全文获取类型
收费全文 | 561篇 |
免费 | 39篇 |
国内免费 | 1篇 |
专业分类
林业 | 9篇 |
农学 | 17篇 |
基础科学 | 4篇 |
47篇 | |
综合类 | 140篇 |
农作物 | 30篇 |
水产渔业 | 15篇 |
畜牧兽医 | 290篇 |
园艺 | 7篇 |
植物保护 | 42篇 |
出版年
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 8篇 |
2017年 | 21篇 |
2016年 | 11篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 17篇 |
2012年 | 34篇 |
2011年 | 32篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 35篇 |
2007年 | 22篇 |
2006年 | 26篇 |
2005年 | 15篇 |
2004年 | 24篇 |
2003年 | 33篇 |
2002年 | 25篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 11篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1987年 | 4篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1979年 | 4篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1900年 | 3篇 |
1899年 | 5篇 |
1898年 | 3篇 |
1892年 | 3篇 |
排序方式: 共有601条查询结果,搜索用时 31 毫秒
161.
162.
Cardamom is an important spice crops used all over the world as a flavoring agent of food materials. The productivity is limited by insect pests and thus effective insecticide which does not leave residues in the produce is the need of the hour. Diafenthiuron 50 WP @ 300 g a.i ha?1 was found effective in managing both the cardamom shoot and capsule borer, Conogethes punctiferalis Guenee and thrips, Sciothrips cardamomi Ramk and thus can be recommended for pest management. Cardamom capsules were collected from the plants that were sprayed with diafenthiuron at the recommended dose of 200 g a.i ha?1 and double the dose (400 g a.i ha?1), which were then analyzed under HPLC with a normal phase column. The diafenthiuron residue was below the detectable levels of 0.05 µg g?1 in the harvested produce (both fresh and cured) after twelve and fourteen days of spray. So, capsules can be harvested safely without any risk of insecticide residues 12 days after spraying of diafenthiuron and thus can be recommended for usage in cardamom plantations. 相似文献
163.
Chris Ojiewo Emmanuel Monyo Haile Desmae Ousmane Boukar Clare Mukankusi‐Mugisha Mahendar Thudi Manish K. Pandey Rachit K. Saxena Pooran M. Gaur Sushil K. Chaturvedi Asnake Fikre NPVR Ganga Rao CV SameerKumar Patrick Okori Pasupuleti Janila Jean Claude Rubyogo Chigeza Godfree Essegbemon Akpo Lucky Omoigui Stanley Nkalubo Berhanu Fenta Papias Binagwa Michael Kilango Magdalena Williams Omari Mponda David Okello Mekasha Chichaybelu Amos Miningou Joseph Bationo Dramane Sako Sory Diallo Candidus Echekwu Muhammad Lawan Umar Richard Oteng‐Frimpong Haruna Mohammed Rajeev K. Varshney 《Plant Breeding》2019,138(4):487-499
Legumes are important components of sustainable agricultural production, food, nutrition and income systems of developing countries. In spite of their importance, legume crop production is challenged by a number of biotic (diseases and pests) and abiotic stresses (heat, frost, drought and salinity), edaphic factors (associated with soil nutrient deficits) and policy issues (where less emphasis is put on legumes compared to priority starchy staples). Significant research and development work have been done in the past decade on important grain legumes through collaborative bilateral and multilateral projects as well as the CGIAR Research Program on Grain Legumes (CRP‐GL). Through these initiatives, genomic resources and genomic tools such as draft genome sequence, resequencing data, large‐scale genomewide markers, dense genetic maps, quantitative trait loci (QTLs) and diagnostic markers have been developed for further use in multiple genetic and breeding applications. Also, these mega‐initiatives facilitated release of a number of new varieties and also dissemination of on‐the‐shelf varieties to the farmers. More efforts are needed to enhance genetic gains by reducing the time required in cultivar development through integration of genomics‐assisted breeding approaches and rapid generation advancement. 相似文献
164.
Age and growth in southern bluefin tuna, Thunnus maccoyii (Castelnau): Direct estimation from otoliths, scales and vertebrae 总被引:1,自引:1,他引:0
John S. Gunn Naomi P. Clear Thor I. Carter Anthony J. Rees Clive A. Stanley Jessica H. Farley John M. Kalish 《Fisheries Research》2008,92(2-3):207-220
In the early 1990s, the spawning biomass of the southern bluefin tuna (SBT) population was estimated to be less than 10% of its historical level. However, major uncertainties surrounding the age composition of the catch confounded the virtual population analysis assessment models. To eliminate these uncertainties, validated estimates of the age composition of the catch were required.We examined scales, caudal vertebrae and sagittal otoliths to determine which structure produced the most accurate age estimates in SBT. Scales proved useful for estimating ages of SBT only up to 4 years. Marginal increment analysis verified that the zones of dense circuli visible on the scales were deposited annually up to this age. In larger fish, the compression of circuli on the margin of scales and high incidence of regenerated scales made estimation of age very difficult. Obvious increments were present on both the vertebrae and otoliths. Age estimates from the two structures matched closely for the first 10 years of life. However, in larger (older) fish the counts diverged, otoliths consistently providing higher age estimates. We determined that annual increments are formed on sagittal otoliths throughout life but that this is not the case in vertebrae, where bands are formed less frequently. Thus, vertebrae were unreliable for estimating age beyond 10 years, which corresponds approximately to the age-at-first maturity.Ages were estimated from otoliths of 1121 fish from throughout the species’ size range. These data indicate that SBT live to at least 40 years of age, twice the longevity previously accepted; that age at recruitment is 1 year, not 2; and that mean age-at-maturity is approximately 11 years, not 7.The age distribution of SBT catches by the Japanese longline fishery in the Tasman Sea indicate that a significant proportion of the SBT population in this area is over 25 years of age and that cohorts spawned in the late 1970s and early 1980s are markedly under-represented in the population. The latter is thought to result from intense exploitation on these cohorts by the Australian surface fishery soon after recruitment. 相似文献
165.
