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1.
A thin sectioning technique involving hand grinding has been developed to produce 20-40-microns-thick sections of bone-titanium implant sites. Components include: 1) surface staining of sections prior to mounting on slides so bone labels (oxytetracycline-HCl and 2,4-bis(N,N-dicarbomethyl)aminomethylfluorescein (DCAF] can be seen in sections viewed with transmitted light, 2) a pneumatic sample press for bonding sections to slides with a thin, uniform glue line and without trapped air bubbles, and 3) bonding methyl methacrylate embedded sections to clear acrylic slides with methyl methacrylate monomer to provide enhanced bond strength and grinding properties compared to those obtainable with glass slides. Sample cracking and distortion is minimized and the tissue-implant interface can be kept intact. The expense of start-up equipment for this technique is minimal. 相似文献
2.
Maintenance of the cellobiose utilization genes of Escherichia coli in a cryptic state 总被引:6,自引:1,他引:5
The genes for cellobiose utilization are normally cryptic in Escherichia
coli. The cellobiose system was used as a model to understand the process
by which silent genes are maintained in microbial populations. Previously
reported was (1) the isolation of a mutant strain that expresses the
cellobiose-utilization (Cel) genes and (2) that expression of those genes
allows utilization of three beta- glucoside sugars: cellobiose, arbutin,
and salicin. The Cel gene cluster has now been cloned from that mutant
strain. In the course of locating the Cel genes within the cloned DNA
segment, it was discovered that inactivation of the Cel-encoded hydrolase
rendered the host strain sensitive to all three beta-glucosides as potent
inhibitors. This sensitivity arises from the accumulation of the
phosphorylated beta- glucosides. Because even the fully active genes
conferred some degree of beta-glucoside sensitivity, the effects of
cellobiose on a series of five Cel+ mutants of independent origin were
investigated. Although each of those strains utilizes cellobiose as a sole
carbon and energy source, cellobiose also acts as a potent inhibitor that
reduces the growth rate on glycerol 2.5-16.5-fold. On the other hand,
wild-type strains that cannot utilize cellobiose are not inhibited. The
observation that the same compound can serve either as a nutrient or as an
inhibitor suggests that, under most conditions in which cellobiose will be
present together with other resources, there is a strong selective
advantage to having the cryptic (Cel0) allele. In those environments in
which cellobiose is the sole, or the best, resource, mutants that express
the genes (Cel+) will have a strong selective advantage. It is suggested
that temporal alternation between these two conditions is a major factor in
the maintenance of these genes in E. coli populations. This alternation of
environments and fitnesses was predicted by the model for cryptic-gene
maintenance that was previously published.
相似文献
3.
Selection-induced mutations are nonrandom mutations that occur as specific
and direct responses to environmental challenge. Examples of
selection-induced mutations have been reported both in bacteria and in
yeast. I previously showed (Hall 1988) that excisions of the mobile genetic
element IS150 from within bglF are selection induced and argued that they
occurred because they were potentially advantageous under the selective
conditions employed. Mittler and Lenski (Mittler and Lenski 1992) have
argued that such excisions are not selection induced but that they occur
randomly in nondividing cells. Here I provide further evidence that IS150
excisions are induced by selection and that the excisions are immediately,
rather than only potentially, advantageous to the cell. I also provide
evidence that excisions, which Mittler and Lenski claim occur randomly in
saturated broth cultures, actually occur after samples from those cultures
are plated onto selective medium.
相似文献
4.
Lysine acetylome profiling uncovers novel histone deacetylase substrate proteins in Arabidopsis 下载免费PDF全文
Paul J Boersema Jan‐Oliver Jost Katharina Kramer Ahmet Bakirbas Julia Sindlinger Magdalena Plöchinger Dario Leister Glen Uhrig Greg BG Moorhead Jürgen Cox Michael E Salvucci Dirk Schwarzer Matthias Mann Iris Finkemeier 《Molecular systems biology》2017,13(10)
Histone deacetylases have central functions in regulating stress defenses and development in plants. However, the knowledge about the deacetylase functions is largely limited to histones, although these enzymes were found in diverse subcellular compartments. In this study, we determined the proteome‐wide signatures of the RPD3/HDA1 class of histone deacetylases in Arabidopsis. Relative quantification of the changes in the lysine acetylation levels was determined on a proteome‐wide scale after treatment of Arabidopsis leaves with deacetylase inhibitors apicidin and trichostatin A. We identified 91 new acetylated candidate proteins other than histones, which are potential substrates of the RPD3/HDA1‐like histone deacetylases in Arabidopsis, of which at least 30 of these proteins function in nucleic acid binding. Furthermore, our analysis revealed that histone deacetylase 14 (HDA14) is the first organellar‐localized RPD3/HDA1 class protein found to reside in the chloroplasts and that the majority of its protein targets have functions in photosynthesis. Finally, the analysis of HDA14 loss‐of‐function mutants revealed that the activation state of RuBisCO is controlled by lysine acetylation of RuBisCO activase under low‐light conditions. 相似文献
5.
