全文获取类型
收费全文 | 3289篇 |
免费 | 138篇 |
国内免费 | 3篇 |
专业分类
林业 | 236篇 |
农学 | 463篇 |
基础科学 | 87篇 |
853篇 | |
综合类 | 84篇 |
农作物 | 271篇 |
水产渔业 | 70篇 |
畜牧兽医 | 982篇 |
园艺 | 100篇 |
植物保护 | 284篇 |
出版年
2023年 | 23篇 |
2022年 | 38篇 |
2021年 | 51篇 |
2020年 | 86篇 |
2019年 | 87篇 |
2018年 | 119篇 |
2017年 | 137篇 |
2016年 | 108篇 |
2015年 | 83篇 |
2014年 | 95篇 |
2013年 | 296篇 |
2012年 | 140篇 |
2011年 | 157篇 |
2010年 | 126篇 |
2009年 | 114篇 |
2008年 | 112篇 |
2007年 | 138篇 |
2006年 | 143篇 |
2005年 | 110篇 |
2004年 | 71篇 |
2003年 | 77篇 |
2002年 | 72篇 |
2001年 | 57篇 |
2000年 | 51篇 |
1999年 | 53篇 |
1998年 | 41篇 |
1997年 | 43篇 |
1996年 | 34篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 38篇 |
1988年 | 45篇 |
1987年 | 34篇 |
1986年 | 29篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 26篇 |
1982年 | 22篇 |
1980年 | 34篇 |
1979年 | 37篇 |
1978年 | 20篇 |
1976年 | 20篇 |
1971年 | 20篇 |
1970年 | 37篇 |
1969年 | 24篇 |
1968年 | 23篇 |
排序方式: 共有3430条查询结果,搜索用时 15 毫秒
51.
A laboratory study was conducted at the Indian Agricultural Research Institute, New Delhi on a sandy clay loam soil of pH 7.9 and organic C content of 0.34% to study the effect of incorporating Sesbania or Vigna legume residues or wheat straw at 15 and 30t ha?1 on temporal variation in ammoniacal and nitrate‐N in soil under submergence and well drained conditions. Under submergence most mineral N was present as ammoniacal‐N, while under well drained conditions it was present as Nitrate‐N. The content of ammoniacal N in soil was the highest after 30 days of incubation and declined thereafter under submergence. On the other hand under well drained conditions the mineral‐N (mostly nitrate) content in soil at 30 DAI was very little and showed increases only later, reaching the highest level at 90 DAI. Application of wheat straw specially at 301 ha?1 level resulted in immobilization of native soil‐N. These results show that rice which is grown under submergence can be transplanted soon after incorporation of legume residues, but for wheat or other crops which are grown under well drained condition a time interval of 30 days or more needs to be provided before sowing the crop. 相似文献
52.
DL-α-Difluoromethylornithine (DFMO), a specific suicide inhibitor of the polyamine biosynthetic enzyme ornithine decarboxylase
(EC 4.1.1.17), strongly inhibited mycelial growth and sporidial formation of the wheat pathogen,Neovossia indica, in vitro, while DL-α-difluoromethylarginine (DFMA), the analogous suicide inhibitor of arginine decarboxylase (EC 4.1.1.19), did not.
The inhibited mycelial growth and sporidial formation were not only restored by putrescine (polyamine) addition, but were
actually enhanced in the putrescine + DFMO cultures. Besides altering mycelial growth and morphology, DFMO also reduced the
cell size drastically. The inhibition of fungal polyamine biosynthesis is discussed in relation to selective control of plant
disease. 相似文献
53.
Uma S. Singh 《Pest management science》1989,25(2):145-154
[14C]metalaxyl applied to seeds, roots and leaves of cowpea was readily taken up by all plant parts and a major fraction of it was retained within the treated leaves and seeds but not in the roots. The fungicide exhibited ambimobility inside the plant. When applied to the middle of leaflets, metalaxyl mobilised towards proximal and distal parts of the leaflet. Intraleaflet movement seemed to result from translocation through veins and diffusion through cell walls and intercellular spaces. Accumulation of metalaxyl at tips and margins of primary leaves followed application to roots. Metalaxyl was readily extracted from most plant parts except cotyledons and only 0.8% of the fungicide applied as a seed treatment was recovered from 50-day-old plants. 相似文献
54.
