全文获取类型
收费全文 | 1530篇 |
免费 | 54篇 |
国内免费 | 165篇 |
专业分类
林业 | 74篇 |
农学 | 213篇 |
基础科学 | 35篇 |
172篇 | |
综合类 | 580篇 |
农作物 | 205篇 |
水产渔业 | 113篇 |
畜牧兽医 | 61篇 |
园艺 | 276篇 |
植物保护 | 20篇 |
出版年
2024年 | 14篇 |
2023年 | 23篇 |
2022年 | 48篇 |
2021年 | 54篇 |
2020年 | 42篇 |
2019年 | 63篇 |
2018年 | 50篇 |
2017年 | 58篇 |
2016年 | 67篇 |
2015年 | 49篇 |
2014年 | 85篇 |
2013年 | 104篇 |
2012年 | 112篇 |
2011年 | 129篇 |
2010年 | 106篇 |
2009年 | 87篇 |
2008年 | 68篇 |
2007年 | 103篇 |
2006年 | 79篇 |
2005年 | 67篇 |
2004年 | 36篇 |
2003年 | 39篇 |
2002年 | 23篇 |
2001年 | 26篇 |
2000年 | 20篇 |
1999年 | 27篇 |
1998年 | 14篇 |
1997年 | 16篇 |
1996年 | 20篇 |
1995年 | 23篇 |
1994年 | 17篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有1749条查询结果,搜索用时 15 毫秒
1.
2.
3.
大蒜新品种成蒜早2号和成蒜早3号的选育 总被引:1,自引:1,他引:1
成蒜早2号和成蒜早3号是从温江蒜的自然变异株中,经系统选育而成的早熟新品种.成蒜早2号从播种到蒜薹始收需153~180 d(天),平均单薹质量12.7 g,单头质量10.7 g,多数蒜头由6~9瓣组成,蒜瓣紧密抱握蒜薹轴,一般蒜薹和蒜头产量分别为340和350 kg·(667 m2)-1,抽薹比温江蒜早,抗寒力比温江蒜弱;成蒜早3号从播种到蒜薹始收需153~186 d(天),平均单薹质量和单头质量分别为14.5和12.0 g,多数蒜头由5~8瓣组成.一般蒜薹和蒜头产量分别为320和410kg·(667 m2)-1,抽薹比温江蒜早,抗寒力与温江蒜相当. 相似文献
4.
5.
早熟、优质、耐贮梨新品种新梨7号选育研究 总被引:7,自引:0,他引:7
以库尔勒香梨为母本,早酥梨为父本,有性杂交选育成新梨7号品种。该品种同时兼备优质、早熟与耐贮藏性;该品种遗传了父本的早熟性,比父本更早熟15~20d,盛花期~果实可食期约80~95d,属于早熟品种;且遗传了母本品质性状的质地酥脆、耐贮、清香、阳面红晕,比母本果个大,果心小。果柄木质化,丰产抗风。新梨7号果实贮藏期的可溶性固形物、果实重量、果实硬度和果实前期腐烂率的变化与库尔勒香梨基本相似,但耐热能力高于母本。凡适宜香梨、早酥、苹果梨和巴梨种植的地区,都适宜该品种的种植。 相似文献
6.
7.
8.
早熟薄皮甜瓜新品种香瑞1号的选育 总被引:1,自引:1,他引:0
香瑞1号是黑龙江省青冈县瑞雪农业有限责任公司以NY-99为父本、RX-99为母本选育的早熟薄皮甜瓜新品种.全生育期68d,果实发育期27 d.子、孙蔓均可结瓜.果实长圆形,果皮黄白色,果实大小整齐,外形美观,不裂果;中心可溶性固形物14%,品质优.单果质量500~600g,667m2产量3 500 kg左右.田间表现对... 相似文献
9.
10.
Trees are the dominant species in agroforestry systems, profoundly affecting the performance of understory crops. Proximity to trees is a key factor in crop performance, but rather little information is available on the spatial distribution of yield and yield components of crop species under the influence of trees in agroforestry systems. Also, little information is available on how crop density may be exploited to optimize the yield in such systems. Here we studied the performance of cotton in jujube/cotton agroforestry. Field experiments were conducted in 2012 and 2013 in Hetian, Xinjiang, China. Cotton was grown at a row distance of 60 cm in three densities, 13.5, 18.0 and 22.5 plants m−2 in six m wide paths between tree lines in a jujube plantation. Plant density affected both cotton aboveground dry matter and yield significantly. The highest yield was attained at the intermediate density of 18.0 plants m−2 (20.0 plants m−2 corresponding in sole cotton), lower than the optimal density in sole cotton (25.0 plants m−2). Yield at the lower density was constrained by the low number of bolls per m2 as a direct consequence of the low density, whereas at the high plant density yield was constrained by a lower allocation of assimilates to cotton seed and lint, as a consequence of intraspecific and interspecific competitions. There were strong gradients in yield and yield components in relation to the distance from the tree rows. Leaf area and total dry matter of cotton in rows close to the tree lines were reduced, especially in the rows next to the trees. Moreover, biomass allocation to cotton fruits was reduced in these rows. Competitive influences from the trees on cotton performance extended two rows deep in a six-year old jujube stand, and even three rows deep in a seven-year old stand. Shading effects on cotton yield were compensated by increasing plant density as a result of greater boll numbers per unit ground area. Data from this study help guide the design of optimal plant density of cotton in jujube plantations and give insight in the spatial distribution and dynamics of competitive effects in agroforestry systems in general. 相似文献