全文获取类型
收费全文 | 760篇 |
免费 | 30篇 |
国内免费 | 80篇 |
专业分类
林业 | 33篇 |
农学 | 41篇 |
基础科学 | 16篇 |
182篇 | |
综合类 | 256篇 |
农作物 | 70篇 |
水产渔业 | 58篇 |
畜牧兽医 | 177篇 |
园艺 | 22篇 |
植物保护 | 15篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 29篇 |
2020年 | 26篇 |
2019年 | 27篇 |
2018年 | 24篇 |
2017年 | 31篇 |
2016年 | 35篇 |
2015年 | 35篇 |
2014年 | 49篇 |
2013年 | 80篇 |
2012年 | 66篇 |
2011年 | 49篇 |
2010年 | 45篇 |
2009年 | 34篇 |
2008年 | 51篇 |
2007年 | 25篇 |
2006年 | 31篇 |
2005年 | 36篇 |
2004年 | 19篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 13篇 |
1999年 | 21篇 |
1998年 | 11篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有870条查询结果,搜索用时 15 毫秒
121.
122.
123.
124.
硫酸钾镁肥在马铃薯上的肥效试验研究 总被引:1,自引:1,他引:0
进行硫酸钾镁肥在马铃薯上的肥效试验研究,结果表明:磷酸二铵450 kg/hm2+尿素75 kg/hm2+硫酸钾镁肥300 kg/hm2的处理马铃薯产量最高,磷酸二铵450 kg/hm2+尿素75 kg/hm2+硫酸钾镁肥225 kg/hm2的处理施肥投入成本较低,经济效益最佳。 相似文献
125.
用不同浓度硫酸铜、异噻唑啉酮对采自养殖池塘的黄丝藻藻华染毒,分时采样,用分光光度计法测定叶绿素a(ChII a)含量,用相应的试剂盒测定丙二醛(MDA)含量、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性的变化。结果表明,硫酸铜、异噻唑啉酮对黄丝藻24、48、72、96 h的半数有效浓度(EC50)分别为5.551、4.543、3.646、2.898mg/L 和13.712、9.858、8.680、5.114 mg/L。随着浓度的升高,硫酸铜、异噻唑啉酮对黄丝藻的毒性越来越强,浓度为2.40 mg/L 时黄丝藻ChII a含量、SOD、CAT 活性较低,而MDA 含量较高,说明此时黄丝藻细胞已经完全解体。浓度为0.42 mg/L 时,各个测量值与对照组差异不显著,说明低浓度两种除藻剂96 h内对黄丝藻的毒性较小。结果说明两种除藻剂都可以抑制或者杀死黄丝藻藻华,并且硫酸铜对黄丝藻藻华的毒性较异噻唑啉酮强。 相似文献
126.
《Communications in Soil Science and Plant Analysis》2012,43(1):7-12
Abstract Sulfate concentration in the equilibrium solutions of a black solonetz soil was different at each moisture content. In the sub‐surface horizons a decrease in soil moisture up to about 35 percent resulted in a gradual increase of sulfate concentration. However, with further decrease in moisture the sulfate concentration increased abruptly. Variation of sulfate concentration appears to alter significantly certain cation ratios in the equilibrium solutions. 相似文献
127.
《Communications in Soil Science and Plant Analysis》2012,43(11):1087-1103
Abstract An automated turbidimetric method has been developed for the rapid and accurate determination of sulfate. The method is practical and useful for accurately measuring total sulfur in plant tissues, and extractable sulfate in soils. The principle of intermittent reagent addition is used which eliminates drift and sensitivity changes caused by coating of BaSO4 on tubing and cell walls. Also, the appropriate chemistry is used to minimize interactions of the wash with the sample at a sampling rate of 30/H. The sensitivity of the method is excellent with a working range of 0 to 15 ppm sulfur for soils. For plant digests the sample solutions are diluted to 0–35 ppm S. The precision as determined by repeated analysis of a soil sample extract was 0.58% RSD with a mean of 9.26 pg/g extractable SO= 4‐S. On another soil sample using a different extractant and extraction procedure the RSD was 0.64%, mean of 9.26 μg/g. Multiple automated sulfur analyses on a plant tissue digest resulted in an RSD of 0.41% for a sample containing 0.21% S. The automated turbidimetric method for sulfate has excellent precision and sensitivity in plant tissue and soil analyses where gravimetric BaSO4 assays are not practical. 相似文献
128.
