全文获取类型
收费全文 | 7670篇 |
免费 | 318篇 |
国内免费 | 8篇 |
专业分类
林业 | 340篇 |
农学 | 398篇 |
基础科学 | 90篇 |
1080篇 | |
综合类 | 437篇 |
农作物 | 297篇 |
水产渔业 | 237篇 |
畜牧兽医 | 4035篇 |
园艺 | 132篇 |
植物保护 | 950篇 |
出版年
2023年 | 36篇 |
2022年 | 34篇 |
2021年 | 78篇 |
2020年 | 96篇 |
2019年 | 107篇 |
2018年 | 122篇 |
2017年 | 126篇 |
2016年 | 132篇 |
2015年 | 112篇 |
2014年 | 155篇 |
2013年 | 533篇 |
2012年 | 360篇 |
2011年 | 416篇 |
2010年 | 217篇 |
2009年 | 209篇 |
2008年 | 378篇 |
2007年 | 381篇 |
2006年 | 315篇 |
2005年 | 321篇 |
2004年 | 322篇 |
2003年 | 279篇 |
2002年 | 275篇 |
2001年 | 251篇 |
2000年 | 227篇 |
1999年 | 212篇 |
1998年 | 62篇 |
1997年 | 58篇 |
1996年 | 66篇 |
1995年 | 67篇 |
1994年 | 46篇 |
1993年 | 55篇 |
1992年 | 113篇 |
1991年 | 123篇 |
1990年 | 145篇 |
1989年 | 122篇 |
1988年 | 112篇 |
1987年 | 91篇 |
1986年 | 77篇 |
1985年 | 92篇 |
1984年 | 76篇 |
1983年 | 50篇 |
1982年 | 37篇 |
1981年 | 45篇 |
1980年 | 48篇 |
1979年 | 48篇 |
1974年 | 31篇 |
1973年 | 32篇 |
1972年 | 40篇 |
1971年 | 42篇 |
1969年 | 31篇 |
排序方式: 共有7996条查询结果,搜索用时 62 毫秒
991.
Diversity in starch, protein and mineral composition of sorghum landrace accessions from Ethiopia 总被引:1,自引:1,他引:0
Abe Shegro Nemera Geleta Shargie Angeline van Biljon Maryke Tine Labuschagne 《Journal of Crop Science and Biotechnology》2012,15(4):275-280
Sorghum (Sorghum bicolor (L.) Moench) is an important food crop in arid and semi-arid tropics where it is grown mainly due to its drought tolerance. In Ethiopia, sorghum is grown in different agro-ecological zones primarily for food. Landraces are widely cultivated in the region due to their adaptation to the growing conditions and other characteristics such as food quality, quantity, and quality of by-products. The objective of this research was to determine the genetic variation in protein, mineral composition, total starch and its components in sorghum landraces collected from the western regions of Ethiopia. Sorghum whole grains were analyzed for crude protein, total starch and its components, and mineral profile (calcium, magnesium, potassium, phosphorus, iron, manganese, zinc, and sodium). The analysis of variance showed significant differences among the sorghum landraces in nutritional composition. There was highly significant correlation between phosphorus and magnesium, and between zinc and phosphorus and protein which indicated that some interaction existed in absorption and translocation between minerals and protein content. The genetic variation found among the sorghum landrace accessions in chemical composition can be exploited in the breeding program. 相似文献
992.
993.
994.
995.
Hulshof RB Berndt A Gerrits WJ Dijkstra J van Zijderveld SM Newbold JR Perdok HB 《Journal of animal science》2012,90(7):2317-2323
The objective of this study was to determine the effect of dietary nitrate on methane emission and rumen fermentation parameters in Nellore × Guzera (Bos indicus) beef cattle fed a sugarcane based diet. The experiment was conducted with 16 steers weighing 283 ± 49 kg (mean ± SD), 6 rumen cannulated and 10 intact steers, in a cross-over design. The animals were blocked according to BW and presence or absence of rumen cannula and randomly allocated to either the nitrate diet (22 g nitrate/kg DM) or the control diet made isonitrogenous by the addition of urea. The diets consisted of freshly chopped sugarcane and concentrate (60:40 on DM basis), fed as a mixed ration. A 16-d adaptation period was used to allow the rumen microbes to adapt to dietary nitrate. Methane emission was measured using the sulfur hexafluoride tracer technique. Dry matter intake (P = 0.09) tended to be less when nitrate was present in the diet compared with the control, 6.60 and 7.05 kg/d DMI, respectively. The daily methane production was reduced (P < 0.01) by 32% when steers were fed the nitrate diet (85 g/d) compared with the urea diet (125 g/d). Methane emission per kilogram DMI was 27% less (P < 0.01) on the nitrate diet (13.3 g methane/kg DMI) than on the control diet (18.2 g methane/kg DMI). Methane losses as a fraction of gross energy intake (GEI) were less (P < 0.01) on the nitrate diet (4.2% of GEI) than on the control diet (5.9% of GEI). Nitrate mitigated enteric methane production by 87% of the theoretical potential. The rumen fluid ammonia-nitrogen (NH(3)-N()) concentration was significantly greater (P < 0.05) for the nitrate diet. The total concentration of VFA was not affected (P = 0.61) by nitrate in the diet, while the proportion of acetic acid tended to be greater (P = 0.09), propionic acid less (P = 0.06) and acetate/propionate ratio tended to be greater (P = 0.06) for the nitrate diet. Dietary nitrate reduced enteric methane emission in beef cattle fed sugarcane based diet. 相似文献
996.
A good intake of fluids and essential nutrients in the first fourteen days is of vital importance to recuperating animals. Moreover, it is important to encourage cats and dogs to eat after illness or surgery, in order to promote optimal functioning of the gut and the immune system. Enteral nutrition is to be preferred to nasogastric feeding or parenteral nutrition. In the first stage of recovery, during the first 24 to 48 hours, it is important to feed the gut' with nutrients, and thereafter, in the second stage of recovery (after day 3), the calorie intake can be increased. Timely nutritional support with nutraceuticals, such as arginine, glutamine, taurine, long-chain polyunsaturated omega-3 fatty acids, and prebiotic fibres, can considerably shorten the recovery period of cats and dogs after illness or surgery 相似文献
997.
998.
999.
1000.