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51.
Metabolism of 3- and 4-phosphorylated phosphatidylinositols in stomatal guard cells of Commelina communis L. 总被引:2,自引:0,他引:2
Paroo N. Parmar Charles A. Brearley 《The Plant journal : for cell and molecular biology》1995,8(3):425-433
Within the plant kingdom the stomatal guard cell is presented as a model system of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]-mediated signal transduction. Despite this it is only recently that the phosphoinositide components of animal signal transduction pathways have been identified in stomatal guard cells. Interestingly, stomatal guard cells contain both 3- and 4-phosphorylated phosphatidylinositols though their relative contributions to signalling remain undefined. An appraisal of the routes of synthesis and rates of turnover of these phosphatidylinositols would appear timely as the in vivo biosynthesis of these components is a much neglected facet of the phosphoinositide-mediated signalling paradigm as purported to apply to plants. A non-equilibrium [32P]Pi labelling strategy and enzymic and chemical dissection of labelled phosphatidylinositols have been used to address not only the route of synthesis but also the rates of turnover of phosphatidylinositols in stomatal guard cells of Commelina communis L. The specific activity of the ATP pool of isolated guard cells was found to increase over a 4 h period when labelled from [32P]Pi. In separate experiments, isolated guard cells were labelled over a 40–240 min period, their lipids extracted, deacylated and resolved by HPLC. Glycerophosphoinositol phosphate (GroPInsP) and glycerophosphoinositol bisphosphate (GroPInsP2) peaks were desalted and enzymically cleaved with alkaline phosphatase and human erythrocyte ghosts, respectively. The monoester phosphate in phosphatidylinositol 4-monophosphate (PtdIns4P) accounted for 90–97% of the [32P]Pi label while the 4- and 5-monoester phosphates of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] accounted for typically 39% and 61% respectively. Therefore, the evidence is consistent with synthesis of PtdIns(4,5)P2 by successive 4- and 5-phosphorylation of phosphatidylinositol (PtdIns). This study therefore represents the first report of the pathway of the synthesis of 4- and 5-phosphorylated phosphatidylinositols in a single defined hormone-responsive plant cell type. The monoester phosphate in phosphatidylinositol 3-monophosphate (PtdIns3P) accounted for 83–95% of the 32P label. It was not possible, however, to determine the route of synthesis of phosphatidylinositol 3,4-bisphosphate [PtdIns(3,4)P2] owing to the rapid attainment of equilibrium between the 3- and 4-monoester phosphates of PtdIns(3,4)P2, each containing approximately 50% of the label at just 40 min of labelling. Turnover of PtdIns3P was quicker than that of PtdIns4P. Similarly, turnover of PtdIns(3,4)P2 was quicker than that of PtdIns(4,5)P2, and in mass terms PtdIns(3,4)P2 appeared to predominate over PtdIns(4,5)P2. By analogy with animal systems, in which signalling molecules such as PtdIns(4,5)P2 show considerable basal turnover, the evidence presented is consistent with signalling roles for PtdIns3P and PtdIns(3,4)P2 in addition to those previously indicated for PtdIns(4,5)P2 in stomatal guard cells. 相似文献
52.
铁皮石斛的离体开花 总被引:9,自引:0,他引:9
铁皮石斛(Dendrobium candidum),为一种野生兰科植物,在栽培条件下,从种子萌发到开花通常需要3~4a.研究了多种植物激素和多胺对该种石斛组织培养中花芽形成的影响,结果表明在培养基中加入合适浓度的亚精胺(spermidine)或BA(6-苄基腺嘌呤),或同时加入NAA(萘乙酸)和BA均可诱导原球茎或由之形成的无根小苗在3~6个月开花,频率在31.6%~45.8%.当将原球茎在加有ABA(脱落酸)的培养基上预培养后再移到加有BA的培养基上,花芽形成的频率可提高到平均达82.8%(个别实验中可达100%),这种诱导提早开花的现象也与实验材料的发育阶段(原球茎、无根小苗、已生根的小苗)有关,通常发生在根的形成受到完全或部分抑制的情况中. 相似文献
53.
