全文获取类型
收费全文 | 8210篇 |
免费 | 409篇 |
国内免费 | 9篇 |
专业分类
林业 | 588篇 |
农学 | 275篇 |
基础科学 | 62篇 |
1389篇 | |
综合类 | 1234篇 |
农作物 | 542篇 |
水产渔业 | 647篇 |
畜牧兽医 | 3023篇 |
园艺 | 215篇 |
植物保护 | 653篇 |
出版年
2023年 | 47篇 |
2022年 | 73篇 |
2021年 | 138篇 |
2020年 | 151篇 |
2019年 | 174篇 |
2018年 | 154篇 |
2017年 | 148篇 |
2016年 | 172篇 |
2015年 | 130篇 |
2014年 | 183篇 |
2013年 | 342篇 |
2012年 | 408篇 |
2011年 | 562篇 |
2010年 | 319篇 |
2009年 | 298篇 |
2008年 | 548篇 |
2007年 | 502篇 |
2006年 | 511篇 |
2005年 | 540篇 |
2004年 | 442篇 |
2003年 | 481篇 |
2002年 | 420篇 |
2001年 | 93篇 |
2000年 | 87篇 |
1999年 | 100篇 |
1998年 | 85篇 |
1997年 | 76篇 |
1996年 | 67篇 |
1995年 | 89篇 |
1994年 | 86篇 |
1993年 | 73篇 |
1992年 | 56篇 |
1991年 | 54篇 |
1990年 | 63篇 |
1989年 | 45篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 48篇 |
1985年 | 50篇 |
1984年 | 49篇 |
1983年 | 46篇 |
1982年 | 32篇 |
1981年 | 25篇 |
1980年 | 34篇 |
1979年 | 29篇 |
1978年 | 37篇 |
1977年 | 37篇 |
1976年 | 35篇 |
1975年 | 38篇 |
1974年 | 30篇 |
排序方式: 共有8628条查询结果,搜索用时 15 毫秒
991.
John V. Westra Kevin J. Boyle Gregory A. Porter 《American Journal of Potato Research》1995,72(2):99-117
Using actual potato production data from Aroostook County, Maine, we investigate the possibility of producers increasing net revenues by modifying rotation practices. By examining rotations as a whole, and incorporating yield effects and changes in production costs across rotations, more realistic pictures of net revenues for each rotation develop than if net revenue for each crop within a rotation is considered independently. Our analyses indicate producers can alter their production practices within the range of rotations used locally to increase net revenues. A key finding confirms the synergistic interaction between grains underseeded with a green manure crop and round-white potato varieties, resulting in decreased production costs, greater potato yields, and increased net revenues. 相似文献
992.
Lal J Kumar CV Suresh MV Indira M Vijayammal PL 《Plant foods for human nutrition (Dordrecht, Netherlands)》2001,56(2):133-143
The objective of this study was to determine theeffects of country liquor Toddy and its equivalentquantity of ethanol on lipid metabolism duringgestation in rats. Female rats weighing an average of125 g were exposed to Toddy (24.5 ml/body weight/day)and ethanol (0.52 ml/kg body weight/day) for 15 daysbefore conception and throughout gestation. On the19th day of gestation, altered liver function andhyperlipidemia was seen in both the treated groups.Altered liver function was evidenced by the increasedactivity of alcohol dehydrogenase, aldehydedehydrogenase, glutamic oxaloacetic transaminase oraspartate amino transferase (GOT), glutamic pyruvictransaminase or alanine amino transferase (GPT) andgamma glutamyl transpeptidase (GGT). Hyperlipidemiawas caused by increased biosynthesis and decreaseddegradation of lipids. The incorporation of 14Cacetate in lipids and activities of HMG CoA reductaseand lipogenic enzymes were elevated and activity ofLPL and bile acids contents were decreased. Toddytreated rats were more severely affected than thosereceiving an equivalent quantity of ethanol. Toddyseemed to potentiate the toxicity induced by alcoholindicating the role of the nonethanolic portion.Hepatic functions were also affected. 相似文献
993.
Anastasia Ktenioudaki Emily Crofton Amalia G.M. Scannell John A. Hannon Kieran N. Kilcawley Eimear Gallagher 《Journal of Cereal Science》2013
The incorporation of brewer's spent grain (BSG) into baked snacks (crispy-slices) was investigated in terms of nutritional, sensory and aromatic properties. Wheat flour was replaced with BSG at the levels of 10, 15 and 25%. Snacks containing 10% BSG exhibited high Crispiness index (Ci), low Crispiness work (Wc) and a high number of peaks during texture analysis, indicating that the crispiness of the samples was not negatively affected. However higher levels of BSG affected the texture and the crumb structure of snacks and the results were significantly different to the 100% wheat control. Addition of BSG altered the odour profile of the snacks as shown by the volatile profiles, however sensory results indicated that BSG-containing snacks at a level of 10% were highly acceptable and highlighted the possibility of using BSG as a baking ingredient in the formulation of enhanced fibre baked snacks. 相似文献
994.
