全文获取类型
收费全文 | 1028篇 |
免费 | 63篇 |
专业分类
1091篇 |
出版年
2023年 | 3篇 |
2022年 | 12篇 |
2021年 | 21篇 |
2020年 | 13篇 |
2019年 | 19篇 |
2018年 | 27篇 |
2017年 | 22篇 |
2016年 | 42篇 |
2015年 | 55篇 |
2014年 | 52篇 |
2013年 | 84篇 |
2012年 | 99篇 |
2011年 | 85篇 |
2010年 | 58篇 |
2009年 | 64篇 |
2008年 | 56篇 |
2007年 | 51篇 |
2006年 | 46篇 |
2005年 | 50篇 |
2004年 | 48篇 |
2003年 | 32篇 |
2002年 | 41篇 |
2001年 | 15篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1091条查询结果,搜索用时 0 毫秒
941.
Guadalupe Delgado-Sánchez Lourdes García-García Martín Castellanos-Joya Pablo Cruz-Hervert Leticia Ferreyra-Reyes Elizabeth Ferreira-Guerrero Andrés Hernández Victor Manuel Ortega-Baeza Rogelio Montero-Campos José Antonio Sulca Ma. de Lourdes Martínez-Olivares Norma Mongua-Rodríguez Renata Baez-Salda?a Jesús Felipe González-Roldán Hugo López-Gatell Alfredo Ponce-de-León José Sifuentes-Osornio María Eugenia Jiménez-Corona 《PloS one》2015,10(6)
Background
Tuberculosis (TB) remains a public health problem in Mexico while the incidence of diabetes mellitus type 2 (DM) has increased rapidly in recent years.Objective
To describe the trends of incidence rates of pulmonary TB associated with DM and not associated with DM and to compare the results of treatment outcomes in patients with and without DM.Materials and Methods
We analysed the National Tuberculosis Registry from 2000 to 2012 including patients with pulmonary TB among individuals older than 20 years of age. The association between DM and treatment failure was analysed using logistic regression, accounting for clustering due to regional distribution.Results
In Mexico from 2000 to 2012, the incidence rates of pulmonary TB associated to DM increased by 82.64%, (p <0.001) in contrast to rates of pulmonary TB rate without DM, which decreased by 26.77%, (p <0.001). Patients with a prior diagnosis of DM had a greater likelihood of failing treatment (adjusted odds ratio, 1.34 (1.11–1.61) p <0.002) compared with patients who did not have DM. There was statistical evidence of interaction between DM and sex. The odds of treatment failure were increased in both sexes.Conclusion
Our data suggest that the growing DM epidemic has an impact on the rates of pulmonary TB. In addition, patients who suffer from both diseases have a greater probability of treatment failure. 相似文献942.
Angel A. Islas Alfredo Sánchez-Solano Thomas Scior Lourdes Millan-PerezPe?a Eduardo M. Salinas-Stefanon 《PloS one》2013,8(12)
Voltage-gated sodium channels (VGSCs) are heteromeric protein complexes that initiate action potentials in excitable cells. The voltage-gated sodium channel accessory subunit, Navβ1, allosterically modulates the α subunit pore structure upon binding. To date, the molecular determinants of the interface remain unknown. We made use of sequence, knowledge and structure-based methods to identify residues critical to the association of the α and β1 Nav1.4 subunits. The Navβ1 point mutant C43A disrupted the modulation of voltage dependence of activation and inactivation and delayed the peak current decay, the recovery from inactivation, and induced a use-dependent decay upon depolarisation at 1 Hz. The Navβ1 mutant R89A selectively delayed channel inactivation and recovery from inactivation and had no effect on voltage dependence or repetitive depolarisations. Navβ1 mutants Y32A and G33M selectively modified the half voltage of inactivation without altering the kinetics. Despite low sequence identity, highly conserved structural elements were identified. Our models were consistent with published data and may help relate pathologies associated with VGSCs to the Navβ1 subunit. 相似文献
943.
