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31.
M Gálvez-Santisteban AE Rodriguez-Fraticelli DM Bryant S Vergarajauregui T Yasuda I Bañón-Rodríguez I Bernascone A Datta N Spivak K Young CL Slim PR Brakeman M Fukuda KE Mostov F Martín-Belmonte 《Nature cell biology》2012,14(8):838-849
The formation of epithelial tissues requires both the generation of apical-basal polarity and the coordination of this polarity between neighbouring cells to form a central lumen. During de novo lumen formation, vectorial membrane transport contributes to the formation of a singular apical membrane, resulting in the contribution of each cell to only a single lumen. Here, from a functional screen for genes required for three-dimensional epithelial architecture, we identify key roles for synaptotagmin-like proteins 2-a and 4-a (Slp2-a/4-a) in the generation of a single apical surface per cell. Slp2-a localizes to the luminal membrane in a PtdIns(4,5)P(2)-dependent manner, where it targets Rab27-loaded vesicles to initiate a single lumen. Vesicle tethering and fusion is controlled by Slp4-a, in conjunction with Rab27/Rab3/Rab8 and the SNARE syntaxin-3. Together, Slp2-a/4-a coordinate the spatiotemporal organization of vectorial apical transport to ensure that only a single apical surface, and thus the formation of a single lumen, occurs per cell. 相似文献
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Estimating plant responses to climate by direct gradient analysis and geographic distribution analysis 总被引:1,自引:0,他引:1
We characterised the climatic behaviour of 53 woody species in terms of the climatic factors that play the main role in controlling
species distribution in the study area. Floristic and climatic data were obtained from 150 stands in sites under climatic
control (i.e. eu-climatopes). The sampling strategy used allowed a reliable match between floristic and climatic observations.
Different methods of frequency analysis and goodness-of-fit tests were used to identify associations between species occurrence
and climatic characteristics. The species' responses were summarised by statistics describing ecological preferences and amplitudes,
and species were grouped accordingly. A Gaussian response model was fitted to the abundance data along the main climatic gradients
for selected species and response surfaces were derived by spatial analysis for a set of indicator species. Frequency analysis
methods detected 42 indicator taxa for the Baudiere's Qe drought index, and lower numbers, 34 and 22, respectively, for the mean minimum coldest-month temperature and the daily temperature
range in the coldest month. Goodness-of-fit tests revealed a lower number of ecological profiles with statistically significant
deviations from equidistribution. We discuss the relative performance of the different methods and suggest that the combined
use of statistical tests and frequency analyses may improve estimation of the environmental requirements of species. We also
recommend using the species' responses to key environmental factors as reliable criteria in the definition of plant functional
types.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Mengsheng Gao Anne Benge Julia M. Mesa Regina Javier Feng-Xia Liu 《Biological procedures online》2018,20(1):8
Background
Soil bacterium Sinorhizobium meliloti (S. meliloti) forms an endosymbiotic partnership with Medicago truncatula (M. truncatula) roots which results in root nodules. The bacteria live within root nodules where they function to fix atmospheric N2 and supply the host plant with reduced nitrogen. The bacterial RNA-binding protein Hfq (Hfq) is an important regulator for the effectiveness of the nitrogen fixation. RNA immunoprecipitation (RIP) method is a powerful method for detecting the association of Hfq protein with specific RNA in cultured bacteria, yet a RIP method for bacteria living in root nodules remains to be described.Results
A modified S. meliloti gene encoding a His-tagged Hfq protein (HfqHis) was placed under the regulation of the native Hfq gene promoter (Phfqsm). The trans produced HfqHis protein was accumulated at its nature levels during all stages of the symbiosis, allowing RNAs that associated with the given protein to be immunoprecipitated with the anti-His antibody against the protein from root nodule lysates. RNAs that associated with the protein were selectively enriched in the immunoprecipitated sample. The RNAs were recovered by a simple method using heat and subsequently analyzed by RT-PCR. The nature of PCR products was determined by DNA sequencing. Hfq association with specific RNAs can be analyzed at different conditions (e. g. young or older root nodules) and/or in wild-type versus mutant strains.Conclusions
This article describes the RIP method for determining Sinorhizobium meliloti RNA-Hfq associations in vivo. It is also applicable to other rhizobia living in planta, although some tissue-specific modification related to sample disruption and homogenization may be needed.39.
40.
At variance with previous reports, the paedomorphic goby Aphia minuta does not show semelparity, but abbreviate iteroparity like other small Mediterranean gobiid species. In spring, the mature ovary contains several batches of eggs at different stages of vitellogenesis. This indicates that the breeding season of A. minuta is quite long and that spawning takes place at least twice during its short lifespan, involving in each ovulatory wave different batches of oocytes which undergo vitellogenesis at different times. These observations agree with the testicular cycle data. In males, which in spring exhibit active spermiation coinciding with deposition of the first batch of oocytes, spermatogonial mitosis also resumes, eventually resulting in the production of new sperm in summer. 相似文献