首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   861篇
  免费   88篇
  国内免费   166篇
林业   18篇
农学   54篇
基础科学   79篇
  298篇
综合类   473篇
农作物   37篇
水产渔业   20篇
畜牧兽医   107篇
园艺   12篇
植物保护   17篇
  2024年   7篇
  2023年   35篇
  2022年   56篇
  2021年   55篇
  2020年   46篇
  2019年   41篇
  2018年   53篇
  2017年   65篇
  2016年   62篇
  2015年   47篇
  2014年   48篇
  2013年   56篇
  2012年   70篇
  2011年   79篇
  2010年   65篇
  2009年   53篇
  2008年   47篇
  2007年   40篇
  2006年   45篇
  2005年   43篇
  2004年   20篇
  2003年   17篇
  2002年   16篇
  2001年   15篇
  2000年   7篇
  1999年   9篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1995年   4篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
排序方式: 共有1115条查询结果,搜索用时 31 毫秒
101.
牛粪堆肥成型基质块蔬菜育苗灌溉方式   总被引:3,自引:2,他引:1  
为优选蔬菜育苗成型基质的灌溉方式,提高成型基质蔬菜育苗效果,以牛粪好氧堆肥腐熟料和牛粪蚯蚓堆肥腐熟料为主料配方的成型基质块为研究对象,在低位浸泡灌溉和微喷灌溉条件下,其中牛粪好氧腐熟料成型基质块灌溉耗水量体积的处理水平分别为2 500、350、700、1 050、1 400、1 750 m L,用T1、T2、T3、T4、T5、T6表示;牛粪蚯蚓堆肥腐熟料基质块灌溉耗水量体积的处理水平分别为3 000、700、1 050、1 400、1 750、2 100 m L,用TS1、TS2、TS3、TS4、TS5、TS6表示,探讨不同灌溉条件对2种牛粪腐熟料成型基质块中全氮(TN)、全磷(TP)、全钾(TK)的迁移及其吸水特性和育苗效果。结果表明,2种牛粪腐熟料成型基质块在低位浸泡灌溉下,其灌溉充分,淋洗脱盐量相对较小,并且对成型基质块的冲刷,扰动较小;微喷灌溉最小灌溉量T2或TS2下,虽然其淋洗损失的TN、TP、TK小于低位浸泡灌溉,但成型基质块未能被充分湿润,影响育苗效果;微喷灌溉在T3、T4、T5、T6或TS3、TS4、TS5、TS6处理水平下,成型基质块中的TN、TP、TK淋洗损失量均大于低位浸泡灌溉,并且随灌溉量的增大而逐步增大。对牛粪好氧堆肥腐熟料成型基质块,育苗前期应选取微喷灌溉T4进行前充分淋洗,育苗后期采取低位浸泡灌溉保留幼苗生长所需养分;而对牛粪蚯蚓堆肥腐熟料成型基质块,TS1处理下黄瓜幼苗的茎粗(6.23 mm)、株高(138.09 mm)、地上部分干质量(758.85 mg)、地下部分干质量(147.92 mg)和壮苗指数(217.64)均为该试验中最大值,灌溉水利用率为2.79g/kg,该处理水平下幼苗生长及水分有效利用率均较优,即可采取TS1处理对牛粪蚯蚓腐熟料成型基质块进行灌溉。  相似文献   
102.
