总被引:2,自引:4,他引:2
通过改造MCF-30型冲蚀腐蚀试验机,建立了水、沙、气三相流冲蚀磨损试验装置;试验研究了水、沙混合流场中试样的磨损特征,通过扫描电子显微镜观测了三相流冲蚀磨损表面,并借助计算机模拟分析水、沙混合条件下产生气蚀破坏的条件.结果表明:合理的设计可以实现冲蚀与气蚀的复合磨损模拟试验;形成三相流共同作用下的冲蚀与气蚀复合磨损重要条件为介质中含有较多气体,并且在试样中有气泡溃灭.三相流磨损模拟试验与仿真为进一步开展三相流气蚀与冲蚀磨损研究奠定了基础. 相似文献
7.
A simple and sensitive HPLC method using UV detection was developed to determine the concentration of protoapigenone in rat plasma. Chromatographic separation was conducted on a C18 column with a mobile phase consisting of an acetonitrile–methanol–aqueous phase (containing 0.2% acetic acid, pH 3.0) system at a flow rate of 1.0 mL/min. The UV detector was set at 248 nm. The calibration curve was linear over the range of 0.031–10.0 µg/mL. The lower limit of quantification was 31 ng/mL. The recoveries for plasma samples ranged from 70.3 to 82.5%. The intra‐ and inter‐day accuracy and precision fulfilled the international standards. This method was successfully applied to a pharmacokinetic study of protoapigenone in rats after oral administration of protoapigenone. It was shown that protoapigenone could be absorbed rapidly after oral administration and could reach the maximum concentration within 1 h. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
8.
In this review the focus is on application of porous monoliths to miniaturized extraction of biological analysis, with emphasis
on porous monolithic materials and different miniaturized extraction formats. The general approaches used to synthesize organic
polymer and silica monolithic materials are highlighted, and their properties and applicability are described and compared.
Several extraction formats, including in-tube microextraction, chip-based microextraction, tip-based microextraction, among
others, are reviewed in depth. 相似文献
9.
In this study, we investigated the differences in the crystallinity of starch films (mung bean, water chestnut, sweet potato, and cassava starches) with different moisture contents stored in different humidity conditions (11%, 22%, 33%, 43%, 54%, 75%, and 84%) and evaluated their thermal adhesion and sealing properties. X-ray diffraction analysis revealed an association between the degree of crystallinity and the moisture content in starch films: crystallinity decreased with an increase in the moisture content. Field Emission Scanning Electron Microscopy (FE-SEM) analysis showed that films with low moisture content failed to completely adhere, but films with a high moisture content and lower crystallinity showed good adherence, with two films perfectly adhered at the same temperature because water molecules acted as a mobility enhancer. The peeling test demonstrated the failure modes of the heat-bound films. The cassava starch film, which had a low amylose content and crystallinity, showed better adhesion compared to other starch films. 相似文献
10.