全文获取类型
收费全文 | 2218篇 |
免费 | 123篇 |
国内免费 | 2篇 |
专业分类
林业 | 86篇 |
农学 | 31篇 |
基础科学 | 22篇 |
289篇 | |
综合类 | 705篇 |
农作物 | 51篇 |
水产渔业 | 122篇 |
畜牧兽医 | 827篇 |
园艺 | 42篇 |
植物保护 | 168篇 |
出版年
2021年 | 17篇 |
2020年 | 36篇 |
2019年 | 28篇 |
2018年 | 29篇 |
2017年 | 30篇 |
2016年 | 32篇 |
2015年 | 32篇 |
2014年 | 35篇 |
2013年 | 92篇 |
2012年 | 99篇 |
2011年 | 137篇 |
2010年 | 87篇 |
2009年 | 50篇 |
2008年 | 152篇 |
2007年 | 147篇 |
2006年 | 144篇 |
2005年 | 124篇 |
2004年 | 116篇 |
2003年 | 114篇 |
2002年 | 150篇 |
2001年 | 44篇 |
2000年 | 42篇 |
1999年 | 27篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 22篇 |
1995年 | 22篇 |
1994年 | 29篇 |
1993年 | 29篇 |
1992年 | 29篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 23篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1974年 | 14篇 |
1972年 | 11篇 |
1970年 | 9篇 |
1969年 | 11篇 |
1968年 | 11篇 |
1966年 | 8篇 |
排序方式: 共有2343条查询结果,搜索用时 15 毫秒
1.
Edwin H. Robinson Menghe H. Li Bruce B. Manning 《Journal of the World Aquaculture Society》2001,32(1):68-71
Abstract.— This study was conducted to evaluate corn gluten feed as an alternative feedstuff in the diet of pond-raised channel catfish Ictalurus punctatus . Three 32%-protein diets containing 0%, 25%, or 50% corn gluten feed were tested. Channel catfish fingerlings (average weight: 57 g/fish) were stocked into 15 0.04-ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed to satiation once daily for a 147-d growing period. No differences were observed in feed consumption, weight gain, feed conversion ratio, survival, or fillet protein concentration among fish fed the test diets. Fish fed diets containing 25% and 50% corn gluten feed exhibited a lower level of visceral fat and a higher carcass yield than fish fed the control diet without corn gluten feed. The diet containing 50% corn gluten feed resulted in a lower level of fillet fat and a higher level of moisture than the control diet. There were no visible differences in the coloration of skin or fillet of channel catfish fed diets with and without corn gluten feed. Results from this study indicated that channel catfish can efficiently utilize corn gluten feed at levels up to 50%n without adverse effect on feed palatability, weight gain, or feed efficiency. Corn gluten feed may be beneficial in reducing fattiness of channel catfish and improving carcass yield by reducing the digestible energy to protein ratio of the diet. 相似文献
2.
A total of 739 cattle from nine breeds maintained at the Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska were tested for 42 class I antigens of the bovine major histocompatibility system (BoLA). Each antigen appears to be the product of a distinct co-dominant allele of the BoLA-A locus. The number of antigens present in each breed ranged from a minimum of 10 in Hereford to a maximum of 21 in Charolais cattle. There were large differences among breeds in the frequencies of antigens. The effect of each antigen on birth weight, preweaning weight gain and postweaning weight gain was estimated in a gene substitution model. Each breed was analyzed separately. There were significant effects of some BoLA antigens on birth weight, preweaning weight gain and postweaning weight gain, which is consistent with previous reports showing associations between the major histocompatibility system and growth parameters in mice, rats and pigs. However, further research is necessary to confirm these findings and to determine the biological mechanisms underlying these associations. 相似文献
3.
Michael S. Stone Ian B. Johnstone Marjory Brooks Trent K. Bollinger Susan M. Cotter 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1994,8(1):57-61
A circulating anticoagulant was detected in a 2-year-old Chesapeake Bay Retriever with hemolytic anemia, nephrotic syndrome, thrombocytopenia, polyarthropathy, and pulmonary thromboembolism. A persistent prolongation of the activated partial thromboplastin time (aPTT) was detected, and it did not correct with repeated administration of fresh frozen plasma. The aPTT was still prolonged, with a 1:1 mixture of patient's plasma and normal dog plasma in vitro, suggesting the presence of a circulating inhibitor. Results of assays to characterize the inhibitor were compatible with those described for the lupus anticoagulant in human patients with systemic lupus erythematosus. Paradoxically, patients having the lupus anticoagulant are at increased risk for thrombosis. Pulmonary thromboembolism has been described as a frequent complication of immune-mediated hemolytic anemia in the dog, and the presence of a circulating anticoagulant should be considered as a potential mechanism. 相似文献
4.
5.
Six shipments totaling 3452 mummies of the blackmargined aphid,Monellia caryella (Fitch), parasitized withAphelinus perpallidus Gahan, were obtained by air freight during the years 1982-1985 from Texas A&M Research Center, El Paso, Texas. About two-thirds of the mummies did not yield parasites. A colony ofA. perpallidus was established in the laboratory. Under laboratory conditions the percentage of emerged parasites was higher than that in the imported mummies, and the parasite had very limited impact on the aphid population. Field releases of the parasite were made but no establishment ofA. perpallidus was observed through the years. 相似文献
6.
Olson ME Bruce J 《The Canadian veterinary journal. La revue veterinaire canadienne》1986,27(12):523-527
This article describes the surgical procedures for the ovariectomy, ovariohysterectomy and orchidectomy in rodents and rabbits. The indications for each procedure are outlined and effective and safe anesthetics are described. Preoperative and postoperative care is also discussed. 相似文献
7.
Stone R 《Science (New York, N.Y.)》1994,266(5184):360-361
8.
Stone R 《Science (New York, N.Y.)》1994,263(5151):1218-1219
9.
10.
Stone R 《Science (New York, N.Y.)》1992,257(5077):1730-1731