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371.
LEONARDO DAPPORTO JAN CRISTIAN HABEL ROGER L. H. DENNIS THOMAS SCHMITT 《Biological journal of the Linnean Society. Linnean Society of London》2011,103(3):571-577
In the western Palaearctic, the Mediterranean zone is an important region where taxa and genes of thermophilous organisms are preserved during glacial stages and new clades are generated. This is achieved through the existence of refugia over Mediterranean Europe and North Africa, where organisms persisted and continued to evolve during the cold phases. However, it is not clear in detail how these refugia function for the maintenance of ancestral taxa, the evolution of new taxa, and as launching pads during postglacial colonizations of northern Europe. One outstanding issue is the incongruence of findings from different marker systems. For the butterfly Maniola jurtina, morphometry and allozyme data analyzed for populations scattered over Europe and North Africa show congruent patterns for Sicily and the Maghreb but produce discrepant results for the Italian mainland. This discrepancy between allozyme and morphological data can be explained by recent gene flow in the wake of postglacial range expansions and shifts. It is evident that colonization histories are far more complex than originally considered. We highlight different aspects of colonization and evolutionary history emerging from the joint use of different marker systems and advocate multiple uses of different markers in paleobiogeographic reconstructions to explore evolutionary events and colonization pathways. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 571–577. 相似文献
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FELIPE FIGUEROA WERNER E. MAYER JIÍ LOM IVA DYKOVÁ MATHIAS WELLER HANA PECKOVA JAN KLEIN 《The Journal of eukaryotic microbiology》1999,46(5):473-481
Fish trypanosomes have traditionally been classified according to the host species from which they were isolated, each isolate being regarded as a distinct species. To test the soundness of this practice, the genetic variabilities of the kinetoplast 12S rRNA-encoding genes of different fish trypanosomes isolates were compared. The DNAs were extracted from trypanosomes cloned from blood samples of 15 donors representing ten different fish species in four orders from waters of three major river systems of Central and Northern Europe. Comparison with other trypanosomatid sequences revealed that the fish trypanosomes form a monophyletic group with Trypanosoma brucei as a sister group. Pairwise comparisons of genetic distances yielded a wide range of continuous variation with no indication of any discontinuities attributable to barriers to gene flow. The genetic distances did not correlate with either the identity of the host species or geography. The host specificity of fish trypanosomes appears to be limited. 相似文献
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375.
JAN L. ELDRIDGE GARY L. KRAPU DOUGLAS H. JOHNSON 《The Journal of wildlife management》2009,73(2):248-252
ABSTRACT We evaluated food habits of 4 species of spring-migrant calidrid sandpipers in the Prairie Pothole Region (PPR) of North Dakota. Sandpipers foraged in several wetland classes and fed primarily on aquatic dipterans, mostly larvae, and the midge family Chironomidae was the primary food eaten. Larger sandpiper species foraged in deeper water and took larger larvae than did smaller sandpipers. The diverse wetland habitats that migrant shorebirds use in the PPR suggest a landscape-level approach be applied to wetland conservation efforts. We recommend that managers use livestock grazing and other tools, where applicable, to keep shallow, freshwater wetlands from becoming choked with emergent vegetation limiting chironomid production and preventing shorebird use. 相似文献
376.
MARCIA J. LOEB ROBERT A. BELL DALE B. GELMAN JAN KOCHANSKY WILLIAM LUSBY RENEE M. WAGNER 《Invertebrate reproduction & development.》2013,57(1-3):181-190
Summary Testis sheaths from late last instar larvae and mid-developing pupae of Heliothis virescens and Lymantria dispar synthesize ecdysteroid in vitro. Gonadal ecdysteroid can stimulate the production of growth factors from the sheaths which, in turn, promote the growth and development of the genital tract. Ongoing basal synthesis is controlled by positive feedback to exogenous ecdysteroid; titers of this hormone approaching those of molting last instar larvae and developing pupae effect maximum synthesis. These findings suggest that circulating titers of ecdysteroid hormone promote gonadal ecdysteroidogenesis, and thus coordinate the actions of the gonads with metamorphic events in the whole animal. Synthesis of ecdysteroid by testes is initiated, however, by a brain neuropeptide, testis ecdysiotropin (TE). TE is a 21 amino acid peptide of molecular weight 2472 Da. TE boosts basal steroid synthesis by pupal testis sheaths as well. It acts primarily via Gi protein and second messengers diacyl glycerol and low calcium influx, resulting in stimulation of phosphokinase C. Gs protein and its resultant messenger, cyclic AMP, also play roles in activation and inhibition of ecdysteroidogenesis. The interplay of controlling systems probably serves to fine tune a system essential to gonadal development and function. 相似文献
377.
