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   69篇
  免费   1篇
林业   8篇
农学   13篇
基础科学   2篇
  18篇
综合类   1篇
农作物   8篇
水产渔业   7篇
畜牧兽医   4篇
园艺   3篇
植物保护   6篇
  2023年   1篇
  2022年   3篇
  2021年   1篇
  2020年   3篇
  2019年   1篇
  2018年   3篇
  2017年   5篇
  2016年   1篇
  2014年   2篇
  2013年   9篇
  2012年   5篇
  2011年   6篇
  2010年   2篇
  2009年   5篇
  2008年   2篇
  2007年   2篇
  2006年   2篇
  2005年   4篇
  2004年   1篇
  2002年   1篇
  1997年   1篇
  1994年   2篇
  1991年   1篇
  1989年   1篇
  1988年   2篇
  1984年   1篇
  1983年   1篇
  1975年   1篇
  1974年   1篇
排序方式: 共有70条查询结果,搜索用时 171 毫秒
1.
Vanilla is a large genus of about 110 species in the orchid family (Orchidaceae), including the species Vanilla planifolia from which commercial vanilla flavoring is derived. Since most species of vanilla are considered rare and endangered there is an urgent need to conserve them through genetic analysis and propagation/conservation studies on this crop.The present study investigated the genetic diversity among nine leafy- and leaf-less Vanilla species employing 30 decamer RAPD primers and 10 ISSR primers. The species under study were diverse and displayed a range of variability (0–66% and 0–81% for RAPD and ISSR, respectively). A total of 154 RAPD polymorphic markers (83.24%, h = 0.378) and 93 ISSR polymorphic markers (86.11%, h = 0.363) were used to generate a genetic similarity matrix followed by the cluster analysis. Specific groupings were revealed by each cluster analysis with slight variation between two different markers. Among the nine species studied, V. planifolia, Vanilla aphylla and Vanilla tahitensis revealed very low level of variation within their collections, thus indicating a narrow genetic base. The large genetic distance of Vanilla andamanica from other species suggests its different origin. A close genetic affinity was observed between the pairs V. planifolia, V. tahitensis and Vanilla albida, V. aphylla. These are the first comparative results for RAPD and ISSR reporting inter-relationship among nine cultivated, wild and hybrid Vanilla species.  相似文献   
2.
A detailed study has been conducted to evaluate the residues of endosulfan and its principal metabolite (alpha-endosulfan, beta-endosulfan and endosulfan sulfate) which may have accumulated in environmental samples due to regular aerial spray application of endosulfan on cashew leaf plantation for a period of 20 years. Three months after the last spray of endosulfan 350 g litre-1 EC at 300 ml acre-1 (equivalent to 105 g AI acre-1 = 42.5 g ha-1), a total of 93 samples of cow milk, fish, water, soil and dried cashew leaf were collected from a village in Kasargode District, Kerala, India, where endosulfan contamination was likely to have occurred. All the samples were analyzed for total residues of endosulfan (comprising alpha- and beta-endosulfan), endosulfan sulfate and also the potential hydrolysis product endosulfan diol, using gas chromatography with electron capture detection. The minimum detection limits of total endosulfan was 0.001 microgram g-1. Analysis of soil samples showed the deposition of total endosulfan residues in the range < 0.001-0.010 microgram g-1, and dried leaf samples showed residues of endosulfan in the range < 0.001-3.43 micrograms g-1 dry weight. In cow milk, fish and water, endosulfan residues could not be detected above the minimum detection limit. Endosulfan diol was not observed in any sample. The data obtained was confirmed by GC-MS-EI using selective ion monitoring (SIM) mode.  相似文献   
3.
