全文获取类型
收费全文 | 23120篇 |
免费 | 1506篇 |
国内免费 | 222篇 |
专业分类
林业 | 1980篇 |
农学 | 1077篇 |
基础科学 | 200篇 |
3502篇 | |
综合类 | 2577篇 |
农作物 | 782篇 |
水产渔业 | 1469篇 |
畜牧兽医 | 11113篇 |
园艺 | 484篇 |
植物保护 | 1664篇 |
出版年
2023年 | 160篇 |
2022年 | 181篇 |
2021年 | 241篇 |
2020年 | 296篇 |
2019年 | 328篇 |
2018年 | 614篇 |
2017年 | 555篇 |
2016年 | 575篇 |
2015年 | 501篇 |
2014年 | 521篇 |
2013年 | 1048篇 |
2012年 | 918篇 |
2011年 | 999篇 |
2010年 | 732篇 |
2009年 | 620篇 |
2008年 | 898篇 |
2007年 | 984篇 |
2006年 | 829篇 |
2005年 | 857篇 |
2004年 | 701篇 |
2003年 | 732篇 |
2002年 | 602篇 |
2001年 | 952篇 |
2000年 | 893篇 |
1999年 | 734篇 |
1998年 | 218篇 |
1997年 | 194篇 |
1996年 | 175篇 |
1995年 | 218篇 |
1994年 | 195篇 |
1993年 | 163篇 |
1992年 | 427篇 |
1991年 | 456篇 |
1990年 | 424篇 |
1989年 | 421篇 |
1988年 | 395篇 |
1987年 | 417篇 |
1986年 | 357篇 |
1985年 | 298篇 |
1984年 | 268篇 |
1983年 | 229篇 |
1982年 | 145篇 |
1979年 | 250篇 |
1978年 | 170篇 |
1977年 | 143篇 |
1975年 | 147篇 |
1974年 | 167篇 |
1973年 | 167篇 |
1971年 | 155篇 |
1969年 | 156篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
A new pest in oilseed rape the cabbage root fly (Delia radicum L.) has succeded to establish – at least regional –during the recent years. It is not easy to monitor the cabbage root fly. Although the usual yellow water trap works quite well, it is still difficult for the farmers to determine Delia radicum exactly. The amount of infestation can be assessed best in the middle of November by analysing the damages of the roots. In this article a classification scheme is proposed. It is also difficult to control this pest. While applications of Pyrethroids against the imagines and the use of Dimethoat against the larva mostly showed only little effect in the tests, some new dressing-substances proved better against the standard “Chinook” (Imidacloprid+beta-Cyfluthrin). To forward this research and to clarify factors, which influence the infestation, a project titled “Possibilities of defence and control of cabbage root fly in winter oilseed rape” has been started in November 2003. Eight crop-protection services at German Federal State level and the BBA are involved in this project, which is supported by UFOP. 相似文献
72.
Patrick Rehmann Andrea Gr?ne Bruno Gottstein Jürg V?llm Heinz Sager Martin Janovsky Luca N Bacciarini 《Journal of veterinary diagnostic investigation》2005,17(2):183-186
Five animals in a colony of cynomolgus monkeys (Macaca fascicularis) died or were euthanatized because of alveolar echinococcosis, during a period of 5 years. The remainder of the colony was screened for possible infection with Echinococcus multilocularis, using serology and ultrasonography. A total of 46 animals out of a group of 55 were examined. The presence of anti-Em2 antibodies analyzed with enzyme-linked immunosorbent assay was demonstrated in 3 monkeys. In 2 of these 3 monkeys, multilocular structures compatible with metacestodal cysts in the liver were identified, using ultrasonography. The presence of alveolar echinococcosis was subsequently confirmed at postmortem examination in 1 animal. The other animals are still alive. Two other monkeys were negative in the serological examination but had cystic structures in the liver, which were identified as bile duct cysts at postmortem examination in 1 animal. The other monkey is still alive. These findings suggest that serology for antibodies against the Em2 antigen may represent a useful method in identifying animals that might be infected with E. multilocularis and are therefore at risk of developing fatal alveolar echinococcosis. 相似文献
73.
74.
75.
76.
77.
78.
79.
80.
N. J. Grünwald F. Workneh S. Hu A. H. C. van Bruggen 《European journal of plant pathology / European Foundation for Plant Pathology》1997,103(1):55-63
Testing of soil samples in greenhouse assays for suppressiveness to soilborne plant pathogens requires a considerable investment in time and effort as well as large numbers of soil samples. To make it possible to process large numbers of samples efficiently, we compared an in vitro growth assay with a damping-off assay using Pythium aphanidermatum as the test organism on tomato seedlings. The in vitro test compares the radial growth or relative growth of the fungus in soil to that in autoclaved soil and reflects suppressiveness of soils to the pathogen. We used soils from a field experiment that had been farmed either organically or conventionally and into which a cover crop (oats and vetch in mixture) had been incorporated 0, 10, 21, and 35 days previously. We obtained a significant, positive correlation between damping-off severities of tomato seedlings in damping-off assays and both relative and radial growth in vitro. In addition, radial and relative growth of P. aphanidermatum in the in vitro assay were positively correlated with several carbon and nitrogen variables measured for soil and incorporated debris. We did not find differences between the two farming systems for either growth measures of P. aphanidermatum or disease severities on tomato at different stages of cover crop decomposition. The in vitro assay shows potential for use with any fungus that exhibits rapid saprophytic growth, and is most suitable for routine application in suppressiveness testing. 相似文献