全文获取类型
收费全文 | 133篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 59篇 |
力学 | 1篇 |
数学 | 23篇 |
物理学 | 53篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 6篇 |
2009年 | 9篇 |
2008年 | 14篇 |
2007年 | 12篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1990年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 15 毫秒
91.
Down Syndrome (DS) is considered the most frequent form of Intellectual Disability, with important expressions of cognitive decline and early dementia. Studies on potential treatments for dementia in this population are still scarce. Thus, the current review aims to synthesize the different pharmacological approaches that already exist in the literature, which focus on improving the set of symptoms related to dementia in people with DS. A total of six studies were included, evaluating the application of supplemental antioxidant therapies, such as alpha-tocopherol; the use of acetylcholinesterase inhibitor drugs, such as donepezil; N-methyl-d-aspartate (NMDA) receptor antagonists, such as memantine; and the use of vitamin E and a fast-acting intranasal insulin. Two studies observed important positive changes related to some general functions in people with DS (referring to donepezil). In the majority of studies, the use of pharmacological therapies did not lead to improvement in the set of symptoms related to dementia, such as memory and general functionality, in the population with DS. 相似文献
92.
Marília Cavalcanti Coriolano Cynarha Daysy Cardoso da Silva Cristiane Moutinho Lagos de Melo Ranilson de Souza Bezerra Athiê Jorge Guerra Santos Valéria Rêgo Alves Pereira Luana Cassandra Breitenbach Barroso Coelho 《Applied biochemistry and biotechnology》2012,168(5):1335-1348
This work reports the isolation of a serum lectin from cobia fish (Rachycentron canadum) named RcaL. Immunomodulatory activity on mice splenocyte experimental cultures through cytotoxic assays and cytokine production were also performed. RcaL was obtained through precipitation with ammonium sulphate and affinity chromatography on a Concanavalin A-Sepharose 4B column. The ammonium sulphate fraction F3 showed the highest specific hemagglutinating activity and was applied to affinity chromatography. The lectin was eluted with methyl-α-d-mannopyranoside. RcaL showed highest affinity for methyl-α-d-mannopyranoside and d-mannose; eluted fractions of RcaL agglutinated rabbit erythrocytes (titre, 128?1) retained 66 % of chromatographed lectin activity, and the obtained purification factor was 1.14. Under reducing conditions, a polypeptide band of 19.2 kDa was revealed in sodium dodecyl sulphate polyacrylamide gel electrophoresis (PAGE). PAGE confirmed RcaL as an acidic protein revealed in a single band. Cytotoxic and immunomodulatory assays with RcaL in mice splenocyte cultures showed that the lectin was not cytotoxic and induced higher interferon gamma and nitric oxide production in splenocyte cultures. Purified RcaL induced preferential Th1 response, suggesting that it acts as an immunomodulatory compound. 相似文献
93.
Lira RB Cavalcanti MB Seabra MA Silva DC Amaral AJ Santos BS Fontes A 《Micron (Oxford, England : 1993)》2012,43(5):621-626
In order to study biological events, researchers commonly use methods based on fluorescence. These techniques generally use fluorescent probes, commonly small organic molecules or fluorescent proteins. However, these probes still present some drawbacks, limiting the detection. Semiconductor nanocrystals - Quantum Dots (QDs) - have emerged as an alternative tool to conventional fluorescent dyes in biological detection due to its topping properties - wide absorption cross section, brightness and high photostability. Some questions have emerged about the use of QDs for biological applications. Here, we use optical tools to study non-specific interactions between aqueous synthesized QDs and peripheral blood mononuclear cells. By fluorescence microscopy we observed that bare QDs can label cell membrane in live cells and also label intracellular compartments in artificially permeabilized cells, indicating that non-specific labeling of sub-structures inside the cells must be considered when investigating an internal target by specific conjugation. Since fluorescence microscopy and flow cytometry are complementary techniques (fluorescence microscopy provides a morphological image of a few samples and flow cytometry is a powerful technique to quantify biological events in a large number of cells), in this work we also used flow cytometry to investigate non-specific labeling. Moreover, by using optical tweezers, we observed that, after QDs incubation, zeta potentials in live cells changed to a less negative value, which may indicate that oxidative adverse effects were caused by QDs to the cells. 相似文献
94.
