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361.
The role of fire in governing rainforest–eucalypt forest ecotone dynamics is of theoretical interest and has conservation management implications. Several eucalypt forests in the Wet Tropics of Australia have an endangered status due to extensive conversion to rainforest. Rainforest plants are known to survive occasional low intensity fires in the eucalypt forest ecotone. However, the ability of rainforest plants to survive frequent fires remains untested. The timing of rainforest expansion is also a subject of interest, and is generally considered to be delayed until fire has been absent for several years. We used 14 years of data collected across 13 plots in the Wet Tropics of north‐eastern Australia to test predictions regarding rainforest seedling recruitment and post‐fire regenerative capacity. The 13 plots received different numbers of fires, between zero and five, over the 14‐year study. The recruitment of new rainforest plants in the ecotone was most abundant in the initial year after fire. If this post‐fire pulse of recruitment is left undisturbed, it can facilitate the subsequent germination of additional rainforest species. The removal of grass cover, whether temporarily in the immediate post‐fire environment or once a developing rainforest mid strata shades out grasses, appears crucial to abundant rainforest recruitment. A variety of tropical rainforest species can persist under a frequent fire regime through resprouting. The difference in the mode of resprouting, between ground‐level coppicing rainforest plants and canopy resprouting eucalypt forest trees, is the critical mechanism that causes regular fire to maintain an open structure in eucalypt forests. The inability of rainforest species to maintain their height when fires fully scorch their crowns, temporarily resets the forest's open structure and delays the rainforest's ability to dominate through shading out grasses to transform the ecosystem into a closed forest. 相似文献
362.
László Sipos István Ilisz Anita Aranyi Zsanett Gecse Melinda Nonn Ferenc Fülöp Myung Ho Hyun Antal Péter 《Chirality》2012,24(10):817-824
The enantiomers of four unusual isoxazoline‐fused 2‐aminocyclopentanecarboxylic acids were directly separated on chiral stationary phases containing (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid as chiral selector. The nature of the alcoholic modifier (MeOH, EtOH, IPA) exerted a great effect on the retention, whereas the selectivity and resolution did not change substantially. Two types of dependence of retention on alcohol content were detected: k1 increased continuously with increasing alcohol content or a U‐shaped retention curve was observed. A comparison of the chromatographic data obtained with HCOOH, AcOH, TFA, HClO4, H2SO4, or H3PO4 as acidic modifier at a constant concentration demonstrated that in most cases, larger k values were obtained on the application of AcOH or HCOOH, and an increase of the acid content resulted in a decrease of retention. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes and selector. The sequence of elution of the enantiomers was determined in all cases. Chirality 24:817‐824, 2012. © 2012 Wiley Periodicals, Inc. 相似文献
363.
Rohan D. Wilson John W. H. Trueman Stephen E. Williams David K. Yeates 《Biodiversity and Conservation》2007,16(11):3163-3177
The Australian Wet Tropics World Heritage Area (WTWHA) contains a number of highland vertebrates predicted to face extinction
due to a warming climate, but little is known about risks to invertebrates, which are vital to ecosystem health. This study
investigates the distribution and abundance patterns of the Dipteran sub-order Schizophora along an altitudinal transect in
the Carbine Uplands of the WTWHA using Malaise traps. The season of peak abundance changed with altitude, with highland abundance
peaking in October, and lowland abundance peaking in April. There was a high level of species turnover with altitude, and
some evidence for distinct low-, mid-, and high-elevation assemblages, with the high-elevation assemblage containing the most
restricted species. We would expect this high-elevation assemblage to be at risk of local extinction with 2–3° of warming,
and the mid-elevation assemblage to be at risk with 4–5° warming. Future work should continue sampling to confirm patterns
presented here and to monitor range shifts with climate change. A highland species—Helosciomyza
ferruginea Hendel is suggested as a good indicator species for such monitoring. 相似文献
364.
365.
366.
Helen T. Murphy Daniel J. Metcalfe Matt G. Bradford Andrew J. Ford 《Austral ecology》2014,39(6):696-709
Cyclones are relatively infrequent, may cause massive and widespread disturbance to tropical regions, and are recognized as important determinants of the structure of tropical rainforest communities. Climate change scientists predict that the intensity of cyclones will increase in the future; understanding the long‐term implications of these major disturbances for tropical forest composition and structure will be vital in anticipating and adapting to future changes and impacts. We established a long‐term monitoring site in a rainforest area impacted by severe tropical Cyclone Larry which crossed the North Queensland coast of Australia in March 2006. We monitored recruitment, growth and mortality of nearly 17 000 seedlings in 90 quadrats across the study area for almost 5 years following the cyclone and measured the impact of variation in cyclone disturbance and debris load on community diversity, composition and dispersion as the forest recovered. We show that the level of structural disturbance sustained by the forest has a strong and immediate influence on community dynamics. Quadrats in severely disturbed areas, which were characterized by multiple treefalls and extensive canopy loss, had higher levels of diversity and variation in community assemblage than quadrats in areas characterized primarily by branch loss and defoliation. A rapid divergence in community composition between quadrats in the most‐ and least‐severely disturbed areas resulted in the development of statistically distinct community states across relatively small scales. This provides further evidence that severe cyclones are important in maintaining species diversity in tropical forests. 相似文献
367.
