全文获取类型
收费全文 | 6222篇 |
免费 | 295篇 |
国内免费 | 34篇 |
专业分类
化学 | 3658篇 |
晶体学 | 23篇 |
力学 | 192篇 |
数学 | 1196篇 |
物理学 | 1035篇 |
无线电 | 447篇 |
出版年
2024年 | 6篇 |
2023年 | 66篇 |
2022年 | 139篇 |
2021年 | 196篇 |
2020年 | 176篇 |
2019年 | 170篇 |
2018年 | 149篇 |
2017年 | 131篇 |
2016年 | 271篇 |
2015年 | 241篇 |
2014年 | 262篇 |
2013年 | 363篇 |
2012年 | 443篇 |
2011年 | 481篇 |
2010年 | 291篇 |
2009年 | 273篇 |
2008年 | 395篇 |
2007年 | 364篇 |
2006年 | 333篇 |
2005年 | 307篇 |
2004年 | 242篇 |
2003年 | 186篇 |
2002年 | 195篇 |
2001年 | 77篇 |
2000年 | 50篇 |
1999年 | 71篇 |
1998年 | 52篇 |
1997年 | 68篇 |
1996年 | 50篇 |
1995年 | 49篇 |
1994年 | 47篇 |
1993年 | 36篇 |
1992年 | 29篇 |
1991年 | 29篇 |
1990年 | 22篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 26篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 16篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有6551条查询结果,搜索用时 15 毫秒
991.
Thominet O Baker JR Britton H Etheridge ZC Soscia MG Caddick S 《Organic & biomolecular chemistry》2007,5(22):3703-3712
We present herein our recent efforts towards the synthesis of epoxydiynes which represent an unusual structural feature of the neocarzinostatin chromophore. A number of different routes to these epoxydiynes have been explored with varying success. Ultimately a concise and convergent approach was developed, which involved the addition of an allenyl zinc bromide to propargylic ketones/aldehydes followed by epoxide formation. This new protocol enabled us to synthesise a fully elaborated epoxydiyne which will find application for our studies towards the total synthesis of the NCS chromophore. 相似文献
992.
We report on the use of EPR spectroscopy and spin trapping technique to detect free radical intermediates formed in the presence of gold nanoparticles. Phosphine- and amine-protected gold nanoparticles were found to initiate air oxidation of organic substrates containing active hydrogen atoms, such as amines and phosphine oxides. Nanoparticles protected by stronger bound ligands (e.g., thiols) were inactive in these reactions. We also found that gold nanoparticles are able to abstract a halogen atom from the halogenated compounds, presumably due to the high affinity of gold metal for halogens. Reaction of Au nanoparticles with chloroform showed an unusual inverse isotope effect. The trichloromethyl spin adduct was observed when Au nanoparticles were mixed with CDCl(3) but not with CHCl(3). This unexpected behaviour suggests that C-H bond breaking is not the rate-determining step in Au-initiated hydrogen abstraction. 相似文献
993.
The effect of 1,1,1,3,3,3-hexafluoro-2-phenylpropan-2-ol (HFPP) on the persistency of sec-alkyl peroxy radicals has been investigated. The formation of a hydrogen-bonding complex between HFPP and the radical resulted in a large increase in the lifetime of the radical. This variation was accompanied by a decrease in the g-value. An enthalpy change of -3.4 kcal mol-1 was estimated for the formation of the hydrogen-bonded complex. 相似文献
994.
Dielectrophoresis for the manipulation of nanobioparticles 总被引:1,自引:0,他引:1
Dielectrophoresis (DEP) is a nondestructive electrokinetic mechanism with great potential for the manipulation of bioparticles. DEP is the movement of particles induced by polarization effects in nonuniform electric fields. Since the 1960s, this technique has been successfully used for the manipulation of microbioparticles, such as microorganisms. Moreover, due to the advances in microfabrication techniques, that allowed progressively smaller microstructures to be constructed, DEP can now be used for the manipulation of nanobioparticles. The first research studies on the DEP of nanobioparticles started in the 1990s. Since then, many research groups have carried out outstanding work with DEP of nanobioparticles such as macromolecules, virus, and spores. However, the need of a critical report that integrates these findings is evident. The aim of the present review is to depict the state-of-the-art on the use of DEP for the separation of nanobioparticles and the potential trends of novel applications of this technique. This review compiles and analyzes the significant findings obtained by many researchers. This publication is intended to provide the reader with state-of-the-art information on many research studies focused on DEP to handle nanobioparticles. 相似文献
995.
A rapid, reproducible and highly sensitive method, based on liquid chromatography mass spectrometry, was developed for the determination of the excitatory amino acid glutamic acid released in the diffusion medium of control, ischemic and mutant cells from retinas. Signal intensity of glutamic acid was enhanced by dansyl chloride derivatization giving rise to a detection limit in the order of pmol/mL. Further, in HPLC-ESI-MS detection an MS-friendly dansyl group to glutamic acid enhanced both ionization efficiency in the ESI source and collision-activated dissociation in the collision cell. The sample processing procedure included liquid-liquid extraction, derivatization with dansyl chloride and a final cation-exchange extraction to generate clean extracts for LC/MS/MS analysis. This approach has been validated as sensitive, linear (20-300 ng/mL), accurate and precise for the differential quantification of glutamic acid in the diffusion medium of retina cells. This is the first report of using chemical derivatization to enhance MS/MS detection of the glutamic acid released in the diffusion medium of wild-type and mutant retina cells, under ischemic conditions. 相似文献
996.
997.
998.
999.
1000.