15N示踪技术已开始应用于畜禽粪便氮素循环与利用研究领域,而15N在畜禽粪便不同组分和不同形态氮素中的丰度与数量将直接影响到畜禽粪便15N示踪去向与氮素实际去向的一致性。为了解15N在畜禽粪便标记过程的转化特点和在标记粪尿的分布特征,本文首先采用改进的、含有15N标记硫酸铵(60 atom%15N)的Hoagland营养液砂培种植15N玉米,然后将15N玉米和普通玉米以55∶45的氮配比作为混合青贮饲料饲喂1头已空腹2 d的2龄黄牛,饲喂4 d后停喂2 d,收集全部牛粪尿并对其不同组分和形态氮素的15N丰度和数量进行分析。结果表明:标记玉米、混合青贮饲料、牛粪尿的15N丰度分别为48.024%、26.579%和8.044%;标记玉米对硫酸铵15N的回收率为26.3%,牛粪尿对标记玉米15N回收率为36.0%。在收集的牛粪尿氮中,牛粪全氮、牛尿全氮、牛粪铵态氮和牛尿铵态氮量分别占70.25%、29.75%、5.44%和0.03%,其15N丰度分别为9.223%、5.261%、6.505%和5.419%。在短期内通过饲喂黄牛15N青贮饲料制备的标记牛粪尿中,15N丰度在不同组分和形态氮素中的分布并不相同,牛尿氮的15N丰度低于牛粪氮,矿质态和易于矿化态氮的15N丰度低于不易矿化态氮。 相似文献
129.
本文旨在深入了解植物体对硫素的吸收方式及转运机制,归纳了近年来关于硫素对植物的重要性、植物缺硫的症状、植物对硫吸收和转运的机理,着重分析了硫酸盐的转运机制,硫酸盐进入植物体内经过活化、还原和半胱氨酸的合成过程,总结了国内外关于硫酸盐在植物体内部的变化、各种存在形式的利用机制,指出该领域仍存在的一些问题以及未来的研究侧重点,为相关研究奠定基础。 相似文献
130.
Nutritional characteristics of the leaves of native plants growing in adverse soils of humid tropical lowlands 总被引:3,自引:0,他引:3
Osaki M Watanabe T Ishizawa T Nilnond C Nuyim T Shinano T Urayama M Tuah SJ 《Plant foods for human nutrition (Dordrecht, Netherlands)》2003,58(2):93-115
Acid sulfate, peat, sandy podzolic, and saline soils are widely distributed inthe lowlands of Thailand and Malaysia. The nutrient concentrations in theleaves of plants grown in these type of soils were studied with the aim ofdeveloping a nutritional strategy for adapting to such problem soils. In sagoand oil palms that were well-adapted to peat soil, the N, P, and Kconcentrations were the same in the mature leaves, while the Ca, Mg, Na,and Fe concentrations were higher in the mature leaves of the oil palm thanof the sago palm. Melastoma malabathricum and Melaleuca cajuputi plantsthat were well-adapted to low pH soils, peat, and acid sulfate soils were alsostudied. It was observed that a high amount of Al accumulated in the M.marabathricum leaves, while Al did not accumulate in M. cajuputi leaves.M. cajuputi plants accumulated large amounts of Na in their leaves or stemsregardless of the exchangeable Na concentration in the soil, while M.malabathricum that was growing in saline-affected soils excluded Na.Positive relationships between macronutrients were recognized between Pand N, between K and N, and between P and K. Al showed antagonisticrelationships with P, K, Ca, Mg, Fe, Zn, Cu, and Na. Na also showedantagonistic relationships with P, K, Zn, Mn, Cu, and Al. Fe showed weakantagonistic relationships with Zn, Mn, Cu, and Al. 相似文献