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71.
Schiano de Colella JM Barbarat B Sweet R Gastaut JA Olive D Costello RT 《European cytokine network》2008,19(2):81-88
Mature dendritic cells (DC) are efficient, antigen-presenting cells required for the stimulation of naive T lymphocytes. Many members of the tumour necrosis factor (TNF) receptor family are involved in DC maturation, such as Fas, CD40, OX40L, LIGHT (homologous to lymphotoxins, exhibits inducible expression, and competes with HSV glycoprotein D for herpes virus entry mediator (HVEM), a receptor expressed by T lymphocytes) or RANK (receptor activator of NFkappaB), with different, but often overlapping effects. We focused our attention on RANK DC stimulation, since RANK ligand (RL) is expressed on activated T lymphocytes with different kinetic and expression patterns from the other members of TNF family previously cited. After culture with RL-transfected cells, a significant percentage of immature DC generated from monocytes (Mo-DC) acquired a typical, mature DC morphology and phenotype characterised by up-regulation of CD83, DC-LAMP (lysosome-associated membrane glycoprotein), HLA class I, CD86 and CD54. The functional RL-mediated maturation was demonstrated by a decrease in DC macropinocytosis and acquisition of the capacity to stimulate allogenic T-cells. Among the various cytokines tested, we detected only a weak up-regulation of IL-12p40. Our results show that ligation of RANK on DC cell surfaces is not only a survival stimulus, but also induces a partial and specific mature DC phenotype, the physiological significance of which is under investigation. 相似文献
72.
Cd36, a class B scavenger receptor, functions as a monomer to bind acetylated and oxidized low-density lipoproteins 总被引:1,自引:0,他引:1
Martin CA Longman E Wooding C Hoosdally SJ Ali S Aitman TJ Gutmann DA Freemont PS Byrne B Linton KJ 《Protein science : a publication of the Protein Society》2007,16(11):2531-2541
Cd36 is a small-molecular-weight integral membrane protein expressed in a diverse, but select, range of cell types. It has an equally diverse range of ligands and physiological functions, which has implicated Cd36 in a number of diseases including insulin resistance, diabetes, and, most notably, atherosclerosis. The protein is reported to reside in detergent-resistant microdomains within the plasma membrane and to form homo- and hetero-intermolecular interactions. These data suggest that this class B scavenger receptor may gain functionality for ligand binding, and/or ligand internalization, by formation of protein complexes at the cell surface. Here, we have overexpressed Cd36 in insect cells, purified the recombinant protein to homogeneity, and analyzed its stability and solubility in a variety of nonionic and zwitterionic detergents. Octylglucoside conferred the greatest degree of stability, and by analytical ultracentrifugation we show that the protein is monomeric. A solid-phase ligand-binding assay demonstrated that the purified monomeric protein retains high affinity for acetylated and oxidized low-density lipoproteins. Therefore, no accessory proteins are required for interaction with ligand, and binding is a property of the monomeric fold of the protein. Thus, the highly purified and functional Cd36 should be suitable for crystallization in octylglucoside, and the in vitro ligand-binding assay represents a promising screen for identification of bioactive molecules targeting atherogenesis at the level of ligand binding. 相似文献
73.
Biomass and photosynthesis of size-fractionated phytoplankton in Canadian Shield lakes 总被引:3,自引:2,他引:3
Both in situ primary production and biomass (chlorophyll ) of fractionated phytoplankton (<64,µ, <25 µm and < 10 µm) were studied in 10 Canadian Shield lakes to elucidate the spatial and temporal variability of the contribution of size fractions to the biomass and primary production of the phytoplankton community. Mean summer biomass and production of each size fraction varied significantly between lakes. Within lakes, temporal variation was low for biomass but great for production. However, temporal variation can be considered of minor importance during the sampling period, as compared to the spatial variation between lakes. Algae from the < 10 µm size fraction were the most important in biomass (41–65 %) and production (23–69%). The temporal trends for both phytoplankton variables thus generally followed closely that of the < 10 µm size fraction. Among the physical, chemical and morphometric variables of the studied lakes, water transparency (Secchi disk), total phosphorus, lake volume, lake area, and mean depth gave the best correlations with phytoplankton variables.Contribution number 354 from the Groupe de recherches en Ecologie des Eaux douces, Limnological Research Group, Université de Montréal. 相似文献
74.
