全文获取类型
收费全文 | 1406篇 |
免费 | 79篇 |
国内免费 | 144篇 |
专业分类
林业 | 164篇 |
农学 | 182篇 |
基础科学 | 79篇 |
230篇 | |
综合类 | 369篇 |
农作物 | 84篇 |
水产渔业 | 80篇 |
畜牧兽医 | 324篇 |
园艺 | 33篇 |
植物保护 | 84篇 |
出版年
2024年 | 5篇 |
2023年 | 11篇 |
2022年 | 37篇 |
2021年 | 51篇 |
2020年 | 57篇 |
2019年 | 52篇 |
2018年 | 37篇 |
2017年 | 58篇 |
2016年 | 65篇 |
2015年 | 53篇 |
2014年 | 61篇 |
2013年 | 86篇 |
2012年 | 83篇 |
2011年 | 95篇 |
2010年 | 74篇 |
2009年 | 79篇 |
2008年 | 100篇 |
2007年 | 75篇 |
2006年 | 69篇 |
2005年 | 65篇 |
2004年 | 26篇 |
2003年 | 34篇 |
2002年 | 27篇 |
2001年 | 26篇 |
2000年 | 35篇 |
1999年 | 35篇 |
1998年 | 39篇 |
1997年 | 18篇 |
1996年 | 25篇 |
1995年 | 25篇 |
1994年 | 25篇 |
1993年 | 26篇 |
1992年 | 18篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1962年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有1629条查询结果,搜索用时 25 毫秒
71.
随着人们生活水平的不断提高,与此相应地对城镇街道绿化景观也提出了越来越高的要求。城镇街道绿化景观不仅是城市生态景观的重要组成部分之一,更是一个城市改善居民居住环境的重要途径。它不仅改善了城市环境,美化了城市形象,更能够彰显城市的文化内涵,对整个城市宜居水平产生着极其重要的影响。没有良好的城镇街道绿化景观,就没有良好的城市生态环境。基于此,试图就城镇街道绿化景观设计展开初步探讨研究,以供参考借鉴。 相似文献
72.
为探究澳洲坚果(Macadamia integrifolia)对土壤铅胁迫的耐受性,以3年生澳洲坚果实生苗为材料,研究不同浓度铅处理下(0、200、400、800、1 200、1 600和2 000 mg/kg)澳洲坚果幼苗生长及生理特性的变化。结果表明,除地径增量和可溶性糖含量外,铅浓度对澳洲坚果幼苗生长及生理特性均影响极显著。随铅浓度升高,幼苗株高和地径增量、叶绿素含量、可溶性蛋白和游离脯氨酸含量及SOD和POD活性均呈先升后降的趋势;可溶性糖含量呈先降后升的趋势;MDA含量逐渐上升。澳洲坚果幼苗对1 200 mg/kg以下的铅胁迫有一定抗性;1 200 mg/kg以上会对其造成毒害,抑制其生长。 相似文献
73.
74.
Effect of LED light quality on the phototaxis and locomotion behaviour of Haliotis discus hannai 下载免费PDF全文
Xiaolong Gao Mo Zhang Jimeng Zheng Xian Li Liang Chi Changbin Song Ying Liu 《Aquaculture Research》2016,47(11):3376-3389
Abalones were reared in a laboratory to determine the percentage response rate, response time, average crawling speed and the time taken to recover an upright posture under nine light‐emitting diode light quality treatments (red, orange, yellow, green, cyan, blue, purple, white and grey) and a dark environment. Animals were placed in the centre of an experimental device, and the tropism of each animal was continuously monitored by video. The highest percentage response rate (80% in dark adapted abalones, 60% in light adapted abalones) was observed in the dark environment, followed by red and orange light (27% and 30% in dark adapted abalones, respectively, 22% and 24% in light adapted abalones). Two induction materials (substrate and brown algae Laminaria japonica) were used to assess the effect of light quality on the tropism of abalones, with the highest percentage response rate (76% in the L. japonica treatment, 22% in the substrate treatment) also observed in the dark environment, followed by red and orange light (both 25% in the L. japonica treatment, and 26% and 32%, respectively, in the substrate treatment). The tropism order of the abalones under dark, red, orange and yellow light was as follows: dark > orange > red, yellow, but fewer abalones chose to stay in blue, green, cyan and purple light. The response time (about 700 s) in the dark environment was significantly longer than for the other light quality treatments. Compared with the average crawling speed in the other light quality treatments, abalones were relatively slower (about 3.8 mm s?1) in red and orange light, and the dark environment. The mean time required for the recovery of an upright posture in red light and the dark environment was longer than in the other light quality treatments, with the average recovery time reaching a maximum of 60 s in the dark environment. The results demonstrate the phototaxis and locomotion behaviour of abalones, as well as confirming the necessity of a dark, orange or red environment for their management and aquaculture. 相似文献
75.
76.
77.
对广东省鹤山和东莞莲花山自然保护区的小蛾类昆虫进行调查,计有8科35属43种。其中广东新记录种14种。 相似文献
78.
SUMMARY Clinical signs of proliferative haemorrhagic enteropathy (PHE) including anaemia, dysentery and sudden death were observed in finisher pigs and young breeding stock on 2 farms. On farm A, PHE occurred 12 months after repopulation of the farm. Other outbreaks of PHE occurred after the withdrawal of therapeutic concentrations of in-feed antibacterial agents (farm A), or after monensin sodium (100 g/t) replaced olaquindox (100 g/t) in feed (farm B). The outbreaks, the possible sources of contamination and the role of antibacterial feed additives in the treatment and control of PHE are described. 相似文献
79.
80.
A total of 2053 import and 164 export samples from 425 production plants were examined over a 9-year period (1992-2000) for the presence of Listeria monocytogenes (L. monocytogenes) in Switzerland. Overall, 282 samples (12.2%) and 85 plants (20.5%) harbored the pathogen. The highest isolation risk was for marinated fish (38%); the lowest was in cured- and dried-meat products.Unconditional fixed-effect logistic regression was used to identify the main hazards associated with the presence of L. monocytogenes. The plant-level model considered potential risk factors for a positive culture operating at the production-plant level by including a random effect of plant and year.Food category was the only significant factor; sampling site, country of origin and season were not significant. Marinated fish was a strong predictor for positive culture, whereas cooked- and cured-meat products were protective. Plant and year effects were significant. Control measures should be focused on specific food items in each production plant. 相似文献