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91.
Lactobacillus reuteri is both a gut symbiont and a stable member of sourdough microbiota. This study employed multilocus sequence analysis and an analysis of host-specific physiological and genetic traits to assign five sourdough isolates to rodent- or human-specific lineages. Comparative genome hybridization revealed that the model sourdough isolate LTH2584 had a genome content very similar to that of the model rodent isolate 100-23. These results demonstrate that sourdough isolates of L. reuteri are of intestinal origin. 相似文献
92.
Increasing land salinization in Australia is predicted to lead to severe declines in species diversity in affected areas, and perhaps significant numbers of species extinctions. Much of the diversity that will be lost consists of understorey and mid-storey species, yet the overwhelming majority of research has focussed on salinity tolerance in tree species. We investigated how the presence of a shallow, saline water table affected the understorey species composition, species richness and species diversity in two remnant Eucalyptus wandoo Blakely woodlands in the Western Australian wheatbelt. Species richness and species diversity were significantly lower in areas with a shallow water table at elevations < 0.5 m above the lowest local elevation, compared with both higher elevations and with areas of low elevation without a shallow water table. Species composition (Bray-Curtis similarities) was also significantly different in low elevation, saline areas. At one site, saline areas were colonized by native and alien species that were not present in the surrounding vegetation, yet the community that has developed does not contain either the species or structural diversity of the surrounding system. At the other site, no colonisation of saline areas by new species occurred. Even though small differences in elevation (< 0.5 m) at our study sites were important in moderating the impacts of salinity in areas with a shallow water table, the loss of species diversity, species richness and structural complexity in low-lying elevations indicated that the ecological risk from secondary salinity to species associated only with drainage lines, seasonally wet flats and other low-lying areas is severe. The priority is to identify those vegetation communities that are restricted to only low relative elevations within the landscape and that only occur in remnants predicted to be at a high risk of developing a shallow and saline water table. 相似文献
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Stuart David Greenhill Sophie Elizabeth Lyn Chamberlain Alex Lench Peter Vernon Massey Kathryn Heather Yuill Gavin Lawrence Woodhall Roland Spencer Gwynne Jones 《PloS one》2014,9(1)
The entorhinal cortex (EC) controls hippocampal input and output, playing major roles in memory and spatial navigation. Different layers of the EC subserve different functions and a number of studies have compared properties of neurones across layers. We have studied synaptic inhibition and excitation in EC neurones, and we have previously compared spontaneous synaptic release of glutamate and GABA using patch clamp recordings of synaptic currents in principal neurones of layers II (L2) and V (L5). Here, we add comparative studies in layer III (L3). Such studies essentially look at neuronal activity from a presynaptic viewpoint. To correlate this with the postsynaptic consequences of spontaneous transmitter release, we have determined global postsynaptic conductances mediated by the two transmitters, using a method to estimate conductances from membrane potential fluctuations. We have previously presented some of this data for L3 and now extend to L2 and L5. Inhibition dominates excitation in all layers but the ratio follows a clear rank order (highest to lowest) of L2>L3>L5. The variance of the background conductances was markedly higher for excitation and inhibition in L2 compared to L3 or L5. We also show that induction of synchronized network epileptiform activity by blockade of GABA inhibition reveals a relative reluctance of L2 to participate in such activity. This was associated with maintenance of a dominant background inhibition in L2, whereas in L3 and L5 the absolute level of inhibition fell below that of excitation, coincident with the appearance of synchronized discharges. Further experiments identified potential roles for competition for bicuculline by ambient GABA at the GABAA receptor, and strychnine-sensitive glycine receptors in residual inhibition in L2. We discuss our results in terms of control of excitability in neuronal subpopulations of EC neurones and what these may suggest for their functional roles. 相似文献
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97.
