全文获取类型
收费全文 | 182106篇 |
免费 | 9307篇 |
国内免费 | 4290篇 |
专业分类
林业 | 11738篇 |
农学 | 10620篇 |
基础科学 | 4462篇 |
23692篇 | |
综合类 | 38331篇 |
农作物 | 8015篇 |
水产渔业 | 8080篇 |
畜牧兽医 | 75389篇 |
园艺 | 3536篇 |
植物保护 | 11840篇 |
出版年
2022年 | 1623篇 |
2021年 | 2403篇 |
2020年 | 2453篇 |
2019年 | 2497篇 |
2018年 | 3728篇 |
2017年 | 4372篇 |
2016年 | 3521篇 |
2015年 | 3423篇 |
2014年 | 3610篇 |
2013年 | 6974篇 |
2012年 | 6247篇 |
2011年 | 7677篇 |
2010年 | 6230篇 |
2009年 | 5779篇 |
2008年 | 6746篇 |
2007年 | 6821篇 |
2006年 | 5509篇 |
2005年 | 5245篇 |
2004年 | 4116篇 |
2003年 | 4191篇 |
2002年 | 3772篇 |
2001年 | 4571篇 |
2000年 | 4646篇 |
1999年 | 4058篇 |
1998年 | 2076篇 |
1997年 | 1992篇 |
1996年 | 1783篇 |
1995年 | 2145篇 |
1994年 | 1756篇 |
1993年 | 1751篇 |
1992年 | 3185篇 |
1991年 | 3213篇 |
1990年 | 3255篇 |
1989年 | 3155篇 |
1988年 | 2887篇 |
1987年 | 2781篇 |
1986年 | 2830篇 |
1985年 | 2702篇 |
1984年 | 2319篇 |
1983年 | 2039篇 |
1979年 | 2196篇 |
1978年 | 1708篇 |
1975年 | 1609篇 |
1974年 | 2028篇 |
1973年 | 2068篇 |
1972年 | 2069篇 |
1971年 | 1924篇 |
1970年 | 1859篇 |
1969年 | 1752篇 |
1967年 | 1612篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Sonia Czarnes Pierre-Edouard Mercier Damien G. Lemoine Jihane Hamzaoui Laurent Legendre 《Journal of Agronomy and Crop Science》2020,206(5):505-516
Members of the bacterial genus Azospirillum are root-associated bacteria that increase yield in cereals by promoting growth and alleviating drought stress. How plants integrate the many bacterium-derived growth-promoting stimuli with other environmental factors to generate a coordinated response remains unresolved. Using a commercial Azospirillum strain, A. lipoferum CRT1 and two host maize cultivars, it was observed that bacterization reduced the drought-induced increase in lateral root growth and enhanced the flood-induced increase in lateral root growth in the more drought- and flood-sensitive cultivar. In the other one, A. lipoferum CRT1 only elicited a moderate root growth response under low soil water potential. The photosynthetic potential and activity were increased in the earlier cultivar and decreased in the later one, irrespective of the soil water content. No impact of the bacterium was seen on the growth of the leaves of both cultivars under both stresses until the third leaf stage, therefore suggesting that it is a consequence of multiple primary adaptations to biotic and abiotic stresses. It is suggested that host–bacteria recognition leads to a stress-specific modulation of the root response and a differential stress-independent effect on photosynthesis. This is the first report of the impact of Azospirillum under flood conditions. 相似文献
22.
23.
24.
Effects of Feeding Frequency on Apparent Energy and Nutrient Digestibility/Availability of Channel Catfish,Ictalurus punctatus,Reared at Optimal and Suboptimal Temperatures
下载免费PDF全文
![点击此处可从《Journal of the World Aquaculture Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This study examined the effects of feeding frequency (daily versus every other day [EOD]) on nutrient digestibility/availability of channel catfish, Ictalurus punctatus, reared at optimal (30 C) and suboptimal (24 C) temperatures. A 28% protein practical diet was used as the test diet, and chromic oxide was used at 0.75% of the diet as a maker. Twenty channel catfish of a mean weight of 141 g/fish were stocked into 12 flow‐through aquaria (110 L). Fish were fed daily or EOD to apparent satiation for 7 d before fecal samples were collected by the dissection method. Fish fed EOD to apparent satiation consumed more diet on days fed than those fed daily, and fish reared at 30 C consumed more diet than those reared at 24 C. Neither feeding frequency nor water temperature significantly affected apparent digestibility coefficients for energy and protein and apparent availability coefficients for total amino acids. Results show no advantage by feeding EOD over feeding daily on nutrient digestibility and diet utilization efficiency. 相似文献
25.
