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91.
Reti NG Lappas M Huppertz B Riley C Wlodek ME Henschke P Permezel M Rice GE 《Cell and tissue research》2007,328(3):607-616
Ex situ culture of human gestational tissues has been routinely used as a model to investigate tissue function. The objective of
this study was to determine the effect of varying oxygen concentrations on human term placental explants over a 24-h time
period. Specifically, the effect of incubating placental explants in oxygen concentrations of 8%, 21% or 95% on tissue viability,
metabolism and cell death was measured by assessing glucose consumption, lactate production, release of lactate dehydrogenase,
parathyroid hormone-related protein (PTHrP), tumour necrosis factor-alpha (TNF-α) and 8-isoprostane, immunoreactivity for
cleaved-caspase-9 and immunohistochemistry for the caspase-3-cleaved cytokeratin-18 neoepitope, M30. Exposure to higher oxygen
concentrations significantly increased the rates of glucose consumption and lactate production. Apoptosis was significantly
increased under conditions of higher oxygen as evidenced by increased M30 in placental explant sections. Similarly, hyperoxia
significantly increased the releases of PTHrP, TNF-α and 8-isoprostane. Thus, incubation of placental explants with oxygen
concentrations of 95% and, to a lesser extent, 21% oxygen was associated with the modulation of multiple cellular response
pathways including those associated with tissue viability and cell death. These data are consistent with the hypothesis that
hyperoxia activates pathways and mechanisms involved in cellular metabolism, necrosis and apoptosis, thereby shifting the
balance from a steady state towards cell death. 相似文献
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93.
Melanie J Carvell Phil J Marsh Shanta J Persaud Peter M Jones 《Cellular physiology and biochemistry》2007,20(5):617-626
Islet function is dependent on cells within the islet interacting with each other. E-cadherin (ECAD) mediates Ca(2+)-dependent homophilic cell adhesion between b-cells within islets and has been identified as a tumour suppressor. We generated clones of the MIN6 beta-cell line that stably over- (S) and under-express (alphaS) ECAD. Modified expression of ECAD was confirmed by quantitative RT-PCR, immunoblotting and immunocytochemistry. Preproinsulin mRNA, insulin content and basal rates of insulin secretion were higher in S cells compared to aS and control (V) cells. However, stimulated insulin secretory responses were unaffected by ECAD expression levels. ECAD expression did affect proliferation, with enhanced ECAD expression being associated with reduced proliferation and vice versa. Formation of islet-like structures was associated with a significant reduction in proliferation of V and S cells but not alphaS cells. These data suggest that ECAD expression levels do not modulate insulin secretory function but are consistent with a role for ECAD in the regulation of beta-cell proliferation. 相似文献
94.
Lin SP Coan P da Rocha ST Seitz H Cavaille J Teng PW Takada S Ferguson-Smith AC 《Development (Cambridge, England)》2007,134(2):417-426
Genomic imprinting is an epigenetic mechanism controlling parental-origin-specific gene expression. Perturbing the parental origin of the distal portion of mouse chromosome 12 causes alterations in the dosage of imprinted genes resulting in embryonic lethality and developmental abnormalities of both embryo and placenta. A 1 Mb imprinted domain identified on distal chromosome 12 contains three paternally expressed protein-coding genes and multiple non-coding RNA genes, including snoRNAs and microRNAs, expressed from the maternally inherited chromosome. An intergenic, parental-origin-specific differentially methylated region, the IG-DMR, which is unmethylated on the maternally inherited chromosome, is necessary for the repression of the paternally expressed protein-coding genes and for activation of the maternally expressed non-coding RNAs: its absence causes the maternal chromosome to behave like the paternally inherited one. Here, we characterise the developmental consequences of this epigenotype switch and compare these with phenotypes associated with paternal uniparental disomy of mouse chromosome 12. The results show that the embryonic defects described for uniparental disomy embryos can be attributed to this one cluster of imprinted genes on distal chromosome 12 and that these defects alone, and not the mutant placenta, can cause prenatal lethality. In the placenta, the absence of the IG-DMR has no phenotypic consequence. Loss of repression of the protein-coding genes occurs but the non-coding RNAs are not repressed on the maternally inherited chromosome. This indicates that the mechanism of action of the IG-DMR is different in the embryo and the placenta and suggests that the epigenetic control of imprinting differs in these two lineages. 相似文献
95.
