全文获取类型
收费全文 | 21327篇 |
免费 | 1411篇 |
国内免费 | 803篇 |
专业分类
林业 | 4705篇 |
农学 | 829篇 |
基础科学 | 1584篇 |
2549篇 | |
综合类 | 8561篇 |
农作物 | 855篇 |
水产渔业 | 1131篇 |
畜牧兽医 | 1545篇 |
园艺 | 365篇 |
植物保护 | 1417篇 |
出版年
2024年 | 41篇 |
2023年 | 327篇 |
2022年 | 439篇 |
2021年 | 588篇 |
2020年 | 709篇 |
2019年 | 753篇 |
2018年 | 486篇 |
2017年 | 623篇 |
2016年 | 802篇 |
2015年 | 699篇 |
2014年 | 1148篇 |
2013年 | 1344篇 |
2012年 | 1771篇 |
2011年 | 1803篇 |
2010年 | 1377篇 |
2009年 | 1470篇 |
2008年 | 1309篇 |
2007年 | 1361篇 |
2006年 | 1151篇 |
2005年 | 1053篇 |
2004年 | 819篇 |
2003年 | 719篇 |
2002年 | 519篇 |
2001年 | 479篇 |
2000年 | 379篇 |
1999年 | 253篇 |
1998年 | 205篇 |
1997年 | 175篇 |
1996年 | 154篇 |
1995年 | 129篇 |
1994年 | 89篇 |
1993年 | 73篇 |
1992年 | 76篇 |
1991年 | 72篇 |
1990年 | 36篇 |
1989年 | 46篇 |
1988年 | 33篇 |
1987年 | 20篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1963年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
中小型饲料企业是饲料产品经济发展中的重要组成部分,也是我国农牧行业经济发展的重要组成部分。随着计算机物联网技术的不断发展,当前线上销售模式应成为中小型饲料企业创新经济增长点的重点发展领域,而要想更好的发展线上运营模式必须考虑当前中小型饲料企业自身供应链管理物流配送的发展状况。本文研究分析当前中小型饲料企业供应链管理及物流配送的发展现状,通过对供应链管理的核心影响因素及中小型饲料企业所处内外部环境的深入研究,分析当前中小型饲料企业供应链管理发展问题背后的原因,并在此基础上提出针对中小型饲料企业供应链管理与物流配送的合理性建议与优化措施。
[关键词]中小型饲料企业|供应链管理|优化措施 相似文献
102.
103.
104.
M M HASOBA Ahmed 《干旱区科学》2020,12(4):609-617
Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots (1000 m2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height (DBH) ≥5.00 cm were identified and counted, and their DBH values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species (Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities. 相似文献
105.
Justice A. Tambo Roger K. Day Julien Lamontagne-Godwin Silvia Silvestri Patrick K. Beseh Birgitta Oppong-Mensah 《国际虫害防治杂志》2020,66(4):298-310
AbstractSince its emergence in Africa in 2016, fall armyworm (FAW) has spread rapidly and poses a severe threat to the food security and livelihood of millions of smallholder farmers in the continent. Using survey data from Ghana and Zambia, we examined FAW prevention and control methods implemented by farm households and their impacts on maize output and household consumption of self-produced maize. The main control methods used included pesticide application and handpicking of larvae, while access to information on FAW was a key driver behind the implementation of the control methods. Results from an endogenous switching regression showed that the implementation of a FAW management strategy significantly enhanced maize yield and households’ own maize consumption. When disentangling the impacts of the main control methods, we found that the combination of pesticide application and handpicking of larvae produced the highest yield gain of 125%. We concluded that the current interventions put in place by farmers to tackle FAW infestations are providing positive outcomes, but successful management of the pest will require more actions, including raising awareness to enhance the adoption of control interventions and exploring other control options. 相似文献
106.
107.
108.
109.
110.