全文获取类型
收费全文 | 199篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 189篇 |
晶体学 | 7篇 |
数学 | 4篇 |
物理学 | 9篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2021年 | 23篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 3篇 |
2013年 | 13篇 |
2012年 | 13篇 |
2011年 | 19篇 |
2010年 | 6篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 11篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
排序方式: 共有209条查询结果,搜索用时 15 毫秒
1.
2.
Kinga Suwińska Giovanni Dario Andreetti 《Journal of inclusion phenomena and macrocyclic chemistry》1983,1(1):71-78
C28H36O10. KSCN is monoclinic, space groupP21 withZ=2,a=10.390(3),b=8.959(7),c=16.377(7) Å, =92.49(5)°. FinalR=0.053 for 1437 reflections measured at room temperature. The K– ion lies on the least-squares plane formed by the six oxygen atoms in the macrocyclic ring. The SCN– ion was found on the same face of the macrocycle as the chiral glucopyranoside moiety.Methyl-4,6-O-benzylidene-2,3-O-(1,2-bis(ethoxyethoxy)benzenediyl)--d-glucopyranoside. 相似文献
3.
4.
Lipophilicity study of eight cephalosporins by reversed‐phase thin‐layer chromatographic method 下载免费PDF全文
Monika Dąbrowska Łukasz Komsta Jan Krzek Kinga Kokoszka 《Biomedical chromatography : BMC》2015,29(11):1759-1768
The lipophilicity (RM0) and specific hydrophobic surface area for the representatives of four generation cephalosporins have been determined by reversed‐phase thin‐layer chromatography, and the effect of different mobile‐phase modifiers (such as methanol, acetonitrile, acetone, 1,4‐dioxane and 2‐propanol) on the retention has been studied. The compounds studied showed typical retention behavior; their RM values decreased linearly with increasing concentration of the organic modifier in the eluent. The linear correlations between the volume fraction of the organic solvent and the RM values over a limited range were established for each solute, resulting in high values of correlation coefficients (>0.95 in most cases). RM values were determined by various concentrations of organic modifier, and the correlation obtained was extrapolated to 0% of organic modifier. Chromatographically established logP (RM0) parameters were compared with computationally calculated partition coefficients values (AClogP, ALOGP, KOWWIN, ALOGPs, XLOGP2, MLOGP and XLOGP3) and experimental octanol–water logP values (measured by the shake flask method). The received results demonstrate that RP‐TLC may be a good alternative technique for analytics in describing the lipophilic nature of investigated cephalosporins as well as the activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
5.
Agnieszka Lewiska Marta Doma-Kdzia Kinga Kierul Micha Bochynek Dominika Pannert Piotr Nowaczyk Marcin ukaszewicz 《Molecules (Basel, Switzerland)》2021,26(4)
The skin is constantly exposed to external and internal factors that disturb its function. In this work, two nanosystems-levan nanoparticles and a surfactin-stabilized nanoemulsion were preserved (tested for microbial growth) and characterized (size, polydispersity, Zeta potential, and stability). The nanosystems were introduced in the model formulations-cream, tonic, and gel, and confirmed by TEM. The analysis showed that nanoemulsion has a spherical morphology and size 220–300 nm, while levan nanoparticles had irregular shapes independently of the use of matrix and with particle size (130–260 nm). Additionally, we examined the antiradical effect of levan nanoparticles and nanoemulsion in the prototype of formulations by scavenging DPPH (2,2-diphenyl-1-picrylhydrazyl; EPR spectroscopy). The model cream with both nanosystems and the whole range of products with nanosystems were evaluated in vivo for hydration, elasticity, smoothness, wrinkles and vascular lesions, discoloration, respectively. The cream improved skin condition in all tested parameters in at least 50% of volunteers. The use of more comprehensive care, additionally consisting of a tonic and gel, reduced the previously existing skin discoloration to 10.42 ± 0.58%. The presented prototype formulations are promising in improving skin conditions. 相似文献
6.
Dobosz B Drzewiecka K Waskiewicz A Irzykowska L Bocianowski J Karolewski Z Kostecki M Kruczynski Z Krzyminiewski R Weber Z Golinski P 《Applied magnetic resonance》2011,41(1):19-30
Electron paramagnetic resonance was used to monitor free radicals and paramagnetic species like Fe, Mn, Cu generation, stability and status in Asparagus officinalis infected by common pathogens Fusarium proliferatum and F. oxysporum. Occurrence of F. proliferatum and F. oxysporum, level of free radicals and other paramagnetic species, as well as salicylic acid and mycotoxins content in roots and stems of seedlings were estimated on the second and fourth week after inoculation. In the first term free and total salicylic acid contents were related to free radicals level in stem (P?=?0.010 and P?=?0.033, respectively). Concentration of Fe(3+) ions in porphyrin complexes (g?=?2.3, g?=?2.9) was related to the species of pathogen. There was no significant difference between Mn(2+) concentrations in stem samples; however, the level of free radicals in samples inoculated with F. proliferatum was significantly higher when compared to F. oxysporum. 相似文献
7.
