全文获取类型
收费全文 | 2924篇 |
免费 | 169篇 |
国内免费 | 5篇 |
专业分类
林业 | 178篇 |
农学 | 96篇 |
基础科学 | 22篇 |
452篇 | |
综合类 | 471篇 |
农作物 | 137篇 |
水产渔业 | 297篇 |
畜牧兽医 | 1064篇 |
园艺 | 88篇 |
植物保护 | 293篇 |
出版年
2023年 | 26篇 |
2022年 | 22篇 |
2021年 | 60篇 |
2020年 | 73篇 |
2019年 | 75篇 |
2018年 | 76篇 |
2017年 | 71篇 |
2016年 | 62篇 |
2015年 | 64篇 |
2014年 | 86篇 |
2013年 | 115篇 |
2012年 | 170篇 |
2011年 | 222篇 |
2010年 | 120篇 |
2009年 | 102篇 |
2008年 | 170篇 |
2007年 | 195篇 |
2006年 | 177篇 |
2005年 | 161篇 |
2004年 | 181篇 |
2003年 | 178篇 |
2002年 | 151篇 |
2001年 | 35篇 |
2000年 | 21篇 |
1999年 | 25篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 21篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 23篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 16篇 |
1976年 | 8篇 |
1975年 | 14篇 |
1974年 | 8篇 |
1973年 | 14篇 |
排序方式: 共有3098条查询结果,搜索用时 218 毫秒
21.
22.
23.
24.
Jeann Leal de Araújo Alice C. A. M. Arruda Nayadjala T. A. Santos Glenison F. Dias Thiago F. L. Nery Fabio Del Piero Richard Ploeg Brian F. Porter Ingeborg M. Langohr 《Journal of veterinary diagnostic investigation》2021,33(3):600
A 4-mo-old northern red-shouldered macaw (Diopsittaca nobilis) was admitted to the veterinary hospital of the Arruda Câmara Zoo, in the State of Paraiba, Brazil, for investigation of an orbital mass. Given rapid progression and lack of response to treatment, the bird was euthanized, and an autopsy was performed. Histologically, the mass consisted of a retrobulbar invasive tumor characterized by tubular and rosette-like structures, with interspersed heteroplastic tissues, such as aggregates of neuroglial cells and islands of hyaline cartilage. The tumor was immunopositive for pancytokeratin, GFAP, NSE, and S100. These findings were compatible with an ocular teratoid medulloepithelioma, a neoplasm best described in humans but also reported rarely in young cockatiels and African Grey parrots. 相似文献
25.
A long-term rangeland monitoring programme needs to employ a field survey technique that is practicable, precise, powerful enough to distinguish change, not prone to worker bias, and able to distinguish real change from operator error arising from staff turnover. These criteria were used to evaluate a widely used grassland sampling technique in South Africa – the nearest-plant (with 200 points) method (NP) – against common alternatives, namely NP excluding forbs (NP-nf), the plant number scale (PNS; a cover-abundance method) and quadrat frequency (QF), using multivariate ordination and permutation tests. Four trained teams surveyed four grasslands using each method. PNS took more than twice as long as the other techniques, which were similarly rapid. Estimates of composition using NP methods were the most precise and PNS was least repeatable, with QF intermediate. Compositional differences between sites were most finely distinguished using NP-nf, followed by NP and QF. PNS was able to detect only marked differences and had the greatest potential for surveyor bias. The NP method, with or without including forbs, is therefore recommended for monitoring the species composition of mesic, dense grassland. Some suggestions for monitoring agencies on how best to use multivariate methods are presented. 相似文献
26.
Rita M. Hanel DVM DACVIM DACVECC Lee Palmer DVM MS DACVECC NREMT‐T WEMT CCRP Janice Baker DVM DACVPM Jo‐Anne Brenner BA EMT‐I EMT‐T David Dorman DVM PhD DABVT John C. Gicking DVM DACVECC Brian Gilger DVM MS DACVO DABT Cynthia M. Otto DVM PhD DACVECC DACVSMR Elizabeth Rozanski DVM DACVECC DACVIM Brian Trumpatori DVM 《Journal of Veterinary Emergency and Critical Care》2016,26(2):166-233
27.
Theory of mind (ToM) to infer other people's current mental states and episodic memory of personal happenings have been assumed to be closely related. We report two participants with severely impaired episodic memory who perform indistinguishably from healthy controls on objective ToM tests. These results suggest that ToM can function independently of episodic memory. 相似文献
28.
Young BC Strom AM Prittie JE Barton LJ 《Journal of the American Veterinary Medical Association》2007,231(1):74-78
CASE DESCRIPTION: 2 dogs were evaluated because of vomiting and lethargy (a Toy Poodle; dog 1) and acute respiratory distress, vomiting, and anorexia (a Chihuahua; dog 2). Dog 1 had been exposed to a commercial hydrocarbon waterproofing spray 24 hours before the development of clinical signs, and dog 2 was examined 18 hours after exposure to a waterproofing spray containing heptane, a highly flammable liquid hydrocarbon. CLINICAL FINDINGS: In both dogs, major gastrointestinal tract abnormalities were ruled out but respiratory status worsened. Thoracic radiography revealed a diffuse interstitial pulmonary pattern, and hypoxemia was detected. TREATMENT AND OUTCOME: Hospitalization for monitoring and care was required for both dogs. The dogs recovered with supportive care, which included administration of oxygen, fluids, and bronchodilators. Additionally, dog 1 received glucocorticoids via inhalation and supplemental enteral nutrition, whereas dog 2 was treated with an antimicrobial. CLINICAL RELEVANCE: The dogs of this report developed hydrocarbon pneumonitis following exposure to waterproofing sprays. Such sprays contain potentially toxic hydrocarbons. The severity of the adverse effects associated with exposure may have been amplified because the dogs were physically small and were exposed to a relatively large amount of aerosolized spray within small areas. Development of chemical pneumonitis in pet animals is best prevented by application of waterproofing sprays in well-ventilated or outdoor areas from which pets have been excluded. With prolonged hospitalization and considerable monitoring and care, affected dogs can recover from these exposures. 相似文献
29.
Booker CW Abutarbush SM Schunicht OC Jim GK Perrett T Wildman BK Guichon PT Pittman TJ Jones C Pollock CM 《Veterinary therapeutics : research in applied veterinary medicine》2007,8(3):183-200
The purpose of this study was to determine the efficacy and cost-effectiveness of tulathromycin (DRAX) versus tilmicosin (MIC) or oxytetracycline (TET) as a metaphylactic antimicrobial in feedlot calves. Calves that received DRAX had significantly (P<.05) lower initial undifferentiated fever (UF) treatment and relapse rates; lower overall chronicity, overall mortality, and cause-specific mortality rates; higher average daily gains; and improved quality grades. However, calves that received DRAX also had poorer (P<.05) yield grades compared with calves that received MIC or TET and worse feed conversion compared with calves that received MIC. Net advantages in the DRAX group were 3.79CanDollars/animal and 16.96CanDollars/animal compared with the MIC and TET groups, respectively. Based on these results, DRAX is a more efficacious and cost-effective metaphylactic antimicrobial than MIC or TET in feedlot calves at ultra-high risk of developing UF. In addition, this study presents a comparison between two methods ("deads out" and "deads in") of calculating feedlot performance variables. 相似文献
30.
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