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331.
332.
Adam R Burns W Zac Stephens Keaton Stagaman Sandi Wong John F Rawls Karen Guillemin Brendan JM Bohannan 《The ISME journal》2016,10(3):655-664
Despite their importance to host health and development, the communities of microorganisms associated with humans and other animals are characterized by a large degree of unexplained variation across individual hosts. The processes that drive such inter-individual variation are not well understood. To address this, we surveyed the microbial communities associated with the intestine of the zebrafish, Danio rerio, over developmental time. We compared our observations of community composition and distribution across hosts with that predicted by a neutral assembly model, which assumes that community assembly is driven solely by chance and dispersal. We found that as hosts develop from larvae to adults, the fit of the model to observed microbial distributions decreases, suggesting that the relative importance of non-neutral processes, such as microbe-microbe interactions, active dispersal, or selection by the host, increases as hosts mature. We also observed that taxa which depart in their distributions from the neutral prediction form ecologically distinct sub-groups, which are phylogenetically clustered with respect to the full metacommunity. These results demonstrate that neutral processes are sufficient to generate substantial variation in microbiota composition across individual hosts, and suggest that potentially unique or important taxa may be identified by their divergence from neutral distributions. 相似文献
333.
We sampled populations of forest-floor dwelling cave and ground wētā using footprint tracking tunnels and spotlight transect counts in southern beech forest, New Zealand. Samples were compared to estimates of wētā density based on mark–recapture estimates from 25?m2 enclosures. Both activity indices captured variability in cave wētā in time and space, were strongly correlated with each other, and have the potential for monitoring cave wētā activity levels. Comparisons between indices and cave wētā density estimates were equivocal, as recapture rates were too low to calculate high-resolution density estimates. We also found that cave wētā counts had a curved relationship increasing with temperature, and a negative relationship with increasing shrub and woody debris cover. Based on these preliminary results, tracking tunnels could be a viable method of monitoring cave wētā as they appear more efficient than transect counts and are relatively inexpensive. However, further calibration trials are needed to determine if indices mirror robust population density estimates. 相似文献
334.
335.
Microbial planktonic communities (i.e. bacteria and protozoa),
phytoplankton, dissolved organic carbon (DOC) and particulate organic
carbon (POC) were seasonally examined at Medes Islands (Northwestern
Mediterranean) to assess their variation in abundance and composition
throughout the year in a near-bottom littoral ecosystem. From October 1995
to November 1996, samples were collected between two and six times per
month at 0.5 m above the bottom. Mean DOC and POC values throughout the
year were 2560 180 (SE) and 387
± 35 g C
l-1, respectively. All year, detrital organic carbon
(detrital=total POC - live carbon) represented the main POC fraction, and
mean live carbon was 24 ± 9 g C
l-1. Winter and spring had maximum values of POC,
and spring and summer had maximum values of DOC. Heterotrophic bacteria,
with a mean abundance of 5.16 ± 0.08 x
105 cells ml-1, were the main
contributor to live carbon (26 ± 7%). During winter,
heterotrophic bacterial biomass decreased 40% due to a decrease in mean
biovolume per cell. Synechococcus sp. and
Prochlorococcus sp. abundance were 2.24 ±
0.09 x 104 and 1.05 ± 0.07 x
104 cells ml-1, respectively.
However, while Synechococcus sp. were present all
year, Prochlorococcus sp. were not observed from April
to July. Mean phytoplankton (i.e. diatoms and dinoflagellates) abundance
was 2.06 ± 0.40 x 104 cells
l-1 with biomass at a maximum during the winter
months, the period with the lowest temperature and the highest nutrient
concentration. The size composition of live carbon showed two clearly
distinct periods: from December to March, live carbon was dominated in
biomass by microplankton, while from April to November, pico- and
nanoplankton cells were dominant. Overall, the dynamics of the near-bottom
planktonic communities was characterized by a low biomass of heterotrophic
and autotrophic bacteria, phytoplankton and ciliates in contrast to
previous water column studies. This pattern and the high temporal
heterogeneity of the different planktonic communities are discussed in
relation to the physical and chemical characteristics of the environment,
as well as to the potential role that benthic communities may be exerting
in the control of the near-bottom planktonic communities.
相似文献
336.
Grupstra Carsten G. B. Coma Rafel Ribes Marta Leydet Karine Posbic Parkinson John Everett McDonald Kelly Catllà Marc Voolstra Christian R. Hellberg Michael E. Coffroth Mary Alice 《Coral reefs (Online)》2017,36(3):981-985
Coral Reefs - Zooxanthellate corals are threatened by climate change but may be able to escape increasing temperatures by colonizing higher latitudes. To determine the effect of host range... 相似文献
337.
338.
Marco J Koudijs Marjo J den Broeder Evelyn Groot Fredericus JM van Eeden 《BMC developmental biology》2008,8(1):15
Background
Aberrant activation of the Hedgehog (Hh) signaling pathway in different organisms has shown the importance of this family of morphogens during development. Genetic screens in zebrafish have assigned specific roles for Hh in proliferation, differentiation and patterning, but mainly as a result of a loss of its activity. We attempted to fully activate the Hh pathway by removing both receptors for the Hh proteins, called Patched1 and 2, which are functioning as negative regulators in this pathway. 相似文献339.
340.
High activity of human butyrylcholinesterase at low pH in the presence of excess butyrylthiocholine.
Patrick Masson Florian Nachon Cynthia F Bartels Marie-Therese Froment Fabien Ribes Cedric Matthews Oksana Lockridge 《European journal of biochemistry》2003,270(2):315-324
Butyrylcholinesterase is a serine esterase, closely related to acetylcholinesterase. Both enzymes employ a catalytic triad mechanism for catalysis, similar to that used by serine proteases such as alpha-chymotrypsin. Enzymes of this type are generally considered to be inactive at pH values below 5, because the histidine member of the catalytic triad becomes protonated. We have found that butyrylcholinesterase retains activity at pH 相似文献