There is concern that the use of neuroenhancements to alter character traits undermines consumer's authenticity. But the meaning, scope and value of authenticity remain vague. However, the majority of contemporary autonomy accounts ground individual autonomy on a notion of authenticity. So if neuroenhancements diminish an agent's authenticity, they may undermine his autonomy. This paper clarifies the relation between autonomy, authenticity and possible threats by neuroenhancements. We present six neuroenhancement scenarios and analyse how autonomy accounts evaluate them. Some cases are considered differently by criminal courts; we demonstrate where academic autonomy theories and legal reasoning diverge and ascertain whether courts should reconsider their concept of autonomy. We argue that authenticity is not an appropriate condition for autonomy and that new enhancement technologies pose no unique threats to personal autonomy. 相似文献
378.
Dormant and after-ripened seeds of Agrostemma githago (corn-cockle)were pretreated in polyethylene glycol 400 (PEG) solutions attemperatures which would have allowed germination if the seedshad been imbibed in water, viz. 4?C or 20?C for after-ripenedseeds, and 4?C for dormant seeds. Pretreated seeds germinatedfaster than untreated seeds. The maximum decrease of the T50(time to 50% germination) was 66%. Furthermore, pretreated seedswere capable of germination at supra-optimal temperatures whichotherwise had inhibited germination completely (20?C for dormantseeds and 30?C for after-ripened seeds). The percentage germinationat a supra-optimal temperature was considerably higher whenthe seeds had been primed at a temperature at which they developedmore extension power. The advantageous effects of the osmotic pretreatment were lessthan might be expected when the osmoticum had inhibited onlycell elongation. This was largely, if not fully, due to a generaldetrimental effect of osmotic stress and not to a selectiveinhibition of the processes which occur during the pregerminativephase in preparation for growth. Thus, during priming seedscomplete all or almost all processes which occur in water-imbibedseeds prior to radicle emergence. Key words: Agroatemma githago, dormancy, germination, germination performance, osmotic stress, priming 相似文献
379.
JAN BERGSTRÖM 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1977,10(2):95-105
Classification should at least to some extent show phylogenetic relationships. It is therefore reasonable to base any classification on a discussion of phylogeny and analysis of phylogenetically relevant features. Adaptational features likely to evolve many times must be sorted out in the discussion of relationships, but may be useful to describe the evolution inside phyletic lineages defined by other means. The Proetida, as defined by Fortey & Owens 1975, are taken as an example of a heterogeneous taxon based on purely morphological features. A phylogenetic approach to ontogenetical, morphological and functional criteria seems to indicate that the Proetida fall into at least three groups without close relationships. 相似文献
380.
Pachygnatha kiwuana Strand, P. leleupi Lawrence, P. longipes Simon. P. mucronata Tullgren, P. palmqvisti Tullgren, P. ruanda Strand and Dyschiriognatha argyrostilba (O.-P. Cambridge, 1876) (junior synonym: D. atlantica Holm, 1969) are redescribed. Puchygnutha hexutrucheutu, P. zuppu, P. procincta, P. okuensis, P. utromurginata, P. jansseni, P., goedeli, P. opdmwrdiue and Glenognatha smilodon, all species collected during the Belgian Cameroon expeditions, arc described as new. A key for all Afrotropical species is presented. 相似文献