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   4620篇
  免费   69篇
  国内免费   159篇
林业   187篇
农学   651篇
基础科学   48篇
  220篇
综合类   1212篇
农作物   2356篇
水产渔业   39篇
畜牧兽医   82篇
园艺   13篇
植物保护   40篇
  2024年   8篇
  2023年   15篇
  2022年   28篇
  2021年   43篇
  2020年   42篇
  2019年   82篇
  2018年   28篇
  2017年   147篇
  2016年   200篇
  2015年   148篇
  2014年   129篇
  2013年   165篇
  2012年   244篇
  2011年   354篇
  2010年   264篇
  2009年   359篇
  2008年   243篇
  2007年   376篇
  2006年   279篇
  2005年   229篇
  2004年   165篇
  2003年   122篇
  2002年   110篇
  2001年   113篇
  2000年   99篇
  1999年   103篇
  1998年   102篇
  1997年   112篇
  1996年   75篇
  1995年   84篇
  1994年   71篇
  1993年   66篇
  1992年   58篇
  1991年   55篇
  1990年   52篇
  1989年   43篇
  1988年   20篇
  1987年   5篇
  1986年   5篇
  1985年   2篇
  1984年   1篇
  1979年   1篇
  1955年   1篇
排序方式: 共有4848条查询结果,搜索用时 31 毫秒
971.
《Plant Production Science》2013,16(4):331-337
Abstract

Days from full maturity to combine harvest maturity (DFC) is a major concern in combine harvesting of soybeans (Glycine max (L.)), especially in northern Japan, which has a short harvesting period. The combine harvest maturity, which was defined as the day at which the moisture content of the stem reached 30%, was analyzed using 7 soybean varieties for 3 yr in Hokkaido. There were significant differences in DFC among varieties (12 to 31 d) and among the 3 yr (16 to 25 d). DFC was closely associated with dry matter partitioning to stem (DMPS) at full maturity, that is, high DMPS increased DFC. The relationship between DMPS and DFC was examined by pod removal experiments conducted for 2 yr. In the soybean plants with high DMPS pod removal increased the stem desiccation period and DFC. These results indicated that DMPS at full maturity is an informative indicator for predicting the harvest maturity in the combine harvesting system.  相似文献   
972.
以大豆分离蛋白为试验材料,优化糖基化大豆分离蛋白制备工艺并研究经过葡萄糖处理对大豆分离蛋白溶解度、凝胶强度、乳化性以及热稳定方面的影响。结果表明:糖基化大豆分离蛋白最佳制备工艺为反应温度69.49℃、反应时间46.64 min、糖的添加量10.64%,凝胶强度最高为76.03;在相同p H下,经葡萄糖处理后的大豆分离蛋白溶解度较大,沉淀较少,而未糖基化的大豆分离蛋白沉淀量增加。糖基化处理的大豆分离蛋白乳化稳定性(emulsifying stability,ES)和热稳定性均有所增强。糖基化改性过程可显著提高大豆分离蛋白的溶解性和乳化性能,这为拓宽其在食品工业中的应用提供了理论基础。  相似文献   
973.
Abstract

Bragg soybeans [Glycine max. (L. ) Merill] were grown under field conditions near Sanford, Florida on a tile‐drained Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Haplaquod). The objectives were: 1) to assess the K and P fertilizer requirements of soybeans grown in central Florida 2) to correlate soil and tissue nutritional levels with extractable soil nutrients and 3) to assess the influence of K application time on yield.

Experimental treatments were four K rates (0, 50, 100, and 200 kg K/ha), three P rates (0, 25, and 50 kg P/ha), and two sidedress K rates (0 and 50 kg K/ha) at early bloom. Treatments were arranged in a randomized complete block design and replicated four times.

Yield increased with each increase in applied K. Statistical maximum yield was obtained on plots which contained 103 ppm double‐acid extractable K during the pod‐filling stage of growth. Tissue K at early bloom exceeded 2.85% at maximum statistical yield. Potassium applied broadcast at early bloom did not significantly influence yield.

This soil contained approximately 390 ppm double‐acid extractable P prior to P application. No significant yield response to applied P was observed, indicating that the original extractable P content of the soil was adequate for the yield level obtained.

The quadratic regression of the ratio equivalents of double‐acid extractable K:Ca + Mg on the same ratio for the plant tissue is highly significant. This expression was a good predictor of tissue accumulation of these nutrients in that the coefficient for determination was 0.68.  相似文献   
974.
辽豆34是辽宁省农业科学院作物研究所选育的高产、优质、抗病、适应性广的大豆新品种,分别于2011和2015年通过辽宁省和国家农作物品种审定委员会审定。适于在辽宁省中部和南部、山西中部和东南部、宁夏中部和北部及甘肃中部等地区大面积推广种植。  相似文献   
975.
大豆转化过程中的褐化现象研究   总被引:5,自引:1,他引:4  
由大豆愈伤组织所产生的酚类物质可诱发组织产生褐化,并严重影响大豆离体培养时植株的转化率。本文以东农50为试验材料,研究了不同外植体和不同添加剂对抑制褐化的作用。结果表明,子叶节和胚尖作为外植体褐化率较低;L-半胱氨酸和AgNO3对大豆抑制褐化效果明显。  相似文献   
976.
《Plant Production Science》2013,16(4):374-382
Abstract

