全文获取类型
收费全文 | 711篇 |
免费 | 34篇 |
国内免费 | 5篇 |
专业分类
林业 | 60篇 |
农学 | 29篇 |
基础科学 | 6篇 |
109篇 | |
综合类 | 93篇 |
农作物 | 42篇 |
水产渔业 | 51篇 |
畜牧兽医 | 248篇 |
园艺 | 63篇 |
植物保护 | 49篇 |
出版年
2023年 | 17篇 |
2022年 | 21篇 |
2021年 | 32篇 |
2020年 | 24篇 |
2019年 | 39篇 |
2018年 | 31篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 18篇 |
2014年 | 29篇 |
2013年 | 36篇 |
2012年 | 51篇 |
2011年 | 60篇 |
2010年 | 37篇 |
2009年 | 28篇 |
2008年 | 31篇 |
2007年 | 30篇 |
2006年 | 27篇 |
2005年 | 25篇 |
2004年 | 24篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1992年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1960年 | 1篇 |
1950年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有750条查询结果,搜索用时 15 毫秒
91.
Festus Otaka Abonyi Ndubuisi Samuel Machebe Michael Sunday Ezea James I. Eze Benjamin Chigozie Omeke Benjamin Nwabueze Marire 《Tropical animal health and production》2013,45(4):957-963
Twenty-four Large White × Landrace crossbreed primigravid pigs, aged 7.50 to 8.00 months weighing between 86.15 and 88.24 kg were used to study the effects of feeding graded levels of soya bean meal (SBM) replaced blood meal (BM) diets on serum biochemical profile in gestating pigs. The pigs were randomly allotted to four finisher diets formulated such that BM replaced SBM at 0.0, 50.0, 75.0 and 100.0 %, respectively. The diets were T1 (100.0 % SBM, 0.0 % BM), T2 (50.0 % SBM, 50.0 % BM), T3 (25.0 % SBM, 75.0 % BM) and T4 (0.0 % SBM, 100.0 % BM). Individual animal’s daily ration of the test diets was 2.20, 2.00 and 2.50 kg at stages one, two and three of gestation. Blood sampling and analysis for the effects of the test diets on biochemical profile of the experimental animals were carried out prior to conception, at weeks 3, 7 and 11 of gestation, respectively. The result showed no significant (P?≥?0.05) dietary treatment effects on total protein, albumin, globulin fraction, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatinine and urea profile of the pigs fed with BM diets when compared to the control fed with 100.0 % SBM. There was however a significant (P?≤?0.05) variation in these biochemical indices in all the experimental groups at different stages of gestation. It was concluded that BM can replace 100.0 % of SBM in the diets of pregnant pigs in the tropical humid environment without any deleterious effect on their health. 相似文献
92.
Samuel P. Franklin James. L. Cook 《The Canadian veterinary journal. La revue veterinaire canadienne》2013,54(9):881-884
This prospective, randomized, double-blinded trial compared outcomes in dogs with bilateral elbow osteoarthritis (OA) treated with hyaluronan plus methylprednisolone (HA + S) or autologous conditioned plasma (ACP®; Arthrex). An investigator blinded to the treatments graded lameness (0–4) before and 6 months after a single injection with either HA + S or ACP. Clients were blinded to treatment and completed a validated survey before and 1, 6, 12, and 24 weeks after injection. Ten dogs (5 per group) completed all parts of the study. Pre-treatment lameness grades were 1.2 ± 0.97 for HA + S and 1.8 ± 1.1 for ACP and were not different between groups. Post-treatment lameness grades were 0.4 ± 0.55 for HA + S and 0.8 ± 0.64 for ACP with significant (P < 0.05) improvement with either treatment but without differences between groups. Client-based assessments demonstrated improvements in activity, lameness, and pain with HA + S and ACP. These data suggest that both treatments have beneficial effects for dogs with bilateral elbow OA. 相似文献
93.
94.
Penman-Monteith模型模拟Venlo型温室黄瓜植株蒸腾 总被引:2,自引:2,他引:0
准确模拟温室作物蒸腾对于制定科学合理的灌溉制度及温室环境调控具有重要意义,该研究基于2017年秋冬季和2018年春夏季Venlo型温室黄瓜生育期内微气象数据、黄瓜生长发育指标和植株蒸腾,对Penman-Monteith(PM)模型中关键参数—冠层阻力和空气动力学阻力进行研究。通过分析黄瓜叶片孔阻力与温室内气象因子的响应关系,构建了由黄瓜有效叶面积指数及叶片孔阻力模拟冠层阻力的子模型;采用基于风速的Perrier对数法和基于温室对流类型的热传输系数法计算温室内低风速环境下的空气动力学阻力,并评价不同方法的适用性。结果表明:叶片孔阻力与太阳辐射呈指数关系(R~2=0.89),可通过观测温室内太阳辐射计算黄瓜叶片孔阻力;应用热传输系数法确定空气动力学阻力时,温室内对流类型绝大多数时间为混合对流;2种方法计算的温室内空气动力学阻力变化幅度均较小,Perrier对数法计算的春夏季和秋冬季空气动力学阻力平均值分别为388和383 s/m,热传输系数法计算的空气动力学阻力平均值分别为141和158 s/m;基于2种空气动力学阻力计算方法,PM模型模拟的植株蒸腾与实测值均具有较好的一致性,但采用Perrier对数法计算空气动力学阻力时,PM模型低估了植株蒸腾,春夏季和秋冬季拟合线斜率分别为0.87和0.91;而采用热传输系数法计算空气动力学阻力时,PM模型可更准确的模拟该地区温室黄瓜植株蒸腾,春夏季和秋冬季拟合线斜率分别为1.00和0.94,R~2分别为0.91和0.95,均方根误差分别为46.15和12.45 W/m~2。该研究结果为实现PM模型在Venlo型温室环境的准确应用提供了参考。 相似文献
95.