Altered photosynthesis,flowering, and fruiting in transgenic tomato plants that have an increased capacity for sucrose synthesis 总被引:2,自引:0,他引:2
Barry J. Micallef Kirk A. Haskins Peter J. Vanderveer Kwang-Soo Roh Christine K. Shewmaker Thomas D. Sharkey 《Planta》1995,196(2):327-334
Photosynthesis, leaf assimilate partitioning, flowering, and fruiting were examined in two lines of Lycopersicon esculentum Mill. transformed with a gene coding for sucrose-phosphate synthase (SPS) (EC 2.3.1.14) from Zea mays L. expressed from a tobacco ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit promoter. Plants were grown at either 35 or 65 Pa CO2 and high light (1000 mol photons·m–2·s–1). Limiting and maximum SPS activities were significantly greater (up to 12 times) in the leaves of SPS-transformed lines for all treatments. Partitioning of carbon into sucrose increased 50% for the SPS transformants. Intact leaves of the control lines exhibited CO2-insensitivity of photosynthesis at high CO2 levels, whereas the SPS transformants did not exhibit CO2-insensitivity. The O2-sensitivity of photosynthesis was also greater for the SPS-transformed lines compared to the untransformed control when measured at 65 Pa CO2. These data indicate that the SPS transformants had a reduced limitation on photosynthesis imposed by end-product synthesis. Growth at 65 Pa CO2 resulted in reduced photosynthetic capacity for control lines but not for SPS-transformed lines. When grown at 65 Pa CO2, SPS transformed lines had a 20% greater photosynthetic rate than controls when measured at 65 Pa CO2 and a 35% greater rate when measured at 105 Pa CO2. Photosynthetic rates were not different between lines when grown at 35 Pa CO2. The time to 50% blossoming was reduced and the total number of inflorescences was significantly greater for the SPS transformants when grown at either 35 or 65 Pa CO2. At 35 Pa CO2, the total fruit number of the SPS transformants was up to 1.5 times that of the controls, the fruit matured earlier, and there was up to a 32% increase in total fruit dry weight. Fruit yield was not significantly different between the lines when grown at 65 Pa CO2. Therefore, there was not a strict relationship between yield and leaf photosynthesis rate. Flowering and fruit development of the SPS-transformed lines grown at 35 Pa CO2 showed similar trends to the controls grown at 65 Pa CO2. Incidences of blossom-end rot were also reduced in the SPS-transformed lines. These data indicate that altering starch/sucrose partitioning by increasing the capacity for sucrose synthesis can affect acclimation to elevated CO2 partial pressure and flowering and fruiting in tomato.Abbreviations DAS
days after seeding
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nptII
neomycin phos-photransferase
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose-1,5-bisphosphate
- SPS
sucrose-phosphate synthase
- SSU
Rubisco small subunit
This research was supported by U.S. Department of Energy grant FG02-87ER13785. B.J.M. thanks the Natural Sciences and Engineering Research Council of Canada for financial support. We are grateful to Toni A. Voelker (Calgene Inc.) for supplying tomato seeds and valuable advice. 相似文献
98.
The genus Penthorum L. consists of two species of perennial herbs, P. sedoides of eastern North America and P. chinense of eastern Asia. Penthorum has long been considered intermediate between Crassulaceae and Saxifragaceae. An anatomical study of both species was undertaken to contribute to a better understanding of the relationships of these plants. Prominent anatomical features of Penthorum include: an aerenchymatous cortex and closely-spaced collateral vascular bundles of stems; one-trace unilacunar nodes; brochidodromous venation, rosoid teeth bearing hydathodes, and anomocytic stomata of leaves; angular vessel elements with many-barred scalariform perforation plates and alternate to scattered intervascular pits; thin-walled non-septate fiber-tracheids; abundant homocellular erect uniseriate and biseriate rays; and absence of axial xylem parenchyma. In general, Penthorum possesses neither the morphological nor the anatomical synapomorphies which define Crassulaceae, and features shared with Saxifragaceae are largely symplesiomorphous. Thus Penthorum is probably best classified in the monogeneric Penthoraceae. 相似文献
99.
100.
m-Cresol has been isolated from culture filtrates of Valsa friesii. The yield after 10 days of growth on glucose-phytone broth was 160 mg/liter. 相似文献