Anthropogenic impacts on North American grasslands, a highly endangered ecosystem, have led to declines of prairie dogs, a keystone species, over 98% of their historical range. While impacts of this loss on maintenance of grassland biodiversity have been widely documented, much less is known about the consequences on the supply of ecosystem services. Here we assessed the effect of prairie dogs in the supply of five ecosystem services by comparing grasslands currently occupied by prairie dogs, grasslands devoid of prairie dogs, and areas that used to be occupied by prairie dogs that are currently dominated by mesquite scrub. Groundwater recharge, regulation of soil erosion, regulation of soil productive potential, soil carbon storage and forage availability were consistently quantitatively or qualitatively higher in prairie dog grasslands relative to grasslands or mesquite scrub. Our findings indicate a severe loss of ecosystem services associated to the absence of prairie dogs. These findings suggest that contrary to a much publicize perception, especially in the US, prairie dogs are fundamental in maintaining grasslands and their decline have strong negative impacts in human well – being through the loss of ecosystem services. 相似文献
944.
In plants, various chitinases have been identified and categorized into several groups based on the analysis of their sequences and domains. We have isolated SafchiA, a novel class of chitinase from saffron (Crocus sativus L.). The cDNA encoding SafchiA is mainly expressed in roots and corms, and its expression is induced by elicitor treatment, methyl jasmonate, wounding, and by the fungi Fusarium oxysporum, Beauveria and Phoma sp., suggesting a defence role of the protein. Furthermore, in vitro assays with the recombinant native protein showed chitinolytic, and antifungal activity. The deduced protein shares high similarity with chitinases belonging to family 19 of glycosyl-hydrolases, although some changes in the enzyme active site are present. To explore the properties of SafchiA we have expressed recombinant SafchiA in Escherichia coli and generated four different mutants affected in residues involved in the catalytic activity. One glutamic acid essential for family 19 chitinases activity is not present in C. sativus chitinase suggesting that only one acidic residue is necessary for the enzyme activity, in a similar manner as family 18 glycosyl-hydrolases. 相似文献
945.
Cruz-Garcia L Sánchez-Gurmaches J Bouraoui L Saera-Vila A Pérez-Sánchez J Gutiérrez J Navarro I 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,158(4):391-399
The effects of fish oil (FO) substitution by 66% vegetable oils in a diet with already 75% vegetable protein (66VO) on adipose tissue lipid metabolism of gilthead sea bream were analysed after a 14-month feeding trial. In the last 3 months of the experiment, a FO diet was administrated to a 66VO group (group 66VO/FO) as a finishing diet. Hormone-sensitive lipase (HSL) activity was measured in adipose tissue and adipocyte size, and HSL, lipoprotein lipase and liver X receptor gene expression in isolated adipocytes, on which lipolysis and glucose uptake experiments were also performed. Lipolysis was measured after incubation with tumour necrosis factor-α (TNFα), linoleic acid, and two conjugated linoleic acid isomers. Glucose uptake was analysed after TNFα or insulin administration. Our results show that FO replacement increased lipolytic activity and adipocyte cell size. The higher proportion of large cells observed in the 66VO group could be involved in their observed lower response to fatty acid treatments and lower insulin sensitivity. The 66VO/FO group showed a moderate return to the FO conditions. Therefore, FO replacement can affect the morphology and metabolism of gilthead sea bream adipocytes which could potentially affect other organs such as the liver. 相似文献
946.
