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71.
Carbon use efficiency of microbial communities: stoichiometry,methodology and modelling 总被引:2,自引:0,他引:2
Robert L. Sinsabaugh Stefano Manzoni Daryl L. Moorhead Andreas Richter 《Ecology letters》2013,16(7):930-939
Carbon use efficiency (CUE) is a fundamental parameter for ecological models based on the physiology of microorganisms. CUE determines energy and material flows to higher trophic levels, conversion of plant‐produced carbon into microbial products and rates of ecosystem carbon storage. Thermodynamic calculations support a maximum CUE value of ~ 0.60 (CUE max). Kinetic and stoichiometric constraints on microbial growth suggest that CUE in multi‐resource limited natural systems should approach ~ 0.3 (CUE max/2). However, the mean CUE values reported for aquatic and terrestrial ecosystems differ by twofold (~ 0.26 vs. ~ 0.55) because the methods used to estimate CUE in aquatic and terrestrial systems generally differ and soil estimates are less likely to capture the full maintenance costs of community metabolism given the difficulty of measurements in water‐limited environments. Moreover, many simulation models lack adequate representation of energy spilling pathways and stoichiometric constraints on metabolism, which can also lead to overestimates of CUE. We recommend that broad‐scale models use a CUE value of 0.30, unless there is evidence for lower values as a result of pervasive nutrient limitations. Ecosystem models operating at finer scales should consider resource composition, stoichiometric constraints and biomass composition, as well as environmental drivers, to predict the CUE of microbial communities. 相似文献
72.
Summary L-Carnitine was obtained in 40% yield from D,L-octanoyl carnitine by enantioselective hydrolysis with a strain ofFusarium oxysporum. 相似文献
73.
Gotsman M Dusa C Nassar H Hasin Y Lotan C Rozenman Y 《International journal of cardiovascular interventions》1999,2(3):187-190
The Cutting Balloon consists of a standard balloon dilatation catheter with four microtome-sharp blades that incise the plaque and minimize arterial wall trauma. It was used in 31 patients; nine had calcified arteries, ten had non-compliant lesions, three had in-stent restenosis and nine had aorto-ostial lesions. Seventeen lesions were predilated, 28 were post-dilated and 18 required stent implantation. The procedure was very effective in aorto-ostial lesions, non-compliant lesions that were not responsive to high-pressure balloon dilatation, and was partially successful in calcified arteries. It has a very specific niche in selected lesions. 相似文献
74.
Carboncini MC Manzoni D Strambi S Bonfiglio L Andre P Rossi B 《Archives italiennes de biologie》2004,142(2):113-124
We have investigated the electromyographic (EMG) and kinematic characteristics of horizontal arm extension movements in patients affected by idiopathic cervical dystonia (ICD) as well as in normal subjects. In spite of the lack of an overt dystonic involvement of the muscles acting at upper arm level, all these patients were considerably bradykinetic. Although the degree of bradykinesia observed was comparable to that previously reported for the body segment directly affected by this patholgy (21,15,8), the EMG analysis of the agonist muscles indicated a specific pathophysiological mechanism. In particular, the recruitment of the posterior deltoid (pD) in ICD patients was severely impaired within the initial phase (130 ms) of the movement. On the other hand, within the same time span, the activation of the mD, a muscle that plays a more important postural role than the pD, was not significantly different between patients and normal subjects. This reduced recruitment in the initial phase of the AG1 appears responsible of the slowness of voluntary movements. 相似文献
75.
76.
Lucotte GL;French MS Consortium 《Genetic counseling (Geneva, Switzerland)》2002,13(2):133-138
To identify the chromosomal localizations of the multiple sclerosis (MS) genes, we conducted a genomewide linkage analysis using eighteen affected families. A MS gene is linked to markers located in the 19q13.3 region (multipoint lod-score = 2.1). Apolipoprotein E (ApoE) gene, located in this region, is an excellent candidate gene for MS because the ApoEe4 allele is acting as a severity allele in the disease. 相似文献
77.
78.
