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91.
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93.
Summary We have studied the responses of three human retinoblastoma cell lines (GM1232, Y79, and WERI-Rb1) to substratum-bound laminin
(LN), fibronectin (FN), or collagen (CN) in serum-containing medium. About 95% of the cells attached to poly-d-lysine (PN)-pretreated plastic surfaces either unbound or protein-bound within 1 h after plating. With PN-bound LN, GM1232
cells showed an outgrowth of processes and cell spread within 1 d, but very little was seen on PN-bound FN, CN, or unbound
PN even by Day 4. Both the percentage of cells with processes and the number of processes/cell were dependent on the amount
of LN bound to the surfaces at Day 4. On LN surfaces without PN pretreatment, by Day 2 most cells had formed floating aggregates
and were not attached to the surfaces. By Day 4 only a part of the peripheral cells of attached aggregates displayed process
outgrowth and cell spreading. Dibutyryl cyclic AMP (dbcAMP) maintained these effects of PN-bound LN, and promoted process
branching, cell spreading, and elongation with concomitant inhibition of cell growth. The percentage of cells with processes
was 83%. Y79 and WERI-Rb1 cells, passed for several years, showed little and weak response to PN-bound LN either in the absence
or presence of dbcAMP. These results indicate that the morphologic differentiation of GM1232 cells is elicited specifically
by PN-bound LN, and that dbcAMP maintains and promotes this differentiated status. 相似文献
94.
Interleukin‐17 family cytokines in protective immunity against infections: role of hematopoietic cell‐derived and non‐hematopoietic cell‐derived interleukin‐17s 下载免费PDF全文
Interleukin‐17 family cytokines, consisting of six members, participate in immune response in infections and autoimmune and inflammatory diseases. The prototype cytokine of the family, IL‐17A, was originally identified from CD4+ T cells which are now termed Th17 cells. Later, IL‐17A‐producing cells were expanded to include various hematopoietic cells, namely CD8+ T cells (Tc17), invariant NKT cells, γδ T cells, non‐T non‐B lymphocytes (termed type 3 innate lymphoid cells) and neutrophils. Some IL‐17 family cytokines other than IL‐17A are also expressed by CD4+ T cells: IL‐17E by Th2 cells and IL‐17F by Th17 cells. IL‐17A and IL‐17F induce expression of pro‐inflammatory cytokines to induce inflammation and anti‐microbial peptides to kill pathogens, whereas IL‐17E induces allergic inflammation. However, the functions of other IL‐17 family cytokines have been unclear. Recent studies have shown that IL‐17B and IL‐17C are expressed by epithelial rather than hematopoietic cells. Interestingly, expression of IL‐17E and IL‐17F by epithelial cells has also been reported and epithelial cell‐derived IL‐17 family cytokines shown to play important roles in immune responses to infections at epithelial sites. In this review, we summarize current information on hematopoietic cell‐derived IL‐17A and non‐hematopoietic cell‐derived IL‐17B, IL‐17C, IL‐17D, IL‐17E and IL‐17F in infections and propose functional differences between these two categories of IL‐17 family cytokines. 相似文献
95.
96.
Nucleotide sequence and replication properties of the Bacillus borstelensis cryptic plasmid pHT926. 下载免费PDF全文
S Ebisu Y Murahashi H Takagi K Kadowaki K Yamaguchi H Yamagata S Udaka 《Applied microbiology》1995,61(8):3154-3157
The nucleotide sequence of pHT926, a cryptic plasmid found in Bacillus borstelensis HP926, was determined. pHT926 replicates by a rolling-circle mechanism and belongs to the pC194 plasmid family. The copy number of pHT926 was fourfold higher than that of pUB110 and very stably maintained in Bacillus choshinensis. 相似文献
97.
Soil properties and above-and belowground forest structure were studied across various topographies in a 20-year-oldPinus thunbergii Parl. plantation on Mt Tanakami, Japan. The soil properties and stand structure varied greatly with slope position fromridge
top to valley floor. Soil thickness, fine soil content and soil moisture content were greater in lower slope positions. The
amount of organic carbon in the forest floor was greater in upper slope positions. The organic carbon content in the mineral
soil was slightly greater in lower slope positions. These changes in soil properties suggested an upslope decrease in decomposition
rate and water and/or nutrient availability. The aboveground structure ofP. thunbergii was more developed at lower slope positions. The mean stem diameter, height and volume ofP. thunbergii increased downslope with decreasing tree density. However, fine root biomass increased greatly upslope. This inverse relationship
between tree height and fine root biomass indicated morphological plasticity ofP. thunbergii in exploiting environmental heterogeneity. Variations in soil-plant interactions in the stand along various topographies
caused spatial heterogeneity in the accumulation pattern of organic matter in plants and the soil. 相似文献
98.
