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991.
Bridging global and microregional scales: ploidy distribution in Pilosella echioides (Asteraceae) in central Europe 总被引:1,自引:0,他引:1
Trávnícek P Dockalová Z Rosenbaumová R Kubátová B Szelag Z Chrtek J 《Annals of botany》2011,107(3):443-454
Background and Aims
A detailed knowledge of cytotype distribution can provide important insights into the evolutionary history of polyploid systems. This study aims to explore the spatial distribution of different cytotypes in Pilosella echioides at various spatial scales (from the whole distributional range to the population level) and to outline possible evolutionary scenarios for the observed geographic pattern.Methods
DNA-ploidy levels were estimated using DAPI flow cytometry in 4410 individuals of P. echioides from 46 populations spread over the entire distribution range in central Europe. Special attention was paid to the cytotype structure in the most ploidy-diverse population in south-west Moravia.Key Results
Five different cytotypes (2x, 3x, 4x, 5x and 6x) were found, the last being recorded for the first time. Although ploidy-uniform (di- or tetraploid) sites clearly prevailed, nearly one-quarter of the populations investigated harboured more (up to all five) cytotypes. Whereas penta- and hexaploids constituted only a minority of the samples, a striking predominance of the triploid cytotype was observed in several populations.Conclusions
The representative sampling confirmed previous data on cytotype distribution, i.e. the spatial aggregation of mixed-ploidy populations in south-west Moravia and Lower Austria and the predominance of ploidy-uniform populations in other parts of the area investigated. Recurrent origin of polyploids from diploid progenitors via unreduced gametes and their successful establishment are considered the key factors promoting intrapopulational ploidy mixture (‘primary hybrid zones’). As an alternative to the generally accepted theory of cytotype co-existence based on the development of different means of inter-ploidy reproductive isolation, it is suggested that a long-term ploidy mixture can also be maintained in free-mating populations provided that the polyploids originate with a sufficient frequency. In addition, the prevalence (or subdominance) of the triploid cytotype in several mixed-ploidy populations represents the first evidence of such a phenomenon in plant systems with exclusively sexual reproduction. 相似文献992.
Trávnícek P Kubátová B Curn V Rauchová J Krajníková E Jersáková J Suda J 《Annals of botany》2011,107(1):77-87
Background and Aims
One of the prerequisites for polyploid research in natural systems is knowledge of the geographical distribution of cytotypes. Here inter- and intrapopulational ploidy diversity was examined in the Gymnadenia conopsea aggregate in central Europe and potential explanations and evolutionary consequences of the observed spatial patterns investigated.Methods
DAPI flow cytometry supplemented by confirmatory chromosome counts was used to determine ploidy in 3581 samples of the G. conopsea aggregate from 43 populations. The fine-scale spatial pattern of cytotype distribution (intra- and interploidy associations) was analysed with univariate and bivariate K-functions.Key Results
Gymnadenia tissues undergo a progressively partial endoreplication, which accounts for about 60 % and 75 % of the total genome in G. conopsea and G. densiflora, respectively. Flow cytometric profiles are therefore species-specific and can be used as a marker for rapid and reliable species recognition. Two majority (4x, 8x) and three minority (6x, 10x, 12x) cytotypes were found, often in mixed-ploidy populations (harbouring up to all five different ploidy levels). The scarcity of the minority cytotypes (about 2·7 %) suggests the existence of strong pre- or postzygotic mating barriers. Spatial structure was observed in plots of populations with the highest cytotype variation, including clumping of individuals of the same ploidy and negative association between tetra- and octoploids.Conclusions
The remarkable ploidy coexistence in the G. conopsea aggregate has reshaped our perception of intrapopulational ploidy diversity under natural conditions. This system offers unique opportunities for studying processes governing the formation and establishment of polyploids and assessing the evolutionary significance of the various pre- and postzygotic mating barriers that maintain this ploidy mixture. 相似文献993.
