全文获取类型
收费全文 | 459篇 |
免费 | 37篇 |
国内免费 | 1篇 |
专业分类
化学 | 402篇 |
晶体学 | 2篇 |
力学 | 5篇 |
数学 | 29篇 |
物理学 | 59篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 29篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 25篇 |
2015年 | 25篇 |
2014年 | 17篇 |
2013年 | 25篇 |
2012年 | 35篇 |
2011年 | 34篇 |
2010年 | 27篇 |
2009年 | 19篇 |
2008年 | 44篇 |
2007年 | 35篇 |
2006年 | 32篇 |
2005年 | 37篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1985年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1935年 | 1篇 |
1934年 | 1篇 |
1933年 | 5篇 |
排序方式: 共有497条查询结果,搜索用时 46 毫秒
91.
In vitro microdialysis recoveries of glucose were evaluated and optimised by varying the inner cannula dimensions for a concentric type microdialysis probe. The recovery was shown to be significantly dependent on the outer radius of the inner cannula (r alpha). Increasing r alpha by 50% while holding all other microdialysis variables constant caused a 26% increase in recovery under the conditions tested. Mass transport modeling of microdialysis sampling showed that the magnitude of the recovery change in response to changes in r alpha may depend on other experimental variables such as effective dialysis length, membrane dimensions, membrane type and medium composition. These data indicate that microdialysis recovery may be substantially improved by optimising the outer diameter of the inner cannula. These data also suggest that in order to fully characterise and compare data from microdialysis experiments, r alpha should become one of the reported variables. 相似文献
92.
Lilly MJ Miller NA Edwards AJ Willis AC Turner P Paddon-Row MN Sherburn MS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(8):2525-2536
The stereochemical outcome of the intramolecular Diels-Alder reaction of ester-linked 1,3,8-nonatrienes can be controlled by substituents about a stereogenic center attached to C1. The scope and limitations of this approach have been investigated, with variation in substrate structure about the allylic stereocenter and the dienophile. The stereochemical outcomes of these reactions are explained by reference to B3 LYP/6-31G(d) transition structures. New insights into the conformational preferences of allylic alcohol derivatives are reported, results which allow an explanation of the differing levels of pi-diastereofacial selectivity and cis/trans (i.e. endo/exo) selectivity from the reaction. 相似文献
93.
1,4-Dimethyl-1,4-diphenylbutadiene was shown to be able to execute regiospecific HT-1 photoisomerization around a methyl group when irradiated in a low-temperature organic glass, albeit at reduced efficiency. 2,3-Dimethyl-1,4-diphenylbutadiene exhibited a different type of steric effect, causing the E,E-isomer to undergo regiospecific HT-1 photoisomerization. 相似文献
94.
95.
Victorin N. Mallet Monique Duguay Marc Bernier Natalie Trottier 《International journal of environmental analytical chemistry》2013,93(3):271-279
Abstract In this study isocratic high performance liquid chromatography in the reversed-phase mode (RP-8 or RP-18 column) with UV-detection (254 nm), was evaluated for the analysis, directly or after extraction, of organophosphorous pesticides in environmental water. Fifteen pesticides were studied and good resolution was obtained for eight by direct analysis of a multi-residue water sample. Reproducibility in terms of retention times was found to be very good. Linear calibration curves were obtained down to 0.5ng/μL (3 ng injected) with a coefficient of variation near 10%. The limit of quantitation for direct analysis was found to be 0.5mg/L (3ng) in water. However, by extraction with methylene chloride or ethyl acetate and concentration of the extract some of the pesticides could be determined at 0.5 μg/L (ppb) in water. 相似文献
96.
97.
98.
99.