A series of substituted 4-methylcoumarins was synthesised and the members tested for their toxicity towards mycelial growth of seven phytopathogenic fungi in culture. Rhizoctonia solani, Alternaria alternata and Fusarium solani exhibited maximum sensitivity to these compounds whereas Pythium aphanidermatum, Colletotrichum falcatum, Drechslera oryzae and Macrophomina phaseolina were relatively less sensitive. 6-Ethyl-3-n- propyl-7-hydroxy4-methylcoumarin ( I ) was relatively toxic towards all fungi except C. falcatum, P. aphanidermatum and M. phaseolina. The 6-n-butyl ( III ) and 6-(1, 1, 3, 3-tetramethylbutyl) ( VI ) derivatives were highly toxic to R. solani with EC50, values of lμg ml?1. 相似文献
55.
Seeds of 49 accessions of corn (Zea mays ssp. mays), 9 accessions of teosinte (Zea species that are thought to be ancestors and probable progenitors to corn), and 3 accessions of Job's tears (Coix lacryma), obtained from a germplasm repository, were ground and extracted with hexane. Whole kernel oil yields and levels of four phytonutrients (free phytosterols, fatty acyl phytosterol esters, ferulate phytosterol esters, and gamma-tocopherol) in the oils were measured. Among the seeds tested, oil yields ranged from 2.19 to 4.83 wt %, the levels of ferulate phytosterol esters in the oil ranged from 0.047 to 0.839 wt %, the levels of free phytosterols in the oil ranged from 0.54 to 1.28 wt %, the levels of phytosterol fatty acyl esters in the oil ranged from 0.76 to 3.09 wt %, the levels of total phytosterols in the oil ranged from 1.40 to 4.38 wt %, and the levels of gamma-tocopherol in the oil ranged from 0.023 to 0.127 wt %. In general, higher levels of all three phytosterol classes were observed in seed oils from accessions of Zea mays ssp. mays than in seed oils from accessions of the other taxonomic groups. The highest levels of gamma-tocopherol were observed in teosinte accessions. 相似文献
56.
The ovipositional response ofHelicoverpa armigera (Hübner) to different cotton varieties and species was studied under caged conditions. Maximum oviposition (51.6 eggs/female)
was recorded on LH 900, a variety ofGossypium hirsutum, and minimum oviposition (3.0 eggs/female) on G 27, a variety ofG. arboreum. Oviposition, in general, was low (3 to 6.5 eggs/female) onarboreum cottons as compared withhirsutum. Of the number of factors found to affect the oviposition ofH. armigera, the trichome length on the upper surface of the leaf, rather than the density, was positively correlated (r = 0.687*). Among
different months in the cropping season, oviposition was maximum (552.7) during April. Oviposition was higher on leaves than
on other plant parts. 相似文献
57.
58.
59.
Twenty-six pigs from four litters in a healthy herd of swine were examined periodically for the fecal excretion of viruses by the use of porcine kidney cell cultures. Viruses were initially isolated from all pigs between 34 to 64 days of age. The pigs within each litter began shedding virus in their feces approximately at the same time, usually within one week, and the type of virus initially recovered was usually the same. Subsequently, waves of infection with different enteroviruses appeared to occur during the observation period of six months. At least six antigenically different viruses were isolated from this herd over a 26-month period. Most, if not all, of these viruses were considered to belong to the enterovirus group. No disease was associated with these enteroviral infections.
The colostrum and milk of sows contained significant amounts of enteroviral antibodies. Prior to nursing, the serum of new-born pig contained no enteroviral antibodies but, shortly after nursing, high titers of such antibodies were present in the serum. Antibodies were detected in the feces of suckling pigs.
相似文献60.