全文获取类型
收费全文 | 1891篇 |
免费 | 128篇 |
国内免费 | 143篇 |
专业分类
林业 | 68篇 |
农学 | 110篇 |
基础科学 | 42篇 |
129篇 | |
综合类 | 694篇 |
农作物 | 84篇 |
水产渔业 | 443篇 |
畜牧兽医 | 188篇 |
园艺 | 25篇 |
植物保护 | 379篇 |
出版年
2024年 | 15篇 |
2023年 | 35篇 |
2022年 | 53篇 |
2021年 | 68篇 |
2020年 | 76篇 |
2019年 | 70篇 |
2018年 | 46篇 |
2017年 | 80篇 |
2016年 | 103篇 |
2015年 | 73篇 |
2014年 | 113篇 |
2013年 | 149篇 |
2012年 | 154篇 |
2011年 | 148篇 |
2010年 | 112篇 |
2009年 | 114篇 |
2008年 | 87篇 |
2007年 | 105篇 |
2006年 | 85篇 |
2005年 | 82篇 |
2004年 | 75篇 |
2003年 | 62篇 |
2002年 | 50篇 |
2001年 | 44篇 |
2000年 | 25篇 |
1999年 | 24篇 |
1998年 | 15篇 |
1997年 | 18篇 |
1996年 | 11篇 |
1995年 | 18篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1982年 | 2篇 |
排序方式: 共有2162条查询结果,搜索用时 15 毫秒
81.
湿润直播稻田杂草出苗动态与发生规律 总被引:5,自引:3,他引:5
1996~1997年在浙江嘉兴调查了湿润直播稻田杂草出苗动态和发生规律,并比较了直播与移栽,早稻、单季晚稻与连作晚稻直播,翻耕与免耕直播间杂草发生差异。湿润直播稻田杂草以稗草、千金子、异型莎草、节节菜、陌上菜为主,其次有通泉草、丁香蓼、水芹。禾本科、莎草科和阔叶杂草种类数分别占25.0%、18.8%和56.2%,出苗数量分别占11.2%、11.6%和77.2%。单季晚稻直播田稗草、千金子发生重于其他直播田,直播田稗草和千金子数量明显高于移栽田。直播田杂草于播种后3~4 d陆续出苗,1~3周达到高峰。连作晚稻直播田播后6~8周出现明显的第二个出苗高峰。以阔叶杂草为绝对优势的翻耕直播田杂草发生重于免耕田。直播田杂草数量自然消长呈现与出苗动态相同的趋势。直播田杂草发生以稗草、千金子、丁香蓼较早,节节菜、陌上菜、通泉草次之,异型莎草和水芹较迟。稗草、千金子及其他几种主要杂草出苗高峰均呈单峰状态,而节节菜、陌上菜在连作晚稻直播田的出苗则为双峰。 相似文献
82.
[目的]解决早熟禾草坪中禾本科杂草的防除难题。[方法]采用坪安2号、坪安3号加草坪抑制荆对早熟禾草坪中的禾本科杂草进行防除试验。[结果]坪安2号300倍液对早熟禾草坪中的禾本科杂草防除效果较好。[结论]坪安2号可有效防除早熟禾草坪中禾本科杂草,且对草坪安全,环境污染小。 相似文献
83.
Giovanni M Turchini Rasanthi M Gunasekera & Sena S De Silva 《Aquaculture Research》2003,34(9):697-708
The efficacy of trout oil (TO), extracted from trout offal from the aquaculture industry, was evaluated in juvenile Murray cod Maccullochella peelii peelii (25.4±0.81 g) diets in an experiment conducted over 60 days at 23.7±0.8 °C. Five isonitrogenous (48% protein), isolipidic (16%) and isoenergetic (21.8 kJ g?1) diets, in which the fish oil fraction was replaced in increments of 25% (0–100%), were used. The best growth and feed efficiency was observed in fish fed diets containing 50–75% TO. The relationship of specific growth rate (SGR), food conversion ratio (FCR) and protein efficiency ratio (PER) to the amount of TO in the diets was described in each case by second‐order polynomial equations (P<0.05), which were: SGR=–0.44TO2+0.52TO+1.23 (r2=0.90, P<0.05); FCR=0.53TO2–0.64TO+1.21 (r2=0.95, P<0.05); and PER=–0.73TO2+0.90TO+1.54 (r2=0.90, P<0.05). Significant differences in carcass and muscle proximate compositions were noted among the different dietary treatments. Less lipid was found in muscle than in carcass. The fatty acids found in highest amounts in Murray cod, irrespective of the dietary treatment, were palmitic acid (16:0), oleic acid (18:1n‐9), linoleic acid (18:2n‐6) and eicosapentaenoic acid (20:5n‐3). The fatty acid composition of the muscle reflected that of the diets. Both the n‐6 fatty acid content and the n‐3 to n‐6 ratio were significantly (P<0.05) related to growth parameters, the relationships being as follows. Percentage of n‐6 in diet (X) to SGR and FCR: SGR=–0.12X2+3.96X–32.51 (r2=0.96) and FCR=0.13X2–4.47X+39.39 (r2=0.98); and n‐3:n‐6 ratio (Z) to SGR, FCR, PER: SGR=–2.02Z2+5.01Z–1.74 (r2=0.88), FCR=2.31Z2–5.70Z+4.54 (r2=0.93) and PER=–3.12Z2–7.56Z+2.80 (r2=0.88) respectively. It is evident from this study that TO could be used effectively in Murray cod diets, and that an n‐3:n‐6 ratio of 1.2 results in the best growth performance in Murray cod. 相似文献
84.
