全文获取类型
收费全文 | 1068991篇 |
免费 | 61720篇 |
国内免费 | 56123篇 |
专业分类
林业 | 86451篇 |
农学 | 70473篇 |
基础科学 | 46733篇 |
143588篇 | |
综合类 | 329471篇 |
农作物 | 58168篇 |
水产渔业 | 51971篇 |
畜牧兽医 | 288712篇 |
园艺 | 49773篇 |
植物保护 | 61494篇 |
出版年
2023年 | 11203篇 |
2022年 | 25779篇 |
2021年 | 30853篇 |
2020年 | 29160篇 |
2019年 | 27537篇 |
2018年 | 24918篇 |
2017年 | 36179篇 |
2016年 | 27489篇 |
2015年 | 32709篇 |
2014年 | 39339篇 |
2013年 | 58807篇 |
2012年 | 69381篇 |
2011年 | 73670篇 |
2010年 | 66944篇 |
2009年 | 61654篇 |
2008年 | 67064篇 |
2007年 | 63773篇 |
2006年 | 56466篇 |
2005年 | 47968篇 |
2004年 | 32183篇 |
2003年 | 25159篇 |
2002年 | 23637篇 |
2001年 | 22844篇 |
2000年 | 23376篇 |
1999年 | 16395篇 |
1998年 | 8035篇 |
1997年 | 7089篇 |
1996年 | 7839篇 |
1995年 | 8359篇 |
1994年 | 7612篇 |
1993年 | 5459篇 |
1992年 | 8265篇 |
1991年 | 8387篇 |
1990年 | 8140篇 |
1989年 | 7778篇 |
1988年 | 6974篇 |
1987年 | 6865篇 |
1986年 | 6820篇 |
1985年 | 6373篇 |
1984年 | 5361篇 |
1983年 | 4724篇 |
1979年 | 4612篇 |
1978年 | 3777篇 |
1975年 | 3300篇 |
1974年 | 4015篇 |
1973年 | 4073篇 |
1972年 | 3914篇 |
1971年 | 3630篇 |
1970年 | 3461篇 |
1969年 | 3237篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
993.
以新疆赛买提杏为试验原料,选用0.9 mg/L的24-表油菜素内酯(24-epibrassionolide,EBR)对杏果实进行10 min的浸泡处理,将处理后的果实取出晾干后贮藏在温度为4℃、相对湿度(RH)90%~95%的冷库中,以蒸馏水处理为对照,定期测定相关指标,研究24-表油菜素内酯处理对杏果实贮藏品质的影响。结果表明,24-表油菜素内酯处理可以延缓杏果实贮藏期间可溶性固形物、可滴定酸、叶绿素和抗坏血酸含量的下降,有效降低杏果实的自然发病率,并能有效延缓呼吸速率和失重率的上升。 相似文献
994.
995.
Wenwen Wang Yanfeng Bai Chunqian Jiang Haijun Yang 《Journal of Sustainable Forestry》2020,39(5):526-541
ABSTRACT An individual-tree basal area increment model was developed for masson pine based on 26276 observations of 13,138 trees in 987 sample plots from the 7th (2004), 8th (2009), and 9th (2014) Chinese National Forest Inventory in Hunan Province, South-central China. The model was built using a linear mixed-effects approach with sample plots included as random effects since the data have a hierarchical stochastic structure and biased estimates of the standard error of parameter estimates could be a consequence of applying ordinary least square (OLS) for regression. In addition, within-plot heteroscedasticity and autocorrelation were also considered. The final mixed-effects model was determined according to the Akaike information criterion (AIC), Bayesian information criterion (BIC), log-likelihood (Loglik), and the likelihoodratio test (LRT). The results revealed that initial diameter (DBH), the sum of the basal area (m2/ha) in trees with DBHs larger than the DBH of the subject tree (BAL), number of trees per hectare (NT), and elevation (EL) had a significant impact on individual-tree basal area increment. The mixed-effects model performed much better than the basic model produced using OLS. Additionally, the variance structure of the model errors was successfully modeled using the power function. However, the autocorrelation structures were not defined because there was no autocorrelation amongst the data. It is believed that the final model will contribute to the scientific management of the masson pine. 相似文献
996.
Sabyasachi Banerjee Seema Singh Shailesh Pandey Maneesh S. Bhandari Amit Pandey Krishna Giri 《Forest Pathology》2020,50(2)
Wilt disease caused by Fusarium solani is a serious constraint to Dalbergia sissoo (shisham) plantations in northern India. In this study, the antagonistic potential of 40 bacterial isolates recovered from rhizophere soil of healthy shisham trees, and a well‐characterized Trichoderma species (Trichoderma virens) were tested for their possibility as biocontrol agents for F. solani. Two promising isolates (S1 and S15) were identified which inhibited pathogen growth, caused chitin degradation, produced siderophores and solubilized phosphate in vitro. Isolate S15 scored highest for hydrogen cyanide (HCN) production while isolate S1 was a non‐HCN producer. These two isolates were identified as Serratia marcescens (S1) and Pseudomonas azotoformans (S15) following sequence analysis of 16S rDNA. In dual culture assays, T. virens caused 80% inhibition of mycelial growth of the test fungus. The three selected antagonists when tested in planta in the glasshouse completely suppressed production of wilt symptoms on 12‐month‐old shisham plants. Further work is needed to ascertain the potential of these isolates to be used as biocontrol agents to manage shisham wilt under field conditions. 相似文献
997.
998.
999.
云南怒江傈僳族自治州古树名木资源现状调查 总被引:1,自引:0,他引:1
对怒江傈僳族自治州人为活动区域古树名木资源现状进行调查。结果表明:共记录到古树名木496株,涉及36科54属76种,其中有8种国家重点保护野生植物,分别为澜沧黄杉、秃杉、南方红豆杉、云南榧树、千果榄仁、红椿、光叶珙桐和香果树;怒江州古树名木主要分布在乡村街道及远郊野外,占总数的98.8%,63.6%的古树生长在海拔1500~1999 m;古树名木的生长环境及长势总体较好,但保护力度相对薄弱,应采取相关措施加强保护和管理。 相似文献
1000.
Analysing the agricultural sectors of Taiwan, Malaysia and Singapore, this paper examines the capability‐building process that encourages productivity and innovation. It describes and explains the origins and subsequent evolution of three forms of agricultural production system, each generating different farming capabilities and distinct forms of competitive advantages. The paper argues that Taiwan's rice‐oriented agricultural production system stimulates both productivity and innovation, helping Taiwanese farmers raise their income level and living standards. The active deployment of state institutions and a malleable labour force, evidenced in the Malaysian palm oil industry, is effective in raising farming productivity but not the ability to innovate. Singapore's aquaculture‐oriented agricultural production system is somewhat useful in stimulating productivity and innovation. Yet the city‐state's inherent lack of space and open international trade regime have circumscribed the potential of its aquaculture industry. It now relies on the regional ethnic Chinese business networks to expand the aquaculture industry's knowledge base and its industrial commons. The principles discussed in this paper provide policy lessons, or at least some initial guidance, for other developing economies aspiring to modernise their agricultural sector. 相似文献