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   1737篇
  免费   22篇
  国内免费   122篇
系统科学   5篇
丛书文集   98篇
教育与普及   308篇
理论与方法论   83篇
现状及发展   13篇
综合类   1374篇
  2024年   1篇
  2023年   14篇
  2022年   12篇
  2021年   13篇
  2020年   13篇
  2019年   14篇
  2018年   4篇
  2017年   10篇
  2016年   20篇
  2015年   30篇
  2014年   73篇
  2013年   62篇
  2012年   79篇
  2011年   76篇
  2010年   68篇
  2009年   75篇
  2008年   116篇
  2007年   106篇
  2006年   92篇
  2005年   114篇
  2004年   119篇
  2003年   123篇
  2002年   102篇
  2001年   93篇
  2000年   87篇
  1999年   78篇
  1998年   53篇
  1997年   39篇
  1996年   36篇
  1995年   33篇
  1994年   27篇
  1993年   20篇
  1992年   18篇
  1991年   13篇
  1990年   22篇
  1989年   16篇
  1988年   7篇
  1986年   1篇
  1985年   1篇
  1957年   1篇
排序方式: 共有1881条查询结果,搜索用时 93 毫秒
131.
邓志龙  倪德祥 《江西科学》1993,11(2):125-130
介绍了转基因植物的发展历史,已获得转基因植物的物种,转基因技术及转基因植物在生产上的应用.  相似文献   
132.
BYDVCP基因转化小麦原生质体及转基因植株再生   总被引:1,自引:0,他引:1  
用原生质体融合技术与PEG介导的直接转基因方法相结合,使高频率分裂的小麦济南177悬浮细胞系原生质体与具有分化能力的小麦济南177胚性愈伤组织原生质体融合,形成具有分裂和分化能力的融合细胞;同时,利用PEG对原生质体的直接转基因作用,将带有抗病基因的质粒P^pp15与带有抗性选择标记基因的质粒P^BlAetSN导入融合细胞中。经抗性筛选获得抗潮霉素的阳性克隆并再生植株。对再生植株作PCR检测表明,  相似文献   
133.
木槿愈伤组织耐盐细胞系是在含NaCl的培养基上通过屡代选择产生的,在无盐培养其中进行几代继代培养后的愈伤组织,由其分化的芽以及脱分化增殖的愈伤组织均表现了耐盐性,木槿耐盐细胞由于对NaCl的反应比未经选择的细胞积累了更多的N^+,K^+,而且细胞体积较小。  相似文献   
134.
用PEG法向小麦原生质体导入外源基因获得转基因植株   总被引:16,自引:0,他引:16  
郭光沁 《科学通报》1993,38(13):1227-1227
目前用基因工程方法改良小麦是世界上普遍关注的课题,但其有效外源基因转化系统的建立却十分困难.Vasil 等曾用基因枪法转化小麦悬浮细胞获得转化的愈伤组织;最近他们又用相同的方法转化小麦胚性愈伤组织得到了抗除草剂的小麦转基因植株.我们在小麦原生质体再生植株获得成功的基础上,通过反复实验,用 PEG 处理法将外源基因导入小麦原生质体,通过培养和对转化细胞的筛选,获得了完整的转基因小麦再生植株.  相似文献   
135.
两种小麦的原生质体培养再生植株   总被引:2,自引:0,他引:2  
  相似文献   
136.
Expression vector pBPC102, which carries winged bean lysine-rich protein (wblrp) gene and dihydropicolinate synthase (DHDPS) gene, was transferred into hexaploid winter wheat cv. Jinghua No.l, Jing411, You899 and Yangnongl5 explants of immature inflorescence and immature embryos by particle bombardment. More than 100 transgenic plants were obtained under the selection of s-(2-aminoethyl)-L-cysteine (AEC). Confirmed transgenic plants of To and TI generation by PCR and PCR-Southern blotting analyses showed successful integration of wblrp gene into wheat genome. Analysis of transgenic plant lines of T2 by Northern dot-blotting showed good expression of wblrp gene in offspring seed. The content of free lysine in leaves, contents of bound lysine and total proteins in seeds of T2 transgenie wheat lines were determined and analyzed. Among 34 tested transgenic lines, levels of free lysine content in leaves of 9 transgenic lines are 2~3times higher than un-trans-formed wild-type cultivars. Among 17 analyzed transgenic lines, bound lysine content of 4 transgenic lines is more than 10% higher than that of wild-type cultivars. Our research suggests that introducing wblrp gene into wheat is an effective way to improve its nutrition quality.  相似文献   
137.
