全文获取类型
收费全文 | 18693篇 |
免费 | 1085篇 |
国内免费 | 701篇 |
专业分类
林业 | 4222篇 |
农学 | 620篇 |
基础科学 | 1310篇 |
2365篇 | |
综合类 | 7262篇 |
农作物 | 715篇 |
水产渔业 | 1071篇 |
畜牧兽医 | 1284篇 |
园艺 | 338篇 |
植物保护 | 1292篇 |
出版年
2024年 | 101篇 |
2023年 | 312篇 |
2022年 | 353篇 |
2021年 | 527篇 |
2020年 | 593篇 |
2019年 | 667篇 |
2018年 | 433篇 |
2017年 | 555篇 |
2016年 | 697篇 |
2015年 | 591篇 |
2014年 | 1031篇 |
2013年 | 1196篇 |
2012年 | 1542篇 |
2011年 | 1554篇 |
2010年 | 1174篇 |
2009年 | 1239篇 |
2008年 | 1120篇 |
2007年 | 1152篇 |
2006年 | 957篇 |
2005年 | 904篇 |
2004年 | 711篇 |
2003年 | 607篇 |
2002年 | 447篇 |
2001年 | 420篇 |
2000年 | 344篇 |
1999年 | 238篇 |
1998年 | 180篇 |
1997年 | 167篇 |
1996年 | 136篇 |
1995年 | 110篇 |
1994年 | 80篇 |
1993年 | 67篇 |
1992年 | 70篇 |
1991年 | 66篇 |
1990年 | 36篇 |
1989年 | 49篇 |
1988年 | 31篇 |
1987年 | 13篇 |
1986年 | 5篇 |
1985年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
高速公路边坡防护体系的建植养护 总被引:1,自引:0,他引:1
在对广东省普惠高速公路边坡生物防治体系——护坡草皮的建植和养护过程中,就草种选择、建植方式和质量监控等问题进行了讨论并提出建议,旨在提高我国高速公路边坡防护体系草皮的建植和养护水平。 相似文献
92.
犊牛阶段的生长发育状况对成年后生产性能的发挥具有极为重要的影响,所以犊牛的饲养管理非常关键。水是犊牛维持基础营养代谢和健康生长的重要营养元素,但是与代乳粉和开食料等日粮相比,容易被牧场忽视。本文分析了犊牛饮水的重要性及需水量与采食量的关系,讨论了犊牛饮水管理中的关键点,为加强犊牛饮水管理,提高犊牛阶段的培育管理水平提供指导。 相似文献
93.
饲料行业作为国民经济发展中的重要一环,对解决就业、促进区域经济增长、推动产业结构优化调整等起到重要作用.回顾饲料行业的发展历程,由于过去饲料行业门槛较低且呈现明显的地域分布规律,以家族管理模式创立的饲料企业数量较多.家族化管理一定程度上提升了企业的凝聚性,且具有执行效率高、管理成本低等优势.但随着行业竞争的进一步加剧,... 相似文献
94.
95.
96.
《Strength and Conditioning Journal》2020,73(3):420-432
One of the primary conservation threats surrounding sagebrush (Artemisia spp.) ecosystems in the Intermountain West of the United States is the expansion and infilling of pinyon pine (Pinus edulis, P. monophylla) and juniper (Juniperus spp.) woodlands. Woodland expansion into sagebrush ecosystems has demonstrated impacts on sagebrush-associated flora and fauna, particularly the greater sage-grouse (Centrocercus urophasianus). These impacts have prompted government agencies, land managers, and landowners to ramp up pinyon-juniper removal efforts to maintain and restore sagebrush ecosystems. Accurately quantifying and analyzing management activities over time across broad spatial extents still poses a major challenge. Such information is vital to broad-scale planning and coordination of management efforts. To address this problem and aid future management planning, we applied a remote sensing change detection approach to map reductions in pinyon-juniper cover across the sage-grouse range and developed a method for rapidly updating maps of canopy cover. We found total conifer reduction over the past several yr (2011−2013 to 2015−2017) amounted to 1.6% of the area supporting tree cover within our study area, which is likely just keeping pace with estimates of expansion. Two-thirds of conifer reduction was attributed to active management (1.04% of the treed area) while wildfire accounted for one-third of all estimated conifer reduction in the region (0.56% of the treed area). Our results also illustrate the breadth of this management effort—crossing ownership, agency, and state boundaries. We conclude by identifying some key priorities that should be considered in future conifer management efforts based on our comprehensive assessment. 相似文献
97.
草地土壤肥力及其营养管理的必要性 总被引:3,自引:0,他引:3
介绍了草地土壤肥力的来源,土壤基本养分对草地生产的作用,草地植物与动物对养分的需求量及缺乏症状,说明了加强草地营养管理以及维持草地生态系统营养平衡的重要性,指出增强对土壤肥力和营养管理是提高草地生产能力、保证草地生态系统平衡、保障草地可持续利用的关键技术措施。 相似文献
98.
2017年9月,甘肃省凉州区农牧局在日常检查时,查处一公司经营的饲料产品涉嫌非法添加其他物质。经立案调查,认定该公司经营的四黄止痢颗粒、抗病毒消炎颗粒、参芪增免颗粒、感冒神奇颗粒中擅自添加国务院农业行政主管部门公布的饲料添加剂品种目录和药物性饲料添加剂品种目录以外物质的违法事实确实,根据《饲料和饲料添加剂管理条例》规定,依法给予了行政处罚。本文通过对案件定性、查处过程及行业规范监管策略进行讨论,提出了多视角案件定性、先行追溯核查生产企业、陈述申辩与申请听证的不同处理和规范企业生产行为的监管举措。为切实规范兽药饲料经营秩序,强化饲料及饲料添加剂生产企业监管提供参考。 相似文献
99.
100.
Zhaolong CHENG Yongtao LI Matthew Keith PINE Tao ZUO Mingxiang NIU Jun WANG 《Integrative zoology》2023,18(1):169-182
The associations between feeding activities and environmental variables inform animal feeding tactics that maximize energetic gains by minimizing energy costs while maximizing feeding success. Relevant studies in aquatic animals, particularly marine mammals, are scarce due to difficulties in the observation of feeding behaviors in aquatic environments. This data scarcity concurrently hinders ecosystem-based fishery management in the context of small toothed-cetacean conservation. In the present study, a passive acoustic monitoring station was deployed in an East Asian finless porpoise habitat in Laizhou Bay to investigate potential relationships between East Asian finless porpoises and their prey. The data revealed that porpoises were acoustically present nearly every day during the survey period. Porpoise detection rates differed between spring and autumn in concert with activities of fish choruses. During spring, fish choruses were present throughout the afternoon, and this was the time when porpoise vocalizations were the most frequently detected. During autumn, when fish choruses were absent, porpoise detection rates decreased, and diurnal patterns were not detected. The close association between fish choruses and finless porpoise activities implies an “eavesdropping” feeding strategy to maximize energetic gains, similar to other toothed cetaceans that are known to engage similar feeding strategies. Underwater noise pollution, particularly those masking fish choruses, could interrupt finless porpoises’ feeding success. Fisheries competing soniferous fishes with finless porpoise could impact finless porpoise viability through ecosystem disruption, in addition to fishing gear entanglement. 相似文献