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21.
Dipl. Geol. Volker Thiel Dr. Martina Merz-Preiß Prof. Dr. Joachim Reitner PD Dr. Walter Michaelis 《Facies》1997,36(1):163-172
Summary Biomarker investigations are applied to the free lipid fractions of a naturally grown freshwater microbial mat, constructed
by calcifying cyanobacteria (Scytonema sp. andSchizothrix sp.). The absolute and relative concentrations of hydrocarbons, free alcohols and carboxylic acids are studied and their
probable biological precursors are discussed. A significant signal of cyanobacterial lipids is recognized by the strong predominance
ofn-heptadecane (C17),n-heptadecene, two monomethyl-heptadecanes, and the pentacyclic triterpenoid diploptene. Their occurrences parallel the lipid
distributions found in pure cultured cyanobacteria and in recent cyanobacterial mats grown in particular environments (hypersaline,
lagoonal, hot spring). The observed compound signature appears to be a suitable reference for environments, where cyanobacteria
are directly associated with theloci of carbonate precipitation and thus, rock formation. In the studied material, a significant contribution of organic matter
from other sources, especially higher plants is characterized by the occurrence of several specific marker compounds, namely
lup-20(29)-ene-3-ol, high molecular weightn-alkanes and carboxylic acids. Although these components comprise a notably high portion of the sample’s lipid inventory,
they are shown to be distinguished easily from the signal left by the predominant mat building organisms. 相似文献
22.
PD Dr. med. Hanspeter Rohr Ute Seitter Jürgen Schmalbeck 《Cell and tissue research》1968,85(3):376-397
Zusammenfassung Einer weiblichen Maus wurde 3 Tage post partum 750 C 3H-Leucin i. p. injiziert. Zu verschiedenen Zeiten nach der Leucinapplikation wurden dem leicht narkotisierten Tier Gewebeteile der Milchdrüse entnommen und zu elektronenmikroskopischen Autoradiogrammen verarbeitet. An Hand der dabei gewonnenen Ergebnisse wurde versucht, den zeitlichen Ablauf der Milcheiweißbildung rechnerisch zu erfassen. 5 und 15 min nach der 3H-Leucinapplikation kann die Aktivität über dem rauhen endoplasmatischen Retikulum, nach 30 min über dem Golgi-Feld, und nach 240 min zur Hauptsache über den Lumina der Ausführungsgänge beobachtet werden. Die Halbwertszeit von markierten Proteinen im Ergastoplasma errechnete sich zu etwa 22 min, diejenige im Golgi-Feld zu etwa 3 Std.Die Voraussetzungen und derzeitigen Grenzen einer quantitativen elektronenmikroskopischen Autoradiographie werden diskutiert. Wegen der vielen möglichen Fehlerquellen wird die Berechnung der Kinetik der Milcheiweißbildung lediglich als Modell gewertet.
Ausgeführt mit Unterstützung durch die Deutsche Forschungsgemeinschaft.
Wesentliche Teile der Arbeit werden Von Ute Seitter der Medizinischen Fakultät der Universität Freiburg i. Br. als Inaugural-Dissertation vorgelegt. 相似文献
Summary A female mouse, 3 days post partum, was injected with 3H-leucine. After various intervals parts of the mammary gland were processed for electronmicroscopic autoradiograms, the results of which were mathematically evaluated in order to understand the temporal course of milk protein formation. After 5 and 15 minutes the leucine-activity is located mainly in the rough endoplasmic reticulum, after 30 minutes in the Golgi field and after 240 minutes in the lumina of the mammary ducts. The half-live time of labelled proteins in the rough endoplasmic reticulum is about 22 minutes, in the Golgi field about 3 hours.The preconditions and limitations of quantitative electronmicroscopic autoradiography are discussed. Because of the many possible sources of error, the calculations of the kinetics of protein synthesis and secretion in the mammary gland are merely regarded as a model.
