全文获取类型
收费全文 | 79240篇 |
免费 | 4255篇 |
国内免费 | 93篇 |
专业分类
林业 | 3195篇 |
农学 | 2044篇 |
基础科学 | 463篇 |
8591篇 | |
综合类 | 15514篇 |
农作物 | 3141篇 |
水产渔业 | 3428篇 |
畜牧兽医 | 41918篇 |
园艺 | 847篇 |
植物保护 | 4447篇 |
出版年
2019年 | 722篇 |
2018年 | 1092篇 |
2017年 | 1212篇 |
2016年 | 1048篇 |
2015年 | 906篇 |
2014年 | 1192篇 |
2013年 | 2625篇 |
2012年 | 2122篇 |
2011年 | 2594篇 |
2010年 | 1625篇 |
2009年 | 1727篇 |
2008年 | 2610篇 |
2007年 | 2423篇 |
2006年 | 2297篇 |
2005年 | 2153篇 |
2004年 | 2086篇 |
2003年 | 2154篇 |
2002年 | 1941篇 |
2001年 | 2409篇 |
2000年 | 2449篇 |
1999年 | 1879篇 |
1998年 | 723篇 |
1997年 | 714篇 |
1996年 | 713篇 |
1995年 | 808篇 |
1993年 | 744篇 |
1992年 | 1567篇 |
1991年 | 1765篇 |
1990年 | 1650篇 |
1989年 | 1656篇 |
1988年 | 1487篇 |
1987年 | 1541篇 |
1986年 | 1606篇 |
1985年 | 1557篇 |
1984年 | 1193篇 |
1983年 | 1067篇 |
1982年 | 707篇 |
1979年 | 1157篇 |
1978年 | 900篇 |
1977年 | 759篇 |
1975年 | 775篇 |
1974年 | 1028篇 |
1973年 | 1032篇 |
1972年 | 1048篇 |
1971年 | 1001篇 |
1970年 | 988篇 |
1969年 | 904篇 |
1968年 | 811篇 |
1967年 | 800篇 |
1966年 | 732篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
953.
954.
955.
A Field Trial of a Pilated Moraxella bovis Bacterin for the Prevention of Infectious Bovine Keratoconjunctivitis 下载免费PDF全文
Bateman KG Leslie KE Scholl TP 《The Canadian veterinary journal. La revue veterinaire canadienne》1986,27(1):23-27
Two field trials were conducted to evaluate the efficacy of a Moraxella bovis bacterin in the control of infectious bovine keratoconjunctivitis. The bacterin did not affect the incidence of infectious bovine keratoconjunctivitis in either trial but did appear to reduce the severity of lesions, treatments required and withdrawals from pasture required in one trial. Possible reasons for the apparently contradictory results are offered. It is suggested that the bacterin may be of some value when used in conjunction with other preventive measures. 相似文献
956.
D W Vogt M R Ellersieck W E Deutsch B Akremi M N Islam 《American journal of veterinary research》1986,47(1):188-191
Fourteen instances of meningocele-encephalocele in an experimental herd were recorded over a 5-year period. Thirteen of these affected animals were subjected to extensive pedigree analyses. Familial associations were strong, and clearly the meningocele-encephalocele in this herd was under genetic influence. However, additional studies are needed to clarify the mode of inheritance and, perhaps, to identify other factors that might be involved. 相似文献
957.
Poxvirus infections are common in domestic birds in Germany, but they are rare in birds of prey. Only species of falconidae imported from Arabian or Asian countries have so far tested positive for poxvirus, and, among these, only raptors kept for falconry. As part of a reintroduction programme in the northern county of Mecklenburg-Western Pomerania, which is adjacent to the Baltic Sea, 21 young peregrine falcons were released into the wild; six of them died and one was examined postmortem, its tissues being examined by light and electron microscopy. In addition, an ELISA for fowlpox, pigeonpox and canarypox was applied. No virus could be isolated and propagation in culture failed, but virus particles were detected by electron microscopy in lesions from its skin and tongue. 相似文献
958.
