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991.
Abstract The effects of doxycycline (DOX) and streptomycin (SM) treatment of Brucella melitensis infected mice on humoral immune response were examined. In female BALB/c mice, DOX was administered at a dose of 50 mg/kg/12 h, for 21 or 45 consecutive days, alone or combined with SM (10 mg/kg/12 h) for 14 days. All treatments induced a significant increase in specific IgG levels (ELISA and CIEP) against LPS and cytosolic antigens of Brucella during treatment. This was not related with therapeutic failure or relapse since all treatments induced a significant reduction in the degree of infection. 相似文献
992.
Nine indigenous cachaça Saccharomyces cerevisiae strains and one wine strain were compared for their trehalose metabolism characteristics under non-lethal (40°C) and lethal (52°C) heat shock, ethanol shock and combined heat and ethanol stresses. The yeast protection mechanism was studied through trehalose concentration, neutral trehalase activity and expression of heat shock proteins Hsp70 and Hsp104. All isolates were able to accumulate trehalose and activate neutral trehalase under stress conditions. No correlation was found between trehalose levels and neutral trehalase activity under heat or ethanol shock. However, when these stresses were combined, a positive relationship was found. After pre-treatment at 40°C for 60 min, and heat shock at 52°C for 8 min, eight strains maintained their trehalose levels and nine strains improved their resistance against lethal heat shock. Among the investigated stresses, heat treatment induced the highest level of trehalose and combined heat and ethanol stresses activated the neutral trehalase most effectively. Hsp70 and Hsp104 were expressed by all strains at 40°C and all of them survived this temperature although a decrease in cell viability was observed at 52°C. The stress imposed by more than 5% ethanol (v/v) represented the best condition to differentiate strains based on trehalose levels and neutral trehalase activity. The investigated S. cerevisiae strains exhibited different characteristics of trehalose metabolism, which could be an important tool to select strains for the cachaça fermentation process. 相似文献
993.
Pimentel C Van Der Straeten D Pires E Faro C Rodrigues-Pousada C 《The FEBS journal》2007,274(10):2523-2539
Cardosin A and cardosin B are two aspartic proteases mainly found in the pistils of cardoon Cynara cardunculus L., whose flowers are traditionally used in several Mediterranean countries in the manufacture of ewe's cheese. We have been characterizing cardosins at the biochemical, structural and molecular levels. In this study, we show that the cardoon aspartic proteases are encoded by a multigene family. The genes for cardosin A and cardosin B, as well as those for two new cardoon aspartic proteases, designated cardosin C and cardosin D, were characterized, and their expression in C. cardunculus L. was analyzed by RT-PCR. Together with cardosins, a partial clone of the cyprosin B gene was isolated, revealing that cardosin and cyprosin genes coexist in the genome of the same plant. As a first approach to understanding what dictates the flower-specific pattern of cardosin genes, the respective gene 5' regulatory sequences were fused with the reporter beta-glucuronidase and introduced into Arabidopsis thaliana. A subsequent deletion analysis of the promoter region of the cardosin A gene allowed the identification of a region of approximately 500 bp essential for gene expression in transgenic flowers. Additionally, the relevance of the leader intron of the cardosin A and B genes for gene expression was evaluated. Our data showed that the leader intron is essential for cardosin B gene expression in A. thaliana. In silico analysis revealed the presence of potential regulatory motifs that lay within the aforementioned regions and therefore might be important in the regulation of cardosin expression. 相似文献
994.
Generalist foraging behavior among stingless bees is accepted but untested, as well as the subsidiary hypothesis of floral preferences in the genus Melipona. Here we analyzed those hypotheses comparing the use of floral sources of pollen, through paired analyses of pollen samples from different colonies of Melipona scutellaris Latreille, in three areas of the Atlantic Forest Domain, in Northern Brazil. From August, 2004 to January, 2005, monthly samples of pollen were collected at the entrance of twelve colonies of M. scutellaris. In two places, four colonies of M. scutellaris were compared with four colonies of africanized Apis mellifera L. The main pollen sources chosen by the colonies of M. scutellaris were flowers of the following plant families, in decreasing order of importance: Myrtaceae, Mimosaceae, Anacardiaceae, Sapindaceae, Caesalpiniaceae and Fabaceae. Productive pollen sources of Asteraceae, Arecaceae e Rubiaceae were heavily exploited by the colonies of A. mellifera and discharged by the colonies of M.scutellaris. Often, both species shared the main productive pollen sources, as the flowers of Myrtaceae and Mimosaceae. On the other hand, no pollen sources were heavily exploited altogether by both of them, as a rule. In different places and periods, the colonies of M. scutellaris presented high intra-specific similarity and they formed distinct clusters apart from A. mellifera. Therefore, the selection of pollen sources by colonies was species dependent. The paired comparisons refute the hypothesis of random flower exploitation by colonies and give support to the subsidiary hypothesis of selectivity or floral preferences by M.scutellaris. 相似文献
995.
