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111.
Salt TE 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2002,357(1428):1759-1766
It is known that glutamate is a major excitatory transmitter of sensory and cortical afferents to the thalamus. These actions are mediated via several distinct receptors with postsynaptic excitatory effects predominantly mediated by ionotropic receptors of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate varieties (NMDA). However, there are also other kinds of glutamate receptor present in the thalamus, notably the metabotropic and kainate types, and these may have more complex or subtle roles in sensory transmission. This paper describes recent electrophysiological experiments done in vitro and in vivo which aim to determine how the metabotropic and kainate receptor types can influence transmission through the sensory thalamic relay. A particular focus will be how such mechanisms might operate under physiological conditions. 相似文献
112.
We have determined the DNA sequence of the distal 148 codons of trpE and
all of trpG in Pseudomonas aeruginosa. These genes encode, respectively,
the large and small (glutamine amidotransferase) subunits of anthranilate
synthase, the first enzyme in the tryptophan synthetic pathway. The
sequenced region of trpE is homologous with the distal portion of E. coli
and Bacillus subtilis trpE, whereas the trpG sequence is homologous to the
glutamine amidotransferase subunit genes of a number of bacterial and
fungal anthranilate synthases. The two coding sequences overlap by 23 bp.
Codon usage in these Pseudomonas genes shows a marked preference for codons
ending in G or C, thereby resembling that of trpB, trpA, and several other
chromosomal loci from this species and others with a high G + C content in
their DNA. The deduced amino acid sequence for the P. aeruginosa trpG gene
product differs to a surprising extent from the directly determined amino
acid sequence of the glutamine amidotransferase subunit of P. putida
anthranilate synthase (Kawamura et al. 1978). This suggests that these two
proteins are encoded by loci that duplicated much earlier in the phylogeny
of these organisms but have recently assumed the same function. We have
also determined 490 bp of DNA sequence distal to trpG but have not
ascertained the function of this segment, though it is rich in dyad
symmetries.
相似文献
113.
The components of feeding behavior in rotifers 总被引:3,自引:3,他引:0
George W. Salt 《Hydrobiologia》1987,147(1):271-281
Feeding behavior of a rotifer can be broken into two classes of activities: the rate of successful search and the handling process. The former consists of the following components: Perceptual field (in planktonic rotifers the area of the corona), swimming rate, and attack rate. The second class consists of capture rate, handling time, rejection rate, ingestion, digestion, and assimilation. All evidence indicates that the perceptual field cannot be varied by the rotifer. Swimming rate is variable and under rotifer control, but does not appear to vary with degree of starvation. Attack rate is also under control of the rotifer, at least in the genus Asplanchna. Capture rates vary with the species of food item from zero to 100%. Handling times are longer than one would expect, as are rejection times. Digestion and assimilation appear to vary inversely with rate of ingestion. There is some suggestion in the literature that feeding behavior on very small particles differs from that on larger ones. 相似文献
114.
Acetylcholine and ATP are costored and coreleased during synaptic activity at the electric organ ofTorpedo. It has been suggested that released ATP is converted to adenosine at the synaptic cleft, and in turn this nucleoside would depress the evoked release of acetylcholine. In the present communication we have used a chemiluminescent reaction that let us to monitor continuously the presence of adenosine in this preparation. The chemiluminescent reaction is based on the conversion of adenosine into uric acid and H2O2 by adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase enzymes. The hydrogen peroxide has been detected by peroxidase-luminol mixture. The reaction has a sensitivity on the picomol range and discerned between Adenosine, AMP, ADP, and ATP. We have developed this technique in the hope of understanding whether adenosine is released during synaptic activity or it comes from the released ATP. We have studied the release or formation of adenosine in fragments of the electric organ and in isolated cholinergic nerve terminals obtained from it. In both conditions we have followed the effect of potassium stimulation upon the detection of adenosine. Potassium stimulation increased the extracellular adenosine either in slices or the synaptosomal fraction ofTorpedo electric organ. The presence of , -methylene ADP, an inhibitor of 5-nucleotidase, inhibits the detection of adenosine, suggesting that extracellular adenosine is a consequence of ectocellular dephosphorylation of released ATP. 相似文献
115.
