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81.
Phylogenetic analyses of the rbcL sequences from haptophytes and heterokont algae suggest their chloroplasts are unrelated 总被引:2,自引:0,他引:2
Using the large subunit of RuBisCo (rbcL) sequences from cyanobacteria,
proteobacteria, and diverse groups of algae and green plants, we evaluated
the plastid relationship between haptophytes and heterokont algae. The rbcL
sequences were determined from three taxa of heterokont algae
(Bumilleriopsis filiformis, Pelagomonas calceolata, and Pseudopedinella
elastica) and added to 25 published sequences to obtain a data set
comprising 1,434 unambiguously aligned sites (approximately 98% of the
total rbcL gene). Higher levels of mutational saturation in third codon
positions were observed by plotting the pairwise substitutions with and
without corrections for multiple substitutions at the same site for first
and second codon positions only and for third positions only. In accordance
with this finding phylogeny reconstructions were completed by omitting
third codon positions, thus using 956 bp in weighted-parsimony and
maximum-likelihood analyses. The midpoint-rooted phylogenies showed two
major clusters, one containing cyanobacteria, glaucocystophytes, a
phototrophic euglenoid, chlorophytes, and embryophytes (the green lineage),
the other containing proteobacteria, haptophytes, red algae, a cryptophyte,
and heterokont algae (the non-green lineage). In the nongreen lineage, the
haptophytes formed a sister group to the clade containing heterokont algae,
red algae, and the cryptophyte Guillardia theta. This branching pattern was
well supported in terms of bootstrap values in weighted- parsimony and
maximum-likelihood analyses (100% and 92%, respectively). However, the
phylogenetic relationship among red algae, heterokonts, and a cryptophyte
taxon was not especially well resolved. A four- cluster analysis was
performed to further explore the statistical significance of the
relationship between proteobacteria, red algae (including and excluding
Guillardia theta), haptophytes, and heterokont algae. This test strongly
favored the hypothesis that the heterokonts and red algae are more closely
related to each other than either is to proteobacteria or haptophytes.
Hence, this molecular study based on a plastid-encoded gene provides
additional evidence for a distant relationship between haptophytes and the
heterokont algae. It suggests an evolutionary scenario in which the
ancestor of the haptophyte lineage engulfed a phototrophic eukaryote and,
more recently, the heterokont lineage became phototrophic by engulfing a
red alga.
相似文献
82.
In temperate zones, the potential grain yield of wheat has increased during the twentieth century owing to progressive increases in the harvest index of new varieties, which are principally associated with reduction in plant stature. Crop biomass has not increased substantially. In contrast, the potential grain yield of maize in the USA has increased owing to progressive increases in biomass, principally associated with selection for grain yield at higher population density. Harvest index was already around 0.5 for recommended varieties in 1930, and has not increased significantly since. However, for both crops, the harvest index of a given variety has proved to be a highly‐heritable character, except under severe stress. Less is known about the physiology of tropical maize. This paper reviews evidence from Mexico and Malawi that tropical maize can respond to selection for reduced stature following the same pattern as temperate wheat, but, under other circumstances, the magnitude of harvest index is not highly heritable, varying inconsistently with season, management and environment. It is proposed that these differences arise out of the unique vulnerability of the grain‐setting process around flowering. The plasticity of harvest index under long, favourable conditions, however, remains to be explained, although it is probably also related to the events around grain setting. Nevertheless, to the subsistence farmer, higher harvest index may not be a high priority in crop improvement, because of the need for large quantities of high‐quality stover. 相似文献
83.
TOMÁ HERBEN FRANTIEK KRAHULEC VRA HADINCOVÁ MARCELA KOVÁOVÁ HANA SKÁLOVÁ 《Plant Species Biology》1994,9(3):183-189
Abstract Festuca rubra forms tillers in two different ways: extravaginally and intravaginally. Demography of these two tiller types was observed in seventeen selected tussocks of Festuca rubra s.s. over four growing seasons. Extravaginal tillers were bigger at birth and on the average produced twice as many daughter tillers per tiller. In general, the natality and mortality of extravaginal tillers were less regular than that of intravaginal tillers. Overall tillering rate per tiller was correlated with the density of the surrounding vegetation; mortality, natality and tiller life span were not. High density of the surrounding vegetation did not result in increased formation of extravaginal tillers. The proportion of the extravaginal tillers was not correlated with the density of the F. rubra tussocks. There is no evidence for foraging by extravaginal tillers, but they do act as founders of small clusters of tillers. 相似文献
84.
