全文获取类型
收费全文 | 1371篇 |
免费 | 24篇 |
国内免费 | 16篇 |
专业分类
化学 | 820篇 |
晶体学 | 44篇 |
力学 | 58篇 |
数学 | 128篇 |
物理学 | 361篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 63篇 |
2021年 | 55篇 |
2020年 | 32篇 |
2019年 | 31篇 |
2018年 | 35篇 |
2017年 | 66篇 |
2016年 | 61篇 |
2015年 | 55篇 |
2014年 | 96篇 |
2013年 | 127篇 |
2012年 | 148篇 |
2011年 | 95篇 |
2010年 | 76篇 |
2009年 | 51篇 |
2008年 | 40篇 |
2007年 | 32篇 |
2006年 | 41篇 |
2005年 | 28篇 |
2004年 | 14篇 |
2003年 | 27篇 |
2002年 | 16篇 |
2001年 | 27篇 |
2000年 | 17篇 |
1999年 | 24篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 9篇 |
1987年 | 32篇 |
1986年 | 18篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有1411条查询结果,搜索用时 15 毫秒
171.
Heracleum sphondylium L. subsp. ternatum (Velen.) Brummitt. commonly known as “hogweed” is traditionally used to manage several human ailments. This investigation assessed, for the first time, the enzyme inhibitory properties, antioxidant activity, phytochemical profile, antimutagenic, and antimicrobial potential of the ethyl acetate, methanol, and water extracts of H. sphondylium. We also established the possible interactions of identified phenolic compounds with cholinesterases, amylase, glucosidase, and tyrosinase using in silico docking studies. Chlorogenic acid was found in high amounts in the methanol extract of H. sphondylium. The methanol extract was an effective inhibitor of acetylcholinesterase (1.70 mg galantamine equivalent (GALAE)/g extract) while the ethyl acetate extract showed pronounced inhibitory action against butyrylcholinesterase (1.77 mg GALAE/g extract). The extracts exhibited low inhibition against amylase (0.12-0.84 mmol acarbose equivalent (ACAE)/g extract) and a more pronounced inhibition against glucosidase (2.29–3.65 mmol ACAE/g extract). In silico results showed that rutin and quercetin (-70.4 and -72.2 Kcal/mol, for rutin and quercetin respectively) docked to the enzymatic cavity of acetylcholinesterase but these phenolic compounds showed less affinity with butyrylcholinesterase (-15.0 and -5.2 Kcal/mol, for rutin and quercetin respectively). The extracts did not induce any mutations on the bacterial strains, while they have excellent antimutagenic capacity against well-known mutagens (inhibition values 98%, 97% and 96%). The methanol extract (0.78 mg/ml) showed moderate antifungal activity while the ethyl acetate extract (0.78–3.12 mg/ml) showed weak to moderate antimicrobial activity. This study provides valuable baseline data which might serve for the development of future pharmacophores for the management of human ailments. 相似文献
172.
Conductivity studies of plasticized anhydrous PEO-KOH alkaline solid polymer electrolyte 总被引:1,自引:0,他引:1
Polyethylene oxide (PEO)–potassium hydroxide (KOH)-based alkaline solid polymer electrolyte films have been prepared by using
methanol as solvent. The highest room temperature ionic conductivity of (2.1 ± 0.5) × 10−8 S cm−1 was achieved for the composition of 70 wt% PEO:30 wt% KOH. The addition of plasticizer, ethylene carbonate, propylene carbonate,
or polyethylene glycol to the highest conductivity of PEO–KOH system helps to increase the ambient ionic conductivity to the
order of 10−6–10−4 S cm−1. The log σ vs 1/T plot of PEO–KOH showed a small conductivity decrease at 50–60 °C range. The small decrease and the hysteresis that occur
during the heating–cooling cycle was overcome by the presence of the plasticizer. X-ray diffraction observation supports the
conductivity results. 相似文献
173.
《Chemical physics letters》2003,367(3-4):398-404
Various strategies for correcting structural and energetic artefacts of molecular simulations with truncated potentials based on integral equation theory are described and applied to liquid water. The performance of the methods is examined for a range of cutoff distances and different shifted-force potentials. With the recently enhanced damped Coulomb potential (D. Zahn, B. Schilling, S.M. Kast, J. Phys. Chem. B, 106 (2002) 10725), parameterised and corrected by integral equation theory, radial distribution functions and excess internal energy very close to the Ewald simulation limit are obtained from a simulation with a cutoff distance of only 6 Å. 相似文献
174.
《Chemical physics letters》2003,367(5-6):723-729
We show that the incidental numerical instabilities in explicitly correlated coupled cluster R12 (CC-R12) calculations can be a priori removed by using systematically developed R12 suited basis sets. Those are quite different from basis sets developed for conventional calculations mainly in polarization functions. Using even tempered polarization sets for carbon and oxygen we were able to define compromise R12 suited bases which describe equally well atomic ground states, positive and negative ions and electric field polarized atoms. Corresponding energies obtained with such ‘R12 universal’ sets remain accurate to within a few μEh with respect to the ‘R12 optimal’ bases of individual systems. 相似文献
175.
176.
《Journal of voice》2022,36(4):582.e23-582.e32
177.
178.
179.
180.
《Journal of voice》2021,35(4):664.e11-664.e19