全文获取类型
收费全文 | 21893篇 |
免费 | 345篇 |
国内免费 | 1篇 |
专业分类
林业 | 4599篇 |
农学 | 1445篇 |
基础科学 | 145篇 |
3925篇 | |
综合类 | 1249篇 |
农作物 | 2239篇 |
水产渔业 | 1956篇 |
畜牧兽医 | 3245篇 |
园艺 | 1196篇 |
植物保护 | 2240篇 |
出版年
2023年 | 37篇 |
2022年 | 41篇 |
2021年 | 86篇 |
2020年 | 78篇 |
2019年 | 48篇 |
2018年 | 2865篇 |
2017年 | 2833篇 |
2016年 | 1323篇 |
2015年 | 209篇 |
2014年 | 174篇 |
2013年 | 382篇 |
2012年 | 1091篇 |
2011年 | 2444篇 |
2010年 | 2227篇 |
2009年 | 1374篇 |
2008年 | 1583篇 |
2007年 | 1864篇 |
2006年 | 347篇 |
2005年 | 363篇 |
2004年 | 356篇 |
2003年 | 428篇 |
2002年 | 285篇 |
2001年 | 187篇 |
2000年 | 219篇 |
1999年 | 105篇 |
1998年 | 36篇 |
1997年 | 38篇 |
1996年 | 46篇 |
1995年 | 80篇 |
1994年 | 46篇 |
1993年 | 36篇 |
1992年 | 35篇 |
1991年 | 27篇 |
1990年 | 27篇 |
1989年 | 27篇 |
1988年 | 42篇 |
1987年 | 18篇 |
1986年 | 34篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 20篇 |
1982年 | 15篇 |
1980年 | 29篇 |
1977年 | 27篇 |
1973年 | 15篇 |
1970年 | 15篇 |
1968年 | 17篇 |
1966年 | 15篇 |
1955年 | 14篇 |
1941年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
2.
T. Pudert A. Weyrich F. Geburek C. Herden M. Röcken 《Equine Veterinary Education》2021,33(11):e386-e392
Thymoma is a rare condition in horses. This case of a 24-year-old Warmblood gelding that was presented with oedema and signs of vascular congestion of the left forelimb caused by a thoracic mass is described. The diagnostic work-up included blood chemistry, cytology of pleural effusion, ultrasonography, radiography and the visualisation and collection of a tissue sample by thoracoscopy. Finally, post-mortem findings and histopathology revealed thymic epithelial neoplasia with histomorphologic features previously unreported in horses. The unique mixture of spindle-shaped and epithelioid tumour cells in combination with clear features of malignancy suggested the application of the Moran and Suster histological classification system for thymomas in humans (Moran and Suster, 2008, Curr. Treat. Options Oncol., 9, 288), which has not been reported in an equine case before and fits well to the present case. 相似文献
3.
4.
B. Götz 《Journal of pest science》1938,14(8):92-93
Ohne Zusammenfassung 相似文献
5.
6.
Revierförfter von Mühlen zu Solitude 《European Journal of Forest Research》1868,12(1):340-342
Ohne Zusammenfassung
Bergleiche Auguftheft diefer Bl?tter, in melchem gleichfalls auf die Wichtigfeit diefes Qegenftandes hingemiefen murde. Die
Red. 相似文献
7.
Abstract – Foraging juvenile fish with relatively high food demands are usually vulnerable to various aquatic and avian predators. To compromise between foraging and antipredator activity, they need exact and reliable information about current predation risk. Among direct predator-induced cues, visual and olfactory signals are considered to be most important. Food intake rates and prey-size selectivity of laboratory-reared, naive young-of-the-year (YOY) perch, Perca fluviatilis , were studied in experiments with Daphnia magna of two size classes: 2.8 and 1.3 mm as prey and northern pike, Esox lucius , as predator. Neither total intake rate nor prey-size selectivity was modified by predator kairomones alone (water from an aquarium with a pike was pumped into the test aquaria) under daylight conditions. Visual presentation of pike reduced total food intake by perch. This effect was significantly more pronounced (synergistic) when visual and olfactory cues were presented simultaneously to foraging perch. Moreover, the combination of cues caused a significant shift in prey-size selection, expressed as a reduced proportion of large prey in the diet. Our observations demonstrate that predator-induced olfactory cues alone are less important modifiers of the feeding behaviour of naive YOY perch than visual cues under daylight conditions. However, pike odour acts as a modulatory stimulus enhancing the effects of visual cues, which trigger an innate response in perch. 相似文献
8.
9.
10.
Dr. G. Götze 《Journal of pest science》1929,5(6):73-75
Ohne Zusammenfassung 相似文献