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61.
Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms 总被引:15,自引:0,他引:15
Orr JC Fabry VJ Aumont O Bopp L Doney SC Feely RA Gnanadesikan A Gruber N Ishida A Joos F Key RM Lindsay K Maier-Reimer E Matear R Monfray P Mouchet A Najjar RG Plattner GK Rodgers KB Sabine CL Sarmiento JL Schlitzer R Slater RD Totterdell IJ Weirig MF Yamanaka Y Yool A 《Nature》2005,437(7059):681-686
Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms--such as corals and some plankton--will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean-carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously. 相似文献
62.
Gandin V Miluzio A Barbieri AM Beugnet A Kiyokawa H Marchisio PC Biffo S 《Nature》2008,455(7213):684-688
Cell growth and proliferation require coordinated ribosomal biogenesis and translation. Eukaryotic initiation factors (eIFs) control translation at the rate-limiting step of initiation. So far, only two eIFs connect extracellular stimuli to global translation rates: eIF4E acts in the eIF4F complex and regulates binding of capped messenger RNA to 40S subunits, downstream of growth factors, and eIF2 controls loading of the ternary complex on the 40S subunit and is inhibited on stress stimuli. No eIFs have been found to link extracellular stimuli to the activity of the large 60S ribosomal subunit. eIF6 binds 60S ribosomes precluding ribosome joining in vitro. However, studies in yeasts showed that eIF6 is required for ribosome biogenesis rather than translation. Here we show that mammalian eIF6 is required for efficient initiation of translation, in vivo. eIF6 null embryos are lethal at preimplantation. Heterozygous mice have 50% reduction of eIF6 levels in all tissues, and show reduced mass of hepatic and adipose tissues due to a lower number of cells and to impaired G1/S cell cycle progression. eIF6(+/-) cells retain sufficient nucleolar eIF6 and normal ribosome biogenesis. The liver of eIF6(+/-) mice displays an increase of 80S in polysomal profiles, indicating a defect in initiation of translation. Consistently, isolated hepatocytes have impaired insulin-stimulated translation. Heterozygous mouse embryonic fibroblasts recapitulate the organism phenotype and have normal ribosome biogenesis, reduced insulin-stimulated translation, and delayed G1/S phase progression. Furthermore, eIF6(+/-) cells are resistant to oncogene-induced transformation. Thus, eIF6 is the first eIF associated with the large 60S subunit that regulates translation in response to extracellular signals. 相似文献
63.
64.
Vascular endothelial growth factors (VEGFs) and their high-affinity tyrosine kinase VEGF receptors (VEGFRs) are key regulators of both angiogenesis and neurogenesis. The current issue of CMLS discusses recent literature and work implementing these signals in nervous system development, maintenance and disease pathology. 相似文献
65.
Mary Anne Rogers 《西北部美国博物学家》2011,51(2)
Geographic and nongeographic variation in morphology was examined in Thomomys townsendii . A univariate analysis of external and cranial characters from a large population sample (66 adults; fusion of cranial sutures used as aging criteria) was used to assess variation among three adult age classes and between sexes. Only minor variation is apparent among age classes; however, sexual dimorphism is pronounced. Univariate and multivariate techniques were used to analyze external and cranial measurements and pelage characters for adults throughout the species range. These analyses show little to support the seven subspecific designations recognized by Davis (1937). The general pattern is one of homogeneity throughout the range of Thomomys townsendii . With the possible exception of T. t. nevadensis samples, current subspecies are not defined as morphological units. In fact, differentiation is found among populations within some subspecies. The most apparent pattern seen in these analyses is the divergence between the Humboldt River (including Honey Lake Valley samples) and Snake River systems. These results will be considered with those of a companion paper on the genetic variation in this species to more adequately assess the patterns of differentiation in Thomomys townsendii . 相似文献
66.
Annual plant populations in norhtwestern New Mexico were found to be spatially and temporally highly variable. During favorable years annual plant species have patterns of dominance and diversity that are different from those of perennial species. Measurement of perennial plant diversity in plant communities is a poor predictor of productivity. Both perennial and annual components of plant communities should be considered in measurements of diversity and productivity. 相似文献
67.
