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81.
Edward S. Grew Jeffrey L. Bada Robert M. Hazen 《Origins of life and evolution of the biosphere》2011,41(4):307-316
The RNA World is generally thought to have been an important link between purely prebiotic (>3.7 Ga) chemistry and modern
DNA/protein biochemistry. One concern about the RNA World hypothesis is the geochemical stability of ribose, the sugar moiety
of RNA. Prebiotic stabilization of ribose by solutions associated with borate minerals, notably colemanite, ulexite, and kernite,
has been proposed as one resolution to this difficulty. However, a critical unresolved issue is whether borate minerals existed
in sufficient quantities on the primitive Earth, especially in the period when prebiotic synthesis processes leading to RNA
took place. Although the oldest reported colemanite and ulexite are 330 Ma, and the oldest reported kernite, 19 Ma, boron
isotope data and geologic context are consistent with an evaporitic borate precursor to 2400-2100 Ma borate deposits in the
Liaoning and Jilin Provinces, China, as well as to tourmaline-group minerals at 3300–3450 Ma in the Barberton belt, South
Africa. The oldest boron minerals for which the age of crystallization could be determined are the metamorphic tourmaline
species schorl and dravite in the Isua complex (metamorphism between ca. 3650 and ca. 3600 Ma). Whether borates such as colemanite,
ulexite and kernite were present in the Hadean (>4000 Ma) at the critical juncture when prebiotic molecules such as ribose
required stabilization depends on whether a granitic continental crust had yet differentiated, because in its absence we see
no means for boron to be sufficiently concentrated for borates to be precipitated. 相似文献
82.
Mariana A Antunes Soraia C Abreu Fernanda F Cruz Ana Clara Teixeira Miquéias Lopes-Pacheco Elga Bandeira Priscilla C Olsen Bruno L Diaz Christina M Takyia Isalira PRG Freitas Nazareth N Rocha Vera L Capelozzi Débora G Xisto Daniel J Weiss Marcelo M Morales Patricia RM Rocco 《Respiratory research》2014,15(1)
We sought to assess whether the effects of mesenchymal stromal cells (MSC) on lung inflammation and remodeling in experimental emphysema would differ according to MSC source and administration route. Emphysema was induced in C57BL/6 mice by intratracheal (IT) administration of porcine pancreatic elastase (0.1 UI) weekly for 1 month. After the last elastase instillation, saline or MSCs (1×105), isolated from either mouse bone marrow (BM), adipose tissue (AD) or lung tissue (L), were administered intravenously (IV) or IT. After 1 week, mice were euthanized. Regardless of administration route, MSCs from each source yielded: 1) decreased mean linear intercept, neutrophil infiltration, and cell apoptosis; 2) increased elastic fiber content; 3) reduced alveolar epithelial and endothelial cell damage; and 4) decreased keratinocyte-derived chemokine (KC, a mouse analog of interleukin-8) and transforming growth factor-β levels in lung tissue. In contrast with IV, IT MSC administration further reduced alveolar hyperinflation (BM-MSC) and collagen fiber content (BM-MSC and L-MSC). Intravenous administration of BM- and AD-MSCs reduced the number of M1 macrophages and pulmonary hypertension on echocardiography, while increasing vascular endothelial growth factor. Only BM-MSCs (IV > IT) increased the number of M2 macrophages. In conclusion, different MSC sources and administration routes variably reduced elastase-induced lung damage, but IV administration of BM-MSCs resulted in better cardiovascular function and change of the macrophage phenotype from M1 to M2. 相似文献
83.
