全文获取类型
收费全文 | 2061篇 |
免费 | 259篇 |
国内免费 | 270篇 |
专业分类
林业 | 27篇 |
农学 | 54篇 |
基础科学 | 4篇 |
54篇 | |
综合类 | 799篇 |
农作物 | 15篇 |
水产渔业 | 1372篇 |
畜牧兽医 | 232篇 |
园艺 | 11篇 |
植物保护 | 22篇 |
出版年
2024年 | 7篇 |
2023年 | 27篇 |
2022年 | 39篇 |
2021年 | 46篇 |
2020年 | 80篇 |
2019年 | 82篇 |
2018年 | 65篇 |
2017年 | 127篇 |
2016年 | 98篇 |
2015年 | 71篇 |
2014年 | 73篇 |
2013年 | 141篇 |
2012年 | 174篇 |
2011年 | 178篇 |
2010年 | 135篇 |
2009年 | 115篇 |
2008年 | 106篇 |
2007年 | 107篇 |
2006年 | 124篇 |
2005年 | 88篇 |
2004年 | 58篇 |
2003年 | 77篇 |
2002年 | 53篇 |
2001年 | 68篇 |
2000年 | 56篇 |
1999年 | 44篇 |
1998年 | 38篇 |
1997年 | 37篇 |
1996年 | 38篇 |
1995年 | 44篇 |
1994年 | 39篇 |
1993年 | 44篇 |
1992年 | 31篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有2590条查询结果,搜索用时 62 毫秒
991.
992.
993.
载菌蒙托石改善鲫养殖水质和生长性能的研究 总被引:1,自引:0,他引:1
以附载益生菌-沼泽红假单胞菌的蒙托石为研究对象,通过对鲫养殖水质指标和生长性能的测定,研究了其作用效果.试验分为1个对照组和3个试验组(T1、T2、T3分别添加一定量的沼泽红假单胞菌、蒙托石和载菌蒙托石).试验结果表明,与对照组相比,试验组T3显著降低了(P < 0.01)养殖水体后期氨氮、亚硝酸盐氮、硝酸盐氮、化学需氧量和硫化物的含量,提高了鲫的质量日增长和质量相对增长率(P < 0.01),改善效果优于T1和T2.试验组T1和T2在生长指标上与对照组比较,虽有不同程度的提高,但差异不显著(P > 0.01). 相似文献
994.
995.
在零售市场和生产企业抽取4批真空包装淡腌青鱼,对其感官、化学和细菌学品质特性进行分析,并对细菌类型和数量进行研究。结果显示,产品栅栏因子及强度存在差异,盐分含量6.68%~12.06%,平均值(9.36±2.2)%;水分活度值0.75~0.91,平均值0.82±0.07;pH值6.00~6.30,平均值6.20±0.13。栅栏因子种类和强度的不同决定产品品质的差异,感官评价均可接受,过氧化值均值为19.65±8.75 meq/kg,挥发性盐基氮均值为24.50±15.30 mg/100 g,菌落总数均值为4.45±1.15 cfu/g,大肠菌群均低于30 MPN/100 g。从4批淡腌青鱼样品分离到234株细菌,73.9%是革兰氏阳性细菌,其中36.3%是葡萄球菌,31.6%是链球菌,并出现少量微球菌和棒状杆菌;由需氧革兰氏阴性杆菌不动杆菌、摩氏杆菌和鞘氨醇单胞菌组成较小的细菌菌群约占总细菌群落的18.4%,显示水分活度、盐分含量和pH值等栅栏因子与产品细菌类型和数量呈一定相关性。 相似文献
996.
Mohammad Mustafizur Rahman Marc Verdegem Leo Nagelkerke Md Abdul Wahab Ana Milstein & Johan Verreth 《Aquaculture Research》2008,39(1):85-95
The effects of introducing common carp (CC) and of adding artificial feed to fertilized rohu ponds on water quality and nutrient accumulation efficiency were studied. All ponds were stocked with 15 000 rohu ha?1. Treatments included ponds with rohu alone, rohu plus 5000 common carp ha?1 and rohu plus 10 000 CC ha?1. A comparison was also made between supplementally fed and non‐fed ponds. The overall highest nitrogen (N) and phosphorus (P) concentrations were observed in ponds with 5000 CC ha?1, followed by ponds with 10 000 and 0 CC ha?1. The largest fractions of N and P inputs accumulating in fish, phytoplankton and zooplankton were observed in ponds with 5000 CC ha?1, followed by ponds with 10 000 CC ha?1 and subsequently ponds without CC. Relatively more nutrients accumulated in benthic organisms in ponds without than in ponds with CC. A smaller fraction of the nutrient input was retained in fish, plankton and benthic organisms in ponds without CC compared with ponds with CC. Compared with 5000 CC ha?1, stocking 10 000 CC ha?1 can be considered as overstocking, because this leads to lower fish production and relatively less nutrients retained in plankton and benthic organisms. 相似文献
997.