Studies of wireworm populations 总被引:4,自引:0,他引:4
A method has been developed, and is here briefly described, by means of which all the wireworm larvae of all stages can be collected from soil samples. By use of that method, complete wireworm populations have been obtained from soil samples of three types, two of which provide large homogeneous populations for detailed study while the third gives information about the seasonal and spatial infestation of fields. These collections show that the wireworm population of English pasture land is on the average about three times as large as has been commonly supposed. Populations have been found ranging up to ten millions per acre in the top 12 in. of soil. In two pastures studied intensively throughout the year, the wireworm population has been found to consist of large numbers of small larvae, decreasing numbers of larger larvae, and comparatively few of the very large larvae that have usually been allowed to represent the population. Such a composition is shown to be characteristic of wireworm populations under old grass at all seasons of the year and in several fields in different parts of the country. This result suggests that in research on the wireworm problem it is desirable to take into consideration the whole wireworm population throughout the year, not merely the large larvae during the cropping season. 相似文献
116.
Nuclear Localised MORE SULPHUR ACCUMULATION1 Epigenetically Regulates Sulphur Homeostasis in Arabidopsis thaliana 总被引:1,自引:0,他引:1
Xin-Yuan Huang Dai-Yin Chao Anna Koprivova John Danku Markus Wirtz Steffen Müller Francisco J. Sandoval Hermann Bauwe Sanja Roje Brian Dilkes Rüdiger Hell Stanislav Kopriva David E Salt 《PLoS genetics》2016,12(9)
Sulphur (S) is an essential element for all living organisms. The uptake, assimilation and metabolism of S in plants are well studied. However, the regulation of S homeostasis remains largely unknown. Here, we report on the identification and characterisation of the more sulphur accumulation1 (msa1-1) mutant. The MSA1 protein is localized to the nucleus and is required for both S-adenosylmethionine (SAM) production and DNA methylation. Loss of function of the nuclear localised MSA1 leads to a reduction in SAM in roots and a strong S-deficiency response even at ample S supply, causing an over-accumulation of sulphate, sulphite, cysteine and glutathione. Supplementation with SAM suppresses this high S phenotype. Furthermore, mutation of MSA1 affects genome-wide DNA methylation, including the methylation of S-deficiency responsive genes. Elevated S accumulation in msa1-1 requires the increased expression of the sulphate transporter genes SULTR1;1 and SULTR1;2 which are also differentially methylated in msa1-1. Our results suggest a novel function for MSA1 in the nucleus in regulating SAM biosynthesis and maintaining S homeostasis epigenetically via DNA methylation. 相似文献
117.
A loss‐of‐function allele of OsHMA3 associated with high cadmium accumulation in shoots and grain of Japonica rice cultivars
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Jiali Yan Peitong Wang Peng Wang Meng Yang Xingming Lian Zhong Tang Chao‐Feng Huang David E. Salt Fang Jie Zhao 《Plant, cell & environment》2016,39(9):1941-1954
Excessive cadmium (Cd) accumulation in rice poses a risk to food safety. OsHMA3 plays an important role in restricting Cd translocation from roots to shoots. A non‐functional allele of OsHMA3 has been reported in some Indica rice cultivars with high Cd accumulation, but it is not known if OsHMA3 allelic variation is associated with Cd accumulation in Japonica cultivars. In this study, we identified a Japonica cultivar with consistently high Cd accumulation in shoots and grain in both field and greenhouse experiments. The cultivar possesses an OsHMA3 allele with a predicted amino acid mutation at the 380th position from Ser to Arg. The haplotype had no Cd transport activity when the gene was expressed in yeast, and the allele did not complement a known nonfunctional allele of OsHMA3 in F1 test. The allele is present only in temperate Japonica cultivars among diversity panels of 1483 rice cultivars. Different cultivars possessing this allele showed greatly increased root‐to‐shoot Cd translocation and a shift in root Cd speciation from Cd―S to Cd―O bonding determined by synchrotron X‐ray absorption spectroscopy. Our study has identified a new loss‐of‐function allele of OsHMA3 in Japonica rice cultivars leading to high Cd accumulation in shoots and grain. 相似文献
118.