Burkholder WJ Lees GE LeBlanc AK Slater MR Bauer JE Kashtan CE McCracken BA Hannah SS 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2004,18(2):165-175
Young adult heterozygous (carrier) female dogs with X-linked hereditary nephropathy (XLHN) have glomerular proteinuria but are otherwise healthy. Because data regarding dietary influences on the magnitude of proteinuria in dogs with spontaneous glomerular disease are not available, 12 such dogs were studied in a double crossover experiment intended to determine effects of altering dietary protein intake for up to 6 weeks. Dogs were blocked by urine protein : creatinine ratio (UPC) and randomly assigned to receive 2 diets: high protein (34.6% dry matter [DM], HP) or low protein (14.1% DM, LP) fed in HP-LP-HP or LP-HP-LP sequence. Food intake was measured daily, body weight (BW) was measured twice weekly, and UPC, plasma creatinine, blood urea nitrogen, phosphorus, albumin, and protein concentrations were measured at 2-week intervals. Nutrient digestibility was measured during the third treatment period. Diet had a significant effect (P < .0001) on all measured variables except plasma phosphorus (P > .5), but unintended differences in digestibility of protein and energy (P < or = .01) prevented assignment of the diet effect exclusively to protein. Proteinuria was greater (UPC 4.7 +/- 2.2 versus 1.8 +/- 1.1, P < .0001) when the HP diet was fed, but the LP diet did not maintain starting BW or plasma albumin concentration within the normal reference range. Diet greatly affects the magnitude of proteinuria in XLHN carrier females. Dietary protein restriction can reduce proteinuria in dogs with glomerular disease, but BW and blood protein concentrations may not be maintained if the restriction is too severe. 相似文献
959.
Effects of spray-dried animal plasma (SDAP) on intake and apparent digestibility of major dietary components were determined using 22 adult Beagles. Trials 1 and 2 used six and eight dogs, respectively, in a switchback design using 10-d periods. Trial 3 used eight dogs in a replicated 4 x 4 Latin square design with 15-d periods. The final 5 d of each period were used for measurement of intake and fecal collections. In Trial 1, dry extruded dog food kibbles were coated with 5% tallow, 2% commercial flavor, and 0 or 2% SDAP (as-fed basis). In Trial 2, commercially available dry dog food, previously coated with fat and flavor were coated with 0 or 2% SDAP. In Trial 3, SDAP (0, 1, 2, or 3%) was blended with other ingredients and extruded (as-fed basis). Kibbles were subsequently coated with 5% poultry fat and 1% commercial flavor. Intake, fecal consistency, and apparent digestibility of nutrients were determined. Addition of SDAP did not markedly affect chemical composition of diets and did not affect intake. Digestibility of DM was improved (P < 0.04) an average of 3.2% when 2% SDAP was included in the diet for all trials. Organic matter digestibility was improved (P < 0.01) in Trials 2 and 3 by an average of 2.9%. Also, digestibility of crude fiber (Trials 1 and 2) or total dietary fiber (Trial 3) was increased with addition of SDAP to the diet (P < 0.01). Fecal DM excretion was decreased by an average of 15% across all trials with the addition of SDAP. Spray-dried animal plasma was an acceptable ingredient in dry dog food preparations, resulting in improved digestion and decreased fecal output. Changes in digestion that occurred with addition of SDAP suggested alteration in digestive capacity in dogs. 相似文献
960.
Cornelisse CJ Robinson NE Berney CE Kobe CA Boruta DT Derksen FJ 《Equine veterinary journal》2004,36(5):426-430
REASONS FOR PERFORMING STUDY: Although the efficacy of dexamethasone for the treatment of recurrent airway obstruction (RAO) has been documented, the speed of onset of effect and duration of action are unknown, as is the efficacy of orally administered dexamethasone with or without fasting. OBJECTIVES: To document the time of onset of effect and duration of action of a dexamethasone solution i.v. or orally with and without fasting. METHODS: Protocol 1 used 8 RAO-affected horses with airway obstruction in a crossover design experiment that compared the effect of i.v. saline and dexamethasone (0.1 mg/kg bwt) on pulmonary function over 4 h. Protocol 2 used 6 similar horses to compare, in a crossover design, the effects of dexamethasone i.v. (0.1 mg/kg bwt), dexamethasone per os (0.164 mg/kg bwt) with and without prior fasting, and dexamethasone per os (0.082 mg/kg) with fasting. RESULTS: Dexamethasone i.v. caused significant improvement in lung function within 2 h with a peak effect at 4-6 h. Dexamethasone per os was effective within 6 h with peak effect at 24 h at a dose of 0.164 mg/kg bwt prior to feeding. The duration of effect was, for all dexamethasone treatments, statistically significant for 30 h when compared to saline and tended to have a longer duration of effect when used orally. Dexamethasone per os at a dose of 0.164 mg/kg bwt to fed horses had mean effects comparable to dexamethasone at a dose of 0.082 mg/kg bwt per os given to fasted horses, indicating that feeding decreases bioavailability. CONCLUSIONS: Dexamethasone administered i.v. has a rapid onset of action in RAO-affected horses. Oral administration of a bioequivalent dose of the same solution to fasted horses is as effective as i.v. administration and tends to have longer duration of action. Fasting horses before oral administration of dexamethasone improves the efficacy of treatment. POTENTIAL RELEVANCE: Oral administration to fasted horses of a dexamethasone solution intended for i.v. use provides an effective treatment for RAO-affected animals. 相似文献