全文获取类型
收费全文 | 16238篇 |
免费 | 934篇 |
国内免费 | 1780篇 |
专业分类
林业 | 1125篇 |
农学 | 903篇 |
基础科学 | 688篇 |
1657篇 | |
综合类 | 7832篇 |
农作物 | 1165篇 |
水产渔业 | 726篇 |
畜牧兽医 | 2925篇 |
园艺 | 1205篇 |
植物保护 | 726篇 |
出版年
2024年 | 131篇 |
2023年 | 333篇 |
2022年 | 793篇 |
2021年 | 780篇 |
2020年 | 720篇 |
2019年 | 701篇 |
2018年 | 478篇 |
2017年 | 780篇 |
2016年 | 539篇 |
2015年 | 807篇 |
2014年 | 845篇 |
2013年 | 1022篇 |
2012年 | 1393篇 |
2011年 | 1393篇 |
2010年 | 1439篇 |
2009年 | 1211篇 |
2008年 | 1265篇 |
2007年 | 1099篇 |
2006年 | 850篇 |
2005年 | 729篇 |
2004年 | 439篇 |
2003年 | 313篇 |
2002年 | 256篇 |
2001年 | 258篇 |
2000年 | 226篇 |
1999年 | 62篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 2篇 |
1994年 | 8篇 |
1993年 | 16篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1965年 | 1篇 |
1962年 | 2篇 |
1956年 | 5篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Cong HUANG Kun LANG Wan-qiang QIAN Shu-ping WANG Xiao-mei CAO Rui HE An-ran ZHAN Meng-yao CHEN Nian-wan YANG Fei LI 《农业科学学报》2021,20(1):191-200
Invasive alien species(IAS) are species whose introduction to areas outside of their native range cause harm to economics, biodiversity, and the environment. Understanding the genetic basis of invasiveness is critical for preventing invasion by an alien species and managing IAS with eco-friendly control methods. In addition, uncovering the genomic features of IAS is essential for accurately predicting invasiveness. However, even though increasing efforts have been devoted to sequencing the genomes of IAS, there is still not an integrated genome database for the invasive biology community. Here, we first determined a list of invasive plants and animals by mining references and databases. Then, we retrieved the genomic and gene data of these IAS, and constructed a database, Invasion DB. Invasion DB encompasses 131 IAS genomes, 76 annotated IAS assemblies, and links these data to conventional functions such as searching for gene coding sequences and Pfam, KEGG, NR annotations, BLAST server, JBrowse, and downloads services. Next, we analyzed 19 invasivenessrelated gene families which confer invasiveness in insects. To study the roles of noncoding RNA in invasiveness, we also annotated 135 494 mi RNAs, 89 294 r RNAs, and 2 671 941 t RNAs from these IAS. In summary, Invasion DB is useful for studying the invasiveness at the genomic level, and thus helps to develop novel management strategies to control IAS. 相似文献
162.
163.
164.
采用鸡肝酯酶对不同浓度的氰戊菊酯农药进行了催化水解,并通过pH-stat法优化了水解条件.结果表明,在pH 8.0,温度55℃的条件下,酶催化反应速度较大.在该反应条件下,分析了农药浓度(1/x)与酶解反应初速度(1/y)之间的关系,发现在0.05~2.00 mg·L-1农药浓度范围内,两者的关系曲线为y=0.0723... 相似文献
165.