Forty peptides were synthesized corresponding to hydrophilic clusters of amino acids within the sequences of foot-and-mouth disease virus (FMDV) nonstructural proteins (NSP). Six peptides were studied in more detail and the most promising, a 2B peptide, was evaluated in enzyme-linked immunosorbent assay (ELISA) using sera from naive, vaccinated, and vaccinated-and-challenged cattle as well as bovine sera from field outbreaks. The performance of the new NSP peptide ELISA was compared to that of 4 commercial NSP ELISA kits. Antibody to 2B was detectable from the end of the first week to the second week after infection in most of the nonvaccinated animals and by the second to third week in vaccinated-and-challenged animals. The sensitivity of the 2B peptide ELISA was comparable to the 3ABC Ceditest (Ceditest FMDV-NS, Cedi Diagnostics B.V.; Chung et al., 2002). With some modification and further validation, this 2B test could be useful as a screening or conformational NSP test in postvaccination surveillance for FMD.  相似文献   
4.
Bruchidius andrewesi Pic. has been recorded as a serious pest of pods and seeds of Acacia tortilis in the Thar desert of India. Pest infestation on developing pods and its relationship with morphological traits is reported. Pod infestation varied from 5 to 19% with 5–29% infestation of seeds. Infestation of pods is directly related to infestation of seed (r = 0.72**), and both pod and seed infestation are also directly correlated with loss in seed biomass (r = 0.79** and R = 0.88**). The infestation of pods starts in November and increases steady until harvest. Seeds kept in the laboratory for further studies were found to be 100% infested with B. andrewesi, as the insect multiplied faster under these conditions. The heavy infestation is damaging not only to A. tortilis but also to other leguminous trees of the desert. Bruchidius andrewesi has also been found on pods and seeds of Prosopis cineraria, an important indigenous tree of the region.  相似文献   
5.
Summary Two RAPD markers linked to gene for resistance (assayed as pustule number cm−2 leaf area) to rust [Uromyces fabae (Pers.) de Bary] in pea (Pisum sativum L.) were identified using a mapping population of 31 BC1F1 [HUVP 1 (HUVP 1 × FC 1] plants, FC 1 being the resistant parent. The analysis of genetics of rust resistance was based on the parents, F1, F2, BC1F1 and BC1F2 generations. Rust resistance in pea is of non-hypersensitive type; it appeared to be governed by a single partially dominant gene for which symbol Ruf is proposed. Further, this trait seems to be affected by some polygenes in addition to the proposed oligogene Ruf. A total of 614 decamer primers were used to survey the parental polymorphism with regard to DNA amplification by polymerase chain reaction. The primers that amplified polymorphic bands present in the resistant parent (FC 1) were used for bulked segregant analysis. Those markers that amplified consistently and differentially in the resistant and susceptible bulks were separately tested with the 31 BC1F1 individuals. Two RAPD makers, viz., SC10-82360 (primer, GCCGTGAAGT), and SCRI-711000 (primer, GTGGCGTAGT), flanking the rust resistance gene (Ruf) with a distance of 10.8 cM (0.097 rF and LOD of 5.05) and 24.5 cM (0.194 rF and a LOD of 2.72), respectively, were identified. These RAPD markers were not close enough to Ruf to allow a dependable maker-assisted selection for rust resistance. However, if the two makers flanking Ruf were used together, the effectiveness of MAS would be improved considerably.  相似文献   
6.
Penultimate and last instar larvae of the common citrus swallowtail butterfly, Papilio demoleus L. (Papilionidae: Lepidoptera), were treated with different doses of a novel juvenoid, diofenolan. Several deformities were observed as a result of topical administration of diofenolan which include delay in larval–larval and larval–pupal ecdysis, ecdysial failure, mortality, severe reduction in pupation, deformed pupae and complete inhibition of adult emergence. The juvenoid diofenolan severely hampers the normal growth, development and metamorphosis of P. demoleus and can be incorporated into integrated pest management programs for successful control of this important pest of citrus all over the world.  相似文献   
7.
A field study was conducted to determine if differences in grain filling rate and duration existed in two early cultivars of rice. There is no cultivar difference in duration of grain filling and grain matured in about 30 days from anthesis in both the cultivars. The effective grain filling period in rice is only 10 days between 3rd and 13th day from anthesis. There is significant difference in grain filling rate and is positively related to grain weight. Grain filling rate is more important than duration of filling for achieving higher grain size and thus yield in rice.  相似文献   
8.
