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101.
102.
103.
The peculiar heme pocket of the 2/2 hemoglobin of cold-adapted Pseudoalteromonas haloplanktis TAC125
Barry D. Howes Daniela Giordano Leonardo Boechi Roberta Russo Simona Mucciacciaro Chiara Ciaccio Federica Sinibaldi Maria Fittipaldi Marcelo A. Mart�� Dar��o A. Estrin Guido di Prisco Massimo Coletta Cinzia Verde Giulietta Smulevich 《Journal of biological inorganic chemistry》2011,16(2):299-311
The genome of the cold-adapted bacterium Pseudoalteromonas haloplanktis TAC125 contains multiple genes encoding three distinct monomeric hemoglobins exhibiting a 2/2 ??-helical fold. In the present work, one of these hemoglobins is studied by resonance Raman, electronic absorption and electronic paramagnetic resonance spectroscopies, kinetic measurements, and different bioinformatic approaches. It is the first cold-adapted bacterial hemoglobin to be characterized. The results indicate that this protein belongs to the 2/2 hemoglobin family, Group II, characterized by the presence of a tryptophanyl residue on the bottom of the heme distal pocket in position G8 and two tyrosyl residues (TyrCD1 and TyrB10). However, unlike other bacterial hemoglobins, the ferric state, in addition to the aquo hexacoordinated high-spin form, shows multiple hexacoordinated low-spin forms, where either TyrCD1 or TyrB10 can likely coordinate the iron. This is the first example in which both TyrCD1 and TyrB10 are proposed to be the residues that are alternatively involved in heme hexacoordination by endogenous ligands. 相似文献
104.
Pedro Ortega-Mart��nez Beatriz ��gueda Luz Marina Fern��ndez-Toir��n Fernando Mart��nez-Pe?a 《Mycorrhiza》2011,21(1):65-70
The study of factors influencing the production and development of wild edible mushroom sporocarps is extremely important
in the characterization of the fungi life cycle. The main objective of this work is to determine how tree age influences the
speed of sporocarp growth of edible ectomycorrhizal fungi Boletus edulis and Lactarius deliciosus in a Pinus sylvestris stand. This study is based on information recorded on a weekly basis every autumn between 1995 and 2008 in a set of permanent
plots in Spain. Sporocarps are collected weekly, and as a result, specimens may not have reached their maximum size. The study
area is a monospecific P. sylvestris stand. Three age classes were considered: under 30 years, between 31 and 70 years, and over 70 years. Sporocarps of B. edulis and L. deliciosus grow faster in the first age class stands than in the other two, and in the second age class stands, sporocarps are more
than 50% smaller. The average weight of the picked B. edulis sporocarps clearly varies in the three age classes considered, with its maximum in the first age class (127 g and 6.8 cm
cap diameter), minimum in the second age class (68 g and 4.7 cm cap diameter), and showing a relative maximum in the third
(79 g and 4.3 cm cap diameter). L. deliciosus sporocarps are on average larger in the first age class (48 g and 7.4 cm cap diameter), decreasing in the second (20 g and
5.8 cm cap diameter) and also in the third (21 g and 5.3 cm cap diameter). The results show the influence of tree age in speed
of sporocarp growth for the two ectomycorrhizal species. 相似文献
105.
Anders Nielsen Ingolf Steffan-Dewenter Catrin Westphal Olivia Messinger Simon G. Potts Stuart P. M. Roberts Josef Settele Hajnalka Szentgy?rgyi Bernard E. Vaissi��re Michalis Vaitis Michal Woyciechowski Ioannis Bazos Jacobus C. Biesmeijer Riccardo Bommarco William E. Kunin Thomas Tscheulin Ellen Lamborn Theodora Petanidou 《Ecological Research》2011,26(5):969-983
The decline of bees has raised concerns regarding their conservation and the maintenance of ecosystem services they provide to bee-pollinated wild flowers and crops. Although the Mediterranean region is a hotspot for bee species richness, their status remains poorly studied. There is an urgent need for cost-effective, reliable, and unbiased sampling methods that give good bee species richness estimates. This study aims: (a) to assess bee species richness in two common Mediterranean habitat types: semi-natural scrub (phrygana) and managed olive groves; (b) to compare species richness in those systems to that of other biogeographic regions, and (c) to assess whether six different sampling methods (pan traps, variable and standardized transect walks, observation plots and trap nests), previously tested in other European biogeographic regions, are suitable in Mediterranean communities. Eight study sites, four per habitat type, were selected on the island of Lesvos, Greece. The species richness observed was high compared to other habitat types worldwide for which comparable data exist. Pan traps collected the highest proportion of the total bee species richness across all methods at the scale of a study site. Variable and standardized transect walks detected the highest total richness over all eight study sites. Trap nests and observation plots detected only a limited fraction of the bee species richness. To assess the total bee species richness in bee diversity hotspots, such as the studied habitats, we suggest a combination of transect walks conducted by trained bee collectors and pan trap sampling. 相似文献
106.
