全文获取类型
收费全文 | 125862篇 |
免费 | 6077篇 |
国内免费 | 90篇 |
专业分类
林业 | 5634篇 |
农学 | 3619篇 |
基础科学 | 740篇 |
12866篇 | |
综合类 | 27425篇 |
农作物 | 4961篇 |
水产渔业 | 5269篇 |
畜牧兽医 | 62767篇 |
园艺 | 1439篇 |
植物保护 | 7309篇 |
出版年
2018年 | 1262篇 |
2017年 | 1357篇 |
2016年 | 1257篇 |
2015年 | 1147篇 |
2014年 | 1362篇 |
2013年 | 4090篇 |
2012年 | 2618篇 |
2011年 | 3227篇 |
2010年 | 2112篇 |
2009年 | 1996篇 |
2008年 | 3183篇 |
2007年 | 3196篇 |
2006年 | 3002篇 |
2005年 | 2954篇 |
2004年 | 2826篇 |
2003年 | 2907篇 |
2002年 | 2751篇 |
2001年 | 3329篇 |
2000年 | 3300篇 |
1999年 | 2759篇 |
1997年 | 1130篇 |
1995年 | 1281篇 |
1993年 | 1137篇 |
1992年 | 2511篇 |
1991年 | 2637篇 |
1990年 | 2772篇 |
1989年 | 2795篇 |
1988年 | 2633篇 |
1987年 | 2547篇 |
1986年 | 2599篇 |
1985年 | 2607篇 |
1984年 | 2159篇 |
1983年 | 1928篇 |
1982年 | 1353篇 |
1981年 | 1285篇 |
1980年 | 1193篇 |
1979年 | 2133篇 |
1978年 | 1724篇 |
1977年 | 1526篇 |
1976年 | 1426篇 |
1975年 | 1605篇 |
1974年 | 2083篇 |
1973年 | 2083篇 |
1972年 | 2122篇 |
1971年 | 2040篇 |
1970年 | 1903篇 |
1969年 | 1669篇 |
1968年 | 1430篇 |
1967年 | 1573篇 |
1966年 | 1393篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
961.
W. C. Carefoot 《British poultry science》1995,36(2):205-207
1. An investigation was conducted among the progeny from crosses between Buff Rock and Light Sussex bantams, and between Buff Rock and Gold‐Pencilled Hamburgh bantams in order to ascertain whether the eumelanin restrictor genes Columbian (Co) and Dark‐brown (Db) were present in the genome of the Buff Rock.
2. The Light Sussex and Gold‐Pencilled Hamburgh bantams used in this study were known to be Co/ Co db+ / db+ and co+ / co+ Db/ Db respectively.
3. In both F2 generations the least eumelanin restricted segregants were as the parent mated with the Buff Rock, thus demonstrating the Buff Rock bantam tested to be Co/ Co Db/ Db, or possess similar alleles at these loci.
4. The Buff Rock bantam male was found to be heterozygous for a eumelanin inhibitor gene which appears to be dominant white (I). 相似文献
962.
G. Jager H. Velvis 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(4):467-478
The position of plants withRhizoctonia solani sclerotia (black scurf) on progeny tubers was mapped for an experimental field at Haren where potatoes were grown continuously and in rotation with other crops for five successive years, and for another field at Borgercompagnie with a 12 frequency of potatoes during three potato crops. Initially, the distribution of plants with black scurf on both fields was rather dense and homogeneous. In the following years the distribution became heterogeneous and patchy. The local decline ofR. solani AG 3 (the common potato pathogen) in Haren was apparently caused by an unknown factor selectively suppressingR. solani AG 3, while simultaneouslyR. solani AG 5 increased in mass. This AG 5 type proved to be an inferior competitor of AG 3 on the potato plant in a laboratory experiment. The specificR. solani antagonistVerticillium biguttatum did not play a role. A similar factor could have reduced the formation of black scurf in the experimental field at Borgercompagnie, whereV. biguttatum was also too infrequent to account for the decline.R. solani AG 5 was not present here and could not indicate the presence of a selective factor against AG 3. 相似文献
963.
964.
965.
966.
967.
968.
969.
A comparison of paleobotanical records with archeological and ethnographic evidence from the Pacific Northwest shows a strong correlation between the expansion of Western red cedar (Thuja plicata) in coastal forests between 5000 and 2500 years ago and the evolution of a massive woodworking technology by native cultures. This suggests that an important component of cultural development was environmentally constrained until large cedar trees, the basic resource for canoe-building and plank-house construction, had become available in late Holocene time. 相似文献
970.