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991.
Perumal Palanivell Nik Muhamad Ab Majid 《Communications in Soil Science and Plant Analysis》2017,48(17):2083-2092
Application of urea in lowland rice fields leads to ammonia (NH3) volatilization and environmental pollution, and diminishes nitrogen recovery by rice (Oryza sativa L.). Amending urea with biochar could reduce NH3 loss from urea as well as improve chemical properties of acid soils. An incubation study was conducted using a closed-dynamic air flow system to determine NH3 volatilization from urea and chemical properties of an acid soil (Typic Paleudults). The soil was mixed with three rates of chicken litter biochar (20, 40, and 60 g pot?1) and 1.31 g urea. Mixing an acid soil with biochar (60 g pot?1) in waterlogged to stimulate conditions in paddy condition significantly reduced NH3 loss and total titratable acidity. Biochar application also increased soil pH, total nitrogen, available nitrate, organic matter, total organic carbon, total carbon, available phosphorus, and exchangeable cations. Thus, chicken litter biochar can be used to reduce urea-N loss and ameliorate chemical properties of acid soils. This aspect is being embarked on in our on-going field experiments. 相似文献
992.
The objective was to determine the most favorable nitrogen (N) source ratio of ammonium (NH4+) to nitrate (NO3?) for aeroponic culture of Chinese fragrant solomonseal Polygonatum odoratum (Mill.) Druce seedlings. Seedlings were cultured with solutions based on 50% Hoagland formula containing 0:100, 10:90, 20:80, and 30:70 NH4+:NO3? ratios for 21 days. Activities of anti-oxidant enzymes and glutathione contents of leaves with treatments of 10:90 and 20:80 NH4+:NO3? ratios were higher than that of all-nitrate treatment, and malondialdehyde (MDA) concentrations were lower than that of all-nitrate treatment. The maximum quantum yield ?Po value was normal among all of the treatments, whereas the absorption energy ABS/CSm value with 20:80 NH4+:NO3? treatment was highest and the heat dissipation DIo/CSm value with 20:80 NH4+:NO3? treatment was lowest among all of the treatments. These results supported that moderate proportion of 20% NH4+ in the solution provided optimal growth condition for (P) P. odoratum aeroponic culture. 相似文献
993.
《Land Degradation \u0026amp; Development》2017,28(3):856-869
Spatiotemporal heterogeneity of soil available nitrogen (AN) (sum of NO3−–N and NH4+–N) is the essential basis for soil management and highly correlates to crop yield. Both geostatistical and traditional analyses were used to describe the spatiotemporal distribution of AN in the 0–20‐cm soil depth on typical Mollisol slopes (S1 and S2) in Northeast China. The concentration of NO3−–N dynamics at slope positions was typically opposite to NH4+–N. The peak values of AN typically moved from the summit of the slope to the bottom from spring to autumn and were mainly influenced by the content of NO3−–N (S1, 7·9–18·9 mg kg−1; S2, 1·2–103·6 mg kg−1), both of NO3−–N (S1, 3·9–8·3 mg kg−1; S2, 2·2–28·0 mg kg−1) and NH4+–N (S1, 21·4–30·5 mg kg−1; S2, 2·1–23·3 mg kg−1), and NH4+–N (S1, 10·5–28·9 mg kg−1; S2, 5·0–39·0 mg kg−1) in the seedling stage, vegetative growth stage, and reproductive growth stage, respectively. The spatial autocorrelation of AN was strong and was mainly influenced by structural factors during crop growth stages. This was mainly determined by soil erosion–deposition (SED) and soil temperature–moisture (STM) in the seedling stage; this was also mainly influenced by SED, STM, crop type, and crop growth in the vegetative growth stage and by early STM and early SED in the reproductive growth stage. Generally, the content of AN, NO3−–N, and NH4+–N on the whole slope was mainly determined by the early SED and local fertilizer application, while their spatiotemporal heterogeneity, especially the evenness, was mainly changed by SED, STM, crop growth, and crop types on the slope scale. In order to increase more crop yields, additional N fertilizer application on both the summit and the bottom during the vegetative growth stage and conservation tillage systems or additional soil amendments on the back slopes was necessary. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
994.
