全文获取类型
收费全文 | 163篇 |
免费 | 3篇 |
专业分类
化学 | 110篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 6篇 |
物理学 | 43篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 9篇 |
2011年 | 15篇 |
2010年 | 7篇 |
2009年 | 15篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2001年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
排序方式: 共有166条查询结果,搜索用时 15 毫秒
41.
The most challenging task of creating a bioengineered ovary to restore fertility in cancer patients is choosing an appropriate biomaterial to encapsulate isolated preantral follicles and ovarian cells. In this study, as a biocompatible and biodegradable biomaterial containing fibrin-like bioactivity and manageable physical properties, PEGylated fibrin aims to encapsulate isolated ovarian stromal cells as a first step of creating an engineered ovarian tissue. For this purpose, human ovarian stromal cells were isolated from frozen-thawed ovarian tissue and cultured in the PEGylated fibrin hydrogels (PEG:Fib), which were fabricated by combining two different molar ratios of PEG:Fib (10:1 and 5:1) and two thrombin concentrations. The samples were analyzed at days 0 and 5 of in vitro for cell density, proliferation (Ki67), and apoptosis (caspase-3). Moreover, LIVE/DEAD and PrestoBlue assays assessed cell viability and proliferation on days 1, 3, and 5. The effect of PEGylation on the biodegradation behavior of fibrin was evaluated by measuring the remaining mass ratio of non-modified fibrin, PEG:Fib 10:1, and PEG:Fib 5:1 hydrogels after 1, 2, 3, 5, 8, 11, and 15 days. The results showed that PEGylated fibrin hydrogels enhanced scaffold stability and supported cell viability and proliferation. In addition, PEG:Fib 5:1 T50 indicated a significantly higher cell density dynamic and non-significantly lower expression of caspase-3 on day 5. Besides, uniformity of cell distribution inside the hydrogel and a tendency to a high rate of Ki67-positive cells was observed in PEG:Fib 10:1 T50 hydrogels. In conclusion, this study reveals the positive effects of PEGylated fibrin hydrogels on isolated human ovarian stromal cells. Based on such promising findings, we believe that this matrix should be tested to encapsulate isolated human ovarian follicles. 相似文献
42.
Fernando Dures Patrícia M. A. Silva Pedro Novais Isabel Amorim Luís Gales Ctia I. C. Esteves Samuel Guieu Hassan Bousbaa Madalena Pinto Emília Sousa 《Molecules (Basel, Switzerland)》2021,26(11)
Thioxanthones are bioisosteres of the naturally occurring xanthones. They have been described for multiple activities, including antitumor. As such, the synthesis of a library of thioxanthones was pursued, but unexpectedly, four tetracyclic thioxanthenes with a quinazoline–chromene scaffold were obtained. These compounds were studied for their human tumor cell growth inhibition activity, in the cell lines A375-C5, MCF-7 and NCI-H460. Photophysical studies were also performed. Two of the compounds displayed GI50 values below 10 µM for the three tested cell lines, and structure–activity relationship studies were established. Three compounds presented similar wavelengths of absorption and emission, characteristic of dyes with a push-pull character. The structures of two compounds were elucidated by X-ray crystallography. Two tetracyclic thioxanthenes emerged as hit compounds. One of the two compounds accumulated intracellularly as a bright fluorescent dye in the green channel, as analyzed by both fluorescence microscopy and flow cytometry, making it a promising theranostic cancer drug candidate. 相似文献
43.
The small organic molecule electro-oxidation (OMEO) and the hydrogen evolution (HER) are two important half-reactions in direct liquid fuel cells (DLFCs) and wa... 相似文献
44.
Clarissa M. de Amorim Daisy J. A. Netz Angelica G. Couto Rilton A. de Freitas Tania M. B. Bresolin 《Chromatographia》2009,70(9-10):1411-1415
A forced degradation study of idebenone was conducted under conditions of UV irradiation, acid, basic and oxidative hydrolysis and in order to develop an isocratic stability-indicating LC-UV method for drug quantification in chitosan and N-carboxymethylchitosan nanoparticles obtained by spray drying. The drug was more labile to alkaline treatment than under the other forced degradation conditions. Idebenone and its degradation products were optimally resolved (resolution >4) on a Luna Phenomenex C18 column with mobile phase composed by methanol:water: (80:20% v/v) at a flow rate of 1.0 mL min?1, at 30 °C, using wavelength of 279 nm for drug detection. The method was linear, over a drug concentration range of 2 to 10 μg mL?1. The RSD% value of intra- and inter-day precision studies was <1.5. The method showed excellent recoveries (99.4 to 101.1%). The LOD and LOQ values were found to be 0.18 and 0.59 μg mL?1, respectively. In conclusion this method can be used as a rapid and accurate assay of idebenone in the nanoparticles during stability tests. 相似文献
45.
