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971.
Plant Growth Regulators and Induction of Leaf Senescence in Nitrogen-Deprived Wheat Plants 总被引:1,自引:0,他引:1
M. Victoria Criado Irma N. Roberts Mariela Echeverria Atilio J. Barneix 《Journal of Plant Growth Regulation》2007,26(4):301-307
The sequence of events and the signals that regulate the remobilization of nitrogen (N) reserves during senescence induced
by N starvation were studied in leaf 3, the last fully expanded leaf, in 17-day-old wheat (Triticum aestivum L.) plants. The first event observed was a rapid decrease in the isopentenyl adenosine (iPA) concentration during the first
24 h of N starvation. No differences in t-zeatin riboside and dihydrozeatin riboside concentrations were observed until the
end of the assay. During the following 6 days, a decrease in soluble amino acids, chlorophyll, and protein, as well as an
increase in soluble sugar concentration and endoproteolytic activity, could be observed. At day 3 of the experiment, the abscisic
acid (ABA) concentration in the leaves of N-deprived plants started to increase. After 6 days of N deprivation there was a
rise in oxidative stress, as indicated by the increase in malondialdehyde concentration, as well as a decrease in the activities
of antioxidant enzymes catalase and ascorbate peroxidase. To analyze interactions with leaf development, the first, second,
third, and fourth leaves were studied. iPA concentration decreased in all the leaf stages, including leaf 4, which was not
fully expanded. A linear correlation between iPA and protein concentration was determined. These results suggest that the
sharp fall in iPA could be the earliest event that induces protein degradation during the development of senescence induced
by N deficiency, and that only later is ABA accumulated and oxidative stress developed. 相似文献
972.
Baumann K Perez-Rodriguez M Bradley D Venail J Bailey P Jin H Koes R Roberts K Martin C 《Development (Cambridge, England)》2007,134(9):1691-1701
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976.
Brian S. Roberts Andrew A. Hardigan Marie K. Kirby Meredith B. Fitz-Gerald C.?Mel Wilcox Robert P. Kimberly Richard M. Myers 《Nucleic acids research》2015,43(21):e145
Highly abundant microRNAs (miRNAs) in small RNA sequencing libraries make it difficult to obtain efficient measurements of more lowly expressed species. We present a new method that allows for the selective blocking of specific, abundant miRNAs during preparation of sequencing libraries. This technique is specific with little off-target effects and has no impact on the reproducibility of the measurement of non-targeted species. In human plasma samples, we demonstrate that blocking of highly abundant hsa-miR-16–5p leads to improved detection of lowly expressed miRNAs and more precise measurement of differential expression overall. Furthermore, we establish the ability to target a second abundant miRNA and to multiplex the blocking of two miRNAs simultaneously. For small RNA sequencing, this technique could fill a similar role as do ribosomal or globin removal technologies in messenger RNA sequencing. 相似文献
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978.
Thomas W. Miller David R. Soto-Pantoja Anthony L. Schwartz John M. Sipes William G. DeGraff Lisa A. Ridnour David A. Wink David D. Roberts 《The Journal of biological chemistry》2015,290(41):24858-24874
Modulating tissue responses to stress is an important therapeutic objective. Oxidative and genotoxic stresses caused by ionizing radiation are detrimental to healthy tissues but beneficial for treatment of cancer. CD47 is a signaling receptor for thrombospondin-1 and an attractive therapeutic target because blocking CD47 signaling protects normal tissues while sensitizing tumors to ionizing radiation. Here we utilized a metabolomic approach to define molecular mechanisms underlying this radioprotective activity. CD47-deficient cells and cd47-null mice exhibited global advantages in preserving metabolite levels after irradiation. Metabolic pathways required for controlling oxidative stress and mediating DNA repair were enhanced. Some cellular energetics pathways differed basally in CD47-deficient cells, and the global declines in the glycolytic and tricarboxylic acid cycle metabolites characteristic of normal cell and tissue responses to irradiation were prevented in the absence of CD47. Thus, CD47 mediates signaling from the extracellular matrix that coordinately regulates basal metabolism and cytoprotective responses to radiation injury. 相似文献
979.
980.
Anders Nielsen Ingolf Steffan-Dewenter Catrin Westphal Olivia Messinger Simon G. Potts Stuart P. M. Roberts Josef Settele Hajnalka Szentgy?rgyi Bernard E. Vaissi��re Michalis Vaitis Michal Woyciechowski Ioannis Bazos Jacobus C. Biesmeijer Riccardo Bommarco William E. Kunin Thomas Tscheulin Ellen Lamborn Theodora Petanidou 《Ecological Research》2011,26(5):969-983
The decline of bees has raised concerns regarding their conservation and the maintenance of ecosystem services they provide to bee-pollinated wild flowers and crops. Although the Mediterranean region is a hotspot for bee species richness, their status remains poorly studied. There is an urgent need for cost-effective, reliable, and unbiased sampling methods that give good bee species richness estimates. This study aims: (a) to assess bee species richness in two common Mediterranean habitat types: semi-natural scrub (phrygana) and managed olive groves; (b) to compare species richness in those systems to that of other biogeographic regions, and (c) to assess whether six different sampling methods (pan traps, variable and standardized transect walks, observation plots and trap nests), previously tested in other European biogeographic regions, are suitable in Mediterranean communities. Eight study sites, four per habitat type, were selected on the island of Lesvos, Greece. The species richness observed was high compared to other habitat types worldwide for which comparable data exist. Pan traps collected the highest proportion of the total bee species richness across all methods at the scale of a study site. Variable and standardized transect walks detected the highest total richness over all eight study sites. Trap nests and observation plots detected only a limited fraction of the bee species richness. To assess the total bee species richness in bee diversity hotspots, such as the studied habitats, we suggest a combination of transect walks conducted by trained bee collectors and pan trap sampling. 相似文献