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1.
2.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:8,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献
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4.
Cultured chick embryo fibroblasts derived from skin and skeletal muscle exhibit hyaluronidase activity both associated with the cell layer and secreted into the medium. Although both forms of the enzyme have a number of similar characteristics (R.W. Orkin and B.P. Toole, 1980, J. Biol. CHem. 255), they differ in thermal stability at neutral pH and in behavior on ion-exchange chromatography. Both forms of the enzyme are equally stable at acidic pH for long intervals, but the cell-associated hyaluronidase is significantly less stable than the secreted froms at neutral pH and at temperatures more than or equal to 30 degrees C. Neither the presence of proteases nor inhibitors of hyaluronidase appear to be involved in the cell-asspcoated enzyme. Chromatography of the two forms of hyaluronidase on carboxymethyl cellulose reveals that most (60-90 percent) of the secreted form of the enzyme elutes at a lower ionic strength than the cell- associated enzyme. Treatment of the secreted form of hyaluronidase with neuraminidase shifts its elution profile on carboxymethyl cellulose toward that of the cell-associated form, and also decreases its thermal stability at neutral pH. In contrast, treatment of the secreted form of hyaluronidase with alkaline phosphatase has no detectable effect. These data suggest that the secreted hyaluronidase differs from the cellular form in possessing additional sialic acid residues which endow the former with increased stability in the extracellular milieu. 相似文献
5.
R Sibert 《BMJ (Clinical research ed.)》1975,3(5975):87-89
One hundred families of children under 5 years admitted to Cardiff Hospitals after accidentally ingesting poisons were compared with 100 control families matched for socioeconomic class and age and sex of the child. Questioning about five major stress factors (serious family illness, pregnancy, recent family moves, one parent away from home, anxiety or depression in one or both parents) disclosed significantly more stress in the affected families than in the controls. Thirty of the affected families had more than one major stress factor compared with four of the controls, while 63 of the controls had no major stress factor compared with 24 of the affected families (P less than 0.001). In only four of the affected families was there no stress factor. Fifteen children took poisons in homes other than their own. Unemployment was significantly more prevalent in the affected families than in the general population, though apart from this the socioeconomic backgrounds were similar. There were significantly more accidents and childhood poisonings in the parents and siblings of affected children than in the control families. In 25% of the cases poisoning was with Angiers Junior Aspirin. 相似文献
6.
The invasive freshwater snail Tarebia granifera (Lamarck, 1822) was first reported in South Africa in 1999 and it has become widespread across the country, with some evidence to suggest that it reduces benthic macroinvertebrate biodiversity. The current study aimed to identify the primary abiotic drivers behind abundance patterns of T. granifera, by comparing the current abundance of the snail in three different regions, and at three depths, of the highly modified Nseleni River in KwaZulu-Natal, South Africa. Tarebia granifera was well established throughout the Nseleni River system, with an overall preference for shallow waters and seasonal temporal patterns of abundance. Although it is uncertain what the ecological impacts of the snail in this system are, its high abundances suggest that it should be controlled where possible and prevented from invading other systems in the region. 相似文献
7.
A PBX1 transcriptional network controls dopaminergic neuron development and is impaired in Parkinson's disease 下载免费PDF全文
J Carlos Villaescusa Bingsi Li Enrique M Toledo Pia Rivetti di Val Cervo Shanzheng Yang Simon RW Stott Karol Kaiser Saiful Islam Daniel Gyllborg Rocio Laguna‐Goya Michael Landreh Peter Lönnerberg Anna Falk Tomas Bergman Roger A Barker Sten Linnarsson Licia Selleri Ernest Arenas 《The EMBO journal》2016,35(18):1963-1978
8.
RW Horobin 《Biotechnic & histochemistry》2002,77(1):3-13
New staining techniques continue to be introduced, and older ones continue to be used and improved. Several factors control specificity, selectivity and visibility of the end product in any procedure using dyes, fluorochromes, inorganic reagents or histochemical reactions applied to sections or similar preparations. Local concentration of the tissue target often determines the intensity of the observed color, as does the fine structure within the object being stained, which may facilitate or impede diffusion of dyes and other reagents. Several contributions to affinity control the specificity of staining. These include electrical forces, which result in accumulation of dye ions in regions of oppositely charged tissue polyions. Weaker short-range attractions (hydrogen bonding, van der Waals forces or hydrophobic bonding, depending on the solvent) hold dyes ions and histochemical end products in contact with their macromolecular substrates. Nonionic forces can also increase visibility of stained sites by causing aggregation of dye molecules. Covalent bonds between dye and tissue result in the strongest binding, such as in methods using Schiff's reagent and possibly also some mordant dyes. The rate at which a reagent gains access to or is removed from targets in a section or other specimen affect what is stained, especially when more then one dye is used, together or sequentially. Rate-controlled staining is greatly influenced by the presence and type of embedding medium, such as a resin, that infiltrates the tissue. The rates of chemical reactions are major determinants of outcome in many histochemical techniques. Selective staining of different organelles within living cells is accomplished mainly with fluorochromes and is controlled by mechanisms different from those that apply to fixed tissues. Quantitative structure-activity relations (QSAR) of such reagents can be derived from such molecular properties as hydrophilic-hydrophobic balance, extent of conjugated bond systems, acid-base properties and ionic charge. The QSAR correlates with staining of endoplasmic reticulum, lysosomes, mitochondria, DNA, or the plasma membranes of living cells. 相似文献
9.
William B. Milisen Glen K. Miller Stephen A. Benjamin Gary J. Sibert 《In vitro cellular & developmental biology. Plant》1988,24(10):972-980
Summary An explant culture procedure has been developed that makes it possible to measure the relative growth capacity of the epithelial
and mesenchymal cells of the canine thymus gland. Standardized growth conditions were obtained by size-grading thymic fragments
and counting to allow uniform fragment density during culture. After 6 d in culture, outgrowth from the fragments formed colonies
that could be classified into epithelial, mixed, or spindle cell type. Uniform fragment size and number in each flask allowed
calculation of the total plating efficiency, relative distribution of colony types, and mean colony diameters for thymic fragments
collected from fetuses (50 d of gestation), neonates (0 d postpartum), and juveniles (70 d postpartum). Data show age-related
changes in the proliferative capacity of the cells in all three colony types. The most significant difference was seen in
the epithelium, which showed a 30% reduction in mean colony diameter over the 2 wk between fetal and neonatal ages and a 23%
reduction over the postnatal period of 70 d. Significant reductions were seen in the other colony types as well. Because the
severity of the effect of many injurious agents is proportional to the rate of growth of the target cells, these data suggest
that the thymus gland of the fetus may be more sensitive to physical or chemical injury than is the neonate or adult.
Funding was provided by grants NCI CA36456, NCI T15CA09408, NIEHS ES07152 from the National Institutes of Health, Bethesda,
MD, and by USDA Animal Health and Disease Program (PL 95-113). 相似文献
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