全文获取类型
收费全文 | 11590篇 |
免费 | 3556篇 |
国内免费 | 4篇 |
专业分类
林业 | 433篇 |
农学 | 648篇 |
基础科学 | 10篇 |
2273篇 | |
综合类 | 643篇 |
农作物 | 684篇 |
水产渔业 | 2832篇 |
畜牧兽医 | 6001篇 |
园艺 | 82篇 |
植物保护 | 1544篇 |
出版年
2023年 | 42篇 |
2022年 | 96篇 |
2021年 | 256篇 |
2020年 | 561篇 |
2019年 | 1115篇 |
2018年 | 1012篇 |
2017年 | 1062篇 |
2016年 | 1086篇 |
2015年 | 942篇 |
2014年 | 968篇 |
2013年 | 1219篇 |
2012年 | 794篇 |
2011年 | 869篇 |
2010年 | 807篇 |
2009年 | 463篇 |
2008年 | 534篇 |
2007年 | 371篇 |
2006年 | 374篇 |
2005年 | 336篇 |
2004年 | 321篇 |
2003年 | 276篇 |
2002年 | 311篇 |
2001年 | 208篇 |
2000年 | 216篇 |
1999年 | 84篇 |
1998年 | 32篇 |
1997年 | 30篇 |
1996年 | 24篇 |
1995年 | 25篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 28篇 |
1991年 | 29篇 |
1990年 | 38篇 |
1989年 | 39篇 |
1988年 | 31篇 |
1987年 | 40篇 |
1986年 | 21篇 |
1985年 | 33篇 |
1984年 | 24篇 |
1983年 | 29篇 |
1981年 | 20篇 |
1978年 | 27篇 |
1977年 | 24篇 |
1976年 | 29篇 |
1975年 | 17篇 |
1974年 | 22篇 |
1973年 | 23篇 |
1972年 | 22篇 |
1970年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
Precision Agriculture - An accurate and robust strawberry flower representation and detection scheme is a key step to enable the reliable forecasting of fruit yield for use in precision... 相似文献
34.
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
35.
This article considers the experiences of a Samoan female geographer undertaking community‐based field research in her home country, and identifies some lessons for researchers working in similar circumstances. The paper suggests that ethical behaviour in research is ‘place‐specific’, and there is therefore a need to employ culturally sensitive and ‘location‐specific’ methodologies when undertaking community‐based research fieldwork. For the lead researcher, growing up in Samoa played a significant role in gaining an understanding of a set of robust and effective procedures to evaluate citizens' resilience to climatic and other environmental challenges. Fluency in everyday and more formal local languages, and awareness of local differences, each with multi‐layered connections to local communities, understanding cultural nuances and practising respect for va tapuia [sacred space or relationships] protocols, together facilitated the process of knowledge acquisition and helped to confirm the validity of the conclusions derived from the study. 相似文献
36.
Sohee Kim Tu Cam Le Sang-Ah Han Prima F. Hillman Ahreum Hong Sunghoon Hwang Young Eun Du Hiyoung Kim Dong-Chan Oh Sun-Shin Cha Jihye Lee Sang-Jip Nam William Fenical 《Marine drugs》2022,20(1)
Analysis of the chemical components from the culture broth of the marine bacterium Saccharomonospora sp. CNQ-490 has yielded three novel compounds: saccharobisindole (1), neoasterric methyl ester (2), and 7-chloro-4(1H)-quinolone (3), in addition to acremonidine E (4), pinselin (5), penicitrinon A (6), and penicitrinon E (7). The chemical structures of the three novel compounds were elucidated by the interpretation of 1D, 2D nuclear magnetic resonance (NMR), and high-resolution mass spectrometry (HRMS) data. Compound 2 generated weak inhibition activity against Bacillus subtilis KCTC2441 and Staphylococcus aureus KCTC1927 at concentrations of 32 μg/mL and 64 μg/mL, respectively, whereas compounds 1 and 3 did not have any observable effects. In addition, compound 2 displayed weak anti-quorum sensing (QS) effects against S. aureus KCTC1927 and Micrococcus luteus SCO560. 相似文献
37.
An updated list of all 27 species of aphelinids (Hymenoptera: Aphelinidae) in nine genera that have been identified or reported from South Korea, along with a dichotomous taxonomic key to separate them, is provided. Ten of the species are included in the EPPO ‘Positive list of biological control agents widely used in the EPPO region’ (which corresponds to Appendix 1 – Commercially used biological control agents – and to Appendix 2 – Successfully introduced classical biological control agents – of EPPO Standard PM 6/3, 2016 version). Five of these species are successfully used in classical biological control. Other species could be used in the EPPO region, or elsewhere in the world, in the future. 相似文献
38.
Although preference for NH4+, NO3? or a combination of the two often differs among species, we know little about the responses of invasive plants to different inorganic N forms. Furthermore, many studies have suggested that an increase in N availability may facilitate further invasions. However, most of these studies predicted the positive feedback without considering the preference for N forms of invasive plants. Therefore, we cultivated four common invasive species (Mikania micrantha, Ipomoea cairica, Wedelia trilobata and Bidens pilosa) in South China with hydroponic media containing different forms of N (i.e. NO3?, NH4NO3 and NH4+) at equimolar concentrations. Our results showed that the N forms significantly affected the growth, biomass allocation and physiological traits of the plants. All four invasive plants supplied with NO3? alone had better performance and greater allocation to root biomass than did plants that were supplied with NH4+ alone. Moreover, the photosynthetic rate, pigment content and photosystem II activity of plants supplied with NO3? or NH4NO3 were significantly higher than those of plants supplied with NH4+alone. The results suggested that all four invasive plants preferred NO3? rather than NH4+, and changes in NO3? played an important role in furthering the invasions of these plants than did changes in NH4+. Our results implied that decreasing NO3? may be a useful tool for controlling and managing invasive plants preferring NO3?. In addition, this study highlighted the importance of considering plant N form preference to better understand plant invasions. 相似文献
39.
A Cirujeda G Pardo A I Marí J Aibar Y Pallavicini J L Gonzlez‐Andújar J Recasens X O Sol‐Senan 《Weed Research》2019,59(4):300-311
40.
Fish contribute a significant amount of animal protein to the diets of people in Bangladesh, about 63% of which comes from aquatic animals. In Bangladesh, fish is mainly derived from two sources: capture and culture. Aquaculture has shown tremendous growth in the last two decades, exhibiting by about 10% average annual growth in production. Capture fisheries, although still the major source of supply of fish, have become static or are in decline due to over‐fishing and environmental degradation, and it is now believed that aquaculture has the greatest potential to meet the growing demand for fish from the increasing population. At present, aquaculture production accounts for about one‐third of the total fish production in Bangladesh. This paper examines the impact of an aquaculture development project in Bangladesh on food security, with particular emphasis on the poor. The analysis shows a positive impact of aquaculture development on employment, income and consumption. A number of implications for policy in areas that might strengthen these outcomes are discussed and recommendations are presented. 相似文献