全文获取类型
收费全文 | 5460篇 |
免费 | 322篇 |
国内免费 | 6篇 |
专业分类
林业 | 801篇 |
农学 | 119篇 |
基础科学 | 19篇 |
1032篇 | |
综合类 | 543篇 |
农作物 | 177篇 |
水产渔业 | 334篇 |
畜牧兽医 | 2220篇 |
园艺 | 125篇 |
植物保护 | 418篇 |
出版年
2023年 | 35篇 |
2022年 | 39篇 |
2021年 | 76篇 |
2020年 | 83篇 |
2019年 | 69篇 |
2018年 | 162篇 |
2017年 | 177篇 |
2016年 | 168篇 |
2015年 | 116篇 |
2014年 | 157篇 |
2013年 | 287篇 |
2012年 | 338篇 |
2011年 | 325篇 |
2010年 | 182篇 |
2009年 | 167篇 |
2008年 | 279篇 |
2007年 | 318篇 |
2006年 | 311篇 |
2005年 | 275篇 |
2004年 | 273篇 |
2003年 | 258篇 |
2002年 | 236篇 |
2001年 | 145篇 |
2000年 | 134篇 |
1999年 | 92篇 |
1998年 | 46篇 |
1997年 | 38篇 |
1996年 | 43篇 |
1995年 | 72篇 |
1994年 | 27篇 |
1993年 | 39篇 |
1992年 | 40篇 |
1991年 | 33篇 |
1990年 | 47篇 |
1989年 | 30篇 |
1988年 | 41篇 |
1987年 | 30篇 |
1986年 | 28篇 |
1985年 | 28篇 |
1984年 | 33篇 |
1983年 | 37篇 |
1982年 | 20篇 |
1980年 | 32篇 |
1979年 | 21篇 |
1978年 | 30篇 |
1977年 | 22篇 |
1976年 | 20篇 |
1973年 | 21篇 |
1971年 | 18篇 |
1970年 | 22篇 |
排序方式: 共有5788条查询结果,搜索用时 312 毫秒
51.
A neurologic syndrome in Golden Retrievers presenting as a sensory ataxic neuropathy 总被引:1,自引:0,他引:1
Jäderlund KH Orvind E Johnsson E Matiasek K Hahn CN Malm S Hedhammar A 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2007,21(6):1307-1315
BACKGROUND: A sensory ataxic neuropathy has been observed in Swedish Golden Retrievers recently. ANIMALS: Twenty-one affected Golden Retrievers. METHODS: Clinical and neurologic status, electrophysiologic, and pathologic status as well as pedigree analyses were evaluated. RESULTS: Clinical signs had an insidious onset between 2 and 8 months of age and a slowly progressive course. Affected dogs were ataxic and dysmetric. They had abnormal postural reactions and decreased spinal reflexes but no apparent muscle atrophy. Clinical pathology, radiography, and electrophysiology of motor systems were all within reference values. Sensory nerve conduction results of affected dogs were significantly different from those of a group of control dogs. Necropsy revealed a chronic progressive central and peripheral sensorimotor axonopathy; the proprioceptive pathways were most severely affected. CONCLUSIONS AND CLINICAL IMPORTANCE: This disease in these Golden Retrievers is distinct from other canine breed-related neurodegenerative diseases or hereditary neurodegenerative diseases described in humans. Pedigree analyses indicated a hereditary background, but the mode of inheritance could not be established. 相似文献
52.