Ice nucleation active(INA)bacteria are the most potent heterogeneous ice nuclei in nature,which have become an important biological resource for diverse applications.Many researches have proved that INA bacteria can raise the supercooling points(SCPs)of insect pests,then reduce their cold hardiness.However,INA bacteria‘s inefficient colonization on the surface or in the guts of insects,and the high incidence of frost injury induced by their release hampered the application of INA bacteria in controlling insect pests in agricultural fields.In this study,we constructed a recombinant plasmid mob-Tn5-iceA with the ability of broad-host-range conjugal mobilization and integration of the ina gene of icaA into chromosomal DNA of many gram-negative bacteria by Tn5 transposition.In addition,Ent.cloacae strains stably carrying iceA and expressing high ice nucleation activity(INA),even in the absence of antibiotic pressure,were constructed through conjugal mobilization and Tn5 transposition.Ent,cloacae strains have benn reported to be able to efficently colonize in the guts of insects,but have weak plant epiphytic ability.Therefore,these transgenic Ent.Cloacae may be promising candidates for control of insect pests in agricultural fields.  相似文献   
138.
Human lysozyme is a 130-aa (amino acid) alkaline polypeptide, and has both anti-bacterial and anti-viral properties which make it an important component of human natural immunity system. As a first step toward the ultimate goal of improving the anti-bacterial properties of bovine and ovine milk, a transgenic mouse that contains the genomic DNA sequence of the human lysozme gene has been generated for the first time. From 83 mice generated by microinjection, a total of 6 positive transgenic mice were identified by PCR and Southern blot. F1 mice positive for transgene in lines were also detected by PCR. This shows that transgene could be transmitted from founder transgenic mice to their offspring. Recombinant human lysozyme (rHlys) was found in the whey of 3 female positive transgenic mice by Western blot. The highest concentration of rHlys for transgenic mice was 0.2mg/mL. The antibacterial activity of the whey for transgenic mice was highly enhanced up to 0.4 times as much as that of human, while that of non-transgenic mouse was very low. Although the lysozyme activity of transgenic mice is still lower than that of human, the rHlys exhibits the same specific activity as that of human lysozyme. It provides a strong basis for further studies into the possible application of rHlys express in mammary gland.  相似文献   
139.
种子萌发法是检测外源抗性基因在转基因植物中的表达和分析外源抗性基因在转基因植物中遗传行为的简单而直接的方法,以转bar基因燕麦后代R2种子为材料,用不同体积分数的除草剂Challenge处理种子,萌发的幼苗经PCR和Southern dot blot鉴定,发现在0.03%的除草剂上萌发的幼苗,部分不含bar基因,而在0.07%和0.09%的除草剂上萌发的幼苗,均含bar基因。用0.07%的除草剂测  相似文献   
140.
一、危害症状 茶黄螨,又名白蜘蛛,主要发生在温暖地区,设施内蔬菜受害严重,主要危害茄子、辣椒、番茄、马铃薯、黄瓜、豆类等多种蔬菜及花卉和经济作物,以茄子、辣椒受害最为严重.成螨、若螨多集中在作物幼芽、嫩叶、花、幼果等处刺吸汁液.受害叶片背面呈灰褐色或黄褐色,具油质光泽,呈油渍状,叶片边缘向下卷曲,受害嫩茎、嫩枝变黄褐色,扭曲畸形,严重者植株顶部干枯;花、蕾受害重者不开花结果;果实受害则皮变褐变硬,常被人误认为是生理病害或病毒性病害.  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