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排序方式: 共有123条查询结果,搜索用时 15 毫秒
1.
Chytrid fungus Batrachochytrium dendrobatidis (Bd), an emerging disease, has been decimating amphibian populations around the world for several decades. We quantified
aspects of larval fitness, adaptive (major histocompatibility complex) diversity and neutral (microsatellite) diversity in
natterjack toad (Bufo calamita) populations in two regions of north-west England. Toads in region one had no evidence of chytrid infection, whereas in region
two there was a substantial prevalence of Bd. Larval fitness (growth rate, time to metamorphosis and survival) of B. calamita did not differ between the regions. Genetic diversity at microsatellite loci was much higher in the infected than in the
uninfected region, but the converse was true of MHC diversity indicating that genetic drift was unlikely to explain the differences
in MHC between the regions. Furthermore, MHC allele frequencies varied significantly between Bd-infected and uninfected populations.
Microsatellite diversity was not a robust indicator of larval fitness in these toad populations while MHC genotype frequencies
varied in a way that was consistent with directional selection in response to pathogen prevalence. The acquired immune defences
may therefore play an important role in determining the susceptibility of amphibian species to chytridiomycosis. 相似文献
2.
Marcelo H Ratto Louis TJ Delbaere Yvonne A Leduc Roger A Pierson Gregg P Adams 《Reproductive biology and endocrinology : RB&E》2011,9(1):24
Background
The objective of the present study was to isolate and purify the protein fraction(s) of llama seminal plasma responsible for the ovulation-inducing effect of the ejaculate. 相似文献3.
Christopher J. Durrant Trevor J. C. Beebee Frank Greenaway David A. Hill 《Conservation Genetics》2009,10(2):489-496
We investigated the population genetics of seven maternity roosts of Bechstein’s bats widely distributed across the south
of England. Across all of the populations sampled, two mitochondrial DNA microsatellite loci were fixed for single haplotypes.
Genetic diversity across eight nuclear microsatellite loci was similar in all seven populations, with a mean He of 0.727. However, six of the populations showed substantial homozygote excess, with F
IS estimates greater than zero, indicative of recent inbreeding. Bottleneck tests also implied that six of the populations have
experienced recent declines. Genetic differentiation among the populations was low, with a mean intersite F
ST estimate of 0.041. There was no significant isolation by distance using allele frequency-based criteria (F
ST and genetic distances), however, a weak correlation was found using the allele size-based R
ST criterion. Assignment tests were unable to distinguish the seven sampling sites as distinct clusters. Mean intra-roost relatedness
(r) was 0.079, indicative of recent inbreeding relative to German populations. All but one of the bats had one or more half
or full siblings in its maternity roost. In addition, family relationships of individuals within a colony were significantly
commoner than family relationships among four proximal roosts <8 km apart. The results are discussed in the context of conservation
requirements for this rare British bat. 相似文献
4.
5.
Sara Rosati Ewald TJ van den Bremer Janine Schuurman Paul WHI Parren Johannis P Kamerling Albert JR Heck 《MABS-AUSTIN》2013,5(6):917-924
Here, we describe a fast, easy-to-use, and sensitive method to profile in-depth structural micro-heterogeneity, including intricate N-glycosylation profiles, of monoclonal antibodies at the native intact protein level by means of mass spectrometry using a recently introduced modified Orbitrap Exactive Plus mass spectrometer. We demonstrate the versatility of our method to probe structural micro-heterogeneity by describing the analysis of three types of molecules: (1) a non-covalently bound IgG4 hinge deleted full-antibody in equilibrium with its half-antibody, (2) IgG4 mutants exhibiting highly complex glycosylation profiles, and (3) antibody-drug conjugates. Using the modified instrument, we obtain baseline separation and accurate mass determination of all different proteoforms that may be induced, for example, by glycosylation, drug loading and partial peptide backbone-truncation. We show that our method can handle highly complex glycosylation profiles, identifying more than 20 different glycoforms per monoclonal antibody preparation and more than 30 proteoforms on a single highly purified antibody. In analyzing antibody-drug conjugates, our method also easily identifies and quantifies more than 15 structurally different proteoforms that may result from the collective differences in drug loading and glycosylation. The method presented here will aid in the comprehensive analytical and functional characterization of protein micro-heterogeneity, which is crucial for successful development and manufacturing of therapeutic antibodies 相似文献
6.