Gu Y Wu SL Meyer JL Hancock WS Burg LJ Linder J Hanlon DW Karger BL 《Journal of proteome research》2007,6(11):4256-4268
The purpose of this discovery phase study was to identify candidate protein biomarkers for high-grade dysplastic cervical cells using mass spectrometry. Laser Capture Microdissection (LCM) was utilized to isolate high-grade dysplastic and normal cells from ThinPrep slides prepared from cervical cytological specimens. Following cell capture, samples were solubilized and proteins separated by gel electrophoresis in preparation for enzymatic digestion and liquid chromatography mass spectrometry analysis (LC-MS). Processed samples were subsequently analyzed using a linear ion trap coupled with a Fourier transform mass spectrometer (LTQ-FT MS). It was determined that both PreservCyt Solution and ThinPrep Pap Stain (Cytyc Corporation) were compatible with the sample processing and LC-MS analysis. In total, from 9 normal and 9 abnormal cervical cytological specimens, more than 1000 unique proteins were identified with high confidence, based on approximately 12,000 captured cells per specimen. Quantitative protein differences between HSIL (High-Grade Squamous Intraepithelial Lesion) and NILM (Negative for Intraepithelial Lesions or Malignancy) samples were determined by comparing the intensities of the representative (label-free) peptide ions. More than 200 proteins were found to exhibit a 3-fold difference in protein level. Interestingly, significant up-regulation of nuclear and mitochondrial proteins in HSIL specimens was noted. In several cases, the increased protein abundance observed in high-grade cells, as determined by quantitative LC-MS, was validated by immunocytochemical methods using ThinPrep cervical specimens. With the study of additional clinical specimens, the differential abundance of proteins in high-grade dysplastic cells versus morphologically normal cervical cells may lead to validated novel biomarkers for cervical disease. 相似文献
96.
97.
Testing assumptions of central place foraging theory: a study of Adélie penguins Pygoscelis adeliae in the Ross Sea
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R. Glenn Ford David G. Ainley Amelie Lescroël Phil O'B. Lyver Viola Toniolo Grant Ballard 《Journal of avian biology》2015,46(2):193-205
We investigated central place foraging (CPF) in the context of optimal foraging theory in Adélie penguins Pygoscelis adeliae of the southern Ross Sea by using satellite tracking and time‐depth recorders to explore foraging at two spatio‐temporal scales: within the day‐to‐day (sub‐mesoscale: single foraging trip, 10s of km2) and the entire breeding season (mesoscale: trips by multiple individuals across the collective foraging area, 100s of km2). Specifically, we examine whether three basic assumptions of the Orians–Pearson CPF model, shown to occur in other CPF species, are met: 1) within a patch, the rate of prey acquisition declines with time spent in that patch; 2) food is distributed in discrete patches and is not available between those patches; and 3) CPF species have knowledge of the potential (or average, at least) feeding rate within their universe of patches, and use this knowledge to determine their foraging strategy when planning or engaging in a foraging trip. We found that prey consumption rates did not decline with time spent in patches, and penguins foraged to some degree most of the time when at sea. Food availability, as measured by foraging dive rate, appeared to be predictable within the same day at the same location, but predictability broke down after 2 d at distances > 10 km away. We conclude that the assumptions of the Orians–Pearson CPF model are not a good fit to the circumstances of Ross Sea penguins, which clearly are central place foragers. 相似文献
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100.
Small, isolated populations are prone to genetic drift and high levels of inbreeding that can threaten their long-term survival.
Alnus maritima persists exclusively in three groups of small, highly disjunct, regional populations in the Delmarva Peninsula, Georgia,
and Oklahoma. Trees in the three regions are recognized as separate subspecies. Microsatellite markers were used to measure
fine-scale population genetic diversity and structure (1) within and among regions and (2) within and among populations in
each region. Compared to a previous study utilizing allozymes, microsatellite data show higher levels of variation, lower
levels of inbreeding, but similar levels of genetic differentiation among regions. Significant genetic differentiation was
detected among regions and among distinct populations within regions. Genetic differentiation was significantly correlated
with geographic distance among regional populations, but not among populations within regions. Populations, therefore, likely
represent fragments of formerly extensive networks of populations that have decayed and retracted due to competition with
other species better adapted to the shadier habitats of late-succession environments. The unique genetic features of populations
within different regions should be considered as part of future conservation efforts. 相似文献