Myeong Whoon Seo Dong Sik Yang Stanley J. Kays Jun-Hong Kim Jin Ho Woo Kuen Woo Park 《Scientia Horticulturae》2009,122(3):369-374
The effect of nutrient solution electrical conductivity (EC) and sulfur (S), magnesium (Mg), and phosphorus (P) levels on the content of the primary sesquiterpene lactones (SLs), lactucin, 8-deoxylactucin, and lactucopicrin, in hydroponically grown lettuce was assessed. Lettuce grown at 4 EC levels (0.5, 1.0, 2.0, and 3.0 dS m−1) displayed significant differences in leaf area index, number of leaves, plant height, fresh weight per plant, and chlorophyll content that were highest at EC 2.0 dS m−1. Lactucin (5.5 μg g−1 dry weight), 8-deoxylactucin (7.5), lactucopicrin (35.8), and total SLs (48.7) concentraions were highest at EC 0.5 dS m−1. Four S (8, 16, 48, and 80 mg L−1) and Mg (6, 12, 36, and 60 mg L−1) levels and 3 P (8, 16, and 48 mg L−1) levels were assessed for their effect on individual and total SLs. S and P had the greatest effect on SL levels. Plants in the lowest S level had significantly higher lactucin, lactucopicrin and total SLs. Each of the SLs was higher in the highest P level while Mg influenced only the lactucopicrin level in a quadratic manner. The results indicate that solution culture conditions can strongly influence the SL concentration and therefore bitterness and acceptability of lettuce. 相似文献
166.
在实验室条件下,采用混合均匀的Alafia河表层沉积物并以蒸馏水为上覆水进行沉积物磷释放模拟试验,研究了溶解氧、有机碳和金属铝对沉积物磷(PO4-P)释放的影响.结果表明,试验期间厌氧条件下沉积物磷释放量明显高于好氧条件下.厌氧条件下,未添加金属铝、添加有机碳源的试验组中沉积物释放平衡时水中磷浓度为5.93 mg·L-1;好氧条件下,平衡时水中磷浓度为2.39mg·L-1.研究还发现,未添加金属铝的试验组,无论好氧还是厌氧条件下,未添加有机碳源时,沉积物磷释放量高于添加碳源条件;而在添加金属铝后,添加有机碳源的试验组中磷释放昔略高于未添加碳源的试验组.添加金属铝能够明显抑制沉积物中磷的释放.未添加金属铝,厌氧条件下,平衡时水中磷浓度为6.91 mg·L-1,好氧条件下,释放半衡时水中磷浓度为3.70nag·L-1;而添加金属铝的试验组,无论厌氧还是好氧条件下,上覆水中磷浓度均很小,接近于0 mg·L-1. 相似文献
167.
W F Robinson S E Shaw B Stanley C R Huxtable A D Watson S E Friend R Mitten 《Australian veterinary journal》1989,66(7):193-195
Chronic renal failure was diagnosed in 15 Bull terrier dogs. The dogs ranged in age from one to 8 years. History and clinical findings typically included lethargy, anorexia, polyuria, polydipsia and weight loss. Affected dogs were azotaemic, had elevated serum phosphate and cholesterol, and proteinuria was apparent in all dogs tested (13/13). The concentration of urine was consistently in the nil to minimally concentrated range (specific gravities 1.011-1.017). In those dogs necropsied, both kidneys were approximately two-thirds normal size, tough in consistency, with a pale cortex and a finely nodular capsular surface. Histologically, there was marked nephron loss, diffuse interstitial fibrosis and focal dense radial fibrosis which was especially evident in the renal medulla. Tubular dilation was widespread with focal mineralisation of tubular epithelium and adjacent basement membranes. Glomeruli were often shrunken and segmentally fibrotic. Some Bowman's spaces were extremely dilated. Many less severely affected glomeruli had thickened basement membranes. 相似文献
168.
169.
A high molecular weight crystalline protein, possessing the properties of ring spot virus and differing markedly from tobacco mosaic virus protein in its physical, chemical and serological properties, has been isolated by means of an ultracentrifuge from Turkish tobacco plants diseased with tobacco ring spot virus. Ultracentrifugal methods were also used to demonstrate that high molecular weight proteins are characteristic of other virus diseases. The concentration of the different virus proteins in the host was found to differ greatly. The quantity ultracentrifuge, used in conjunction with an analytical ultracentrifuge, has proven to be a powerful tool for the concentration, purification and crystallization of high molecular weight virus proteins and to be indispensable in the case of unstable viruses existing in low concentration in the host. 相似文献
170.