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   1498篇
  免费   73篇
  国内免费   1篇
林业   140篇
农学   220篇
基础科学   23篇
  302篇
综合类   47篇
农作物   88篇
水产渔业   46篇
畜牧兽医   511篇
园艺   66篇
植物保护   129篇
  2023年   10篇
  2022年   22篇
  2021年   32篇
  2020年   31篇
  2019年   24篇
  2018年   67篇
  2017年   56篇
  2016年   68篇
  2015年   37篇
  2014年   40篇
  2013年   119篇
  2012年   56篇
  2011年   77篇
  2010年   56篇
  2009年   45篇
  2008年   67篇
  2007年   54篇
  2006年   45篇
  2005年   40篇
  2004年   34篇
  2003年   39篇
  2002年   41篇
  2001年   28篇
  2000年   26篇
  1999年   29篇
  1998年   13篇
  1997年   9篇
  1996年   15篇
  1995年   11篇
  1994年   10篇
  1993年   11篇
  1992年   18篇
  1991年   20篇
  1990年   30篇
  1989年   21篇
  1988年   14篇
  1987年   20篇
  1986年   17篇
  1985年   17篇
  1984年   11篇
  1983年   12篇
  1982年   14篇
  1981年   17篇
  1980年   14篇
  1979年   21篇
  1978年   15篇
  1977年   11篇
  1970年   8篇
  1969年   14篇
  1968年   12篇
排序方式: 共有1572条查询结果,搜索用时 31 毫秒
101.
The Indian gene centre possesses a rich legume biodiversity––1,152 species comprising cultivated, underutilized edible and forage legumes. Majority of the underutilized food legumes are widely distributed as wild species in various agro-ecological regions of peninsular India. Indian legume species (62%) contribute to the food and health security of ethnic communities. A total of 66,546 accessions of legume gene resources including underutilized species are conserved in the National Gene Bank. Collection, characterization and conservation efforts regarding the diversity of these beans are described. The importance of genetic variation in legumes and their wild relatives as a source of desirable resistance to pests and diseases in a changing climate scenario is discussed. Information on legumes used in Indian and modern systems of medicine and ethno-botany as well as the scope for bio-prospecting are presented. Advanced biotechnological applications in legume research for sustainable utilization of these resources are highlighted. An integrated gene resource management strategy to combat malnutrition, identify gene resources for legume improvement and enhance their value as traditional food and medicine is described.  相似文献   
102.
Acorus calamus is an important medicinal plant which has been used in Indian traditional medicine since time immemorial. Various bioactive molecules, viz., acorin, α- and β-asarone, asaryldehyde, caryophylene, isoasarone, methylisoeugenol, and safrol have been isolated from this plant. However, the use of this plant for medicinal purpose has been recently banned due to the high toxic property of β-asarone. The triploid Acorus calamus is reported to be low in β-asarone content and thus found to be the ideal raw material for medicinal use. The present investigation represents our finding for successful in vitro clonal propagation of the elite triploid accessions of Acorus calamus for mass propagation. In the dual-phase culture system consisting of agar-solidified Murashige and Skoog medium overlaid by liquid fraction of the same medium, maximum multiple shoot induction was favored by supplementation of α-naphthaleneacetic acid (0.5 mg L−1) and 6-benzylaminopurine (2.0 mg L−1). In vitro rooting of the microshoots was maximum in the medium supplemented with indolebutyric acid at 2.0 mg L−1. The well-rooted microshoots could be successfully hardened and transplanted in the field. This result can be reproduced and is a viable protocol for successful clonal propagation of the seedless triploid Acorus calamus for conservation and sustainable development.  相似文献   
103.
Actinomycin D and thioacetamide induced ovalbumin synthesis and increased serum progesterone concentrations in immature chicks. The increase in progesterone induced by the carcinogens actinomycin D and thioacetamide may account for the induction of ovalbumin synthesis.  相似文献   
104.
An increase in the rate of mutation has been found in Drosophila melanogaster reared on a basic medium that was irradiated with a sterilizing dose (150,000 rads) of cobalt-60 gamma rays. In Muller-5 tests, sex-linked recessive lethals occurred only in the F(2) progenies of the male test flies obtained from breeding the parent flies on irradiated medium, while visible changes occurred in experimental cultures from both the control and irradiated media. The frequency of sex-linked recessive lethals was 0.35, 0.55, and 0.8 percent in three independent experiments. Visible changes were two to six times more frequent in the irradiated series than in the controls.  相似文献   
105.
