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61.
62.
Marmoset phylogenetics, conservation perspectives, and evolution of the mtDNA control region 总被引:3,自引:1,他引:2
Tagliaro CH; Schneider MP; Schneider H; Sampaio IC; Stanhope MJ 《Molecular biology and evolution》1997,14(6):674-684
Marmosets (genus Callithrix) are a diverse group of platyrrhine primates
with 13-15 purported taxa, many of them considered endangered.
Morphological analyses constitute most of the basis for recognition of
these forms as distinct taxa. The purpose of this study was to provide a
molecular view, based on mitochondrial control region sequences, of the
evolutionary history of the marmosets, concomitant with a molecular
phylogenetic perspective on species diversity within the group. An
additional purpose was to provide the first comparative examination of a
complete New World monkey control region sequence with those of other
mammals. The phylogenetic analyses provide convincing support for a split
between the Atlantic forest and Amazonian marmosets, with the inclusion of
the pygmy marmoset (Cebuella pygmaea) at the base of the Amazonian clade.
The earliest branch of the Atlantic forest group was C. aurita. In the
Amazonian group, the analyses do not support the recognition of C.
humeralifer and the recently described C mauesi as distinct taxa. They do,
however, support a clear distinction between C. argentata and a strongly
supported mixed clade of C. humeralifer and C. mauesi. In the Atlantic
forest group, the phylogenetic tree suggests mixing between C. penicillata,
C. kuhli, and possibly C. jacchus. Most of the sequence features
characteristic of other mammal control regions were also evident in
marmosets, with the exception that conserved sequence blocks (CSBs) 2 and 3
were not clearly identifiable. Tandem repeat units often associated with
heteroplasmy in a variety of other mammals were not evident in the marmoset
sequences.
相似文献
63.
Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae) 总被引:5,自引:0,他引:5
Campbell CS; Wojciechowski MF; Baldwin BG; Alice LA; Donoghue MJ 《Molecular biology and evolution》1997,14(1):81-90
Individual plants of several Amelanchier taxa contain many polymorphic
nucleotide sites in the internal transcribed spacers (ITS) of nuclear
ribosomal DNA (nrDNA). This polymorphism is unusual because it is not
recent in origin and thus has resisted homogenization by concerted
evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the
result of gene flow between two major North American clades resolved by
phylogenetic analysis of ITS sequences. Western North American species plus
A. humilis and A. sanguinea of eastern North America form one clade (A),
and the remaining eastern North American Amelanchier make up clade B. Five
eastern North American taxa are polymorphic at many of the nucleotide sites
where clades A and B have diverged and are thought to be of hybrid origin,
with A. humilis or A. sanguinea as one parent and various members of clade
B as the other parent. Morphological evidence suggests that A. humilis is
one of the parents of one of the polymorphic taxa, a microspecies that we
refer to informally as A. "erecta." Sequences of 21 cloned copies of the
ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical
to A. humilis sequence or to the clade B consensus sequence, or they are
apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier
"erecta" and another polymorphic taxon are suspected to be relatively old
because both grow several hundred kilometers beyond the range of one of
their parents. ITS sequence polymorphisms have apparently persisted in
these two taxa perhaps because of polyploidy and/or agamospermy (asexual
seed production), which are prevalent in the genus.
相似文献
64.
Mapping genes controlling root morphology and root distribution in a doubled-haploid population of rice 总被引:31,自引:0,他引:31
R. Yadav B. Courtois N. Huang G. McLaren 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(5):619-632
A deep thick root system has been demonstrated to have a positive effect on yield of upland rice under water stress conditions.
Molecular-marker-aided selection could be helpful for the improvement of root morphological traits, which are otherwise difficult
to score. We studied a doubled-haploid population of 105 lines derived from an indica×japonica cross and mapped the genes controlling root morphology and distribution (root thickness, maximum root length, total root
weight, deep root weight, deep root weight per tiller, and deep root to shoot ratio). Most putative QTL activity was concentrated
in fairly compact regions on chromosomes 1, 2, 3, 6, 7, 8 and 9, but was widely spread on chromosome 5 and largely absent
on chromosomes 4, 10, 11 and 12. Between three and six QTLs were identified on different chromosomes for each trait. Individual
QTLs accounted for between 4 and 22% of the variation in the traits. Multiple QTL models accounted for between 14 and 49%.
The main QTLs were common between traits, showing that it should be possible to modify several aspects of root morphology
simultaneously. There was evidence of interaction between marker locations in determining QTL expression. Interacting locations
were mostly on different chromosomes and showed antagonistic effects with magnitudes large enough to mask QTL detection. The
comparison of QTL locations with another population showed that one to three common QTLs per trait were recovered, among which
the most significant was in one or other population. These results will allow the derivation of isogenic lines introgressed
with these common segments, separately in the indica and japonica backgrounds.
Received: 12 August 1996 / Accepted: 15 November 1996 相似文献
65.
G J Lancz J V Scaletti L C McLaren 《Biochemical and biophysical research communications》1972,49(2):543-549
The effect of ethidium bromide (EB) on the buoyant density of reovirus RNA during equilibrium sedimentation has been investigated. The addition of the dye ethidium bromide was found to reduce the buoyant density of reovirus RNA in a Cs2SO4 gradient by a value of 0.13 to 0.15 g/cc, and provided a separation limit of 0.10 g/cc relative to the ? of marker DNA. Ethidium bromide was found also to reduce the ? of reovirus RNA to allow this RNA to band on a CsCl gradient. The separation factor between DNA and RNA on a CsCl-EB gradient was found to be 0.23 g/cc, indicating this type of gradient to be highly effective for separating the two types of polynucleotides. 相似文献
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The purpose of this report is to emphasize the importance of strict dietary control of patients suffering from the malabsorption syndrome and to announce the availability of a gluten-free bread-substitute, called “Unimix”, from the Scientific Development Committee, Room 14, Medical Building, University of Toronto. Science a gluten-free diet is difficult to follow because of the widespread use of wheat flour and other cereals in the production of many common foods, a suggested gluten-free meal pattern is presented, which conforms with Canada''s Food Guide and permits a number of choices of menu within certain limits. 相似文献