全文获取类型
收费全文 | 10399篇 |
免费 | 542篇 |
国内免费 | 976篇 |
专业分类
林业 | 956篇 |
农学 | 1015篇 |
基础科学 | 771篇 |
1343篇 | |
综合类 | 4107篇 |
农作物 | 648篇 |
水产渔业 | 418篇 |
畜牧兽医 | 1752篇 |
园艺 | 459篇 |
植物保护 | 448篇 |
出版年
2024年 | 51篇 |
2023年 | 192篇 |
2022年 | 383篇 |
2021年 | 440篇 |
2020年 | 430篇 |
2019年 | 378篇 |
2018年 | 271篇 |
2017年 | 470篇 |
2016年 | 304篇 |
2015年 | 503篇 |
2014年 | 507篇 |
2013年 | 584篇 |
2012年 | 762篇 |
2011年 | 825篇 |
2010年 | 784篇 |
2009年 | 739篇 |
2008年 | 682篇 |
2007年 | 627篇 |
2006年 | 555篇 |
2005年 | 528篇 |
2004年 | 283篇 |
2003年 | 250篇 |
2002年 | 234篇 |
2001年 | 183篇 |
2000年 | 197篇 |
1999年 | 132篇 |
1998年 | 99篇 |
1997年 | 79篇 |
1996年 | 66篇 |
1995年 | 70篇 |
1994年 | 51篇 |
1993年 | 64篇 |
1992年 | 42篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 21篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1962年 | 2篇 |
1958年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
不同籼稻颖果发育及其结构与品质性状 总被引:5,自引:2,他引:5
比较了两个籼稻品种颖果的发育,籽粒的主要品质性状以及胚乳淀粉体的大小、形状、结构等特性。结果表明: 扬稻6号的主要品质性状优于湘早籼33;在开花后前期扬稻6号干物质积累速率较慢,但在后期较快,淀粉充实度较高; 淀粉胚乳细胞内存在两种淀粉体,即单粒淀粉体,直径2.4~8.0 μm,平均4.7 μm;复合淀粉体,即由多个单粒淀粉体结合而成,直径5.7~19.5 μm,平均9.7 μm。湘早籼33单粒淀粉体多数为椭圆形或圆球形,大小差异较大,排列疏松,变异系数较大;扬稻6号胚乳单粒淀粉体基本为晶体多面形,发育良好,大小较为一致,排列紧密,变异系数较小。胚乳背部淀粉体的发育和排列结构优于腹部和中部。胚乳垩白的出现是由于淀粉体发育不良、排列疏松所致,而淀粉体的充实又与灌浆物质的输入途径紧密相关。 相似文献
93.
94.
95.
谈高校管理中的激励技术 总被引:2,自引:0,他引:2
在高校的管理过程中,科学地选择激励技术是调动教职工积极性,发挥教职工创造性,质量和办学水平的有效的一从六个方面对此了探讨。 相似文献
96.
97.
甘肃冬小麦品种品质性状分析与评价 总被引:1,自引:0,他引:1
为了全面掌握甘肃冬小麦的品质状况,以甘肃省冬小麦主产区100个小麦品种(系)为供试材料,采用AACC国标分析方法对其籽粒蛋白质品质、磨粉品质及面团流变学特性进行检测和分析。结果表明,甘肃冬小麦品种具有较高的蛋白质、湿面筋含量和吸水率,但面筋强度较低,形成时间、稳定时间较短,最大抗延阻力和拉伸面积较小,加工品质与国内主产麦区存在一定的差距,商品率低。甘肃冬小麦品种整体以中筋小麦为主。建议在今后育种过程中加强对品质性状的选择,以进一步提升小麦品种质量水平。 相似文献
98.
不同供氮水平对西瓜产量和品质的影响 总被引:6,自引:0,他引:6
以京欣1号为材料,采用随机区组设计,以尿素为肥源,设计5个不同氮水平,探讨不同供氮水平对西瓜产量和品质的影响,结果表明:在氮适量的土壤上增施氮肥,能增加单株西瓜个数和单瓜质量,提高产量,对提高单个西瓜质量更为突出。在一定的范围内,西瓜产量随着氮肥用量的上升而增加,但当每公顷纯氮用量达到360 kg以后,西瓜产量开始呈下降趋势,继续增加用量,产量急剧下降;在纯氮用量0~240 kg/hm2时,对可溶性糖含量影响很小,而继续增加氮用量,即当纯氮用量为360~480 kg/hm2时,可溶性糖含量明显上升;施用氮肥不同程度提高了西瓜维生素C含量;在纯氮用量0~240 kg/hm2时,硝酸盐的含量逐渐增加,之后却有下降趋势。综合产量和品质,在本试验条件下,N4处理即纯氮用量360 kg/hm2为较合适的用量。 相似文献
99.
The availability of nitrogen (N) contained in crop residues for a following crop may vary with cultivar, depending on root traits and the interaction between roots and soil. We used a pot experiment to investigate the effects of six spring wheat (Triticum aestivum L.) cultivars (three old varieties introduced before mid last century and three modern varieties) and N fertilization on the ability of wheat to acquire N from maize (Zea mays L.) straw added to soil. Wheat was grown in a soil where 15N‐labeled maize straw had been incorporated with or without N fertilization. Higher grain yield in three modern and one old cultivar was ascribed to preferred allocation of photosynthate to aboveground plant parts and from vegetative organs to grains. Root biomass, root length density and root surface area were all smaller in modern than in old cultivars at both anthesis and maturity. Root mean diameter was generally similar between modern and old cultivars at anthesis but was greater in modern than in old cultivars at maturity. There were cultivar differences in N uptake from incorporated maize straw and the other N sources (soil and fertilizer). However, these differences were not related to variation in the measured root parameters among the six cultivars. At anthesis, total N uptake efficiencies by roots (total N uptake per root weight or root length) were greater in modern than in old cultivars within each fertilization level. At maturity, averaged over fertilization levels, the total N uptake efficiencies by roots were 292?336 mg N g?1 roots or 3.2?4.0 mg N m?1 roots for three modern cultivars, in contrast to 132?213 mg N g?1 roots or 0.93?1.6 mg N m?1 roots for three old cultivars. Fertilization enhanced the utilization of N from maize straw by all cultivars, but root N uptake efficiencies were less affected. We concluded that modern spring wheat cultivars had higher root N uptake efficiency than old cultivars. 相似文献
100.
In intensive and large-scale livestock breeding, how to evaluate welfare of each individual effectively has become one hotspot of welfare breeding.In this study, a remote monitor system based on computer vision technology and wireless sensor networks was proposed.In the system, pig videos in the piggery were captured by IP cameras and transmitted remotely to PC systems for objects tracking and trajectory extraction, and the piggery environmental data such as temperature, humidity and harmful gases were collected by wireless sensor networks(WSN) nodes.Traditional Camshift tracking algorithm was improved.The average root mean square errors of traditional and improved algorithm were 78.07 and 32.29, indicating the improved algorithm reduced error and improved tracking stability.The results of the real-time monitoring of environmental parameters by WSN showed that the hydrogen and ammonia concentrations, and the ambient temperature were all kept in the normal range, while the carbon dioxide concentration was exceeded, and the air humidity was slightly high.Through data mining, precise welfare monitoring and breeding management were realized. 相似文献