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当国人争先恐后地奔赴新加坡、泰国、马来西亚等地领略异域风光时,外国旅游者也成群结队地来到中国,足迹深入到寂寞广辽的大漠、古老神奇的自然风景区,与自然界的生灵“握手”。今年,是中国生态旅游年,期待已久的生态旅游已撩开神秘的面纱,走入人们的视野。

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Pearl River is the property of Pearl River Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Quantitative assessment of nitrogen（N）balance in greenhouse vegetable fields could enhance our understanding of N loss path in soil and its potential environmental pollution, which could be beneficial for the green development of intensive greenhouse vegetable production in China. In this study, we analyzed N balance and its spatial distribution in greenhouse vegetable fields based on 648 groups of available data selected from the CNKI and Web of Science according to the National Key Area Development Plan of Greenhouse Vegetables （2015-2020）. Our results showed that the apparent nitrogen balance of greenhouse vegetable fields was positive in every growing season （49~1154 kg N·hm-2）, and the mean was 324 kg N·hm-2. The mean nitrogen use efficiency（NUE）of greenhouse vegetable fields was 18.6%. Regarding N input, the total nitrogen input per growing season was approximately 863 kg N·hm-2. Chemical fertilizer and organic fertilizer were two major sources（471 kg N·hm-2 vs 306 kg N·hm-2）of nitrogen, and the nitrogen contributed by irrigation water could not be ignored（86 kg N·hm-2）. Regarding N output, the total nitrogen output per growing season was approximately 539 kg N·hm-2 and the percentages absorbed by crops and lost to the environment（leaching, nitrification and denitrification, and NH3 volatilization）were 42.6% and 57.4%, respectively. The distribution of N balance exhibited a spatial heterogeneity pattern. The N surplus in the Huang-Huai-Hai and the warm temperature area around the Bohai Sea were the highest（441 kg N·hm-2）. The main reasons were the large amount of nitrogen input and low crop absorption. In addition, the nitrogen loss in this area was also high, and the leaching loss reached 186 kg N·hm-2. Our result suggested that the overall apparent nitrogen balance of Chinese vegetable fields showed a positive surplus, mainly owing to the large amounts of chemical fertilizer and organic fertilizer input, but there was a high risk of nitrogen loss. Reducing N input as well as improving crop up⁃ take and NUE may be promising ways to optimize N management. It is necessary to reduce nitrogen input and mainly focus on nitrogen leach⁃ ing losses, especially in Huang-Huai-Hai and the warm temperature area around the Bohai Sea. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)