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531.
We report the nucleotide sequence of a gene encoding the constant region of a human immunoglobulin gamma 1 heavy chain (C gamma 1). A comparison of this sequence with those of the C gamma 2 and C gamma 4 genes reveals that these three human C gamma genes share considerable homology in both coding and noncoding regions. The nucleotide sequence differences indicate that these genes diverged from one another approximately 608 million years ago. An examination of hinge exons shows that these coding regions have evolved more rapidly than any other areas of the C gamma genes in terms of both base substitution and deletion/insertion events. Coding sequence diversity also is observed in areas of CH domains which border the hinge. 相似文献
532.
G. T. H. Ellison J. D. Skinner J. W. H. Ferguson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(1):62-68
The daily activity and energy metabolism of pouched mice (Saccostomus campestris) from two localities in southern Africa was examined following warm (25 °C) and cold (10 °C) acclimation under long (LD 14:10) and short (LD 10:14) photoperiol. There was no differential effect of photoperiod on the daily activity or metabolism of pouched mice from the two localities examined, which suggests that reported differences in photoresponsivity between these two populations were not the result of differences in daily organisation. Neverthe-less, there was a significant increase in metabolism at 10 °C, irrespective of photoperiod, even though seven cold-acclimated animals displayed bouts of spontaneous torpor and saved 16.4–36.2% of their daily energy expenditure. All but one of these bouts occurred under short photoperiod, which suggests that short photoperiod facilitated the expression of torpor and influenced the daily energy metabolism of these individuals. As expected for a noctureal species, the amount of time spent active increased following acclimation to short photoperiod at 25 °C. However, there was a reduction in mean activity levels under short photoperiod at 10 °C, possibly because the stimulation of activity by short photoperiod was masked by a reduction in activity during bouts of spontaneous torpor. Cold temperature clearly had an overriding effect on the daily activity and metabolism of this species by necessitating an increase in metabolic heat production and eliciting spontaneous torpor which overrode the effect of short photoperiod on activity at an ambient temperature of 10 °C.Abbreviations 3-ANOVA
three-way analysis of variance
- %ACT
percentage of time spent active
- ADMR
average daily metabolic rate
-
M
b
body mass
- MR
metabolic rate
- MRdark
metabolic rate recorded during the dark phase
- MRlight
metabolic rate recorded during the light phase
- NST
non-shivering thermogenesis
- RQ
respiratory quotient
- STPD
standard temperature and pressure, dry
-
T
a
ambient temperature
-
T
b
body temperature
-
VO2
oxygen consumption 相似文献
533.
We examined the phylogenetic relationships of 16 northern species of the
aplocheiloid genus Rivulus inhabiting the Caribbean, Central America, and
South America. A total of 714 base pairs per taxon were sequenced from two
segments of the mitochondrial genome, 12S rRNA and cytochrome b. Both
parsimony and neighbor-joining analyses suggest an ancient vicariant origin
of the Greater Antillean taxa, in addition to a quite recent dispersal of
species into the Lesser Antilles from the South American mainland. Combined
analyses support the monophyly of the northern South American assemblage as
the sister group of a Central American/Columbian biota. However, the
monophyly of the Central American biota remains uncertain. Divergence
estimates for the Central American taxa are calibrated from the Last
Cretaceous separation of the proto-Antilles from the Americas. These data
suggest that the extant Central American taxa represent the descendants of
at least two separate invasions during the Cenozoic, prior to the closing
of the Panamanian isthmus. Times are consistent with the extensive evidence
for reptilian and mammalian exchange throughout the Cenozoic.
相似文献
534.
A computational method is presented for characterizing residue usage, i.e.,
site-specific residue frequencies, in aligned protein sequences. The method
obtains frequency estimates that maximize the likelihood of the sequences
in a simple model for sequence evolution, given a tree or a set of
candidate trees computed by other methods. These maximum- likelihood
frequencies constitute a profile of the sequences, and thus the method
offers a rigorous alternative to sequence weighting for constructing such a
profile. The ability of this method to discard misleading phylogenetic
effects allows the biochemical propensities of different positions in a
sequence to be more clearly observed and interpreted.