Dry direct-seeded aerobic rice (DSR) is an emerging attractive alternative to traditional puddled transplanted rice (PTR) production system for reducing labour and irrigation water requirements in the Indo-Gangetic plains (IGP) of India. The fertilizer N requirement of DSR grown with alternate wetting and drying water management may differ from that of PTR grown under continuous flooding due to differences in N dynamics in the soil/water system and crop growth patterns. Limited studies have been conducted on optimizing N management and application schedule for enhanced N use efficiency in DSR. Therefore, field experiments were conducted over 3 years in NW India to evaluate the effects of N rate and timing of its application on crop performance and N use efficiency. Interaction effects of four N rates (0, 120, 150, and 180 kg ha?1) as urea and four schedules of N application on yield and N use efficiency were evaluated in DSR. The N schedules included N application in three equal split doses (0, 35 and 63, and 14, 35 and 63 days after sowing, DAS) and four equal split doses (0, 28, 49 and 70; 14, 28, 49 and 70 DAS). There was no significant interaction between N rate and schedules on grain yield. Significant response to fertilizer N was observed at 120 kg N ha?1 and economic optimum dose for three equal split doses and skipping N at sowing was 130 kg N ha?1. Highest mean grain yield of 6.60 t ha?1 was obtained when N was applied in three equal split doses at 14, 35 and 63 DAS which was about 8.5% higher compared with N applied in four equal split doses at 14, 28, 49 and 70 DAS. Under the best N application schedule, agronomic N use efficiency (26 kg grain kg?1), recovery efficiency (49%) and physiological efficiency (53 kg kg?1) were comparable to the values reported in Asia for PTR. Results from our study will help to achieve high yields and N use efficiency in DSR to replace resource intensive PTR.  相似文献   
103.
为考察超高温快速堆肥提高畜禽粪便处理效率的可行性及其产物农田施用效果,以鸡粪(chicken manure,CM)、猪粪(pig manure,PM)、奶牛粪(dairy manure,DM)和稻壳为发酵原料,监测其在85℃、发酵24 h前后的理化特性和嗜热微生物数量变化,并采用盆栽试验研究了鸡粪为主要原料的快速堆肥产物对小白菜出苗和生长的影响。结果表明,超高温发酵24 h后粪便中病原菌数量和含水率达到有机肥质量标准,70℃能生长的高温微生物数量提高2个数量级。超高温快速堆肥后,CM,PM,DM浸提液可溶性有机碳质量分数分别增加了46.5%、22.9%和42.6%,挥发性脂肪酸质量分数分别增加了37.2%,31.2%和56.8%。超高温快速堆肥对CM,PM,DM总氮、总磷、总钾含量影响不大,但游离氨基酸质量分数分别增加79.2%,58.1%,74.6%;总腐殖质质量分数分别增加了27.6%,3.4%,27.3%。CM,PM中铵态氮质量分数分别上升了114.6%,40.6%(P0.001),因而降低了种子发芽指数和小白菜出苗率。但出苗后,施用超高温快速堆肥产物的小白菜地上部生物量最高,分别比施用纯化肥、腐熟有机肥高出20.4%(P0.05)和51.9%(P0.05)。可见超高温快速堆肥(85℃,24 h)提高畜禽粪便处理效率是可行的,其产物施入土壤能减少无机氮肥的施用,但不宜用于育苗,施用时应根据土壤和作物类型,采用合理的施用量和施用方法。  相似文献   
104.
为探讨微生物和生物炭联用对畜禽粪便堆肥过程中重金属钝化效果的影响,该文研究生物炭(花生壳炭、木屑炭、玉米秸秆炭)与复合微生物菌剂联用对重金属Pb、Cd形态转化及钝化效果的影响。试验结果表明:9个处理高温期维持天数均达无害化卫生要求,生物炭添加比例对堆肥过程中温度变化影响显著。对Pb的钝化效果最优处理是24%花生壳生物炭和1%的菌剂(T9),可交换态分配率较堆前下降16.32%,钝化效率为74.60%。对Cd的钝化效果最优的处理是24%木屑炭和1.5%的菌剂(T3),交换态Cd与堆前相比下降7.96%,钝化效率为58.13%。统计分析结果表明,重金属Pb、Cd的钝化效果与堆肥过程中平均pH值呈显著正相关,重金属Pb的钝化效果与堆肥过程中温度平均值呈显著正相关,重金属Cd的钝化效果与有机质降解率呈显著正相关。  相似文献   
105.