Feline calicivirus (FCV) is an important and highly prevalent pathogen of cats. It belongs to the family Caliciviridae which includes other significant pathogens of man and animals. As an RNA virus, high polymerase error rates convey upon FCV a high genome plasticity, and allow the virus to respond rapidly to environmental selection pressures. This makes the virus very adaptable and has important implications for clinical disease and its control. Being genetically diverse, FCV is associated with a range of clinical syndromes from inapparent infections to relatively mild oral and upper respiratory tract disease with or without acute lameness. More recently, highly virulent forms of the virus have emerged associated with a systemic infection that is frequently fatal. A proportion of FCV infected cats that recover from acute disease, remain persistently infected. In such cats, virus evolution is believed to help the virus to evade the host immune response. Such long-term carriers may only represent a minority of the feline population but are likely to be crucial to the epidemiology of the virus. Vaccination against FCV has been available for many years and has effectively reduced the incidence of clinical disease. However, the vaccines do not prevent infection and vaccinated cats can still become persistently infected. In addition, FCV strain variability means that not all strains are protected against equally. Much progress has been made in understanding the biology and pathogenesis of this important feline virus. Challenges for the future will necessarily focus on how to control the variability of this virus particularly in relation to emerging virulent strains and vaccination. 相似文献
53.
Feline herpesvirus (FHV-1; felid herpesvirus 1 (FeHV-1)) is an alphaherpesvirus of cats closely related to canine herpesvirus-1 and phocine herpesvirus-1. There is only one serotype of the virus and it is relatively homogenous genetically. FeHV-1 is an important cause of acute upper respiratory tract and ocular disease in cats. In addition, its role in more chronic ocular disease and skin lesions is increasingly being recognised. Epidemiologically, FeHV-1 behaves as a typical alphaherpesvirus whereby clinically recovered cats become latently infected carriers which undergo periodic episodes of virus reactivation, particularly after a stress. The primary site of latency is the trigeminal ganglion. Conventional inactivated and modified-live vaccines are available and protect reasonably well against disease but not infection, although viral shedding may be reduced. Genetically engineered vaccines have also been developed, both for FeHV-1 and as vector vaccines for other pathogens, but none is as yet marketed. 相似文献
54.
Farnaz Kordbacheh Charles L. Mohler Alan G. Taylor Anna S. Westbrook Hamid Rahimian-Mashhadi Hassan M. Alizadeh Antonio DiTommaso 《Weed Research》2023,63(1):34-44
Abutilon theophrasti (velvetleaf) is a widespread and problematic annual weed. Greenhouse and field experiments were conducted to investigate the effects of different cutting methods on the viability of A. theophrasti seeds. Three cutting methods were assessed: (1) Entire plant cut and dried (EPD)—plants were cut at soil level and dried with capsules attached on the greenhouse bench or soil surface for 4 weeks; (2) capsules detached and dried (CD)—capsules were removed from plants and dried for 4 weeks; and (3) capsules detached and tested while fresh (CF)—a control treatment. Before drying, the developmental stage (stage one, dark green; stage two, light green; stage three, yellowish-green; or stage four, black with the slightly open capsule) and age (days after flowering, DAF) of each capsule was recorded. Seed viability was measured immediately in the CF treatment and after the 4-week drying period in the EPD and CD treatments. No seeds in the EPD and CD treatments were viable when harvested at the first developmental stage (1–8 DAF) in either experiment, but 100% of seeds in the CF treatment in the field were viable when harvested at 8 DAF. In both greenhouse and field experiments, seeds attained full viability at earlier harvest ages in CF than in EPD or CD treatments, suggesting that seeds might become viable relatively early in development but lose viability if allowed to dry. These findings could be applied to optimise late-season mechanical control of A. theophrasti. 相似文献
55.
56.
57.
58.
59.
Goyette Jean-Olivier Cimon-Morin Jérôme Mendes Poliana Thériault Maxime Pellerin Stéphanie Poulin Monique 《Landscape Ecology》2021,36(9):2691-2706
Landscape Ecology - Human activities have led to the degradation of wetlands, impinging on their capacity to deliver essential ecosystem services to society. Wetland restoration now appears an... 相似文献
60.
Alan Williams 《Pest management science》1996,46(1):3-9
Chiral compounds account for 25% of all agrochemical compounds used commercially and for 26% of the total value of the world agrochemical market. However, those sold in single isomer form contribute only 7% to the market value despite many potential advantages in terms of regulatory, intellectual property and marketing benefits. Limited access to chiral raw materials and economic synthesis routes are key reasons why single isomers are less common than they might be. The development of more chiral routes will encourage the development of single isomer compounds to capitalise on their advantages. 相似文献