José I. Márquez-Corro Santiago Martín-Bravo Pedro Jiménez-Mejías rew L. Hipp Daniel Spalink Robert F. C. Naczi Eric H. Roalson Modesto Luceño Marcial Escudero 《植物分类学报:英文版》2021,59(4):776-790
Changes in holocentric chromosome number due to fission and fusion have direct and immediate effects on genome structure and recombination rates. These, in turn, may influence ecology and evolutionary trajectories profoundly. Sedges of the genus Carex (Cyperaceae) comprise ca. 2000 species with holocentric chromosomes. The genus exhibits a phenomenal range in the chromosome number (2n = 10 − 132) with almost not polyploidy. In this study, we integrated the most comprehensive cytogenetic and phylogenetic data for sedges with associated climatic and morphological data to investigate the hypothesis that high recombination rates are selected when evolutionary innovation is required, using chromosome number evolution as a proxy for recombination rate. We evaluated Ornstein–Uhlenbeck models to infer shifts in chromosome number equilibrium and selective regime. We also tested the relationship between chromosome number and diversification rates. Our analyses demonstrate significant correlations between morphology and climatic niche and chromosome number in Carex. Nevertheless, the amount of chromosomal variation that we are able to explain is very small. We recognized a large number of shifts in mean chromosome number, but a significantly lower number in climatic niche and morphology. We also detected a peak in diversification rates near intermediate recombination rates. In combination, these analyses point toward the importance of chromosome evolution to the evolutionary history of Carex. Our work suggests that the effect of chromosome evolution on recombination rates, not just on reproductive isolation, may be central to the evolutionary history of sedges. 相似文献
6.
Carmen Benítez-Benítez Santiago Martín-Bravo Charlotte S. Bjorå Sebastian Gebauer rew L. Hipp Matthias H. Hoffmann Modesto Luceño Tyril M. Pedersen Anton Reznicek Eric Roalson Polina Volkova Okihito Yano Daniel Spalink Pedro Jiménez-Mejías 《植物分类学报:英文版》2021,59(4):642-667
Carex section Phacocystis (Cyperaceae) is one of the most diverse and taxonomically complex groups of sedges (between 116 and 147 species), with a worldwide distribution in a wide array of biomes. It has a very complicated taxonomic history, with numerous disagreements among different treatments. We studied the biogeography and niche evolution in a phylogenetic framework to unveil the relative contribution of geographical and ecological drivers to diversification of the group. We used a large species sampling of the section (82% of extant species) to build a phylogeny based on four DNA regions, constrained with a phylogenomic HybSeq tree and dated with six fossil calibrations. Our phylogenetic results recovered section Phacocystis s.s. (core Phacocystis) as sister to section Praelongae. Ancestral area reconstruction points toward the N Pacific as the cradle for the crown diversification of section Phacocystis during the Middle Miocene. Wide distributions were recurrently inferred across deep nodes. Large Northern Hemisphere lineages with geographical congruence were retrieved, pointing toward the importance of allopatric divergence at deep phylogenetic levels, whereas within-area speciation emerges as the predominant pattern at shallow phylogenetic level. The Southern Hemisphere (Neotropics, SW Pacific) was colonized several times from the Northern Hemisphere. The global expansion of Carex section Phacocystis did not entail major ecological changes along the inner branches of the phylogeny. Nevertheless, ecological differentiation seems to gain importance toward recent times. 相似文献
7.
