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71.
72.
Although ecological risk assessment (ERA) and environmental monitoring would seem to be potentially complimentary activities, they have been disjunct in practice. This is because of differences in goals and products. Environmental monitoring determines status and trends in indicators to determine whether the environment is improving. ERA estimates effects of stressors on endpoint attributes to support decision making. Indicators are, by definition, indicative of some unmeasured condition. Assessment endpoints are valued properties of the environment that are susceptible to stressors of concern. Indicators are justified by the logic of the monitoring program, which may be self-referential. Assessment endpoints are justified by their potential susceptibility and by environmental policies and public values. Indicators are often expressed in terms of indices or scores that obscure the actual condition of the environment. Because assessment endpoints must be clear to decision makers and the public, they require real units of actual environmental properties. Monitoring programs are peripherally concerned about causal relationships, while risk assessment is devoted to elucidating causal relationships. As a result, risk assessments may use the results of monitoring studies, but only after disaggregating the indicators to their components and choosing those that are appropriate. Monitoring programs could be more useful if they used a risk-based approach to address important problems rather than simply tracking indicators. 相似文献
73.
Transmission of growth cone traction force through apCAM-cytoskeletal linkages is regulated by Src family tyrosine kinase activity.
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Tyrosine kinase activity is known to be important in neuronal growth cone guidance. However, underlying cellular mechanisms are largely unclear. Here, we report how Src family tyrosine kinase activity controls apCAM-mediated growth cone steering by regulating the transmission of traction forces through receptor-cytoskeletal linkages. Increased levels of tyrosine phosphorylation were detected at sites where beads coated with apCAM ligands were physically restrained to induce growth cone steering, but not at unrestrained bead binding sites. Interestingly, the rate and level of phosphotyrosine buildup near restrained beads were decreased by the myosin inhibitor 2,3-butanedione-2-monoxime, suggesting that tension promotes tyrosine kinase activation. While not affecting retrograde F-actin flow rates, genistein and the Src family selective tyrosine kinase inhibitors PP1 and PP2 strongly reduced the growth cone's ability to apply traction forces through apCAM-cytoskeletal linkages, assessed using the restrained bead interaction assay. Furthermore, increased levels of an activated Src family kinase were detected at restrained bead sites during growth cone steering events. Our results suggest a mechanism by which growth cones select pathways by sampling both the molecular nature of the substrate and its ability to withstand the application of traction forces. 相似文献
74.
Desulfonation and Degradation of the Disulfodiphenylethercarboxylates from Linear Alkyldiphenyletherdisulfonate Surfactants
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David Schleheck Melanie Lechner Ren Schnenberger Marc J.-F. Suter Alasdair M. Cook 《Applied microbiology》2003,69(2):938-944
Earlier work showed that the biodegradation of a commercial linear monoalkyldiphenyletherdisulfonate surfactant as a carbon source for microbial growth leads to the quantitative formation of corresponding disulfodiphenylether carboxylates (DSDPECs), which were not degraded. α-Proteobacterium strain DS-1 (DSM 13023) catalyzes these reactions. These DSDPECs have now been characterized by high-pressure liquid chromatography coupled via an electrospray interface to a mass spectrometer. DSDPECs were a complex mixture of compounds which indicated catabolism via ω-oxygenation and β-oxidation. DSDPECs were subject to quantitative desulfonation in bacterial cultures in which they served as sole sulfur sources for bacterial growth. On average, one sulfonate group per DSDPEC species was removed, and the organism responsible for this desulfonation was isolated and identified as Rhodococcus opacus ISO-5. The products were largely monosulfodiphenylether carboxylate-phenols (MSDPEC-phenols). MSDPEC-phenols were subject to extensive dissimilation by bacteria from activated sludge. 相似文献
75.
Multiple roles of mouse Numb in tuning developmental cell fates. 总被引:8,自引:0,他引:8
O Zilian C Saner L Hagedorn H Y Lee E S?uberli U Suter L Sommer M Aguet 《Current biology : CB》2001,11(7):494-501
BACKGROUND: Notch signaling regulates multiple differentiation processes and cell fate decisions during both invertebrate and vertebrate development. Numb encodes an intracellular protein that was shown in Drosophila to antagonize Notch signaling at binary cell fate decisions of certain cell lineages. Although overexpression experiments suggested that Numb might also antagonize some Notch activity in vertebrates, the developmental processes in which Numb is involved remained elusive. RESULTS: We generated mice with a homozygous inactivation of Numb. These mice died before embryonic day E11.5, probably because of defects in angiogenic remodeling and placental dysfunction. Mutant embryos had an open anterior neural tube and impaired neuronal differentiation within the developing cranial central nervous system (CNS). In the developing spinal cord, the number of differentiated motoneurons was reduced. Within the peripheral nervous system (PNS), ganglia of cranial sensory neurons were formed. Trunk neural crest cells migrated and differentiated into sympathetic neurons. In contrast, a selective differentiation anomaly was observed in dorsal root ganglia, where neural crest--derived progenitor cells had migrated normally to form ganglionic structures, but failed to differentiate into sensory neurons. CONCLUSIONS: Mouse Numb is involved in multiple developmental processes and required for cell fate tuning in a variety of lineages. In the nervous system, Numb is required for the generation of a large subset of neuronal lineages. The restricted requirement of Numb during neural development in the mouse suggests that in some neuronal lineages, Notch signaling may be regulated independently of Numb. 相似文献
76.
