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排序方式: 共有174条查询结果,搜索用时 15 毫秒
141.
JÉRÔME ATEUDJIEU JOHN WILLIAMS MARIE HIRTLE CÉDRIC BAUME JOYCE IKINGURA ALASSANE NIARÉ DOMINIQUE SPRUMONT 《Developing world bioethics》2010,10(2):88-98
Background: As actors with the key responsibility for the protection of human research participants, Research Ethics Committees (RECs) need to be competent and well‐resourced in order to fulfil their roles. Despite recent programs designed to strengthen RECs in Africa, much more needs to be accomplished before these committees can function optimally. Objective: To assess training needs for biomedical research ethics evaluation among targeted countries. Methods: Members of RECs operating in three targeted African countries were surveyed between August and November 2007. Before implementing the survey, ethical approvals were obtained from RECs in Switzerland, Cameroon, Mali and Tanzania. Data were collected using a semi‐structured questionnaire in English and in French. Results: A total of 74 respondents participated in the study. The participation rate was 68%. Seventy one percent of respondents reported having received some training in research ethics evaluation. This training was given by national institutions (31%) and international institutions (69%). Researchers and REC members were ranked as the top target audiences to be trained. Of 32 topics, the top five training priorities were: basic ethical principles, coverage of applicable laws and regulations, how to conduct ethics review, evaluating informed consent processes and the role of the REC. Conclusion: Although the majority of REC members in the targeted African countries had received training in ethics, they expressed a need for additional training. The results of this survey have been used to design a training program in research ethics evaluation that meets this need. 相似文献
142.
GUILLAUME EVANNO†‡ EMMANUEL CASTELLA§ CÉLINE ANTOINE§ GABRIELLE PAILLAT§ JÉRÔME GOUDET 《Molecular ecology》2009,18(6):1137-1144
We examined the spatial and temporal variation of species diversity and genetic diversity in a metacommunity comprising 16 species of freshwater gastropods. We monitored species abundance at five localities of the Ain river floodplain in southeastern France, over a period of four years. Using 190 AFLP loci, we monitored the genetic diversity of Radix balthica , one of the most abundant gastropod species of the metacommunity, twice during that period. An exceptionally intense drought occurred during the last two years and differentially affected the study sites. This allowed us to test the effect of natural disturbances on changes in both genetic and species diversity. Overall, local (alpha) diversity declined as reflected by lower values of gene diversity H S and evenness. In parallel, the among-sites (beta) diversity increased at both the genetic ( F ST ) and species ( F STC ) levels. These results suggest that disturbances can lead to similar changes in genetic and community structure through the combined effects of selective and neutral processes. 相似文献
143.
Boris Musset Susan ME Smith Sindhu Rajan Vladimir V Cherny Deri Morgan Thomas E DeCoursey 《Channels (Austin, Tex.)》2010,4(4):260-265
The voltage-gated proton channel exists as a dimer, although each protomer has a separate conduction pathway, and when forced to exist as a monomer, most major functions are retained. However, the proton channel protomers appear to interact during gating. Proton channel dimerization is thought to result mainly from coiled-coil interaction of the intracellular C-termini. Several types of evidence are discussed that suggest that the dimer conformation may not be static, but is dynamic and can sample different orientations. Zn2+ appears to link the protomers in an orientation from which the channel(s) cannot open. A tandem WT-WT dimer exhibits signs of cooperative gating, indicating that despite the abnormal linkage, the correct orientation for opening can occur. We propose that C-terminal interaction functions mainly to tether the protomers together. Comparison of the properties of monomeric and dimeric proton channels speaks against the hypothesis that enhanced gating reflects monomer-dimer interconversion.Key words: voltage-gated proton channels, voltage gating, voltage-sensing domains, phagocytes, coiled-coil, oligomerization, proton currents, pH, dimerization, C-terminus 相似文献
144.
本文对移植的5-HT神经元从蛛网膜下腔跨软脊膜迁移进入脊髓作了初步研究。将含有5-HT细胞的胚胎中缝核组织小块或神经细胞悬浮液作为移植物,以5-HT免疫组织化学方法跟踪移植细胞,结果如下:(1)在低胸水平横切脊髓,10d后,横断脊髓内的5-HT纤维消失。(2)横切脊髓(方法同上)后,立即将中缝核组织小块移植在胸腰段脊髓的蛛网膜下腔,一月后.在横断脊髓内出现5-HT阳性神经元和纤维。5-HT纤维能在灰白质内延伸。(3)脊髓横断后,若以中缝核的细胞悬浮液代替组织小块,作上述移植,则在移植区附近的灰质内出现大量的5-HT阳性神经元。这些神经元在灰质内的分布范围与神经细胞悬浮液在蛛网膜下腔的移植范围相一致。迁入神经元能在灰质内重新形成5-HT阳性纤维网。(4)经上述移植后,灰质内出现的5-HT阳性纤维随远离细胞体而变得稀疏。白质内的5-HT阳性纤维远比灰质内稀少。本实验结果表明:移植在脊髓蛛网膜下腔的脑干5-HT细胞能跨软脊膜迁移进入脊髓。 相似文献
145.
Seston quantity and quality was measured in the Urdaibai Estuary in summer, when river discharge is low and tidal flushing
is the main driving force to transport and resuspend particulate matter in the estuary. The highest seston concentrations
are found in the upper estuary, where more than 90% of total suspended particulate matter is made up of particles <20 μm.
