全文获取类型
收费全文 | 533篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
化学 | 326篇 |
晶体学 | 4篇 |
力学 | 48篇 |
数学 | 110篇 |
物理学 | 70篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 19篇 |
2013年 | 34篇 |
2012年 | 26篇 |
2011年 | 40篇 |
2010年 | 29篇 |
2009年 | 30篇 |
2008年 | 28篇 |
2007年 | 41篇 |
2006年 | 31篇 |
2005年 | 32篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1941年 | 1篇 |
1937年 | 1篇 |
1926年 | 1篇 |
1913年 | 1篇 |
1907年 | 1篇 |
1869年 | 1篇 |
排序方式: 共有558条查询结果,搜索用时 584 毫秒
441.
Mirko Salinitro Alessandro Zappi Sonia Casolari Marcello Locatelli Annalisa Tassoni Dora Melucci 《Molecules (Basel, Switzerland)》2022,27(6)
Bioindicator plants are species that have the capacity to linearly uptake some elements (metal and metalloids) from the growing substrate, thus reflecting their concentration in the soil. Many factors can influence the uptake of these elements by plants, among which is the simultaneous presence of several metals, a common situation in contaminated or natural soils. A novel approach that can be used to validate the bioindication ability of a species growing on a polymetallic substrate is the design of experiment (DoE) approach. The aim of the present study was to apply the DoE in full factorial mode to model the Cu, Cd, Pb, Zn, and Cr bioindication capacity of Polygonum aviculare, used as the model plant. The results showed that P. aviculare has the ability to bioindicate Cd and Cr with a linear uptake (from 0.35 to 6.66, and 0.1 to 3.4 mg kg−1, respectively) unaffected by the presence of other metals. Conversely, the uptake of Pb, Cu, and Zn is strongly influenced by the presence of all the studied metals, making their concentration in the plant shoot not proportional to that of the soil. In conclusion, these preliminary results confirmed that the DoE can be used to predict the bioindicator abilities of a plant for several elements at the same time and to evaluate the interactions that can be established between variables in the growing medium and in the plant itself. However, more studies including other plant species are needed to confirm the effectiveness of this method. 相似文献
442.
Daniel Josiane S. P. Cruz Jonas C. Catelani Tiago A. Garcia Jerusa S. Trevisan Marcello G. 《Journal of Thermal Analysis and Calorimetry》2021,143(4):3127-3135
Journal of Thermal Analysis and Calorimetry - This study aims to characterize erythromycin (ERY) estolate by thermogravimetry analysis and differential scanning calorimetry. For such a purpose,... 相似文献
443.
444.
Katarzyna Jakimiuk Jakub W. Strawa Sebastian Granica Marcello Locatelli Angela Tartaglia Micha Tomczyk 《Molecules (Basel, Switzerland)》2022,27(6)
A new 5,7-dihydroxy-3′-methoxy-4′-acetoxyflavone-8-C-β-d-arabinopyranoside-2″-O-(4‴-acetoxy)-glucoside (6) and three known flavone C-glycosides—5,7,3′,4′-tetrahydroxyflavone-6-C-xyloside-8-C-β-d-glucoside (lucenin-1) (7), 5,7,3′-trihydroxyflavone-6-C-glucoside-8-C-β-d-glucoside (vicenin-2) (8), and 5,7,4′-trihydroxy-3′-methoxyflavone-6-C-β-d-glucopyranoside-8-C-α-arabinopyranoside (chrysoeriol-6-C-β-d-glucopyranoside-8-C-α-arabinopyranoside) (9)—were isolated from aerial parts of Scleranthus perennis L. (Caryophyllaceae). Their structures were determined through the use of comprehensive spectroscopic and spectrometric methods, and a method for the quantification of the major constituents of S. perennis and S. annuus L. was developed. Furthermore, the anti-collagenase and antioxidant activities of all isolated compounds obtained from extracts and fractions from both Scleranthus species were evaluated. The highest percentage of collagenase inhibition (at 400 µg/mL) was distinguished for methanolic extracts (22.06%, 32.04%) and ethyl acetate fractions (16.59%, 14.40%) from S. annuus and S. perennis. Compounds 6–9 displayed moderate inhibitory activity, with IC50 values ranging from 39.59–73.86 µM. 相似文献
445.
Margherita Mastromarino Mauro Niso Carmen Abate Ewgenij Proschak Mariam Dubiel Holger Stark Marin Castro Enza Lacivita Marcello Leopoldo 《Molecules (Basel, Switzerland)》2022,27(4)
Long-chain arylpiperazine scaffold is a versatile template to design central nervous system (CNS) drugs that target serotonin and dopamine receptors. Here we describe the synthesis and biological evaluation of ten new arylpiperazine derivatives designed to obtain an affinity profile at serotonin 5-HT1A, 5-HT2A, 5-HT7 receptor, and dopamine D2 receptor of prospective drugs to treat the core symptoms of autism spectrum disorder (ASD) or psychosis. Besides the structural features required for affinity at the target receptors, the new compounds incorporated structural fragments with antioxidant properties to counteract oxidative stress connected with ASD and psychosis. All the new compounds showed CNS MultiParameter Optimization score predictive of desirable ADMET properties and cross the blood–brain barrier. We identified compound 12a that combines an affinity profile compatible with antipsychotic activity (5-HT1A Ki = 41.5 nM, 5-HT2A Ki = 315 nM, 5-HT7 Ki = 42.5 nM, D2 Ki = 300 nM), and compound 9b that has an affinity profile consistent with studies in the context of ASD (5-HT1A Ki = 23.9 nM, 5-HT2A Ki = 39.4 nM, 5-HT7 Ki = 45.0 nM). Both compounds also had antioxidant properties. All compounds showed low in vitro metabolic stability, the only exception being compound 9b, which might be suitable for studies in vivo. 相似文献
446.
447.
Francesco Epifano Serena Fiorito Marcello Locatelli Vito Alessandro Taddeo Salvatore Genovese 《Natural product research》2015,29(2):180-184
As a continuation of our ongoing studies aimed to reveal the presence of oxyprenylated anthraquinones in plants claimed to have a laxative effect, in this article, we describe the extraction and HPLC separation of madagascin (3-isopentenyloxyemodin) and 3-geranyloxyemodine from dried leaves and fruits of Senna alexandrina Mill. (Leguminosae) and leaves and gel of Aloe vera (L.) Burm. F. (Xanthorrhoeaceae). Both compounds are described herein for the first time as components of extracts of the title plants. 相似文献
448.
449.
450.
NAD(P)H‐Independent Asymmetric CC Bond Reduction Catalyzed by Ene Reductases by Using Artificial Co‐substrates as the Hydrogen Donor
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Christoph K. Winkler Dorina Clay Marcello Entner Markus Plank Prof. Dr. Kurt Faber 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(5):1403-1409
To develop a nicotinamide‐independent single flavoenzyme system for the asymmetric bioreduction of C?C bonds, four types of hydrogen donor, encompassing more than 50 candidates, were investigated. Six highly potent, cheap, and commercially available co‐substrates were identified that (under the optimized conditions) resulted in conversions and enantioselectivities comparable with, or even superior to, those obtained with traditional two‐enzyme nicotinamide adenine dinucleotide phosphate (NAD(P)H)‐recycling systems. 相似文献