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71.
Plant Community Composition as a Predictor of Regional Soil Carbon Storage in Alaskan Boreal Black Spruce Ecosystems 总被引:1,自引:0,他引:1
The boreal forest is the largest terrestrial biome in North America and holds a large portion of the world’s reactive soil
carbon. Therefore, understanding soil carbon accumulation on a landscape or regional scale across the boreal forest is useful
for predicting future soil carbon storage. Here, we examined the relationship between floristic composition and ecosystem
parameters, such as soil carbon pools, the carbon-to-nitrogen (C/N) ratio of live black spruce needles, and normalized basal
area increment (NBAI) of trees in black spruce communities, the most widespread forest type in the boreal forest of Alaska.
Variability in ecosystem properties among black spruce stands was as large as that which had previously been documented among
all forest types in the central interior of Alaska; we found an eightfold range in NBAI and fivefold range in mineral soil
carbon and nitrogen pools. Acidic black spruce communities had significantly more carbon in the organic soil horizon than
did nonacidic black spruce communities, but did not differ in any other measured ecosystem parameter. We explained 48% of
the variation in total soil carbon with a combination of plant community indices and abiotic and biotic factors. Plant community
composition was at least as effective as any single environmental factor or stand characteristic in predicting soil C pools
in Alaskan black spruce ecosystems. We conclude that among the community properties analyzed, the presence of key groups of
species, overall species composition, and diversity of certain functional types, especially Sphagnum moss species, are important predictors of soil carbon sequestration in the black spruce forest type. 相似文献
72.
Euphrasia species in Britain attract a large amount of conservation attention due to the recognition of numerous endemic taxa in what is essentially a species‐poor flora. To develop a set of research tools to investigate the evolutionary processes underlying this diversification, a membrane enrichment procedure has been used to isolate five polymorphic microsatellite loci from Euphrasia nemorosa (Pers.) Wallr. These loci amplify polymorphic products in several other British Euphrasia species. 相似文献
73.
Temporal patterns of diversification and microendemism in Eastern Highland endemic barcheek darters (Percidae: Etheostomatinae) 总被引:1,自引:0,他引:1
Eastern North America is the location of the world's most species-rich temperate freshwater fish fauna. Hypotheses regarding the geographic and temporal scale of teleost diversification in this region have not been broadly investigated using absolute divergence time estimates among the constituent lineages. This study used time-calibrated molecular phylogenies estimated from mitochondrial and nuclear genes to investigate the temporal and geographic signatures of diversification within barcheek darters, a clade of allopatrically distributed species endemic to the Eastern Highlands. Results from divergence time estimates using an uncorrelated lognormal model suggest that the barcheek darters are an ancient group with a crown node estimate of 16.3 mya, 95% highest posterior density (HPD): [12.4, 20.5], and the clade is characterized by substantial intraspecific divergence times within several species. In particular, the Caney Fork endemic Etheostoma basilare comprises five strongly supported and deeply divergent clades with a most recent common ancestor estimated at 8.0 mya, 95% HPD: [5.6, 10.7]. These results are concordant with the hypothesis that geologically stable areas of eastern North America have facilitated both the generation and preservation of lineages across a substantial breadth of evolutionary time, and that allopatric speciation in darters has occurred at much smaller spatial scales than previously realized. 相似文献
74.
Möller M Pfosser M Jang CG Mayer V Clark A Hollingsworth ML Barfuss MH Wang YZ Kiehn M Weber A 《American journal of botany》2009,96(5):989-1010
The 'didymocarpoid Gesneriaceae' (traditional subfam. Cyrtandroideae excluding Epithemateae) are the largest group of Old World Gesneriaceae, comprising 85 genera and 1800 species. We attempt to resolve their hitherto poorly understood generic relationships using three molecular markers on 145 species, of which 128 belong to didymocarpoid Gesneriaceae. Our analyses demonstrate that consistent topological relationships can be retrieved from data sets with missing data using subsamples and different combinations of gene sequences. We show that all available classifications in Old World Gesneriaceae are artificial and do not reflect natural relationships. At the base of the didymocarpoids are grades of clades comprising isolated genera and small groups from Asia and Europe. These are followed by a clade comprising the African and Madagascan genera. The remaining clades represent the advanced Asiatic and Malesian genera. They include a major group with mostly twisted capsules. The much larger group of remaining genera comprises exclusively genera with straight capsules and the huge genus Cyrtandra with indehiscent fruits. Several genera such as Briggsia, Henckelia, and Chirita are not monophyletic; Chirita is even distributed throughout five clades. This degree of incongruence between molecular phylogenies, traditional classifications, and generic delimitations indicates the problems with classifications based on, sometimes a single, morphological characters. 相似文献
75.
