全文获取类型
收费全文 | 110篇 |
免费 | 20篇 |
专业分类
130篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 12篇 |
2012年 | 8篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 1篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有130条查询结果,搜索用时 15 毫秒
51.
Zou J Rodriguez-Zas S Aldea M Li M Zhu J Gonzalez DO Vodkin LO DeLucia E Clough SJ 《Molecular plant-microbe interactions : MPMI》2005,18(11):1161-1174
52.
53.
Jinwon Jung In-Ja L. Byeon Maria DeLucia Leonardus M. I. Koharudin Jinwoo Ahn Angela M. Gronenborn 《The Journal of biological chemistry》2014,289(5):2577-2588
The human homolog of the yeast DNA repair protein RAD23, hHR23A, has been found previously to interact with the human immunodeficiency virus, type 1 accessory protein Vpr. hHR23A is a modular protein containing an N-terminal ubiquitin-like (UBL) domain and two ubiquitin-associated domains (UBA1 and UBA2) separated by a xeroderma pigmentosum complementation group C binding (XPCB) domain. All domains are connected by flexible linkers. hHR23A binds ubiquitinated proteins and acts as a shuttling factor to the proteasome. Here, we show that hHR23A utilizes both the UBA2 and XPCB domains to form a stable complex with Vpr, linking Vpr directly to cellular DNA repair pathways and their probable exploitation by the virus. Detailed structural mapping of the Vpr contacts on hHR23A, by NMR, revealed substantial contact surfaces on the UBA2 and XPCB domains. In addition, Vpr binding disrupts an intramolecular UBL-UBA2 interaction. We also show that Lys-48-linked di-ubiquitin, when binding to UBA1, does not release the bound Vpr from the hHR23A-Vpr complex. Instead, a ternary hHR23A·Vpr·di-UbK48 complex is formed, indicating that Vpr does not necessarily abolish hHR23A-mediated shuttling to the proteasome. 相似文献
54.
A method for quantitative analysis of spatially variable physiological processes across leaf surfaces 总被引:1,自引:0,他引:1
Many physiological processes are spatially variable across leaf surfaces. While maps of photosynthesis, stomatal conductance,
gene expression, water transport, and the production of reactive oxygen species (ROS) for individual leaves are readily obtained,
analytical methods for quantifying spatial heterogeneity and combining information gathered from the same leaf but with different
instruments are not widely used. We present a novel application of tools from the field of geographical imaging to the multivariate
analysis of physiological images. Procedures for registration and resampling, cluster analysis, and classification provide
a general framework for the analysis of spatially resolved physiological data. Two experiments were conducted to illustrate
the utility of this approach. Quantitative analysis of images of chlorophyll fluorescence and the production of ROS following
simultaneous exposure of soybean leaves to atmospheric O3 and soybean mosaic virus revealed that areas of the leaf where the operating quantum efficiency of PSII was depressed also
experienced an accumulation of ROS. This correlation suggests a causal relationship between oxidative stress and inhibition
of photosynthesis. Overlaying maps of leaf surface temperature and chlorophyll fluorescence following a photoinhibition treatment
indicated that areas with low operating quantum efficiency of PSII also experienced reduced stomatal conductance (high temperature).
While each of these experiments explored the covariance of two processes by overlaying independent images gathered with different
instruments, the same procedures can be used to analyze the covariance of information from multiple images. The application
of tools from geographic image analysis to physiological processes occurring over small spatial scales will help reveal the
mechanisms generating spatial variation across leaves. 相似文献
55.
