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381.
Digenean trematodes are common and abundant in aquatic habitats and their free-living larvae, the cercariae, have recently been recognized as important components of ecosystems in terms of comprising a significant proportion of biomass and in having a potentially strong influence on food web dynamics. One strategy to enhance their transmission success is to produce high numbers of cercariae which are available during the activity peak of the next host. In laboratory experiments with 13 Lymnaea stagnalis snails infected with Trichobilharzia szidati the average daily emergence rate per snail was determined as 2,621 cercariae, with a maximum of 29,560. During a snail’s lifetime this summed up to a mass equivalent of or even exceeding the snail’s own body mass. Extrapolated for the eutrophic pond where the snails were collected, annual T. szidati biomass may reach 4.65 tons, a value equivalent to a large Asian elephant. Emission peaks were observed after the onset of illumination, indicating emission synchronizing with the high morning activities of the definitive hosts, ducks. However, high cercarial emission is possible throughout the day under favorable lightning conditions. Therefore, although bird schistosomes, such as T. szidati constitute only a fraction of the diverse trematode communities in the studied aquatic ecosystem, their cercariae can still pose a considerable risk for humans of getting cercarial dermatitis (swimmer''s itch) due to the high number of cercariae emitted from infected snails. 相似文献
382.
383.
Árvay Július Šnirc Marek Hauptvogl Martin Bilčíková Jana Bobková Alica Demková Lenka Hudáček Marek Hrstková Miroslava Lošák Tomáš Král Martin Kováčik Anton Štefániková Jana 《Biological trace element research》2019,190(1):226-233
Biological Trace Element Research - The aim of the present study was to determine concentrations of 15 macro- and micro-elements in 10 commercially available plantation Arabica coffee brands. The... 相似文献
384.
In dieser Arbeit wurden allelopathische Eigenschaften von Roggen, Weizen, Gerste und Hafer studiert, die sich bei gegenseitigen Beziehungen dieser Getreidearten geltend machen können. Als Beweis für die Wurzelbeeinflussung der angeführten Getreidearten wurde eine Methode verwendet, bei der die erwähnten Getreidearten in derselben Kultivierungserde wuchsen, und zwar teils unmittelbar nacheinander, teils in abgestuften Zeitintervallen nacheinander mit verschiedenlanger Lagerungszeit der Erde. Die Versuchsergebnisse haben die Ansichten zahlreicher Verfasser bestätigt, die behaupten, dass die angegebenen Getreidearten allelopathish aktiv sind. Roggen, Weizen und Hafer beeinflussten signifikant das Wachstum der nachfolgenden Kulturen; dabei erwiesen die Ergebnisse nicht deutlich jene Beeinflussung, die durch das Erschöpfen der Nährstoffe durch die vorhergehende Pflanze bedingt worden wäre. Die angewandte Methode einer nachfolgenden Kultivierung erwies sich geeignet als Beweis für die allelopathischen Eigenschaften der Pflanzen unter natürlichen Bodenbedingungen. Die erwähnte Methode lässt sich vorteilhaft insbesondere in jenen Fällen anwenden, bei denen der Unterschied im Habitus der oberirdischen Teile der Pflanzenarten das Studium des Charakters ihrer gegenseitigen Beziehungen bei gemeinsamem Wachstum unmöglich macht. Diese Methode könnte ebenfalls eine Anwendung in der landwirtschaftlichen Praxis finden, wenn eine geeignete Zeitfolge der Pflanzen bei der unmittelbare Reihenfolge auf demselben Standort ermittelt werden soll. 相似文献
385.
Jiří Kamler Miloslav Homolka Radim Cerkal Marta Heroldová Jarmila Krojerová-Prokešová Miroslava Barančeková Jan Dvořák Karel Vejražka 《European Journal of Wildlife Research》2009,55(6):583-588
Large herbivores are the key species for game management in the Central Europe. Analyses of factors affecting the feeding
behaviour of herbivores and consequences of their browsing are therefore highly important both for farmers and for game managers
as the protective measurements should be focused on the most threatened fields. The influence of fallow (Dama dama) and roe deer (Capreolus capreolus) browsing during vegetation period on sunflower production was studied. The experiment was carried out in 2006 on a field
located near a forest complex. We marked out pairs of paired permanent plots and monitored deer impact regularly from the
emergence of plants until the harvest. Herbivores damaged the sunflower intensively immediately after the emergence at the
height of 1 to 2 cm above the ground. When the plants had reached approximately 15-40 cm in height, deer browsed the top shoots
and as the plants grew higher the browsing was restricted to leaves or to substitute stems of the previously browsed plants.
Sunflower ceased to attract big herbivores in flowering stage. Browsing significantly affected the yield of seeds. Approximately
one half of the plants that had been damaged in early stage died as well as 12.5% of plants that had been damaged at second
term; the rest produced substitute stems. Almost 33% of the substitute stems did not form disc florets; the second third of
them formed disc florets with a diameter of 6-8 cm, and the last third set disc florets with a diameter of 8-10 cm. 相似文献
386.
The strain of Aureobasidium pullulans NRRL Y-2311 (CCY 27-1-98), known as a hyperproducer of endo-1,4-β-xylanase, exhibited good growth on pectin or pectate. Growth
on these carbon sources is associated with an inducible production of significant amounts of pectolytic enzymes, of which
exopolygalacturonase (EC 3.2.1.67) and endopolygalacturonase (EC 3.2.1.15) were identified. The two enzymes are not produced
on D-glucose or under carbon starvation conditions. The enzymes can be induced in glucose-grown cells by D-galacturonic acid
and its oligomers. Thus, D-galacturonic acid, the monomer derived from the polysaccharide, appears to be the natural inducer
or a precursor of an inducer of pectolytic enzymes in the studied yeast.
Received: 4 November 1995 / Accepted: 11 December 1995 相似文献