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991.
Niyaz Ahmed SManjulata Devi M de los Á Valverde P Vijayachari Robert S Machang'u William A Ellis Rudy A Hartskeerl 《Annals of clinical microbiology and antimicrobials》2006,5(1):1-10
Background
Multi-drug resistant Pseudomonas aeruginosa nosocomial infections are increasingly recognized worldwide. In this study, we focused on the virulence of multi-drug resistant clinical strains P. aeruginosa against the intestinal epithelial barrier, since P. aeruginosa can cause lethal sepsis from within the intestinal tract of critically ill and immuno-compromised patients via mechanisms involving disruption of epithelial barrier function.Methods
We screened consecutively isolated multi-drug resistant P. aeruginosa clinical strains for their ability to disrupt the integrity of human cultured intestinal epithelial cells (Caco-2) and correlated these finding to related virulence phenotypes such as adhesiveness, motility, biofilm formation, and cytotoxicity.Results
Results demonstrated that the majority of the multi-drug resistant P. aeruginosa clinical strains were attenuated in their ability to disrupt the barrier function of cultured intestinal epithelial cells. Three distinct genotypes were found that displayed an extreme epithelial barrier-disrupting phenotype. These strains were characterized and found to harbor the exoU gene and to display high swimming motility and adhesiveness.Conclusion
These data suggest that detailed phenotypic analysis of the behavior of multi-drug resistant P. aeruginosa against the intestinal epithelium has the potential to identify strains most likely to place patients at risk for lethal gut-derived sepsis. Surveillance of colonizing strains of P. aeruginosa in critically ill patients beyond antibiotic sensitivity is warranted. 相似文献992.
Oscar Skewes Fernando Gonzalez Rodrigo Olave Alberto Ávila Víctor Vargas Peter Paulsen Horst Erich König 《European Journal of Wildlife Research》2006,52(4):292-296
Castor canadensis specimens were imported from Canada and released in the wilderness on the Argentinean part of Tierra del Fuego (TDF) in the
year 1946. First studies on the development of the beaver population and subsequent environmental changes were conducted four
decades later and indicated a strong expansion of these animals, with negative effects on the forest, especially the dominant
Nothofagus sp. Between 1999 and 2001, we investigated the density of the beaver population in the Chilean part of TDF and the southern
adjacent island Navarino (NAV). Data were mapped into a geographical information system. The mean colony density was 1.03
(range: 0.15–1.91) and 1.1 per km watercourse for 75% of the area of TDF (mainly south and central region) and the total NAV
island, respectively. The average number of individuals estimated per colony was five. Based on these findings, the number
of beavers in the Chilean part of TDF and on NAV was estimated at 61,300 individuals. The population is increasing and expanding
in the Northern region, with a linear rate of 2.6–6.3 km/year. 相似文献
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995.
M. M. Sánchez-Montoya M. R. Vidal-Abarca T. Puntí J. M. Poquet N. Prat M. Rieradevall J. Alba-Tercedor C. Zamora-Muñoz M. Toro S. Robles M. Álvarez M. L. Suárez 《Hydrobiologia》2009,619(1):39-54
The European Water Framework Directive establishes the need to define stream type-specific reference conditions to identify
“high ecological status”. Methods for selecting reference sites using a priori criteria have been proposed by many authors.
A review of these criteria revealed that the most relevant criteria for streams and rivers were those related to riparian
vegetation, diffuse and point sources of pollution, river morphology and hydrological conditions and regulation. In this work,
we propose 20 criteria that reflect the characteristics of Mediterranean streams and their most frequent disturbances for
the selection of reference sites in Mediterranean streams in Spain. We studied 162 sites located in 33 Mediterranean basins
belonging to five stream types. Of the locations, 57% were selected as a priori reference sites by having applied the proposed
criteria. Reference sites were identified for all stream types except for “large watercourses” which includes the lower reaches
of some rivers in this study area. This a priori selection of reference sites was subjected to validation using the macroinvertebrate
community by applying of an IBMWP threshold, which is considered to be an indicator of undisturbed sites in Mediterranean
streams. This approach determined that whole of this selection (100%) could be considered valid reference sites. Furthermore,
we identified differences in the reference conditions for each stream type on the basis of macroinvertebrate assemblage composition.
Handling editor: R. Bailey 相似文献
996.
Ten reaches of an Atlantic stream located in north‐west Spain were sampled intensively during one summer to characterize the conditions where Atlantic salmon Salmo salar have been re‐introduced along the stream. Fish species richness and diversity showed a downstream increase, which was mainly attributed to the higher number of cyprinid species found in the lower reaches. Moreover, except for brown trout Salmo trutta that appeared to be the most ubiquitous species, the densities of the other species was higher in the lower than in the upper stream reaches. Redundancy analysis showed that the pattern of fish assemblages observed along the studied stream was mainly related to the expected gradient observed in the levels of dissolved oxygen, discharge and mean current speed. There was a significant differentiation between midstream and downstream reaches, both in terms of the composition of their fish assemblages and the freshwater habitat. This study emphasizes the importance of describing the variations in fish assemblages and habitat characteristics along a river to explore its relation to potential changes in the survival of fish populations. In particular, the development of habitat–fish relationships may be a useful tool for water managers to assess the effects of development and restoration projects on the habitat of S. salar. 相似文献
997.
