全文获取类型
收费全文 | 8278篇 |
免费 | 545篇 |
国内免费 | 980篇 |
专业分类
林业 | 902篇 |
农学 | 1662篇 |
基础科学 | 363篇 |
1287篇 | |
综合类 | 3315篇 |
农作物 | 533篇 |
水产渔业 | 317篇 |
畜牧兽医 | 642篇 |
园艺 | 459篇 |
植物保护 | 323篇 |
出版年
2024年 | 46篇 |
2023年 | 145篇 |
2022年 | 287篇 |
2021年 | 297篇 |
2020年 | 323篇 |
2019年 | 361篇 |
2018年 | 239篇 |
2017年 | 372篇 |
2016年 | 475篇 |
2015年 | 371篇 |
2014年 | 498篇 |
2013年 | 541篇 |
2012年 | 702篇 |
2011年 | 656篇 |
2010年 | 544篇 |
2009年 | 480篇 |
2008年 | 401篇 |
2007年 | 434篇 |
2006年 | 377篇 |
2005年 | 344篇 |
2004年 | 256篇 |
2003年 | 246篇 |
2002年 | 167篇 |
2001年 | 177篇 |
2000年 | 146篇 |
1999年 | 131篇 |
1998年 | 100篇 |
1997年 | 98篇 |
1996年 | 85篇 |
1995年 | 64篇 |
1994年 | 71篇 |
1993年 | 64篇 |
1992年 | 60篇 |
1991年 | 49篇 |
1990年 | 49篇 |
1989年 | 28篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1962年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有9803条查询结果,搜索用时 390 毫秒
11.
Indices of the tomato seedling quality maintenance level after production before field planting were studied through simulated experiments, small--scale operation, indoor analyses and measurements, and field observation. The results showed that under simulated shipping and storage conditions, seedling quality change following different durations (days) of shipping and storage was correlated significantly or even very significantly with certain physiological and morphological indices. With various measured indices following different periods of shipping and storage treatment subjected to multinomial successive regressive correlation analysis, the principal factors influencing seedling quality maintenance level are identified to be chlorophyll content→dry short weight→ leaf freshness index in order of their importance. Significance analysis with multinomial fitted equation indicated that correlations between any one of above three factors and the growth index after field planting reached very significant difference level. 相似文献
12.
北京植物园引种日本梅花品种初探 总被引:4,自引:3,他引:1
北京植物园 1998年从日本引进梅花品种 39个。通过几年的观察、驯化 ,初步优选出可在北京地区生长的梅花品种 2 9个。 2 0 0 3年冬用电导法测定不同品种的抗寒力。对日本梅花品种在北京地区的栽培、养护及应用进行了初步探讨。 相似文献
13.
14.
Provision of feed supplies for the rapidly growing livestock population is essential in West Asia. Shortages can be alleviated by growing forage crops in the existing fallow lands.
Narbon vetch (Vicia narbonensis L.) is a leguminous species with high yield potential, drought tolerance and cold resistance. It could be used for grain and straw production as source for animal feed in dry areas. It is good source of protein with seeds contain 28 % protein yielding 364 kg per hectare protein, whilst straw contains 9 % protein and yields a similar amounts of digestible protein per hectare.
Nine promising lines of Narbon vetch developed at ICARDA were tested at two sites over four years under rainfed conditions. Since climatic conditions were considered to be of considerable importance, each site in each year was treated as a separate environment to give eight environments with annual rainfall varied from 195 to 504 mm.
Narbon vetch possessed high seedling vigour with rapid winter growth and negligible cold damage. Grain yield varied form 0.47 to 1.90 t/ha, with a harvest index varying from 30 to 40 %. The data indicated that below 300 mm rainfall the grain yield varied from 0.47 t/ha when rain fall was 195 mm to 1.4 t/ha when rainfall was 245 mm. Most of the lines had wide adaptation to dry areas in terms of both grain yield and stability. Climate, except early spring rains had little effect on biological and grain yields. 相似文献
Narbon vetch (Vicia narbonensis L.) is a leguminous species with high yield potential, drought tolerance and cold resistance. It could be used for grain and straw production as source for animal feed in dry areas. It is good source of protein with seeds contain 28 % protein yielding 364 kg per hectare protein, whilst straw contains 9 % protein and yields a similar amounts of digestible protein per hectare.
Nine promising lines of Narbon vetch developed at ICARDA were tested at two sites over four years under rainfed conditions. Since climatic conditions were considered to be of considerable importance, each site in each year was treated as a separate environment to give eight environments with annual rainfall varied from 195 to 504 mm.
Narbon vetch possessed high seedling vigour with rapid winter growth and negligible cold damage. Grain yield varied form 0.47 to 1.90 t/ha, with a harvest index varying from 30 to 40 %. The data indicated that below 300 mm rainfall the grain yield varied from 0.47 t/ha when rain fall was 195 mm to 1.4 t/ha when rainfall was 245 mm. Most of the lines had wide adaptation to dry areas in terms of both grain yield and stability. Climate, except early spring rains had little effect on biological and grain yields. 相似文献
15.
16.
大豆室内耐冷筛选及其在田间的应用研究 总被引:4,自引:1,他引:3
本试验把生长箱大豆耐低温萌发筛选与田间早春播研究相结合,验证耐低温发芽的可靠性。在实验室,萌发期表现抗冷的大豆,田间出昔期仍表现抗冷或较抗冷。实验表明,大豆出苗的生物学最低温度平均为7.1℃,所需有效积温136℃。地温的高低直接影响大豆早春出苗的多寡,两者呈密切的正相关。黄、青、黑豆中,以黑豆抵抗早春不良气候条件的能力最强。 相似文献
17.
钙对苜蓿幼苗抗寒性及相关生理指标影响的研究 总被引:24,自引:4,他引:20
先用50mmol/L CaCl2浸泡图牧吉苜蓿,公农一号苜蓿种子,蒸馏水处理作对照,之后将其幼苗放在低温下胁迫。结果表明:Ca^2 不但能提高图牧吉苜蓉幼苗的抗寒性,而且,也能提高公农一号苜蓿幼苗的抗寒性,同时,图牧吉苜蓿,公农一号苜蓿的超氧化物歧化酶,过氧化物酶,过氧化氢酶等酶活性及脯氨酸与抗坏血酸含量也得到提高。由此推测,Ca^2 提高图牧吉苜蓿,公农一号苜蓿幼苗的抗寒性可能与Ca^2 提高其超氧化物歧化酶,过氧化物酶,过氧化氢酶等酶活性及脯氨酸与抗坏血酸含量有关。 相似文献
18.
19.
20.