Cem B. Yildiz Kinga I. Leszczyska Sandra Gonzlez‐Gallardo Michael Zimmer Akin Azizoglu Till Biskup Christopher W. M. Kay Volker Huch Henry S. Rzepa David Scheschkewitz 《Angewandte Chemie (International ed. in English)》2020,59(35):15087-15092
Main group analogues of cyclobutane‐1,3‐diyls are fascinating due to their unique reactivity and electronic properties. So far only heteronuclear examples have been isolated. Here we report the isolation and characterization of all‐silicon 1,3‐cyclobutanediyls as stable closed‐shell singlet species from the reversible reactions of cyclotrisilene c‐Si3Tip4 (Tip=2,4,6‐triisopropylphenyl) with the N‐heterocyclic silylenes c‐[(CR2CH2)(NtBu)2]Si: (R=H or methyl) with saturated backbones. At elevated temperatures, tetrasilacyclobutenes are obtained from these equilibrium mixtures. The corresponding reaction with the unsaturated N‐heterocyclic silylene c‐(CH)2(NtBu)2Si: proceeds directly to the corresponding tetrasilacyclobutene without detection of the assumed 1,3‐cyclobutanediyl intermediate. 相似文献
8.
9.
The antitumor drug, oxaliplatin, induces neuropathic pain, which is resistant to available analgesics, and novel mechanism-based therapies are being evaluated for this debilitating condition. Since activated microglia, impaired serotonergic and noradrenergic neurotransmission and overexpressed sodium channels are implicated in oxaliplatin-induced pain, this in vivo study assessed the effect of minocycline, a microglial activation inhibitor used alone or in combination with ambroxol, a sodium channel blocker, or duloxetine, a serotonin and noradrenaline reuptake inhibitor, on oxaliplatin-induced tactile allodynia and cold hyperalgesia. To induce neuropathic pain, a single dose (10 mg/kg) of intraperitoneal oxaliplatin was used. The mechanical and cold pain thresholds were assessed using mouse von Frey and cold plate tests, respectively. On the day of oxaliplatin administration, only duloxetine (30 mg/kg) and minocycline (100 mg/kg) used alone attenuated both tactile allodynia and cold hyperalgesia 1 h and 6 h after administration. Minocycline (50 mg/kg), duloxetine (10 mg/kg) and combined minocycline + duloxetine influenced only tactile allodynia. Seven days after oxaliplatin, tactile allodynia (but not cold hyperalgesia) was attenuated by minocycline (100 mg/kg), duloxetine (30 mg/kg) and combined minocycline and duloxetine. These results indicate a potential usefulness of minocycline used alone or combination with duloxetine in the treatment of oxaliplatin-induced pain. 相似文献
10.
Bartosz Mozgawa Dr. Filip Zasada Dr. Monika Fedyna Prof. Kinga Góra-Marek Dr. Edyta Tabor Dr. Kinga Mlekodaj Dr. Jiří Dědeček Prof. Zhen Zhao Dr. Piotr Pietrzyk Prof. Zbigniew Sojka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17159-17180
NH3 temperature-programmed desorption (NH3-TPD) is frequently used for probing the nature of the active sites in CuSSZ-13 zeolite for selective catalytic reduction (SCR) of NOx. Herein, we propose an interpretation of NH3-TPD results, which takes into account the temperature-induced dynamics of NH3 interaction with the active centers. It is based on a comprehensive DFT/GGA+D and first-principles thermodynamic (FPT) modeling of NH3 adsorption on single Cu2+, Cu+, [CuOH]+ centers, dimeric [Cu-O-Cu]2+, [Cu-O22−-Cu]2 species, segregated CuO nanocrystals and Brønsted acid sites (BAS). Theoretical TPD profiles are compared with the experimental data measured for samples of various Si/Al ratios and distribution of Al within the zeolite framework. Copper reduction, its relocation, followed by the intrazeolite olation/oxolation processes, which are concomitant with NH3 desorption, were revealed by electron paramagnetic resonance (EPR) and IR. DFT/FPT results show that the peaks in the desorption profiles cannot be assigned univocally to the particular Cu and BAS centers, since the observed low-, medium- and high-temperature desorption bands have contributions coming from several species, which dynamically change their speciation and redox states during NH3-TPD experiment. Thus, a rigorous interpretation of the NH3-TPD profiles of CuSSZ-13 in terms of the strength and concentration of the active centers of a particular type is problematic. Nonetheless, useful connections for molecular interpretation of TPD profiles can be established between the individual component peaks and the corresponding ensembles of the adsorption centers. 相似文献