Distribution and conservation of mobile elements in the genus Drosophila 总被引:13,自引:1,他引:12
Essentially nothing is known of the origin, mode of transmission, and
evolution of mobile elements within the genus Drosophila. To better
understand the evolutionary history of these mobile elements, we examined
the distribution and conservation of homologues to the P, I, gypsy, copia,
and F elements in 34 Drosophila species from three subgenera. Probes
specific for each element were prepared from D. melanogaster and hybridized
to genomic DNA. Filters were washed under conditions of increasing
stringency to estimate the similarity between D. melanogaster sequences and
their homologues in other species. The I element homologues show the most
limited distribution of all elements tested, being restricted to the
melanogaster species group. The P elements are found in many members of the
subgenus Sophophora but, with the notable exception of D. nasuta, are not
found in the other two subgenera. Copia-, gypsy-, and F-element homologues
are widespread in the genus, but their similarity to the D. melanogaster
probe differs markedly between species. The distribution of copia and P
elements and the conservation of the gypsy and P elements is inconsistent
with a model that postulates a single ancient origin for each type of
element followed by mating-dependent transmission. The data can be
explained by horizontal transmission of mobile elements between
reproductively isolated species.
相似文献
85.
86.
Luiz Eduardo Canton Santos Gilcélio Amaral da Silveira Victor Diego Cupertino Costa Aline Gisele Batista Ana Paula Madureira Ant?nio Márcio Rodrigues Carla Alessandra Scorza Henrique Alves Amorim Ricardo Mário Arida Mario Ant?nio Duarte Fúlvio Alexandre Scorza Esper Abr?o Cavalheiro Ant?nio-Carlos Guimar?es de Almeida 《PloS one》2013,8(11)
Non-synaptic mechanisms are being considered the common factor of brain damage in status epilepticus and alcohol intoxication. The present work reports the influence of the chronic use of ethanol on epileptic processes sustained by non-synaptic mechanisms. Adult male Wistar rats administered with ethanol (1, 2 e 3 g/kg/d) during 28 days were compared with Control. Non-synaptic epileptiform activities (NEAs) were induced by means of the zero-calcium and high-potassium model using hippocampal slices. The observed involvement of the dentate gyrus (DG) on the neurodegeneration promoted by ethanol motivated the monitoring of the electrophysiological activity in this region. The DG regions were analyzed for the presence of NKCC1, KCC2, GFAP and CD11b immunoreactivity and cell density. The treated groups showed extracellular potential measured at the granular layer with increased DC shift and population spikes (PS), which was remarkable for the group E1. The latencies to the NEAs onset were more prominent also for the treated groups, being correlated with the neuronal loss. In line with these findings were the predispositions of the treated slices for neuronal edema after NEAs induction, suggesting that restrict inter-cell space counteracts the neuronal loss and subsists the hyper-synchronism. The significant increase of the expressions of NKCC1 and CD11b for the treated groups confirms the existence of conditions favorable to the observed edematous necrosis. The data suggest that the ethanol consumption promotes changes on the non-synaptic mechanisms modulating the NEAs. For the lower ethanol dosage the neurophysiological changes were more effective suggesting to be due to the less intense neurodegenertation. 相似文献
87.
