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   209篇
  免费   4篇
  国内免费   4篇
林业   17篇
农学   23篇
基础科学   3篇
  53篇
综合类   16篇
农作物   15篇
水产渔业   15篇
畜牧兽医   47篇
园艺   7篇
植物保护   21篇
  2023年   3篇
  2022年   8篇
  2021年   15篇
  2020年   6篇
  2019年   8篇
  2018年   5篇
  2017年   5篇
  2016年   7篇
  2015年   8篇
  2014年   6篇
  2013年   26篇
  2012年   13篇
  2011年   8篇
  2010年   6篇
  2009年   11篇
  2008年   9篇
  2007年   5篇
  2006年   4篇
  2005年   4篇
  2004年   2篇
  2003年   3篇
  2002年   8篇
  2001年   1篇
  2000年   2篇
  1999年   3篇
  1998年   4篇
  1997年   4篇
  1996年   3篇
  1994年   2篇
  1992年   2篇
  1991年   1篇
  1989年   2篇
  1986年   1篇
  1985年   2篇
  1984年   3篇
  1983年   4篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1977年   2篇
  1976年   1篇
  1974年   1篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1967年   1篇
  1966年   2篇
排序方式: 共有217条查询结果,搜索用时 15 毫秒
171.
River channel shifting in the deltaic regime is an unabated occurrence. Channel shifting has become one of the concerns as it influences land use/land cover along the riverbank in various ways. For the management of the river, it is indispensable to study the pattern of river course change both in qualitative and quantitative methods. This study is an attempt to understand the pattern of shifting and to quantify erosion and deposition of the river Ganga at upstream and downstream of Farakka Barrage during 1794–2017. The study has been carried out by using various historical maps, aerial photographs, satellite imagery, and remote sensing and GIS technique to understand the dynamic of the river. Over 223 years period shifting of the river accentuates the remarkable oscillation of the river. Perimeter of the river is determined to understand the area covered by the river course in the study area. To evaluate the meandering of the river sinuosity of the river has been computed in this study. The amount of erosion and deposition was calculated in this study by using ArcGIS 10.6. The study found a higher amount of erosion at the east bank where Manikchak, Kaliachak II and Kaliachak III blocks are situated between 1965 and 2017. At the west bank of the river, especially the Rajmahal block, the occurrence of deposition was remarkable during the same period.  相似文献   
172.
173.
I. S. A. Tahir    N. Nakata    A. M. Ali    H. M. Mustafa    A. S. I. Saad    K. Takata    N. Ishikawa    O. S. Abdalla 《Plant Breeding》2006,125(4):323-330
High temperature influences both grain yield and end‐use quality of wheat. The objectives of this study were to evaluate the performance of selected wheat genotypes under heat stress and to examine the effects of high temperatures during grain filling on grain yield and end‐use quality parameters. Fifteen bread wheat genotypes in 2000/2001 and 18 genotypes in 2002/2003 were evaluated under the optimum and late‐sowing conditions of the irrigated hot environment of the Gezira Research Farm, Wad Medani, Sudan. The genotypes comprised released varieties and elite lines from the Sudanese wheat improvement programme. Data collected included grain yield, grain weight and grain end‐use quality including protein content, protein composition, SDS sedimentation values (SDSS) and gluten strength as determined by mixograph analyses. High temperatures significantly decreased grain yield by decreasing grain weight. Although genotypes exhibited variation in magnitude of response, results indicated that high temperature during grain filling increased both soluble and insoluble protein contents, SDSS, mixograph peak height (MPH) and the descending slope at 2 min past peak (MDS). In contrast, mixograph peak time (MPT) and the curve width at 2 min past peak (MCW) were significantly decreased. Flour protein correlated positively with SDSS, MPH and MDS and negatively with MCW. MPT correlated negatively with MDS and positively with MCW. Results indicate that high temperature increased both soluble and insoluble protein contents, SDSS and MPH, and hence the gluten strength, but decreased flour mixing time and tolerance and hence the dough elasticity. Variation observed among genotypes suggests that grain end‐use quality could be improved under high temperature conditions utilizing the available variability; however, it might require evaluation under various growing conditions.  相似文献   
174.