农村河道清淤产生的淤泥,体量大、有机物浓度高,处置不当会造成二次污染。现代农业的工厂化育苗需求大量的营养土,就地取土导致耕地退化。该研究利用功能微生物发酵淤泥制备育苗基质,研究不同菌株发酵基质的物理和生物学性状,基质培育西瓜苗的生长、生理参数和抗逆性能。结果表明:微生物处理均能够提升淤泥基质物理和生物学性能,同时能够提升育苗质量。其中Trichoderma harzianum T83(T83)、Bacillus amyloliquefaciens IAE(BIAE)菌株发酵基质性能最好。相较于对照处理基质的最大持水量、总孔隙度、毛管孔隙度、通气孔隙度,T83处理分别增加了64.25%、52.65%、45.05%、56.11%;BIAE处理分别增加了101.17%、45.43%、61.43%、38.14%。相较于对照处理西瓜苗的株高、鲜质量、干质量、叶绿素含量、根系活力、根际真菌、细菌数量,T83处理分别增加了66.85%、52.07%、72.16%、43.13%、54.93%、110.62倍、1.63倍;BIAE处理分别增加了80.40%、57.34%、82.37%、54.88%、46.40%、67.26%、2.60倍、2.94倍。T83和BIAE处理西瓜苗叶片过氧化氢酶和超氧化物歧化酶酶活显著增加,根系丙二醛含量显著降低。真菌菌株T. harzianum T83和细菌菌株B. amyloliquefaciens IAE发酵淤泥,能够显著提升其农用品质,为淤泥高附加值化农用提供一条可行的途径。  相似文献   
106.
典型畜禽粪便配伍食用菌菌渣堆肥研究   总被引:5,自引:0,他引:5  
[目的]研究三种典型畜禽粪便工厂化高温好氧堆肥过程中物理化学参数的动态变化规律,为典型禽畜粪便和食用菌菌渣废弃物有机肥料化提供理论依据。[方法]本研究分别以新鲜牛粪、猪粪和鸡粪配以2倍质量(DW)的食用菌菌渣进行堆肥试验,研究了堆肥过程中温度、pH值、铵态氮、硝态氮和发芽指数等理化指标的动态变化规律。[结果]堆肥过程中牛粪、鸡粪和猪粪处理在55 ℃以上的持续时间均超过15 天,堆体温度均超过70 ℃。堆肥结束时,猪粪、鸡粪、牛粪处理的pH值分别为7.59、7.81、7.48,符合腐熟堆肥pH值在 5.5 ~ 8.5的一般标准,种子发芽指数(GI)均大于80%,总养分(N+P2O5+K2O)分别为4.31%、5.01%、4.57%,只有鸡粪处理满足有机肥养分标准(NY525-2012)。堆肥过程中各处理铵态氮含量逐渐下降,硝态氮含量逐渐增加,至堆肥结束时牛粪、鸡粪和猪粪处理铵态氮的减少量分别为45.6%、29.2%、33.9%,而相应地硝态氮含量分别增加到2.59 g kg-1、2.57 g kg-1、2.15 g kg-1。[结论]本研究结果可为适度规模养殖场的畜禽粪便进行堆肥处理提供一定的理论依据。  相似文献   
107.
Highlights of progress in the production of silage over the past 50 years include the introduction of improved hybrids of maize (Zea mays L.), the forage harvester, the big baler, polyethylene covering for horizontal silos, stretch‐wrap film for bales and novel additives designed to improve the fermentation and aerobic stability of silage. The key biochemical pathways in the silage fermentation have been described together with the effects of microbial and chemical additives on fermentation and aerobic stability during the feed‐out phase. The significance of oxygen and water in silage fermentation has been quantified and efficacy of covering silos has been established, with recent progress in the development of oxygen barrier film. Future perspectives include improving food safety and animal health by increasing the hygienic quality of silage, reducing the environmental impact of silage by decreasing loss of nitrogen to soil and atmosphere, reducing methanogenesis in the rumen and increasing methane yield from silage as biofuel, and the use of silages as feedstocks for multiple end uses in biorefineries.  相似文献   
108.