民勤退化人工梭梭种群雨养恢复试验研究 总被引:2,自引:0,他引:2
通过对民勤人工梭梭种群更新、平茬矮化和林地结皮改造试验,探讨梭梭种群雨养恢复关键技术措施。结果表明:民勤人工梭梭种群以半固定沙丘、沙地上更新较好,更新苗平均密度为1 130~2 280株.hm-2,但当年生幼苗保存率低,为20.6%~53.3%,这主要受降水和风蚀环境的限制;人工梭梭全平茬处理明显促进了梭梭枝条生长和萌发,平茬后当年高生长量平均58.9 cm,新枝平均长度27.0 cm,二次枝萌发数平均16.9个,分别为半平茬梭梭的1.1倍、1.6倍和1.3倍;梭梭林地结皮的穴状破坏加速了降水水分入渗过程,降水入渗深度可达70 cm,结皮带状和片状处理对降水产生一定的截留,降水在50~70 cm之间入渗。 相似文献
995.
996.
997.
Donna Peppin Peter Z. Fulé Carolyn Hull Sieg Jan L. Beyers Molly E. Hunter 《Forest Ecology and Management》2010
Broadcast seeding is one of the most widely used post-wildfire emergency response treatments intended to reduce soil erosion, increase vegetative ground cover, and minimize establishment and spread of non-native plant species. We conducted an evidence-based review to examine the effectiveness and effects of post-wildfire seeding treatments on soil stabilization, non-native species invasion, and plant community recovery in the western U.S. We reviewed 94 scientific papers and agency monitoring reports identified using a systematic search protocol. As sampling designs have become more rigorous in recent years, evidence that seeding is effective in reducing erosion has decreased. Of highest and high quality studies evaluating soil erosion, 92% (11 of 12) were published since 2000, none of which showed an effective result. Before 2000, the majority of the studies (71%) fell into the lowest quality categories, of which 72% showed seeding to be effective. The majority of studies (20 of 27, 74%) evaluating soil erosion in seeded versus unseeded controls showed that seeding did not reduce erosion relative to unseeded controls. Even when seeding significantly increased vegetative cover, seeded sites rarely supported plant cover levels considered sufficient to stabilize soils within the first and second year post-wildfire. Of the 11 studies evaluating seeding effectiveness for curtailing invasions of non-native plant species, an almost equal percentage found seeding treatments to be either effective (54%, 6 studies) or ineffective (45%, 5 studies). However, the majority of effective and ineffective treatments (83% and 80%, respectively) used non-native species. Sixteen of 26 studies (62%) evaluating seeding effects on plant communities reported that seeding suppressed recovery of native plants, although data on long-term impacts of this reduction are limited. The literature suggests that post-wildfire seeding does little to protect soil in the short-term, has equivocal effect on invasion of non-native species, and can have negative effects on native vegetation recovery, although long-term studies are needed to assess lasting impacts of seeded species. 相似文献
998.
The present study shows that microwave pretreatment coupled with solvent extraction is a clean and dry process for the production of crude palm oil (CPO). The results indicate that palm fruits microwave heated for 3 min achieved oil yield comparable to the conventional and commercial palm oil milling process with an average of 20%. Fatty acid composition (FAC) of the CPO produced shows an increment in lauric acid (C12:0) as the duration of microwave exposure increases. Due to the absence of wet-heat treatment or sterilization process, the resultant palm oil also exhibits desirable and very low free fatty acid (FFA) (0.26%) and moisture content (0.05%). The current approach has also provided surprisingly high vitamin E and carotenes content. The highest concentration of vitamin E (2345 ppm) and carotene content (1585 ppm) was recorded for palm fruits subjected to microwave for 2 min. It shows that under the investigated conditions in the present study, the quality of CPO produced using microwave treatment coupled with hexane extraction possesses superior qualities compared to the conventional palm oil milling process. 相似文献
999.
1000.
Adverse consequences of stock recovery: European hake,a new “choke” species under a discard ban? 下载免费PDF全文
Many commercial fish stocks are beginning to recover under more sustainable exploitation regimes. In this study, we document the temporal and spatial changes in one remarkable example of stock recovery: northern European hake (Merluccius merluccius). Analysing data from several scientific surveys, we document a dramatic increase in estimates of biomass between 2004 and 2011 throughout the larger area now occupied by the stock. The largest increase occurred in the North Sea, where hake have been largely absent for over 50 years. Spatio‐temporally resolved commercial landings show that high densities occur in the North Sea only between April and September, suggesting a density‐dependent seasonal habitat expansion to suitable temperature and depth conditions. These changes have implications for the management of the stock which are discussed. Notably, if discards are banned as part of management revisions, the relatively low quota for hake in the North Sea will be a limiting factor (the so‐called ‘choke’ species) which may result in a premature closure of the entire demersal mixed fishery in the North Sea, jeopardizing many commercial fisheries in the region. This example of the unforeseen consequences of improved stewardship highlight the need for a more holistic, regional and responsive approach to managing our marine ecosystems. 相似文献