Stuart J Rowland Charlie Mifsud Mark Nixon Philip Read Matthew Landos 《Aquaculture Research》2008,40(1):44-54
Infestations of the protozoan parasite, Ichthyophthirius multifiliis, cause the serious disease ichthyophthiriosis in freshwater fish throughout the world. Formalin is a recommended treatment for ichthyophthiriosis in the Australian fish silver perch (Bidyanus bidyanus Mitchell), but the disease is difficult to control in ponds, particularly at low water temperatures. Experiments were carried out to develop an improved treatment regime for formalin and to evaluate copper as a therapeutant. Silver perch fingerlings infested with I. multifiliis were stocked into 55 L aquaria at temperatures of 14.8–17.6 °C and alkalinities of 70–110 mg L?1. Formalin (34–38% formaldehyde) or copper (24.5% copper sulphate) were added to the aquaria and then monitored and readjusted to nominal concentrations daily. A concentration of 30 mg L?1 formalin controlled ichthyophthiriosis, but fish treated with 20 mg L?1 remained infested with theronts and trophonts on day 17; survival at both concentrations was 100%. A concentration of 10 mg L?1 formalin did not control ichthyophthiriosis and all fish were dead from the infestation by day 17. Fish treated with 0.1 or 0.2 mg L?1 copper were free of theronts and trophonts by days 17 and 14, respectively, and survival was 100%. Survival at 0.05 mg L?1 copper was 100%, but fish remained infested. At 0.25 mg L?1 copper, survival was 82.5% and there were no theronts or trophonts on gill and skin tissues of fingerlings by day 14. There was total mortality of fish treated with 0.5 or 1.0 mg L?1 copper suggesting these concentrations are toxic to silver perch. All fish in infested‐control treatments died. In earthen ponds containing silver perch, 0.2 mg L?1 copper was depleted to below 0.1 mg L?1 within 24 h, and concentrations of 25–38 mg L?1 formalin were depleted to below 15 mg L?1 within 48 h. Treatment regimes involving daily applications of formalin or copper controlled ichthyophthiriosis in silver perch in earthen ponds at costs of $US466.37 and $US65.58 hectare?1 day?1 respectively. This study has developed a new formalin‐treatment regime for the control of ichthyophthiriosis, and demonstrated that copper sulphate is a potential therapeutant for this serious disease of silver perch. 相似文献
998.
IPTG诱导含有鲮(Cirrhinus molitorella)生长激素基因(growth hormone,GH)的工程菌M15(pQE30-GH)重组表达鲮生长激素蛋白。SDS-PAGE凝胶电泳结果表明,在24.5kDa处有1条重组表达鲮生长激素条带,经分离纯化、复性和浓缩后得到有活性的重组鲮生长激素蛋白。以复性浓缩后的重组鲮生长激素蛋白为抗原,采用改进的方法对新西兰大白兔进行皮下多点免疫注射,获得兔抗鲮生长激素多克隆抗体。经ELISA检测该免疫血清的滴度为12800。以该多抗为一抗,Western blotting可以检测到10ng的抗原量;并且在鲮垂体组织提取液中和血清中检测到一种能与该血清作用的大小约为21.5kDa的蛋白条带。说明该试验所制备的兔抗鲮生长激素多克隆抗体具有较好的免疫活性。 相似文献
999.
异育银鲫经过低温下停食后的补偿生长 总被引:2,自引:0,他引:2
在室内水槽中进行了10周实验,以检验异育银鲫(Carassius auratus gibeli)经过低温下停食后的补偿生长。实验鱼初始体质量为(5.1±0.1)g,分为4组:2组鱼在第1~4周内被停食,在第5~10周分别恢复投喂蛋白能量比为23 g.MJ-1(SL组)和26 g.MJ-1(SH组)的等能饲料;另2组鱼(CL组和CH组)在1~4周内投喂蛋白能量比为23 g.MJ-1的饲料,在第5~10周分别投喂蛋白能量比为23 g.MJ-1(CL组)和26 g.MJ-1(CH组)的饲料。第1~4周内水温控制在14.8~15.2℃,第5~10周内水温控制在24.8~25.2℃。结果表明,第4周结束时SL组和SH组体质量明显低于CL组和CH组;SL组和SH组全鱼水分、蛋白质和灰分百分含量明显高于CL组和CH组,但脂肪含量明显低于后者。恢复投喂期间,SL组在第7~10周内SGR高于CL组,SH组第5~8周内SGR高于CH组,但SL组与SH组,CL组与CH组之间SGR无显著差异(P>0.05)。实验结束时,SL组和SH组的体质量分别低于CL组和CH组,SL组与SH组间及CL组与CH组间体质量无显著差异(P>0.05);SL组和SH组全鱼、躯干和内脏团内蛋白质和灰分含量分别高于CL组和CH组,脂肪含量分别低于CL组和CH组。本实验结果显示,经过低温下停食后,异育银鲫仅表现出部分补偿生长能力,恢复投喂期间增加饲料蛋白质含量未明显增强异育银鲫的补偿生长。[中国水产科学,2007,14(1):113-119] 相似文献
1000.
MASAYUKI YOSHIDA YASUHIKO MUROCHI YOSHIHIKO BABA KAZUMASA UEMATSU 《Fisheries Science》2002,68(2):277-281
ABSTRACT: A new method for monitoring spinal motoneuron activities during fictive swimming in teleost fish was developed. Enamel-insulated copper wire electrodes were implanted in the trunk muscle of goldfish or carp. For each freely moving fish, an electromyogram (EMG) was recorded using the electrodes. In those fish paralyzed with curare, using the same electrode set, bursts of electrical activities consisted of spikes of smaller amplitude and of shorter duration compared with those recorded by EMG. Simultaneous recording of the extracellular activity and intracellular recording from the muscle revealed that the bursts of spikes recorded in the paralyzed fish were motor nerve impulses innervating the muscle and are considered to be fictive swimming activity. The method developed in the present study provides a useful tool with which to investigate neuronal mechanisms underlying swimming activity in teleost fish. 相似文献