全文获取类型
收费全文 | 722篇 |
免费 | 35篇 |
专业分类
林业 | 150篇 |
农学 | 41篇 |
基础科学 | 4篇 |
148篇 | |
综合类 | 84篇 |
农作物 | 17篇 |
水产渔业 | 21篇 |
畜牧兽医 | 256篇 |
园艺 | 6篇 |
植物保护 | 30篇 |
出版年
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 19篇 |
2013年 | 43篇 |
2012年 | 24篇 |
2011年 | 32篇 |
2010年 | 10篇 |
2009年 | 17篇 |
2008年 | 41篇 |
2007年 | 31篇 |
2006年 | 19篇 |
2005年 | 26篇 |
2004年 | 39篇 |
2003年 | 28篇 |
2002年 | 25篇 |
2001年 | 26篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1973年 | 6篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1969年 | 7篇 |
1966年 | 5篇 |
1965年 | 6篇 |
1956年 | 5篇 |
1926年 | 9篇 |
1925年 | 7篇 |
1924年 | 5篇 |
1911年 | 6篇 |
排序方式: 共有757条查询结果,搜索用时 15 毫秒
11.
Effect of the eye fluke Diplostomum spathaceum on fish growth has remained somewhat unclear because 1) the question has not been subjected to experimental examination with treatment-control setup and 2) growth has not been related to the coverage of parasite-induced cataracts in a quantitative manner. We examined effects of the parasite on growth and competitive ability of whitefish (Coregonus lavaretus) in experimental conditions resembling those at fish farms by maintaining groups of exposed and control fish, as well as mixed groups from both treatments, under optimal conditions for 8 weeks. Contrary to our expectations, we did not observe differences in fish growth between the treatments. However, at the level of individual fish, parasite-induced cataracts had a negative effect on weight of the exposed fish but this took place only when the cataract coverage reached 100% in both eyes. No effect of the infection on competitive ability of fish was observed in mixed treatments which may be related to patterns of food distribution in the tanks or cues received by the fish from less infected conspecifics. Overall, the results suggest that effects of D. spathaceum on fish growth become apparent only in cases of very high cataract coverage, and that feeding regimes and the shape of the cataract coverage distribution in a fish group are important determinants of the magnitude of these effects. 相似文献
12.
The agroecosystem models THESEUS and OPUS were tested with data obtained from three agricultural experimental field plots on sandy soils without groundwater located at the moraine landscape in East Brandenburg, Germany. At each of these plots, a separate agricultural management practice was applied. Measurements of soil water contents, pressure heads, above‐ground crop biomass, and crop yield from these three plots were compared with the corresponding simulation results of both models. The comparisons of simulated with measured outputs were analyzed using the modeling‐efficiency index IA. According to these analyses, both models simulated adequately the time courses of volumetric soil water contents and above‐ground crop biomass, but the time courses of pressure heads were predicted with a lower quality by both models. As for the pressure heads, the yields simulated with both models showed greater discrepancies in comparison with the observed ones. This indicates the need of a site‐specific parameter calibration of the crop‐growth modules, especially for that included in OPUS . 相似文献
13.
14.
European Journal of Forest Research - 相似文献
15.
Otto Alt 《Forstwissenschaftliches Centralblatt》1898,20(5-6):287-294
Ohne Zusammenfassung 相似文献
16.
17.
Otto Lüders 《Journal of pest science》1949,22(9):138-139
Ohne Zusammenfassung 相似文献
18.
Gartenbaurat Friedrich Wenck 《Journal of pest science》1948,21(2):21-22
Ohne Zusammenfassung 相似文献
19.
Jean-Franois Chollet Jean-Louis Bonnemain Lone Miginiac Otto Rohr 《Pest management science》1990,29(4):427-435
Twenty-four I-substituted-I-aryl-2-triazol-I-yl-ethanols were prepared by the reaction between acetylenic, propargylic or allylic organometallics and aryl triazolylmethyl ketones. These were tested for antifungal activity against ten phytopathogenic fungi of different taxonomic classes. EC80 values were determined for the seven most active compounds and for two commercial compounds, hexaconazole and flusilazole. In these tests, the fungicidal activity of the new compounds was generally lower than that of the two reference triazoles except for two products which were more active than hexaconazole and flusilazole against powdery mildew on barley. 相似文献
20.
Jos P. M. Vink Peter Nrtersheuser Otto Richter Bernd Diekkrüger Klaas P. Groen 《Pest management science》1994,40(4):285-292
Results of field measurements and laboratory experiments were used to simulate the behaviour of 1,3-dichloropropene (1,3-D) in a loamy sand soil. Microbial activity was described using pre-set conditions to compute transformation rates as dependent on compound concentrations and temperature. These kinetics could only be analysed using non-linear transformation rates. To link the development of microbial populations and the consumption of the compound over time, an iterative technique was used to estimate the necessary parameters. 相似文献