96.
Aaron C. Rhodes Cecily Fitch Samuel B. St. Clair 《Strength and Conditioning Journal》2019,72(3):454-460
Aspen is a foundation species that provides vital habitat for hundreds of plant and animal species. However, changing ungulate herbivory regimes may be altering recruitment success and resilience of aspen forests. The objective of this observational study was to quantify the impacts of ungulate herbivory on aspen recruitment potential. We sampled 36 aspen dominant stands on the Fishlake National Forest in Utah for browse of apical meristems, suckering density (< 180 cm in height), and recruitment density (≥ 180 cm). Our analysis indicated that for each 10% of apical meristems browsed, annual vertical and radial growth rates and recruitment density were reduced by 1.2 cm, 0.02 mm, and 17 ha? 1, respectively. In contrast, aspen suckering density increased by 1 230 suckers ha? 1, with each 10% browse of apical meristems. This suggests that ungulates contribute to aspen suckers persisting in the understory for longer periods and may alter recruitment success of aspen stands. Aspen that were under high ungulate browse pressure were associated with lower growth rates and persisted for twice as long in the understory. For example, a 5-yr-old sucker was predicted to be 115 cm without browse of apical meristems and 60 cm with 100% browse of apical meristems. Further, aspens of the same height with 100% browse of apical meristems were nearly 4 yr older on average than aspens with no evidence of browse of apical meristems. Approximately 34% of aspen suckers had persisted in the understory < 100 cm for ≥ 6 yr, and 7% of suckers had persisted in the understory for ≥ 10 yr. Our results suggest that high rates of meristem removal are correlated with increased aspen suckering yet reduced aspen growth and recruitment. 相似文献
97.
Cameron A. Duquette Craig A. Davis Samuel D. Fuhlendorf R. Dwayne Elmore 《Strength and Conditioning Journal》2019,72(3):484-491
Despite the fact that the northern bobwhite (Colinus virginianus Linnaeus; hereafter, bobwhite) is one of the most well-studied and widely distributed wildlife species in North America, we know little about how bobwhite respond to oil and gas infrastructure. We investigated the impacts of oil and gas development on space use of bobwhite using a multiseason approach. We captured and monitored bobwhite in the breeding season (1 April–30 September, n = 135 individuals) and nonbreeding season (1 October–31 March, n = 30 coveys) and modeled their habitat selection in a resource-utilization function (third order, within home range selection) and resource-selection function (second order, home range selection) format. Generally, energy infrastructure effects on bobwhite were neutral, but breeding season bobwhite did select for areas near low-traffic roads (β = ? 0.31 ± 0.15 SE). In the nonbreeding season, coveys selected for areas within their home range with a limited viewshed (i.e., areas with limited visibility of anthropogenic structures; β = ? 0.03 ± 0.02 SE). Selection differed between sexes for well pads (t = ? 2.12, P = 0.04) but was otherwise similar. At the level of home range selection, bobwhite exhibited a preference for areas with a low density of oil and gas wells and a high density of low-traffic roads during both the breeding and nonbreeding seasons (breeding: βwell = ? 0.14 ± 0.02, βroad = 0.26 ± 0.27; nonbreeding: βwell = ? 0.08 ± 0.03, βroad = 0.16 ± 0.03). As a generalist species, bobwhite appear to be largely tolerant of energy infrastructure and associated disturbances at moderate levels of development but may be sensitive to high densities of oil and gas pads. 相似文献
98.
Clinical features of canine pulmonary veno‐occlusive disease and pulmonary capillary hemangiomatosis
99.
100.
Balaro Mario Felipe A. de Mello Samuel Guaraná Valverde da Silva Santos Alex Cavalcanti Luiza Mattos Almosny Nádia Regina Pereira Fonseca Jeferson F. Brandão Felipe Z. 《Tropical animal health and production》2019,51(2):345-353
Tropical Animal Health and Production - This study aimed to verify the reproductive seasonality in Saanen goats from distinct parity orders (nulliparous, primiparous, and pluriparous) throughout an... 相似文献