全文获取类型
收费全文 | 559篇 |
免费 | 65篇 |
出版年
2023年 | 4篇 |
2020年 | 5篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 14篇 |
2014年 | 20篇 |
2013年 | 14篇 |
2012年 | 37篇 |
2011年 | 37篇 |
2010年 | 26篇 |
2009年 | 17篇 |
2008年 | 15篇 |
2007年 | 28篇 |
2006年 | 23篇 |
2005年 | 23篇 |
2004年 | 24篇 |
2003年 | 23篇 |
2002年 | 23篇 |
2001年 | 19篇 |
2000年 | 22篇 |
1999年 | 15篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1966年 | 3篇 |
1964年 | 5篇 |
1961年 | 3篇 |
1957年 | 4篇 |
1956年 | 5篇 |
1945年 | 3篇 |
排序方式: 共有624条查询结果,搜索用时 15 毫秒
1.
2.
Effect of Bacteriophage on Colonization of Sugarbeet Roots by Fluorescent Pseudomonas spp 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The colonization potential of two fluorescent Pseudomonas strains (M11/4, B2/6) that exhibit antifungal activity in vitro was studied on the roots of sugarbeet plants in a clay loam soil. The cell density of the introduced bacteria declined on the root system over a 16-day test period in nonsterile soil. Strain B2/6 declined at a significantly faster rate compared with M11/4. This loss in viability and difference in colonization ability between M11/4 and B2/6 was not observed in sterile soil. Nutrient deprivation induced by indigenous microorganisms was excluded as a key factor involved in the decline of the introduced bacteria on the basis that strains M11/4 and B2/6 retained viability when subjected to nutrient starvation conditions over a 16-day period. Experiments designed to test whether antagonism by indigenous microorganisms was responsible for the decline in the introduced fluorescent Pseudomonas sp. population revealed the presence of large numbers of bacteriophage in the soil capable of lysing strain B2/6. Reconstitution experiments carried out with sugarbeet seedlings inoculated independently with strains M11/4 and B2/6 and grown in sterile soil to which a soil phage filtrate had been added showed a significant decrease in the viability of strain B2/6 relative to M11/4. Phage antagonistic toward strain B2/6 were detected in 43% of soils taken from the major sugarbeet growing regions of Ireland. 相似文献
3.
4.
Summary twenty seven field experiments were conducted to determine if there were differences between five barley cultivars in their ability to utilize soil nutrients. There were significant differences among cultivars in yield of grain and in concentration of all macro and micro nutrients examined in both the whole plant and grain.Gateway ranked the highest for the concentration of Na, Mn, and Cu in the whole plant and was among the cultivars with highest concentration of Ca, Fe, and Zn. Centennial had generally the lowest concentration of all the nutrients determined in the whole plant. For the concentrations of Na, Mg, and Cu in grain Gateway ranked highest, but ranked third for the concentrations of K, Ca, Fe, Mn, and Zn in grain. Galt had the highest K and Mg concentration and lowest Mn, Cu and Zn concentration in grain. Except for K concentration in grain, Centennial had the lowest concentrations of all other cationic nutrients in grain.Yield of grain rather than nutrient concentration was the most important criteria in determining the ranking of nutrient yields per hectare. Because of its high grain yield, Bonanza produced the largest yield of micronutrient cations and was second to Galt in production of macronutrient cations, although it was lowest in macronutrient cation concentration. Similarly, Bonanza and Galt had the lowest protein concentration, but produced the highest yield of protein per hectare.The implications for animal nutrition of different levels of nutrients between cultivars are discussed. 相似文献
5.
An improved purification procedure, an alternative assay and activation of mevalonate kinase by ATP 总被引:1,自引:0,他引:1
An improved procedure for the purification of pig liver mevalonate kinase (ATP:mevalonate 5-phosphotransferase, EC 2.7.1.36) is described. A high-voltage electrophoresis assay was developed for mevalonate kinase. The procedure separates mevalonate from phosphomevalonate and also from diphosphomevalonate so that it can be used to measure the subsequent enzyme, phosphomevalonate kinase (EC 2.7.4.2). The assay has allowed the reassessment of the metal ion and nucleotide specificity of the pig liver enzyme. Some of the previously reported properties reflected those of the enzymes in the coupling assay rather than mevalonate kinase itself. A series of compounds were tested as activators or inhibitors of mevalonate kinase. It was found that ATP4-, arsenate and, to a smaller extent, inorganic phosphate activated the enzyme. At fixed MgATP2- (1 mM) concentrations the activation of mevalonate kinase by free ATP4- at pH 8.0 was observed at concentrations at up to 10-fold that of MgATP2- before causing any inhibition. The presence of free ATP4- resulted in a biphasic Lineweaver-Burke plot with apparent Km values for MgATP2- being 0.14 mM and 60 microM, respectively. Fluorescence measurements were consistent with the notion that the binding of excess ATP4- to the enzyme caused a conformational change. 相似文献
6.
