全文获取类型
收费全文 | 1095篇 |
免费 | 68篇 |
国内免费 | 1篇 |
专业分类
林业 | 48篇 |
农学 | 34篇 |
基础科学 | 4篇 |
121篇 | |
综合类 | 272篇 |
农作物 | 57篇 |
水产渔业 | 60篇 |
畜牧兽医 | 497篇 |
园艺 | 11篇 |
植物保护 | 60篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 19篇 |
2019年 | 28篇 |
2018年 | 16篇 |
2017年 | 27篇 |
2016年 | 23篇 |
2015年 | 18篇 |
2014年 | 28篇 |
2013年 | 51篇 |
2012年 | 50篇 |
2011年 | 51篇 |
2010年 | 31篇 |
2009年 | 26篇 |
2008年 | 55篇 |
2007年 | 52篇 |
2006年 | 36篇 |
2005年 | 44篇 |
2004年 | 42篇 |
2003年 | 49篇 |
2002年 | 39篇 |
2001年 | 29篇 |
2000年 | 26篇 |
1999年 | 22篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 8篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 13篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 15篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 16篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 6篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 7篇 |
排序方式: 共有1164条查询结果,搜索用时 0 毫秒
991.
Abstract Malignant catarrhal fever was transmitted from affected to recipient red deer (Cervus eluphus) using bloodor lymphoid suspension as inoculum. Incubation periods ranged from 11 to 26 days. The disease was also transmitted using lymphoid suspension stored overnight at 4°C or at ?70°C for 8 months. The experimental disease was characterised by fever, depression, anorexia, diarrhoea and dysentry. The course of the disease was approximately 96 hours. Major lesions consisted of acute mesenteric lymphadenitis and acute haemorrhagic typhlitis and colitis. Lesions in the caecum and colon started as multifocal mucosal haemorrhages and progressed rapidly to massive mucosal haemorrhage. 相似文献
992.
Eric A. Ferrell DVM Patrick R. Gavin DVM PhD Russell L. Tucker DVM Debra C. Sellon DVM PhD MelissaT. Hikes DVM PhD 《Veterinary radiology & ultrasound》2002,43(6):510-516
Magnetic resonance (MR) imaging was used as a neurodiagnostic modality in the assessment of 12 horses with neurologic disease localized cranial to the foramen magnum. This retrospective study included a mixed population of horse breeds and consisted of three foals and nine adult horses. MR sequences of the head and central nervous system of each horse were acquired. Routine MR sequences included transverse T1 weighted (T1wt), T2 weighted (T2wt), and proton density images. Additional imaging sequences were obtained on a patient-dependent basis. Eight neurologic related diseases were diagnosed. MRI imaging of the horse head is a feasible and valuable neurodiagnostic modality in the assessment of equine neurologic diseases. 相似文献
993.
994.
ABSTRACT The source of nitrogen (N) used in soil fertility practices affects plant growth, nutrient absorption, and the availability of nutrients. Consequently, the potential of plants to extract zinc (Zn) from soils may be increased by controlling the ratio of NH4 + to NO3 ? to maximize growth and Zn accumulation. The objectives of this research were to determine the effects of Zn supply and different molar ratios of NH4 + to NO3 ? on growth and Zn accumulation in Indian mustard (Brassica juncea Czern.). In a factorial experiment with solution culture, Indian mustard (accession 182921) was supplied with two concentrations of Zn (0.05 and 4.0 mg L?1) in combination with six N treatments with different molar percentage ratios of NH4 + to NO3 ? (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50) for three weeks. Zinc supplied at 0.05 mg Zn L?1 represented a common concentration of Zn in solution culture, whereas 4.0 mg Zn L?1 was excessive for plant nutrition. If the supply of Zn in solution was excessive, plants developed symptoms of foliar chlorosis, which became severe if plants were supplied with 80% of N as NO3 ?. Supplying high proportions of NO3 ? in the nutrient medium stimulated Zn accumulation, whereas increasing proportions of NH4 + (up to 50% of the total N) enhanced shoot growth. The pH of nutrient solutions generally decreased with increasing proportion of NH4 + in solutions and with increased Zn supply. The Zn phytoextraction potential of Indian mustard was maximized, at about 15 mg Zn plant?1, if plants received 10% of the total N as NH4 + and 90% as NO3 ?. 相似文献
995.
996.
997.
998.
999.
An analysis of cellulose crystallite width, microfibril angle and wood density after the time of thinning (at 8 years) in
straight vertical trees was undertaken in a 13-year-old E. globulus trial designed to assess the effect of thinning on tension wood formation. The most important effect was on cellulose crystallite
width, which increased with thinning intensity and this was mitigated where fertilizer was applied at the time of thinning.
Given the relationship between high crystallite width and tension wood occurrence the results demonstrate that heavy thinning
of E. globulus at this age can contribute to tension wood formation. However, tension wood production may be significantly reduced where
fertilizer is applied. This is possibly because increased diameter growth as a response to fertilizer application stabilises
the stems and this is the mechanism by which trees cope with internal stresses that are generated from wind in destabilsed
stands following thinning. In contrast, trees that respond poorly to thinning produce tension wood. 相似文献
1000.
Willoughby Ian; Stokes Victoria; Poole Jane; White John E. J.; Hodge Simon J. 《Forestry》2007,80(5):531-553
A series of species trials were set up to investigate the establishmentand early growth (up to 14 years old) of 44 native and non-nativetree species on a variety of different site types in lowlandBritain. On good quality lowland afforestation sites, Platanusx hispanica (London plane) established and grew more successfullythan the native trees tested, and may be an example of a speciesthat could theoretically be established in anticipation of futureclimate change. Experiments on a variety of community woodlandsites indicated that a range of exotic species, such as X Cupressocyparisleylandii (Leyland cypress), may have the potential for establishinga woodland cover on poorly restored land where few other treeswould grow. However, on less challenging, better restored sites,a wide range of native species also grew successfully. Furtherlong-term and larger scale trials on a wider variety of sitesare required to confirm the potential of the species testedfor British conditions. The results from these experiments alsoshowed that relative growth rates of different species can varythrough time, highlighting the danger in making premature judgementsabout species suitability based solely on very early tree growth. 相似文献