全文获取类型
收费全文 | 186篇 |
免费 | 2篇 |
专业分类
化学 | 154篇 |
晶体学 | 1篇 |
数学 | 13篇 |
物理学 | 20篇 |
出版年
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有188条查询结果,搜索用时 15 毫秒
181.
Pérez-Flores L Ruiz-Chica AJ Delcros JG Sánchez-Jiménez FM Ramírez FJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(4):1089-1096
We studied by electronic spectroscopies the interaction between double-stranded oligonucleotides containing either adenine-thymine or guanine-cytosine alternating sequences and N(1)-(acridin-9-yl)-1,16-diamino-4,8,13-triazahexadecane, which is a conjugated molecule formed by the covalent binding of spermine and 9-aminoacridine moieties via a trimethylene chain. Solutions containing the oligonucleotides and the conjugate, at different molar ratios, were studied by using electronic absorption, fluorescence emission and circular dichroism. Calculated association constants and fluorescence emission spectra showed that spermine conjugation induces sequence selectivity. The orientation of the intercalated acridine rings with respect to the oligonucleotide base planes was deduced from the electronic circular dichroism spectra. Evidence of the formation of spermine-induced aggregated structures, with potential applications to DNA packaging, gene therapy and anti-tumor therapy, was also achieved. Our data demonstrates that this spermine-acridine conjugate adds several specific characteristics provided by the polyamine moiety, as sequence selectivity, to the interesting properties of acridine derivatives. 相似文献
182.
Silva MG Vieira IG Mendes FN Albuquerque IL dos Santos RN Silva FO Morais SM 《Molecules (Basel, Switzerland)》2008,13(10):2482-2487
Ursolic acid is a very important compound due to its biological potential as an anti-inflammatory, trypanocidal, antirheumatic, antiviral, antioxidant and antitumoral agent. This study presents the HPLC analysis of ursolic acid (UA) content in eight different Ocimum species: O. americanum L., O. basilicum L, O. basilicum var purpurascens Benth, O. basilicum var. minimum L, O. gratissimum L, O. micranthum Willd, O. selloi Benth. and O. tenuiflorum L. grown in Northeastern Brazil. In these Ocimum species, UA was detected in different yields, with O. tenuiflorum showing the highest content (2.02%). This yield is very significant when compared with other sources of UA. 相似文献
183.
Fernández-Botello A Comelles F Alsina MA Cea P Reig F 《The journal of physical chemistry. B》2008,112(44):13834-13841
Docetaxel (DCT) is an antineoplastic drug for the treatment of a wide spectrum of cancers. DCT surface properties as well as miscibility studies with l-alpha-dipalmitoyl phosphatidylcholine (DPPC), which constitutes the main component of biological membranes, are comprehensively described in this contribution. Penetration studies have revealed that when DCT is injected under DPPC monolayers compressed to different surface pressures, it penetrates into the lipid monolayer promoting an increase in the surface pressure. DCT is a surface active molecule able to decrease the surface tension of water and to form insoluble films when spread on aqueous subphases. The maximum surface pressure reached after compression of a DCT Langmuir film was 13 mN/m. Miscibility of DPPC and DCT in Langmuir films has been studied by means of thermodynamic properties as well as by Brewster angle microscopy (BAM) analysis of the mixed films at the air-water interface, concluding that DPPC and DCT are miscible and they form non-ideally mixed monolayers at the air-water interface. Helmholtz energies of mixing revealed that no phase separation occurs. In addition, Helmholtz energies of mixing become more negative with decreasing areas per molecule, which suggests that the stability of the mixed monolayers increases as the monolayers become more condensed. Compressibility values together with BAM images indicate that DCT has a fluidizing effect on DPPC monolayers. 相似文献
184.
J Francos F Grande-Carmona H Faustino J Iglesias-Sigüenza E Díez I Alonso R Fernández JM Lassaletta F López JL Mascareñas 《Journal of the American Chemical Society》2012,134(35):14322-14325
The first highly enantioselective intermolecular (4 + 2) cycloaddition between allenes and dienes is reported. The reaction provides good yields of optically active cyclohexenes featuring diverse substitution patterns and up to three stereocenters. Key to the success of the process is the use of newly designed axially chiral N-heterocyclic carbene-gold catalysts. 相似文献
185.
Singh SB Zink DL Huber J Genilloud O Salazar O Diez MT Basilio A Vicente F Byrne KM 《Organic letters》2006,8(24):5449-5452
Inhibition of protein synthesis is one of the validated and highly successful targets for inhibition of bacterial growth; this mechanism is a target of a large number of clinical drugs. Ribosomal protein S4, a primary protein, is a potential target for the discovery of antibacterial agents. We describe, using an antisense-sensitized rpsD Streptomyces aureus strain, the discovery and activity of lucensimycins A and B. [structure: see text]. 相似文献
186.
Beatriz Abad‐García Sergio Garmón‐Lobato Luis A. Berrueta Blanca Gallo Francisca Vicente 《Rapid communications in mass spectrometry : RCM》2009,23(17):2785-2792
A mass spectrometric method using electrospray ionization with triple quadrupole and quadrupole time‐of‐flight hybrid (Q‐Tof) mass spectrometry has been applied to the structural characterization of dihydroflavonols. This family of compounds has been studied by liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the first time in this work. A comprehensive study of the product ion MS spectra of the [M+H]+ ion of a commercially available standard has been performed. The most useful fragmentations in terms of structural identification are those that involve cleavage of the C‐ring, resulting in diagnostic ions of dihydroflavonol family: 1,3A, 1,2B, 1,2B‐CO, 0,2A, 0,2A‐H2O, 0,2A‐CO, and 0,2A‐H2O‐CO, that allow the characterization of the substituents in the A‐ and B‐rings. In addition to those ions, other product ions due to losses of H2O and CO molecules from the Y ion were observed. Their fragmentation mechanisms and ion structures have been proposed. The established fragmentation patterns have been used to successfully identity three dihydroflavonols found in tangerine juices for the first time. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
187.
Jorge Rivas Florentina Pia Matías Araya Nicols Latorre-Padilla Benjamín Pinilla-Rojas Sofía Caroca Francisca C. Bronfman Loretto Contreras-Porcia 《Molecules (Basel, Switzerland)》2022,27(20)
Seaweed aquaculture is affected by natural and anthropogenic stressors, which put the biomass productivity of the cultures at risk. Seaweed biomass for commercial purposes, principally in pharmaceutical and/or nutraceutical applications, needs to be free of pollutants; therefore, controlled cultures have relevance in regulating the quality of biomass. The aim of this work was to demonstrate the successful utilization of controlled outdoor cultures to remove excess heavy metal accumulation in Gracilaria chilensis, an important commercial seaweed farming model. Specifically, we designed a simple and operational heavy metal depuration protocol, utilizing seawater and tap water removal, which permitted the concentration reduction of 10 heavy metals, including As, Cu, and Cd but not Zn, from the biomass at 7 days of culture. The percentage of depuration of the heavy metals ranged from 32 to 92% at 7 days, which was maintained throughout 21 days of culture. During the culture period, the monitored physicochemical parameters (temperature, salinity, and dissolved oxygen, among others) remained stable, with an increase in the daily growth rate (DGR% d−1) of the biomass recorded after 14 days of culture. Consequently, the experimental setup was successful for heavy metal depuration, which highlights the importance of controlled outdoor cultures as important tools of sustainability. 相似文献
188.