Joao L. N. Carvalho Tara W. Hudiburg Henrique C. J. Franco Evan H. DeLucia 《Global Change Biology Bioenergy》2017,9(8):1333-1343
GHG mitigation by bioenergy crops depends on crop type, management practices, and the input of residue carbon (C) to the soil. Perennial grasses may increase soil C compared to annual crops because of more extensive root systems, but it is less clear how much soil C is derived from above‐ vs. belowground inputs. The objective of this study was to synthesize the existing knowledge regarding soil C inputs from above‐ and belowground crop residues in regions cultivated with sugarcane, corn, and miscanthus, and to predict the impact of residue removal and tillage on soil C stocks. The literature review showed that aboveground inputs to soil C (to 1‐m depth) ranged from 70% to 81% for sugarcane and corn vs. 40% for miscanthus. Modeled aboveground C inputs (to 30 cm depth) ranged from 54% to 82% for sugarcane, but were 67% for miscanthus. Because 50% of observed miscanthus belowground biomass is below 30 cm depth, it may be necessary to increase the depth of modeled soil C dynamics to reconcile modeled belowground C inputs with measured. Modeled removal of aboveground corn residue (25–100%) resulted in C stock reduction in areas of corn–corn–soybean rotation under conventional tillage, while no‐till management lessoned this impact. In sugarcane, soil C stocks were reduced when total aboveground residue was removed at one site, while partial removal of sugarcane residue did not reduce soil C stocks in either area. This study suggests that aboveground crop residues were the main C‐residue source to the soil in the current bioethanol sector (corn and sugarcane) and the indiscriminate removal of crop residues to produce cellulosic biofuels can reduce soil C stocks and reduce the environmental benefits of bioenergy. Moreover, a switch to feedstocks such as miscanthus with more allocation to belowground C could increase soil C stocks at a much faster rate. 相似文献
56.
Summary Soils derived from hydrothermally altered andesite support unique communities of Sierran conifers (Pinus ponderosa Laws. and P. jeffreyi Grev. and Balf.) amongst sagebrush (Artemisia tridentata Nutt.) vegetation in the western Great Basin. Plants grown in soil derived from hydrothermally altered bedrock had lower growth rates, total biomass, and net photosynthetic rates than plants grown in soil derived from unaltered andesite of the same formation. Total dry mass was 10 to 28% lower for conifers grown in altered soil whereas dry mass of Artemisia tridentata and Bromus tectorum L. was reduced by over 90%. Results from a nutrient amendment experiment indicated that low phosphorus was the dominant limitation in altered soil, and phosphorus-deficiency affected growth primarily by limiting leaf area development rather than direct inhibition of photosynthesis. The proportionately greater reduction of biomass for Artemisia and Bromus grown in altered soil supports our hypothesis that Great Basin vegetation is excluded from altered soil by intolerance to nutrient deficiency. The Sierran conifers growing on this rock type are therefore free of competition for water with Great Basin vegetation and are able to persist in an exceptionally dry climate. 相似文献
57.
Altered dynamics of forest recovery under a changing climate 总被引:2,自引:0,他引:2
Kristina J. Anderson‐Teixeira Adam D. Miller Jacqueline E. Mohan Tara W. Hudiburg Benjamin D. Duval Evan H. DeLucia 《Global Change Biology》2013,19(7):2001-2021
Forest regeneration following disturbance is a key ecological process, influencing forest structure and function, species assemblages, and ecosystem–climate interactions. Climate change may alter forest recovery dynamics or even prevent recovery, triggering feedbacks to the climate system, altering regional biodiversity, and affecting the ecosystem services provided by forests. Multiple lines of evidence – including global‐scale patterns in forest recovery dynamics; forest responses to experimental manipulation of CO2, temperature, and precipitation; forest responses to the climate change that has already occurred; ecological theory; and ecosystem and earth system models – all indicate that the dynamics of forest recovery are sensitive to climate. However, synthetic understanding of how atmospheric CO2 and climate shape trajectories of forest recovery is lacking. Here, we review these separate lines of evidence, which together demonstrate that the dynamics of forest recovery are being impacted by increasing atmospheric CO2 and changing climate. Rates of forest recovery generally increase with CO2, temperature, and water availability. Drought reduces growth and live biomass in forests of all ages, having a particularly strong effect on seedling recruitment and survival. Responses of individual trees and whole‐forest ecosystems to CO2 and climate manipulations often vary by age, implying that forests of different ages will respond differently to climate change. Furthermore, species within a community typically exhibit differential responses to CO2 and climate, and altered community dynamics can have important consequences for ecosystem function. Age‐ and species‐dependent responses provide a mechanism by which climate change may push some forests past critical thresholds such that they fail to recover to their previous state following disturbance. Altered dynamics of forest recovery will result in positive and negative feedbacks to climate change. Future research on this topic and corresponding improvements to earth system models will be a key to understanding the future of forests and their feedbacks to the climate system. 相似文献
58.
In an isolated population of Drosophila melanogaster on Ishigaki Island the
chromosomal distribution of several retrotransposons, including copia, 412,
297, 17.6, I, and jockey elements, was examined by in situ hybridization.
