全文获取类型
收费全文 | 5421篇 |
免费 | 366篇 |
国内免费 | 1篇 |
专业分类
5788篇 |
出版年
2023年 | 40篇 |
2022年 | 101篇 |
2021年 | 195篇 |
2020年 | 162篇 |
2019年 | 175篇 |
2018年 | 227篇 |
2017年 | 188篇 |
2016年 | 261篇 |
2015年 | 322篇 |
2014年 | 358篇 |
2013年 | 398篇 |
2012年 | 491篇 |
2011年 | 407篇 |
2010年 | 233篇 |
2009年 | 203篇 |
2008年 | 258篇 |
2007年 | 256篇 |
2006年 | 209篇 |
2005年 | 178篇 |
2004年 | 158篇 |
2003年 | 134篇 |
2002年 | 139篇 |
2001年 | 111篇 |
2000年 | 80篇 |
1999年 | 72篇 |
1998年 | 29篇 |
1997年 | 24篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 30篇 |
1991年 | 30篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1968年 | 6篇 |
排序方式: 共有5788条查询结果,搜索用时 0 毫秒
91.
Adriana Fernanda K. Vizuete Matheus Mittmann Hennemann Carlos Alberto Gonçalves Diogo Losch de Oliveira 《Neurochemical research》2017,42(10):2730-2742
Epilepsy prevalence is high in infancy and in the elderly population. Lithium–pilocarpine is widely used to induce experimental animal models of epilepsy, leading to similar neurochemical and morphological alterations to those observed in temporal lobe epilepsy. As astrocytes have been implicated in epileptic disorders, we hypothesized that specific astroglial changes accompany and contribute to epileptogenesis. Herein, we evaluated time-dependent astroglial alterations in the hippocampus of young (27-day-old) rats at 1, 14 and 56 days after Li–pilocarpine-induced status epilepticus (SE), corresponding to different phases in this model of epilepsy. We determined specific markers of astroglial activation: GFAP, S100B, glutamine synthetase (GS), glutathione (GSH) content, aquaporin-4 (AQP-4) and potassium channel Kir 4.1; as well as epileptic behavioral, inflammatory and neurodegenerative changes. Phase-dependent signs of hippocampal astrogliosis were observed, as demonstrated by increments in GFAP, S100B and GS. Astrocyte dysfunction in the hippocampus was characterized, based on the decrease in GSH content, AQP-4 and Kir 4.1 channels. Degenerating neurons were identified by Fluoro-Jade C staining. We found a clear, early (at SE1) and persistent (at SE56) increase in cerebrospinal fluid (CSF) S100B levels. Additionally, serum S100B was found to decrease soon after SE induction, implicating a rapid-onset increase in the CSF/serum S100B ratio. However, serum S100B increased at SE14, possibly reflecting astroglial activation and/or long-term increase in cerebrovascular permeability. Moreover, we suggest that peripheral S100B levels may represent a useful marker for SE in young rats and for follow up during the chronic phases of this model of epilepsy. Together, results reinforce and extend the idea of astroglial involvement in epileptic disorders. 相似文献
92.
Maternal protein restriction during gestation and lactation in the rat results in increased brain levels of kynurenine and kynurenic acid in their adult offspring 下载免费PDF全文
93.
94.
Ingrid L.M. Souza Natália H. Oliveira Pierina A.M. Huamaní Anh-Tuan S. Martin Zaine L.M. Borgonovo Lia S. Nakao Silvio M. Zanata 《Experimental cell research》2021,398(2):112415
A Disintegrin And Metalloprotease 23 (ADAM23) is a member of the ADAMs family of transmembrane proteins, mostly expressed in nervous system, and involved in traffic and stabilization of Kv1-potassium channels, synaptic transmission, neurite outgrowth, neuronal morphology and cell adhesion. Also, ADAM23 has been linked to human pathological conditions, such as epilepsy, cancer metastasis and cardiomyopathy. ADAM23 functionality depends on the molecule presence at the cell surface and along the secretory pathway, as expected for a cell surface receptor. Because endocytosis is an important functional regulatory mechanism of plasma membrane receptors and no information is available about the traffic or turnover of non-catalytic ADAMs, we investigated ADAM23 internalization, recycling and half-life properties. Here, we show that ADAM23 undergoes constitutive internalization from the plasma membrane, a process that depends on lipid raft integrity, and is redistributed to intracellular vesicles, especially early and recycling endosomes. Furthermore, we observed that ADAM23 is recycled from intracellular compartments back to the plasma membrane and thus has longer half-life and higher cell surface stability compared with other ADAMs. Our findings suggest that regulation of ADAM23 endocytosis/stability could be exploited therapeutically in diseases in which ADAM23 is directly involved, such as epilepsy, cancer progression and cardiac hypertrophy. 相似文献
95.
96.
