全文获取类型
收费全文 | 3569篇 |
免费 | 208篇 |
国内免费 | 393篇 |
专业分类
林业 | 227篇 |
农学 | 394篇 |
基础科学 | 182篇 |
818篇 | |
综合类 | 1569篇 |
农作物 | 317篇 |
水产渔业 | 91篇 |
畜牧兽医 | 201篇 |
园艺 | 109篇 |
植物保护 | 262篇 |
出版年
2024年 | 20篇 |
2023年 | 75篇 |
2022年 | 131篇 |
2021年 | 137篇 |
2020年 | 182篇 |
2019年 | 168篇 |
2018年 | 143篇 |
2017年 | 195篇 |
2016年 | 224篇 |
2015年 | 181篇 |
2014年 | 194篇 |
2013年 | 262篇 |
2012年 | 304篇 |
2011年 | 231篇 |
2010年 | 178篇 |
2009年 | 163篇 |
2008年 | 131篇 |
2007年 | 156篇 |
2006年 | 151篇 |
2005年 | 100篇 |
2004年 | 79篇 |
2003年 | 86篇 |
2002年 | 62篇 |
2001年 | 74篇 |
2000年 | 64篇 |
1999年 | 68篇 |
1998年 | 62篇 |
1997年 | 45篇 |
1996年 | 31篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 44篇 |
1992年 | 26篇 |
1991年 | 27篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1962年 | 2篇 |
排序方式: 共有4170条查询结果,搜索用时 15 毫秒
71.
阐述了“春作——培两优特青早秋制——秋菜”栽培模式的科学依据和优点,并具体提出了几种主要的搭配模式,探讨了每种模式的适应范围、品种搭配、栽培管理技术,强调了培两优特青早秋制要培育双强亲本、灵活调节花期和综合防治稻粒黑粉病等几个技术环节。 相似文献
72.
Judging watermelon quality based on its apparent properties such as size or skin color is difficult. A non-destructive method is employed here, based on vibrational response spectrum, to determine the quality indices of watermelon (Charleston gray). The responses of samples to vibration excitation were recorded by laser Doppler vibrometry (LDV). The phase shift between input and output signals were extracted over a wide frequency range. The total soluble solids (TSS), titratable acidity (TA) and TSS/TA ratio also measured as watermelon quality characters. Stepwise multiple linear regression (SMLR) as well as partial least square regression (PLS) was applied to extracted vibration spectrums to construct prediction models of watermelon quality. The results showed that performance of SMLR models were better than PLS. The determination coefficients (R2) of SMLR validation models were 0.9976, 0.9985 and 0.9542 for TSS, TA and TSS/TA respectively. It is likely that reduction of cell wall materials to soluble solids during ripening process changes viscoelastic properties of watermelon reflected by vibrational response. This study demonstrated the feasibility of mentioned method for predicting the quality of watermelons in an industrial grading system. 相似文献
73.
74.
75.
增产菌对复种燕麦产草量影响的试验 总被引:4,自引:0,他引:4
采用拌种、喷洒和拌种+喷洒3种方法,对临夏县北塬灌区麦后复种燕麦草增产效果进行了初步研究。结果 表明,增产菌对麦后复种燕麦的增产效果极显著(p<0.01),最佳拌种量300 g/hm2,最佳喷洒量300 g/hm2,最佳处 理组合为300 g/hm2拌种+300 g/hm2喷洒。 相似文献
76.
Models predicting the effects of cropping systems on weed demography are important tools for testing new rules for integrated weed management that may reduce the use of herbicides and preserve the biodiversity of agro-ecosystems. Such models already exist for a few species and should now be extended to a larger flora, in order to predict and understand the effects of agricultural practices on the evolution of weed communities. This review analysed the literature from 1973 to 2006, focusing on 45 species, to identify past reasons for choosing particular species when modelling the effects of cropping systems on the processes leading to seedling emergence. The frequency or harmfulness of the species were the main reason for studying them. It appears that the studied species were mainly autumn-emerging in north-western Europe cropping systems and summer-emerging in North America; the effects of deep soil tillage were studied mainly in Europe, as simplified sowing techniques are more often practised in North America. A voluminous literature exists on seed persistence in the soil, dormancy, germination and emergence, but rarely with the attempt of establishing generic relationships between species characteristics and model parameters. Until now, such an approach has been mostly developed in ecological studies. Taxa, as well as ecological preferences, seed size and the relationships of these characteristics with weed emergence model parameters should be considered when selecting a range of species for multi-specific modelling purposes. 相似文献
77.
Field and pot experiments were conducted to evaluate the effect of co-cultivation and crop rotation on the growth and corm rot disease of gladiolus (Gladiolus grandiflorus sect. Blandus) cv. Aarti caused by Fusarium oxysporum f.sp. gladioli (Massey) Snyd. and Hans. In the field experiment, gladiolus was co-cultivated with 10 agricultural/horticultural crops viz. Allium cepa L., Brassica campestris L., Capsicum annuum L., Eruca sativa Mill., Helianthus annuus L., Tagetes erectus L., Zea mays L., Vinca rosea L. and Rosa indica L., in a soil infested with F. oxysporum. All the crops except V. rosea and R. indica reduced disease incidence. The effect of H. annuus and T. erectus was significant and more pronounced than other co-cultivated crops. In general, root and shoot dry biomass, corm fresh weight, number of cormlets and number of flowers per spike decreased as compared to the un-inoculated monoculture gladiolus treatment (negative control) but these parameters enhanced as compared to the F. oxysporum inoculated monoculture gladiolus treatment (positive control). In a pot experiment, all the crops of the field experiment except V. rosea and R. indica were sown in rotation with gladiolus. Pot grown plants of different species were harvested at maturity and the soil was inoculated with F. oxysporum. Gladiolus was cultivated 1 week after inoculation. Disease incidence was significantly suppressed in all the treatments ranging from 29% to 53%. The highest suppression of disease incidence was recorded in T. erectus (53%) followed by B. campestris (49%). The effect of preceding crops on various vegetative parameters was similar in the pot experiment to that of the field experiment. The present study suggests that corm rot disease of gladiolus can be managed by mixed cropping of H. annuus and T. erectus or cultivation of T. erectus and B. campestris in rotation. 相似文献
78.
朱月娥 《中南林业科技大学学报(自然科学版)》2004,24(3):105-108
新一轮的大学英语教学改革正在全国进行.改变对教学翻译的认识,提高教学翻译在大学英语教学中的地位,在大学英语教学中进行切实、有效的教学翻译活动,有利于学生英语综合运用能力的提高和复合型人才的培养. 相似文献
79.
自20世纪80年代起,云南保山潞江坝胡椒种植面积逐渐萎缩,经调查分析,该地区冬春季节低温干旱的气候条件、管理粗放、连作障碍等导致胡椒旱衰和死亡是种植面积大幅萎缩的主要原因;作者在此基础上提出了该区胡椒产业发展的建议。 相似文献
80.
北京地处暖温带半湿润季风气候区,地带性植被是暖温带落叶阔叶林。由于长期受 相似文献