In this population the cosmopolitan inversion, In(2L)t, is known to exist
in high frequency. One major haplotype concerning the occupied sites of the
transposable elements was identified in the In(2L)t-carrying chromosomes.
This haplotype is suggested to be the ancestral one. The age of the
inversion in this local population was estimated to be 1,400 generations.
The transposition rates of these elements were estimated based on the age
of the inversion and the number of the elements lost and gained. The
excision rates were in the range from 9.13 x 10(-5) to 2.25 x 10(-4) per
site per generation. They were similar each other in the copia-like
elements as well as in the LINE-like elements. The rate was higher in the
copia-like elements than in the LINE-like elements. Insertions occurred in
the range from 6.79 x 10(-4) to 9.05 x 10(-4) per element per generation.
It is herein shown that both insertions and excisions occurred at a
significantly higher rate in this population than in the laboratory.
相似文献
59.
Contribution of photosynthetic rate to growth and reproduction in Amaranthus hybridus 总被引:1,自引:0,他引:1
While it is known that genetic variation for photosynthetic and growth traits exists in natural populations, the functional
significance of this variation remains unclear, particularly for photosynthetic traits. To test the hypothesis that photosynthetic
rate has direct effects on reproduction as well as contributing indirectly to reproduction through effects on growth, we compared
wild-type Amaranthus hybridus families to those with a single gene mutation that confers a lower photosynthetic rate. Wild-type and photosynthetic-mutant
families were grown in competitive and non-competitive environments and we compared size, biomass allocation, architecture,
and reproduction at three developmental stages. To assess the contributions of individual growth traits to reproduction, we
calculated covariances between standardized traits and relative fitness (selection differentials), and compared selection
between the two biotypes. Finally, we used path analysis to calculate the indirect effects of photosynthetic rate on fitness
through growth. The size, allocation, and architecture of photosynthetic mutants did not differ from those of the wild type
in either the competitive or non-competitive environment, with the exception that they were taller by the last developmental
stage. However, the reproductive biomass of the photosynthetic mutants was significantly reduced compared to the wild type.
In the competitive environment, the wild type achieved greater fitness because, while similar in size to the mutants, at any
given size it produced more reproductive biomass. This suggests that photosynthetic rate affected the linkage between plant
size and reproduction and is evidence of an indirect contribution to fitness. In the non-competitive environment, there were
fewer differences in selection differentials between the two plant genotypes, suggesting fewer indirect effects. Path analysis
showed that variation in photosynthetic biotype had indirect effects on reproductive biomass, via growth traits, and that
there were no direct effects. Photosynthetic rate appears to have fitness consequences primarily through multiple contributions
to growth throughout development.
Received: 27 March 1998 / Accepted: 28 August 1998 相似文献
60.
Human-induced increases in atmospheric CO2 concentration have the potential to alter the chemical composition of plant tissue, and thereby affect the amount of tissue consumed by herbivorous arthropods. At the Duke Forest free-air concentration enrichment (FACE) facility in North Carolina (FACTS–1 research facility), we measured the amount of leaf tissue damaged by insects and other herbivorous arthropods during two growing seasons in a deciduous forest understory continuously exposed to ambient (360 l l–1) and elevated (~560 µl l–1) CO2 conditions. In 1999, there was a significant interaction between CO2 and species such that winged elm (Ulmus alata) showed lower herbivory in elevated CO2 plots, whereas red maple (Acer rubra) and sweetgum (Liquidambar styraciflua) did not. In 2000, our results did not achieve statistical significance but the magnitude of the result was consistent with the 1999 results. In 1999 and 2000, we found a decline (10–46%) in community-level herbivory in elevated CO2 plots driven primarily by reductions in herbivory on elm. The major contribution to total leaf damage was from missing tissue (66% of the damaged tissue), with galls, skeletonized, and discolored tissue making smaller contributions. It is unclear whether the decline in leaf damage is a result of altered insect populations, altered feeding, or a combination. We were not able to quantify insect populations, and our measurements did not resolve an effect of elevated CO2 on leaf chemical composition (total nitrogen, carbon, C/N, sugars, phenolics, starch). Despite predictions from a large number of single-species studies that herbivory may increase under elevated CO2, we have found a decrease in herbivory in a naturally established forest understory exposed to a full suite of insect herbivores and their predators. 相似文献