Jean Carlos Santos Fernando A. O. Silveira G. Wilson Fernandes 《Evolutionary ecology》2008,22(1):123-137
The Plant Vigor Hypothesis (PVH) proposes that natural selection on female oviposition choice results from higher fitness
of larvae on more vigorous and larger plant modules. For six consecutive years we tested the PVH predictions by investigating
the effect of shoot size of Bauhinia brevipes (Fabaceae) on the oviposition preference and offspring survival of the gall-midge Schizomyia macrocapillata (Diptera: Cecidomyiidae). Additionally, we analyzed the effects of bottom-up and top-down mortality forces on the system.
The hypersensitive reaction (bottom-up effect) accounted for more than 90% larval mortality of S.
macrocapillata, making available few galls to be found and killed by natural enemies (top-down effect). Smaller shoots were always more
abundant while longer shoots were rare. Nevertheless, the percent number of galls induced by S.
macrocapillata was up to 10-fold greater on the largest shoots, corroborating the preference prediction of the PVH. Schizomyia macrocapillata should use over-exploit larger shoots to maximize the preference for, and consequently increase the performance on these
shoots. Our results partially support the performance prediction of the PVH: (1) the observed survival was higher than expected
on longer shoots, and (2) the ratio of survival per shoot was positively related with shoot length only in 2 years. Thus,
we found a link between female preference and larval performance on large-sized shoots, at least in some years. The gall-midge
attack pattern in this study might be an evolved response to maximize the female preference and increased larval performance
on longer shoots of the host plant. 相似文献
996.
Influence of drought on algal biofilms and meiofaunal assemblages of temperate reservoirs and rivers
Maria-José Caramujo Carlos Rafael B. Mendes Paulo Cartaxana Vanda Brotas Maria-José Boavida 《Hydrobiologia》2008,598(1):77-94
The role of hydrological droughts in shaping meiofauna abundance through alterations in biofilm biomass and composition was
investigated. In January 2005, continental Portugal was under a moderate to severe drought resulting from a 40% to 60% decrease
in rainfall during the previous 12 months relative to the long-term average (1961–1990). Reservoir capacity was reduced by
30–50% relative to average values and the width of streams was reduced by 20–80% in the Zêzere River Basin (central Portugal).
Algal biomass and algal class composition of biofilms was assessed through quantification of algal pigments in three reservoir
and six river locations. During drought, habitat alterations are expected to be sharp in rivers while, in the absence of water
quality deterioration, the habitat characteristics of reservoirs are expected to remain fairly unaffected. Chlorophylls and
carotenoid pigments were extracted from biofilm samples and analysed using high performance liquid chromatography (HPLC).
In the winter of 2003, during the period of average rainfall, biofilm biomass did not exceed 5 μg chlorophyll a cm−2 at any location. River biofilm biomass was roughly half of that measured in the reservoirs. In the winter of 2005 (drought),
biofilm biomass increased by more than 5-fold in river locations and remained low or decreased in the reservoirs. Algal biofilms
were either dominated by Bacillariophyceae or by Chlorophyceae regardless of the existence of drought. The relative contribution
of Bacillariophyceae to total biofilm biomass was higher during the drought than under average hydrological conditions. The
abundance of harpacticoids, cladocerans and ostracods was favoured by the drought only in the reservoirs where an increase
in diatom proportion in biofilms was observed. The increase in the abundance of cyclopoid copepods, turbellarians, nematodes
and chironomids in rivers during the drought could be explained by algal class composition and biomass of biofilms and environmental
variables (organic matter sediment content, phosphorus availability content and sediment granulometry). The hydrological drought
appears to regulate meiofauna abundance only in river locations, possibly through the promotion of the growth of biofilms
and the availability of organic matter deposited in rivers during the drought.
