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排序方式: 共有372条查询结果,搜索用时 187 毫秒
1.
H. M. Koop M. Valentijn-Benz A. V. Nieuw Amerongen P. A. Roukema J. De Graaff 《Antonie van Leeuwenhoek》1989,55(3):277-290
Twenty-seven oral strains of the genera Actinomyces (5), Bacteroides (3), and Streptococcus (19) were tested for aggregation by human whole saliva, as well as the effect of culture medium, Ca-ions, and bacteria concentration thereupon. Of the media tested, GF-broth gave rise to less interference by autoaggregation or higher aggregation titers than BHI and TSB, and was used throughout this study. In most cases, Ca-ions (1 mM) only enhanced the rate of induced aggregation, whereas raising the bacteria concentration increased the rate of both induce- and autoaggregation. The final titers, ranging from 1–64, were hardly affected by these parameters, except those of S. rattus HG 59 and S. mutans HG 199, which were respectively increased and decreased by Ca-ions. Saliva-induced aggregation was observed for 21 strains of A. viscosus, A. naeslundii, A. israelii, B. gingivalis, B. intermedius, S. cricetus, S. mutans, S. rattus, S. sanguis, and S. sobrinus, mostly within 15 min to 3 h. Seventeen of these strains also showed autoaggregation, usually well after the onset of induced aggregation. Any potential induced aggregation of B. gingivalis HG 91 was always masked by autoaggregation, as well as that of the S. mutans strains under a particular set of conditions. The aggregation rate and titer varied considerably in a mutually unrelated and strain-dependent way. These microtiterplate data were matched by the 5 spectrophotometric patterns observed for saliva-bacterial interaction, which moreover, gave the better differentiation between induced and autoaggregation. In conclusion, most strains tested can show rapid saliva-induced aggregation in a strain-dependent way, yet strongly affected by the experimental conditions and interference from autoaggregation. 相似文献
2.
Ion accumulation in the cell walls of rice plants growing under saline conditions: evidence for the Oertli hypothesis 总被引:10,自引:3,他引:7
Abstract. When plants of rice ( Oryza saliva L.) are subjected to mildly saline (50mol m−3 NaCl) conditions, the leaves show symptoms of water deficit, even though ion accumulation has been more than sufficient to adjust to the decrease in external water potential. After a few days of exposure to salt, there is a negative correlation, in a population of leaves, between the leaf water concentration (g water per g dry weight) and their sodium concentration (mmol Na per g dry weight). Ion concentrations in the cell walls and the cytoplasm of cells of plants grown in low salinity were measured by X-ray microanalysis. The NaCl concentration in solution in the apoplast was calculated to be around 600mol m−3 in leaves of plants whose roots were exposed to only 50 mol m−3 NaCl. This constitutes strong evidence that an important factor in salt damage in rice is dehydration due to the extracellular accumulation of salt as suggested in the Oertli hypothesis. The implication, that changes in tissue ion concentration and solute potentials equivalent to the external medium is not evidence of plant osmotic adjustment to salinity, is discussed. 相似文献
3.
Comparative studies of diurnal variations of nitrate reductase activity in wheat, oat and barley 总被引:1,自引:0,他引:1
Diurnal variations of in vitro and in vivo (intact tissue assay) nitrate reductase (EC 1.6.6.1) activity and stability were examined in leaves of wheat ( Triticum aestivum L. cv. Runar), oat ( Avcna saliva L. cv. Mustang) and barley ( Hordeum vulgure L. cv. Agneta and cv. Gunillu). Nitrate reductase activity was generally higher for wheat than for oat and barley. However, the diurnal variations of nitrate reductase activity and stability were principally the same for all species, e.g. the high activity during the photoperiod was associated with low stability. All species showed a rapid (30-60 min) increase in the in vitro and in vivo activity when the light was switched on. When light was switched off the in vitro activity decreased rapidly whereas decrease in in vivo activity was slower. These experiments support the hypothesis that an activation/ deactivation mechanism is involved in the regulation of diurnal variations in nitrate reductase activity. Red light enhanced nitrate reductase activity in etiolated wheat and barley leaves. In green leaves, however, the daily increase in nitrate reductase activity was not induced by a brief red light treatment. Indications of different regulation mechanisms for the diurnal variations of nitrate reductase activity among the cereals were not found. 相似文献
4.