Stavros Garantziotis Zhuowei Li Erin N. Potts Koji Kimata Lisheng Zhuo Daniel L. Morgan Rashmin C. Savani Paul W. Noble W. Michael Foster David A. Schwartz John W. Hollingsworth 《The Journal of biological chemistry》2009,284(17):11309-11317
Ozone is a common urban environmental air pollutant and significantly
contributes to hospitalizations for respiratory illness. The mechanisms, which
regulate ozone-induced bronchoconstriction, remain poorly understood.
Hyaluronan was recently shown to play a central role in the response to
noninfectious lung injury. Therefore, we hypothesized that hyaluronan
contributes to airway hyperreactivity (AHR) after exposure to ambient ozone.
Using an established model of ozone-induced airways disease, we characterized
the role of hyaluronan in airway hyperresponsiveness. The role of hyaluronan
in response to ozone was determined by using therapeutic blockade, genetically
modified animals, and direct challenge to hyaluronan. Ozone-exposed mice
demonstrate enhanced AHR associated with elevated hyaluronan levels in the
lavage fluid. Mice deficient in either CD44 (the major receptor for
hyaluronan) or inter-α-trypsin inhibitor (molecule that facilitates
hyaluronan binding) show similar elevations in hyaluronan but are protected
from ozone-induced AHR. Mice pretreated with hyaluronan-binding peptide are
protected from the development of ozone-induced AHR. Overexpression of
hyaluronan enhances the airway response to ozone. Intratracheal instillation
of endotoxin-free low molecular weight hyaluronan induces AHR dependent on
CD44, whereas instillation of high molecular weight hyaluronan protects
against ozone-induced AHR. In conclusion, we demonstrate that hyaluronan
mediates ozone-induced AHR, which is dependent on the fragment size and both
CD44 and inter-α-trypsin inhibitor. These data support the conclusion
that pulmonary matrix can contribute to the development of airway
hyperresponsiveness.Ozone is a commonly encountered urban air pollutant that significantly
contributes to increased morbidity
(1–4)
and can lead to a significant economic burden. It has been estimated that each
year inhalation of ambient ozone contributes to 800 premature deaths, 4,500
hospital admissions, 900,000 school absences, and more than 1 million
restricted activity days with an estimated $5 billion annual economic burden
(5). Population-based studies
suggest that for each 10 ppb increase in 1-h daily maximum level of ozone
there is an increase in mortality risk of 0.39–0.87%, especially in
individuals with pre-existing respiratory disease
(2,
3,
6,
7). However, the biological
mechanisms, which regulate the response to ambient ozone exposure, remain
poorly understood.Hyaluronan is an abundant extracellular matrix component, which has been
recently shown to play a significant role in the response to noninfectious
lung injury. Short fragment hyaluronan
(sHA)2 is released in
the lung after sterile injury such as bleomycin instillation
(8) or high tidal volume
ventilation (9) and can modify
the tissue response to injury. Furthermore, hyaluronan has been identified in
airway secretions from asthmatics
(10), and high molecular
weight hyaluronan can attenuate the bronchoconstrictive response in
exercise-induced asthma (11).
We therefore hypothesized that hyaluronan may contribute to the biological
response to airway injury after exposure to ozone.In this study, we provide evidence that hyaluronan mediates ozone-induced
AHR. Mice exposed to ozone demonstrate elevated lung lavage fluid levels of
hyaluronan, which is of low molecular weight. We observed that animals
deficient in either CD44 (a hyaluronan surface receptor) or
inter-α-trypsin inhibitor (IaI, which facilitates hyaluronan binding)
are protected from ozone-induced AHR. Overexpression of hyaluronan by airway
epithelia enhances ozone-induced AHR. Furthermore, pretreatment of mice with
hyaluronan-binding peptide or high molecular weight hyaluronan protects
animals from the development of ozone-induced AHR. Direct instillation of low
molecular weight, but not high molecular weight, hyaluronan alone induces AHR.
Our observations support a critical role for short fragment hyaluronan in the
development of airway hyperresponsiveness after exposure to ozone. 相似文献
76.
Selecting barcoding loci for plants: evaluation of seven candidate loci with species-level sampling in three divergent groups of land plants 总被引:3,自引:0,他引:3
Hollingsworth ML Andra Clark A Forrest LL Richardson J Pennington RT Long DG Cowan R Chase MW Gaudeul M Hollingsworth PM 《Molecular ecology resources》2009,9(2):439-457
There has been considerable debate, but little consensus regarding locus choice for DNA barcoding land plants. This is partly attributable to a shortage of comparable data from all proposed candidate loci on a common set of samples. In this study, we evaluated the seven main candidate plastid regions (rpoC1, rpoB, rbcL, matK, trnH‐psbA, atpF‐atpH, psbK‐psbI) in three divergent groups of land plants [Inga (angiosperm); Araucaria (gymnosperm); Asterella s.l. (liverwort)]. Across these groups, no single locus showed high levels of universality and resolvability. Interspecific sharing of sequences from individual loci was common. However, when multiple loci were combined, fewer barcodes were shared among species. Evaluation of the performance of previously published suggestions of particular multilocus barcode combinations showed broadly equivalent performance. Minor improvements on these were obtained by various new three‐locus combinations involving rpoC1, rbcL, matK and trnH‐psbA, but no single combination clearly outperformed all others. In terms of absolute discriminatory power, promising results occurred in liverworts (e.g. c. 90% species discrimination based on rbcL alone). However, Inga (rapid radiation) and Araucaria (slow rates of substitution) represent challenging groups for DNA barcoding, and their corresponding levels of species discrimination reflect this (upper estimate of species discrimination = 69% in Inga and only 32% in Araucaria; mean = 60% averaging all three groups). 相似文献
77.