This study investigated the effects of different additives on fermentation quality and aerobic stability of Leymus chinensis silage. Treatments included (i) no additive, (ii) 3 mL kg?1 formic acid (FA), (iii) 6 mL kg?1 FA, (iv) 5 mL kg?1 acetic acid (AA), (v) 10 mL kg?1 AA, (vi) 2 mL kg?1 propionic acid (PA), (vii) 4 mL kg?1 PA, (viii) 5 mL kg?1 butyric acid (BA), (ix) 10 mL kg?1 BA, (x) 1.0 g kg?1 potassium sorbate (PS), (xi) 1.0 g kg?1 sodium benzoate (SB), (xii) 1 × 108 colony‐forming units (cfu) kg?1 Lactobacillus (Lb) plantarum LP (LP), (xiii) 1 × 108 cfu kg?1 Lb. brevis LB (LB) and (xiv) 1 × 108 cfu kg?1 Lb. buchneri NCIMB40788 (Fresh). Each additive treatment was based on fresh matter (FM). Results showed that all additives decreased pH values. All additives except Fresh decreased ammonia‐N content (< .001). Both LP and LB increased lactic acid content (< .001). Butyric acid content increased with FA (3 mL kg?1) and BA, but decreased with PA, PS, SB, FA (6 mL kg?1), AA, LP, LB (< .001). FA (3 mL kg?1), AA (10 mL kg?1), PA, BA, PS, SB and Fresh improved aerobic stability (< .001). After 8 days exposure to air, the pH value and yeast count were lower in FA (3 mL kg?1), BA (10 mL kg?1), SB treatments than in other treatments. Overall, AA outperformed all other additives in improving fermentation quality. Sodium benzoate and AA could be used as an effective additive to improve aerobic stability of L. chinensis silage.  相似文献   
109.
Aerobic rice technology is still new in Malaysia, and information regarding MARDI Aerob 1 (MA1), the first local aerobic rice variety, is still lacking. Therefore, comparative studies were carried out to determine the physiological performance of aerobic rice variety MA1 and lowland rice variety MR253 under water stress given at the panicle initiation, flowering and ripening stages. This experiment was arranged in a randomized complete block design. Stomatal conductance (gs), chlorophyll a fluorescence (Fv/Fm), leaf relative water content (leaf RWC), and soil moisture content (SMC) as well as yield component parameters such as panicle number, grain yield and 100-grain weight were measured. Results revealed that gs and leaf RWC for both varieties decreased with depletion of SMC. The correlation study between the physiological parameters and SMC indicated that Fv/Fm was not affected by water stress, regardless of varieties. The yield components (panicle number, grain yield and 100-grain weight) for both varieties greatly decreased when water stress was imposed at the panicle initiation stage. This study showed that the panicle initiation period was the most sensitive stage to water stress that contributed to a substantial reduction in yield for both varieties. Under the aerobic condition (control), MR253 produced higher panicle number, 100-grain weight and yield than MA1. Although MR253 is bred for lowland, it is well adapted to aerobic condition.  相似文献   
110.
建立Soleris微生物实时光电检测法检测生乳中菌落总数的快速测定方法,并将该方法与国标的平板计数法进行比较。结果表明:Soleris法检测生乳中菌落总数的标准曲线为y=-0.651 5x+8.263 9(y为菌落总数(lg(CFU/mL)),x为胶体栓变色时间(h)),相关系数R2=-0.939 6,表明标准曲线相关性良好;重复性实验结果的相对标准偏差均小于5%;Soleris法与平板计数法测定结果的比较表明,2 种方法之间没有显著性差异(P>0.05)。在本研究的实验条件下,Soleris法检测生乳中  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号