全文获取类型
收费全文 | 17622篇 |
免费 | 823篇 |
国内免费 | 1033篇 |
专业分类
林业 | 943篇 |
农学 | 1039篇 |
基础科学 | 1118篇 |
1902篇 | |
综合类 | 9363篇 |
农作物 | 1085篇 |
水产渔业 | 528篇 |
畜牧兽医 | 2666篇 |
园艺 | 451篇 |
植物保护 | 383篇 |
出版年
2024年 | 97篇 |
2023年 | 220篇 |
2022年 | 423篇 |
2021年 | 513篇 |
2020年 | 551篇 |
2019年 | 612篇 |
2018年 | 323篇 |
2017年 | 519篇 |
2016年 | 764篇 |
2015年 | 684篇 |
2014年 | 1116篇 |
2013年 | 1192篇 |
2012年 | 1453篇 |
2011年 | 1536篇 |
2010年 | 1197篇 |
2009年 | 1213篇 |
2008年 | 1061篇 |
2007年 | 1111篇 |
2006年 | 873篇 |
2005年 | 705篇 |
2004年 | 459篇 |
2003年 | 455篇 |
2002年 | 283篇 |
2001年 | 250篇 |
2000年 | 260篇 |
1999年 | 209篇 |
1998年 | 190篇 |
1997年 | 200篇 |
1996年 | 150篇 |
1995年 | 156篇 |
1994年 | 107篇 |
1993年 | 152篇 |
1992年 | 87篇 |
1991年 | 89篇 |
1990年 | 68篇 |
1989年 | 46篇 |
1988年 | 46篇 |
1987年 | 42篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1962年 | 1篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
The effect of dietary supplementation with Aurantiochytrium limacinum on lactating dairy cows in terms of animal health,productivity and milk composition 下载免费PDF全文
C. A. Moran M. Morlacchini J. D. Keegan G. Fusconi 《Journal of animal physiology and animal nutrition》2018,102(2):576-590
The aim of this study was to investigate the effect of dietary supplementation with the docosahexaenoic acid (DHA )‐rich microalgae, Aurantiochytrium limacinum (AURA ), on a variety of health and productivity parameters in lactating cows. Twenty‐four cows were blocked by parity and number of days in milk and then randomly assigned to a control (CON ; n = 12) group with no algal supplementation, or a treatment group (AURA ; n = 12) provided with 100 g AURA cow?1 day?1 or 16 g DHA cow?1 day?1. A variety of health and productivity measurements were taken, and results indicated that supplementation had no negative effects on animal health in terms of somatic cell count, haematological and biochemical blood parameters, while body condition was marginally improved by algal supplementation. No differences were found for the various production parameters measured; however, a tendency towards increased milk production was observed for the AURA group during the final stage of the study (+4.5 kg cow?1 day?1, day 78–84). The fatty acid profile of milk was improved by supplementation, with significantly lower saturated fatty acids, significantly higher omega‐3 fatty acids and an improved omega‐3/omega‐6 ratio observed when compared to the control group. The amount of DHA in the milk of cows provided 105 g AURA head?1 day?1 was 4.7 mg/100 g milk with a peak transfer efficiency from feed to milk at day 49 of 8.3%. These results indicate that supplementation with 105 g AURA head?1 day?1 resulted in the successful enrichment of milk with DHA without negatively impacting the health or productivity of the animals. 相似文献
73.
Gas and short‐chain fatty acid production from feeds commonly fed to red deer (Cervus elaphus L.) and incubated with rumen inoculum from red deer and sheep 下载免费PDF全文
Andrej Lavrenčič Darko Veternik 《Journal of animal physiology and animal nutrition》2018,102(5):1146-1153
Efficient red deer supplementary feeding depends on estimations of the nutritive value of offered feeds, frequently estimated with the use of equations derived from domestic ruminants. The aim of this study was to compare the 24‐hour in vitro true dry matter degradability (ivTD24), in vitro gas production (GP) kinetic parameters, GP in 24 hr of incubation (GAS24) and short‐chain fatty acid (SCFA) and microbial biomass (MBS) produced after 24‐hour incubation of feeds in inoculum prepared from sheep and red deer rumen fluid. Eleven feeds, frequently consumed by red deer in Slovenia, which occur either naturally (two fresh grasses, chestnut fruits and common and sessile oak acorns) or are fed as winter supplemental feeds (two grass hays, two grass silages, apple pomace, fresh sugar beetroot), were investigated. The in vitro GP kinetic parameters, GAS24 and ivTD24, did not differ between animal species. Amounts of SCFAs were greater (p < 0.05) when feeds were incubated in sheep inoculum, while molar proportions of acetic and propionic acids did not differ. Molar proportions of butyric acid produced during incubation of high fibre feeds did not differ between animal species, but were higher (p < 0.05) when feeds high in starch or sugar were incubated in red deer inoculum. Greater production of SCFA by sheep rumen microbes suggests better coverage of host animal with energy precursors, while greater production of MBS by red deer rumen microbes suggests better coverage of host animal with protein. Results also suggest that rumens of sheep and red deer are inhabited by different microbial communities, which did not affect the extent of in vitro GP and degradation of feeds used in the present experiment. However, the possibility exists that the divergent nutrient use could be a consequence of different priming by different feeds of the donor animal diets. 相似文献
74.
