全文获取类型
收费全文 | 1487篇 |
免费 | 124篇 |
国内免费 | 44篇 |
专业分类
林业 | 95篇 |
农学 | 86篇 |
基础科学 | 11篇 |
71篇 | |
综合类 | 380篇 |
农作物 | 88篇 |
水产渔业 | 20篇 |
畜牧兽医 | 64篇 |
园艺 | 15篇 |
植物保护 | 825篇 |
出版年
2024年 | 8篇 |
2023年 | 39篇 |
2022年 | 48篇 |
2021年 | 39篇 |
2020年 | 66篇 |
2019年 | 58篇 |
2018年 | 55篇 |
2017年 | 57篇 |
2016年 | 69篇 |
2015年 | 56篇 |
2014年 | 73篇 |
2013年 | 77篇 |
2012年 | 88篇 |
2011年 | 84篇 |
2010年 | 52篇 |
2009年 | 76篇 |
2008年 | 59篇 |
2007年 | 73篇 |
2006年 | 85篇 |
2005年 | 60篇 |
2004年 | 54篇 |
2003年 | 60篇 |
2002年 | 52篇 |
2001年 | 61篇 |
2000年 | 42篇 |
1999年 | 37篇 |
1998年 | 30篇 |
1997年 | 29篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 4篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1655条查询结果,搜索用时 15 毫秒
41.
蔗园恶性杂草香附子药剂防除效果评价 总被引:1,自引:0,他引:1
为筛选蔗园恶性杂草香附子的理想安全性除草剂,选用20%噻吩磺隆WP和65%甲·灭·敌草隆WP进行田间药效试验。田间试验结果表明:20%噻吩磺隆WP和65%甲·灭·敌草隆WP对蔗园恶性杂草香附子均具有良好的防除效果,是防除蔗园恶性杂草香附子的理想除草剂。20%噻吩磺隆WP最适宜用量为1125 g/hm2(有效成分225 g)、65%甲·灭·敌草隆WP为3150 g/hm2(有效成分2047.5 g)。2种药剂均可在香附子生长旺盛期(株高10~15 cm),按每公顷用药量兑水675 kg进行定向茎叶喷雾,药后15天防除效果可达87.9%以上。 相似文献
42.
Summary Semilooper resistant transgenic castor plants were produced through Agrobacterium-mediated genetic transformation method. Two castor cultivars, Jyothi and VP1 were transformed using the super-binary vector
pTOK233 carrying gus A and hpt genes. Putative transformants were regenerated following selection on the hygromycin containing medium. GUS positive primary
transformants, when subjected to Southern analysis, revealed stable integration of gus A into their genomes. In the T1 generation, a monogenic segregation ratio of 3 GUS positive: 1 GUS negative plants was observed. Furthermore, transformation
experiments were carried out with the Agrobacterium pSB111 super-binary vector carrying a synthetic delta endotoxin gene cryIAb and the herbicide resistance gene bar both driven by cauliflower mosaic virus 35S promoter. Putative transformants were regenerated through selection on the phosphinothricin
containing medium and Basta tolerant transformants were subjected to molecular analysis. PCR analysis revealed the presence
of both bar and cryIAb genes in the Basta tolerant primary transformants. Southern analysis of PCR positive plants with cryIAb probe showed a 3 Kb band upon HindIII digestion and a > 6 Kb band with BamHI digestion, thus suggesting stable integration of cryIAb intact expression cassette and independent nature of the transformants. The primary transformants subjected to ELISA disclosed
varied levels of Cry protein. These transgenics expressing cryIAb – when bioassayed against freshly hatched semilooper larvae – induced substantial (> 88%) insect mortality. Southern analysis
of 2T1 plants revealed the presence of cryIAb gene, indicating stable inheritance of the transgene into the next generation. In T1, all the Southern-positive plants for cryIAb invariably exhibited tolerance to Basta, denoting co-segregation of both bar and cryIAb genes. Transgenics, expressing cryIAb exhibited ample resistance against the castor semilooper. 相似文献
43.
44.
45.