Trevor J. C. Beebee John Buckley Ivor Evans Jim P. Foster Antony H. Gent Chris P. Gleed-Owen Geoffrey Kelly Graham Rowe Charles Snell Julia T. Wycherley Inga Zeisset 《Biodiversity and Conservation》2005,14(7):1607-1626
Introduced species often pose serious threats to biodiversity, but occasionally confusion arises as to whether a species really is introduced or is in fact an overlooked native. A recent UK conservation dilemma has centred on the status of the pool frog Rana lessonae. This species has been the subject of documented introductions from central and southern Europe since the early 1800s, the accepted position being that all UK R. lessonae populations are descended from these introductions. However, a closer examination of early UK literature sources, and recent discoveries of isolated, native R. lessonae populations in Sweden and Norway, led some herpetologists to question whether the species was in fact present as a native at some locations prior to the introductions. Research was initiated along four major lines of enquiry: genetic, bioacoustic, archaeozoological and archival. A high degree of convergence among the genetic and bioacoustic investigations demonstrated that the potentially native UK pool frogs were closely related to Scandinavian frogs, thus ruling out introductions from further south as a potential origin. Subfossil evidence of pool frogs was found from ca. 1000 years before present, demonstrating that the species occurred in the UK prior to known introductions. Archival sources produced no historical support for introductions from northern Europe. The postglacial history inferred for these northern populations is consistent with the known climatic and geographical conditions. Taken together, the evidence for the native status of the pool frog is compelling, and furthermore the UK population appears to be part of a distinct northern clade. 相似文献
7.
Edward G. Brede Graham Rowe Jan Trojanowski Trevor J. C. Beebee 《Molecular ecology resources》2001,1(4):308-310
The Common Toad Bufo bufo is a wide‐ranging species, with a distribution encompassing much of Europe and Asia. Few molecular studies have been undertaken on this species, and only one polymorphic microsatellite locus has been identified. Therefore, little is known about the genetic variability within and between B. bufo populations. The value of such information is essential for monitoring the species and its environment. This paper reports the characterization of 15 B. bufo microsatellite loci using individuals from a Spanish and UK sample. 相似文献
8.
TJ Beveridge 《Biotechnic & histochemistry》2001,76(3):111-118
The Gram stain differentiates bacteria into two fundamental varieties of cells. Bacteria that retain the initial crystal violet stain (purple) are said to be 'Gram-positive,' whereas those that are decolorized and stain red with carbol fuchsin (or safranin) are said to be 'Gram-negative.' This staining response is based on the chemical and structural makeup of the cell walls of both varieties of bacteria. Gram-positives have a thick, relatively impermeable wall that resists decolorization and is composed of peptidoglycan and secondary polymers. Gram-negatives have a thin peptidoglycan layer plus an overlying lipid-protein bilayer known as the outer membrane, which can be disrupted by decolorization. Some bacteria have walls of intermediate structure and, although they are officially classified as Gram-positives because of their linage, they stain in a variable manner. One prokaryote domain, the Archaea, have such variability of wall structure that the Gram stain is not a useful differentiating tool. 相似文献
9.
Cecilia PC Soh Alastair SR Donald James Feeney Walter TJ Morgan Winifred M Watkins 《Glycoconjugate journal》1989,6(3):319-332
The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and1H-500 MHz NMR spectroscopy. In Sda serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity. 相似文献
10.
Major histocompatibility complex (MHC) class II genes, which play a major role in the immune system response, are some of the most polymorphic genes in vertebrates. We developed polymerase chain reaction primers for part of the second exon of an expressed MHC class II gene in the common frog, Rana temporaria. We genotyped this locus in five frog populations in southeast England and detected eight alleles in 215 individuals. Five or six alleles were detected in each population with a maximum of two alleles per individual, indicating that only a single locus was amplified. We also inferred the possible existence of a null allele. There were 23 variable nucleotide sites (out of 136) and 13 variable amino acid sites (out of 44), many of which corresponded to amino acids involved in antigen recognition. We detected a significant excess of nonsynonymous substitutions at antigen binding sites, indicating that this gene is under positive selection. The level of variation we found was similar to that in other amphibian MHC class II loci, such as those in Bombina bombina, Xenopus laevis and Ambystoma tigrinum. 相似文献