Oberhaus Laura; Gelinas Malorie; Pinel-Alloul Bernadette; Ghadouani Anas; Humbert Jean-Francois 《Journal of plankton research》2007,29(10):827-838
The role of zooplankton in the control of cyanobacterial bloomsand the transfer of cyanotoxins to higher trophic levels areof great importance to the management of water resources. Manystudies have focused on the cyanobacterium Microcystis, butfew have examined the interactions between zooplankton and filamentouscyanobacteria. In this study, we provide experimental evidencefor the potential grazing of two toxic strains of filamentouscyanobacteria, Planktothrix rubescens and P. agardhii, by Daphniapulicaria, and for transfer of toxins in the planktonic foodchain. We determined clearance rates (CRs) by adult and juvenileD. pulicaria of the two Planktothrix strains, Scenedesmus acutusand a mixture of S. acutus cells with P. rubescens culture filtrate.Filament lengths were analyzed, and microcystin (MCY) presencein Daphnia was assessed using the Protein Phosphatase-2A (PP-2A)Inhibition Assay. The two Planktothrix strains were equallygrazed by D. pulicaria, but at lower CRs than S. acutus. Potentialanti-grazer toxins in P. rubescens filtrate did not inhibitDaphnia grazing. Small P. rubescens (<100 µm) filamentswere preferentially grazed by adult D. pulicaria, suggestingtheir limited ability to control a Planktothrix population duringa bloom. Large quantities of MCYs were found in unstarved Daphniapreviously exposed to Planktothrix, whereas quantities weresignificantly smaller in individuals starved for 24 h beforepreservation. This indicated a potential for transfer of toxinsin the food chain by Daphnia, especially immediately after ingestionof toxic cyanobacteria. 相似文献
75.
Gelinas Malorie; Pinel-Alloul Bernadette; Slusarczyk Miroslaw 《Journal of plankton research》2007,29(9):775-789
Our study showed for the first time in nature that two coexistingDaphnia adopted alternative life history and behavioural strategiesto cope with negative size-selection predation by gape-limitedyoung-of-the-year (YOY) perch. We evaluated the phenotypic plasticityin life history and behavioural traits of two coexisting Daphniaspecies, D. pulicaria (2 mm) and D. galeata mendotae (1.4 mm),in response to seasonal changes in predation by YOY yellow perch(Perca flavescens) in a mesotrophic lake. We expected that thelarge-sized D. pulicaria, the most likely subjected to size-selectivepredation by YOY perch, will show stronger antipredator responsesthan the small-sized D. galeata mendotae. To test this hypothesis,we examined changes in life history and behavioural traits injuveniles and adults of both species during four YOY fish predationperiods that were selected based on the presence of YOY perchin the pelagic zone and the relative abundance of Daphnia preyin their gut contents. Our study supports the scenario of negativesize-selective predation by gape-limited YOY perch on both Daphniaspecies. The electivity index indicated that no daphnids witha body length > 1.75 mm were predated by YOY yellow perch.Coexisting Daphnia exhibited phenotypic plasticity in theirantipredator defenses based on their vulnerability to seasonalchanges in size-selective predation of YOY perch. Juvenile Daphniawere the targeted prey and they responded by a decreased bodylength. Behavioural defenses were the dominant strategy usedby both adult Daphnia populations to withstand high predation.A decreased size at maturity was not employed by Daphnia, exceptat the very end of the predation period. Behavioural defensesare short-term strategy adopted to avoid predation. Both antipredatordefenses became unnecessary expenses and were no longer sustainedafter the predation period. 相似文献
76.