Inter- and intra-annual variations of macroinvertebrate assemblages are related to the hydroperiod in Mediterranean temporary ponds 总被引:1,自引:1,他引:0
Margarita Florencio Laura Serrano Carola Gómez-Rodríguez Andrés Millán Carmen Díaz-Paniagua 《Hydrobiologia》2009,634(1):167-183
Macroinvertebrate assemblages of 22 temporary ponds with different hydroperiod were sampled monthly during a dry year (2005–2006)
and a wet year (2006–2007). Coleopteran and Heteropteran adults were most abundant at the end of the hydroperiod, while Coleopteran
larvae, mainly Dytiscidae, were mostly recorded in spring. Macroinvertebrate assemblages differed between study years. The
shorter hydroperiod of ponds in the dry year constrained the length of the aquatic period for macroinvertebrates, and three
distinct wet phases of community composition could be distinguished: filling phase, aquatic phase and drying phase. In the
wet year, with a longer pond hydroperiod, five phases could be identified, with the aquatic phase differentiated into winter,
early spring and late spring phases. Dispersers such as Anisops sardeus, Berosus guttalis or Anacaena lutescens were typical during the filling phase and Corixa affinis or Enochrus fuscipennis during the drying phase. The ponds with intermediate hydroperiod showed a similar composition (mainly dispersers) at the
beginning and end of their wet period; this is not being seen in early drying or long hydroperiod ponds. A general pattern
was detected, with similar variation between both years, which may be associated with the life histories of the macroinvertebrate
taxa recorded.
Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle
Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16
May 2008 相似文献
368.
Dbora Kestring Jeferson Klein Luciana Cristina Candido Ribeiro de Menezes Marcelo Nogueira Rossi 《Aquatic Botany》2009,91(2):105-109
Mimosa bimucronata is a pioneering tree that occurs predominantly in moist lowlands, floodplains and on margins of rivers and lakes in Latin America. The effect of submergence on seed germination in M. bimucronata was firstly studied. Patterns of water absorption by M. bimucronata seeds were investigated thereafter to assess the imbibition phases of scarified and unscarified seeds. The germination percentage was significantly higher in scarified than in unscarified seeds, and the velocity of seed germination also increased considerably in scarified seeds. Submergence duration did not significantly affect germination percentages of scarified and unscarified seeds. Therefore, seed viability after submersion suggests that M. bimucronata may display hydrochorous dispersal and also that seeds are able to germinate successfully in areas with frequent seasonal flooding. With respect to imbibition phases, phase II was very short or even absent for scarified and unscarified seeds; therefore, a plateau, where water absorption by seeds is established, was not observed. Finally, we verified that the passage from phase I to III was very tenuous and took a long time in seeds without scarification. 相似文献
369.
Leho Tedersoo Genevieve Gates Chris W. Dunk Teresa Lebel Tom W. May Urmas Kõljalg Teele Jairus 《Mycorrhiza》2009,19(6):403-416
Decaying wood provides an important habitat for animals and forms a seed bed for many shade-intolerant, small-seeded plants,
particularly Nothofagus. Using morphotyping and rDNA sequence analysis, we compared the ectomycorrhizal fungal community of isolated N. cunninghamii seedlings regenerating in decayed wood against that of mature tree roots in the forest floor soil. The /cortinarius, /russula-lactarius,
and /laccaria were the most species-rich and abundant lineages in forest floor soil in Australian sites at Yarra, Victoria
and Warra, Tasmania. On root tips of seedlings in dead wood, a subset of the forest floor taxa were prevalent among them species
of /laccaria, /tomentella-thelephora, and /descolea, but other forest floor dominants were rare. Statistical analyses suggested
that the fungal community differs between forest floor soil and dead wood at the level of both species and phylogenetic lineage.
The fungal species colonizing isolated seedlings on decayed wood in austral forests were taxonomically dissimilar to the species
dominating in similar habitats in Europe. We conclude that formation of a resupinate fruit body type on the underside of decayed
wood is not necessarily related to preferential root colonization in decayed wood. Rather, biogeographic factors as well as
differential dispersal and competitive abilities of fungal taxa are likely to play a key role in structuring the ectomycorrhizal
fungal community on isolated seedlings in decaying wood. 相似文献
370.
Peattie AM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(3):231-239
Climbing organisms are constantly challenged to make their way rapidly and reliably across varied and often novel terrain.
A diversity of morphologically and mechanically disparate attachment strategies have evolved across widely distributed phylogenetic
groups to aid legged animals in scaling these surfaces, notable among them some very impressive adhesive pads. Despite the
differences between, for example, the dry fibrillar pads of geckos and the smooth, secretion-aided pads of stick insects,
I hypothesize that they face similar functional demands in their environment. I outline three broad criteria defining dynamic
biological adhesion: reusability, reversibility, and substrate tolerance. Organismal adhesive pads must be able to attach
repeatedly without significant decline in performance, detach easily at will, and adhere strongly to the broadest possible
range of surfaces in their habitat. A survey of the literature suggests that evidence for these general principles can be
found in existing research, but that many gaps remain to be filled. By taking a comparative, integrative approach to biological
dynamic adhesion, rather than focusing on a few model organisms, investigators will continue to discover new and interesting
attachment strategies in natural systems. 相似文献