B M O'Sullivan 《International journal for parasitology》1974,4(2):177-181
Effects of lactation on Trichostrongylus colubriformis infections in the guinea pig. International journal for Parasitology, 4: 177–181. An increase in parasite egg output occurred in lactating guinea pigs infected with Trichostrongylus colubriformis, compared with that of either non-lactating or nulliparous females similarly infected. The lactating animals carried more parasites than either of the other two groups both as fourth stage larvae 9 days after infection and as adults at the peak of egg output 19 days after infection. Both the nulliparous and the non-lactating female guinea pigs had more mast cells and eosinophils in the small intestinal mucosa than did the lactating females.The behaviour of T. colubriformis in the lactating guinea pig is considered to be substantially the same as that of the various nematodes which have been studied in the lactating ewe. 相似文献
7.
8.
Measurement of PGE2 as the methyl oxime by radioimmunoassay using a novel iodinated label 总被引:3,自引:0,他引:3
R W Kelly B J Graham M J O'Sullivan 《Prostaglandins, leukotrienes, and essential fatty acids》1989,37(3):187-191
A radioimmunoassay has been developed for prostaglandin E2 (PGE2) using methyl oxime (MOX) derivatisation and a novel 125Iodine radiolabel. PGE2-methyl oxime (PGE2-MOX) is coupled through an imide linkage to proline in a pro-gly-tyr or similar peptide rather than through the conventional amide linkage to histamine or tyrosine methyl ester. The main advantage of this method is that the imide linkage in the label does not resemble the amide link used in the original antigen and the conjugate is therefore readily displaced by the natural PGE2. This overcomes the traditional difficulty encountered in hapten RIAs where the antiserum has a higher affinity for the label than it has for the compound to be measured. The assay that has been developed using these modifications and a solid-phase second antibody separation step, is both sensitive (with a lower detection limit of 0.5 pg/tube), reliable and simple and has the advantage that methyl oximation of the sample protects the PGE from degrading prior to and during the assay. 相似文献
9.
We have used an antiserum to a synthetic peptide fragment of bovine chromogranin A (ChrgA)[Tyr0] bovine ChrgA (306-313): YLSKEWEDA, together with antibodies to proenkephalin-derived peptides, to measure the release of immunoreactive peptides from nicotine-stimulated cultured bovine adrenal chromaffin cells. Over a period of 6 hr the accumulation of YLSKEWEDA immunoreactivity and Met-enkephalin Arg6Gly7Leu8 (MERGL) immunoreactivity in the medium of 10 microM nicotine-stimulated cells was shown to be biphasic; the initial phase occurred in the first 15-30 min and the second phase reached a peak after 4 hr. In contrast, catecholamine release occurred monophasically over the initial 15-30 min. Investigation of the second phase of peptide accumulation revealed that it was due in part to nicotine-evoked exocytosis and in part to extracellular processing of high molecular weight precursor proteins. 相似文献
10.
Rho guanine nucleotide dissociation inhibitor protein (RhoGDI) inhibits exocytosis in mast cells. 总被引:5,自引:0,他引:5
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Introducing non-hydrolysable analogues of GTP into the cytosolic compartment of mast cells results in exocytotic secretion through the activation of GTP binding proteins. The identity and mechanism of action of these proteins are not established. We have investigated the effects of Rho GDP dissociation inhibitor (RhoGDI) on exocytosis induced by guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) in rat mast cells, introducing the protein into cells by means of a patch pipette and recording the progress of exocytosis by monitoring cell capacitance. To allow time for the protein to enter the cells and find its correct location, stimulation was provided 5-10 min after patch rupture by photolysing caged GTP-gamma-S included in the pipette solution. When bovine RhoGDI was introduced into mast cells, exocytosis was inhibited at concentrations of 200-400 nM for native protein and 800 nM to 8 microM for the recombinant form. Protein denatured by heat or N-ethylmaleimide treatment did not inhibit. In permeabilized cells, recombinant RhoGDI increased the rate at which cells lose their ability to respond to GTP-gamma-S. These data demonstrate that one or more small GTP binding proteins of the Rho family has a central role in the exocytotic mechanism in mast cells. 相似文献