Diana M. Shih Zeneng Wang Richard Lee Yonghong Meng Nam Che Sarada Charugundla Hannah Qi Judy Wu Calvin Pan J. Mark Brown Thomas Vallim Brian J. Bennett Mark Graham Stanley L. Hazen Aldons J. Lusis 《Journal of lipid research》2015,56(1):22-37
We performed silencing and overexpression studies of flavin containing monooxygenase (FMO) 3 in hyperlipidemic mouse models to examine its effects on trimethylamine N-oxide (TMAO) levels and atherosclerosis. Knockdown of hepatic FMO3 in LDL receptor knockout mice using an antisense oligonucleotide resulted in decreased circulating TMAO levels and atherosclerosis. Surprisingly, we also observed significant decreases in hepatic lipids and in levels of plasma lipids, ketone bodies, glucose, and insulin. FMO3 overexpression in transgenic mice, on the other hand, increased hepatic and plasma lipids. Global gene expression analyses suggested that these effects of FMO3 on lipogenesis and gluconeogenesis may be mediated through the PPARα and Kruppel-like factor 15 pathways. In vivo and in vitro results were consistent with the concept that the effects were mediated directly by FMO3 rather than trimethylamine/TMAO; in particular, overexpression of FMO3 in the human hepatoma cell line, Hep3B, resulted in significantly increased glucose secretion and lipogenesis. Our results indicate a major role for FMO3 in modulating glucose and lipid homeostasis in vivo, and they suggest that pharmacologic inhibition of FMO3 to reduce TMAO levels would be confounded by metabolic interactions. 相似文献
84.
Enzyme activities of aerobic lignocellulolytic bacteria isolated from wet tropical forest soils 总被引:1,自引:0,他引:1
Hannah L. Woo Terry C. Hazen Blake A. Simmons Kristen M. DeAngelis 《Systematic and applied microbiology》2014
Lignocellulolytic bacteria have promised to be a fruitful source of new enzymes for next-generation lignocellulosic biofuel production. Puerto Rican tropical forest soils were targeted because the resident microbes decompose biomass quickly and to near-completion. Isolates were initially screened based on growth on cellulose or lignin in minimal media. 75 Isolates were further tested for the following lignocellulolytic enzyme activities: phenol oxidase, peroxidase, β-d-glucosidase, cellobiohydrolase, β-xylopyranosidase, chitinase, CMCase, and xylanase. Cellulose-derived isolates possessed elevated β-d-glucosidase, CMCase, and cellobiohydrolase activity but depressed phenol oxidase and peroxidase activity, while the contrary was true of lignin isolates, suggesting that these bacteria are specialized to subsist on cellulose or lignin. Cellobiohydrolase and phenol oxidase activity rates could classify lignin and cellulose isolates with 61% accuracy, which demonstrates the utility of model degradation assays. Based on 16S rRNA gene sequencing, all isolates belonged to phyla dominant in the Puerto Rican soils, Proteobacteria, Firmicutes, and Actinobacteria, suggesting that many dominant taxa are capable of the rapid lignocellulose degradation characteristic of these soils. The isolated genera Aquitalea, Bacillus, Burkholderia, Cupriavidus, Gordonia, and Paenibacillus represent rarely or never before studied lignolytic or cellulolytic species and were undetected by metagenomic analysis of the soils. The study revealed a relationship between phylogeny and lignocellulose-degrading potential, supported by Kruskal–Wallis statistics which showed that enzyme activities of cultivated phyla and genera were different enough to be considered representatives of distinct populations. This can better inform future experiments and enzyme discovery efforts. 相似文献
85.
86.
Cryoprotection of antibody by organic solutes and organic solute/divalent cation mixtures 总被引:1,自引:0,他引:1
Antibodies are globular glycoproteins that protect animals from microbial and toxic insult. These proteins have proven to have substantial commercial and research value but are variably susceptible to freeze-thaw damage, thus limiting their usefulness. Several carbohydrates and divalent cations were examined alone and in combination to determine whether they could protect antibody from freeze-thaw damage. The amino acid proline was also tested. Two antibodies, derived from different sources and specific for different antigens, were tested by a direct enzyme-linked immunosorbent assay (ELISA). Confirmation of antibody freeze-lability was obtained by rocket electrophoresis and radial immunodiffusion tests. Neither carbohydrate nor divalent cation alone fully protected antibody activity from freeze-thaw damage. However, several combinations protected antibody activity completely when compared to their effect on antibody maintained at room temperature. In the case of affinity-purified antibody, full protection of antibody activity relative to an untreated control was obtained. In several instances, cryoprotection of antibody by solute-divalent cation combinations was synergistic and not an additive effect of each component. Alkaline phosphatase, an enzyme typically linked to antibody for an ELISA, was not freeze-thaw labile. These results indicate that antibody function can be fully protected from damage due to freeze-thaw treatment by organic solutes in combination with divalent cations. 相似文献
87.
88.