Fabiano F. Albertoni Josefina Steiner Anne Zillikens 《Journal of Natural History》2016,50(47-48):2917-2939
This work presents the first list of Coleoptera species found in Hohenbergia augusta (Vell.) E. Morren and Vriesea friburgensis Mez. (Bromeliaceae), in Santa Catarina state, Brazil, most of them identified to the species level. Beetle species richness and composition were compared between the bromeliad species and between Atlantic forest and restinga habitats. Biological information on some beetle species is reported for the first time. We also discuss the aquatic habit of the hydrophilid Lachnodacnum luederwaldti Orchymont, 1937 (Sphaeridinae) inside bromeliad phytotelms. 相似文献
68.
Operons (clusters of co-regulated genes with related functions) are common features of bacterial genomes. More recently, functional
gene clustering has been reported in eukaryotes, from yeasts to filamentous fungi, plants, and animals. Gene clusters can
consist of paralogous genes that have most likely arisen by gene duplication. However, there are now many examples of eukaryotic
gene clusters that contain functionally related but non-homologous genes and that represent functional gene organizations
with operon-like features (physical clustering and co-regulation). These include gene clusters for use of different carbon
and nitrogen sources in yeasts, for production of antibiotics, toxins, and virulence determinants in filamentous fungi, for
production of defense compounds in plants, and for innate and adaptive immunity in animals (the major histocompatibility locus).
The aim of this article is to review features of functional gene clusters in prokaryotes and eukaryotes and the significance
of clustering for effective function. 相似文献
69.
Aury JM Jaillon O Duret L Noel B Jubin C Porcel BM Ségurens B Daubin V Anthouard V Aiach N Arnaiz O Billaut A Beisson J Blanc I Bouhouche K Câmara F Duharcourt S Guigo R Gogendeau D Katinka M Keller AM Kissmehl R Klotz C Koll F Le Mouël A Lepère G Malinsky S Nowacki M Nowak JK Plattner H Poulain J Ruiz F Serrano V Zagulski M Dessen P Bétermier M Weissenbach J Scarpelli C Schächter V Sperling L Meyer E Cohen J Wincker P 《Nature》2006,444(7116):171-178
The duplication of entire genomes has long been recognized as having great potential for evolutionary novelties, but the mechanisms underlying their resolution through gene loss are poorly understood. Here we show that in the unicellular eukaryote Paramecium tetraurelia, a ciliate, most of the nearly 40,000 genes arose through at least three successive whole-genome duplications. Phylogenetic analysis indicates that the most recent duplication coincides with an explosion of speciation events that gave rise to the P. aurelia complex of 15 sibling species. We observed that gene loss occurs over a long timescale, not as an initial massive event. Genes from the same metabolic pathway or protein complex have common patterns of gene loss, and highly expressed genes are over-retained after all duplications. The conclusion of this analysis is that many genes are maintained after whole-genome duplication not because of functional innovation but because of gene dosage constraints. 相似文献
70.
Muzny DM Scherer SE Kaul R Wang J Yu J Sudbrak R Buhay CJ Chen R Cree A Ding Y Dugan-Rocha S Gill R Gunaratne P Harris RA Hawes AC Hernandez J Hodgson AV Hume J Jackson A Khan ZM Kovar-Smith C Lewis LR Lozado RJ Metzker ML Milosavljevic A Miner GR Morgan MB Nazareth LV Scott G Sodergren E Song XZ Steffen D Wei S Wheeler DA Wright MW Worley KC Yuan Y Zhang Z Adams CQ Ansari-Lari MA Ayele M Brown MJ Chen G Chen Z Clendenning J Clerc-Blankenburg KP Chen R Chen Z Davis C Delgado O Dinh HH Dong W 《Nature》2006,440(7088):1194-1198
After the completion of a draft human genome sequence, the International Human Genome Sequencing Consortium has proceeded to finish and annotate each of the 24 chromosomes comprising the human genome. Here we describe the sequencing and analysis of human chromosome 3, one of the largest human chromosomes. Chromosome 3 comprises just four contigs, one of which currently represents the longest unbroken stretch of finished DNA sequence known so far. The chromosome is remarkable in having the lowest rate of segmental duplication in the genome. It also includes a chemokine receptor gene cluster as well as numerous loci involved in multiple human cancers such as the gene encoding FHIT, which contains the most common constitutive fragile site in the genome, FRA3B. Using genomic sequence from chimpanzee and rhesus macaque, we were able to characterize the breakpoints defining a large pericentric inversion that occurred some time after the split of Homininae from Ponginae, and propose an evolutionary history of the inversion. 相似文献