F G Gudat H K Forster F Suter R Albrecht G Krey U Dürmüller M F Girard J P Obrecht 《Virchows Archiv. B, Cell pathology including molecular pathology》1985,48(4):341-350
The reactivity of normal tonsilar cells with the monoclonal antibody anti-Y29/55 is characterized at the tissue and ultrastructural cytological level. Using an indirect immuno-alkaline phosphatase method on frozen sections the antibody labels mantle zone and germinal center lymphocytes. This staining reaction is more generalized in B-lymphocyte areas than that obtained with antibodies to IgM and IgD. By indirect immunoperoxidase staining, as well as by an indirect rosetting procedure in cell suspensions, the reactive cell population were either small resting lymphocytes or activated lymphocytes corresponding to centrocytes, centroblasts, immunoblasts and plasmoblasts; some plasma cells were also labeled. These results characterize the monoclonal antibody anti-Y29/55 as a pan-B-marker antibody, useful for labeling resting and activated peripheral B-lymphocytes in frozen tissue sections and cell suspensions. 相似文献
77.
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79.
B E Matter U Graf S T Hu I Jaeger R Racine W Suter F E Würgler 《Mutation research》1983,116(3-4):389-398
80.
Werner Suter 《Journal of Ornithology》1991,132(1):29-45
Zusammenfassung Diese Arbeit gibt einen Überblick über quantitative Angaben zum Einfluß von Wasservögeln auf Süßwasserfisch-Populationen durch Prädation. Wirtschaftliche Schäden (= Schmälerung von Fischereierträgen) kommen in der Regel nur in Teichwirtschaften vor, wo Graureiher auch bei adäquater Bewirtschaftung etwa 0,4–8 % der Produktion abschöpfen können, Kormorane unter besonderen Umständen 20–>50 %. Schätzwerte durch Teichwirte liegen häufig zu hoch, weil die gesamte Fischmortalität den Wasservögeln angelastet wird. Für Seen sind weder wirtschaftliche noch ökologische Schäden (= negativer Einfluß auf die Populationsdynamik) bekannt, auch wenn nur in wenigen Fällen die im See vorhandene Fischbiomasse ermittelt werden konnte. In jenen Beispielen schöpften die Wasservögel bei den meisten Fischarten nur wenige Prozent, im Maximum 36 % der Biomasse ab. Meistens liegt der Fischereiertrag 10–20mal höher als der Verbrauch der Wasservögel (Tab. 1). Selbst auf Seen mit hohen Kormorandichten beträgt er das 4–12fache des Verzehrs der Kormorane, wobei sogar seine jährlichen Schwankungen ein Mehrfaches des Kormoranverbrauchs ausmachen können. Wasservögel bejagen zudem häufig fischereilich uninteressante Massenarten, was sich für die Bestände kommerziell wichtiger Fische möglicherweise sogar fördernd auswirken kann. Auch für natürliche Fließgewässer deuten die quantitativen Befunde trotz etwas höheren Prädationsraten als auf Seen (Tab. 2) darauf hin, dass die Prädation durch Graureiher, Kormorane und Säger weitgehend im Bereich der kompensatorischen Mortalität auf die Fischpopulationen einwirkt. Die wenigen Hinweise auf zusätzliche (= additive) Mortalität mit Einbußen für die Fischerei stammen von stark verbauten Flüssen und Bächen. Insgesamt sind die Räuber-Beute-Beziehungen zwischen Wasservögeln und Süßwasserfischen aber ungenügend erforscht, und besonders die hervorragenden experimentellen Möglichkeiten bei Fischteichen wurden noch kaum genutzt.
Effects of piscivorous birds on freshwater fish populations — a review
Summary This paper reviews quantitative data on the effects of waterfowl predation on freshwater fish stocks. Economical damage (i. e. reduction of the yield) is usually confined to fish farms. Grey Herons may take some 0.4–8 % of the production of efficiently managed farms, whereas Cormorants can be responsible for losses of 20 % to >50 % under certain circumstances. The influence of birds is often overestimated by fish farmers if they do not separate predation from other causes of mortality. Neither economical nor ecological damage (i. e. negative influence on the population resulting in long-term decline) have been reported from lakes, although total fish stocks were rarely assessed. In these cases, waterfowl took less than 5 % of the biomass of most fish species; under brackish conditions the maximum was 36 %. Commercial catches are often 10–20 times higher than the consumption by the main avian predators (tab. 1). Even on Central European lakes with high Cormorant densities, fishermen take 4–12 times as much as the Cormorants, and annual variations in the catch can amount to a multiple of the bird consumption (fig. 1). Moreover, waterbirds often prey upon commercially unimportant and abundant fish and may therefore reduce competitive pressure on commercial species. Predation rates in streams and rivers are usually higher than in lakes, but in most cases the avian predation does not seem to exceed the range of compensatory mortality. The few reports of waterbirds apparently responsible for added mortality (thus competing with fisheries), mostly refer to canalised rivers with inadequate structural properties for the high fish populations they are stocked with. Altogether predator-prey relationships between waterbirds and freshwater fish remain little studied. Possibilities of fishponds for conducting experiments have particularly been underused.相似文献