Isolation and purification of Flavobacterium alpha-1,3-glucanase-hydrolyzing, insoluble, sticky glucan of Streptococcus mutans. 总被引:5,自引:1,他引:4 下载免费PDF全文
Studies were made on the physical and chemical properties of polysaccharides synthesized by cell-free extracts of Streptococcus mutans, Streptococcus sanguis, and Streptococcus sp. and their susceptibilities to dextranases. Among the polysaccharides examined, insoluble glucans were rather resistant to available dextranase preparations, and the insoluble, sticky glucan produced by S. mutans OMZ 176, which could be important in formation of dental plaques, was the most resistant. By enrichment culture of soil specimens, using OMZ 176 glucans as the sole carbon source, an organism was isolated that produced colonies surrounded by a clear lytic zone on opaque agar plates containing the OMZ 176 glucan. The organism was identified as a strain of Flavobacterium and named the Ek-14 bacterium. EK-14 bacterium was grown in Trypticase soy broth, and an enzyme capable of hydrolyzing the OMZ 176 glucan was concentrated from the culture supernatant and purified by negative adsorption on a diethylaminoethyl-cellulose (DE-32) column and gradient elution chromatography with a carboxymethyl-cellulose (CM-32) column. The enzyme was a basic protein with an isoelectric point of pH 8.5 and molecular weight of 65,000. Its optimum pH was 6.3 and its optimal temperature was 42 C. The purified enzyme released 11% of the total glucose residues of the OMZ 176 glucan as reducing sugars and solubilized about half of the substrate glucan. The products were found to be isomaltose, nigerose, and nigerotriose, with some oligosaccharides. The purified enzyme split the alpha-1,3-glucan endolytically and was inactive toward glucans containing alpha-1,6, alpha-1,4, beta-1,3, beta-1,4, and/or beta-1,6 bonds as the main linkages. 相似文献
99.
Hapten-inhibition studies showed that 3-O-methyl-D-glucose andmethyl--D-mannopyranoside, which are strong sugar haptens ofhemagglutination by pea seed lectins, inhibited (a) bindingof pea seed lectins with Rhizobium leguminosarum J357 cells,(b) the precipitin reaction of pea seed lectins with a capsularpolysaccharide from J357 cells and (c) adsorption of J357 cellsto a pea root. When the capsular polysaccharide was absorb edby the lectins or oxidized by periodate to remove the precipitinreactivity with the lectin, the inhibitory activity of the capsularpolysaccharide towards the adsorption disappeared. I.ectins,which were isolated from the bathing solution of pea roots inacid buffer (pH 2.1), were similar to the seed lectins in sugar-bindingspecificity. The possible existence of lectins on pea root hairsurface was shown by the indirect imraunofluorescent antibodytechnique in combination with the biotin-avidin system. Theseresults suggest that host recognition in Rhizobium-pea. symbiosisis based on the interaction between rhizobial cells and hostlectins.
1Present address: Nodai Research Institute, Tokyo Universityof Agriculture, Setagaya-ku, Tokyo 156, Japan. (Received February 18, 1981; Accepted May 2, 1981) 相似文献
100.
Nutrient mobility in variable- and permanent-charge soils 总被引:5,自引:2,他引:3
Variable-charge (v-c) and permanent-charge (p-c) soils differ fundamentally with regard to many nutrient-cycling processes. Variable-charge soils are more common in the tropics than in temperature zones because their formation requires desilication, which proceeds fastest in warm, moist climates. The dynamics of nutrient mobility tend to be more complex in v-c than in p-c soils. For example, theory predicts that, as pH of v-c soils decreases, cation exchange capacity (CEC) also decreases and anion exchange capacity (AEC) increases. If AEC exceeds CEC, cations such as ammonium and potassium will be more mobile than anions such as nitrate; this is the reverse of the situation in p-c soils, on which most of our knowledge of nutrient cycling is based. Variable-charge surfaces sorb phosphorus, creating plant nutritional problems throughout large areas of the humid tropics. Desilication, the same process that creates v-c surfaces, results also in stable aggregation, creating soils that retain water, yet drain rapidly and resist erosion. The Soil Taxonomy system incorporates information on mineralogy, texture, and organic matter content, and therefore provides insights into patterns of charge chemistry and nutrient cycling across a wide range of soil types. 相似文献