Budding yeast Rif1 binds to replication origins and protects DNA at blocked replication forks
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Shin‐ichiro Hiraga Chandre Monerawela Yuki Katou Sophie Shaw Kate RM Clark Katsuhiko Shirahige Anne D Donaldson 《EMBO reports》2018,19(9)
Despite its evolutionarily conserved function in controlling DNA replication, the chromosomal binding sites of the budding yeast Rif1 protein are not well understood. Here, we analyse genome‐wide binding of budding yeast Rif1 by chromatin immunoprecipitation, during G1 phase and in S phase with replication progressing normally or blocked by hydroxyurea. Rif1 associates strongly with telomeres through interaction with Rap1. By comparing genomic binding of wild‐type Rif1 and truncated Rif1 lacking the Rap1‐interaction domain, we identify hundreds of Rap1‐dependent and Rap1‐independent chromosome interaction sites. Rif1 binds to centromeres, highly transcribed genes and replication origins in a Rap1‐independent manner, associating with both early and late‐initiating origins. Interestingly, Rif1 also binds around activated origins when replication progression is blocked by hydroxyurea, suggesting association with blocked forks. Using nascent DNA labelling and DNA combing techniques, we find that in cells treated with hydroxyurea, yeast Rif1 stabilises recently synthesised DNA. Our results indicate that, in addition to controlling DNA replication initiation, budding yeast Rif1 plays an ongoing role after initiation and controls events at blocked replication forks. 相似文献
89.
JW Santo Domingo J C Radway E W Wilde P Hermann T C Hazen 《Journal of industrial microbiology & biotechnology》1997,18(6):389-395
Immobilization of the trichloroethylene-degrading bacterium Burkholderia cepacia was evaluated using hydrophilic polyurethane foam. The influence of several foam formulation parameters upon cell retention
was examined. Surfactant type was a major determinant of retention; a lecithin-based compound retained more cells than pluronic-
or silicone-based surfactants. Excessive amounts of surfactant led to increased washout of bacteria. Increasing the biomass
concentration in the foam from 4.8 to 10.5% dry weight per wet weight of foam resulted in fewer cells being washed out. Embedding
at reduced temperature did not significantly affect retention, while the use of a silane binding agent gave inconsistent
results. The optimal formulation retained all but 0.2% of total embedded cells during passage of 2 L of water through columns
containing 2 g of foam. All foam formulations tested reduced the culturability of embedded cells by several orders of magnitude,
but O2 consumption and CO2 evolution rates of embedded cells were never less than 50% of those of free cells. Nutrient amendments stimulated an increase
in cell volume and ribosomal activity in immobilized cells as indicated by hybridization studies using fluorescently labeled
ribosomal probes. These results indicate that, although immobilized cells were mostly nonculturable, they were metabolically
active and thus could be used for biodegradation of toxic compounds.
Received 23 December 1996/ Accepted in revised form 13 March 1997 相似文献
90.
Evolution of eutherian cytochrome c oxidase subunit II: heterogeneous rates of protein evolution and altered interaction with cytochrome c 总被引:3,自引:1,他引:2
Cytochrome c oxidase subunit II (COII), encoded by the mitochondrial
genome, exhibits one of the most heterogeneous rates of amino acid
replacement among placental mammals. Moreover, it has been demonstrated
that cytochrome c oxidase has undergone a structural change in higher
primates which has altered its physical interaction with cytochrome c. We
collected a large data set of COII sequences from several orders of mammals
with emphasis on primates, rodents, and artiodactyls. Using phylogenetic
hypotheses based on data independent of the COII gene, we demonstrated that
an increased number of amino acid replacements are concentrated among
higher primates. Incorporating approximate divergence dates derived from
the fossil record, we find that most of the change occurred independently
along the New World monkey lineage and in a rapid burst before apes and Old
World monkeys diverged. There is some evidence that Old World monkeys have
undergone a faster rate of nonsynonymous substitution than have apes. Rates
of substitution at four-fold degenerate sites in primates are relatively
homogeneous, indicating that the rate heterogeneity is restricted to
nondegenerate sites. Excluding the rate acceleration mentioned above,
primates, rodents, and artiodactyls have remarkably similar nonsynonymous
replacement rates. A different pattern is observed for transversions at
four-fold degenerate sites, for which rodents exhibit a higher rate of
replacement than do primates and artiodactyls. Finally, we hypothesize
specific amino acid replacements which may account for much of the
structural difference in cytochrome c oxidase between higher primates and
other mammals.
相似文献