There is a temporal ebb-flood asymmetry and turbulent mixing is stronger at flood tide. During dry calm periods sediment resuspension
is observed for a short period of time at floods during spring tides, decreasing drastically before slack waters. In spite
of this, particulate organic matter mainly originates from anthropogenic sources (domestic wastewater discharge) and plankton
production. 相似文献
146.
147.
Molecular phylogenetic evidence that the phylum Haplosporidia has an alveolate ancestry 总被引:1,自引:0,他引:1
The phylogenetic position of the phylum Haplosporidia among other protists
was investigated with the complete 16S-like rRNA gene sequences from two
species in the phylum: Haplosporidium nelsoni, a parasite of oysters, and
Minchinia teredinis, a parasite of shipworms. Because the lack of obvious
morphological homologies with other protists hampered decisions regarding
taxonomic composition for sequence alignment and phylogenetic analysis, the
complete sequences for these two haplosporidians were directed as search
queries to the blast/ncbi.nlm.nih.gov electronic mail server. The results
of this heuristic similarity search provided a basis for constructing a
preliminary higher-taxonomic-level analysis comparing the haplosporidians
with species from the slime molds, fungi, algae, amoebae, ciliates,
dinoflagellates, and apicomplexans. Maximum parsimony yielded equivocal
results, whereas transversionally weighted parsimony suggested an affinity
with the alveolates (i.e., the ciliates, dinoflagellates, and
apicomplexans). Multiple alignment of the two haplosporidian sequences
against 17 taxa in a secondary analysis focusing on the alveolates and
subsequent parsimony analysis placed the phylum Haplosporidia as a
monophyletic group within the Alveolata and as a taxon of equal rank with
the other three alveolate phyla. The precise placement within the Alveolata
was sensitive to weighting.
相似文献
148.
A requirement for trypsin-sensitive cell-surface components for cell-cell interactions of embryonic neural retina cells 总被引:5,自引:3,他引:2 下载免费PDF全文
A quantitative assay was used to measure the rate of collection of a population of embryonic neural retina cells to the surface of cell aggregates. The rate of collection of freshly trysinized cells was limited in the initial stages by the rate of replacement of trypsin-sensitive cell- surface components. When cells were preincubated, or "recovered," and then added to cell aggregates, collection occurred at a linear rate and was independent of protein and glycoprotein synthesis. The adhesion of recovered cells was temperature and energy dependent, and was reversibly inhibited by cytochalasin B. Colchicine had little effect on collection of recovered cells. Antiserum directed against recovered cell membranes was shown to bind to recovered cells by indirect immunofluorescence. The antiserum also was shown to inhibit collection of recovered cells to aggregates, suggesting that at least some of the antigens identified might be involved in the adhesion process. The inhibitory effect of the antiserum was dose dependent . Freshly trypsinized cells absorbed neither the immunofluorescence activity nor the adhesion-inhibiting activity. Recovered cells absorbed away both activities. In specificity studies, dorsal neural retina cells adhered to aggregates of ventral optic tectum in preference to aggregates of dorsal optic tectum. The adhesive specificity of the dorsal retina cells was less sensitive to trypsin than the adhesive specificity of ventral retina cells which adhered preferentially to dorsal tectal aggregates only after a period of recovery. 相似文献
149.
JR
ME GOUDET 《Molecular ecology resources》2005,5(1):184-186
The package hierfstat for the statistical software r , created by the R Development Core Team, allows the estimate of hierarchical F‐statistics from a hierarchy with any numbers of levels. In addition, it allows testing the statistical significance of population differentiation for these different levels, using a generalized likelihood‐ratio test. The package hierfstat is available at http://www.unil.ch/popgen/softwares/hierfstat.htm . 相似文献
150.
ALAIN DEJEAN CHAMPLAIN DJIÉTO-LORDON JÉRÔME ORIVEL 《Biological journal of the Linnean Society. Linnean Society of London》2008,93(1):63-69
Plant ants generally provide their host myrmecophytes (i.e. plants that shelter a limited number of ant species in hollow structures) protection from defoliating insects, but the exact nature of this protection is poorly known. It was with this in mind that we studied the association between Tetraponera aethiops F. Smith (Pseudomyrmecinae) and its specific host myrmecophyte Barteria fistulosa Mast. (Passifloraceae). Workers bore entrances into the horizontal hollow branches (domatia) of their host B. fistulosa , near the base of the petiole of the alternate horizontal leaves. They then ambush intruders from the domatia, close to these entrances. After perceiving the vibrations caused when an insect lands on a leaf, they rush to it and sting and generally spreadeagle the insect (only small caterpillars are mastered by single workers). Among the insects likely to defoliate B. fistulosa , adult leaf beetles and large katydids were taken as prey and cut up; single workers then retrieved some pieces, whereas other workers imbibed the prey's haemolymph. Other insects known to defoliate this plant, if unable to escape, were killed and discarded. Small Acrea zetes L. caterpillars were stung and then discarded by single workers; whereas locusts of different sizes were mastered by groups of workers that stung and spreadeagled them before discarding them (although a part of their haemolymph was imbibed). More workers were involved and more time was necessary to master insects taken as prey than those attacked and discarded. Consequently, the protection T. aethiops workers provide to their host B. fistulosa from defoliating insects results from predation, but more often from a type of aggressiveness wherein insects are killed and then discarded. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 63–69. 相似文献