全文获取类型
收费全文 | 11631篇 |
免费 | 411篇 |
国内免费 | 1198篇 |
专业分类
林业 | 369篇 |
农学 | 2230篇 |
基础科学 | 445篇 |
2170篇 | |
综合类 | 5222篇 |
农作物 | 1744篇 |
水产渔业 | 182篇 |
畜牧兽医 | 327篇 |
园艺 | 156篇 |
植物保护 | 395篇 |
出版年
2024年 | 57篇 |
2023年 | 134篇 |
2022年 | 184篇 |
2021年 | 220篇 |
2020年 | 320篇 |
2019年 | 286篇 |
2018年 | 244篇 |
2017年 | 392篇 |
2016年 | 497篇 |
2015年 | 477篇 |
2014年 | 610篇 |
2013年 | 875篇 |
2012年 | 808篇 |
2011年 | 843篇 |
2010年 | 705篇 |
2009年 | 760篇 |
2008年 | 719篇 |
2007年 | 735篇 |
2006年 | 673篇 |
2005年 | 585篇 |
2004年 | 440篇 |
2003年 | 352篇 |
2002年 | 243篇 |
2001年 | 251篇 |
2000年 | 227篇 |
1999年 | 187篇 |
1998年 | 194篇 |
1997年 | 143篇 |
1996年 | 148篇 |
1995年 | 143篇 |
1994年 | 124篇 |
1993年 | 134篇 |
1992年 | 125篇 |
1991年 | 108篇 |
1990年 | 90篇 |
1989年 | 59篇 |
1988年 | 75篇 |
1987年 | 38篇 |
1986年 | 14篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1963年 | 5篇 |
1962年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
The denitrifying woodchip bioreactor is designed to remediate nitrate-rich water, including those produced from aquaculture effluents. Reuse of treated bioreactor outflows in recirculating aquaculture would offer considerable water savings and valuable alkalinity recuperation. However, such bioreactors may leach detrimental wood-bound contaminants, preventing outflow reuse. To determine water reuse potential, woodchip media from two hardwood species (white ash, Fraxinus americana; Norway maple, Acer platanoides) were evaluated for 206 d under a range of operating conditions (start-up, steady-state, reducing conditions, and drying-rewetting cycles) for a spectrum of potentially harmful dissolved contaminants. Aerated outflows also were evaluated for acute and chronic toxicity to the biologically sensitive invertebrate Ceriodaphnia dubia. Dissolved metal leaching subsided within the first few weeks of operation, though initial concentrations of copper and zinc were detected at concentrations of concern. Elevated concentrations of tannins-lignin and total ammonia nitrogen were detected throughout the study and were influenced by operational phase. Acute toxicity was not generally detected, though chronic toxicity was observed during drying-rewetting cycles in the maple outflows. The measured toxicity was not correlated with water chemistry, indicating an additive effect of several toxicants. Overall, significant differences in outflow water quality between ash and maple wood species were negligible. Results indicated that bioreactor outflows may be applicable for aquacultural reuse, though reusing outflows immediately following start-up or restarting after a dry period would not be recommended. 相似文献
2.
3.
This study aimed to explore the feasibility of zein as a gluten alternative in preparing sheeted doughs with rice flours containing different amylose contents (12, 19, and 26%) that were successfully slit into noodle strands. Rice-zein mixtures with lower amylose contents exhibited lower pasting parameters and the high amylose paste samples possessed more elastic properties. Higher water absorption was observed in the low amylose rice-zein mixture whereas the use of zein were effective in increasing the stability of rice dough regardless of amylose content. In case of thermal conductivity, the noodle doughs prepared with high amylose rice-zein mixture had low thermal conductivity, probably implying a long cooking time. The structure of the rice-zein noodles had a tendency to become firmer with increasing levels of amylose by showing greater breaking stress and resistance to extension that could be correlated to reduced cooking loss. 相似文献
4.
为了明确水稻条纹病毒(RSV)在水稻和玉米上发生程度差异明显的原因,从一个侧面了解RSV流行本质,2004年在洪泽进行田间试验。采用黄盘诱集、盘扑、盘刮、肉眼计数等方法比较武育粳3号和掖单13上灰飞虱侵入和消长动态,结果表明两者均只有一个成虫侵入高峰,单位面积迁入虫量前者是后者的3.6倍,单株平均虫量相近。Dot-ELISA法测定灰飞虱带毒率为40%,成虫迁移扩散高峰期22d内两者接毒量约为每天百株137头带毒虫。武育粳3号有二代若虫发生,掖单13则无。逐日调查发病进程,结果显示水稻发病率为60%,玉米为0。室内抗性鉴定,掖单13对RSV的抗性比武育粳3号高4个级别。综合以上结果,寄主品种抗性决定了RSV在水稻和玉米上流行状况,二代若虫重复侵染是RSV在水稻上重发的另一主要原因。 相似文献
5.
6.
7.
超高产水稻产量形成的气候生态特点研究 总被引:11,自引:1,他引:10
在云南和湖南异地异季种植,研究了水稻超高产形成的相应气候生态条件,结果表明:超高产水稻具有大穗、多穗、高结实率的特点.云南试区具有日较差大、日照时数多、相对湿度低,平均温度较低的气候特点,故水稻生育期较长,同化物积累多,成穗率高,灌浆强度大.湖南试区阴雨寡照是影响产量的重要因素. 相似文献
8.
9.
不同的施肥方式对剑麻施肥区域土壤微生物类群的影响 总被引:5,自引:0,他引:5
研究不同的施肥方式对剑麻施肥区域土壤微生物类群产生的影响。结果表明,不同施肥方式下土壤微生物总量各有差异,在总体数量上以细菌为主,真菌次之,再其次是放线茵,特殊生理类群是解磷茵居多,纤维素分解茵次之,固氮茵最少;但从土壤微生物多样性指数来看,则表现为土壤中主要微生物类群多样性指数是施肥点的土壤高于附近的土壤,而土壤中特殊生理微生物多样性指数则无此变化趋势,即微生物总数高的土壤,其多样性指数不一定高。因此评价土壤生物多样性应将二者结合起来。 相似文献
10.