Interaction of the salivary low-molecular-weight mucin (MG2) with Actinobacillus actinomycetemcomitans 总被引:2,自引:0,他引:2
J. Groenink A. J. M. Ligtenberg E. C. I. Veerman J. G. M. Bolscher A. V. Nieuw Amerongen 《Antonie van Leeuwenhoek》1996,70(1):79-87
Periodontitis is associated with the presence of certain Gram-negative bacteria in the oral cavity, among these Actinobacillus actinomycetemcomitans. In order to determine which types of salivary components interact with A. actinomycetemcomitans two strains (HG 1175 and FDC Y4) were incubated with whole saliva and individual glandular secretions, viz. parotid, submandibular, and sublingual saliva. Immunochemical analysis by immunoblotting of bacteria-bound salivary proteins showed that IgA, the low-molecular mucin MG2, parotid agglutinin, and a 300 kDa sublingual and submandibular glycoprotein, were bound to the bacterial strains tested. In addition, adherence of A. actinomycetemcomitans to salivary proteins in a solid-phase was studied. After electrophoresis and transfer of salivary proteins to nitrocellulose membranes A. actinomycetemcomitans adhered only to MG2. In this assay periodate treatment, mild acid hydrolysis or neuraminidase digestion of the saliva glycoproteins abolished binding of two clinical isolates (HG 1175 and NY 664), suggesting that sialic acid residues on MG2 are involved in the binding. In contrast, adherence of the smooth laboratory strain Y4 was not affected by removal of sialic acid residues or even periodate treatment of MG2.Abbreviations S-IgA
Secretory IgA
- MG1
high-molecular-weight mucin
- MG2
low-molecular-weight mucin
- EP-GP
extra parotid-glycoprotein
- PRPs
proline-rich proteins
- SNA
Sambucus nigra agglutinin
- MAA
Maackia amurensis agglutinin
- PNA
peanut agglutinin
- UEA
Ulex europaeus agglutinin 相似文献
5.
本文将昆明地区11-15岁健康儿童90名按不同的口腔条件分为三组,每组30人。采用培养基表面主培养主数法,分别测定唾液中厌氧菌和需氧菌细菌总数。结果表明:儿童唾液中细菌总数,牙颌畸形组、正畸组、正常组,三组间结果在统计学无显著差异。 相似文献
6.
7.
Isoelectric focusing was performed on parotid salivas selected for their electrophoretic phenotypes of proline-rich acidic salivary proteins. Fractions encompassing narrow pH regions were pooled and examined by polyacrylamide gel electrophoresis. Isoelectric focusing yielded partial purification of major and minor acidic proline-rich proteins which were subsequently compared by immunoelectrophoresis and double immunodiffusion against goat anti-human parotid saliva. Cross-reactivity without spurring between all fractions containing major Pr proteins in both immunoelectrophoresis and double immunodiffusion suggests that these proteins are immunologically very similar or identical.This study was supported in part by an award from the American Cancer Society Institutional Grant IN-88F to Fels Research Institute. 相似文献
8.
Oryza sativa L. var. bahia coleoptile cell walls show sufficient autolytic activity for the release into the surrounding medium of amounts up to 60 μg of sugars per mg of dry weight of cell wall. The products released elute in Bio-gel P.2 as mono- and polysaccharides with glucose as the sole component. The polysaccharide component releases tri- and tetrasaccharides on treatment with a glucanase specific for β (1–3) (1–4) linkages in the same proportion as that of the mixed glucan of the cell wall. This supports the hypothesis that the polysaccharide component originates from the cell wall glucan and that autolysis is therefore related to the processes of the loss of rigidity of the cell wall. Nojirimycin (a specific glucanase inhibitor and inhibitor of auxin-induced elongation) decreases autolytic activity of the cell walls, reducing it to 30% of its normal value. Bio-gel P. 2 elution of the products released in autolysis in the presence of nojirimycin shows that only the monosaccharide fraction was affected. 相似文献
9.
Abstract. The proposal that rapidly elongating plant cells cannot maintain plasma membrane synthesis by means of the normal endomembrane system has been examined in elongating segments of Avena sativa coleoptiles. Segments were sampled and fixed for electron microscopy, before and after elongation on auxin solutions. Mean cell extensions, cytoplasmic volumes, dictyosomc numbers, and vesicle sizes and numbers were determined. It was shown that there are sufficient dictyosomes present to sustain the vesicle production necessary for the observed plasma membrane extension. 相似文献
10.
Genetic polymorphism of the major glycoprotein (Gl) found in parotid saliva is determined by autosomal inheritance of one unexpressed and four expressed alleles. This hypothesis is supported by studies in 41 white families including 146 children. For 143 randomly collected salivas from whites and 82 randomly collected salivas from blacks, maximum likelihood estimates of the gene frequencies are as follows: for whites, Gl
1=0.742, Gl
2=0.040, Gl
3=0.155, Gl
4=0.017, Gl
0=0.046; for blacks, Gl
1=0.459, Gl
2=0.050, Gl
3=0.337, Gl
4=0.044, Gl
0=0.110. There is strong evidence for linkage of Gl/Pr (seven families, lod score at =0 is 5.24) and Gl/Db (eight families, lod score at =0 is 4.45). The allelic products of Gl show evidence for linkage disequilibrium with the products of the Pr, Db, and Pa loci (P<0.0005). On the basis of varying degrees of linkage disequilibrium, Gl may be closer to Db than to Pr or Pa and on the outside of Db with respect to Pr or Pa. Amino acid analyses of Gl 1 and Gl 4 proteins show strong resemblances in composition to the major basic glycoprotein and the acidic proline-rich proteins of parotid saliva described by other workers. The polymorphic forms of the Gl proteins show microheterogeneity due to variability in charge and molecular weight. The electrophoretic polymorphism appears to be determined by apparent differences in molecular weights between the Gl proteins.This study was supported by a grant from the National Institutes of Dental Research (DEO 3658-12) and in part by NIH Grant GM 15422 and NIH Training Grant GM 00398. Paper No. 2242 of the Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706. 相似文献