全文获取类型
收费全文 | 63318篇 |
免费 | 2889篇 |
国内免费 | 55篇 |
专业分类
林业 | 2602篇 |
农学 | 1670篇 |
基础科学 | 435篇 |
6241篇 | |
综合类 | 14871篇 |
农作物 | 2492篇 |
水产渔业 | 2405篇 |
畜牧兽医 | 31418篇 |
园艺 | 665篇 |
植物保护 | 3463篇 |
出版年
2018年 | 541篇 |
2017年 | 577篇 |
2016年 | 566篇 |
2014年 | 573篇 |
2013年 | 1915篇 |
2012年 | 1261篇 |
2011年 | 1500篇 |
2010年 | 943篇 |
2009年 | 918篇 |
2008年 | 1467篇 |
2007年 | 1436篇 |
2006年 | 1433篇 |
2005年 | 1445篇 |
2004年 | 1365篇 |
2003年 | 1434篇 |
2002年 | 1390篇 |
2001年 | 1503篇 |
2000年 | 1484篇 |
1999年 | 1212篇 |
1997年 | 540篇 |
1995年 | 598篇 |
1994年 | 576篇 |
1993年 | 564篇 |
1992年 | 1311篇 |
1991年 | 1395篇 |
1990年 | 1449篇 |
1989年 | 1490篇 |
1988年 | 1400篇 |
1987年 | 1357篇 |
1986年 | 1400篇 |
1985年 | 1375篇 |
1984年 | 1150篇 |
1983年 | 1006篇 |
1982年 | 718篇 |
1981年 | 689篇 |
1980年 | 644篇 |
1979年 | 1127篇 |
1978年 | 916篇 |
1977年 | 819篇 |
1976年 | 769篇 |
1975年 | 860篇 |
1974年 | 1126篇 |
1973年 | 1063篇 |
1972年 | 1129篇 |
1971年 | 1080篇 |
1970年 | 1022篇 |
1969年 | 874篇 |
1968年 | 710篇 |
1967年 | 844篇 |
1966年 | 693篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
Stump removal was found to singnificantly reduce killing byFomes annosus in second rotation crops of pine. Poisoning andgirdling of trees prior to felling and also stump poisoningfailed to control the disease. In this experiment no significantdifferences were detected in the susceptibility of Scots andCorsican pine to attack. Increasing periods of delay beforereplanting resulted in less mortality. An equation is presented,based on factors of the first rotation crop which may be usedto predict losses likely to occur when a site is replanted.Root attack by F. annosus results in reduced growth and yieldas well as mortality. The results from the experiment are discussed in trems of themangement of pine crops attacted by F. annosus in Theford Chase. 相似文献
84.
85.
86.
87.
88.
89.
W. G. Burton 《Potato Research》1967,10(1):74-80
Summary Richard Hakluyt (ca. 1553–1616) collected together and published first-hand accounts of the voyages of English seamen, including
several 16th century voyages to South America. These accounts provide some of the earliest published references to the potato,
but unfortunately they make no mention of its introduction into Europe. 相似文献
90.
A survey, covering some 140 fields, totalling 1540 acres, in Kent was conducted in 1961 on the effect of different methods of management on yields of perennial ryegrass and white clover seed. The main results were: (a) the majority of seed growers harvested seed from short-term leys and only a limited acreage of permanent pasture was used for producing seed. Yields of both ryegrass and clover seed were considerably higher on the younger leys; (b) the highest seed yields in 1961 were obtained from fields where sheep grazing was stopped on 24 May. However, a large number of growers continued sheep grazing well after this date: (c) mechanical defoliation, especially when used to supplement sheep grazing, proved an effective method for producing high yields of clover seed; (d) honey bees are important in increasing seed yields, particularly on recently sown leys; (e) combine harvesting from the swath was the most common method of harvesting and no instance of the use of tripods was reported. Seed yields from baling methods were generally low, but direct combining produced a high average yield of clover seed. From these results it was concluded that there was much scope for raising the general level of clover seed yields, especially by giving greater attention to details of management. 相似文献