54.
Efficiencies of different genes and different tree-building methods in recovering a known vertebrate phylogeny 总被引:24,自引:6,他引:18
The relative efficiencies of different protein-coding genes of the
mitochondrial genome and different tree-building methods in recovering a
known vertebrate phylogeny (two whale species, cow, rat, mouse, opossum,
chicken, frog, and three bony fish species) was evaluated. The
tree-building methods examined were the neighbor joining (NJ), minimum
evolution (ME), maximum parsimony (MP), and maximum likelihood (ML), and
both nucleotide sequences and deduced amino acid sequences were analyzed.
Generally speaking, amino acid sequences were better than nucleotide
sequences in obtaining the true tree (topology) or trees close to the true
tree. However, when only first and second codon positions data were used,
nucleotide sequences produced reasonably good trees. Among the 13 genes
examined, Nd5 produced the true tree in all tree-building methods or
algorithms for both amino acid and nucleotide sequence data. Genes Cytb and
Nd4 also produced the correct tree in most tree-building algorithms when
amino acid sequence data were used. By contrast, Co2, Nd1, and Nd41 showed
a poor performance. In general, large genes produced better results, and
when the entire set of genes was used, all tree-building methods generated
the true tree. In each tree-building method, several distance measures or
algorithms were used, but all these distance measures or algorithms
produced essentially the same results. The ME method, in which many
different topologies are examined, was no better than the NJ method, which
generates a single final tree. Similarly, an ML method, in which many
topologies are examined, was no better than the ML star decomposition
algorithm that generates a single final tree. In ML the best substitution
model chosen by using the Akaike information criterion produced no better
results than simpler substitution models. These results question the
utility of the currently used optimization principles in phylogenetic
construction. Relatively simple methods such as the NJ and ML star
decomposition algorithms seem to produce as good results as those obtained
by more sophisticated methods. The efficiencies of the NJ, ME, MP, and ML
methods in obtaining the correct tree were nearly the same when amino acid
sequence data were used. The most important factor in constructing reliable
phylogenetic trees seems to be the number of amino acids or nucleotides
used.
相似文献
55.
56.
Chris Brearley Anthony Priestley James Leighton-Scott Michel Christen 《BMC clinical pharmacology》2007,7(1):10
Background
Growth hormone (GH) is used to treat growth hormone deficiency (GHD, adult and paediatric), short bowel syndrome in patients on a specialized diet, HIV-associated wasting and, in children, growth failure due to a number of disorders including Turner's syndrome and chronic renal failure, and in children born small for gestational age. Different brands and generic forms of recombinant human growth hormone (r-hGH) are approved for varying indications in different countries. New ways of administering GH are required because the use of a needle and syringe or a device where a patient still has to insert the needle manually into the skin on a daily basis can lead to low adherence and sub-optimal treatment outcomes. The objective of this study was to assess the relative bioavailability of r-hGH (Saizen®, Merck Serono) administered by a new needle-free device, cool.click? 2, and a standard needle and syringe.Methods
The study was performed with 38 healthy volunteers who underwent pituitary somatotrope cell down-regulation using somatostatin, according to a randomized, two-period, two-sequence crossover design. Following subcutaneous administration of r-hGH using cool.click? 2 or needle and syringe, pharmacokinetic parameters were analysed by non-compartmental methods. Bioequivalence was assessed based on log-transformed AUC and Cmax values.Results
The 90% confidence intervals for test/reference mean ratio of the plasma pharmacokinetic variables Cmax and AUC0-inf were 103.7–118.3 and 97.1–110.0, respectively, which is within the accepted bioequivalence range of 80–125%. r-hGH administered by cool.click? 2 is, therefore, bioequivalent to administration by needle and syringe with respect to the rate and extent of GH exposure. Treatment using cool.click? 2 was found to be well tolerated. With cool.click? 2 the tmax was less (3.0 hours) than for needle and syringe delivery (4.5 hours), p = 0.002 (Friedman test), although this is unlikely to have any clinical implications.Conclusion
These results demonstrate that cool.click? 2 delivers subcutaneous r-hGH exposure that is bioequivalent to the conventional mode of injection. The new device has the additional advantage of being needle-free, and should help to increase patient adherence and achieve good therapeutic outcomes from r-hGH treatment.57.
