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281.
Enrique Alfaro Pablo LpezJimnez Jos GonzlezMartínez Marcos Malumbres Jos A Suja Rocío Gmez 《EMBO reports》2021,22(4)
Cell division requires the regulation of karyokinesis and cytokinesis, which includes an essential role of the achromatic spindle. Although the functions of centrosomes are well characterised in somatic cells, their role during vertebrate spermatogenesis remains elusive. We have studied the dynamics of the meiotic centrosomes in male mouse during both meiotic divisions. Results show that meiotic centrosomes duplicate twice: first duplication occurs in the leptotene/zygotene transition, while the second occurs in interkinesis. The maturation of duplicated centrosomes during the early stages of prophase I and II are followed by their separation and migration to opposite poles to form bipolar spindles I and II. The study of the genetic mouse model Plk1(Δ/Δ) indicates a central role of Polo‐like kinase 1 in pericentriolar matrix assembly, in centrosome maturation and migration, and in the formation of the bipolar spindles during spermatogenesis. In addition, in vitro inhibition of Polo‐like kinase 1 and Aurora A in organotypic cultures of seminiferous tubules points out to a prominent role of both kinases in the regulation of the formation of meiotic bipolar spindles. 相似文献
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Francesco Santini Laurie Sorenson Tina Marcroft Alex Dornburg Michael E. Alfaro 《Molecular phylogenetics and evolution》2013,66(1):153-160
Boxfishes (superfamily Ostracioidea, order Tetraodontiformes) are comprised of 37 species within the families Aracanidae (13 sp.) and Ostracidae (24 sp.). These species are characterized by several dramatic reductive trends in their axial and appendicular skeleton, and by the presence of a carapace formed by enlarged and thickened scale plates. While strong support exists for the monophyly of both families, interspecific relationships remain unclear as no species-level molecular phylogeny currently exists for either of these two clades, and the only hypotheses of relationships are based on morphological studies that were mostly restricted to generic-level relationships. Here we present the results of a new phylogenetic study of a dataset composed of 9 loci for 26 species of boxfishes using both likelihood and Bayesian methods. Our topology strongly supports the monophyly of both groups, and additionally provides strongly supported resolution for the vast majority of species-level interrelationships. Based on this new phylogeny, we suggest changing the taxonomic status of the species Lactoria fornasini to Tetrasomus fornasini, and Rhynchostracion nasus to Ostracion nasus. Using a Bayesian approach to divergence time estimation we inferred a Paleocene origin of the Ostracioidea, with an estimated origin of the reef-associated ostraciids spanning the Eocene and Oligocene, and a Miocene/Pliocene origin of the aracanids. 相似文献
286.
Summary Soft-sediment deformation structures in Tortonian turbiditic deposits of the Guadix Basin (southern Spain) have been described.
The most common structures are asymmetrical pillow structures and elongated sets of loadcasts. The structures are metric in
scale and have been interpreted as the result of liquefaction and/or fluidization processes triggered by the rapid sedimentation
of single high concentration turbidites.
Final morphology of soft-sediment deformation structures is related to two main driving force systems: unstable density gradient
and lateral shear stress. The latter is probably induced by the downslope component of the sediment weight. The asymmetry
of deformational structures (in horizontal and vertical cross-section) allows a clarification of the relationship between
morphology of deformation and direction of lateral shear stress: this relationship seems ambiguous and confused in the literature.
The interpretations both of deformation mechanism and trigger agent have been supported with:-field analyses;-calculations
on the liquefaction processes induced by rapid sedimentation;-qualitative models in laboratory. 相似文献