TOSHIHIRO TOKIWA DAVID MODRÝ AKIRA ITO KATEŘINA POMAJBÍKOVÁ KLÁRA J. PETRŽELKOVÁ SOICHI IMAI 《The Journal of eukaryotic microbiology》2010,57(2):115-120
ABSTRACT. Troglocorys cava n. g., n. sp. is described from the feces of wild eastern chimpanzee, Pan troglodytes schweinfurthii, in Uganda. This new species has a spherical body with a frontal lobe, a long vestibulum, a cytoproct located at the posterior dorsal side of the body, an ovoid macronucleus, a contractile vacuole near the cytoproct, and a large concavity on the left surface of the body. Buccal ciliature is non‐retractable and consists of three ciliary zones: an adoral zone surrounding the vestibular opening, a dorso‐adoral zone extending transversely at the basis of the frontal lobe, and a vestibular zone longitudinally extending in a gently spiral curve to line the surface of the vestibulum. Two non‐retractable somatic ciliary zones comprise arches over the body surface: a short dorsal ciliary arch extending transversely at the basis of the frontal lobe and a wide C‐shaped left ciliary arch in the left concavity. Because of the presence of three ciliary zones in the non‐retractable buccal ciliature, the present genus might be a member of the family Blepharocorythidae, but the large left concavity and the C‐shaped left ciliary arch are unique, such structures have never been described from other blepharocorythids. 相似文献
88.
Laila Brito Torres Bruno Henrique Silva Araujo Paulo Henrique Gomes de Castro Francisco Romero Cabral Klena Sarges Marruaz Michelle Silva Araujo Sergio Gomes da Silva José Augusto Pereira Carneiro Muniz Esper Abrão Cavalheiro 《American journal of primatology》2010,72(12):1055-1061
Animal experimentation contributes significantly to the progression of science. Nonhuman primates play a particularly important role in biomedical research not only because of their anatomical, physiological, biochemical, and behavioral similarities with humans but also because of their close phylogenetic affinities. In order to investigate the use of New World primates (NWP) in biomedical research over the last four decades (1966–2005), we performed a quantitative study of the literature listed in bibliographic databases from the Health Sciences. The survey was performed for each genus of NWP that has been bred in the National Center of Primates in Brazil. The number of articles published was determined for each genus and sorted according to the country from which the studies originated and the general scientific field. The data obtained suggests that Brazil is a leader in generating knowledge with NWP models for translational medicine. Am. J. Primatol. 72:1055–1061, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
89.
Luciana Cavalheiro Marti Lorena Pavon Patricia Severino Tatiana Sibov Daiane Guilhen Carlos Alberto Moreira-Filho 《Memórias do Instituto Oswaldo Cruz》2014,109(1):70-79
Dendritic cells (DCs) are antigen (Ag)-presenting cells that activate and stimulate
effective immune responses by T cells, but can also act as negative regulators of
these responses and thus play important roles in immune regulation. Pro-angiogenic
vascular endothelial growth factor (VEGF) has been shown to cause defective DC
differentiation and maturation. Previous studies have demonstrated that the addition
of VEGF to DC cultures renders these cells weak stimulators of Ag-specific T cells
due to the inhibitory effects mediated by VEGF receptor 1 (VEGFR1) and/or VEGFR2
signalling. As the enzyme indoleamine 2,3-dioxygenase (IDO) is recognised as an
important negative regulator of immune responses, this study aimed to investigate
whether VEGF affects the expression of IDO by DCs and whether VEGF-matured DCs
acquire a suppressor phenotype. Our results are the first to demonstrate that VEGF
increases the expression and activity of IDO in DCs, which has a suppressive effect
on Ag-specific and mitogen-stimulated lymphocyte proliferation. These mechanisms have
broad implications for the study of immunological responses and tolerance under
conditions as diverse as cancer, graft rejection and autoimmunity. 相似文献
90.
The worldwide increase in the use of antibiotics as an integral part of poultry and livestock production industry has recently received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria in human beings. To gauge the presence of the aforementioned scenario in the Indian context, a preliminary survey was conducted to assess the use of chlortetracycline (CTC) in 12 commercial layer farms and to quantify and confirm its residue in the egg. Samples of feed and eggs were collected at day 0 (prior to CTC addition), 3rd, 5th and 7th day during treatment and on the 9th and 14th day (2nd and 7th day after withdrawal of CTC) from each of the 12 commercial poultry farms studied. Concentration of CTC in feed was significantly (P<0.01) high on the 3rd, 5th and 7th day. On the 9th day and 14th day CTC concentration in feed was significantly (P<0.01) lower compared to the earlier 3 days studied. A highly significant difference (P<0.01) of the antibiotic residue in egg was observed in all the 5 days with high residual levels of CTC in egg. CTC in feed and its residue in egg were detected even on the 9th and 14th day respectively. 相似文献