26.
27.
28.
Evaluating the Effects of Dietary Prebiotic Mixture of Mannan Oligosaccharide and Poly‐β‐Hydroxybutyrate on the Growth Performance,Immunity, and Survival of Rainbow Trout,Oncorhynchus mykiss (Walbaum 1792), Fingerlings
下载免费PDF全文
![点击此处可从《Journal of the World Aquaculture Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ebrahim H. Najdegerami Amir Tokmachi Farideh Bakhshi 《Journal of the World Aquaculture Society》2017,48(3):415-425
This study investigated the effects of dietary poly‐β‐hydroxybutyrate (PHB) and mannan oligosaccharide (MOS) on the growth performance, digestive enzyme activities, and disease resistance of rainbow trout fingerlings. A total of 420 fingerlings, distributed equally into four different groups, each with three replicates, were fed a basal diet (control), 2% PHB (PHB), 0.2% MOS (MOS), or a diet supplemented with a mixture of 2% PHB and 0.2% MOS (PHB+MOS) for 60 d. Results showed that dietary PHB and/or MOS did not cause significant improvement in the growth performance of the fingerlings. The gut pH was markedly reduced; however, the activities of the digestive enzymes (except for pepsin and amylase by dietary PHB) were not significantly improved by the dietary supplements. Results also showed that dietary PHB and/or MOS markedly increased the resistance of the fingerlings toward Yersinia ruckeri infection, while the lowest total antibody was observed in fish fed control and MOS, indicating that MOS exerts its protective effects by modulating other mechanisms. Overall, this study provided a first screening effort to determine the effects of PHB and/or MOS as dietary supplements in rainbow trout fingerlings to develop an optimal prebiotic mix for improving the growth and health status of rainbow trout. 相似文献
29.
Fang Chen Hao Zhang Na Zhao Xuehai Yang Encun Du Shaowen Huang Wanzheng Guo Wei Zhang Jintao Wei 《Animal Science Journal》2021,92(1):e13619
Heat stress in poultry is deleterious to productive performance. Chlorogenic acid (CGA) exerts antibacterial, anti-inflammatory, and antioxidant properties. This study was conducted to evaluate the effects of dietary supplemental CGA on the intestinal health and cecal microbiota composition of young hens challenged with acute heat stress. 100-day-old Hy-line brown pullets were randomly divided into four groups. The control group (C) and heat stress group (HS) received a basal diet. HS + CGA300 group and HS + CGA600 group received a basal diet supplemented with 300- and 600-mg/kg CGA, respectively, for 2 weeks before heat stress exposure. Pullets of HS, HS + CGA300, and HS + CGA600 group were exposed to 38°C for 4 h while the control group was maintained at 25°C. In this study, dietary CGA supplementation had effect on mitigate the decreased T-AOC and T-SOD activities and the increasing of IL-1β and TNFα induced by acute heat stress. Dietary supplementation with 600 mg/kg CGA had better effect on increasing the relative abundance of beneficial bacterial genera, such as Rikenellaceae RC9_gut_group, Ruminococcaceae UCG-005, and Christensenellaceae R-7_group, and deceasing bacteria genera involved in inflammation, such as Sutterella species. Therefore, CGA can ameliorate acute heat stress damage through suppressing inflammation and improved antioxidant capacity and cecal microbiota composition. 相似文献
30.
浅谈楼房养猪除臭技术设计与应用 总被引:3,自引:2,他引:1
楼房养猪相较于传统平房养猪,占用面积更小,可节省用地60%以上。楼房养猪同时方便集中管理,易于采光通风和保暖;但是楼房养猪也有明显的缺点,相较于传统的平房养猪,楼房养猪作为集约化、规模化、现代化养猪的集中表现模式,建造及运营维护成本相对较高,消毒及防疫工作较为困难。高楼环境易于通风的同时,猪舍的污染问题也更加突出。猪舍给空气带来的污染不仅会影响猪舍内外的空气质量,同时还会影响猪只的繁殖、生长和发育,并将会对养殖人员与附近居民的身体健康产生重要影响。所以,必须采取相应完善的系统科学措施,处理楼房养猪中的空气除臭问题,保证生猪生活环境的清洁。文章通过结合平房养猪以及楼房养猪的特点,浅谈一下楼房养猪的除臭技术的设计与应用。 相似文献