Ausgeführt mit Unterstützung durch die Deutsche Forschungsgemeinschaft.
Wesentliche Teile der Arbeit werden Von Ute Seitter der Medizinischen Fakultät der Universität Freiburg i. Br. als Inaugural-Dissertation vorgelegt. 相似文献
23.
Colin PD Birch Ambrose C Chikukwa Kieran Hyder Victor J Del Rio Vilas 《BMC veterinary research》2009,5(1):1-14
Background
This paper explores the spatial distribution of sampling within the active surveillance of sheep scrapie in Great Britain. We investigated the geographic distribution of the birth holdings of sheep sampled for scrapie during 2002 – 2005, including samples taken in abattoir surveys (c. 83,100) and from sheep that died in the field ("fallen stock", c. 14,600). We mapped the birth holdings by county and calculated the sampling rate, defined as the proportion of the holdings in each county sampled by the surveys. The Moran index was used to estimate the global spatial autocorrelation across Great Britain. The contributions of each county to the global Moran index were analysed by a local indicator of spatial autocorrelation (LISA). 相似文献24.
At Bird Island, South Georgia, we surveyed the distribution and abundance of ticks on the vertebrate fauna and found only 1 species Ixodes uriae. We classified all seabird species into 3 groups: (1) seabirds nesting on the surface of the ground solitarily, in dispersed groups of a few nests, or in colonies with well-spaced nests; (2) seabirds nesting on the surface of the ground in dense colonies; and (3) seabirds nesting in dense colonies in burrows or rock crevices. We detected I. uriae only on 3 species of the second group that nested in large, dense, persistent colonies, i.e., black-browed albatross (Diomedea melanophrys), gray-headed albatross (Diomedea chrysostoma), and macaroni penguin (Eudyptes chrysolophus). Ticks were found on the undersides of the feet on albatrosses but not on the undersides of the feet on penguins. We hypothesize that the coarse pebble nests of penguins, combined with the fact that their young walk around more than albatross young, make the environment on the underside of penguin feet more harsh and hostile for ticks than the underside of albatross feet. Despite the great abundance of Antarctic fur seals (Arctocephalus gazella) on the island, we found no ticks on them. 相似文献
25.
Rick PD; Hubbard GL; Kitaoka M; Nagaki H; Kinoshita T; Dowd S; Simplaceanu V; Ho C 《Glycobiology》1998,8(6):557-567
The polysaccharide chains of enterobacterial common antigen (ECA) consist
of linear trisaccharide repeat units with the structure -->3)-
alpha-d-Fuc4NAc-(1-->4)-beta-d-ManNAcA-(1-->
4)-alpha-d-GlcNAc-(1-->, where Fuc4NAc is 4-acetamido-4,
6-dideoxy-d-galactose, ManNAcA is N - acetyl-d- mannosaminuronic acid, and
GlcNAc is N -acetyl-d-glucosamine. The major form of ECA (ECAPG) consists
of polysaccharide chains that are believed to be covalently linked to
diacylglycerol through phosphodiester linkage; the phospholipid moiety
functions to anchor molecules in the outer membrane. The ECA trisaccharide
repeat unit is assembled as a polyisoprenyl-linked intermediate which has
been tentatively identified as Fuc4NAc-ManNAcA-GlcNAc-
pyrophosphorylundecaprenol (lipid III). Subsequent chain-elongation
presumably occurs by a block-polymerization mechanism. However, the
identity of the polyisoprenoid carrier-lipid has not been established.
