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71.
Jeroen Staelens Tobias Rütting Dries Huygens An De Schrijver Christoph Müller Kris Verheyen Pascal Boeckx 《Biogeochemistry》2012,108(1-3):259-277
Despite long-term enhanced nitrogen (N) inputs, forests can retain considerable amounts of N. While rates of N inputs via throughfall and N leaching are increased in coniferous stands relative to deciduous stands at comparable sites, N leaching below coniferous stands is disproportionally enhanced relative to the N input. A better understanding of factors affecting N retention is needed to assess the impact of changing N deposition on N cycling and N loss of forests. Therefore, gross N transformation pathways were quantified in undisturbed well-drained sandy soils of adjacent equal-aged deciduous (pedunculate oak (Quercus robur L.)) and coniferous (Scots pine (Pinus sylvestris L.)) planted forest stands located in a region with high N deposition (north Belgium). In situ inorganic 15N labelling of the mineral topsoil (0–10?cm) combined with numerical data analysis demonstrated that (i) all gross N transformations differed significantly (p?<?0.05) between the two forest soils, (ii) gross N mineralization in the pine soil was less than half the rate in the oak soil, (iii) meaningful N immobilization was only observed for ammonium, (iv) nitrate production via oxidation of organic N occurred three times faster in the pine soil while ammonium oxidation was similar in both soils, and (v) dissimilatory nitrate reduction to ammonium was detected in both soils but was higher in the oak soil. We conclude that the higher gross nitrification (including oxidation of organic N) in the pine soil compared to the oak soil, combined with negligible nitrate immobilization, is in line with the observed higher nitrate leaching under the pine forest. 相似文献
72.
73.
Dominik Schüßler Marina B. Blanco Nicola K. Guthrie Gabriele M. Sgarlata Melanie Dammhahn Refaly Ernest Mamy Rina Evasoa Alida Hasiniaina Daniel Hending Fabien Jan Barbara le Pors Alex Miller Gillian Olivieri Ando N. Rakotonanahary Solofomalala Jacques Rakotondranary Romule Rakotondravony Tantely Ralantoharijaona Veronarindra Ramananjato Blanchard Randrianambinina Nancia N. Raoelinjanakolona Emilienne Rasoazanabary Rodin M. Rasoloarison David W. Rasolofoson Solofonirina Rasoloharijaona Emmanuel Rasolondraibe Sam Hyde Roberts Helena Teixeira Tobias van Elst Steig E. Johnson Jörg U. Ganzhorn Lounès Chikhi Peter M. Kappeler Edward E. Louis Jr. Jordi Salmona Ute Radespiel 《American journal of physical anthropology》2024,183(1):60-78
74.
Sofie Sjögersten Dries P. J. Kuijper René van der Wal Maarten J. J. E. Loonen Ad H. L. Huiskes Sarah J. Woodin 《Polar Biology》2010,33(9):1195-1203
Herbivores may increase the productivity of forage plants; however, this depends on the return of nutrients from faeces to
the forage plants. The aim of this study was to test if nitrogen (N) from faeces is available to forage plants and whether
the return of nutrients differs between plant species using 15N natural abundance in faeces and plant tissue. To investigate the effect of grazing on N transfer, we carried out a grazing
experiment in wet and mesic tundra on high Arctic Spitsbergen using barnacle geese (Branta leucopsis) as the model herbivore. N inputs (from faeces) increased with grazing pressure at both the wet and mesic sites, with the
greatest N input from faeces at the wet site. The δ15N ratio in plant tissue from grazed plots was enriched in mosses and the dwarf shrub species, reflecting the δ15N signature of faeces-derived N, but no such pattern was observed in the dominant grasses. This study demonstrates that the
δ15N signature of faeces and forage species is a useful tool to explore how grazing impacts on N acquisition. Our findings suggest
that plant species which acquire their N close to the soil surface (e.g. mosses) access more of the N from faeces than species
with deeper root systems (e.g. grasses) suggesting a transfer of N from the preferred forage species to the mosses and dwarf
shrubs, which are less preferred by the geese. In conclusion, the moss layer appears to disrupt the nitrogen return from herbivores
to their forage species. 相似文献
75.