Natural adhesives in the feet of different arthropods and vertebrates show strong adhesion as well as excellent reusability. Whereas the hierarchical structures on the surface are known to have a substantial effect on adhesion, the role of subsurface structures such as the network of microchannels has not been studied. Inspired by these bioadhesives, we generated elastomeric layers with embedded air- or oil-filled microchannels. These adhesives showed remarkable enhancement of adhesion ( approximately 30 times), which results from the crack-arresting properties of the microchannels, together with the surface stresses caused by the capillary force. The importance of the thickness of the adhesive layer, channel diameter, interchannel spacing, and vertical position within the adhesive has been examined for developing an optimal design of this microfluidic adhesive.  相似文献   
106.
Rapid flow cytometric analysis of the cell cycle in intact plant tissues   总被引:2,自引:0,他引:2  
Mechanical chopping of plant tissues in the presence of mithramycin released intact nuclei representative of the cells within the tissues. The amount of nuclear DNA in the homogenates of monocotyledonous and dicotyledonous plants was accurately and rapidly determined by flow microfluorometry, and the distribution of nuclei involved in the cell cycle was charted for tissues selected from different physical locations or developmental stages.  相似文献   
107.
A fundamental aspect of visuomotor behavior is deciding where to look or move next. Under certain conditions, the brain constructs an internal representation of stimulus location on the basis of previous knowledge and uses it to move the eyes or to make other movements. Neuronal responses in primary visual cortex were modulated when such an internal representation was acquired: Responses to a stimulus were affected progressively by sequential presentation of the stimulus at one location but not when the location was varied randomly. Responses of individual neurons were spatially tuned for gaze direction and tracked the Bayesian probability of stimulus appearance. We propose that the representation arises in a distributed cortical network and is associated with systematic changes in response selectivity and dynamics at the earliest stages of cortical visual processing.  相似文献   
108.
109.
The bacterium Deinococcus radiodurans survives ionizing irradiation and other DNA-damaging assaults at doses that are lethal to all other organisms. How D. radiodurans accurately reconstructs its genome from hundreds of radiation-generated fragments in the absence of an intact template is unknown. Here we show that the D. radiodurans genome assumes an unusual toroidal morphology that may contribute to its radioresistance. We propose that, because of restricted diffusion within the tightly packed and laterally ordered DNA toroids, radiation-generated free DNA ends are held together, which may facilitate template-independent yet error-free joining of DNA breaks.  相似文献   
110.
The objective of this study is to investigate the response of screening, and selection of novel indigenous AM fungal species and Azotobacter chroococcum strains for inoculating apple under different soil disinfestations and moisture conservation mulch practices for sustainable nursery management. Two local AM fungal species namely, Glomus fasciculatum (Thaxter sensu Gerdemann) and Glomus mosseae (Nicol. & Gerd.), and two strains of A. chroococcum viz., A. chroococcum strain-I (AZ1) and A. chroococcum strain-II (AZ2) were inoculated at nursery stage under soil solarization, chemical disinfestation and natural soil conditions at four different mulch materials namely, black plastic mulch (BPM), and organic mulches, i.e. grass mulch (GM); cover crops (CC); green manuring + clean cultivation (Gm + Cc). The comparative performance of the seedlings on the impact of local AM species and A. chroococcum strains on growth characteristics, microbial population, root colonization and leaf nutrient status was evaluated. The inoculation of seedlings to G. fasciculatum and AZ1 increased all growth characteristics (plant height, stem diameter, leaf area and total root length), microbial consortium of the rhizosphere soil and leaf N, P, K and Zn content in all those plots where soil solarization and black plastic mulching was used followed by chemical disinfestations and natural soil conditions at all other mulch types used. These findings suggested that the soil inoculation of G. fasciculatum and AZ1 strain to seeds and/or the saplings under soil solarization with black plastic mulch attained a desirable plant height and become ready for grafting which however saved a period of 1 year for nursery management compared to traditional nursery raising practice, and thus, it may be a viable and feasible approach to maintain soil productivity under nutrient limited soils for sustainable apple nursery production under temperate rain-fed conditions.  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