Tetrodotoxin (TTX) is a neurotoxin that has been reported from taxonomically diverse organisms across 14 different phyla. The biogenic origin of tetrodotoxin is still disputed, however, TTX biosynthesis by host-associated bacteria has been reported. An investigation into the culturable microbial populations from the TTX-associated blue-ringed octopus Hapalochlaena sp. and sea slug Pleurobranchaea maculata revealed a surprisingly high microbial diversity. Although TTX was not detected among the cultured isolates, PCR screening identifiedsome natural product biosynthesis genes putatively involved in its assembly. This study is the first to report on the microbial diversity of culturable communities from H. maculosa and P. maculata and common natural product biosynthesis genes from their microbiota. We also reassess the production of TTX reported from three bacterial strains isolated from the TTX-containing gastropod Nassarius semiplicatus. 相似文献
995.
996.
Xi Liang John E. Erickson Wilfred Vermerris Diane L. Rowland Lynn E. Sollenberger Maria L. Silveira 《Journal of Crop Improvement》2017,31(1):39-55
Plant root architecture offers the potential for increasing soil water accessibility, particularly under water-limited conditions. The objectives of this study were to evaluate the root architecture in two genotypes of sorghum (Sorghum bicolor (L.) Moench) differing in root angles and to assess the influence of different deficit irrigation regimes on root architecture. The response of two sorghum genotypes, ‘Early Hegari-Sart’ (EH; steep root angle) and ‘Bk7’ (shallow root angle) to four irrigation treatments was investigated in two replicated outdoor studies using large pots. The results indicated that EH possessed steeper brace and crown root angles, fewer brace roots, greater root biomass, and root length density than Bk7 at deeper soil depths (i.e., 15–30 and 30–45 cm) compared with a shallower depth (i.e., 0–15 cm). Across the soil profile, EH had greater root length density and length of roots of small diameter (<1 mm) than Bk7. Accordingly, EH showed more rapid soil-water capture than Bk7. Different levels of irrigation input greatly affected root architecture. Severe deficit irrigation (25% of full crop transpiration throughout the season) increased the angle and number of crown roots, root biomass, and root length density compared with 75 and 100% of full crop transpiration treatments. Consequently, root system architecture can be effectively manipulated through both genotypic selection and irrigation management to ensure optimal performance under different levels of soil available water. 相似文献
997.
998.
正棉籽酸脱绒会危害育种家人身安全和潜在环境。需要1种无需用酸,能有效去除棉短绒且对棉种萌发无不利影响的脱绒方法。为了优化棉籽机械脱绒流程,美国农业部农业研究中心(USDA-ARS)棉花生产与加工部门(Lubbock,Texas)研发创制了一台棉籽机械脱绒样机(图1,图2)。测试设计了应用7种滚筒衬垫(1种是不用任何研磨材料,其余6种分别采用不同的研磨材料)、1个或2个辊刷"擦 相似文献
999.
Megan L Fritz Juan Huang Edward D Walker M Nabie Bayoh John Vulule James R Miller 《Journal of circadian rhythms》2008,6(1):2
Background
Anopheles gambiae s.s. Giles is a major malaria vector in Sub-Saharan Africa. Studies of the basic biology of this mosquito, including oviposition, provide a background for assessing which attributes might be exploited for suppressing A. gambiae populations. Here, we report on when during the diel cycle A. gambiae individuals deposit eggs as compared to the ovipositional patterns of groups. 相似文献1000.
The relationship between panicle structure and oat grain quality characteristics was examined in a winter oat (Avena sativa) experiment, cv. Gerald, fertilized with 80 and 200 kg/ha N. Spikelets on each whorl were counted and separated into primary, secondary, and tertiary grains, which were counted and weighed, and the kernels extracted manually and weighed. Tiller and whorl rank had relatively small effects on weight per grain and kernel content. Nitrogen application significantly increased weight per primary and secondary grain on the main stem and T1, the first tiller, while spikelet and grain numbers increased only on T1. However, weight per grain and kernel contents in all whorls on both the main stem and T1 were not significantly affected by nitrogen. Although kernel contents were significantly affected by nitrogen application on some occasions, increases and decreases were less than 2.5%. Across the whole plant, numbers of primary and secondary grains increased at the higher nitrogen application, but weight per primary grain and kernel contents were unaffected. However, weight per secondary grain significantly increased at the higher nitrogen application, thus improving uniformity of grain size which is of value to millers. 相似文献