全文获取类型
| 收费全文 | 2387篇 |
| 免费 | 317篇 |
| 国内免费 | 43篇 |
专业分类
| 林业 | 139篇 |
| 农学 | 94篇 |
| 基础科学 | 49篇 |
| 278篇 | |
| 综合类 | 787篇 |
| 农作物 | 140篇 |
| 水产渔业 | 222篇 |
| 畜牧兽医 | 752篇 |
| 园艺 | 181篇 |
| 植物保护 | 105篇 |
出版年
| 2025年 | 10篇 |
| 2024年 | 54篇 |
| 2023年 | 55篇 |
| 2022年 | 70篇 |
| 2021年 | 87篇 |
| 2020年 | 82篇 |
| 2019年 | 83篇 |
| 2018年 | 64篇 |
| 2017年 | 79篇 |
| 2016年 | 64篇 |
| 2015年 | 82篇 |
| 2014年 | 102篇 |
| 2013年 | 159篇 |
| 2012年 | 118篇 |
| 2011年 | 145篇 |
| 2010年 | 131篇 |
| 2009年 | 139篇 |
| 2008年 | 140篇 |
| 2007年 | 167篇 |
| 2006年 | 99篇 |
| 2005年 | 94篇 |
| 2004年 | 63篇 |
| 2003年 | 39篇 |
| 2002年 | 64篇 |
| 2001年 | 54篇 |
| 2000年 | 59篇 |
| 1999年 | 41篇 |
| 1998年 | 17篇 |
| 1997年 | 17篇 |
| 1995年 | 13篇 |
| 1994年 | 11篇 |
| 1993年 | 14篇 |
| 1992年 | 22篇 |
| 1991年 | 16篇 |
| 1990年 | 17篇 |
| 1989年 | 17篇 |
| 1988年 | 16篇 |
| 1987年 | 12篇 |
| 1986年 | 11篇 |
| 1985年 | 19篇 |
| 1984年 | 10篇 |
| 1983年 | 11篇 |
| 1982年 | 10篇 |
| 1979年 | 12篇 |
| 1978年 | 10篇 |
| 1975年 | 14篇 |
| 1974年 | 12篇 |
| 1973年 | 10篇 |
| 1971年 | 11篇 |
| 1969年 | 12篇 |
排序方式： 共有2747条查询结果，搜索用时 15 毫秒
91.
Søren Saxmose Nielsen Anne Marie Michelsen Henrik Elvang Jensen Kristiane Barington Katharina Vester Opstrup Jens Frederik Agger 《Preventive veterinary medicine》2014
Skin lesions on pigs inflicted by humans compromise animal welfare and are the subject of increased public and political attention in Denmark. Systematic surveillance of such skin lesions was enforced in April 2010 at all Danish pig abattoirs, through the recording of meat inspection Code 904 for the presence of skin lesions suspected to be human inflicted. The objectives of the present study were to (a) estimate the apparent prevalence of Code 904s at the pig and herd owner level; (b) characterise the distribution of deliveries with pigs demonstrating a Code 904; (c) characterise the distribution of herd owners with repeated Code 904 recordings; and (d) determine the developments in Code 904 prevalence over time in Danish finishing pigs in the period from May 1, 2010 to September 30, 2013. 相似文献
92.
Alternate partial root-zone irrigation improves fertilizer-N use efficiency in tomatoes 总被引：1，自引：0，他引：1
Yaosheng Wang Fulai Liu Lars Stoumann Jensen Andreas de Neergaard Christian Richardt Jensen 《Irrigation Science》2013,31(4):589-598
The objective of this study was to investigate the comparative effects of alternative partial root-zone irrigation (PRI) and deficit irrigation (DI) on fertilizer-N use efficiency in tomato plants under mineral N and organic N fertilizations. The plants were grown in split-root pots in a climate-controlled glasshouse and were subjected to PRI and DI treatments during early fruiting stage. When analyzed across the N fertilizer treatments, PRI treatment led to significantly higher N yield, agronomic N use efficiency (ANUE), and apparent N recovery efficiency (ANRE) as compared with the DI treatment, indicating significantly higher fertilizer-N use efficiency and soil N availability as well as enhanced plant’s N acquisition ability in the PRI treatment. Analysis across the irrigation treatments showed that the mineral N fertilizer treatment (MinN) significantly increased N yield, ANUE and ANRE relative to the organic N fertilizer treatment (OrgN). Compared with DI, the rhizosphere and bulk soil mineral N content in the soil were significantly lowered in the PRI treatment, indicating the enhanced root N uptake efficiency. It is suggested that PRI-enhanced soil water dynamics may have increased soil nitrate mass/diffusive flow to the root surfaces and root N uptake efficiency in the wetting soil and stimulated soil N mineralization and plant N demand, contributing to the improved fertilizer-N use efficiency in the PRI relative to the DI treatment. 相似文献
93.
The effect of pre-weaning eating activity on the intestinal morphology in piglets was investigated on the day of weaning and 5 days post-weaning. The eating activity of each piglet was recorded by means of direct observations. On day 5 post-weaning the villous heights were reduced and the crypt depths were increased irrespective of the pre-weaning eating activity. In the caecum and colon the crypt depth was increased post-weaning and no effect of pre-weaning eating activity was observed. The muscle thickness in the small intestine did not change during the immediate post-weaning period whereas the muscle thickness in the large intestine was doubled in the same period. In conclusion, pre-weaning eating activity did not affect the structural alterations of the small and large intestine. However, the actual number of piglets consuming creep feed prior to weaning was low and the eating activity was highly variable. Therefore, more or later weaned piglets may be needed to show effects of pre-weaning eating activity. 相似文献
94.
