全文获取类型
收费全文 | 513篇 |
免费 | 21篇 |
专业分类
林业 | 55篇 |
农学 | 69篇 |
基础科学 | 8篇 |
112篇 | |
综合类 | 33篇 |
农作物 | 27篇 |
水产渔业 | 42篇 |
畜牧兽医 | 125篇 |
园艺 | 27篇 |
植物保护 | 36篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 17篇 |
2019年 | 7篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 17篇 |
2015年 | 18篇 |
2014年 | 23篇 |
2013年 | 46篇 |
2012年 | 29篇 |
2011年 | 31篇 |
2010年 | 23篇 |
2009年 | 22篇 |
2008年 | 26篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 8篇 |
1966年 | 6篇 |
排序方式: 共有534条查询结果,搜索用时 875 毫秒
451.
Twelve profiles representing the principal soils of five major agricultural areas (Al-Kharj, Gassim, Hofuf, Taif and Wadi Dawasir) in Saudi Arabia were described and sampled by horizons. Laboratory analyses were then made of the samples to characterize the profiles more completely. Analyses were also made for certain nutrient elements to get some measure of their levels in the soils.The profiles are tentatively classified in the Entisol and Aridisol orders of the American taxonomy. Five Entisol profiles were considered to be Fluvents and two Psamments. Four Aridisol profiles were considered to be Argids and one an Orthid.All of the profiles are saline and calcareous and most are also sandy. Furthermore, amounts of nutrient elements such as phosphorus, iron and zinc in surface layers are below minimum levels established for similar soils in earlier investigations in other countries. Consequently, the soils are believed to lack sufficient quantities of several elements for optimum plant growth. Successful use of the soils will thus require reductions in salinity, increased levels of nutrient elements, and skillful irrigation to provide adequate moisture. 相似文献
452.
Hydrolysis of ammonium polyphosphate in soils under aerobic and anaerobic conditions 总被引:1,自引:0,他引:1
Summary The hydrolysis of fertilizer-grade solid and liquid ammonium polyphosphate (APP) was studied on an aluvial (Entisol, Typic Ustifluvent), a sodic (Entisol Aquic Ustifluvent), and a laterite (Oxisol, Aquox) soil under aerobic and anaerobic conditions. The hydrolysis rate was the fastest on laterite, intermediate on sodic, and slowest in the alluvial soil. Ammonium polyphosphate hydrolyzed more rapidly under anaerobic than under aerobic conditions. The hydrolysis of liquid ammonium polyphospahte was faster than that of solid ammonium polyphosphate in all soils. The half-life values for the polyforms of P in liquid ammonium polyphosphate ranged from 1.6 to 2.0 days under anaerobic and from 5.2 to 8.7 days under aerobic conditions. The corresponding values for solid ammonium polyphosphate were 3.9 to 9.2 days under anaerobic and 12.5 to 27.0 days under aerobic conditions. 相似文献
453.
Chumki Bhattacharjee Nagenahalli Huchappa Manjunath Doddananjappa Theertha Prasad 《Journal of Crop Science and Biotechnology》2009,12(4):253-260
Proteinase inhibitors play a significant role in plant defense against insect pests and phytopathogens by inhibiting their
proteases. A thermotolerant monomeric trypsin inhibitor with molecular weight ∼18kD was purified from Cocculus hirsutus (ChTI) using trypsin sepharose affinity column. Western blot analysis using ChTI IgY revealed its presence in vegetative
parts and seeds. The second and third instar larvae of H. armigera fed with ChTI (5000TIU/ml) resulted in 84.59 and 58.71% reduction in mean larval weight respectively. An increase in the
larval growth period was observed in ChTI fed larvae at all instars and inhibitor fed larvae could not complete their life
cycle. ChTI caused 74 and 59.53% inhibition of bovine trypsin and Helicoverpa gut proteases respectively. ChTI exhibited strain specificity and inhibited growth and development of plant fungal pathogens.
Bioassay studies on yeast strains indicated that ΔYNK and MNN1 are more sensitive to ChTI. The results suggest that phosphodiester
linkage in cell wall components is likely to be the key determinants for binding of ChTI. Taken together, these studies indicate
that ChTI is a potential candidate for development of transgenic plants against foliar diseases and insect pests. 相似文献
454.
J. Somasundaram R. K. Singh S. N. Prasad B. K. Sethy A. Kumar K. Ramesh B. L. Lakaria 《Soil Use and Management》2011,27(1):124-127
Crop yields in rainfed areas are primarily dependent on the rainfall pattern and stored soil moisture. High smectite clay causes the formation of cracks, which are a striking feature of black Vertisols which are also distinguished by the presence of pot‐holes. Soil water is recharged during the rainy season via these cracks, which also results in pot‐hole formation. This study was undertaken to evaluate the effect of different conservation measures on pot‐holes. Length, width and depth were measured during dry spells after the onset of the monsoon under various field treatments. The results indicate that uncultivated fields have a greater volume of pot‐holes (573 m3/ha) than cultivated ones due to unbroken gentle slopes, which would have caused silt‐laden runoff to travel longer distances to form pot‐holes. The results show that among the cultivated fields, a control plot had the maximum volume of pot‐holes (450 m3/ha), followed by a conservation bench terrace (CBT) (231 m3/ha), residue incorporated (RI) fields (142 m3/ha) and contour furrow areas (CF) (119 m3/ha). The CBT field treatment had a higher volume of pot‐holes despite a high percentage of micro‐aggregates and high total porosity. 相似文献
455.