采用红外气体分析仪,于2008年10月17-19日连续3个昼夜原位监测了荷木的树干CO_2释放通量、树干温度、木质部液流密度和CO_2浓度.结果表明:树干CO_2释放通量(EA)日变化呈S形曲线,不同径级间差异显著.EA与树干温度呈显著幂函数关系(0.24Abstract: By using a Li-820 infra-red CO_2 gas analyzer, an in situ measurement of Schima super-ba stem CO_2 efflux was conducted for three consecutive days from 17 to 19 October 2008. In the meantime, the stem temperature, xylem sap efflux density, and xylem CO_2 concentration were measured. The stem CO_2 efflux had a diurnal variation of "S" pattern, and differed significantly with stem diameter. There was a significant exponential relationship between stem CO_2 efflux and stem temperature (0. 24 < R~2 < 0. 78). The temperature coefficient (b) and regression coeffi-cient (R~2) were higher at nighttime than at daytime, and the Q_(10) value ranged from 2. 01 to 2. 79. The stem CO_2 efflux correlated significantly with the xylem CO_2 concentration, and the best regression curve was cubic (R~2= 0. 48). Excluding the effects of stem temperature, the stem CO_2 efflux showed a significant negative correlation with xylem sap flux density (r =-0.462). Therefore, only using simple temperature function to estimate stem CO_2 efflux would yield a significant error, and xylem sap flux should be taken into consideration in the stem CO_2 emux estimation. 相似文献
58.
J. W. F. Slik Shin-Ichiro Aiba Francis Q. Brearley Chuck H. Cannon Olle Forshed Kanehiro Kitayama Hidetoshi Nagamasu Reuben Nilus John Payne Gary Paoli Axel D. Poulsen Niels Raes Douglas Sheil Kade Sidiyasa Eizi Suzuki Johan L. C. H. van Valkenburg 《Global Ecology and Biogeography》2010,19(1):50-60
Aim Tropical forests have been recognized as important global carbon sinks and sources. However, many uncertainties about the spatial distribution of live tree above‐ground biomass (AGB) remain, mostly due to limited availability of AGB field data. Recent studies in the Amazon have already shown the importance of large sample size for accurate AGB gradient analysis. Here we use a large stem density, basal area, community wood density and AGB dataset to study and explain their spatial patterns in an Asian tropical forest. Location Borneo, Southeast Asia. Methods We combined stem density, basal area, community wood density and AGB data from 83 locations in Borneo with an environmental database containing elevation, climate and soil variables. The Akaike information criterion was used to select models and environmental variables that best explained the observed values of stem density, basal area, community wood density and AGB. These models were used to extrapolate these parameters across Borneo. Results We found that wood density, stem density, basal area and AGB respond significantly, but differentially, to the environment. AGB was only correlated with basal area, but not with stem density and community wood specific gravity. Main conclusions Unlike results from Amazonian forests, soil fertility was an important positive correlate for AGB in Borneo while community wood density, which is a main driver of AGB in the Neotropics, did not correlate with AGB in Borneo. Also, Borneo's average AGB of 457.1 Mg ha?1 was c. 60% higher than the Amazonian average of 288.6 Mg ha?1. We find evidence that this difference might be partly explained by the high density of large wind‐dispersed Dipterocarpaceae in Borneo, which need to be tall and emergent to disperse their seeds. Our results emphasize the importance of Bornean forests as carbon sinks and sources due to their high carbon storage capacity. 相似文献
59.
Neuza M Alcantara-Neves Samuel J Badaró Mariese CA dos Santos Lain Pontes-de-Carvalho Maurício L Barreto 《Respiratory research》2010,11(1):114