Aleksey Y. Malyshev Pavel M. Balaban 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(1):25-32
Bilaterally symmetrical pair of serotonergic cells, named C1 in Clione, has been described in the cerebral ganglia of all gastropod species. Here we describe a new role of C1 cells in gastropod
mollusks: control of activity of ciliated epithelium in the foregut. Detailed morphological investigation of C1 neurons in
the pteropod mollusk Clione
limacina revealed that these cells among other destinations send their neurites into foregut where they produce intense arborization
with large varicosities along the processes. Intracellular stimulation of a single C1 induced pronounced activation (often
followed by inhibition) of cilia lining the foregut. This activation was substantially reduced by serotonin antagonist mianserin.
Bath application of serotonin also induced transient increase in ciliary transport rate, followed by inhibition of ciliary
activity up to its full cessation in some areas of isolated foregut. These data suggest that C1 in Clione may use serotonin to influence cilia in the foregut. Taking into account high homology of serotonergic cerebral cells across
studied species we can speculate that these cells may be involved in the neural control of cilia in the foregut in other gastropod
mollusks. 相似文献
994.
Tong J Dolezal P Selkrig J Crawford S Simpson AG Noinaj N Buchanan SK Gabriel K Lithgow T 《Molecular biology and evolution》2011,28(5):1581-1591
The evolution of mitochondria from ancestral bacteria required that new protein transport machinery be established. Recent controversy over the evolution of these new molecular machines hinges on the degree to which ancestral bacterial transporters contributed during the establishment of the new protein import pathway. Reclinomonas americana is a unicellular eukaryote with the most gene-rich mitochondrial genome known, and the large collection of membrane proteins encoded on the mitochondrial genome of R. americana includes a bacterial-type SecY protein transporter. Analysis of expressed sequence tags shows R. americana also has components of a mitochondrial protein translocase or "translocase in the inner mitochondrial membrane complex." Along with several other membrane proteins encoded on the mitochondrial genome Cox11, an assembly factor for cytochrome c oxidase retains sequence features suggesting that it is assembled by the SecY complex in R. americana. Despite this, protein import studies show that the RaCox11 protein is suited for import into mitochondria and functional complementation if the gene is transferred into the nucleus of yeast. Reclinomonas americana provides direct evidence that bacterial protein transport pathways were retained, alongside the evolving mitochondrial protein import machinery, shedding new light on the process of mitochondrial evolution. 相似文献
995.
The best available approach of biological sample preparation for transmission electron microscopy currently includes cryoimmobilization
by high-pressure freezing (HPF) followed by freeze-substitution (FS). This method has been well established for interphase
cells; however, a reliable and easy procedure is still missing for mitotic cells especially because of their fragility and
sensitivity to treatments. Here, we present a fast and effective method for HPF/automated FS and LR White embedding of mitotic
cells which allows for their controlled and reproducible quality processing. It should be useful in various ultrastructural
studies on mitotic cells especially in combination with immunocytochemistry. 相似文献
996.
El-Hawiet A Kitova EN Kitov PI Eugenio L Ng KK Mulvey GL Dingle TC Szpacenko A Armstrong GD Klassen JS 《Glycobiology》2011,21(9):1217-1227
The binding of recombinant fragments of the C-terminal cell-binding domains of the two large exotoxins, toxin A (TcdA) and toxin B (TcdB), expressed by Clostridium difficile and a library consisting of the most abundant neutral and acidic human milk oligosaccharides (HMOs) was examined quantitatively at 25°C and pH 7 using the direct electrospray ionization mass spectrometry (ES-MS) assay. The results of the ES-MS measurements indicate that both toxin fragments investigated, TcdB-B1 and TcdA-A2, which possess one and two carbohydrate binding sites, respectively, bind specifically to HMOs ranging in size from tri- to heptasaccharides. Notably, five of the HMOs tested bind to both toxins: Fuc(α1-2)Gal(β1-4)Glc, Gal(β1-3)GlcNAc(β1-3)Gal(β1-4)Glc, Fuc(α1-2)Gal(β1-3)GlcNAc(β1-3)Gal(β1-4)Glc, Gal(β1-3)[Fuc(α1-4)]GlcNAc(β1-3)Gal(β1-4)Glc and Gal(β1-4)[Fuc(α1-3)]GlcNAc(β1-3)Gal(β1-4)Glc. However, the binding of the HMOs is uniformly weak, with apparent affinities ≤10(3?)M(-1). The results of molecular docking simulations, taken together with the experimental binding data, suggest that a disaccharide moiety (lactose or lactosamine) represents the core HMO recognition element for both toxin fragments. The results of a Verocytotoxicity neutralization assay reveal that HMOs do not significantly inhibit the cytotoxic effects of TcdA or TcdB. The absence of protection is attributed to the very weak intrinsic affinities that the toxins exhibit towards the HMOs. 相似文献
997.
