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61.
62.
63.
Both the Entamoeba histolytica lectin, a virulence factor for the causative
agent of amebiasis, and the mammalian hepatic lectin bind to
N-acetylgalactosamine (GalNAc) and galactose (Gal) nonreducing termini on
oligosaccharides, with preference for GalNAc. Polyvalent GalNAc-
derivatized neoglycoproteins have >1000-fold enhanced binding affinity
for both lectins (Adler,P., Wood,S.J., Lee,Y.C., Lee,R.T., Petri,W.A.,Jr.
and Schnaar,R.L.,1995, J. Biol. Chem ., 270, 5164-5171). Substructural
specificity studies revealed that the 3-OH and 4-OH groups of GalNAc were
required for binding to both lectins, whereas only the E.histolytica lectin
required the 6-OH group. Whereas GalNAc binds with 4-fold lower affinity to
the E.histolytica lectin than to the mammalian hepatic lectin,
galactosamine and N-benzoyl galactosamine bind with higher affinity to the
E. histolytica lectin. Therefore, a synthetic scheme for converting
polyamine carriers to poly-N-acyl galactosamine derivatives (linked through
the galactosamine primary amino group) was developed to test whether such
ligands would bind the E.histolytica lectin with high specificity and high
affinity. Contrary to expectations, polyvalent derivatives including
GalN6lys5, GalN4desmosine, GalN4StarburstTMdendrimer, and
GalN8StarburstTMdendrimer demonstrated highly enhanced binding to the
mammalian hepatic lectin but little or no enhancement of binding to the
E.histolytica lectin. We propose that the mammalian hepatic lectin binds
with greatest affinity to GalNAc "miniclusters," which mimic branched
termini of N-linked oligosaccharides, whereas the E.histolytica lectin
binds most effectively to "maxiclusters," which may mimic more widely
spaced GalNAc residues on intestinal mucins.
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64.
Marker assisted selection using best linear unbiased prediction 总被引:1,自引:0,他引:1
65.
An optimal division of a key resource between growth and reproductionis expected to produce consistent life history schedules inhabitats where its supply is highly predictable. However, differentialgrowth rates are found between populations and within broodsof Cantareus aspersus, a simultaneous hermaphrodite for whichthe reproductive benefits of a large body size may favour rapidgrowth. Although energy is usually assumed to be the limitingresource in allocation theory, calcium limits the distribution,growth and reproduction of snails. This is a very consistentresource and populations may have allocation strategies whichreflect availability in their habitats. Three experiments comparedCa allocation in the progeny of six populations from Ca-richand Ca-poor habitats. In the first, 100 d-old juveniles werecompared between populations for their shell/soft-tissue dryweight ratio, their allocation of Ca to each compartment, andthe variability within broods. The second measured growth, foodconsumption and shell ratios in growth trials of three populationson low Ca. Thirdly, five populations were compared on abundantor excess Ca. The relationship of shell Ca with soft-tissuelevels differs between populations, but shell ratios changedwith Ca availability in all populations. Most favoured soft-tissuegrowth when dietary Ca is low, but one population (LE) alwayshad the highest shell ratios in these trials. Ca in the parentalhabitat was not a good predictor of juvenile-allocation strategies,but the consistency of LE shell ratios across several broodssuggests theirs may be an inherited trait. LE has faster growthrates and a preference for shell building, which probably representsa strategy for early reproduction. The robustness of a snail'sshell may thus be more indicative of its reproductive strategyrather than Ca availability in its habitat. (Received 18 May 2006; accepted 21 December 2006) 相似文献
66.
Ocaña-de Jesús RL AT Gutiérrez-Ibáñez JR Sánchez-Pale MD Mariezcurrena-Berasain G Velázquez-Garduño A Laguna Cerda I Rojas Puebla 《Phyton》2015,84(1):45-50
The aim of the current research was to determine tomato (Solanum lycopersicum L.) microbiological quality produced under greenhouse conditions in 5 municipalities of the State of Mexico. Studies were conducted during the 2013 production cycle to know the risks and apply prevention strategies prior to its consumption. A microbiological analysis of samples of irrigation water, soil and 100 tomato fruits variety cid was performed to determine Aerobic Mesophiles, Total Coliforms and Fecal Coliforms. The methodology used were those according to the Official Mexican Standards NOM- 109-SSA1-1994, NOM-110-SSA1-1994, NOM-092-SSA1-1994, NOM-113-SSA1-1994, and the Regulations of the National French Organization for Standardization (AFNOR) NF V08-60, and NOM-093-SSA1-1994, which establish the allowable limits for the study microorganisms. The results showed a zero level of pollution in water and soil samples. For fruits, levels of Aerobic Mesophilic were within the maximum limits permitted by the standards. The municipality of Texcaltitlan showed the highest average for these microorganisms (10083.80 CFU/mL). Huixquilucan showed 2266.84 CFU/mL for Total Coliforms. For Fecal Coliforms, municipalities of Coatepec and Texcaltitlan exceeded the allowed limit. 相似文献
67.
