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E Tannich H Scholze R Nickel R D Horstmann 《The Journal of biological chemistry》1991,266(8):4798-4803
A cDNA clone derived from the gene encoding a cysteine proteinase of pathogenic Entamoeba histolytica was isolated using an antiserum to the purified enzyme. This clone was used to identify the homologous clone in a cDNA library from nonpathogenic E. histolytica. Sequence analysis and comparison of the predicted amino acid sequences revealed a sequence divergence of 16%. Southern blot analyses indicated that (i) pathogenic isolates may contain more genes coding for these or related enzymes than nonpathogenic isolates, (ii) the structure and organization of these genes are conserved within each group of amoebae, and (iii) none of the genes is found in both pathogenic and nonpathogenic E. histolytica, underlining the notion that the two groups are genetically distinct. Northern blot analyses suggested that the cysteine proteinase is expressed by pathogenic isolates in substantially higher amounts than by nonpathogenic isolates. Overexpression of this enzyme may be an important factor in the pathogenicity of E. histolytica. 相似文献
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J. C. Oosterwijk Gabriela Richard Michiel J. R. van der Wielen E. van de Vosse Wolfgang Harth Lodewijk A. Sandkuijl Egbert Bakker Gert-Jan B. van Ommen 《Human genetics》1997,100(5-6):520-524
X-linked keratosis follicularis spinulosa decalvans (KFSD) is a rare disorder affecting both skin and eyes. In the two extended
KFSD families analysed to date, the gene was mapped to Xp22.13–p22.2. By analyzing several new markers in this region, we
were able to narrow the candidate region to a 1-Mb interval between DXS7161 and (DXS7593, DXS7105) in the large Dutch pedigree.
In addition, we analyzed 23 markers in Xp21.2– p22.2 in a German family with KFSD. Haplotype and recombination analysis positioned
the KFSD gene in this family most likely outside the candidate region on Xp22.13–p22.2. This finding is suggestive for genetic
heterogeneity: in this pedigree there is either another locus on the X-chromosome, or KFSD is transmitted here as an autosomal
dominant trait with variable expression.
Received: 28 May 1996 / Accepted: 28 May 1997 相似文献
87.
Some shallow lakes switch repeatedly back and forth between a vegetation dominated clear-water state and a contrasting turbid
state. Usually such alternations occur quite irregularly, but in some cases the switches between states are remarkably regular.
Here we use data from a well-studied Dutch lake and a set of simple models to explore possible explanations for such cyclic
behavior. We first demonstrate from a graphical model that cycles may in theory occur if submerged macrophytes promote water
clarity in the short run, but simultaneously cause an increased nutrient retention, implying an accumulation of nutrients
in the long run. Thus, although submerged plants create a positive feedback on their own growth by clearing the water, they
may in the long run undermine their position by creating a slow “internal eutrophication”. We explore the potential role of
two different mechanisms that may play a role in this internal eutrophication process using simulation models: (1) reduction
of the P concentration in the water column by macrophytes, leading to less outflow of P, and hence to a higher phosphorus
accumulation in the lake sediments and (2) a build-up of organic matter over time resulting in an increased sediment oxygen
demand causing anaerobic conditions that boost P release from the sediment. Although the models showed that both mechanisms
can produce cyclic behavior, the period of the cycles caused by the build-up of organic material seemed more realistic compared
to data of the Dutch Lake Botshol in which regular cycles with a period of approximately 7 years have been observed over the
past 17 years. 相似文献
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Egbert Giles LeighJr. 《Trends in ecology & evolution》1999,14(12):495
The ‘modern evolutionary synthesis’ convinced most biologists that natural selection was the only directive influence on adaptive evolution. Today, however, dissatisfaction with the synthesis is widespread, and creationists and antidarwinians are multiplying. The central problem with the synthesis is its failure to show (or to provide distinct signs) that natural selection of random mutations could account for observed levels of adaptation. 相似文献
90.
Daniel Eibach Ralf Krumkamp Hassan M. Al-Emran Nimako Sarpong Ralf Matthias Hagen Yaw Adu-Sarkodie Egbert Tannich Jürgen May 《PLoS neglected tropical diseases》2015,9(3)
BackgroundThe relevance of Cryptosporidium infections for the burden of childhood diarrhoea in endemic settings has been shown in recent years. This study describes Cryptosporidium subtypes among symptomatic and asymptomatic children in rural Ghana to analyse subtype-specific demographic, geographical, seasonal and clinical differences in order to inform appropriate control measures in endemic areas.Conclusions/SignificanceCryptosporidiosis is characterized by seasonal anthroponotic transmission of strains typically found in Sub-Saharan Africa. The infection mainly affects young infants, with vomiting and diarrhoea being one of the leading symptoms in C. parvum infection. Combining molecular typing and clinical data provides valuable information for physicians and is able to track sources of infections. 相似文献