Lourdes Guerrero-Ontiveros Maria Wallimann Theo 《Molecular and cellular biochemistry》1998,184(1-2):427-437
Interest in creatine (Cr) as a nutritional supplement and ergogenic aid for athletes has surged over recent years. After cellular uptake, Cr is phosphorylated to phosphocreatine (PCr) by the creatine kinase (CK) reaction using ATP. At subcellular sites with high energy requirements, e.g. at the myofibrillar apparatus during muscle contraction, CK catalyzes the transphosphorylation of PCr to ADP to regenerate ATP, thus preventing a depletion of ATP levels. PCr is thus available as an immediate energy source, serving not only as an energy buffer but also as an energy transport vehicle. Ingestion of creatine increases intramuscular Cr, as well as PCr concentrations, and leads to exercise enhancement, especially in sprint performance. Additional benefits of Cr supplementation have also been noticed for high-intensity long-endurance tasks, e.g. shortening of recovery periods after physical exercise.The present article summarizes recent findings on the influence of Cr supplementation on energy metabolism, and introduces the Cr transporter protein (CreaT), responsible for uptake of Cr into cells, as one of the key-players for the multi-faceted regulation of cellular Cr homeostasis. Furthermore, it is suggested that patients with disturbances in Cr metabolism or with different neuro-muscular diseases may benefit from Cr supplementation as an adjuvant therapy to relieve or delay the onset of symptoms. Although it is still unclear how Cr biosynthesis and transport are regulated in health and disease, so far there are no reports of harmful side effects of Cr loading in humans. However, in this study, we report that chronic Cr supplementation in rats down-regulates in vivo the expression of the CreaT. In addition, we describe the presence of CreaT isoforms most likely generated by alternative splicing. 相似文献
947.
The chloroplast NADPH thioredoxin reductase C,NTRC, controls non‐photochemical quenching of light energy and photosynthetic electron transport in Arabidopsis 下载免费PDF全文
Belén Naranjo Clara Mignée Anja Krieger‐Liszkay Dámaso Hornero‐Méndez Lourdes Gallardo‐Guerrero Francisco Javier Cejudo Marika Lindahl 《Plant, cell & environment》2016,39(4):804-822
High irradiances may lead to photooxidative stress in plants, and non‐photochemical quenching (NPQ) contributes to protection against excess excitation. One of the NPQ mechanisms, qE, involves thermal dissipation of the light energy captured. Importantly, plants need to tune down qE under light‐limiting conditions for efficient utilization of the available quanta. Considering the possible redox control of responses to excess light implying enzymes, such as thioredoxins, we have studied the role of the NADPH thioredoxin reductase C (NTRC). Whereas Arabidopsis thaliana plants lacking NTRC tolerate high light intensities, these plants display drastically elevated qE, have larger trans‐thylakoid ΔpH and have 10‐fold higher zeaxanthin levels under low and medium light intensities, leading to extremely low linear electron transport rates. To test the impact of the high qE on plant growth, we generated an ntrc–psbs double‐knockout mutant, which is devoid of qE. This double mutant grows faster than the ntrc mutant and has a higher chlorophyll content. The photosystem II activity is partially restored in the ntrc–psbs mutant, and linear electron transport rates under low and medium light intensities are twice as high as compared with plants lacking ntrc alone. These data uncover a new role for NTRC in the control of photosynthetic yield. 相似文献
948.
María Angeles Verdugo Vinatha Sreeramkumar Lourdes Hernández‐Cosido Alfonso Mora Georgiana Crainiciuc María Laura Sáiz Edgar Bernardo Luis Leiva‐Vega Elena Rodríguez Victor Bondía Jorge L Torres Sonia Perez‐Sieira Luis Ortega Ana Cuenda Francisco Sanchez‐Madrid Rubén Nogueiras Andrés Hidalgo Miguel Marcos Guadalupe Sabio 《The EMBO journal》2016,35(5):536-552
Non‐alcoholic fatty liver disease (NAFLD) is a major health problem and the main cause of liver disease in Western countries. Although NAFLD is strongly associated with obesity and insulin resistance, its pathogenesis remains poorly understood. The disease begins with an excessive accumulation of triglycerides in the liver, which stimulates an inflammatory response. Alternative p38 mitogen‐activated kinases (p38γ and p38δ) have been shown to contribute to inflammation in different diseases. Here we demonstrate that p38δ is elevated in livers of obese patients with NAFLD and that mice lacking p38γ/δ in myeloid cells are resistant to diet‐induced fatty liver, hepatic triglyceride accumulation and glucose intolerance. This protective effect is due to defective migration of p38γ/δ‐deficient neutrophils to the damaged liver. We further show that neutrophil infiltration in wild‐type mice contributes to steatosis development by means of inflammation and liver metabolic changes. Therefore, p38γ and p38δ in myeloid cells provide a potential target for NAFLD therapy. 相似文献
949.