相似文献
535.
Comparative studies of genes in the pseudoautosomal region (PAR) of human and mouse sex chromosomes have thus far been very
limited. The only comparisons that can presently be made indicate that the PARs of humans and mice are not identical in terms
of gene content. Here we describe additional comparative studies of human pseudoautosomal genes and their mouse homologs.
Using a somatic cell hybrid mapping panel, we have assigned the mouse homolog of the human pseudoautosomal interleukin 3 receptor
alpha subunit (IL3RA) gene to mouse Chromosome (Chr) 14. Attempts to clone the mouse homolog of the human pseudoautosomal
adenine nucleotide translocase-3 (ANT3) gene resulted in the isolation of the murine homologs of the human ANT1 and ANT2 genes.
The mouse Ant1 and Ant2 genes are very similar in sequence to their human homologs, and we have mapped them to mouse Chromosomes (Chrs) (8 and X
respectively) that exhibit conserved synteny with the chromosomes on which the human genes are located. In contrast, the homolog
of ANT3 appears to be either very divergent or absent from the mouse genome. Southern blot analysis of DNA from a variety
of mammalian species shows restricted conservation of human pseudoautosomal genes, a trend that also applies to the two cloned
mouse homologs of these genes and to neighboring human genes in distal Xp22.3. Our observations combined with those of other
workers lead us to propose a model for the evolution of the PAR that includes both rapid sequence evolution and the incremental
reduction in size of the region during mammalian evolution.
Received: 4 May 1995 / Accepted: 21 August 1995 相似文献
536.
Laboratory colonies of the pouched mouse (Saccostomus campestris) were housed in solid bottom cages and fed a varied diet containing excess fatty acids. Ringtail was only initiated in animals of all ages, from populations originating from different areas of South Africa, when the relative humidity fell below 30%. The incidence of ringtail was curtailed by maintaining relative humidity above 45% in animal houses. 相似文献
537.
Characterization of I-Ppo, an intron-encoded endonuclease that mediates homing of a group I intron in the ribosomal DNA of Physarum polycephalum. 总被引:16,自引:2,他引:14 下载免费PDF全文
A novel and only recently recognized class of enzymes is composed of the site-specific endonucleases encoded by some group I introns. We have characterized several aspects of I-Ppo, the endonuclease that mediates the mobility of intron 3 in the ribosomal DNA of Physarum polycephalum. This intron is unique among mobile group I introns in that it is located in nuclear DNA. We found that I-Ppo is encoded by an open reading frame in the 5' half of intron 3, upstream of the sequences required for self-splicing of group I introns. Either of two AUG initiation codons could start this reading frame, one near the beginning of the intron and the other in the upstream exon, leading to predicted polypeptides of 138 and 160 amino acid residues. The longer polypeptide was the major form translated in vitro in a reticulocyte extract. From nuclease assays of proteins synthesized in vitro with partially deleted DNAs, we conclude that both polypeptides possess endonuclease activity. We also have expressed I-Ppo in Escherichia coli, using a bacteriophage T7 RNA polymerase expression system. The longer polypeptide also was the predominant form made in this system. It showed enzymatic activity in bacteria in vivo, as demonstrated by the cleavage of a plasmid carrying the target site. Like several other intron-encoded endonucleases, I-Ppo makes a four-base staggered cut in its ribosomal DNA target sequence, very near the site where intron 3 becomes integrated in crosses of intron 3-containing and intron 3-lacking Physarum strains. 相似文献
538.
Detection of Listeria monocytogenes by using the polymerase chain reaction. 总被引:10,自引:5,他引:5 下载免费PDF全文
M T Bessesen Q A Luo H A Rotbart M J Blaser R T Ellison rd 《Applied microbiology》1990,56(9):2930-2932
A method was developed for detection of Listeria monocytogenes by polymerase chain reaction amplification followed by agarose gel electrophoresis or dot blot analysis with a 32P-labeled internal probe. The technique identified 95 of 95 L. monocytogenes strains, 0 of 12 Listeria strains of other species, and 0 of 12 non-Listeria strains. 相似文献
539.
