全文获取类型
收费全文 | 318594篇 |
免费 | 17835篇 |
国内免费 | 4878篇 |
专业分类
林业 | 29137篇 |
农学 | 20206篇 |
基础科学 | 6211篇 |
51814篇 | |
综合类 | 38941篇 |
农作物 | 19891篇 |
水产渔业 | 19142篇 |
畜牧兽医 | 120739篇 |
园艺 | 7719篇 |
植物保护 | 27507篇 |
出版年
2021年 | 4059篇 |
2020年 | 4269篇 |
2019年 | 5084篇 |
2018年 | 5231篇 |
2017年 | 5927篇 |
2016年 | 6156篇 |
2015年 | 6089篇 |
2014年 | 7359篇 |
2013年 | 18354篇 |
2012年 | 9764篇 |
2011年 | 12015篇 |
2010年 | 10215篇 |
2009年 | 10685篇 |
2008年 | 11099篇 |
2007年 | 10382篇 |
2006年 | 10497篇 |
2005年 | 9728篇 |
2004年 | 8421篇 |
2003年 | 8144篇 |
2002年 | 7226篇 |
2001年 | 8221篇 |
2000年 | 8068篇 |
1999年 | 7690篇 |
1998年 | 5270篇 |
1997年 | 5186篇 |
1996年 | 4894篇 |
1995年 | 5348篇 |
1994年 | 4704篇 |
1993年 | 4385篇 |
1992年 | 5548篇 |
1991年 | 5711篇 |
1990年 | 5426篇 |
1989年 | 5353篇 |
1988年 | 4703篇 |
1987年 | 4634篇 |
1986年 | 4454篇 |
1985年 | 4590篇 |
1984年 | 4146篇 |
1983年 | 3853篇 |
1982年 | 3095篇 |
1981年 | 2961篇 |
1980年 | 2887篇 |
1979年 | 3500篇 |
1978年 | 3048篇 |
1977年 | 2813篇 |
1976年 | 2630篇 |
1975年 | 2506篇 |
1974年 | 2672篇 |
1973年 | 2754篇 |
1972年 | 2454篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
41.
42.
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
43.
44.
45.
In a feeding trial lasting for months Halothane-positive fattening pigs were put on a diet containing different concentrations of vitamin E and selenium. After a Myostress application vitamin E and selenium were additionally injected in order to examine stress resistance (CK-test) and regenerative capacity (histological examination of Musculus longissimus dorsi) of skeletal muscle. The study revealed that neither high dietary levels of vitamin E/selenium nor a vitamin E/selenium treatment applied after stress are capable of preventing stress related myopathy nor can they influence its healing up favourably. 相似文献
46.
Epidermal growth factor (EGF)-like activity was measured in mares' colostrum and milk by radioreceptor assay. Milk samples were collected from 22 mares 1 or more times during early lactation. Samples of colostrum were taken after parturition and before the foal first suckled (presuckle), within 6 hours after the foal first suckled (postsuckle), and on days 1, 2, 4, and 8 of lactation. In the 5 mares from which milk samples were obtained at each sampling time, presuckle colostral mean EGF-like activity (17.8 ng/ml) was greatest (P less than 0.05). The mean values for EGF-like activity at all other sampling times were not significantly different from each other (postsuckle colostrum, 9.7 ng/ml; day 1, 9.6 ng/ml; day 2, 8.5 ng/ml; day 4, 8.0 ng/ml; day 8, 7.8 ng/ml). 相似文献
47.
M O Furr M V Crisman J Robertson O Barta W S Swecker 《Journal of the American Veterinary Medical Association》1992,201(2):307-309
Immune system dysfunction and immunoglobulin deficiency was diagnosed in a 2-year-old horse with disseminated lymphosarcoma. Prolonged (35 days) parenteral nutrition was delivered to support the horse during a period in which immune function studies could be performed. Correction of nutritional compromise by use of parenteral nutrition did not correct the immunoglobulin deficiency, and results of lymphocyte phenotype testing did not indicate abnormal proportions of leukocytes. Lymphoblast transformation studies were suggestive of a circulating immunosuppressive factor in the horse's serum. Normal cell function was detected when the cells were stimulated in precolostral equine serum. 相似文献
48.
The influence of extruded oilseeds on total tract digestibility and ruminal digestion in dairy cows was studied in three cows fed a hay-concentrate (60.5/39.5; 3.7% fatty acids in diet on DM basis) control diet (C) or the same diet supplemented with raw (R) or extruded (ER) rapeseeds (8.0% fatty acids in diet DM). The experimental design was a 3 x 3 Latin square design. Compared with diet C, diets containing rapeseed decreased ruminal OM digestibility (9.5%, P less than .10) and increased (P less than .05) the proportion of propionate in ruminal fluid VFA. Extrusion had no effect on DM and OM total tract digestibilities and increased (P less than .10) N digestion. Microbial N flow at the duodenum was calculated taking into account solid-adherent bacteria (SAB) and liquid-associated bacteria (LAB). Duodenal flows of total, SAB, and LAB of OM and N did not change with diet. Extrusion of the rapeseeds did not modify (P less than .10) the proportion of bacterial N at the duodenum and had no effect on crude fiber digestibility. This trial demonstrates that rapeseeds in hay-based diets can be fed at levels of up to 14% of the diet without adversely affecting crude fiber digestibility. 相似文献
49.
Osteomyelitis caused by Cryptococcus neoformans was diagnosed in a three-year-old male Irish wolfhound. The case details and radiological findings of radiolucency and periosteal reaction of the left third metatarsal bone had lead to an initial diagnosis of a malignant bone tumour. Biopsy revealed a fungal granuloma and culture identified the causal organism. A four month course of ketaconazole was instigated and the lameness resolved. Twelve months after the end of treatment there was no recurrence of the problem. 相似文献
50.