On existence, uniform decay rates and blow up for solutions of the 2-D wave equation with exponential source 总被引:1,自引:0,他引:1
Claudianor O. Alves Marcelo M. Cavalcanti 《Calculus of Variations and Partial Differential Equations》2009,34(3):377-411
This paper is concerned with the study of the nonlinear damped wave equation
where Ω is a bounded domain of having a smooth boundary ∂Ω = Γ. Assuming that g is a function which admits an exponential growth at the infinity and, in addition, that h is a monotonic continuous increasing function with polynomial growth at the infinity, we prove both: global existence as
well as blow up of solutions in finite time, by taking the initial data inside the potential well. Moreover, optimal and uniform
decay rates of the energy are proved for global solutions.
The author is Supported by CNPq 300959/2005-2, CNPq/Universal 472281/2006-2 and CNPq/Casadinho 620025/2006-9.
Research of Marcelo M. Cavalcanti partially supported by the CNPq Grant 300631/2003-0. 相似文献
95.
96.
97.
We present a device-independent protocol to test if a given black-box measurement device is entangled, that is, has entangled eigenstates. Our scheme involves three parties and is inspired by entanglement swapping; the test uses the Clauser-Horne-Shimony-Holt Bell inequality, checked between each pair of parties. In the case where all particles are qubits, we characterize quantitatively the deviation of the measurement device from a perfect Bell-state measurement. 相似文献
98.
Erisandro S. Silva Marta M. Conceição Eduardo H. S. Cavalcanti Valter J. Fernandes Jr. Ana C. D. Medeiros Antonio G. Souza 《Journal of Thermal Analysis and Calorimetry》2013,113(2):437-442
The oxidation of oils and biodiesels occurs due to several factors: the quantity of double bonds and the presence of allylic and bis-allylic hydrogens. Esters (biodiesel) that have large amounts of unsaturated fatty acids are more susceptible to oxidation than saturated. The aim of this work was to analyze the thermal and oxidative stability of ethyl biodiesel from Jatropha curcas L. and beef tallow by thermogravimetric, pressure differential scanning calorimetry, and PetroOxy methods. The samples of biodiesel from beef tallow present higher oxidation stability compared to biodiesel from J. curcas. In relation to calorimetric curves of biodiesel from J. curcas and beef tallow stored by 60 days without and with antioxidant, there was verified displacement of peak temperature of the transition to higher temperatures, respectively. Just a sample of biodiesel from beef tallow stored for 60 days with 3,000 ppm of antioxidant t-butyl-hydroxyquinone was within the standard established by Brazilian National Agency of Petroleum, Natural Gas, and Biofuels (ANP). The biodiesel from beef tallow was more stable in terms of thermal and oxidative stability than biodiesel from J. curcas. The thermal and oxidative stability of biodiesel depends on its chemical structure; this corroborates the fact that the oils with a predominance of saturated fatty acids are more stable than the unsaturated. 相似文献
99.
Marcelo M. Cavalcanti Valéria N. Domingos Cavalcanti Irena Lasiecka 《Journal of Differential Equations》2007,236(2):407-459
We establish, subject to some natural additional assumptions imposed on the relation between the source and the damping, both well-posedness and effective optimal decay rates for the solutions of a semilinear model of the wave equation. The theory presented allows to consider both superlinear and sublinear behaviours of the dissipation in the presence of unstructured sources. 相似文献
100.
In this work we derive a master equation to describe the interaction of emitters with structured reservoirs. The equation is applicable when the ‘freezing’ of atomic population decay and the existence of an atom-photon bound state are possible. Furthermore, the equation may be used for arbitrarily strong excitations of the reservoir. We show that for a wide range of reservoir spectral densities, this master equation can be reduced to the Markovian form. Applications to spontaneous emission and resonance fluorescence near the band edge are considered. We demonstrate that the stationary state is strongly dependent on the initial state of the decaying atom-field system. For resonance fluorescence, we confirm the prediction of positive stationary atomic inversion. 相似文献