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871.
Justin A. Meeds J. Marty Kranabetter Ieva Zigg Dave Dunn Franois Miros Paul Shipley Melanie D. Jones 《The ISME journal》2021,15(5):1478
Ectomycorrhizal (EM) fungi can acquire phosphorus (P) through the production of extracellular hydrolytic enzymes (exoenzymes), but it is unclear as to the manner and extent native EM fungal communities respond to declining soil P availability. We examined the activity of six exoenzymes (xylosidase, N-acetyl glucosaminidase, β-glucosidase, acid phosphomonoesterase, acid phosphodiesterase [APD], laccase) from EM roots of Pseudotsuga menzesii across a soil podzolization gradient of coastal British Columbia. We found that APD activity increased fourfold in a curvilinear association with declining inorganic P. Exoenzyme activity was not related to organic P content, but at a finer resolution using 31P-NMR, there was a strong positive relationship between APD activity and the ratio of phosphodiesters to orthophosphate of surface organic horizons (forest floors). Substantial increases (two- to fivefold) in most exoenzymes were aligned with declining foliar P concentrations of P. menzesii, but responses were statistically better in relation to foliar nitrogen (N):P ratios. EM fungal species with consistently high production of key exoenzymes were exclusive to Podzol plots. Phosphorus deficiencies in relation to N limitations may provide the best predictor of exoenzyme investment, reflecting an optimal allocation strategy for EM fungi. Resource constraints contribute to species turnover and the assembly of distinct, well-adapted EM fungal communities.Subject terms: Ecology, Microbial ecology 相似文献
872.
Delille Daniel; Marty Gilles; Cansemi-Soullard Maddy; Frankignoulle Michel 《Journal of plankton research》1997,19(9):1251-1264
The significance of bacterial communities in the fluxes of carbonand energy in giant kelp beds (Macrocystis pyrifera) in KerguelenArchipelago, subantarctica, was estimated by measuring bacterioplanktonbiomass and production over diel cycles in surface seawaterslocated inside and outside of Macrocystis beds. Several physicochemicalparameters [temperature, solar radiation, tide level, dissolvedoxygen, total inorganic carbon (TCO2), partial pressure of CO2(pCO2) and dissolved organic carbon (DOC)] were simultaneouslyrecorded in order to establish possible relationships with observedchanges in bacterial parameters. Bacterial biomass and productionwere significantly higher inside the kelp bed than in the surroundingarea. Furthermore, the results showed large and clear diel variationsof all parameters measured inside the kelp bed. Changes in dissolvedoxygen, TCO2 and pCO2 paralleled those of solar radiation, andwere obviously related to the metabolic activity of the kelp.Mean cell volumes and saprophytic bacterial abundance variedover the diel cycles in the same way as photosynthetic activity,while DOC, bacterioplankton production and the frequency ofdividing cells varied in an opposite way with maximal valuesat night-time. 相似文献
873.
The effect of some environmental parameters of the redd (substrate composition, interstitial dissolved oxygen concentration) upon survival of Atlantic salmon embryos was studied in a large artificial stream channel. Batches of 3000 eyed eggs were buried 0.25 m deep in the gravel substrate of 8 different channel sections, where natural or artificial sediment deposition took place. Upon emergence, fry were captured in drift nets or by electrofishing. Survival varied from 32 to 94 % in the different sections. It was strongly affected by volume of sediment less than 10 mm in particle size and more particularly by the fraction less than 0.2 mm, the main component of natural sediment deposition. Survival was less strongly determined by oxygen concentration variations except for values less than 2 mg/l obtained in the section with highest sediment deposition. Available volume of interstitial void space appeared to be crucial for good survival during larval development. 相似文献
874.
From Metaphor to Measurement: Resilience of What to What? 总被引:17,自引:0,他引:17
Resilience is the magnitude of disturbance that can be tolerated before a socioecological system (SES) moves to a different
region of state space controlled by a different set of processes. Resilience has multiple levels of meaning: as a metaphor
related to sustainability, as a property of dynamic models, and as a measurable quantity that can be assessed in field studies
of SES. The operational indicators of resilience have, however, received little attention in the literature. To assess a system's
resilience, one must specify which system configuration and which disturbances are of interest. This paper compares resilience
properties in two contrasting SES, lake districts and rangelands, with respect to the following three general features: (a)
The ability of an SES to stay in the domain of attraction is related to slowly changing variables, or slowly changing disturbance
regimes, which control the boundaries of the domain of attraction or the frequency of events that could push the system across
the boundaries. Examples are soil phosphorus content in lake districts woody vegetation cover in rangelands, and property
rights systems that affect land use in both lake districts and rangelands. (b) The ability of an SES to self-organize is related
to the extent to which reorganization is endogenous rather than forced by external drivers. Self-organization is enhanced
by coevolved ecosystem components and the presence of social networks that facilitate innovative problem solving. (c) The
adaptive capacity of an SES is related to the existence of mechanisms for the evolution of novelty or learning. Examples include
biodiversity at multiple scales and the existence of institutions that facilitate experimentation, discovery, and innovation.
Received 20 March 2001; accepted 6 June 2001. 相似文献