10种杀菌剂对马铃薯晚疫病的防治效果与经济效益评价 总被引:5,自引:0,他引:5
选择72%霜脲·锰锌(克露)可湿性粉剂(WP)、50%烯酰吗啉(安克)WP、25%嘧菌酯(阿米西达)悬浮剂(SC)、64%恶霜·锰锌(杀毒矾)WP、68%精甲霜灵·锰锌(金雷)水分散粒剂(WG)、70%丙森锌(安泰生)WP、68.75%氟吡菌胺·霜霉威(银法利)SC、18.7%烯酰·吡唑酯(凯特)WG、25%双炔酰菌胺(瑞凡)SC和50%多菌灵WP等10种药剂进行了田间马铃薯晚疫病防治试验。结果表明:除50%多菌灵WP之外,其他9种药剂对马铃薯晚疫病均具有明显的防治效果和增产效果,防效均达90%以上,增产10.90%~20.30%,净收入增加500~1000元·(667m2)-1。根据药剂的防效和增产效果,提出广东省马铃薯晚疫病防治的参考药剂,首先是72%霜脲·锰锌WP和50%烯酰吗啉WP,其次是68%精甲霜灵·锰锌WG、18.7%烯酰·吡唑酯WG、25%嘧菌酯SC、70%丙森锌WP和64%恶霜·锰锌WP。 相似文献
166.
菜地土壤中氮肥的反硝化损失和N2O排放 总被引:4,自引:0,他引:4
A field experiment was conducted on Chinese cabbage (Brassica campestris L. ssp. pekinensis (Lour.) Olsson) in a Nanjing suburb in 2003. The experiment included 4 treatments in a randomized complete block design with 3 replicates: zero chemical fertilizer N (CK); urea at rates of 300 kg N ha^-1 (U300) and 600 kg N ha^-1 (U600), both as basal and two topdressings; and polymer-coated urea at a rate of 180 kg N ha^-1 (PCU180) as a basal application. The acetylene inhibition technique was used to measure denitrification (N2 + N2O) from intact soil cores and N2O emissions in the absence of acetylene. Results showed that compared to (3K total denitrification losses were significantly greater (P ≤ 0.05) in the PCU180, U300, and U600 treatments,while N2O emissions in the U300 and U600 treatments were significantly higher (P ≤ 0.05) than (3K. In the U300 and U600 treatments peaks of denitrification and N2O emission were usually observed after N application. In the polymer-coated urea treatment (PCU180) during the period 20 to 40 days after transplanting, higher denitrification rates and N2O fluxes occurred. Compared with urea, polymer-coated urea did not show any effect on reducing denitrification losses and N2O emissions in terms of percentage of applied N. As temperature gradually decreased from transplanting to harvest, denitrification rates and N2O emissions tended to decrease. A significant (P ≤0.01) positive correlation occurred between denitrification (r = 0.872) or N2O emission (r = 0.781) flux densities and soil temperature in the CK treatment with a stable nitrate content during the whole growing season. 相似文献
168.
169.
近几年,我国肉牛业发展遇到了牛源紧缺的问题,其主要原因是牛繁殖率低,牛源供给不足;肉牛繁育部门经济效益差,没有生产犊牛的积极性;牛个体的产肉量低,生产单位牛肉需要屠宰更多的牛;肉牛繁育户组织化程度低,一方面,实力弱小,没有代言人,在产业链中处于弱势地位,另一方面,难以提高生产水平和市场竞争力。解决牛源紧缺问题,要提高牛的繁殖效率.利用奶公牛产肉,增加牛源供给;要提高个体产肉量,少杀牛而多产肉,缓解牛源需求;借鉴国外经验,建立和发展农业合作社,提高技术、加强管理,提高应对市场的能力和提高影响力,从而提高肉牛繁育户的经济效益和权益。 相似文献
170.
根据已经发表的F18ab菌毛A亚单位(FedA/ab)的基因(fedA/ab)[1],设计一对引物,利用PCR技术从表达F18ac菌毛的大肠杆菌2134P株[2]、8199株[3]、8813株[3]中分别扩增到一段序列,并克隆至pGEM-T载体,获得重组质粒T2134PA、T8199A、T8813A.琼脂糖凝胶电泳、序列测定及分析表明,该3个序列大小均为516bp,与fedA/ab(513bp)具有较高的同源性,分别为96.3%、96.5%、95.9%,推导的Fed/ac氨基酸序列与FedA/ab同源性分别为93.0%、93.6%、92.4%.数据表明该实验所克隆的序列均为F18ac菌毛A亚单位(FedA/ac)的基因(fedA/ac). 相似文献