Inna Kuperstein Kerensa Broersen Iryna Benilova Jef Rozenski Wim Jonckheere Maja Debulpaep Annelies Vandersteen Ine Segers-Nolten Kees Van Der Werf Vinod Subramaniam Dries Braeken Geert Callewaert Carmen Bartic Rudi D'Hooge Ivo Cristiano Martins Frederic Rousseau Joost Schymkowitz Bart De Strooper 《The EMBO journal》2010,29(19):3408-3420
The amyloid peptides Aβ40 and Aβ42 of Alzheimer's disease are thought to contribute differentially to the disease process. Although Aβ42 seems more pathogenic than Aβ40, the reason for this is not well understood. We show here that small alterations in the Aβ42:Aβ40 ratio dramatically affect the biophysical and biological properties of the Aβ mixtures reflected in their aggregation kinetics, the morphology of the resulting amyloid fibrils and synaptic function tested in vitro and in vivo. A minor increase in the Aβ42:Aβ40 ratio stabilizes toxic oligomeric species with intermediate conformations. The initial toxic impact of these Aβ species is synaptic in nature, but this can spread into the cells leading to neuronal cell death. The fact that the relative ratio of Aβ peptides is more crucial than the absolute amounts of peptides for the induction of neurotoxic conformations has important implications for anti‐amyloid therapy. Our work also suggests the dynamic nature of the equilibrium between toxic and non‐toxic intermediates. 相似文献
76.
Julien Pétillon Kevin Lambeets William Montaigne Jean-Pierre Maelfait Dries Bonte 《Biological invasions》2010,12(9):3219-3226
Vegetation and underground structures are known to influence flood avoidance and flood resistance in invertebrates. In bimonthly-flooded
European salt marshes, recent invasions by the nitrophilous grass Elymus athericus strongly modified usual habitat structure, notably by the production of a deep litter layer. Consequently, invaded habitats
provide more interstitial spaces that may act as a refuge during flood events. By using both controlled and field designs,
we tested whether invaded habitats may change the ability to resist flooding by the creation of new refuges during tides for
a ground-living, predatory arthropod. The wolf spider Arctosa fulvolineata was employed as a model species since it occurs abundantly in both invaded and uninvaded salt-marsh habitats. In the field,
its abundance strongly decreased (divided by three) after tidal flooding in uninvaded habitats by but did not change in invaded
patches. Under controlled laboratory conditions, ten times more individuals withstood simulated flooding in the presence of
litter and less decided to float. The presence of litter did not influence flood resistance, i.e. survival underwater. Our
results show that habitat structure (i.e. the presence of litter) influences flood-avoiding behavior of A. fulvolineata, by providing more refuges. As the invasion of E. athericus alters salt-marsh habitat structure, it may enhance population size of a rare predatory spider by changing its behavior during
flooding and resulting in less deleterious impacts of tides. Yet biological invasions are detrimental for biodiversity conservation,
our study shows that an invasive species might indirectly benefit a few mobile rare species in a flood-disturbed habitat. 相似文献
77.
Elmar H Pinkhardt Ludger Tebartz van Elst Albert C Ludolph Jan Kassubek 《BMC neurology》2006,6(1):48-6
Background
Evidence for extra-motor involvement in non-demented patients with amyotrophic lateral sclerosis (ALS) has been provided by multiple studies, in particular neuropathological studies have demonstrated neuronal loss in the amygdala. The aim of this study was to investigate possible alterations of amygdala volumes in vivo. 相似文献78.