Katarina Stingl Karl Ulrich Bartz-Schmidt Dorothea Besch Angelika Braun Anna Bruckmann Florian Gekeler Udo Greppmaier Stephanie Hipp Gernot H?rtd?rfer Christoph Kernstock Assen Koitschev Akos Kusnyerik Helmut Sachs Andreas Schatz Krunoslav T. Stingl Tobias Peters Barbara Wilhelm Eberhart Zrenner 《Proceedings. Biological sciences / The Royal Society》2013,280(1757)
This study aims at substituting the essential functions of photoreceptors in patients who are blind owing to untreatable forms of hereditary retinal degenerations. A microelectronic neuroprosthetic device, powered via transdermal inductive transmission, carrying 1500 independent microphotodiode-amplifier-electrode elements on a 9 mm2 chip, was subretinally implanted in nine blind patients. Light perception (8/9), light localization (7/9), motion detection (5/9, angular speed up to 35 deg s−1), grating acuity measurement (6/9, up to 3.3 cycles per degree) and visual acuity measurement with Landolt C-rings (2/9) up to Snellen visual acuity of 20/546 (corresponding to decimal 0.037 or corresponding to 1.43 logMAR (minimum angle of resolution)) were restored via the subretinal implant. Additionally, the identification, localization and discrimination of objects improved significantly (n = 8; p < 0.05 for each subtest) in repeated tests over a nine-month period. Three subjects were able to read letters spontaneously and one subject was able to read letters after training in an alternative-force choice test. Five subjects reported implant-mediated visual perceptions in daily life within a field of 15° of visual angle. Control tests were performed each time with the implant''s power source switched off. These data show that subretinal implants can restore visual functions that are useful for daily life. 相似文献
8.
Avi Z. Rosenberg Michael D. Armani Patricia A. Fetsch Liqiang Xi Tina Thu Pham Mark Raffeld Yun Chen Neil O’Flaherty Rebecca Stussman Adele R. Blackler Qiang Du Jeffrey C. Hanson Mark J. Roth Armando C. Filie Michael H. Roh Michael R. Emmert-Buck Jason D. Hipp Michael A. Tangrea 《PloS one》2016,11(3)
9.
Alexis R. Sullivan Sandra A. Owusu Jaime A. Weber Andrew L. Hipp Oliver Gailing 《Botanical journal of the Linnean Society. Linnean Society of London》2016,181(1):99-114
Oaks (Quercus: Fagaceae) commonly interbreed yet retain their morphological, genetic and ecological distinctiveness. Post‐zygotic isolation mechanisms, such as ecologically dependent selection on adaptive loci, may therefore limit introgression. To test this hypothesis, we quantified hybridization and genetic divergence across the contact zone of four red oaks (Quercus section Lobatae) in the Great Lakes region of North America using a suite of 259 amplified fragment length polymorphisms and 27 genic and genomic microsatellite markers. First, we identified hybrids using genetic structure analysis and confirmed the reliability of our assignments via simulations. Then, we identified candidate loci for species maintenance with three complementary tests for selection and obtained partial gene sequences linked to an outlier locus and three other loci. We detected evidence of recent hybridization among all species and considerable gene flow between Q. ellipsoidalis and Q. velutina. Overall, c. 20% of Q. velutina had recent ancestry from Q. ellipsoidalis, whereas nearly 30% of Q. ellipsoidalis had a Q. velutina ancestor. Most loci were negligibly to weakly differentiated among species, but two gene‐linked microsatellites deviated significantly from neutral expectations in multiple, complementary outlier tests. Both outlier loci were located in the same 15‐cM bin on an existing Q. robur linkage map, a region under divergent selection in other oak species. Adaptive loci in this highly differentiated genomic region may contribute to ecological divergence among species and limit introgression. 相似文献
10.
Belfer I Hipp H Bollettino A McKnight C Evans C Virkkunen M Albaugh B Max MB Goldman D Enoch MA 《Genes, Brain & Behavior》2007,6(5):473-481
The neuropeptide galanin is widely expressed in the periphery and the central nervous system and mediates diverse physiological processes and behaviors including alcohol abuse, depression and anxiety. Four genes encoding galanin and its receptors have been identified (GAL, GALR1, GALR2 and GALR3). Recently we found that GAL haplotypes were associated with alcoholism, raising the possibility that genetic variation in GALR1, GALR2 and GALR3 might also alter alcoholism risk. Tag single nucleotide polymorphisms (SNPs) were identified by genotyping SNP panels in controls from five populations. For the association study with alcoholism, six GALR1, four GALR2 and four GALR3 SNPs were genotyped in a large cohort of Finnish alcoholics and non-alcoholics. GALR3 showed a significant association with alcoholism that was driven by one SNP (rs3,091,367). Moreover, the combination of the GALR3 rs3,091,367 risk allele and GAL risk haplotypes led to a modestly increased odds ratio (OR) for alcoholism (2.4) as compared with the effect of either GAL (1.9) or GALR3 alone (1.4). Likewise, the combination of the GALR3 and GAL risk diplotypes led to an increased OR for alcoholism (4.6) as compared with the effect of either GAL (2.0) or GALR3 alone (1.6). There was no effect of GALR1 or GALR2 on alcoholism risk. This evidence suggests that GALR3 mediates the alcoholism-related actions of galanin. 相似文献