全文获取类型
收费全文 | 30820篇 |
免费 | 1539篇 |
国内免费 | 2434篇 |
专业分类
林业 | 2848篇 |
农学 | 2422篇 |
基础科学 | 1582篇 |
3825篇 | |
综合类 | 9712篇 |
农作物 | 2147篇 |
水产渔业 | 1736篇 |
畜牧兽医 | 7351篇 |
园艺 | 1552篇 |
植物保护 | 1618篇 |
出版年
2024年 | 100篇 |
2023年 | 360篇 |
2022年 | 819篇 |
2021年 | 910篇 |
2020年 | 889篇 |
2019年 | 892篇 |
2018年 | 725篇 |
2017年 | 1228篇 |
2016年 | 1013篇 |
2015年 | 1397篇 |
2014年 | 1395篇 |
2013年 | 1586篇 |
2012年 | 2350篇 |
2011年 | 2294篇 |
2010年 | 1911篇 |
2009年 | 1732篇 |
2008年 | 1663篇 |
2007年 | 1566篇 |
2006年 | 1368篇 |
2005年 | 1771篇 |
2004年 | 1343篇 |
2003年 | 997篇 |
2002年 | 766篇 |
2001年 | 743篇 |
2000年 | 515篇 |
1999年 | 421篇 |
1998年 | 167篇 |
1997年 | 137篇 |
1995年 | 94篇 |
1994年 | 103篇 |
1992年 | 190篇 |
1991年 | 211篇 |
1990年 | 214篇 |
1989年 | 178篇 |
1988年 | 211篇 |
1987年 | 142篇 |
1986年 | 153篇 |
1985年 | 132篇 |
1984年 | 104篇 |
1979年 | 139篇 |
1978年 | 96篇 |
1975年 | 137篇 |
1974年 | 130篇 |
1973年 | 116篇 |
1972年 | 138篇 |
1971年 | 120篇 |
1969年 | 103篇 |
1968年 | 115篇 |
1967年 | 125篇 |
1966年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
51.
52.
A ten-year-old female poodle was presented for left hindlimb lameness. Radiographically, irregular intramedullary densities of long bones (bone infarcts) and a lytic lesion in the left distal femur were detected. Two years after the first examination, the lesions in the distal femur were definitely identified as osteosarcoma and the dog was euthanized. Pathological and histological changes of the bone infarcts as well as of the osteosarcoma are described. Regarding bibliographical data, occurrence and aetiopathogenesis of osteosarcoma associated with multifocal bone infarction in man and dog are discussed. 相似文献
53.
With the help of a new synthetic material follicles and corpora lutea from the ovaries of 80 cows in different stages of the sexual cycle were examined for modifications of their blood vessel architecture. In the theca externa the main artery which runs towards the follicle, separates into arterioles of which capillaries derive in the theca interna, building a basket-like network around the zona granulosa. After ovulation the follicle wall forms characteristic fields. Capillaries grow into the zona granulosa and thus the folds form the lobular structure of the corpus luteum. Capillaries which rise from the ruptured part of the follicle, spread centripetally and together with lutein cells they build up the not lobulated cupola of the corpus luteum. The regression of the corpus luteum starts around the 16th day of the cycle, beginning at the capillary network of the cupola. A contraction of the vessels and a quick decrease of the volume follow. 相似文献
54.
Two cases of H.c.c. which occurred in winter 1987 in Vienna are described. Case one was a female Chow-Chow, 8 weeks of age, that died from the peracute form of the disease. The diagnosis was confirmed by histology and direct immunofluorescence. Case two, a 9-month old female Kuvacz, showed clinical signs of the subacute form of H.c.c. She was hospitalized and therapy was successful. The disease was diagnosed by the typical clinical signs and the raise of antibodies in paired serum samples. Etiology, clinical signs and immunology of H.c.c. are discussed. 相似文献
55.
56.
The kidney's microvascularization of the Pudu pudu is mostly similar to that of domestic animals. The renal parenchymatous arteries do not give off capsular branches. The majority of the Pudu pudu's glomerula shows spherical shape. Glomerula next to the medulla have a diameter which is an average of 25 microns larger than the diameter of those situated more peripherally. Their volume is comparable to that of the angora rabbit. The capillaries form anastomosis in the inner and outer part of the glomerulus. 相似文献
57.
浅谈进一步提高教学质量的措施 总被引:1,自引:0,他引:1
提高教学质量是促进学校全面发展的关键因素之一,有着重要的意义.本文从提高教师自身素质、激发学生能动性、加强教学管理三个方面阐述了进一步提高教学质量的措施. 相似文献
58.
The occurrence of hide damage light flecks and spots was determined on tanned hides from 28 herds during a period of 8 to 12 months. Light flecks and spots are described as small areas of grain loss up to 3 mm in diameter that are seen on dyed crust cattle leather. Damage was found on 75.8% of all hides. The neck and shoulders were the anatomical region with the highest prevalence of damage. Sixty-eight per cent of all hides had light flecks and spots in this region. The forelimbs and dewlap were the anatomical region with the second highest occurrence with a prevalence of 39.1%. This distribution corresponded to the known distribution of lice in cattle. No significant differences were observed in age, sex, prevalence of lice in the herd assessed in March or infestations with different lice species. The frequency of light flecks and spots varied significantly during the year. The frequency was highest in the late winter and early spring, decreased significantly during the summer and was lowest in the autumn. This variation supported the importance of lice in the development of light flecks and spots and suggested a relatively long healing period for the damages induced by lice. 相似文献
59.
60.
3月份迄今.国际石油价格的波段走势可谓“一枝独秀”.相较之下,CBOT大豆衍生品市场却呈现箱体振荡的走势.而国内油脂市场则延续基本面为主导的弱势寻底格局.市场再次验证了预测机构前期作出的油脂行情预测。本文立足于引发近期外围能源市场强势振荡加剧的关键性因素.结合中期我国油、籽市场的供需基本趋势,包括政策面调控导向的新动态.提示和分析下一阶段我国油脂市场可能存在的逆市波动风险。 相似文献