Lena Hoffmann Lingling Li Katharina Herr Amanda J. Wilson Morgan Beeby Jörg Schaber Sonja‐Verena Albers 《Molecular microbiology》2017,103(1):181-194
Organisms have evolved motility organelles that allow them to move to favourable habitats. Cells integrate environmental stimuli into intracellular signals to motility machineries to direct this migration. Many motility organelles are complex surface appendages that have evolved a tight, hierarchical regulation of expression. In the crenearchaeon Sulfolobus acidocaldarius, biosynthesis of the archaellum is regulated by regulatory network proteins that control expression of archaellum components in a phosphorylation‐dependent manner. A major trigger for archaellum expression is nutrient starvation, but although some components are known, the regulatory cascade triggered by starvation is poorly understood. In this work, the starvation‐induced Ser/Thr protein kinase ArnS (Saci_1181) which is located proximally to the archaellum operon was identified. Deletion of arnS results in reduced motility, though the archaellum is properly assembled. Therefore, our experimental and modelling results indicate that ArnS plays an essential role in the precisely controlled expression of archaellum components during starvation‐induced motility in Sulfolobus acidocaldarius. Furthermore they combined in vivo experiments and mathematical models to describe for the first time in archaea the dynamics of key regulators of archaellum expression. 相似文献
68.
DOMINIK LERMEN BRUNHILDE BLÖMEKE ROBERT BROWNE ANN CLARKE PAUL W. DYCE THOMAS FIXEMER GÜNTER R. FUHR WILLIAM V. HOLT KATARINA JEWGENOW RHIANNON E. LLOYD STEFAN LÖTTERS MARTIN PAULUS GORDON MCGREGOR REID DANIEL H. RAPOPORT DAVID RAWSON JENNIFER RINGLEB OLIVER A. RYDER GABRIELE SPÖRL THOMAS SCHMITT MICHAEL VEITH PAUL MÜLLER 《Molecular ecology》2009,18(6):1030-1033
Cryobanking, the freezing of biological specimens to maintain their integrity for a variety of anticipated and unanticipated uses, offers unique opportunities to advance the basic knowledge of biological systems and their evolution. Notably, cryobanking provides a crucial opportunity to support conservation efforts for endangered species. Historically, cryobanking has been developed mostly in response to human economic and medical needs — these needs must now be extended to biodiversity conservation. Reproduction technologies utilizing cryobanked gametes, embryos and somatic cells are already vital components of endangered species recovery efforts. Advances in modern biological research (e.g. stem cell research, genomics and proteomics) are already drawing heavily on cryobanked specimens, and future needs are anticipated to be immense. The challenges of developing and applying cryobanking for a broader diversity of species were addressed at an international conference held at Trier University (Germany) in June 2008. However, the magnitude of the potential benefits of cryobanking stood in stark contrast to the lack of substantial resources available for this area of strategic interest for biological science — and society at large. The meeting at Trier established a foundation for a strong global incentive to cryobank threatened species. The establishment of an Amphibian Ark cryobanking programme offers the first opportunity for global cooperation to achieve the cryobanking of the threatened species from an entire vertebrate class. 相似文献
69.
70.
Several fundamental questions remain enigmatic concerning human olfactory
sensitivity, including (i) whether detection threshold differences exist
between the two sides of the nose (and, if so, whether such differences are
influenced by handedness) and (ii) whether bilateral (i.e. binasal)
stimulation leads to lower thresholds than unilateral stimulation (and, if
so, whether the degree of facilitation is inversely related to general
olfactory ability). In this study, and well-validated single staircase
procedure was used to establish bilateral and unilateral detection
thresholds for the cranial nerve I stimulant phenyl ethyl alcohol in 130
right- and 33 left-handed subjects. No differences in sensitivity between
the left and right sides of the nose were observed in either group.
Bilateral thresholds were lower, on average, than unilateral thresholds
when the latter were categorized in terms of left and right nares. However,
the bilateral thresholds did not differ significantly from those of the
side of the nose with the lower threshold. Overall smell ability, as
measured by the University of Pennsylvania Smell Identification Test, did
not interact with any of the test measures. These data imply that (i) the
left and right sides of the nose do not systematically differ in detection
threshold sensitivity for either dextrals or sinistrals and (ii) if central
integration of left:right olfactory threshold sensitivity occurs, its
effects do not exceed the function of the better side of the nose.
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