Soybean yield is low in the fields with a low groundwater level during summer due to drought stress. By raising the groundwater level using Farm-Oriented Enhancing Aquatic System (FOEAS) the yield of soybean cultivar Sachiyutaka can be increased, but not that of Fukuyutaka. Here, we examined the effect of the groundwater level on root growth and its dynamics in these two cultivars. Three of the four experiments demonstrated that root elongation ceased just below groundwater level in both cultivars. However, when the groundwater level was kept at 35 cm or deeper, the root growth at an early growth stage was more vigorous at a deeper layer in Fukuyutaka than in Sachiyutaka, but at the mid-growth stage root growth in Sachiyutaka became similar to or exceeded that of Fukuyutaka. These results indicated that the optimum control technique for the groundwater level differed with the cultivar. The groundwater level for Sachiyutaka should be kept relatively high at an early growth stage. Further studies will be needed to clarify the optimum control technique for maximizing the yield of Fukuyutaka that have a fast root growth at an early growth stage.  相似文献   
977.
A new strain of Tobacco mosaic virus (TMV) was isolated from soybean (Glycine max) in India (TMV-SoyIn). It produced puckering symptoms on inoculated soybean cultivars, JS-20-30 and JS 93-05, and severe necrotic spots on inoculated leaves of Nicotiana tabacum cv. Xanthi, followed by systemic necrotic spots on subsequent leaves as well as greenish mosaic symptoms on the top leaves. In the electron microscope, tobamovirus like particles were observed in soybean leaves and also in the other inoculated host plants. The host reactions revealed that the present isolate was different from the previously described TMV strain of soybean (TMV-S) from Yugoslavia. To confirm the virus identity, the 3′ end of the genome containing the movement protein gene, coat protein and the 3′ untranslated region of the virus isolate was sequenced (1494 nucleotides; JQ895560). Results indicated that the virus associated with soybean crinkle was an isolate of TMV as the present isolate had 94.4–99.7% sequence identity with known TMV isolates. This is the first report of a TMV-strain infecting soybean in India.  相似文献   
978.
丁俊杰 《大豆科学》2012,31(2):327-329
为明确大豆菌核病发生发展中各个时期气象因子的重要性及相关性,对黑龙江省大豆主产区中9个地点的大豆田菌核病病情指数进行调查,收集各地6~8月的平均降水量、平均日照时数和平均气温,在此基础上采用多元回归分析的方法建立回归方程,然后利用通径分析确定影响菌核病发生的主要气象因子。结果表明:8月份平均降水量对大豆菌核病病情指数的影响最为严重,其次为7月份平均日照时数和8月份平均温度;7月份平均日照时数是通过与8月份平均降水量相互作用对大豆菌核病的病情指数产生较大影响。其它因子的直接间接通径系数都很低,对菌核病病情指数的影响不大。因此,在7月份的平均日照时数少,8月份平均降雨量大,并且8月份平均温度适宜的情况下菌核病将发生流行。  相似文献   
979.
采用灰色系统理论中的灰色综合评判方法,对17个大豆区试品种进行了9个主要性状指标的综合分析和评价,最后得出结论为:各性状在评价品种优劣中所占的比重依次为产量>单株粒重>生育日数>百粒重>主茎节数>株高>有效分枝>有效荚数>单株粒数。为大豆新品种的选育和评价提供了依据和方法。  相似文献   
980.
《Journal of plant nutrition》2013,36(7):1383-1402
Abstract

Narrow‐row soybean [Glycine max (L.) Merr.] production in corn [Zea mays L.]–soybean rotations results in various distances of soybean rows from previous corn rows, yet little is known about soybean responses to proximity to prior corn rows in no‐till systems. The objective of this study was to evaluate the impacts of preceding corn rows on potassium (K) nutrition and yield of subsequent no‐till soybeans. Four field experiments involving a corn–soybean rotation were conducted on long‐term no‐till fields with low to medium K levels from 1998 to 2000 near Paris and Kirkton, Ontario, Canada. In the corn year, treatments included K application rate and placement in conjunction with tillage systems or corn hybrids. Before soybean flowering, soil exchangeable K concentrations (0–20 cm depth) in previous corn rows were significantly higher than those between corn rows. At the initial flowering stage, trifoliate leaf K concentrations of soybeans in preceding corn rows were 2.0 to 5.3 g kg?1 higher than those from corresponding plants between corn rows. Yield of no‐till soybeans in previous corn rows increased 10 to 44% compared to those between previous corn rows. Positive impacts of prior corn rows on soil K fertility, soybean leaf K, and soybean yield occurred even when K fertilizer was not applied in the prior corn season. Deep banding of K fertilizer tended to accentuate row vs. between‐row effects on soybean leaf K concentrations in low‐testing soils. Corn row effects on soybeans were generally not affected by either tillage system or corn hybrid employed in the prior corn crop. Potassium management strategies for narrow‐row no‐till soybeans should take the potential preceding corn row impacts on soil K distribution into account; adjustments to current soil sampling protocols may be warranted when narrow‐row no‐till soybeans follow corn on soils with low to medium levels of exchangeable K.  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