Cantuti-Castelvetri I Hernandez LF Keller-McGandy CE Kett LR Landy A Hollingsworth ZR Saka E Crittenden JR Nillni EA Young AB Standaert DG Graybiel AM 《PloS one》2010,5(11):e13861
Background
Dyskinesias associated with involuntary movements and painful muscle contractions are a common and severe complication of standard levodopa (L-DOPA, L-3,4-dihydroxyphenylalanine) therapy for Parkinson''s disease. Pathologic neuroplasticity leading to hyper-responsive dopamine receptor signaling in the sensorimotor striatum is thought to underlie this currently untreatable condition.Methodology/Principal Findings
Quantitative real-time polymerase chain reaction (PCR) was employed to evaluate the molecular changes associated with L-DOPA-induced dyskinesias in Parkinson''s disease. With this technique, we determined that thyrotropin releasing hormone (TRH) was greatly increased in the dopamine-depleted striatum of hemi-parkinsonian rats that developed abnormal movements in response to L-DOPA therapy, relative to the levels measured in the contralateral non-dopamine-depleted striatum, and in the striatum of non-dyskinetic control rats. ProTRH immunostaining suggested that TRH peptide levels were almost absent in the dopamine-depleted striatum of control rats that did not develop dyskinesias, but in the dyskinetic rats, proTRH immunostaining was dramatically up-regulated in the striatum, particularly in the sensorimotor striatum. This up-regulation of TRH peptide affected striatal medium spiny neurons of both the direct and indirect pathways, as well as neurons in striosomes.Conclusions/Significance
TRH is not known to be a key striatal neuromodulator, but intrastriatal injection of TRH in experimental animals can induce abnormal movements, apparently through increasing dopamine release. Our finding of a dramatic and selective up-regulation of TRH expression in the sensorimotor striatum of dyskinetic rat models suggests a TRH-mediated regulatory mechanism that may underlie the pathologic neuroplasticity driving dopamine hyper-responsivity in Parkinson''s disease. 相似文献78.
The structural rationale, synthesis and evaluation of an inhibitor designed to block glucosamine synthesis by competitively inhibiting the action of glutamine: fructose-6-phosphate amidotransferase and subsequently reducing the transformation of any glucosamine-6-phosphate formed to UDP-N-acetylglucosamine are described. The inhibitor 2-acetamido-2,6-dideoxy-6-sulfo-d-glucose (d-glucosamine-6-sulfonate) is an analog of glucosamine-6-phosphate in which the phosphate group in the latter is replaced with a sulfonic acid group. The inhibitor is designed to function by three different modes which together reduce UDP-N-acetylglucosamine synthesis. This reduction was confirmed by evaluating the effect of the inhibitor on bacterial cell-wall synthesis and by demonstrating that it inhibits acetylation of glucosamine-6-phosphate competitively and by acting as a surrogate substrate. Inhibition of glucosamine production or suitably activated glucosamine in bacteria leads to disruption of the peptidoglycan structure, which results in softening, bulging, deformation, fragility and lysis of the cells. These modifications were documented by scanning electron microscopy for bacteria treated with the inhibitor. They were observed for inhibitor concentrations in the 20 mg/mL range for Escherichia coli and Bacillus subtilis and the 5 mg/mL range for Rhizobium trifolii. 相似文献
79.
Roy Anderson James Truscott T. Deirdre Hollingsworth 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2014,369(1645)
A combination of methods, including mathematical model construction, demographic plus epidemiological data analysis and parameter estimation, are used to examine whether mass drug administration (MDA) alone can eliminate the transmission of soil-transmitted helminths (STHs). Numerical analyses suggest that in all but low transmission settings (as defined by the magnitude of the basic reproductive number, R0), the treatment of pre-school-aged children (pre-SAC) and school-aged children (SAC) is unlikely to drive transmission to a level where the parasites cannot persist. High levels of coverage (defined as the fraction of an age group effectively treated) are required in pre-SAC, SAC and adults, if MDA is to drive the parasite below the breakpoint under which transmission is eliminated. Long-term solutions to controlling helminth infections lie in concomitantly improving the quality of the water supply, sanitation and hygiene (WASH). MDA, however, is a very cost-effective tool in long-term control given that most drugs are donated free by the pharmaceutical industry for poor regions of the world. WASH interventions, by lowering the basic reproductive number, can facilitate the ability of MDA to interrupt transmission. 相似文献