全文获取类型
收费全文 | 47540篇 |
免费 | 2323篇 |
国内免费 | 4768篇 |
专业分类
林业 | 2362篇 |
农学 | 6108篇 |
基础科学 | 1983篇 |
7570篇 | |
综合类 | 21256篇 |
农作物 | 4904篇 |
水产渔业 | 1598篇 |
畜牧兽医 | 5287篇 |
园艺 | 1865篇 |
植物保护 | 1698篇 |
出版年
2024年 | 342篇 |
2023年 | 1005篇 |
2022年 | 1778篇 |
2021年 | 2132篇 |
2020年 | 2077篇 |
2019年 | 2235篇 |
2018年 | 1518篇 |
2017年 | 2403篇 |
2016年 | 2718篇 |
2015年 | 2119篇 |
2014年 | 2849篇 |
2013年 | 3091篇 |
2012年 | 3771篇 |
2011年 | 3629篇 |
2010年 | 2802篇 |
2009年 | 2614篇 |
2008年 | 2257篇 |
2007年 | 2375篇 |
2006年 | 2021篇 |
2005年 | 1750篇 |
2004年 | 1430篇 |
2003年 | 1105篇 |
2002年 | 832篇 |
2001年 | 798篇 |
2000年 | 644篇 |
1999年 | 589篇 |
1998年 | 495篇 |
1997年 | 470篇 |
1996年 | 385篇 |
1995年 | 413篇 |
1994年 | 314篇 |
1993年 | 313篇 |
1992年 | 257篇 |
1991年 | 242篇 |
1990年 | 199篇 |
1989年 | 169篇 |
1988年 | 119篇 |
1987年 | 121篇 |
1986年 | 64篇 |
1985年 | 29篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 10篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1962年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Two-year field trials with winter wheat cultivars Batis and Toronto were conducted in Southern Bavaria, Germany, to investigate the possible causes of cultivar differences in response to N supply varying in total amount and time of application. Cultivar-related differences in grain yields were observed in treatments with low and medium N supply. High doses of N supply resulted in grain yield adjustment or grain yield advantage for cv. Toronto. The results of this study revealed a consistent, genotypic pattern in response to N fertilization in spite of strong seasonal effects. Systematic modifications in canopy growth rates in response to N supply were of particular relevance and a main factor for differences in tillering intensity resulting in modified stand densities. In the present study, cultivar differences in spike development and interactions with N supply related more to abortion than to initiation processes for number of spikelets and number of flowers per spikelet. High grain density (grains per m2) of cv. Toronto was evident during reproduction stages even under conditions of medium N supply. However, decreased growth rates during the later part of grain filling in combination with low 1000 grain weight, which was barely modified by N fertilization, allowed only partial utilization of this potential. It is assumed that sink limitations were of particular relevance for grain yield development in cv. Toronto, while cv. Batis combined a less intense response to N supply with more stability in the development of grain yield components. 相似文献
93.
黄麻(新、引进)品种在闽南地区的产量(鉴定)试验 总被引:2,自引:0,他引:2
通过对中国农科院麻类所新选育的3个黄麻圆果种和12个国外引进的黄麻优异品种进行2002-2005年品种比较试验,结果表明:C90-2、C90-6、C89-6比对照种粤圆五号增产14.97%-19.34%,均达极显著水平。O-3、O-1、O-3(红茎)比对照种宽叶长果增产32.02%-34.21%,均达极显著水平。O-4(Ⅱ)比对照种增产12.28%达显著水平。C-1、C-5比对照种粤圆五号增产11.90%和7.82%。且主要经济性状优良,抗病力强。黄麻品种C90-2、C90-6、C89-6、O-3、O-1、O-3(红茎)、0-4(Ⅱ)、C-1和C-5适合于福建闽南麻区推广种植。 相似文献
94.
采用A-PAGE和SDS-PAGE聚丙烯酰胺凝胶电泳方法,对远缘组合分离出来的节燕98-2类型入选11个遗传性基本稳定的具有高产、多抗的小麦株系的醇溶蛋白和高分子量谷蛋白亚基进行了分析.结果表明,在A-PAGE电泳分析中,11个供试株系具有11种不同的醇溶蛋白带型.在SDS-FAGE电泳分析中,出现了7种不同的高分子量谷蛋白亚基(HMW-GS)及6种亚基组合类型,优质亚基及亚基组合所占的比例较少,品质评分偏低,其变幅为5~8分,平均为6.36分.但在所分析的材料中,出现了一个少见的特殊亚基:2 10 12.并研究了这些HMW-GS和组合频率及特点.11个株系中7个具有45 10优质亚基和2个具有2*亚基,它们可供小麦优质育种利用.研究表明,通过远缘杂交能够选育出具有高产、抗病和优质的小麦新材料. 相似文献
95.
96.
97.
“复激保果剂”在杂交水稻制种上应用技术总结 总被引:1,自引:0,他引:1
复激保累剂,在杂交稻制种上使用,能促使花器发育良好,调节父母本花期,提高结实率,增加每穗实粒和粒重,提高产量。且成本低,有显著的经济效益。 相似文献
98.
99.
采用迅速烘干、太阳晒干和缓慢烘干3种处理对云南温带21个牧草品种的鲜草进行干燥处理,分别测定干草的营养成分。结果表明:以干草的粗蛋白含量为指标,干燥方法以迅速烘干为佳,其次是太阳晒干,最差是缓慢烘干;从干草的粗脂肪考虑,其变化无规律,因牧草品种的不同而不同;其余指标变化不大。 相似文献
100.
Field studies were undertaken to explore the weed management strategies for transplanted and direct wet-seeded rice in the Dera Ismail Khan district of North-west Frontier Province, Pakistan. The experimental design was a randomized complete block with a split plot arrangement. The main plots consisted of two planting techniques (transplantation and direct seeding), while weed control practises assigned to the subplots included the use of the granular herbicide Sunstar 15WG (ethoxy sulfuron), Machete 60EC (butachlor), conventional hand weeding, and the weedy check (untreated control). Data were recorded on weed dynamics and the agronomic parameters of the rice crop. Economic analyses on the data were also run. The weed density and biomass were lower in the transplantation plots than the direct-seeding plots. The herbicides ethoxy sulfuron and butachlor reduced the density over the weedy check, with a density comparable to hand weeding in 2002, but slightly higher in 2003. As a result of weed management by hand weeding and herbicides, the paddy yield and its components were significantly higher for the transplanted method compared to the direct-seeded method. The comparable yield of herbicides with hand weeding offers an option for the use of herbicides as an alternative management tool. In light of our findings, it is concluded that for good economic returns, rice crops may be transplanted rather than direct-seeded. The herbicides ethoxy sulfuron and butachlor offer a weed control cover comparable with hand weeding under the transplantation method, while butachlor is good for controlling weeds even under the direct-seeded conditions in the agroclimatic conditions of the area. 相似文献