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排序方式: 共有185条查询结果,搜索用时 15 毫秒
1.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献2.
3.
Interactive analysis of phylogeny and character evolution using the computer program MacClade 总被引:15,自引:0,他引:15
W P Maddison D R Maddison 《Folia primatologica; international journal of primatology》1989,53(1-4):190-202
Computer programs for phylogenetic analysis have been important tools in systematics and evolutionary biology, but most have been designed primarily for the reconstruction of phylogenetic trees and not the interpretation of patterns of character evolution. Described here is the computer program MacClade, designed for interactive analysis of character evolution and phylogeny. For a given tree and a matrix of character data, MacClade displays its reconstruction of character evolution by shading the branches of the tree to indicate ancestral states. Trees can be manipulated for instance by picking up and moving branches. Assumptions underlying the reconstruction of character evolution can be varied extensively. With these manipulations and MacClade's graphical feedback, one can explore the relationships among phylogenetic trees, character data, assumptions and interpretations of character evolution. MacClade has extensive facilities for editing data, displaying various summaries of character evolution in charts and diagrams, and printing. 相似文献
4.
Fractions and subcellular structures were prepared from rat brain homogenate and their purity was assessed using enzyme markers, gamma-aminobutyric acid binding, DNA content, and electron microscopy. Insulin binding was highest on the plasma membrane preparations and approximately 50% less so on brain homogenate crude mitochondrial (P2), myelinated axon, and synaptosome preparations. Very low levels of binding were found on mitochondria and nuclei. Differences in binding between fractions were due to numbers of binding sites, and not variable binding affinity. There was a close relationship between insulin binding and the activity of Na/K ATPase (E.C. 3.6.1.4) in all fractions (r = 0.98). Insulin binding to the P2 was compared with plasma membrane fractions in seven brain regions, and the results demonstrated the same close relationship between insulin binding and plasma membrane content in all regions except hypothalamus. Plasma membrane insulin binding was well represented by the binding on P2 membranes in all regions except hypothalamus and brainstem. It was concluded that insulin binding is distributed evenly over the surface of brain cells and is not increased on nerve endings. 相似文献
5.
6.
V C Tsang K R Tsang K Hancock M A Kelly B C Wilson S E Maddison 《Journal of immunology (Baltimore, Md. : 1950)》1983,130(3):1359-1365
A systematic and quantitative search was conducted to identify and isolate a serologically pertinent antigen with high specific activity and low cross-reactivity from adult worms of Schistosoma mansoni. Adult worms of S. mansoni quickly thawed from liquid N2 temperatures were disrupted by controlled homogenization in isotonic buffered sucrose. Differential centrifugation of the homogenate yielded three particulate and one soluble fractions: the 480 x G pellet (nuclear), the 7650 x G pellet (mitochondrial), the 360,000 x G pellet (microsomal), and the 360,000 x G supernatant (cytosol). Quantitative analysis indicated a major concentration of specific antigenic activities in the microsomal fraction. Further purifications of the urea-solubilized, n-butanol-treated microsomal particles by gel filtration and ionic-exchange chromatography resulted in a microsomal antigen (MAMA) possessing high specific activity and low cross-reactivity. The final purification post-ionic exchange chromatograph showed a 30-fold increase of specific antigen activity over that of the cytosol fraction. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunotransfer blot by the "Western blot" technique (EITB) indicated specific antigenic activities in association with several different m.w. bands (heterogeneous m.w. by extrapolation = 4.3 to 11.9 x 10(6), 2.0 x 10(5), and 2.0 x 10(4) daltons) of the MAMA fraction. When compared with other reported serologic antigens, MAMA showed substantially higher specific activity and lower cross-reactivity. 相似文献
7.
8.
alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine
proteinase inhibitor superfamily, has a primary role in controlling
neutrophil elastase activity within the mammalian circulation. Several
studies have indicated that the reactive center region of alpha 1-PI, the
amino acid sequence of which is critical to recognition of and binding to
target proteinases, is highly divergent within and among species. This
appears to be a consequence of accelerated rates of evolution that may have
been driven by positive Darwinian selection. In order to examine this and
other features of alpha 1-PI evolution in more detail, we have isolated and
sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus
saxicola and Mus minutoides and have compared these with a number of other
mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent
of nonsynonymous substitution is generally high throughout the alpha 1-PI
mRNA molecule, indicating greater overall rates of amino acid substitution.
Within and among mouse species, the 5'-half of the mRNA, but not the
3'-half, has been homogenized by concerted evolution. Finally, the reactive
center is under diversifying or positive Darwinian selection in murid
rodents (rats, mice) and guinea pigs yet is under purifying selection in
primates and artiodactyls. The significance of these findings to alpha 1-PI
function and the possible selective forces driving evolution of serpins in
general are discussed.
相似文献
9.
Mitochondrial DNA polymorphisms in subterranean mole-rats of the Spalax ehrenbergi superspecies in Israel, and its peripheral isolates 总被引:1,自引:0,他引:1
Nevo E; Honeycutt RL; Yonekawa H; Nelson K; Hanzawa N 《Molecular biology and evolution》1993,10(3):590-604
Patterns of mitochondrial DNA (mtDNA) variation were examined in 133
mole-rats constituting all four chromosomal species (2n = 52, 2n = 54, 2n =
58, and 2n = 60) of the Spalax ehrenbergi superspecies in Israel, as well
as the peripheral isolates of 2n = 60. In the main range of the complex, a
total of 28 mtDNA haplotypes were found in 64 mole-rats, with most
haplotypes being unique to either a single chromosomal species or
population. mtDNA divergence increased from low to high diploid number in a
north-to-south direction in Israel. Overall levels of mtDNA diversity were
unexpectedly the highest in the 2n = 60, the youngest species of the
complex. The mtDNA haplotypes can be separated into two major groups, 2n =
52-54 and 2n = 58-60, and a phylogenetic analysis for each group revealed
evidence of a few haplotypes not sorted by diploid number. The overall
patterns of mtDNA divergence seen within and among the four chromosomal
species are consistent with the parapatric mode of speciation as suggested
from previous studies of allozyme and DNA hybridization. In a separate data
set the patterns of mtDNA variation were examined across the main
geographic range and across peripheral semi-isolates and isolates of the 2n
= 60 chromosomal species. Fifteen haplotypes were found in 69 mole-rats.
High levels of mtDNA diversity characterized the main range, semi-isolated,
and even some desert isolated populations. The peripheral isolates contain
much mtDNA diversity, including novel haplotypes.
相似文献
10.
The serologic and cell-mediated immune responses of hamsters exposed to 2 strains of Entamoeba histolytica (HM-1 and HM-19) were evaluated by a series of in vitro tests. The pathogenicity of the 2 strains was evaluated in terms of their ability to produce liver abscesses and spleen enlargement. Antibody response was evaluated by the indirect hemagglutination test. The cellular immune response was assayed by increased DNA synthesis by lymphocytes and migration inhibition of macrophages. 相似文献