全文获取类型
收费全文 | 2064篇 |
免费 | 157篇 |
专业分类
林业 | 89篇 |
农学 | 41篇 |
基础科学 | 5篇 |
384篇 | |
综合类 | 265篇 |
农作物 | 102篇 |
水产渔业 | 150篇 |
畜牧兽医 | 981篇 |
园艺 | 61篇 |
植物保护 | 143篇 |
出版年
2024年 | 10篇 |
2023年 | 35篇 |
2022年 | 29篇 |
2021年 | 76篇 |
2020年 | 89篇 |
2019年 | 81篇 |
2018年 | 60篇 |
2017年 | 63篇 |
2016年 | 76篇 |
2015年 | 64篇 |
2014年 | 71篇 |
2013年 | 77篇 |
2012年 | 154篇 |
2011年 | 163篇 |
2010年 | 93篇 |
2009年 | 70篇 |
2008年 | 138篇 |
2007年 | 124篇 |
2006年 | 107篇 |
2005年 | 80篇 |
2004年 | 85篇 |
2003年 | 85篇 |
2002年 | 82篇 |
2001年 | 13篇 |
2000年 | 25篇 |
1999年 | 18篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1992年 | 8篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有2221条查询结果,搜索用时 15 毫秒
51.
52.
Laura Gmez-Montes Zaul García-Esquivel Louis R. D'Abramo Armando Shimada Carlos Vsquez-Pelez María Teresa Viana 《Aquaculture (Amsterdam, Netherlands)》2003,220(1-4):769-780
Juvenile green abalone Haliotis rufescens were grown under laboratory conditions at 21±1 °C and fed formulated diets consisting of different protein:energy ratios (mg protein/kcal), 62, 74, 85, 100, 108, for 60 days. The level of crude protein ranged from approximately 26% to 44% while the energy content remained constant at about 4.1 kcal g−1. Growth ranged from 3.63 to 12.33 mg day−1. The growth of abalone fed the 100 and 108 diets was significantly greater than that of each of the other diets. Protein efficiency ratio increased as the dietary protein content increased except for the T108 diet (44% crude protein). Abalone apparently consume food to satisfy an energy requirement. Caloric expenditure due to metabolism was estimated for abalone fed diets with protein ratios of 62, 85, 100. Energy loss due to respiration did not vary appreciably among abalone fed the different diets. The proportional distribution of dietary energy into fecal, digestible, growth, and metabolic energy was estimated for abalone fed these diets. Apparent dry matter digestibility was among the lowest for abalone fed the 100 P:E diet, but growth of abalone fed this diet was significantly higher than that of each of the other treatments except the 108 diet. Unexplained energy loss to achieve balance ranged from 7% to 28.5%, some of which is probably due to differential mucus and ammonia production. Results suggest a potential for the reduction of both dietary protein and lipid without causing any adverse effects on the growth response. 相似文献
53.
Larval traits of the Caribbean amphidromous goby Sicydium punctatum (Gobioidei: Sicydiinae) in Guadeloupe
下载免费PDF全文
![点击此处可从《Ecology of Freshwater Fish》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Léa Lejeune Hélène Tabouret Laura Taillebois Dominique Monti Philippe Keith 《Ecology of Freshwater Fish》2016,25(2):272-280
Amphidromous fish are the biggest contributor to the diversity of fish communities in river systems of Caribbean islands. Among them, Sicydium punctatum Perugia, 1896, which is endemic to the West Indies, represents the vast majority of fish in these rivers. The otolith microstructure and the biometry of S. punctatum postlarvae from Guadeloupe were investigated to explore the dispersal modalities of this species through an appreciation of the growth pattern, the pelagic larval duration (PLD) and the size‐at‐recruitment. The study was made on one cohort of 83 recruited postlarvae, fished at the Capesterre River's mouth on 2 November 2011. The mean (±SD) size‐at‐recruitment of the postlarvae was 24.6 ± 1.3 mm (range of 20.5–28.1 mm, n = 83). We found a mean (±SD) PLD of 72.2 ± 10.5 days (range of 54–101.5 days, n = 67). The growth rate estimated from the otolith increments showed a globally decreasing pattern during the marine larval phase. Growth rates at the beginning of the larval stage were significantly different between hatching periods, suggesting a relation between the hatching period and the growth rate in S. punctatum. This study adds on to the general understanding of the life cycle of S. punctatum in Guadeloupe that will help implement strategies to manage amphidromous fish populations in the Caribbean region. 相似文献
54.
George Eng Stephen P. Coddington Laura L. Stockton Alexander D. W. Acholonu 《Pest management science》1989,26(2):117-121
The effect of organotin compounds on the growth of Ceratocystis ulmi, the causative agent of Dutch elm disease, was studied in shake culture. Triphenyltin, (C6H5)3SnX, tricyclohexyltin, (C6H11)3SnX, and tributyltin, (C4H9)3SnX, compounds were all effective in the inhibition of C. ulmi in vitro. The anionic group, X, did not play a major role in the inhibitory activities of these compounds, suggesting that the species involved in the inhibition is R3Sn+ or the hydrated cation. 相似文献
55.