85.
测定了信阳市主要野生水产动物Cd、Cr、Pb、As和Hg的含量,并根据单因子污染指数评价法对信阳市主要野生水产动物的品质进行质量安全评价。结果表明,8种信阳市主要野生水产动物的所有样品中均检出Pb和Cr,但均未检出Cd和Hg。在鲫鱼、鲤鱼、青虾和克氏原螯虾中检出As,检出率分别为60%、65.5%、55%和50%。单因子污染指数评价法表明,8种信阳市主要野生水产动物均受到不同程度的Pb污染,鲤鱼和鲫鱼受到了轻度的As污染。 相似文献
86.
87.
88.
Irena Pípalová 《Aquaculture International》2003,11(4):325-336
The aims of this experiment were (1) toquantify the ability of grass carp to processduckweed and (2) to assess indirect changes inwater chemistry and phytoplankton community,caused by grass carp feeding. Yearling grass carp sized 126 ± 7.7 mm (TL) and19.6 g in weight were kept in 9 laminate tanksof 1 m3 for 14 days. Two stockingdensities (2 and 6 fish per m3) anda control without fish were used. Standard growthrate (SGR) of grass carp fed exclusively onduckweed was 0.70% body weight (BW) d–1and food conversion ratio (FCR) reached 2.0(average water temperature =21.1 ± 3.8 °C). Daily food intakewas 0.2 g of duckweed dry weight (DW), i.e.,1% of average BW of grass carp. SGR ofduckweed growing in 20 × 20 cm floatingenclosures, differed significantly[F(6,2) = 417.9; p = 0.002] between the twostocking densities of grass carp and thecontrol tanks (without fish). Mean SGR ofduckweed was 0.02 g g–1 day–1 and thehighest SGR was recorded in the control tanks.Both decrease in NH4-N and increase inNO2-N concentrations differedsignificantly between the treatments[F(2,2) = 45.3; p = 0.02 and F(2,2) = 19.2; p = 0.04 respectively]. Changes in other nitrogenand phosphorus components (NO3-N, TN, TPand PO4-P) caused by stocking of grasscarp were not significant. Biomass ofphytoplankton, dominated by filamentous algaeand blue-greens, increased proportionately tostocking density of grass carp. Althoughduckweed has a large potential for nutrientremoval, the most common pathway for thenutrients released through grass carp grazingif duckweed cover is loose is theirincorporation into phytoplankton biomass. 相似文献
89.
Effect of dietary components on the gut microbiota of aquatic animals. A never‐ending story?
下载免费PDF全文
![点击此处可从《Aquaculture Nutrition》网站下载免费的PDF全文](/ch/ext_images/free.gif)
E. Ringø Z. Zhou J.L.G. Vecino S. Wadsworth J. Romero Å. Krogdahl R.E. Olsen A. Dimitroglou A. Foey S. Davies M. Owen H.L. Lauzon L.L. Martinsen P. De Schryver P. Bossier S. Sperstad D.L. Merrifield 《Aquaculture Nutrition》2016,22(2):219-282
It is well known that healthy gut microbiota is essential to promote host health and well‐being. The intestinal microbiota of endothermic animals as well as fish are classified as autochthonous or indigenous, when they are able to colonize the host's epithelial surface or are associated with the microvilli, or as allochthonous or transient (associated with digesta or are present in the lumen). Furthermore, the gut microbiota of aquatic animals is more fluidic than that of terrestrial vertebrates and is highly sensitive to dietary changes. In fish, it is demonstrated that [a] dietary form (live feeds or pelleted diets), [b] dietary lipid (lipid levels, lipid sources and polyunsaturated fatty acids), [c] protein sources (soybean meal, krill meal and other meal products), [d] functional glycomic ingredients (chitin and cellulose), [e] nutraceuticals (probiotics, prebiotics, synbiotics and immunostimulants), [f] antibiotics, [g] dietary iron and [h] chromic oxide affect the gut microbiota. Furthermore, some information is available on bacterial colonization of the gut enterocyte surface as a result of dietary manipulation which indicates that changes in indigenous microbial populations may have repercussion on secondary host–microbe interactions. The effect of dietary components on the gut microbiota is important to investigate, as the gastrointestinal tract has been suggested as one of the major routes of infection in fish. Possible interactions between dietary components and the protective microbiota colonizing the digestive tract are discussed. 相似文献
90.
气相色谱法测定水产品中氯霉素残留 总被引:21,自引:1,他引:21
介绍了水产品中氯霉素残留量测定的气相色谱法。样品中的氯霉素用乙酸乙酯提取,正己烷去脂肪,过Sep-C18柱进行净化,用BSTFA-TMCS衍生后进带有微电子俘获器的气相色谱仪检测。该方法的线性范围为0.5~500μg·L-1,相关系数r=0.999,最低检测限为0.1μg·kg-1,相对标准偏差为4.3%~11.0%,向样品中分别添加1μg·kg-1、10μg·kg-1和20μg·kg-13个浓度水平的氯霉素,回收率分别为62.0%、88.2%和96.4%。方法灵敏度高,准确可靠,适合水产品中氯霉素残留量的检测。 相似文献