Maria‐Ángeles Arevalo Pedro M. Roldan Pedro J. Chacón Alfredo Rodríguez‐Tebar 《Journal of neurochemistry》2009,111(6):1425-1433
In the nervous system, both the shape and connectivity of neurons are strongly influenced by soluble, extracellular factors. Indeed, we recently demonstrated that after binding to p75NTR, the common neurotrophin receptor, nerve growth factor (NGF) controls the morphology and connectivity of cultured mouse hippocampal neurons by encouraging the production of fewer yet longer dendrites, and by augmenting GABAergic connectivity. These effects of NGF are mediated by the differential expression of Enhancer‐of‐split 1/5 homologs and neurogenin 3. Amyloid β (Aβ), a pathogenic agent in Alzheimer’s disease (AD) is known to bind to p75NTR, hence we studied its influence on cultured hippocampal neurons. At 800 nM, Aβ(1–40) prevents NGF‐induced activation of NF‐κB and consequently, it depresses the expression of Enhancer‐of‐split 1. Thus, at this concentration, the effect of Aβ on neurons is antagonistic to those provoked by NGF and accordingly, neurons sprout more yet shorter dendrites and their GABAergic input decreases. In contrast, at lower concentration, 20 nM, the amyloid induces cellular effects similar to those induced by NGF, both in terms of gene expression, neuronal morphology, and GABAergic connectivity. Our results demonstrate that Aβ may act as a neurotrophic factor that mimics the activity of NGF. However, at higher concentrations, the amyloid behaves as an antagonist of NGF, contributing to the advent of AD. 相似文献
998.
Emma Burgos‐Ramos Gabriel Á Martos‐Moreno Manuela G. López Rosario Herranz David Aguado‐Llera Javier Egea Diana Frechilla Edurne Cenarruzabeitia Rafael León Eduardo Arilla‐Ferreiro Jesús Argente Vicente Barrios 《Journal of neurochemistry》2009,109(2):360-370
The protective effects of insulin‐like growth factor I on the somatostatin (SRIF) system in the temporal cortex after β‐amyloid (Aβ) injury may be mediated through its N‐terminal tripeptide glycine‐proline‐glutamate (GPE). GPE is cleaved to cyclo[Pro‐Gly] (cPG), a metabolite suggested to mediate in neuroprotective actions. We evaluated the effects of GPE and cPG in the temporal cortex of Aβ25–35‐treated rats on SRIF and SRIF receptor protein and mRNA levels, adenylyl cyclase activity, cell death, Aβ25–35 accumulation, cytosolic calcium levels ([Ca2+]c) and the intracellular signaling mechanisms involved. GPE and cPG did not change Aβ25–35 levels, but GPE partially restored SRIF and SRIF receptor 2 protein content and mRNA levels and protected against cell death after Aβ25–35 insult, which was coincident with Akt activation and glycogen synthase kinase 3β inhibition. In addition, GPE displaced glutamate from NMDA receptors and blocked the glutamate induced rise in cytosolic calcium in isolated rat neurons and moderately increased Ca2+ influx per se. Our findings suggest that GPE, but not its metabolite, mimics insulin‐like growth factor I effects on the SRIF system through a mechanism independent of Aβ clearance that involves modulation of calcium and glycogen synthase kinase 3β signaling. 相似文献
999.
The metabolic theory of ecology (MTE) states that metabolic rate, ruled mainly by individual mass and temperature, determines many other biological rates. This view of ecology as ruled by the laws of physics and thermodynamics contrasts with life-history-optimization (LHO) theories, where traits are shaped by evolutionary processes. Integrating the MTE and LHO can lead, however, to a synthetic theory of ecology. In this work, we link the two theories to show that offspring development time is the result of both maternal investment in offspring and the metabolic constraints on offspring growth. We formulate a model that captures how offspring development time is the consequence of both offspring growth rate, determined by temperature and allometric scaling in accordance with the MTE, and the size reached by offspring at the end of the developmental period, determined mainly by LHO and reproductive strategies. We first extend the trade-off between offspring size and offspring number to ectotherms, showing that increased body temperatures result in increased resources available for reproduction. We then combine this trade-off with the general ontogenetic growth model to show that there is a trade-off between the number of offspring produced and offspring development time. The model predicts a shorter developmental time in organisms producing larger numbers of offspring. 相似文献
1000.