Jordi Gamir Rocío Torres-Vera Carlos Rial Estefanía Berrio Pedro M. de Souza Campos Rosa M. Varela Francisco A. Macías María J. Pozo Victor Flors Juan A. López-Ráez 《Plant, cell & environment》2020,43(7):1655-1668
Strigolactones (SLs) are important ex-planta signalling molecules in the rhizosphere, promoting the association with beneficial microorganisms, but also affecting plant interactions with harmful organisms. They are also plant hormones in-planta, acting as modulators of plant responses under nutrient-deficient conditions, mainly phosphate (Pi) starvation. In the present work, we investigate the potential role of SLs as regulators of early Pi starvation signalling in plants. A short-term pulse of the synthetic SL analogue 2′-epi-GR24 promoted SL accumulation and the expression of Pi starvation markers in tomato and wheat under Pi deprivation. 2′-epi-GR24 application also increased SL production and the expression of Pi starvation markers under normal Pi conditions, being its effect dependent on the endogenous SL levels. Remarkably, 2′-epi-GR24 also impacted the root metabolic profile under these conditions, promoting the levels of metabolites associated to plant responses to Pi limitation, thus partially mimicking the pattern observed under Pi deprivation. The results suggest an endogenous role for SLs as Pi starvation signals. In agreement with this idea, SL-deficient plants were less sensitive to this stress. Based on the results, we propose that SLs may act as early modulators of plant responses to P starvation. 相似文献
97.
F.M. Gomes I.B. Ramos C. Wendt W. Girard-Dias W. De Souza E.A. Machado E.A. K. Miranda 《European journal of histochemistry : EJH》2013,57(4)
Inorganic polyphosphate (PolyP) is a biological polymer that plays important roles in the cell physiology of both prokaryotic and eukaryotic organisms. Among the available methods for PolyP localization and quantification, a 4’,6-diamidino-2-phenylindole(DAPI)-based assay has been used for visualization of PolyP-rich organelles. Due to differences in DAPI permeability to different compartments and/or PolyP retention after fixation, a general protocol for DAPI-PolyP staining has not yet been established. Here, we tested different protocols for DAPI-PolyP detection in a range of samples with different levels of DAPI permeability, including subcellular fractions, free-living cells and cryosections of fixed tissues. Subcellular fractions of PolyP-rich organelles yielded DAPI-PolyP fluorescence, although those with a complex external layer usually required longer incubation times, previous aldehyde fixation and/or detergent permeabilization. DAPI-PolyP was also detected in cryosections of OCT-embedded tissues analyzed by multiphoton microscopy. In addition, a semi-quantitative fluorimetric analysis of DAPI-stained fractions showed PolyP mobilization in a similar fashion to what has been demonstrated with the use of enzyme-based quantitative protocols. Taken together, our results support the use of DAPI for both PolyP visualization and quantification, although specific steps are suggested as a general guideline for DAPI-PolyP staining in biological samples with different degrees of DAPI and PolyP permeability.Key words: DAPI, polyphosphate, fluorescence, fluorimetry 相似文献
98.
Valéria Cataneli Pereira Maria de Lourdes Ribeiro de Souza da Cunha 《Memórias do Instituto Oswaldo Cruz》2013,108(7):939-942
Coagulase-negative staphylococci (CoNS) are the microorganisms most frequently isolated from clinical samples and are commonly found in neonatal blood cultures. Oxacillin is an alternative treatment of choice for CoNS infections; however, resistance to oxacillin can have a substantial impact on healthcare by adversely affecting morbidity and mortality. The objective of this study was to detect and characterise oxacillin-resistant CoNS strains in blood cultures of newborns hospitalised at the neonatal ward of the University Hospital of the Faculty of Medicine of Botucatu. One hundred CoNS strains were isolated and the mecA gene was detected in 69 of the CoNS strains, including 73.2% of Staphylococcus epidermidis strains, 85.7% of Staphylococcus haemolyticus strains, 28.6% of Staphylococcus hominis strains and 50% of Staphylococcus lugdunensis strains. Among these oxacillin-resistant CoNS strains, staphylococcal cassette chromosome mec (SCCmec) type I was identified in 24.6%, type II in 4.3%, type III in 56.5% and type IV in 14.5% of the strains. The data revealed an increase in the percentage of CoNS strains isolated from blood cultures from 1991-2009. Furthermore, a predominant SCCmec profile of the oxacillin-resistant CoNS strains isolated from neonatal intensive care units was identified with a prevalence of SCCmec types found in hospital-acquired strains. 相似文献
99.
Tiago F. Carrijo Divino Brandão Danilo E. de Oliveira Diogo A. Costa Thiago Santos 《Journal of Insect Conservation》2009,13(6):575-581
The advance of agricultural frontier may cause the Cerrado (Brazilian savanna) to disappear before 2030. This work focuses
on measuring the impact of pasture implantation on a cerrado’s termite fauna. Termites were sampled in a cerrado sensu stricto
and a pasture, originally cerrado. All species were classified as their feeder group, accumulation curves were made and Shannon-Wiener
indexes and β diversity were calculated for both areas. Cerrado was richer than pasture and species composition differed considerably,
leading β diversity to a high value. The humivorous was the most representative species, followed by grass/litter feeders, xylophagous
and, less representative, the intermediates. There were more xylophagous and intermediates species on cerrado than in pasture;
the grass/litter feeders were more abundant in pasture, but didn’t differed in number or species; and humivorous didn’t differed
neither in richness nor in abundance. This work shows that the simplification of the habitat is indeed causing the extinction
of populations that depend on some specifics resource. 相似文献
100.
Paulo Cesar Gomes Bibiana Monson de Souza Nathalia Baptista Dias Patrícia Brigatte Danilo Mourelle Helen Andrade Arcuri Marcia Perez dos Santos Cabrera Rodrigo Guerino Stabeli João Ruggiero Neto Mario Sergio Palma 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014