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Bradley RD; Adkins RM; Honeycutt RL; McDonald JH 《Molecular biology and evolution》1998,15(6):709-717
Using the strictly neutral model as a null hypothesis, we tested for
deviations from expected levels of nucleotide polymorphism at the alcohol
dehydrogenase locus (Adh-1) within and among four species of pocket gophers
(Geomys bursarius major, G. knoxjonesi, G. texensis llanensis, and G.
attwateri). The complete protein-encoding region was examined, and 10
unique alleles, representing both electromorphic and cryptic alleles, were
used to test hypotheses (e.g., the neutral model) concerning the
maintenance of genetic variation. Nineteen variable sites were identified
among the 10 alleles examined, including 9 segregating sites occurring in
synonymous positions and 10 that were nonsynonymous. Several statistical
methods, including those that test for within-species variation as well as
those that examine variation within and among species, failed to reject the
null hypothesis that variation (both within and between species of Geomys)
at the Adh locus is consistent with the neutral theory. However, there was
significant heterogeneity in the ratio of polymorphism to divergence across
the gene, with polymorphisms clustered in the first half of the coding
region and fixed differences clustered in the second half of the gene. Two
alternative hypotheses are discussed as possible explanations for this
heterogeneity: an old balanced polymorphism in the first half of the gene
or a recent selective sweep in the second half of the gene.
相似文献
87.
Vargas ML Cruickshank RH Ross JG Holyoake AJ Ogilvie SC Paterson AM 《Molecular ecology resources》2009,9(2):505-515
The brushtail possum is a major agricultural and ecological pest in New Zealand. A novel noninvasive DNA sampling tool for detecting its presence (WaxTags, or WT) was tested. DNA was recovered from saliva left on WT, and two lengths (407 bp and 648 bp) of the cytochrome c oxidase I (COI) barcoding region were amplified by polymerase chain reaction (PCR). PCR products were considered (+) when a DNA band was clearly visible by electrophoresis. Different factors that might affect PCR (+) were investigated with captive possums: (i) both extraction protocols of the QIAGEN DNeasy Blood and Tissue Kit, (ii) effect of an overnight or longer delay of up to 3 weeks before DNA extraction on both COI amplicons, and (iii) effect of the individual, order and magnitude of the bite. Extraction protocols were not significantly different. The effect of the overnight delay was not significant, and amplification of the short amplicon was significantly higher (100%) than for the long fragment (48%). After a two or 3‐week delay, the short amplicon had 94% and 56% PCR (+), success rates, respectively. Individual, order and magnitude of a bite had no significant effect. The delay trial was repeated with WT from the wild, for which PCR (+) rate of the short amplicon was 63%, regardless of freshness. Four microsatellites were amplified from captive WT samples. We conclude that DNA from saliva traces can be recovered from WT, a potential new tool for noninvasive monitoring of possums and other wildlife. 相似文献
88.
Does sediment resuspension have persistent effects on phytoplankton? Experimental studies in three shallow lakes 总被引:10,自引:0,他引:10
1. The persistence of effects of sediment resuspension on chlorophyll a , phytoplankton production and plant nutrients was examined by artificially resuspending sediment in enclosures in three shallow lakes and monitoring concentrations for 4–8 days. Realism was assessed by relating initial suspended solids concentrations to those observed during natural wind events.
2. Positive effects on the phytoplankton, persisting for at least 4–6 days were detected in eight of the nine experiments, and similar effects on nutrient concentrations were also common, although suspended solids had normally returned to control levels within 24 h
3. The phytoplankton during the periods of persistence was normally dominated by planktonic rather than benthic/meroplanktonic genera.
4. Several of the positive responses appeared to be associated with relief of nitrogen deficiency in the algae.
5. Persistent effects from previous resuspension events may cause baseline concentrations of phytoplankton and nutrients in shallow lakes to be overestimated and the effects of resuspension on phytoplankton and nutrients to be underestimated 相似文献
2. Positive effects on the phytoplankton, persisting for at least 4–6 days were detected in eight of the nine experiments, and similar effects on nutrient concentrations were also common, although suspended solids had normally returned to control levels within 24 h
3. The phytoplankton during the periods of persistence was normally dominated by planktonic rather than benthic/meroplanktonic genera.
4. Several of the positive responses appeared to be associated with relief of nitrogen deficiency in the algae.
5. Persistent effects from previous resuspension events may cause baseline concentrations of phytoplankton and nutrients in shallow lakes to be overestimated and the effects of resuspension on phytoplankton and nutrients to be underestimated 相似文献
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S. A. Forbes A. A. J. Pannett J. H. D. Bassett B. Harding C. Wooding R. V. Thakker R. Butler D. Ogilvie R. Anand P. Gaudray G. Weber C. Larsson C. X. Zhang A. Calender J. W. M. Höppener C. J. M. Lips K. Kas 《Human genetics》1997,100(3-4):481-485
The multiple endocrine neoplasia type 1 (MEN1) locus has been previously localised to 11q13 by combined tumour deletion mapping
and recombination studies, and a 0.5-Mb region, flanked by PYGM and D11S449, has been defined. In the course of constructing
a contig, we have identified the location of the gene encoding the B56β subunit of protein phosphatase 2A (PP2A), which is
involved in cell signal transduction pathways and thus represents a candidate gene for MEN1. We have searched for mutations
in the PP2A-B56β coding region, together with the 5′ and 3′ untranslated regions in six MEN1 patients. DNA sequence abnormalities
were not identified and thus the PP2A-B56β gene is excluded as the candidate gene for MEN1. However, our precise localisation
of PP2A-B56β to this region of 11q13 may help in elucidating the basis for other disease genes mapping to this gene-rich region.
Received: 17 April 1997 / Accepted: 22 April 1997 相似文献