Laumonier C Segers J Laurent S Michel A Coppée F Belayew A Elst LV Muller RN 《Journal of biomolecular screening》2006,11(5):537-545
Phosphatidylserine (PS) exposure on the cell surface is an early marker of apoptosis. To select PS binding peptides as vectors of contrast agents to image apoptosis, a phage library has been exposed to perfused mouse livers. Phages not retained on control livers during the first perfusions were used for selections on apoptotic livers in a second series of perfusions. Four selected phages were further evaluated for binding to PS-coated enzyme-linked immunosorbent assay (ELISA) plates. They presented an apparent affinity constant (Ka app) for PS ranging from 6.08x10(10) M to 1.62x10(11)M. These phages did not bind to phosphatidylcholine, and competition with annexin V confirmed their specific interaction with PS. The phage with the highest affinity-bound PS in ELISA with a Ka app=(1.6+/-0.2)x10(11)M. It carried the TLVSSL peptide that was synthesized. Specific competition with annexin V and with the synthetic peptide was performed and confirms the specificity of the interaction. 相似文献
79.
Habitat Use and Mobility of Two Threatened Coastal Dune Insects: Implications for Conservation 总被引:2,自引:0,他引:2
Dirk Maes Anneleen Ghesquiere Mieke Logie Dries Bonte 《Journal of Insect Conservation》2006,10(2):105-115
We studied the habitat use and mobility of the Grayling butterfly (Hipparchia semele) and the Blue-Winged Grasshopper (Oedipoda caerulescens), two threatened insects within spatially structured blond and grey dunes in a nature reserve along the Belgian coast. Although
both species occur in the same biotope, H. semele were more abundant in open, dynamic sites with a relatively high amount of bare sand, while O. caerulescens preferred sheltered, more stable environments with a lower amount of bare sand. Unlike H. semele, substrate use varied in accordance to body colouration in O. caerulescens, especially on cold days, with light-coloured animals being more abundant on sand and dark-coloured animals more abundant
on moss. During a mark-recapture-study, we marked 493 Grayling butterflies and 1289 Blue-Winged Grasshoppers. On average,
both sexes of H. semele were equally mobile (about 150 m/day; maximum recorded distance of about 1700 m) while male O. caerulescens were significantly more mobile than females (daily average 47 vs. 5 m; maximum distances observed for O. caerulescens were about 800 m). The importance of habitat heterogeneity (within and among patches) and the consequences of habitat use
and mobility of both species for the conservation of typical coastal dune habitats are discussed. The complementary use of
species-specific information to site-based management measures is advocated. 相似文献
80.
Velinova MJ Staffhorst RW Mulder WJ Dries AS Jansen BA de Kruijff B de Kroon AI 《Biochimica et biophysica acta》2004,1663(1-2):135-142
Cisplatin nanocapsules represent a novel lipid formulation of the anti-cancer drug cis-diamminedichloroplatinum(II) (cisplatin), in which nanoprecipitates of cisplatin are coated by a phospholipid bilayer consisting of a 1:1 mixture of zwitterionic phosphatidylcholine (PC) and negatively charged phosphatidylserine (PS). Cisplatin nanocapsules are characterized by an unprecedented cisplatin-to-lipid ratio and exhibit increased in vitro cytotoxicity compared to the free drug [Nat. Med. 8, (2002) 81]. In the present study, the stability of the cisplatin nanocapsules was optimized by varying the lipid composition of the bilayer coat and monitoring in vitro cytotoxicity and the release of contents during incubations in water and in mouse serum. The release of cisplatin from the PC/PS (1:1) nanocapsules in water increased with increasing temperature with a t(1/2) of 6.5 h at 37 degrees C. At 4 degrees C, cisplatin was retained in the nanocapsules for well over 8 days. Replacement of PS by either phosphatidylglycerol or phosphatidic acid revealed that nanocapsules prepared of PS were more stable, which was found to be due to the ability of PS to form a stable cisplatin-PS coordination complex. Mouse serum had a strong destabilizing effect on the cisplatin nanocapsules. The PC/PS formulation lost over 80% of cisplatin within minutes after resuspension in serum. Incorporation of poly(ethylene glycol 2000) (PEG)-derivatized phosphatidylethanolamine and cholesterol in the bilayer coat extended the lifetime of the cisplatin nanocapsules in mouse serum to almost an hour. The results demonstrate that specificity in the interaction of cisplatin with anionic phospholipids is an important criterium for the formation and stability of cisplatin nanocapsules. 相似文献