Lee J Nam J Park HC Na G Miura K Jin JB Yoo CY Baek D Kim DH Jeong JC Kim D Lee SY Salt DE Mengiste T Gong Q Ma S Bohnert HJ Kwak SS Bressan RA Hasegawa PM Yun DJ 《The Plant journal : for cell and molecular biology》2007,49(1):79-90
Reversible modifications of target proteins by small ubiquitin-like modifier (SUMO) proteins are involved in many cellular processes in yeast and animals. Yet little is known about the function of sumoylation in plants. Here, we show that the SIZ1 gene, which encodes an Arabidopsis SUMO E3 ligase, regulates innate immunity. Mutant siz1 plants exhibit constitutive systemic-acquired resistance (SAR) characterized by elevated accumulation of salicylic acid (SA), increased expression of pathogenesis-related (PR) genes, and increased resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. Transfer of the NahG gene to siz1 plants results in reversal of these phenotypes back to wild-type. Analyses of the double mutants, npr1 siz1, pad4 siz1 and ndr1 siz1 revealed that SIZ1 controls SA signalling. SIZ1 interacts epistatically with PAD4 to regulate PR expression and disease resistance. Consistent with these observations, siz1 plants exhibited enhanced resistance to Pst DC3000 expressing avrRps4, a bacterial avirulence determinant that responds to the EDS1/PAD4-dependent TIR-NBS-type R gene. In contrast, siz1 plants were not resistant to Pst DC3000 expressing avrRpm1, a bacterial avirulence determinant that responds to the NDR1-dependent CC-NBS-type R gene. Jasmonic acid (JA)-induced PDF1.2 expression and susceptibility to Botrytis cinerea were unaltered in siz1 plants. Taken together, these results demonstrate that SIZ1 is required for SA and PAD4-mediated R gene signalling, which in turn confers innate immunity in Arabidopsis. 相似文献
119.
Spatial extinction or persistence: landscape‐temperature interactions perturb predator–prey dynamics
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Jason L. Salt Celia Bulit Wei Zhang Hongli Qi David J. S. Montagnes 《Ecography》2017,40(10):1177-1186
Recognising that species interact across a range of spatial scales, we explore how landscape structure interacts with temperature to influence persistence. Specifically, we recognise that few studies indicate thermal shifts as the proximal cause of species extinctions; rather, species interactions exacerbated by temperature result in extinctions. Using microcosm‐based experiments, as models of larger landscape processes, we test hypotheses that would be problematic to address through field work. A text‐book predator–prey system (the ciliates Didinium and Paramecium) was used to compare three landscapes: an unfragmented landscape subjected to uniform temperatures (10, 20, 30°C); a fragmented landscape (potentially hosting metapopulations) subjected to these three temperatures; and a fragmented landscape subjected to a spatial temperature gradient (~ 10 to 30°C) – despite the prevalence of natural temperature ecoclines this is the first time such an analysis has been conducted. Initial thermal response‐analysis (growth, mortality, and movement measured between 10 and 30°C) suggested that as temperature increased, the predator might drive the prey to extinction. Thermal preferences (measured at 5 temperatures between 10 and 30°C), indicated that both predator and prey preferred warmer temperatures, with the predator exhibiting the stronger preference, suggesting that cooler regions might act as a prey‐refuge. The landscape level observations, however, did not entirely support the predictions. First, in the unfragmented landscape, increased temperature led to extinctions, but at the highest temperature (where the predator growth can be reduced) the prey survived. Second, at high temperatures the fragmented landscape failed to host metapopulations that would allow predator–prey persistence. Third, the thermal ecocline did not provide heterogeneity that improved stability; rather it forced both species to occupy a smaller realized space, leading toward extinctions. These findings reveal that temperature‐impacted rates and temperature preferences combine to drive predator–prey dynamics and persistence across landscapes. 相似文献
120.
Philip Gibbons Charlie Zammit Kara Youngentob Hugh P. Possingham David B. Lindenmayer Sarah Bekessy Mark Burgman Mark Colyvan Margaret Considine Adam Felton Richard J. Hobbs Karen Hurley Clive McAlpine Michael A. McCarthy Joslin Moore Doug Robinson David Salt Brendan Wintle 《Ecological Management & Restoration》2008,9(3):182-186
Summary Policy‐makers and managers in natural resource management (NRM) often complain that researchers are out of touch. Researchers often complain that policy‐makers and managers make poorly informed decisions. In this article, we report on a meeting between researchers, policy‐makers and managers convened to identify practical solutions to improve engagement between these camps. A necessary starting point is that every researcher and policy‐maker should understand, and tap into, the motivations and reward systems of the other when seeking engagement. For example, researchers can be motivated to engage in policy development if there is a promise of outputs that align with their reward systems such as co‐authored publications. Successful research–policy partnerships are built around personal relationships. As a researcher, you cannot therefore expect your results to inform policy by only publishing in journals. As a policy‐maker, you cannot guarantee engagement from researchers by publicly inviting comment on a document. Actively building and maintaining relationships with key individuals through discussions, meetings, workshops or field days will increase the likelihood that research outcomes will inform policy decisions. We identified secondments, sabbaticals, fellowships and ‘buddies’, an annual national NRM conference and ‘contact mapping’ (a Facebook‐type network) as forums that can catalyse new relationships between researchers and policy‐makers. We challenge every researcher, policy‐maker and manager in NRM to build one new cross‐cultural relationship each year. 相似文献