Oilseed rape has been modified extensively by conventional breeding for the production of varieties useful for human consumption (blended vegetable oil and margarine) and industrial processes (rubber additives and high‐temperature lubricants). Because much is now known about its genetic and biochemical composition, it has been an obvious choice for genetic modification and is now at the forefront of the commercial development of genetically modified (GM) or transgenic crops. Around the world, the increase in commercial plantings of all transgenic crops has been rapid. In 1996, 1.7 million hectares were planted, but by 1998 this figure had jumped to 27.8 million ha. The area in the year 2001 is likely to be about 50 million ha. With the possible introduction of transgenic varieties into European agriculture, it is essential that the associated farming practices employed are appropriate for their growth, both from a commercial and an environmental viewpoint. Some of the first transgenic crops are those carrying agronomic traits, e.g. herbicide tolerance transgenes. However, before full commercialization occurs, important agronomic and environmental questions need to be answered. How are these new crops to be incorporated into existing cropping practices? How will this change the current herbicide use profile for a given crop? Do herbicide‐tolerant varieties enhance or impede integrated pest management schemes? What is the likely uptake of such crops in agriculture? What are the ecological implications of their introduction? Are there effective measures to control the spread of transgenes to wild relatives? This paper addresses these questions, with special emphasis on oilseed rape production in the UK, but includes examples from other crops and countries where appropriate. 相似文献
46.
47.
Despite the considerable research efforts invested over the years to measure the fitness costs of herbicide resistance, these have rarely been used to inform a predictive theory about the fate of resistance once the herbicide is discontinued. One reason for this may be the reductive focus on relative fitness of two genotypes as a single measure of differential performance. Although the extent of variation in relative fitness between resistant and susceptible plants has not been assessed consistently, we know enough about plant physiology and ecology not to reduce it to a single fixed value. Research must therefore consider carefully the relevance of the experimental environment, the life stage and the choice of metric when measuring fitness‐related traits. The reason most often given for measuring the cost of resistance, prediction of the impacts of management options on population dynamics, cannot be addressed using arbitrary components of fitness or a fixed value of relative fitness. To inform management options, the measurement of traits that capture the relevant processes and the main causes of their variation are required. With an emphasis on the benefit of field experiments measured over multiple time points and seasons, we highlight examples of studies that have made significant advances in this direction. © 2017 Society of Chemical Industry 相似文献
48.
为了开发木醋液作为优质生物农药的应用价值,本文归纳了不同原材料制作的木醋液在细菌真菌病害、病毒病、根结线虫病、害虫和杂草防除中的应用研究案例。总结了木醋液分别在病虫草防治中的作用:在适当浓度下,对真菌、细菌和根结线虫皆能有效抑制;作为助剂也能用于防治植物病毒病;对害虫具有驱避作用,浓度高时,直接的毒杀效果也很明显;对于作物田的部分杂草种类,木醋液具有被开发为生物除草剂的潜能。同时简单介绍了木醋液对有害生物的作用机理,指出了木醋液作为生物农药具有原材料来源广泛、广谱有效、环境友好、不易导致抗性发展等特点,其作为生物农药具有极大的应用价值。最后指出,在今后应用研发中应分馏纯化、组合复配木醋液产品,实现机制研究和产品标准化的综合目标。 相似文献
49.
经除草剂处理的水稻对褐飞虱体内几种酶及水稻受褐飞虱为害程度的影响 总被引:5,自引:1,他引:5
褐飞虱5龄若虫在不同除草剂不同剂量处理的水稻上短期取食(取食1 h)和长期取食(3龄若虫取食至5龄,约7 d),然后测定其体内代谢酶、保护酶的变化。褐飞虱取食除草剂处理的水稻后其体内羧酸酯酶活性不论是短期取食还是长期取食均极显著高于对照(未施用除草剂);乙酰胆碱酯酶活性明显高于对照;稻乐思、苯达松低剂量、丁草胺高剂量处理短期取食后超氧化物歧化酶活性显著低于对照,所有处理长期取食明显高于对照;过氧化物酶活性除了稻乐思300 mL/hm2和苯达松1500 mL/hm2处理短期取食低于对照外(但没有达显著差异),也不同程度地高于对照。褐飞虱在除草剂处理的水稻上蜜露排泄量显著增加,水稻受害程度与对照相比极显著加重。除草剂处理后的水稻游离氨基酸的含量增加而蔗糖含量下降,由此表明除草剂施用后对水稻和褐飞虱具有双向效应 相似文献
50.