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1.
李文渊 《农业图书情报学刊》2004,15(4):55-57
复合图书馆作为图书馆的一种发展形态,有其自身的特点和要求,有许多值得研究的内容。复合图书馆的读者服务工作是图书馆工作的出发点和各项业务工作的最终价值体现。文章分析了目前图书馆读者服务工作面临的形势,探讨了我们应采取的措施。 相似文献
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Components of the energy and heat balances were examined in two maize hybrids grown at three different plant densities (40, 70 and 100 thousand plants per hectare). One of the hybrids was drought tolerant, while the other was bred for cultivation under irrigated conditions. An increase in plant density influenced not only the size of the leaf area, but also the distribution of the leaves at various plant heights. The extinction coefficient, which provides a quantification of radiation penetration, was higher in the irrigated treatments. By contrast to the other two treatments, the plant canopy in the thinly sown stands remained open throughout the vegetation period, and thus behaved quite differently to the closed stands, making it impossible to compare them. Smaller albedo values were recorded for the hybrid bred for irrigation and in thinly sown stands. The low plant density allowed more energy to reach the soil, from which it was reflected, making a considerable contribution to the final temperature in the stand. The latent heat, in keeping with the quantity of water transpired, was the greatest in the densely sown stands. There was little difference between the latent heat values of the normal and dense stands in either hybrid, indicating that they both had a similar sensitivity to increased stand density. If sufficient water is available it would appear that the stand density could be increased even for the drought-tolerant hybrid. 相似文献
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M. Fladung 《Plant Breeding》1993,111(3):242-245
The iaaL gene of Pseudomonas syringae subsp. savastanoi encodes an indoleacetic acid-lysine synthetase which conjugates free indoleacetic acid (IAA) with lysine. lAA-lys is biologically less active than free IAA. The iaaL coding region was expressed under the control of the cauliflower mosaic virus 35S promoter and transgenic potato plants were produced (Spena et al. 1991). 35S iaaL potato plants are characterized by increased internodal length and epinastic bending of older leaves. In three greenhouse experiments with plants grown in pots of different size and in two growth chamber experiments tuber number increased in iaaL transgenic plants compared to untransformed and vector-transformed controls of the same genotype. The increase in tuber numbers observed under controlled conditions was reflected in tuber yield which increased in the pot grown transgenics. 相似文献
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表达序列标签(ESTs)及其应用 总被引:3,自引:0,他引:3
表达序列标签(ESTs)是指从(ESTcDNA文库中随机挑取克隆并对其3’或5’端进行单轮自动测序所获得的短cDNA库列,一般长度为300~500bp。要有效获取ESTs,必须对cDNA文库进行预处理,处理方法有衰减杂交法、均一化法和差异显示法。在dbEST中收录了大量各种生物的ESTs。ESTs广泛应用于鉴定基因、发现新基因、电子克隆、构建遗传学图谱、制备DNA芯片、分子标记、研究基因的差异表达及检验病原微生物等方面。 相似文献
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Modern biotechnology promises a number of new applications in animal breeding and production. Although conventional pig breeding has achieved a high level of efficiency and productivity numerous problems have been encountered with animal health and the loss of meat quality. Selection based on phenotypic performance data of individual animals does not take into account the importance of specific genes and their relevance within a complex regulatory system. In most cases it is therefore difficult to trace back the genetic origins of clinically important disorders. The application of genetic engineering techniques in pig production will facilitate diagnosis, improvement of productivity, and animal health by allowing direct genetic manipulation. Attention must be focussed on the physical and genetic analysis of the procine genome. The isolation and characterisation of genes, DNA-markers, polymorphic DNA-fragments, and their chromosomal assignment will be important prerequisites and tools for the elucidation of genetic disorders. Especially the detection of heterozygous carriers of recessive disorders and their elimination from the breeding stock will increase selection accuracy and decrease the generation intervals. But also the rapid and simple detection of infectious diseases, which is sometimes difficult if not impossible at present, will improve animal health and welfare. Although the production of transgenic animals either by DNA-microinjection into zygotes or the use of embryonal stem cells manipulated in vitro is less straightforward than DNA-based diagnosis it will play an important role in the direct manipulation of the porcine genome and genes. Breeding programmes including the use of transgenic livestock have already been developed. There is no doubt that genetic engineering has reached a degree of practical feasibility, allowing it to play an important role in pig breeding in particular and animal production in general. 相似文献
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对N×特青示范田中试区与肥料试验田各处理小区稻株分析结果表明:抽穗后,亚种间杂交稻N×特青比常规稻特青干物质生产能力强,灌浆速度快;地上部各器官占植株干重比例,前者叶片比重大于茎,后者茎比重大于叶。亚种间杂交稻对肥料反应敏感,抽穗后,干物质累积,植株高度,每穗总粒数和粒重均随施肥量增加而增加,在高肥区有利于进一步提高产量,但增施氮肥后,灌浆速度明显滞后。 相似文献
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In this study, the effects of nitrogen (N) rate (60, 120, 180 and 240 kg N ha?1 applied in three equal dressings at seeding and after the first and second cuttings) and stubble height (7, 14 and 21 cm) on the dry matter (DM) yield, crude protein (CP) content, and CP yield of a sorghum–sudangrass hybrid [Sorghum bicolor (L.) Moench × Sorghum sudanense (Piper) Stapf., cv. Pioneer 988] in the three‐cut system was investigated. The N rate had no significant effect in the first and third cuttings, but in the second cutting DM yields increased significantly with increase in N rate. The highest yield of 9.1 t ha?1 was obtained with 80 kg N ha?1 for the average of 2 years at the second cutting, but no significant difference was found among the 40, 60 and 80 kg N ha?1 rates. CP content and yield were not significantly affected by N rate at the first and third cuttings, but CP content and yield were significantly affected by application of N at the second cutting. Stubble height had a significant effect on CP content at the third cutting. However, it had no significant effect on CP content at the first and second cuttings. Stubble height had a significant effect on the CP yield at the first cutting, but no significant effect on CP yield at the second and third cuttings. 相似文献
9.
TSUYOSHI OHIRA HIDEKAZU KATAYAMA KATSUMI AIDA HIROMICHI NAGASAWA 《Fisheries Science》2003,69(1):95-100
ABSTRACT: Until now, six crustacean hyperglycemic hormones (CHH) designated Pej-SGP-I, -II, -III, -V, -VI and -VII have been characterized in the kuruma prawn Penaeus japonicus . All CHH consist of 72 amino acid residues and have an amidated carboxyl (C)-terminus. In the present study, we expressed Pej-SGP-III in methylotrophic yeast Pichia pastoris in order to obtain a large quantity of recombinant CHH possessing biological activity. A cDNA encoding Pej-SGP-III that had been previously cloned was processed by polymerase chain reaction (PCR) and the resulting product was ligated into an expression vector. Pichia pastoris was transformed with this vector after which a recombinant Pej-SGP-III was expressed having an additional amino acid residue (glycine) at the C-terminus (rPej-SGP-III-Gly), a form considered to be a putative precursor of this hormone. rPej-SGP-III-Gly secreted into the culture medium was purified by reversed-phase HPLC, and amidated using a peptidylglycine alpha-amidating enzyme. The amidated rPej-SGP-III (rPej-SGP-III) showed hyperglycemic activity in in vivo bioassay almost comparable to that of the natural Pej-SGP-III. rPej-SGP-III thus obtained will be a useful tool not only for its physiological study but also for the determination of its 3-D structure. 相似文献
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