全文获取类型
收费全文 | 1426篇 |
免费 | 36篇 |
国内免费 | 7篇 |
专业分类
林业 | 50篇 |
农学 | 17篇 |
基础科学 | 17篇 |
53篇 | |
综合类 | 500篇 |
农作物 | 16篇 |
水产渔业 | 8篇 |
畜牧兽医 | 766篇 |
园艺 | 11篇 |
植物保护 | 31篇 |
出版年
2022年 | 6篇 |
2019年 | 16篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2014年 | 16篇 |
2013年 | 9篇 |
2012年 | 87篇 |
2011年 | 96篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 118篇 |
2007年 | 100篇 |
2006年 | 90篇 |
2005年 | 71篇 |
2004年 | 82篇 |
2003年 | 56篇 |
2002年 | 74篇 |
2001年 | 54篇 |
2000年 | 74篇 |
1999年 | 35篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 27篇 |
1991年 | 33篇 |
1990年 | 7篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1979年 | 9篇 |
1976年 | 7篇 |
1969年 | 6篇 |
1963年 | 7篇 |
1960年 | 12篇 |
1958年 | 5篇 |
1957年 | 6篇 |
1956年 | 7篇 |
1955年 | 6篇 |
1954年 | 5篇 |
1948年 | 5篇 |
1939年 | 6篇 |
排序方式: 共有1469条查询结果,搜索用时 15 毫秒
1.
<正>枣树是一种生态、经济兼用的树种,有较强抗性,适应性较广,同时还拥有抗干旱、耐盐碱、抗风湿等多种优良特性,适合在新疆地区进行大面积栽植。以下就直播酸枣嫁接及管理技术进行介绍。1 砧木培育1.1播种种子质量要求当年新鲜的含仁率高、种仁饱满、破碎率不超过5%、发芽率80%以上、净度达到95%以上的酸枣种子。选择 相似文献
2.
片面强调仔猪饲料中的蛋白质或能量能引起消化问题;过分依赖乳类饲料配料也能减缓对干料的适应。仔猪饲料制造商必须格外小心地选择饲料蛋白质来源,尤其需要注意原料的氨基酸平衡和其对蛋白质总的消化的影响。不过,除了氨基酸平衡外,有许多其它因素能影响仔猪对各种蛋白质来源的利用。了解蛋白质代谢的详细过程能使饲料制造商以可接受的成本获得最大可能的生产性能。蛋白质是一组相互关连的氨基酸,它们以特定的构型存在并具有某些特性。某种蛋白质中各种氨基酸的数量和比例决定了它在 相似文献
3.
从 5个阶段回顾了黑龙江省森工国有林区森林资源管理工作的历程 ,旨在警示提高对森林资源管理工作的认识 相似文献
5.
6.
7.
8.
Cribb AE Burgener DC Reimann KA 《The Canadian veterinary journal. La revue veterinaire canadienne》1988,29(8):654-657
Seven icteric dogs were determined to have bile duct obstruction secondary to chronic pancreatitis. All dogs had histories of intermittent vomiting and diarrhea. Alkaline phosphatase and alanine aminotransferase activities and total bilirubin concentrations were markedly elevated. Diagnosis was based on exploratory laparotomy and histological examination. Each dog had a 3 to 10 cm mass in the body of the pancreas and obstruction of the common bile duct. Three dogs treated with pancreatectomy, gastrojejunostomy, and cholecystojejunostomy died within five weeks. Three dogs treated with conservative surgical procedures were alive at 8, 16, and 26 months postoperatively. One dog was euthanized because of suspected neoplasia. Hepatic enzyme activity and bilirubin levels decreased markedly in the surviving dogs. Histological examination of the pancreatic masses indicated chronic pancreatitis. Hepatic biopsies revealed evidence of cholestasis. Chronic pancreatitis should be included in the differential diagnoses of icterus, bile duct obstruction, and masses in the pancreas. 相似文献
9.
Thurley DC 《New Zealand veterinary journal》1984,32(3):25-29
The teeth and various supporting and ancillary tissues were examined post mortem from two flocks of sheep, one of which had previously shown high deciduous incisor wear. Sheep were killed in groups selected on clinical signs at equivalent ages from birth to 116 weeks of age. At the end of this time the lengths of clinical crowns of the remaining deciduous incisor teeth in the high wear flock were not measurable, whereas the other flock had up to 5.5 mm in visible crown. Using the cingulum as a marker, measurements were made from extracted teeth of the attrition of the crown and size of the root. The tooth root did not grow substantially longer after the 13th week of the sheep;s life. Wear facets were just visible in some sheep at six weeks. More rapid wear occurred three times in the high wear flock. The first of these was relatively small and occurred between the 13th and 27th week of age in I1 and I2. The second was larger and occurred between the 38th and 57th week of age in the winter/spring period. A third period of wear, which was not measured from the cingulum, because this structure had by then been worn away, was seen in the remaining deciduous teeth between the ages of 91 and 110 weeks of age, i.e., during the second winter and spring. In the low wear flock the first of these periods of wear did not occur, the second was of shorter duration and smaller size, and the third equivocal. Eruption of the teeth after the 6th week was principally passive. There was no difference in the degree of wear of the molar teeth from the two flocks. Histological examination showed that the wear was compensated for by the deposition of reparative dentine in the pulp cavity. This usually gave the appearance of an ordered process. However, when wear was excessively rapid, a different, less orderly form of reparative dentine was laid down. In a few cases the reparative process was not fast enough, and a connection developed between the mouth and the pulp causing pulpitis. There was no histological evidence that the supportive tissues of the teeth, or the upper dental pad, contributed to the excessive wear. 相似文献
10.
Cassidy DC 《Science (New York, N.Y.)》1986,233(4766):896