Ji?í Reif Pavel Marhoul Old?ich ?í?ek Martin Konvi?ka 《Biodiversity and Conservation》2011,20(14):3645-3662
The European landscape is under pervasive attack of massive land use changes, such as agricultural intensification, urbanization
and land abandonment. These changes resulted in population decline of birds living in open habitats. Despite a good understanding
on the effects of these driving forces on bird populations, effective conservation actions are difficult to conduct as these
forces are closely connected with socioeconomic development of particular countries and thus almost impossible to reverse.
It is hence necessary to conserve refuge sites with a limited influence of these negative factors. We surveyed birds in 42
abandoned military training sites (AMTS) in a central European country, the Czech Republic, and we have found these sites
are valuable, and to date overlooked, refuges for bird conservation. Birds of high conservation concern and open habitats
birds (such as Miliaria calandra, Saxicola torquata or Lullula arborea) were more abundant in AMTS than predicted by their total population size in the Czech Republic. The most important characteristics
predicting attractiveness of AMTS for birds of conservation concern were low altitude, low proportion of forest/dense scrubland,
high proportion of sparse scrubland/bare ground and large area. Former military activity was beneficial for declining open
habitat birds by maintaining moderate disturbance levels, which are rarely found elsewhere in current landscapes. Owing to
reduction of armed forces across Europe AMTS provide continental-wide network of high-quality sites for bird conservation.
Nevertheless, AMTS are subject to pressure from building activities or loss of openness due to overgrowth of forest or scrub
plant communities. 相似文献
998.
Dong LF Jameson VJ Tilly D Prochazka L Rohlena J Valis K Truksa J Zobalova R Mahdavian E Kluckova K Stantic M Stursa J Freeman R Witting PK Norberg E Goodwin J Salvatore BA Novotna J Turanek J Ledvina M Hozak P Zhivotovsky B Coster MJ Ralph SJ Smith RA Neuzil J 《Free radical biology & medicine》2011,50(11):1546-1555
999.
Dorr CR Yemets S Kolomitsyna O Krasutsky P Mansky LM 《Bioorganic & medicinal chemistry letters》2011,21(1):542-545
Triterpene derivatives were analyzed for anti-HIV-1 activity and for cellular toxicity. Betulinic aldehyde, betulinic nitrile, and morolic acid derivatives were identified to have anti-HIV-1 activity. These derivatives inhibit a late step in virus replication, likely virus maturation. 相似文献
1000.
Franta Z Sojka D Frantova H Dvorak J Horn M Srba J Talacko P Mares M Schneider E Craik CS McKerrow JH Caffrey CR Kopacek P 《International journal for parasitology》2011,41(12):1253-1262
Intracellular proteolysis of ingested blood proteins is a crucial physiological process in ticks. In our model tick, Ixodes ricinus, cathepsin L (IrCL1) is part of a gut-associated multi-peptidase complex; its endopeptidase activity is important in the initial phase of haemoglobinolysis. We present the functional and biochemical characterisation of this enzyme. We show, by RNA interference (RNAi), that cathepsin L-like activity that peaks during the slow feeding period of females is associated with IrCL1. Recombinant IrCL1 was expressed in bacteria and yeast. Activity profiling with both peptidyl and physiological protein substrates (haemoglobin and albumin) revealed that IrCL1 is an acidic peptidase with a very low optimum pH (3-4) being unstable above pH 5. This suggests an endo/lysosomal localisation that was confirmed by indirect fluorescence microscopy that immunolocalised IrCL1 inside the vesicles of digestive gut cells. Cleavage specificity determined by a positional scanning synthetic combinatorial library and inhibition profile indicated that IrCL1 has the ligand-binding characteristics of the cathepsin L subfamily of cysteine peptidases. A non-redundant proteolytic function was demonstrated when IrCL1-silenced ticks had a decreased ability to feed compared with controls. The data suggest that IrCL1 may be a promising target against ticks and tick-borne pathogens. 相似文献