Blair L. Waldron Troy J. Bingham J. Earl Creech Michael D. Peel Rhonda Miller Kevin B. Jensen Dale R. ZoBell Jong‐Su Eun Kevin Heaton Donald L. Snyder 《Grassland Science》2020,66(2):74-87
High nitrogen (N) fertilizer costs and increased environmental stewardship have renewed interest in grass–legume pastures. This research compared herbage mass, nutritive value, steer growth performance and economics of binary mixtures of tall fescue (Schendonorus arundinaceus [Schreb.] Dumort, nom. Cons.) (TF) with alfalfa (ALF) (TF + ALF, Medicago sativa L.) and birdsfoot trefoil (BFT) (TF + BFT, Lotus corniculatus L.), to tall fescue with (TF + N) and without N fertilizer (TF–N). Pastures were established in Lewiston, Utah, USA, and rotationally stocked by Angus beef steers for 112 days in 2012 and 2013. Herbage samples were collected prior to each 7‐day stocking period and analyzed for mass and nutritive value. Steers were weighed each 28‐day rotation cycle and cumulative average daily gain (ADG) calculated. Steer performance differed (p = .05) among most treatments with ADG greatest for TF + BFT (0.73 kg/day) and TF + ALF (0.67 kg/day), followed by TF + N (0.61 kg/day) and the least for TF–N (0.40 kg/day). Multivariate analysis indicated that small inherent differences in herbage energy, fiber and digestibility were highly correlated with steer growth. Other variables associated with ADG included legume proportion and herbage mass. Fescue–legume mixtures had 29 to 33% legume proportion, and more (p = .05) favorable energy and fiber concentrations than grass monocultures. Whereas herbage mass was greatest (p = .05) for TF + N (2,956 kg/ha), followed closely by TF + BFT (2,741 kg/ha) and TF + ALF (2,623 kg/ha). Overall, TF + BFT and TF + ALF pastures had less herbage, but better nutritive value and increased steer growth performance compared to TF + N, without the added cost of fertilizer. 相似文献
95.
[目的]探讨有机硅肥在热带设施甜瓜上的施用效果,为热带设施甜瓜合理使用有机硅肥提供实践依据.[方法]开展大棚试验,按喷施有机硅肥浓度水平组合设4个处理,分别为伸蔓期稀释倍数为1000倍,其他时期800倍(T1);伸蔓期稀释倍数为800倍,其他时期600倍(T2);伸蔓期稀释倍数为700倍,其他时期400倍(T3);伸蔓期稀释倍数为600倍,其他时期300倍(T4);以清水为对照(CK),研究不同浓度喷施对热带设施甜瓜生长发育、产量和品质的影响.[结果]喷施有机硅肥的T2、T3处理甜瓜株高显著高于其他处理(P＜0.05,下同);各处理甜瓜茎粗差异不显著(P＞0.05,下同);相比处理,喷施有机硅肥处理的甜瓜叶面积、叶片SPAD值和果实纵横径均显著增加,收获时间可提前1～2d;随着浓度的增加,产量呈增加趋势,较CK分别增产9.95％、23.70％、24.45％和26.20％.其中产量最高的处理为伸蔓期喷施600倍液,其他时期300倍液的处理(29.50 t/ha).[结论]喷施有机硅肥可提高甜瓜产量和品质,建议使用叶面喷施有机硅肥的稀释倍数为伸蔓期600倍、其他时期300倍. 相似文献
96.
A randomized, blocked 23 factorial experiment was conducted with 48 pigs from sows fed a diet low in selenium and vitamin E. From 3 to 12 weeks of age the piglets were kept in single pens and fed a basic diet consisting mostly of barley, dried skim milk, soybean meal and dried yeast, and containing 55 µg selenium and 3 mg vitamin E per kg. The treatment factors — i.e. feed supplements — were 2 levels of Se (nil, 60 µg/kg), 2 levels of vitamin E (nil, 50 mg/kg), and 2 levels of the feed antioxidant ethoxyquin (nil, 150 mg/kg). Blood samples, collected at termination of the experiment, were examined for glutathione peroxidase activity (GSH-Px) and resistance against erythrocyte lipid peroxidation (ELP) to evaluate Se and vitamin E status, respectively. Analysis of variance showed the GSH-Px activity to be litter-dependent (P < 0.001) and influenced by selenium supplementation (P < 0.001) but not by the other supplements or by interactions between supplements. Resistance against ELP was influenced only by vitamin E supplementation (P < 0.001). GSH-Px and ELP thus seem to be valuable and simple methods for evaluating, respectively, Se status and vitamin E status in growing pigs. 相似文献
97.
98.
目的观察Z-形钛合金钢板前路内固度定术对胸腰椎爆裂性骨折患者的临床疗效。方法对60例胸腰段脊柱爆裂性骨折患者进行前方减压、椎体间植骨、Z-形钛钢板内固定,术后卧床3周,3周后戴支架起床活动。结果随访平均12.5个月,术后CT或MR显示椎管内压迫去除,植骨愈合。脊柱后凸Cobb角较术前改善12.7°,无继发脊柱后凸畸形。神经功能较术前有1~2级以上的改善。结论Z-形钛合金钢板前路内固定术对胸腰椎爆裂性骨折减压彻底,固定牢固,不破坏后稳定结构,并能一期重建脊柱系列。 相似文献
99.
100.