G. T. H. Ellison J. D. Skinner A. Haim 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(8):740-746
Summary The effect of short photoperiod and cold on metabolism and thermoregulation was investigated in pouched mice (Saccostomus campestris: Cricetidae) from three localities in southern Africa which experience contrasting climatic conditions. Mice were initially acclimated to long photoperiod (14L: 10D) at 25°C, followed first by a decline in photoperiod (to 10L: 14D) and then by a fall in temperature (to 10°C). Minimum observed metabolic rate (basal metabolic rate) was unaffected by the decline in photoperiod but increased significantly following cold acclimation. Because minimal thermal conductance remained constant throughout the study the increase in minimum observed metabolic rate caused a decline in lower critical temperature to around 26°C. In contrast to minimum observed metabolic rate, regulatory non-shivering thermogenesis improved significantly following the decline in both photoperiod and temperature. However, pouched mice from the warmest locality were significantly less responsive to photoperiod than those from the other two localities whose survival might depend upon their ability to accurately predict seasonal changes in temperature. Neither photoperiod nor temperature had any effect on body mass, yet pouched mice from the most arid locality, where food supply might be unpredictable, were significantly smaller and had lower total energy requirements than those from areas experiencing higher annual rainfall. These results indicate that S. campestris displays considerable geographical variation in energy requirements together with differences in the use of photoperiod as an anticipatory cue for predicting the onset of winter. These differences appear to be related to the availability of energy and the relative severity of climatic conditions in each locality.Abbreviations ANOVA
analysis of variance
- BMR
basal metabolic rate
-
C
m
minimal thermal conductance
-
M
b
body mass
- MOMR
minimum observed metabolic rate
- MWU
Mann-Whitney U-test
- NA
noradrenaline
- NST
non-shivering thermogenesis
- RMR
resting metabolic rate
- RQ
respiratory quotient
-
T
a
ambient temperature
-
T
b
body temperature
-
T
1c
lower critical temperature
-
oxygen consumption
-
maximum
-
following NA injection 相似文献
540.
Examination of X chromosome markers in Rett syndrome: exclusion mapping with a novel variation on multilocus linkage analysis. 下载免费PDF全文
K A Ellison C P Fill J Terwilliger L J DeGennaro A Martin-Gallardo M Anvret A K Percy J Ott H Zoghbi 《American journal of human genetics》1992,50(2):278-287
Rett syndrome is a neurologic disorder characterized by early normal development followed by regression, acquired deceleration of head growth, autism, ataxia, and stereotypic hand movements. The exclusive occurrence of the syndrome in females and the occurrence of a few familial cases with inheritance through maternal lines suggest that this disorder is most likely secondary to a mutation on the X chromosome. To address this hypothesis and to identify candidate regions for the Rett syndrome gene locus, genotypic analysis was performed in two families with maternally related affected half-sisters by using 63 DNA markers from the X chromosome. Maternal and paternal X chromosomes from the affected sisters were separated in somatic cell hybrids and were examined for concordance/discordance of maternal alleles at the tested loci. Thirty-six markers were informative in at least one of the two families, and 25 markers were informative in both families. Twenty loci were excluded as candidates for the Rett syndrome gene, on the basis of discordance for maternal alleles in the half-sisters. Nineteen of the loci studied were chosen for multipoint linkage analysis because they have been previously genetically mapped using a large number of meioses from reference families. Using the exclusion criterion of a lod score less than -2, we were able to exclude the region between the Duchenne muscular dystrophy locus and the DXS456 locus. This region extends from Xp21.2 to Xq21-q23. The use of the multipoint linkage analysis approach outlined in this study should allow the exclusion of additional regions of the X chromosome as new markers are analyzed. This in turn will result in a defined region of the X chromosome that should be searched for candidate sequences for the Rett syndrome gene in both familial and sporadic cases. 相似文献