Thirty progenies of mungbean were produced by crossing 10 true-breeding genotypes with three testers (NM 92, 6601, and their F1) in a Triple Test cross (TTC) fashion and evaluated with parents in the kharif (July-October) and spring/summer (March-June) seasons. The data on parents and F1s were analysed for pod clusters on main stem, pod clusters on branches, node of the first peduncle, nodes on main stem and average internode length to detect epistasis and estimate additive and dominance components of genetic variation. Epistasis was observed for node of the first peduncle and nodes on main stem in the kharif season. Partitioning of total epistasis revealed that both additive × additive (i type), and additive × dominance, and dominance × dominance (j and l types) interactions were significant with prevalent influence of i type interactions on these traits. Both additive and dominance components of genetic variation were significant for all those traits not significantly influenced by epistasis in either or both seasons. The additive component was predominant for pod clusters on main stem, pod clusters on branches and average internode length in the kharif season, and for the node of the first peduncle and nodes on main stem in spring/summer season whereas dominance component was important for pod clusters on main stem, pod clusters on branches, and average internode length in spring/summer season. These results suggested that particular generation of segregating population and specific breeding method for selection might be adopted in each season for the improvement of these traits in mungbean. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
175.
Summary For breeding early heading wheat cultivars with resistance to frost damage which are well adapted to dry areas of West Asia and North Africa, the relationships between winter hardiness, ear primordia development and heading traits, i.e. veernalization requirement, photoperiodic response and narrow-sense earliness, were assessed using a total of 30 genotypes of wheat (Triticum aestivum L.) grown in an experiment in Syria. The results of artificial freezing tests indicated that cultivars with good winter hardiness were to be found only in the winter wheat cultivars which required 50 or more days of vernalization treatment. These winter wheat cultivars did not initiate internode elongation without vernalization even at 95 days after planting. Thus their ear primordia were still underground and were protected from frost injury at this stage. Photoperiodic response and narrow-sense earliness were not associated with winter hardiness and earliness of internode elongation, but were related to the number of days to heading after planting. This indicated the possibility for breeding early heading cultivars with winter hardiness and tiller frost avoidance by combining high vernalization requirement, short narrow-sense earliness and neutral response to photoperiod.  相似文献   
176.
The conjunctive use of a compost tea (CT) and an inorganic fertiliser (NPK) on the growth, yield and terpenoid content of Centella asiatica (L.) urban was evaluated. CT and NPK applied at half the recommended concentration resulted in the significant enhancement of vegetative growth, yield and antioxidant content. The synergistic effect of CT50 and NPK50 was highly pronounced on the bioactive components Asiatic acid, madecassoside and asiaticoside. The distribution of the total antioxidants was highest in roots (80%), followed by leaves (66%) and petioles (54%). There was a strong positive correlation (r = 0.990) between fertility and total antioxidant content, suggesting an enhanced synthesis of bioactive components resulting from the treatment. This response by C. asiatica to the integrated experimental treatment suggests a viable option for the commercial cultivation of the herb. Augmenting the vegetative biomass production and bioactive components will increase the availability of this medicinal herb for the treatment of various human ailments.  相似文献   
177.
Gesunde Pflanzen - Application of nanoparticles (NPs) in the management of plant diseases may reduce the use of pesticides and enhance food security. In this study, the effects of TiO2 NPs in 100...  相似文献   
178.
The aim of this study was to evaluate the nutritional and feeding value of peanut hay (Arachis hypogaea L.) produced under tropical environment as an alternate forage resource for sheep. Peanut hay was appreciably high in crude protein [CP; 105 g/kg dry matter (DM)] and lower in neutral detergent fiber (NDF; 466 g/kg DM). Moreover, peanut hay was rich in Ca (12 g/kg DM) and P (1.7 g/kg DM). A feeding trial was conducted to investigate the effect of substituting wheat straw with peanut hay on nutrient intake, digestibility, and N utilization. Four adult Ramghani (Kaghani × Rambouillet) wethers (60?±?2.5 kg body weight) were randomly assigned to the four dietary treatments according to a 4?×?4 Latin square design. The four rations were formulated on isonitrogenous and isocaloric bases and differed in the proportion (in grams per kilogram DM) of wheat straw/peanut hay, i.e., 700:0, 460:240, 240:460, and 0:700. The replacement of wheat straw with peanut hay increased the intakes of DM (P?<?0.001), NDF (P?<?0.01), and N (P?<?0.001). Moreover, apparent in vivo digestibility of DM, NDF, and CP increased (P?<?0.001) with the increasing proportion of peanut hay in the ration. Nitrogen retention in the body increased (P?<?0.01; 3.2 to 8.1 g/day) with the replacement of wheat straw with peanut hay. These findings showed that substitution of wheat straw with peanut hay can improve DM and nutrients intake, digestibility, and N retention in sheep.  相似文献   
179.