D. Kolbehdari Z. Wang J.R. Grant B. Murdoch A. Prasad Z. Xiu E. Marques P. Stothard & S.S. Moore 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2009,126(3):216-227
The detection and mapping of genetic markers linked to quantitative trait loci (QTL) can be utilized to enhance genetic improvement of livestock populations. With the completion of the bovine genome sequence assembly, single nucleotide polymorphisms (SNP) assays spanning the whole bovine genome and research work on large scale identification, validation and analysis of genotypic variation in cattle has become possible. The objective of the present study was to perform a whole genome scan to identify and map QTL affecting milk production traits and somatic cell scores using linkage disequilibrium (LD) regression and 1536 SNP markers. Three and 18 SNP were found to be associated with only milk yield (MY) at a genome and chromosome wise significance (p < 0.05) level respectively. Among the 21 significant SNP, 16 were in a region reported to have QTL for MY in other dairy cattle populations and while the rest five were new QTL finding. Four SNP out of 21 are significant for the milk production traits (MY, fat yield, protein yield (PY), and milk contents) in the present study. Six and nine SNP were associated with PY at a genome and chromosome wise significant (p < 0.05) level respectively. Three and 17 SNP were found to be associated with FY at a genome and chromosome wise significant (p < 0.05) level. Five and seven SNP were mapped with somatic cell score at a genome and chromosome wise significant (p < 0.05) level respectively. The results of this study have revealed QTL for MY, PY, protein percentage, FY, fat percentage, somatic cell score and persistency of milk in the Canadian dairy cattle population. The chromosome regions identified in this study should be further investigated to potentially identify the causative mutations underlying the QTL. 相似文献
456.
Kashyap Sarvesh Pratap Kumari Nishi Mishra Pallavi Moharana Durga Prasad Aamir Mohd 《Genetic Resources and Crop Evolution》2021,68(6):2207-2233
Genetic Resources and Crop Evolution - Crop breeding for abiotic stress tolerance entails introgression of stress tolerant genes into the cultivated types. With the augmentation in salt tolerance,... 相似文献
457.
458.
S. N. Sharma R. Prasad M. K. Dwivedi Sandeep Kumar M. R. Davari Moola Ram 《Archives of Agronomy and Soil Science》2013,59(4):429-438
A field study was carried out at the Indian Agricultural Research Institute, New Delhi, India, for three crop years (2000–2001 to 2003–2004) to find out the effect of cropping systems on the production and chemical and biological properties of soil. Rice-potato-mungbean cropping system gave 59–89% higher productivity, 30–46% higher protein yield, 18–38% higher energy output and resulted in 7–16% higher available P, 60% higher fungi population, 15% higher actinomycetes population, 14% higher microbial biomass and 3% higher CO2 evolution in soil than rice-wheat cropping system. Rice-rapeseed-mungbean cropping system also gave 12–15% higher productivity, 19–26% higher protein yield and resulted in 11–18% higher available P, 65% higher fungi population, 22% higher actinomycetes population, 12% higher microbial biomass and 2% higher CO2 evolution in soil than rice-wheat cropping system. However, the rice-potato-mungbean cropping system was significantly superior to the rice-rapeseed-mungbean cropping system in productivity, protein yield and energy output and thus recommended as in alternative to rice-wheat cropping system. 相似文献
459.
Krishna Prasad Woli Toshiyuki Nagumo Ryusuke Hatano 《Soil Science and Plant Nutrition》2013,59(6):883-887
Abstract This study was conducted to evaluate the magnitude of nitrogen (N) pollution in stream water associated with intensive livestock farming practices. An extensive water sampling was carried out from stream tributaries, open channels, drainages, and seepages during the snow-melting season in 2001. Total nitrogen (TN) concentration was determined and water flow was measured. The lowest concentration of TN in the headwater of tributary ‘A’ was as low as 0.39 mg N L?1 (0.03 g s?1 of N load), and the concentration reached a value of 5 mg N L?1 in the outlet of the stream, which resulted in a N load of 1.37 g s?1. The increase in the N load (1.34 g s?1) was mainly due to drainage from a constructed wetland for livestock wastes, other drainages, and seepages from around the livestock sheds. The maximum concentration of TN in the drainage and seepage water from the constructed wetland was very high, 63 mg N L?1, which resulted in a N load of 0.53 g s?1 into the open channel that reached tributary ‘A.’ About 40% of the increased N load in the main tributary in the intensive livestock farming area was occupied by a single constructed wetland confirming that the drainage from this facility acted as the point source of pollution in the area. 相似文献
460.
Sri Niwas Sharma Yashbir Singh Shivay Rajendra Prasad Manoj Kumar Dwivedi Mohammadreza Davari Sandeep Kumar 《Journal of plant nutrition》2013,36(7):998-1015
Field experiments were conducted at the Indian Agricultural Research Institute, New Delhi, India for three years from 2001–2002 to 2003–2004 to study the relative efficiency of diammonium phosphate (DAP) and mussoorie rock phosphate (MRP) in a rice-potato-mungbean cropping system. Phosphorus application significantly increased productivity, protein yield and energy output of rice-potato-mungbean cropping system and resulted in an increase in 0.5 M sodium bicarbonate (NaHCO3) extractable phosphorus (P) content in soil. The MRP at 35 kg P ha?1 was at par with 17.5 kg P ha?1 as DAP in terms of productivity, protein yield, and energy output but significantly superior in terms of PSB population in soil. Phosphorus balance (application – crop removal) was generally more positive for MRP than DAP and the highest with an application of 52.5 kg P ha?1 as MRP. Present study indicates that P requirement of a rice-potato-mungbean cropping system can be met with 76–79% higher dose of MRP as compared to DAP. 相似文献