Diagnosis of cerebellar cortical degeneration in a Scottish terrier using magnetic resonance imaging
Primary cerebellar cortical degeneration (CCD), also termed abiotrophy, is the spontaneous premature degeneration of fully differentiated neurological tissue. Cerebellar hypoplasia shares many morphological features with primary CCD, both conditions being characterised by decreased cerebellar size, with reduced numbers of Purkinje and granular cells. CCD has been identified in many canine breeds. This is the first report of the syndrome in a Scottish terrier. The patient presented with mild, gradually progressive ataxia. Survey radiographs of the cervical spine and cerebrospinal fluid (CSF) analysis were normal. CSF distemper and Toxoplasma titres were negative. A diagnosis of cerebellar atrophy was made based on magnetic resonance imaging. The progressive clinical signs suggested cerebellar degeneration rather than hypoplasia. On necropsy, the cerebellum showed macroscopic and microscopic changes consistent with primary CCD. 相似文献
56.
Evaluation of an air-filtration system for preventing aerosol transmission of Porcine reproductive and respiratory syndrome virus
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Scott Dee Laura Batista John Deen Carlos Pijoan 《Canadian journal of veterinary research》2005,69(4):293-298
The purpose of this study was to evaluate the ability of a commercial air-filtration system to reduce aerosol transmission of Porcine reproductive and respiratory syndrome virus (PRRSV). The system consisted of a pre-filter and 2 filters with EU8 and EU13 ratings. In each of 4 trials, 5 PRRSV-infected donor pigs and 1 naive recipient pig (each 25 kg) were housed in opposing chambers connected by a 1.3-m-long duct. The system filtered air entering 1 recipient-pig chamber (filtered facility) from the donor-pig chamber but not a 2nd recipient-pig chamber (nonfiltered facility). The donor pigs had been experimentally infected with PRRSV MN-184, an isolate previously documented to be shed at a high frequency in contagious aerosols. On days 3 to 7 after infection of the donors, the 2 groups were housed in their respective chambers for 6 h and then in separate facilities, where samples were collected for testing by polymerase chain reaction and enzyme-linked immunosorbent assay over 14 d. Aerosol transmission was observed in 6 of the 20 replicates in the nonfiltered facility, whereas all pigs remained PRRSV-negative in the filtered facility; the difference was significant at P < 0.01. Thus, under the conditions of this study, the air-filtration system evaluated appeared to be highly effective at reducing aerosol transmission of PRRSV. 相似文献
57.
58.
Moore DA Atwill ER Kirk JH Brahmbhatt D Herrera Alonso L Hou L Singer MD Miller TD 《Journal of the American Veterinary Medical Association》2003,223(6):839-845
OBJECTIVE: To evaluate the effect of daily oral administration of decoquinate to neonatal calves experimentally challenged with various numbers of Cryptosporidium parvum oocysts. DESIGN: Clinical trial. ANIMALS: 75 calves. PROCEDURE: Calves were purchased from a commercial dairy during a 5-week period. Calves were housed in individual hutches and fed milk replacer with or without decoquinate (2 mg/kg [0.9 mg/lb per day]). Calves were randomly assigned to treatment and 1 of 5 challenge groups (0, 50, 100, 1000, or 10,000 C. parvum oocysts in 60 mL of saline [0.9% NaCl] solution administered p.o. on the day after arrival). Calves were maintained in the study for as long as 28 days. Calves were clinically assessed for diarrhea and dehydration. Fecal samples were submitted for oocyst enumeration 3 times each week. RESULTS: Treatment did not affect number of days to first watery feces (diarrhea), number of days to first oocyst shedding, or duration of diarrhea or oocyst shedding. Duration of oocyst shedding was significantly associated with challenge dose of oocysts administered to calves and number of days to first oocyst shedding. Duration of diarrhea and number of days to first oocyst shedding were significantly associated with week of arrival and number of days to first watery diarrhea. CONCLUSIONS AND CLINICAL RELEVANCE: Daily treatment with decoquinate at the dosage used in this study did not affect oocyst shedding or clinical signs associated with cryptosporidiosis. However, there was an indication that if the number of oocysts calves received could be reduced, then the duration of oocyst shedding and, hence, environmental loading of C. parvum oocysts could be reduced. 相似文献
59.
Clooten JK Woods JP Smith-Maxie LL 《The Canadian veterinary journal. La revue veterinaire canadienne》2003,44(6):480-483
A 21-month-old, castrated male Vizsla was presented for pelvic limb weakness, difficulty opening his mouth, ptyalism, voice change, and urinary incontinence. Myasthenia gravis and masticatory myositis were diagnosed. The unusual clinical findings, diagnosis, treatment, and case outcome are described, followed by a brief discussion of myasthenia gravis and masticatory myositis. 相似文献
60.
McKenna SL Barkema HW McClure JT Rogers LA 《The Canadian veterinary journal. La revue veterinaire canadienne》2003,44(4):312-313
A 2-year-old, purebred Holstein heifer with exercise intolerance and cardiovascular compromise was diagnosed at postmortem with tetralogy of Fallot, which typically results in death within a few months of life. Survival past the age of 2 was unexpected. The concurrent endocarditis of the pulmonic valve is discussed. 相似文献