The hippocampus is critical to remembering the flow of events in distinct experiences and, in doing so, bridges temporal gaps between discontiguous events. Here, we report a robust hippocampal representation of sequence memories, highlighted by "time cells" that encode successive moments during an empty temporal gap between the key events, while also encoding location and ongoing behavior. Furthermore, just as most place cells "remap" when a salient spatial cue is altered, most time cells form qualitatively different representations ("retime") when the main temporal parameter is altered. Hippocampal neurons also differentially encode the key events and disambiguate different event sequences to compose unique, temporally organized representations of specific experiences. These findings suggest that hippocampal neural ensembles segment temporally organized memories much the same as they represent locations of important events in spatially defined environments. 相似文献
107.
Yogan Monnier Bruno Vila Nicolas Mont��s Anne Bousquet-M��lou Bernard Pr��vosto Catherine Fernandez 《Trees - Structure and Function》2011,25(3):497-507
Pinus halepensis Mill., is a Mediterranean pioneer forest species with shade-intolerant features. The purpose of this study is to better understand
how stand fertility and allelopathic properties of adult trees influence shade acclimation of saplings. Crown growth and morphological
plasticity were studied under different light, fertilization, and allelopathic conditions in a nursery experiment. We tested
whether shade-acclimation capacity increases with fertilization, and is affected by autotoxicity due to pine leachates. We
examined stem diameter, and crown characteristics (length, width, shape, and density) in a factorial experiment with two levels
for each tested factor: light (full and 20% reduced light), fertilization (low and high rate of NPK fertilizer) and allelopathy
(control and allelopathic leachates uptake). In our study, shading induced a significantly higher crown length, width, and
surface. Fertilization strongly increased crown length and vertical expended crown shape (the ratio crown length/crown width).
Leachates uptake reduced crown length and density, highlighting an autotoxicity phenomenon. We concluded that P. halepensis saplings presented a shade-avoiding syndrome and that the crown shade-acclimation response increased with fertilization but
was severely compromised by autotoxicity. We finally discuss the role of fertilization and allelopathy in early P. halepensis acclimation ability. 相似文献
108.
109.
Claudia C. Soliz-Gamboa Dana? M. A. Rozendaal Greg��rio Ceccantini Veronica Angyalossy Klaas van der Borg Pieter A. Zuidema 《Trees - Structure and Function》2011,25(1):17-27
Knowledge on juvenile tree growth is crucial to understand how trees reach the canopy in tropical forests. However, long-term
data on juvenile tree growth are usually unavailable. Annual tree rings provide growth information for the entire life of
trees and their analysis has become more popular in tropical forest regions over the past decades. Nonetheless, tree ring
studies mainly deal with adult rings as the annual character of juvenile rings has been questioned. We evaluated whether juvenile
tree rings can be used for three Bolivian rainforest species. First, we characterized the rings of juvenile and adult trees
anatomically. We then evaluated the annual nature of tree rings by a combination of three indirect methods: evaluation of
synchronous growth patterns in the tree- ring series, 14C bomb peak dating and correlations with rainfall. Our results indicate that rings of juvenile and adult trees are defined
by similar ring-boundary elements. We built juvenile tree-ring chronologies and verified the ring age of several samples using
14C bomb peak dating. We found that ring width was correlated with rainfall in all species, but in different ways. In all, the
chronology, rainfall correlations and 14C dating suggest that rings in our study species are formed annually. 相似文献
110.
Jos�� Climent Roberto San-Mart��n Maria Regina Chambel Sven Mutke 《Trees - Structure and Function》2011,25(2):175-186
Heteroblastic development in pine seedlings includes extreme morphological changes with still unclear adaptive and evolutionary
significance. In particular, Mediterranean and Eurasian pines (section Pinus) living in the Mediterranean basin seem to follow quite distinct developmental trajectories at the seedling stage. Aiming
to confirm this ontogenetic differentiation we performed a nursery experiment with seedlings of five Mediterranean pines (Pinus pinaster, P. brutia, P. halepensis, P. pinea and P. canariensis) and three Eurasian pines (P. sylvestris, P. uncinata, and P. nigra subsp. salzmannii), also including P. radiata as an outgroup. After destructive analyses at two harvest times (9 and 32 weeks), we found sharp differentiation between
Mediterranean and Eurasian pines in a combination of traits linked to shoot heteroblasty. In particular, Mediterranean pines
showed a marked delay in the proportion of adult needles to total needles in the shoot compared to Eurasian species, especially
at the second harvest. However, two Mediterranean pines, P. pinaster and P. brutia showed a slightly higher proportion of secondary needles, and a higher rate of budset at a more advanced stage (68 weeks)
compared to the other three Mediterranean species. Meaningfully, the outgroup P. radiata was the only species combining a high proportion of adult foliage since the first harvest with a delayed formation of the
first terminal bud. We discussed the adaptive significance of these findings at the light of species’ climatic niches and
life histories. 相似文献