Patrizia Restani Chiara Di Lorenzo Alicia Garcia-Alvarez Mihaela Badea Alessandro Ceschi Bernadette Egan Lorena Dima Saskia Lüde Franco M. Maggi Angela Marculescu Raimon Milà-Villarroel Monique M. Raats Lourdes Ribas-Barba Liisa Uusitalo Lluís Serra-Majem 《PloS one》2016,11(2)
Background
The use of food supplements containing botanicals is increasing in European markets. Although intended to maintain the health status, several cases of adverse effects to Plant Food Supplements (PFS) have been described.Objectives
To describe the self-reported adverse effects collected during the European PlantLIBRA PFS Consumer Survey 2011–2012, with a critical evaluation of the plausibility of the symptomatology reported using data from the literature and from the PlantLIBRA Poisons Centers'' survey.Subjects/Setting
From the total sample of 2359 consumers involved in the consumers'' survey, 82 subjects reported adverse effects due to a total of 87 PFS.Results
Cases were self-reported, therefore causality was not classified on the basis of clinical evidence, but by using the frequency/strength of adverse effects described in scientific papers: 52 out of 87 cases were defined as possible (59.8%) and 4 as probable (4.6%). Considering the most frequently cited botanicals, eight cases were due to Valeriana officinalis (garden valerian); seven to Camellia sinensis (tea); six to Ginkgo biloba (Maidenhair tree) and Paullinia cupana (guarana). Most adverse events related to the gastrointestinal tract, nervous and cardiovascular systems.Conclusions
Comparing the data from this study with those published in scientific papers and obtained by the PlantLIBRA Poisons Centers'' survey, some important conclusions can be drawn: severe adverse effects to PFS are quite rare, although mild or moderate adverse symptoms can be present. Data reported in this paper can help health professionals (and in particular family doctors) to become aware of possible new problems associated with the increasing use of food supplements containing botanicals. 相似文献950.
Ana Rita Lima Maria de Lourdes Bastos Márcia Carvalho Paula Guedes de Pinho 《Translational oncology》2016,9(4):357-370
Prostate cancer (PCa) is the most frequently diagnosed cancer and the second leading cause of cancer death among men in Western countries. Current screening techniques are based on the measurement of serum prostate specific antigen (PSA) levels and digital rectal examination. A decisive diagnosis of PCa is based on prostate biopsies; however, this approach can lead to false-positive and false-negative results. Therefore, it is important to discover new biomarkers for the diagnosis of PCa, preferably noninvasive ones. Metabolomics is an approach that allows the analysis of the entire metabolic profile of a biological system. As neoplastic cells have a unique metabolic phenotype related to cancer development and progression, the identification of dysfunctional metabolic pathways using metabolomics can be used to discover cancer biomarkers and therapeutic targets. In this study, we review several metabolomics studies performed in prostatic fluid, blood plasma/serum, urine, tissues and immortalized cultured cell lines with the objective of discovering alterations in the metabolic phenotype of PCa and thus discovering new biomarkers for the diagnosis of PCa. Encouraging results using metabolomics have been reported for PCa, with sarcosine being one of the most promising biomarkers identified to date. However, the use of sarcosine as a PCa biomarker in the clinic remains a controversial issue within the scientific community. Beyond sarcosine, other metabolites are considered to be biomarkers for PCa, but they still need clinical validation. Despite the lack of metabolomics biomarkers reaching clinical practice, metabolomics proved to be a powerful tool in the discovery of new biomarkers for PCa detection. 相似文献