The aim of this study was to standardize the feeding regimen and the body condition score (BCS) for maximum superovulatory responses in indigenous zebu cows. Ten regularly cycling 5–8‐year‐old dry cows, weighing 176–260 kg with BCS 2.5–4.5 were divided into two equal groups at random. The groups were maintained on either a good‐nutrition or a high‐nutrition diet. The feedstuffs were analysed by proximate feed analysis and the metabolizable energy content was estimated. After 3 months feeding, individual cows were injected (i.m) with 1500 IU pregnant mare's serum gonadotrophin (PMSG) at day 10 or day 11 of the oestrous cycle (day of oestrus = day 0). Alfaprostol (6 mg) was injected (i.m) 48 h after the injection of PMSG to induce oestrus. At day 6 or day 7 (day of insemination = day 1), the contents of individual uterine horns were flushed with 150–200 ml of phosphate‐buffered saline + 0.2% bovine serum albumin using a two‐way Foley catheter. The embryos were identified, evaluated and graded as excellent, good, fair or poor under a stereomicroscope. For the good‐ and high‐nutrition diets, the daily intake of green grass, straw, concentrate, dry matter, crude protein and estimated metabolizable energy by individual cows were 5 and 6 kg, 3 and 3 kg, 1.5 and 3.5 kg, 4.87 and 6.82 kg, 0.39 and 0.74 kg, and 39.60 and 59.12 MJ, respectively. The protein content was 8 and 11% in the good‐ and high‐nutrition diets, respectively. The two groups of cows on different nutritional diets differed significantly with regard to body weight, body condition score and number of palpated corpora lutea (p < 0.01). For cows on the good‐nutrition diet, the median number of recovered embryos and transferable quality embryos were three and two, respectively. The recovery rate of embryos was 79.30% of palpated corpora lutea. Cows on the high‐nutrition diet did not yield any embryos. The indigenous zebu cows fed on the good‐nutrition diet with BCS 2.5–3 were considered suitable for the induction of superovulation, the cows on the high‐nutrition diet with BCS 4–4.5 were unsatisfactory and were more prone to cyst formation in the ovaries.  相似文献   
180.
Bacteria containing ACC-deaminase in the vicinity of roots may influence plant growth by modifying root architecture through their potential to regulate ethylene synthesis in plant roots. Approximately 138 isolates capable of utilizing ACC as the sole source of N were isolated from the rhizosphere soil of chickpea (Cicer arietinum L.) plants. Under axenic conditions, some rhizobacterial isolates were highly effective in increasing root length (up to 2.08 fold), number (up to 3.7 fold) and length (up to 3.9 fold) of lateral roots, and root biomass (up to 83%) of chickpea as compared to uninoculated control. Serratia proteamaculans strain J119 was found to be the most effective plant growth promoting rhizobacterium (PGPR) in improving root and shoot growth, nodulation and grain yield of chickpea as compared to respective controls in growth pouches, pot and field trials. A highly significant direct correlation (r = 0.99) was observed between number of lateral roots under axenic conditions (jar trial) and number of nodules per plant in pot and field trials. Interestingly, S. proteamaculans J119 also exhibited highest ACC-deaminase activity in addition to root colonization compared to other tested strains. The results of this study demonstrated that changes in root growth and architecture (particularly lateral roots) as a result of inoculation with PGPR containing ACC-deaminase are crucial for improving growth, yield and nodulation of chickpea under field 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