全文获取类型
收费全文 | 228篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
化学 | 161篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 19篇 |
物理学 | 50篇 |
出版年
2023年 | 9篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 14篇 |
2012年 | 27篇 |
2011年 | 26篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 21篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 4篇 |
1990年 | 1篇 |
1987年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有239条查询结果,搜索用时 16 毫秒
71.
We demonstrate efficient generation of high-order anti-Stokes Raman sidebands in a highly transient regime, using a pair of approximately 100-fs laser pulses tuned to Raman resonance with vibrational transitions in methane or hydrogen. The use of this technique looks promising for efficient subfemtosecond pulse generation. 相似文献
72.
Bedini E De Castro C Erbs G Mangoni L Dow JM Newman MA Parrilli M Unverzagt C 《Journal of the American Chemical Society》2005,127(8):2414-2416
Many phytopathogenic bacteria display lipopolysaccharides (LPS) with the O-chain repeating unit [alpha-l-Rha-(1-->3)-alpha-l-Rha-(1-->3)-alpha-l-Rha-(1-->2)](n)(). This trisaccharide unit was synthesized and oligomerized to obtain hexa- and nonasaccharides. The deprotected rhamnans were effective in suppressing the hypersensitive response (HR) and in inducing PR-1 gene expression in Arabidopsis thaliana. Conformational analysis of the oligorhamnans by NMR spectroscopy and molecular dynamics calculations revealed that a coiled structure develops with increasing chain length of the oligosaccharide. This is associated with increasing efficacy in HR suppression and PR-1 gene expression. We therefore infer that the coiled structure of phytopathogenic bacteria is a plant-recognizable pathogen-associated molecular pattern (PAMP). 相似文献
73.
da Silva Bruno Fonseca da Silva Karolayne Esthefany Melo de Farias Emerson Emiliano Gualberto de França Elvis Joacir Martins Mônica Cristina Barroso de Oliveira Santos Mariana Luiza de Lourdes Lacerda Buril Maria da Silva Alves Gustavo Gabriel de Oliveira Silva Andrezza Karla de Lira Júnior Ednaldo Barbalho da Silva Nicácio Herique Pereira Eugênia C. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(9):3671-3679
Journal of Radioanalytical and Nuclear Chemistry - This study aimed to evaluate the effects of the Rn-222 progeny on the lichen Cladonia verticillaris under controlled conditions. The results... 相似文献
74.
75.
76.
Rita Traversi Silvia Becagli Emiliano Castellano Ombretta Largiuni Alessio Migliori Mirko Severi 《International journal of environmental analytical chemistry》2013,93(6-7):457-470
The chemical analysis of shallow firn cores sampled in coastal and plateau areas in Northern Victoria Land and along a transect from Talos Dome to Dome C (East Antarctica, Pacific Ocean sector) allowed a global view of spatial and temporal changes in chemical composition of snow depositions over the last 100 years. Variations in concentration of primary (sea spray) and secondary (biogenic emission, atmospheric inputs) source markers were observed and discussed as a function of distance from the sea and altitude. In the stations characterized by relatively high snow accumulation rates, the sub-sampling resolution was sufficient to obtain a stratigraphic dating by using the periodical variations of seasonal markers. In these stations, a subdivision in “summer” and “winter” samples was carried out in order to study the seasonal changes of the contributions of the measured compounds to the snow composition as elevation and distance from the sea increase. Some evidence of post-depositional effects which are able to change the original deposition of chloride and nitrate, was observed at stations with low accumulation rates. The reliability of the depth/concentration profile of these substances for reconstructing past deposition was also discussed. 相似文献
77.
A Semisynthetic Approach to New Immunoadjuvant Candidates: Site‐Selective Chemical Manipulation of Escherichia coli Monophosphoryl Lipid A 下载免费PDF全文
Dr. Daniele D'Alonzo Manuela Cipolletti Giulia Tarantino Marcello Ziaco Dr. Giuseppina Pieretti Prof. Alfonso Iadonisi Prof. Giovanni Palumbo Dr. Alberto Alfano Dr. Mariateresa Giuliano Prof. Mario De Rosa Prof. Chiara Schiraldi Dr. Marcella Cammarota Prof. Michelangelo Parrilli Dr. Emiliano Bedini Prof. Maria M. Corsaro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):11053-11063
A semisynthetic approach to novel lipid A derivatives from Escherichia coli (E. coli) lipid A is reported. This methodology stands as an alternative to common approaches based exclusively on either total synthesis or extraction from bacterial sources. It relies upon the purification of the lipid A fraction from fed‐batch fermentation of E. coli, followed by its structural modification through tailored, site‐selective chemical reactions. In particular, modification of the lipid pattern and functionalization of the phosphate group as well as of the sole primary hydroxyl group were accomplished, highlighting the unusual reactivity of the molecule. Preliminary investigations of the immunostimulating activity of the new semisynthetic lipid A derivatives show that some of them stand out as promising, new immunoadjuvant candidates. 相似文献
78.
Mauro Panunzio Emiliano Tamanini Yves St‐Denis Fabio Maria Sabbatini Romano Di Fabio Zhining Xia 《合成通讯》2013,43(23):4239-4244
Nitrogen‐containing heterocycles bearing a halogen substituent have been converted to the corresponding amines by a synthetic protocol based on Buchwald methodology assisted by microwaves. 相似文献
79.
80.
Andrea Bencini Claudia Giorgi Emiliano Romagnoli Carlos Lodeiro André Saint-Maurice 《Supramolecular chemistry》2013,25(2):277-285
Abstract The synthesis of a new cylindrical macrotricyclic ligand (L) based upon two 1,4,7,13-tetramethyl-1,4,7,10,13,16-hexaazacyclooctadecane rings connected via two azobenzene pillars is described. The ligands displays photoelastic properties: light absorption at 366 nm produces trans→cis isomerization of the azobenzene moieties with formation of trans-cis (L E-Z ) and cis-cis (L Z-Z ) isomers. Recovery of the thermodynamically more stable trans-trans (L E-E ) isomer can be obtained by thermal back-isomerization or visible light (430 nm) absorption. The isomeric composition of L solution depends upon pH: for pH < 5.5 the L E-E form is the unique species in solution, while increasing amounts of Z species are formed at increasing pH. The protonation constants of L E-E have been determined in 0.1 mol dm?3 Me4NNO3 solution at 298.1 ± 0.1 K. The protonated species of L form stable inclusion complexes with anionic species such as [Co(CN)6]3?. 相似文献