Accordingly, the current studies were conducted in an effort to
structurally characterize the polyisoprenyl lipid-carrier involved in ECA
synthesis. Isolation and characterization of the lipid carrier was
facilitated by the accumulation of a ManNAcA-GlcNAc-
pyrophosphorylpolyisoprenyl lipid (lipid II) in mutants of Salmonella
typhimurium defective in the synthesis of TDP-Fuc4NAc, the donor of Fuc4NAc
residues for ECA synthesis. Analyses of lipid II preparations by fast atom
bombardment tandem mass spectroscopy (FAB-MS/MS) resulted in the
identification of the lipid-carrier as the 55-carbon polyisoprenyl alcohol,
undecaprenol. These analyses also resulted in the identification of a novel
glycolipid which copurified with lipid II. FAB-MS/MS analyses of this
glycolipid revealed its structure to be 1,2-diacyl- sn
-glycero-3-pryophosphoryl-GlcNAc-ManNAcA (DGP- disaccharide). An
examination of purified ECAPGby phosphorus-31 nuclear magnetic resonance
spectroscopy confirmed that the polysaccharide chains are linked to
diacylglycerol through phosphodiester linkage. Thus, DGP-disaccharide does
not appear to be an intermediate in ECAPGsynthesis. Nevertheless, although
the available evidence clearly indicate that lipid II is a precursor of
DGP-disaccharide, the function of this novel glycolipid is not yet known,
and it may be an intermediate in the biosynthesis of a molecule other than
ECAPG.
相似文献
26.
Summary The apical portion of the uterine lining of the ovoviviparous fire salamander, Salamandra salamandra, was studied by the freeze-fracture technique in conjunction with the polyene antibiotic filipin. Filipin-sterol complexes were found in the luminal plasmalemma and in the membranes limiting the mucous secretory granules typical of this epithelium. In all females, but particularly in non-pregnant females, more or less discrete clusters of filipinsterol complexes were occasionally found overlying heavily affected secretory granules. The findings are discussed with regard to comparable results (Orci et al. 1980) based on the examination of collapsed and stretched urinary bladders of toads.We are indebted to Mrs. K. Ott for excellent technical assistance, to Miss E.S. MacLure for linguistic corrections and to Dr. J.E. Grady of the Upjohn Co., Kalamazoo, Michigan USA, for kindly providing the filipin 相似文献
27.
Joubert syndrome generally represents an autosomal recessive and rarely X-linked disorder characterized by hypotonia, an irregular breathing pattern, abnormal eye movements, ataxia, developmental delay and a complex mid-hindbrain malformation causing the molar tooth sign on magnetic resonance imaging (MRI). Many patients have additional features, with nephronophthisis, retinal dystrophy, coloboma and hepatic fibrosis representing the most frequent features. Due to its clinical variability and overlap with other syndromes, the term “Joubert syndrome and related disorders” (JSRD) was proposed. To date 10 genes are known to cause JSRD. The encoded proteins are localized to cilia, linking JSRD to other human ciliopathies. 相似文献
28.
A bioinformatic approach was used for the identification of residues that are conserved within the Nramp family of metal transporters. Site-directed mutagenesis was then carried out to change six conserved acidic residues (i.e., Asp-34, Glu-102, Asp-109, Glu-112, Glu-154, and Asp-238) in the E. coli Nramp homolog mntH. Of these six, five of them, Asp-34, Glu-102, Asp-109, Glu-112, and Asp-238 appear to be important for function since conservative substitutions at these sites result in a substantial loss of transport function. In addition, all of the residues within the signature sequence of the Nramp family, DPGN, were also mutated in this study. Each residue was changed to several different side chains, and of ten site-directed mutations made in this motif, only P35G showed any measurable level of 54Mn2+ uptake with a Vmax value of approximately 10% of wild-type and a slightly elevated Km value. Overall, the data are consistent with a model where helix breakers in the conserved DPGN motif in TMS-1 provide a binding pocket in which Asp-34, Asn-37, Asp-109, Glu-112 (and possibly other residues) are involved in the coordination of Mn2+. Other residues such as Glu-102 and Asp238 may play a role in the release of Mn2+ to the cytoplasm or may be involved in maintaining secondary structure.This revised version was published online in June 2005 with a corrected cover date. 相似文献
29.
30.