Four microsatellite markers and a mitochondrial DNA (mtDNA) fragment were used to investigate two possible explanations for a reported decline in productivity of genetically improved farmed tilapia (GIFT) in Fiji: (i) a decline in genetic diversity (GD) and (ii) genetic introgression from feral tilapia populations. Genetic diversity was estimated using θ and allelic richness, while Bayesian clustering was used to assign individuals to genetic groups (K=2 or 3) to test for introgression. Differentiation among groups was estimated using FST analysis. Results indicate that genetic diversity had declined compared with a GIFT reference stock from WorldFish Centre, while there was little evidence for introgression from feral tilapia populations. Loss of genetic diversity most probably resulted from practices that have not actively managed genetic resources in the hatchery. While GIFT is considered to be an improved line of Nile tilapia (Oreochromis niloticus), mtDNA analysis here revealed haplotypes assigned previously to three discrete Oreochromis species (O. niloticus, Oreochromis mossambicus and Oreochromis aureus) in both the Fijian strain and the WorldFish Centre strain. Possible sources for the three divergent lineages are discussed. Results have implications for the management and future expansion of the tilapia culture industry in Fiji as well as in other Pacific island nations.  相似文献   
9.
A 60 days feeding trial was conducted to illustrate the effect of graded levels of protein on the growth and metabolic enzymes of grey mullet (Mugil cephalus L.) fingerlings reared in inland saline water (ISW). Six isoenergetic (16 MJ/kg) and isolipidic (60 g/kg) diets containing 240, 260, 280, 300, 320 and 340 g crude protein (CP)/kg diet were formulated and fed to triplicate. Weight gain %, specific growth rate, protein utilizing efficiency, feed efficiency and RNA:DNA ratio were significantly higher (p < .05) in 320 and 300 g CP/kg diets. Fish fed with 240 g CP/kg diet showed significantly higher (p < .05) feed intake, whole‐body lipid content, hepatosomatic index value and liver glycogen content. Transaminase enzymes and malate dehydrogenase activities were elevated in fish fed 340 g CP/kg diet. Protease activity increased with increasing dietary CP level, but amylase activities showed an inverse relationship. No significant (p > .05) variations were observed for lactate dehydrogenase, oxidative stress enzymes, blood parameters and serum osmolality among all the treatment groups, but red blood cell count increases with increasing dietary CP levels. Based on the results, feeding dietary protein level of 300 g CP/kg is economically viable for rearing of grey mullet in ISW.  相似文献   
10.
Small ubiquitin-like modifier (SUMO)-conjugating enzymes are involved in post-translational regulatory processes in eukaryotes, including the conjugation of SUMO peptides to protein substrate (SUMOylation). SUMOylation plays an important role in improving plant tolerance to abiotic stress such as salt, drought, heat and cold. Herein, we reported the isolation of OsSCE1 (LOC_Os10g39120) gene encoding a SUMO-conjugating enzyme from rice (Oryza sativa cv. Nipponbare) and its functional validation in response to drought stress. The E2 enzyme, OsSCE1, is one of three key enzymes involved in the conjugation of SUMO to its target proteins. Activated SUMO is transferred to the cysteine of an E2 enzyme and then to the target lysine residue of the substrate, with or without the help of an E3 SUMO ligase. Expression of OsSCE1 was strongly induced by polyethylene glycol 6000 (PEG6000) treatment, which suggested OsSCE1 may be involved in the drought stress response. Overexpression of OsSCE1 (OsSCE1-OX) in Nipponbare reduced the tolerance to drought stress. Conversely, the drought tolerance was slightly improved by the knockdown of OsSCE1 (OsSCE1-KD). These results were further supported by measurement of proline content in OsSCE1-OX and OsSCE1-KD transgenic lines under induced drought stress, which showed OsSCE1-KD transgenic lines accumulated higher proline content than the wild type, whereas OsSCE1-OX line had lower proline content than the wild type. These findings suggested OsSCE1 may play a role as a negative regulator in response to drought stress in rice.  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