通过对河南春水镇农业保险的调查背景描述以及对河南春水镇农户进行走访和问卷调查的基础上,分析农户对农业保险的认知度及参与意愿,研究河南春水镇农户对农业保险的认知度以及其参加农业保险的意愿,并得出调查研究结论,最终提出应加大农业保险的宣传、转变农户思想观念以及增加农户农业收入的对策与建议. 相似文献
75.
本文就西吉县农用地膜的应用现状和污染现状进行了分析,并就这一现状提出了促进旱作农业可持续发展的对策措施。 相似文献
76.
This study was conducted from 1992-2002 on 65,534 individual milk records and fat percentage in 473 herds, in six provinces of Khuzestan, Mazndaran, W. Azerbaijan, E. Azerbaijan, Ardabil and Gilan. The data was analyzed by SAS sotfware using GLM procedure. The heritability and breeding value of 1,195 animals were calculated by DFRML procedure. The average milk yield per lactation, days of lactation, fat percentage and LSM of fat percentage were 1,513 kg, 202 days, 5.04 and 6.77, respectively. The estimated heritability of milk was 0.16. The LSM of average milk production in the provinces of Gilan, Mazandaran, E. Azerbaijan, W. Azerbaijan, Khuzestan and Ardabil were: 1,452, 1,586, 1,382, 1,183, 2,135 and 1,189 kg, respectively. These results indicated that Khuzestan province has the highest potential in the field of milk production. The top five highest breeding value bulls have been introduced to artificial insemination's station in the city of Uremia. 相似文献
77.
78.
79.
S.‐E. Jacobsen 《Journal of Agronomy and Crop Science》2011,197(5):390-399
In Bolivia, one of the world’s most important centres of plant domestication, there is growing awareness of the value of native Andean crops, both for domestic consumption and for market sale – notably the virtually boom‐like consumer demand for quinoa around the world. The southern altiplano of Bolivia, south of Oruro, relies almost purely on the production of quinoa and breeding of llamas, which have also been selected as the two commodities of priority to the government to increase the income of the country. Presently, however, quinoa is facing increasing problems in production, owing to its increasing export market and price. The flat areas around the salt desert of the southern altiplano, previously characterized by natural vegetation fed by the llamas, are being increasingly sown with quinoa, hence transformed into deserts, because intensive cultivation methods make the soil loose its fertility. Possible solutions to these problems will require extensive efforts in the south, in addition to various strategies, which also include other parts of the Bolivian altiplano and a strengthened focus on other Andean crops. 相似文献
80.
【目的】筛选适宜内蒙阿鲁科尔沁旗地区种植的燕麦品种。【方法】对12份燕麦(Avena sativa)品种的生育期、草产量、茎叶比、营养特性等进行测定和分析,并运用灰色关联度分析法对各品种的生产性能进行综合评价。【结果】12份供试燕麦品种均能在阿鲁科尔沁旗地区完成整个生育期,表现出较好的适应性,生育期为83~94 d,其中枪手的生育期最短(83 d),爱沃的生育期最长(94 d)。贝勒二代和牧王的株高均达到100 cm以上。枪手、贝勒二代和牧王的干草产量较高,分别为9.99,8.69和8.59 t/hm~2。贝勒二代的茎叶比最低(1.12),适口性最好;美达的茎叶比最高(3.19)。爱沃和贝勒二代的粗蛋白含量(质量分数)较高,分别为12.20%和11.90%;太阳神、贝勒二代和领袖的中性洗涤纤维及酸性洗涤纤维含量较低,领袖和贝勒二代的相对饲喂价值较高。灰色关联度分析表明,综合评价排在前2位的燕麦品种为贝勒二代和牧王,其加权关联度分别为0.838 2和0.799 1。【结论】燕麦品种贝勒二代和牧王综合表现最好,适宜在阿鲁科尔沁旗地区推广种植。 相似文献