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   201篇
  免费   9篇
  国内免费   16篇
林业   12篇
农学   69篇
基础科学   15篇
  12篇
综合类   50篇
农作物   15篇
水产渔业   5篇
畜牧兽医   7篇
园艺   25篇
植物保护   16篇
  2024年   1篇
  2022年   2篇
  2021年   1篇
  2020年   3篇
  2019年   5篇
  2018年   2篇
  2017年   2篇
  2016年   12篇
  2015年   5篇
  2014年   8篇
  2013年   5篇
  2012年   2篇
  2011年   5篇
  2010年   6篇
  2009年   8篇
  2008年   10篇
  2007年   6篇
  2006年   7篇
  2005年   3篇
  2004年   7篇
  2003年   14篇
  2002年   9篇
  2001年   12篇
  2000年   6篇
  1999年   10篇
  1998年   4篇
  1997年   10篇
  1996年   8篇
  1995年   5篇
  1994年   2篇
  1993年   4篇
  1992年   9篇
  1991年   3篇
  1990年   4篇
  1989年   2篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1982年   4篇
  1981年   3篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   4篇
  1976年   2篇
排序方式: 共有226条查询结果,搜索用时 15 毫秒
31.
蔬菜棚室用自走式微型旋耕机的研究   总被引:7,自引:1,他引:7       下载免费PDF全文
为适应蔬菜大棚的大规模发展对农机具的需求,在分析无驱动轮旋耕的力学机理和功率消耗的基础上,根据蔬菜棚室内作业对农机具的要求和目前菜农的技术条件与经济条件,设计和研制了一种微型旋耕机。该机用无驱动轮旋耕的工作方式,采用立轴式小型汽油机和蜗轮蜗杆传动,机架和传动箱体为薄钢板冲压成型,扶手架上下、左右可调,耕深为10.7cm,生产率为0.09hm/h,重量仅为生产率相同的国内其它旋耕机的1/2~1/5。  相似文献   
32.
T. Hodgkin 《Euphytica》1977,26(2):401-408
Summary Brussels sprouts inbred plants, homozygous for the same recessive S-allele, were intercrossed in all combinations and the number of pollen tubes penetrating the stigmas of such crosses measured. The results of five such experiments showed that pollen as well as stigma is significant in determining the number of pollen tubes counted. It was also found that the capacity of a plant's stigmas to permit pollen tube penetration was independent of the capacity of its pollen to penetrate other plants' stigmas. Variation in pollen tube production between pollens of the plants tested was often greater than that between their stigmas.  相似文献   
33.
Summary Investigations of the genetics of self-compatibility and self-incompatibility in dihaploids and diploid derivatives from cv. Gineke revealed the presence of S 1, S2 and S 3 at the S-locus of Gineke and in addition an S 1-allele on a translocation. By means of a complete tester set involving the S-alleles S 1, S2 and S 3 (all from Gineke) and S 4 (from Black 4495) it was demonstrated that some Gineke dihaploids were compatible with all six testers. This indicated a fourth S-allele in Gineke, which differs from those in the tester series and was therefore assigned S 5. Additional evidence was obtained from an analysis of F1's from crosses of two S 5-bearing dihaploids and one of the testers. So the S-genotype of cv. Gineke was identified as S 1S2S3S5/S1, the second S 1 being the S-allele on a translocated fragment.  相似文献   
34.
金顶侧耳不同交配型营养缺陷突变菌株的制备   总被引:1,自引:1,他引:1  
以金顶侧耳的营养缺陷突变菌株为供试菌株,在确认其交配型的基础上,配制杂交株,利用其减数分裂中基因的高频率重组性制备不同交配型的营养缺陷突变菌株。结果表明:除突变型Ade2-、Ade5-、Pdx2-各自获得3种不同交配型的营养缺陷突变菌株外,其他突变型均获得4种不同交配型的营养缺陷突变茵株,共计获得具有不亲和性因子和营养缺陷型双重标记的金顶侧耳菌株(包括供试菌株)133株。  相似文献   
35.