Handling editor: D. Ryder 相似文献
997.
998.
Maria A. Ledesma Sara A. Ochoa Ariadnna Cruz Luz M. Rocha-Ramírez Jaime Mas-Oliva Carlos A. Eslava Jorge A. Girón Juan Xicohtencatl-Cortes 《PloS one》2010,5(8)
Background
Enterohemorrhagic Escherichia coli (EHEC) O157:H7, the causative agent of hemorrhagic colitis and the hemolytic uremic syndrome (HUS), produces long bundles of type IV pili (TFP) called hemorrhagic coli pili (HCP). HCP are capable of mediating several phenomena associated with pathogenicity: i) adherence to human and bovine epithelial cells; ii) invasion of epithelial cells; iii) hemagglutination of rabbit erythrocytes; iv) biofilm formation; v) twitching motility; and vi) specific binding to laminin and fibronectin. HCP are composed of a 19 kDa pilin subunit (HcpA) encoded by the hcpA chromosomal gene (called prepilin peptidase-dependent gene [ppdD] in E. coli K-12).Methodology/Principal Findings
In this study we investigated the potential role of HCP of E. coli O157:H7 strain EDL933 in activating the release of pro- and anti-inflammatory cytokines from a variety of host epithelial cells. We found that purified HCP and a recombinant HcpA protein induced significant release of IL-8 and TNF-α, from cultured polarized intestinal cells (T84 and HT-29 cells) and non-intestinal HeLa cells. Levels of proinflammatory IL-8 and TNF-α, but not IL-2, IL6, or IL-10 cytokines, were increased in the presence of HCP and recombinant HcpA after 6 h of incubation with ≥50 ng/ml of protein, suggesting that stimulation of IL-8 and TNF-α are dose and time-dependent. In addition, we also demonstrated that flagella are potent inducers of cytokine production. Furthermore, MAPK activation kinetics studies showed that EHEC induces p38 phosphorylation under HCP-producing conditions, and ERK1/2 and JNK activation was detectable after 3 h of EHEC infection. HT-29 cells were stimulated with epidermal growth factor stimulation of HT-29 cells for 30 min leading to activation of three MAPKs.Conclusions/Significance
The HcpA pilin monomer of the HCP produced by EHEC O157:H7 is a potent inducer of IL-8 and TNF-α release, an event which could play a significant role in the pathogenesis of hemorrhagic colitis caused by this pathogen. 相似文献999.
Agnès Fleury Jael Moreno García Paulina Valdez Aguerrebere María de Sayve Durán Paola Becerril Rodríguez Carlos Larralde Edda Sciutto 《PLoS neglected tropical diseases》2010,4(8)
Background
The ongoing epidemiological transition in Mexico minimizes the relative impact of neurocysticercosis (NC) on public health. However, hard data on the disease frequency are not available.Methodology
All clinical records from patients admitted in the Instituto Nacional de Neurologia y Neurocirugia (INNN) at Mexico City in 1994 and 2004 were revised. The frequencies of hospitalized NC patients in neurology, neurosurgery and psychiatry services, as well as NC mortality from 1995 through 2009, were retrieved. Statistical analyses were made to evaluate possible significant differences in frequencies of NC patients'' admission between 1994 and 2004, and in yearly frequencies of NC patients'' hospitalization and death between 1995 and 2009.Principal Findings
NC frequency in INNN is not significantly different in 1994 and 2004. Between these two years, clinical severity of the cases diminished and the proportion of patients living in Mexico City increased. Yearly frequencies of hospitalization in neurology and psychiatry services were stable, while frequencies of hospitalization in neurosurgery service and mortality significantly decreased between 1995 and 2009.Conclusions
Our findings show a stable tendency of hospital cases during the last decade that should encourage to redouble efforts to control this ancient disease. 相似文献1000.
Ana Lisa V. Gomes Lawrence J. K. Wee Asif M. Khan Laura H. V. G. Gil Ernesto T. A. Marques Jr Carlos E. Calzavara-Silva Tin Wee Tan 《PloS one》2010,5(6)