全文获取类型
收费全文 | 416篇 |
免费 | 23篇 |
专业分类
化学 | 352篇 |
力学 | 9篇 |
数学 | 30篇 |
物理学 | 48篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 13篇 |
2014年 | 33篇 |
2013年 | 32篇 |
2012年 | 20篇 |
2011年 | 47篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 17篇 |
2007年 | 19篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 11篇 |
2002年 | 23篇 |
2001年 | 5篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有439条查询结果,搜索用时 15 毫秒
431.
Phenolic profile of edible honeysuckle berries (genus lonicera) and their biological effects 总被引:1,自引:0,他引:1
Jurikova T Rop O Mlcek J Sochor J Balla S Szekeres L Hegedusova A Hubalek J Adam V Kizek R 《Molecules (Basel, Switzerland)》2011,17(1):61-79
The current status of research on polyphenolic compounds in the berries of edible honeysuckle and their biological effects, including recommended utilization, are reviewed. The major classes of phenolic compounds in the blue berried honeysuckle are flavonols (quercetin, rutin, quercitrin) and flavanes (proanthocyanidins, catechins) and anthocyanins. Cyanidin-3-glucoside and cyanidin-3-rutinoside are considered as major anthocyanidins in edible honeysuckle berries. Such a high level of antioxidant activity in the berries of different species of the genus Lonicera is especially due to the high level of polyphenolic compounds, especially anthocyanins. These berries seem to be prospective sources of health-supporting phytochemicals that exhibit beneficial anti-adherence and chemo-protective activities, thus they may provide protection against a number of chronic conditions, e.g., cancer, diabetes mellitus, tumour growth or cardiovascular and neurodegenerative diseases. 相似文献
432.
Ondrej Zitka Sylvie Skalickova Sona Krizkova Marcela Vlkova Vojtech Adam Rene Kizek 《Chromatographia》2013,76(11-12):611-619
In this study, we optimized method for the isolation and detection of lactoferrin from human saliva using 3 mm short monolithic disc. We optimized the conditions for separation as flow rate 4 mL min?1 and ionic strength of effluent as 2 M·NaCl. We estimated limit of detection of whole method, which was hyphenated to the Bradford’s assay, down to 100 ng mL?1. The purity of the isolated fractions was verified by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and recovery of isolation was found to be 51 % using minimally processed sample of saliva. Further, we tested the optimized method on group of healthy volunteers (n = 7). We were able to distinguish between the healthy subjects and subject suffering from celiac disease, which reported at least 2.5× higher level of lactoferrin in comparison to healthy ones. The results were correlated with standard enzyme-linked immunosorbent assay (ELISA) kit with obtained correlation coefficient R 2 = 0.8446. Analysis of lactoferrin in saliva by monolithic disc and subsequent offline photometric detection is faster and cheaper method compared to ELISA commercial kit. The total analysis of one sample takes <20 min. 相似文献
433.
Hector Rene Vega-Carrillo Antonio Baltazar-Raigosa 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(1):323-327
Photoneutron spectra around an 18 MV LINAC were calculated in order to observe the effect produced by media around the accelerator.
Calculations were carried out with MCNP 4C code, three different cases were analyzed: Head model, Head and phantom model,
and Head, air, phantom and wall model. The spectra were calculated in five detectors located at the irradiation room at different
distances from the isocentre. A sixth detector, located near the entrance door was included to analyze how the maze change
the neutron spectrum. Neutrons are mainly produced in the LINAC head change the shape of evaporation neutrons from the source
term, some of these neutrons leak out the head with lesser energy, another neutrons goes with the treatment beam. At any site
near the isocentre neutron spectrum has evaporation and thermal neutrons joined by a set of epithermal neutrons. As the distance
from the isocentre increases evaporation neutrons tend to decrease while, epithermal and thermal neutrons tend to remain constant
regardless de distance due to room return produced by the walls. The maze contributes to reduce the neutron fluence, reducing
the evaporation neutrons; resulting spectrum is mainly the contribution of thermal and epithermal neutrons. Near the door
these neutrons can produce activation and prompt gamma rays. 相似文献
434.
John Mommers Jeroen Knooren Ynze Mengerink Arno Wilbers Rene Vreuls Sjoerd van der Wal 《Journal of chromatography. A》2011,1218(21):3159-3165
In gas chromatography (GC) reproducible retention times are in many cases highly favorable or in some cases even required. In one-dimensional GC, retention time shifts can be eliminated or minimized using a procedure called retention time locking (RTL). This procedure is based on adjusting the (constant) column head pressure. Unfortunately, this RTL procedure cannot be used in comprehensive two-dimensional gas chromatography (GC × GC) given the fact that peaks will shift in both dimensions. Adjusting the column head pressure in GC × GC will only minimize or eliminate the primary retention time shifts. In this paper, a fast and easy to perform, two-step retention time locking procedure for two-dimensional gas chromatography (2D-RTL) is proposed and its feasibility is demonstrated. This 2D-RTL procedure involves adjustment of the column head pressure or constant column flow, followed by the adjustment of the so-called effective secondary column length. The secondary column length is increased or decreased, simply by moving it stepwise through the modulator. It is demonstrated that retention time shifts in both the primary- and secondary-dimension, which may occur after e.g. replacing the column set, can be minimized to less than half peak base width. The proposed 2D-RTL procedure is used successfully for approximately 1 year in our laboratory. 相似文献
435.
Masarik M Gumulec J Sztalmachova M Hlavna M Babula P Krizkova S Ryvolova M Jurajda M Sochor J Adam V Kizek R 《Electrophoresis》2011,32(24):3576-3588
Prostate cancer with altered zinc(II) cell metabolism is the second most frequently diagnosed cancer in developed countries. The alterations of zinc(II) metabolism can influence metabolism of other metal ions and can also be associated with the expression and translation of metal-binding proteins including metallothioneins. The aim of this article was to optimize immunoseparation protocol based on paramagnetic beads conjugated with protein G for the isolation of metallothionein. Isolated metallothionein was determined by differential pulse voltammetry Brdicka reaction and SDS-PAGE. Optimal conditions: antigen-binding time - 60 min, temperature - 70°C, and buffer composition and pH - acetate buffer, pH 4.3, were determined. Under the optimized conditions, lysates from 22Rv1 prostate cancer cells treated with various concentrations of cadmium(II) and copper(II) ions were analyzed. We observed strong correlation in all experimental groups and all lysate types (r>0.83 at p<0.041) between metallothionein concentration related to viability and concentration of copper(II) ions and cadmium(II) ions in medium. Moreover, the results were compared with standard sample preparation as heat treatment and SDS-PAGE analysis. 相似文献
436.
Weiyu Li Sen Li Dr. Claire Empel Prof. Dr. Rene M. Koenigs Prof. Dr. Lei Zhou 《Angewandte Chemie (International ed. in English)》2023,62(42):e202309947
A photocatalytic self-(3+2) cycloaddition of vinyldiazo compounds is described, which provides cyclopentene derivatives with conservation of one diazo functional group. Experimental insights and density functional theory indicate that the reaction is triggered by an unusual single electron oxidation of vinyldiazo compounds, while the photolysis for the generation of free carbene species is not involved. The synthetic applications of the resulting cyclopentenyl α-diazo compounds were demonstrated based on the rich chemistry of the diazo functional group. 相似文献
437.
438.
Ansgar Stratmann Thomas Schupp Christiane Toupet Wolfgang Schilling Lukas Oberer Rene Traber 《ChemInform》2002,33(41):222-222
439.