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101.
102.
Williams TJ Lauro FM Ertan H Burg DW Poljak A Raftery MJ Cavicchioli R 《Environmental microbiology》2011,13(8):2186-2203
The growth of all microorganisms is limited to a specific temperature range. However, it has not previously been determined to what extent global protein profiles change in response to temperatures that incrementally span the complete growth temperature range of a microorganism. As a result it has remained unclear to what extent cellular processes (inferred from protein abundance profiles) are affected by growth temperature and which, in particular, constrain growth at upper and lower temperature limits. To evaluate this, 8-plex iTRAQ proteomics was performed on the Antarctic microorganism, Methanococcoides burtonii. Methanococcoides burtonii was chosen due to its importance as a model psychrophilic (cold-adapted) member of the Archaea, and the fact that proteomic methods, including subcellular fractionation procedures, have been well developed. Differential abundance patterns were obtained for cells grown at seven different growth temperatures (-2°C, 1°C, 4°C, 10°C, 16°C, 23°C, 28°C) and a principal component analysis (PCA) was performed to identify trends in protein abundances. The multiplex analysis enabled three largely distinct physiological states to be described: cold stress (-2°C), cold adaptation (1°C, 4°C, 10°C and 16°C), and heat stress (23°C and 28°C). A particular feature of the thermal extremes was the synthesis of heat- and cold-specific stress proteins, reflecting the important, yet distinct ways in which temperature-induced stress manifests in the cell. This is the first quantitative proteomic investigation to simultaneously assess the response of a microorganism to numerous growth temperatures, including the upper and lower growth temperatures limits, and has revealed a new level of understanding about cellular adaptive responses. 相似文献
103.
Pilak O Harrop SJ Siddiqui KS Chong K De Francisci D Burg D Williams TJ Cavicchioli R Curmi PM 《Environmental microbiology》2011,13(8):2232-2249
Archaea are abundant in permanently cold environments. The Antarctic methanogen, Methanococcoides burtonii, has proven an excellent model for studying molecular mechanisms of cold adaptation. Methanococcoides burtonii contains three group II chaperonins that diverged prior to its closest orthologues from mesophilic Methanosarcina spp. The relative abundance of the three chaperonins shows little dependence on organism growth temperature, except at the highest temperatures, where the most thermally stable chaperonin increases in abundance. In vitro and in vivo, the M. burtonii chaperonins are predominantly monomeric, with only 23-33% oligomeric, thereby differing from other archaea where an oligomeric ring form is dominant. The crystal structure of an N-terminally truncated chaperonin reveals a monomeric protein with a fully open nucleotide binding site. When compared with closed state group II chaperonin structures, a large-scale ≈ 30° rotation between the equatorial and intermediate domains is observed resulting in an open nucleotide binding site. This is analogous to the transition observed between open and closed states of group I chaperonins but contrasts with recent archaeal group II chaperonin open state ring structures. The predominance of monomeric form and the ability to adopt a fully open nucleotide site appear to be unique features of the M. burtonii group II chaperonins. 相似文献
104.
Baeumlisberger D Rohmer M Arrey TN Mueller BF Beckhaus T Bahr U Barka G Karas M 《Journal of proteome research》2011,10(6):2889-2894
The beneficial effect of high mass accuracy in mass spectrometry is especially pronounced when using less specific enzymes as the number of theoretically possible peptides increases dramatically without any cleavage specificity defined. Together with a preceding chromatographic separation, high-resolution mass spectrometers such as the MALDI-LTQ-Orbitrap are therefore well suited for the analysis of protein digests with less specific enzymes. A combination with fast, automated, and informative MALDI-TOF/TOF analysis has already been shown to yield increased total peptide and protein identifications. Here, a simple method for nLC separation and subsequent alternating spotting on two targets for both a MALDI-LTQ-Orbitrap and a MALDI-TOF/TOF instrument is introduced. This allows for simultaneous measurements on both instruments and subsequent combination of both data sets by an in-house written software tool. The performance of this procedure was evaluated using a mixture of four standard proteins digested with elastase. Three replicate runs were examined concerning repeatability and the total information received from both instruments. A cytosolic extract of C. glutamicum was used to demonstrate the applicability to more complex samples. Database search results showed that an additional 32.3% of identified peptides were found using combined data sets in comparison to MALDI-TOF/TOF data sets. 相似文献
105.