Paulo J. Amorim Madeira Nuno M. Xavier Amélia P. Rauter M. Helena Florêncio 《Journal of mass spectrometry : JMS》2010,45(10):1167-1178
Sugars that incorporate the unsaturated carbonyl motif have become important synthetic targets not only as a result of their potential biological properties but also as precursors in the synthesis of many bioactive products. Moreover, little is known about the influence of the γ‐lactone moiety in the fragmentation pattern of furanose rings. Therefore, two α,β‐unsaturated γ‐lactones (butenolides) and two β‐hydroxy γ‐lactones, C? C linked to a furanose ring were studied using electrospray ionization FTICR mass spectrometry. The behaviour of the protonated and sodiated forms of the compounds under study has been compared considering their structural features. Fragmentation mechanisms were established and ion structures were proposed taking into account the MS2 and MS3 experiments, accurate mass measurements and semi‐empirical calculations. These inexpensive methods proved to be a valuable resource for proposing protonation sites and for the establishment of fragmentation pathways. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
46.
M.T.Sousa Pessoa De Amorim C. Comel P. Vermande 《Journal of Analytical and Applied Pyrolysis》1982,4(1):73-81
Pyrolysis of two polypropylene samples (degrees of isotacticity 0.50 and 0.85) has been carried out by flash pyrolysis and distillation pyrolysis. The analytical coupling of flash pyrolysis, gas chromatography and mass spectrometry allowed the analysis of the degradation products and their evolution with temperature between 500 and 900°C to be followed under different experimental conditions.The mechanism of polypropylene degradation is compared with the radical mechanism of polystyrene degradation.The depolymerization reaction leading to the production of monomer (25%) is not the most important degradation reaction. The transfer reactions predominate and generate the following products: 2,4-dimethyl-1-heptene (27–32%), pentane (ca. 8%), 2,4,6,8-tetramethyl-1-hendecene (7–18%) and 2,4,6-trimethyl-1-nonene (4–10%). 相似文献
47.
The density-functional approach to Molecular Orbital theory shows that the chemical bonding potential is better described by orbital electronegativities than by ionization energies. This results from the fact that the electronic relaxation connected with ionization is not significant for the homolytic breaking of chemical bonds. Electronegativity, on the other hand, is an eigenvalue corresponding to the average potential seen by an electron as a molecular orbital changes into monocentric (atomic) orbitals. 相似文献
48.
49.
Gastric cancer (GC) is one of the major causes of death worldwide, ranking as the fifth most incident cancer in 2020 and the fourth leading cause of cancer mortality. The majority of GC patients are in an advanced stage at the time of diagnosis, presenting a poor prognosis and outcome. Current GC treatment approaches involve endoscopic detection, gastrectomy and chemotherapy or chemoradiotherapy in an adjuvant or neoadjuvant setting. Drug development approaches demand extreme effort to identify molecular mechanisms of action of new drug candidates. Drug repurposing is based on the research of new therapeutic indications of drugs approved for other pathologies. In this review, we explore GC and the different drugs repurposed for this disease. 相似文献
50.
J. A. Souza-Corrêa C. Oliveira L. D. Wolf V. M. Nascimento G. J. M. Rocha J. Amorim 《Applied biochemistry and biotechnology》2013,171(1):104-116
Sugarcane bagasse samples were pretreated with ozone via atmospheric O2 pressure plasma. A delignification efficiency of approximately 80 % was observed within 6 h of treatment. Some hemicelluloses were removed, and the cellulose was not affected by ozonolysis. The quantity of moisture in the bagasse had a large influence on delignification and saccharification after ozonation pretreatment of the bagasse, where 50 % moisture content was found to be best for delignification (65 % of the cellulose was converted into glucose). Optical absorption spectroscopy was applied to determine ozone concentrations in real time. The ozone consumption as a function of the delignification process revealed two main reaction phases, as the ozone molecules cleave the strong carbon–carbon bonds of aromatic rings more slowly than the weak carbon–carbon bonds of aliphatic chains. 相似文献