A comparison was made of the effects of abscisic acid (ABA) and the ABA biosynthesis inhibitor, norflurazon on the interaction between soybean leaves and Phytophthora sojae. Inoculation of leaves of cv. Harosoy resulted in a compatible interaction typified by the presence of spreading, water soaked lesions with ill-defined margins while inoculation of cv. Haro 1272 resulted in an incompatible interaction with lesions restricted to the inoculation site. Activity of phenylalanine ammonia lyase (PAL) slowly increased in the compatible interaction but in the incompatible interaction there was a rapid rise in activity within 8h after inoculation. When Haro 1272 plants were treated with ABA the normally incompatible interaction with race 1 was changed to what resembled a compatible interaction and activity of PAL was reduced to control levels. There was no visible effect on the compatible combination. In contrast when plants of cv. Harosoy were treated with norflurazon the normally compatible interaction with race 1 was changed to that which resembled an incompatible interaction and PAL activity increased to high levels rapidly. There was no effect of norflurazon on the incompatible interaction of cv. Haro 1272 with race 1. Stomata on leaves of cv. Harosoy treated with norflurazon closed within 2h of inoculation resembling the response of stomata in normal incompatible interactions but not compatible interactions where stomata remained open. On leaves of cv. Harosoy treated with norflurazon at sites 3 and 20mm from the inoculation point stomata also closed. These results extend and confirm the idea that ABA is a molecule that may regulate the outcome of the interaction between soybeans and P. sojae.  相似文献   
36.
Genetic diversity was studied in a population of 24 isolates of Rosellinia necatrix obtained from Cyperus esculentus and 16 from other hosts by means of mycelial compatibility groups (MCGs) and inter-simple sequence repeat (ISSR) techniques. All isolates obtained from C. esculentus belonged to a unique MCG, irrespective of their geographical origin or year of isolation, and were incompatible with the isolates from other hosts. ISSR analysis gave results which were in agreement with the MCG determination; selected ISSR primers grouped a subset of eight representative isolates from C. esculentus in a unique cluster. The homogeneity found within the population of R. necatrix from C. esculentus in Valencia province could suggest that the pathogen was introduced recently and has spread further via infected tubers inadvertently used as propagating material, as well as by cull tubers swept away by irrigation water.  相似文献   
37.
果树自交不亲和性的遗传与生理机制及其研究   总被引:20,自引:5,他引:20  
在简要介绍植物(包括果树)自交不亲和性与生理控制机制的基础上,着重对梨、苹果、杏等果树自交不亲和性的研究进行了综述,内容包括花柱内花粉管生长特点、花柱S糖蛋白的特性与作用机理以及果树自交不亲和的分子生物学研究,并提出了该领域有待研究的问题。  相似文献   
38.
以自交亲和系WS-199和自交不亲和系WS-85为亲本杂交获得的F_2分离群体为供试材料,采用BSA法结合SNP芯片技术,筛选出与自交不亲和性相关的SNP标记,并将SNP差异位点序列信息与白菜基因组序列进行比对分析,并进一步开发SSR标记,共获得了与自交不亲和性相关的SSR分子标记BrA1-2、BrA1-3和BrA1-14,为分子标记辅助自交不亲和性杂交种生产提供技术支持。  相似文献   
39.
番茄种间杂交不亲和性的研究   总被引:1,自引:0,他引:1  
以栽培种番茄[Lycopersicon esculentum“粤农二号”(E)],野生种秘鲁番茄(L.peruvianum(P)],以及“粤农二号×秘鲁番茄”的F_1(“E×P”F_1)为材料,进行相互间的有性杂交。在“P×E”F_0杂交组合中,E的花粉管与P的花柱部位发生不亲和;“E×P”F_1自交,自身的精卵细胞不亲和;PדE×P”F_1回交,远缘杂种“E×P”F_1的花粉管与P的胚珠不亲和。“E×E”和“P×P”两融交组合,E和P的花粉管在授粉后24小时左右已可看到进入子房,到迭胚珠。  相似文献   
40.
应用野外观测和室内模拟方法,研究了酚在巢湖施口水域的自净规律。结果表明,酚在巢湖湖水中的衰减符合一级反应速率方程C=C0e^-Kt。在有水流稀释的情况下,含酚污水的自净主要充的稀释作用;在无水流稀释的情况下,水体中微生物的生化作用,光化学化作用,底泥的吸附作用和酚的挥发作用地酚的净化起重要作用。  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