Substitution bias, rapid saturation, and the use of mtDNA for nematode systematics 总被引:13,自引:0,他引:13
Only relatively recently have researchers turned to molecular methods for
nematode phylogeny reconstruction. Thus, we lack the extensive literature
on evolutionary patterns and phylogenetic usefulness of different DNA
regions for nematodes that exists for other taxa. Here, we examine the
usefulness of mtDNA for nematode phylogeny reconstruction and provide data
that can be used for a priori character weighting or for parameter
specification in models of sequence evolution. We estimated the
substitution pattern for the mitochondrial ND4 gene from intraspecific
comparisons in four species of parasitic nematodes from the family
Trichostrongylidae (38-50 sequences per species). The resulting pattern
suggests a strong mutational bias toward A and T, and a lower
transition/transversion ratio than is typically observed in other taxa. We
also present information on the relative rates of substitution at first,
second, and third codon positions and on relative rates of saturation of
different types of substitutions in comparisons ranging from intraspecific
to interordinal. Silent sites saturate extremely quickly, presumably owing
to the substitution bias and, perhaps, to an accelerated mutation rate.
Results emphasize the importance of using only the most closely related
sequences in order to infer patterns of substitution accurately for
nematodes or for other taxa having strongly composition-biased DNA. ND4
also shows high amino acid polymorphism at both the intra- and
interspecific levels, and in higher level comparisons, there is evidence of
saturation at variable amino acid sites. In general, we recommend using
mtDNA coding genes only for phylogenetics of relatively closely related
nematode species and, even then, using only nonsynonymous substitutions and
the more conserved mitochondrial genes (e.g., cytochrome oxidases). On the
other hand, the high substitution rate in genes such as ND4 should make
them excellent for population genetics studies, identifying cryptic
species, and resolving relationships among closely related congeners when
other markers show insufficient variation.
相似文献
79.
Differentiation-associated modulation of heparan sulfate structure and function in CaCo-2 colon carcinoma cells 总被引:3,自引:2,他引:1
Salmivirta M; Safaiyan F; Prydz K; Andresen MS; Aryan M; Kolset SO 《Glycobiology》1998,8(10):1029-1036
Heparan sulfate species expressed by different cell and tissue types differ
in their structural and functional properties. Limited information is
available on differences in regulation of heparan sulfate biosynthesis
within a single tissue or cell population under different conditions. We
have approached this question by studying the effect of cell
differentiation on the biosynthesis and function of heparan sulfate in
human colon carcinoma cells (CaCo-2). These cells undergo spontaneous
differentiation in culture when grown on semipermeable supports; the
differentiated cells show phenotypic similarity to small intestine
enterocytes. Metabolically labeled heparan sulfate was isolated from the
apical and basolateral media from cultures of differentiated and
undifferentiated cells. Compositional analysis of disaccharides, derived
from the contiguous N-sulfated regions of heparan sulfate, indicated a
greater proportion of 2-O- sulfated iduronic acid units and a smaller
amount of 6-O-sulfated glucosamine units in differentiated than in
undifferentiated cells. By contrast, the overall degree of sulfation, the
chain length and the size distribution of the N-acetylated regions were
similar regardless the differentiation status of the cells. The structural
changes were found to affect the binding of heparan sulfate to the long
isoform of platelet-derived growth factor A chain but not to fibroblast
growth factor 2. These findings show that heparan sulfate structures change
during cell differentiation and that heparan sulfate-growth factor
interactions may be affected by such changes.
相似文献
80.
Kemmer D Huang Y Shah SP Lim J Brumm J Yuen MM Ling J Xu T Wasserman WW Ouellette BF 《Genome biology》2005,6(12):R106
We developed Ulysses as a user-oriented system that uses a process called Interolog Analysis for the parallel analysis and
display of protein interactions detected in various species. Ulysses was designed to perform such Interolog Analysis by the
projection of model organism interaction data onto homologous human proteins, and thus serves as an accelerator for the analysis
of uncharacterized human proteins. The relevance of projections was assessed and validated against published reference collections.
All source code is freely available, and the Ulysses system can be accessed via a web interface . 相似文献