Regulation of one-carbon metabolism in Arabidopsis: the N-terminal regulatory domain of cystathionine gamma-synthase is cleaved in response to folate starvation 总被引:1,自引:0,他引:1 下载免费PDF全文
Loizeau K Gambonnet B Zhang GF Curien G Jabrin S Van Der Straeten D Lambert WE Rébeillé F Ravanel S 《Plant physiology》2007,145(2):491-503
In all organisms, control of folate homeostasis is of vital importance to sustain the demand for one-carbon (C1) units that are essential in major metabolic pathways. In this study we induced folate deficiency in Arabidopsis (Arabidopsis thaliana) cells by using two antifolate inhibitors. This treatment triggered a rapid and important decrease in the pool of folates with significant modification in the distribution of C1-substituted folate coenzymes, suggesting an adaptive response to favor a preferential shuttling of the flux of C1 units to the synthesis of nucleotides over the synthesis of methionine (Met). Metabolic profiling of folate-deficient cells indicated important perturbation of the activated methyl cycle because of the impairment of Met synthases that are deprived of their substrate 5-methyl-tetrahydrofolate. Intriguingly, S-adenosyl-Met and Met pools declined during the initial period of folate starvation but were further restored to typical levels. Reestablishment of Met and S-adenosyl-Met homeostasis was concomitant with a previously unknown posttranslational modification that consists in the removal of 92 amino acids at the N terminus of cystathionine gamma-synthase (CGS), the first specific enzyme for Met synthesis. Rescue experiments and analysis of different stresses indicated that CGS processing is specifically associated with perturbation of the folates pool. Also, CGS processing involves chloroplastic serine-type proteases that are expressed in various plant species subjected to folate starvation. We suggest that a metabolic effector, to date unidentified, can modulate CGS activity in vivo through an interaction with the N-terminal domain of the enzyme and that removal of this domain can suppress this regulation. 相似文献
77.
Julier B Huguet T Chardon F Ayadi R Pierre JB Prosperi JM Barre P Huyghe C 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2007,114(8):1391-1406
In many legume crops, especially in forage legumes, aerial morphogenesis defined as growth and development of plant organs,
is an essential trait as it determines plant and seed biomass as well as forage quality (protein concentration, dry matter
digestibility). Medicago truncatula is a model species for legume crops. A set of 29 accessions of M. truncatula was evaluated for aerial morphogenetic traits. A recombinant inbred lines (RILs) mapping population was used for analysing
quantitative variation in aerial morphogenetic traits and QTL detection. Genes described to be involved in aerial morphogenetic
traits in other species were mapped to analyse co-location between QTLs and genes. A large variation was found for flowering
date, morphology and dynamics of branch elongation among the 29 accessions and within the RILs population. Flowering date
was negatively correlated to main stem and branch length. QTLs were detected for all traits, and each QTL explained from 5.2
to 59.2% of the phenotypic variation. A QTL explaining a large part of genetic variation for flowering date and branch growth
was found on chromosome 7. The other chromosomes were also involved in the variation detected in several traits. Mapping of
candidate genes indicates a co-location between a homologue of Constans gene or a flowering locus T (FT) gene and the QTL
of flowering date on chromosome 7. Other candidate genes for several QTLs are described.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
78.
Daly-Burns B Alam TN Mackay A Clark J Shepherd CJ Rizzo S Tatoud R O'Hare MJ Masters JR Hudson DL 《Differentiation; research in biological diversity》2007,75(1):35-48
In the normal human prostate, undifferentiated proliferative cells reside in the basal layer and give rise to luminal secretory cells. There are, however, few epithelial cell lines that have a basal cell phenotype and are able to differentiate. We set out to develop a cell line with these characteristics that would be suitable for the study of the early stages of prostate epithelial cell differentiation. We produced a matched pair of conditionally immortalized prostate epithelial and stromal cell lines derived from the same patient. The growth of these cells is temperature dependent and differentiation can be induced following a rise in culture temperature. Three-dimensional co-cultures of these cell lines elicited gland-like structures reminiscent of prostatic acini. cDNA microarray analysis of the epithelial line demonstrated changes in gene expression consistent with epithelial differentiation. These genes may prove useful as markers for different prostate cell types. The cell lines provide a model system with which to study the process of prostatic epithelial differentiation and stromal-epithelial interactions. This may prove to be useful in the development of differentiation-targeted prostate cancer therapies. 相似文献
79.
80.
The extraembryonic endoderm of the elongating ovine conceptus was analyzed by scanning and transmission electron microscopy and by whole mount actin staining and immunofluorescence. Morphological and functional differences between the visceral endoderm (VE), the founding cell layer, and the parietal endoderm (PE) are presented. During the elongation process, the PE differentiated to fusiform multinucleated cells aligned parallel to the elongation axis of the conceptus, whereas the VE cells retained the aspect of typical epithelial cells. The multinucleated PE cells however, expressed cellular and nuclear markers typical of endodermal and polarized epithelial cells. The proteins of the extracellular matrix, laminin, and fibronectin, were specifically expressed in the PE. The presence of pairs of nuclei linked by mid-bodies positively stained with tubulin antibodies, indicated that the syncytial differentiation of the PE was due to karyokinesis which was not followed by cytokinesis rather than by cell fusion. 相似文献