首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   64篇
  免费   0篇
  国内免费   3篇
教育   51篇
科学研究   9篇
体育   5篇
综合类   2篇
  2022年   1篇
  2021年   1篇
  2019年   2篇
  2015年   1篇
  2014年   4篇
  2013年   2篇
  2012年   1篇
  2011年   2篇
  2010年   3篇
  2009年   3篇
  2008年   2篇
  2007年   5篇
  2006年   5篇
  2005年   2篇
  2004年   8篇
  2003年   12篇
  2002年   2篇
  2000年   1篇
  1997年   2篇
  1996年   2篇
  1995年   3篇
  1993年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有67条查询结果,搜索用时 15 毫秒
51.
将一种同时含C20-Δ5脂肪酸碳链延长酶(TFD5)基因和C22-Δ4脂肪酸碳链脱饱和酶(FAD4)基因的双基因共表达质粒转化于Saccharomyces cerevisiae中,形成了工程菌株SC.PYFTD5-FAD4.并对工程菌株SC.PYFTD5-FAD4进行了诱导表达,可直接转化底物二十碳五烯酸(EPA,20:5△5,8,11,14,17n-3)生成二十二碳五烯酸(DPA,22:5△4,7,10,13,16n-3)和二十二碳六烯酸(DHA,22:6△4,7,10,13,16,19n-3).  相似文献   
52.
Like many river basins in China, water resources in the Fudong Pai River are almost fully allocated. This paper seeks to assess and evaluate water resource problems using water evaluation and planning (WEAP) model via its application to Hengshui Basin of Fudong Pai River. This model allows the simulation and analysis of various water allocation scenarios and, above all, scenarios of users' behavior. Water demand management is one of the options discussed in detail. Simulations are proposed for diverse climatic situations from dry years to normal years and results are discussed. Within the limits of data availability, it appears that most water users are not able to meet all their requirements from the river, and that even the ecological reserve will not be fully met during certain years. But the adoption of water demand management procedures offers opportunities for remedying this situation during normal hydrological years. However, it appears that demand management alone will not suffice during dry years. Nevertheless, the ease of use of the model and its user-friendly interfaces make it particularly useful for discussions and dialogue on water resources management among stakeholders.  相似文献   
53.
紫外线复合Nd:YAG激光对Bacillus sp.产脂肪酶的诱变   总被引:3,自引:0,他引:3  
以Bacillus sp.为出发菌株,经过紫外线诱变,筛选出较稳定的菌株UV-4,其产脂肪酶活力较出发菌株提高了28%;UV-4经过YAG激光诱变处理,得到变株Y-1,其产酶能力在此基础上又提高了41%,且产酶水平较为稳定。  相似文献   
54.
INTRODUCTIONAnincreasingdemandfromconsumersforhealthyandlowcostmedicalshasledtothede velopmentofalternativemedicaltherapyagentsu  相似文献   
55.
Santalum album Linn. is an evergreen and hemi-parasitic tree, the heartwood-sandalwood of which was used during a long history in traditional Chinese medicine. Kuhnia rosmarinifolia Vent. is a good host for 1- or 2-year-old growing S. album. The interaction between S. album and K. rosmarinifolia is still little known. Many studies have been carried out on a number of plants for identification and diversity of endophytes. In this study, in total 25 taxa of endophytic fungi were isolated from the roots of S. album and the roots of K. rosmarinifolia. The most frequently isolated genera were Penicillium sp. 1 and Fusarium sp. 1 in the roots of S. album and K. rosmarinifolia, respectively. S. album is a root parasite of K. rosmarinifolia. The interesting result is that they apparently do not share the same endophytic fungi isolates. This study for the first time explored the content of endophytic fungi from S. album and K. rosmarinifolia, which provides important information for further studies.  相似文献   
56.
PSO312是从土壤分离的1个青霉菌株,生长中能产生不同酸碱性条件下显黄色与紫红色等天然色素物质.通过菌株固体平板上恒温培养,168h测定菌落直径的方法研究了温度、pH及碳、氮源对菌株(Penicilliumsp.)生长的影响.研究表明31℃为菌株生长的最适温度.31℃培养以pH2—3的最快,pH8—9生长次之,24℃培养以pH8—9生长最快,pH3—4其次.菌株以蛋白胨4g/L、牛肉膏4g/L、酵母膏2g/L及尿素2g/L为氮源培养的菌落直径分别为55.75mm、51.5mm、55.5mm及25.3mm.在(NH4)2SO4 2g/L、NH4NO3 3g/L、NaNO3 4g/L、KN034g/L用量之上培养生长最快,菌落直径分别为35mm、34mm、35mm、及32mm.葡萄糖、蔗糖用量30g/L、果糖20g/L及乳糖25g/L的生长速率最快,菌落直径分别为45mm、38mm、38mm及39mm.丙三醇与淀粉25g/L培养的菌落直径均为39mm.  相似文献   
57.
通过对广西疟原虫新种(Plasmodiumguangxiensesp.nov.)、三趾鹑疟原虫新种(Plasmodiumturnixsp.nov.)的红内期有性体和无性体电镜观察,结果表明2种的超微结构与前人报导的已知种的超微结构基本一致.  相似文献   
58.
A newly isolated strain EL31410, producing elastase (E.C3.4.4.7) with high elastolytic activity was identified as Bacillus sp. In the medium optimization, it was found that wheat bran and soybean flour hydrosate were the best crude carbon and nitrogen source for enzyme production, respectively. Addition of corn steep flour can affect the bacterium growth and elastase production. A fractional factorial design was applied to study the main factors that affect the enzyme production, and central composite experimental design and response surface methodology were adopted to derive a statistical model for the effect of wheat bran and soybean flour hydrosate on elastase production. The experimental results showed that wheat bran had positive effect but soybean flour hydrosate had negative effect, on enzyme production. An initial concentration of 3.4%(w/v) wheat bran and 9.4%(v/v) soybean flour hydrosate were found to be optimal for enzyme production in batch culture. The time course of elastase production in the optimized medium composition was also described.  相似文献   
59.
研究了影响难溶金属氢氧化物溶度积 (pKsp)大小的有关因素 ,基于逐步线性回归建立了一个pKsp与有关参数的定量关联模型 随后 ,根据金属离子在周期表中的区域及其结构差异进行了分组建模 ,相关系数R分别达到或接近优级水平 (0 994和 0 981) 对模型进行分析发现 ,影响氢氧化物pKsp 的最重要因素是离子电荷z和半径r  相似文献   
60.
以(NH4)2SO4为唯一氮源,经富集培养、平板涂布分离及平板划线纯化、摇瓶复筛等方法,从当地养殖池水体中分离、筛选氨氮降解菌。根据形态学、生理生化特征分析,对其进行归属鉴定,并研究其降解特性。通过对初步鉴定归属为沙雷氏菌属(Serratia.sp),命名为N-2的氨氮降解菌降解特性的研究,得到其最适降解条件:N-2利用(NH4):S04作唯一氮源时,最适碳源为蔗糖,降解温度为32—37℃,pH为7.0。在最适条件下,当NH4+-N初始质量浓度为50mg/L时,该菌培养至72h氨氮降解率可达97.4%。结果表明,该菌为高效氨氮降解菌,这种土著微生物在修复富营养化水体方面有较好的应用前景。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号