Bier C Knauer SK Docter D Schneider G Krämer OH Stauber RH 《Traffic (Copenhagen, Denmark)》2011,12(6):703-714
Taspase1 is a threonine protease suspected to process (patho)biologically relevant nuclear and cytoplasmic substrates, such as the mixed lineage leukemia protein. However, neither the mechanisms regulating Taspase1's intracellular localization nor their functional consequences are known. Analysis of endogenous and ectopically expressed Taspase1 detected the protease predominantly in the nucleus accumulating at the nucleolus. Microinjection and ectopic expression studies identified an evolutionarily conserved bipartite nuclear import signal (NLS) (amino acids (197) KRNKRKLELA ERVDTDFMQLKKRR(220) ) interacting with importin-α. Notably, an NLS-mutated, import-deficient Taspase1 was biologically inactive. Although the NLS conferred nuclear transport already of the proenzyme, Taspase1's nucleolar localization required its autoproteolytic processing, triggering its interaction with the nucleolar shuttle protein nucleophosmin. In contrast, (auto)catalytically inactive Taspase1 mutants neither accumulated at the nucleolus nor bound nucleophosmin. Active nuclear import and interaction with nucleophosmin was found to be required for the formation of proteolytically active Taspase1 ensuring to efficiently process its nuclear targets. Intriguingly, coexpression of pathological nucleophosmin variants increased the amount of cytoplasmic Taspase1. Hence, Taspase1 appears to exploit the nuclear export activity of nucleophosmin to gain transient access to the cytoplasm required to also cleave its cytoplasmic substrates. Collectively, we here describe a hitherto unknown mechanism regulating the biological activity of this protease. 相似文献
106.
Scott D. Tiegs Peter S. Levi Janine Rüegg Dominic T. Chaloner Jennifer L. Tank Gary A. Lamberti 《Ecosystems》2011,14(4):598-614
We tested the hypothesis that the carcasses of anadromous Pacific salmon (Oncorhynchus spp.) constitute a significant source of nutrients in the nutrient-poor freshwaters where these fish migrate, spawn, senesce,
and die. In a 110 m-long stream reach in Southeast Alaska, we retained nearly 3000 salmon carcasses and compared streamwater
nitrogen (N), phosphorus (P), and the biomass of benthic biofilm in this reach with an upstream reference reach. The study
spanned 5 months, bracketed the entire salmon run, and encompassed significant seasonal variation in abiotic stream conditions.
Concentrations of dissolved and particulate N and P followed distinctly unimodal patterns through time, which tracked the
abundance of live salmon, and we observed strong predictive relationships between live-salmon abundance and streamwater-nutrient
concentrations. In contrast, we did not observe clear relationships between salmon carcasses and streamwater nutrients. Biofilm
biomass within our study reaches seemed to more closely track the abundance of live salmon than the abundance of carcasses.
The experimental retention of carcasses had a minor or undetectable influence on nutrient concentrations and biofilm within
the study reach as compared to the reference reach. We conclude that physical factors such as temperature, discharge, nutrient
limitation, and irradiance vary seasonally in ways that maximize the influence of nutrients provisioned by live salmon and
minimize the influence of carcass-derived nutrients on the aspects of stream ecosystems that we examined. Overall, our results
promote a new perspective on the ecological role of salmon in freshwaters, and contribute to a more mechanistic understanding
of how migratory fishes can influence aquatic ecosystems. 相似文献
107.
Olszak AM van Essen D Pereira AJ Diehl S Manke T Maiato H Saccani S Heun P 《Nature cell biology》2011,13(7):799-808
108.
109.
We previously reported that global deletion of insulin receptor substrate protein 1 (Irs1) extends lifespan and increases resistance to several age-related pathologies in female mice. However, no effect on lifespan was observed in male Irs1 null mice. We suggested at the time that the lack of any effect in males might have been due to a sample size issue. While such lifespan studies are essential to our understanding of the aging process, they are generally based on survival curves derived from single experiments, primarily due to time and economic constraints. Consequently, the robustness of such findings as a basis for further investigation has been questioned. We have therefore measured lifespan in a second, separate cohort of Irs1 null female mice, and show that, consistent with our previous finding, global deletion of Irs1 significantly extends lifespan in female mice. In addition, an augmented and completed study demonstrates lifespan extension in male Irs1 null mice. Therefore, we show that reduced IRS1-dependent signalling is a robust mechanism through which mammalian lifespan can be modulated. 相似文献
110.
Ducimetière F Lurkin A Ranchère-Vince D Decouvelaere AV Péoc'h M Istier L Chalabreysse P Muller C Alberti L Bringuier PP Scoazec JY Schott AM Bergeron C Cellier D Blay JY Ray-Coquard I 《PloS one》2011,6(8):e20294