全文获取类型
收费全文 | 1623篇 |
免费 | 28篇 |
国内免费 | 14篇 |
专业分类
林业 | 166篇 |
农学 | 131篇 |
基础科学 | 19篇 |
426篇 | |
综合类 | 264篇 |
农作物 | 189篇 |
水产渔业 | 58篇 |
畜牧兽医 | 246篇 |
园艺 | 79篇 |
植物保护 | 87篇 |
出版年
2023年 | 13篇 |
2022年 | 46篇 |
2021年 | 76篇 |
2020年 | 74篇 |
2019年 | 65篇 |
2018年 | 72篇 |
2017年 | 79篇 |
2016年 | 87篇 |
2015年 | 107篇 |
2014年 | 91篇 |
2013年 | 152篇 |
2012年 | 121篇 |
2011年 | 95篇 |
2010年 | 117篇 |
2009年 | 105篇 |
2008年 | 103篇 |
2007年 | 82篇 |
2006年 | 52篇 |
2005年 | 20篇 |
2004年 | 11篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 11篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1970年 | 2篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1959年 | 2篇 |
1958年 | 1篇 |
1937年 | 1篇 |
1936年 | 2篇 |
1928年 | 2篇 |
1870年 | 1篇 |
1868年 | 1篇 |
1863年 | 1篇 |
1860年 | 1篇 |
1857年 | 2篇 |
排序方式: 共有1665条查询结果,搜索用时 484 毫秒
1.
2.
Definitions of the notions of soil resilience and degradation of the soil-vegetation cover are suggested. These problems are considered with respect to vulnerable tundra ecosystems. The analysis of available experimental data made it possible to obtain empirical equations characterizing the relationships between the plant productivity and the soil properties. These equations can be used to predict the degree of soil degradation under particular types of technogenic loads and the soil and vegetation potential for the natural restoration or artificial rehabilitation of the soil-vegetation cover in tundra ecosystems. The results obtained can be applied for the development of optimal nature management strategies in the areas of oil and gas fields in the north. 相似文献
3.
4.
Alla M. Gol’Berg Shoshana Yathom Ahuva ALmogi-Labin G. Fridland-Wunder 《Phytoparasitica》1989,17(2):81-89
Adult populations ofMaladera matrida Argaman (Coleoptera: Scarabaeidae), a beetle highly injurious to agricultural crops, were studied in the coastal plain of Israel from 1985 to 1988. There were two generations annually. Adults emerged in March, April or May and disappeared in October or November. The beetles are on the wing, mate, and feed at twilight and in the dark. Feeding and mating behavior, sex ratio, and preferred food plants were studied. 相似文献
5.
Two entomophthoraceous species,Zoophthora radicans andEntomophthora planchoniana, were found on the yellow pecan aphid,Monellia costalis, shortly after it was introduced into Israel. This aphid is a new host forZ. radicans anywhere. The fungus was isolated in pure culture and artificially inoculated on three Dipteran species:Musca domestica, Drosophila melanogaster andCeratitis capitata, as well as on the HemipteranEmpoasca sp. from pecan. The identity ofZ. radicans and some new characters,e.g. the production of two kinds of rhizoids, are discussed. The possibility of usingM. domestica as a vector for artificial spread of the fungus, as a means of biological control of various insect pests, is advocated. 相似文献
6.
7.
8.
Tomas Tubritt Luc Delaby Trevor Gilliland Michael O’Donovan 《Grass and Forage Science》2020,75(3):253-265
The objective of this study was to compare the grazing efficiency of 30 perennial ryegrass varieties, differing in ploidy and heading date. Plots were grazed by lactating dairy cows and managed under a rotational grazing system with 19 grazing events occurring over two years. Pre-grazing and post-grazing compressed sward heights were measured with a rising plate meter. A mixed model was used to predict the post-grazing sward height of each variety based on year, grazing event, block and pre-grazing sward height. Residual grazed height (RGH) was derived as the difference between the actual and predicted post-grazing sward height and was used as the measure of grazing efficiency. Negative RGH values indicated that the actual herbage removed was greater than that predicted and so indicated a superior grazing efficiency. Varieties differed in their level of grazing efficiency (p < .001), with RGH values ranging from −0.38 to +0.34 cm. Tetraploid varieties exhibited significantly greater grazing efficiency performance than diploids (p < .001), with average RGH values of −0.13 and +0.13 cm respectively. A significant difference in grazing efficiency was found among recommended perennial ryegrass varieties that are not being recorded by mechanically harvested simulated grazing protocols. A variety reappraisal that included grazing efficiency could identify varieties capable of improving on-farm livestock productivity from grass. 相似文献
9.
10.
[Objectives]This study aimed to investigate the effects of ropivacaine-sufentanil epidural analgesia on labor and maternal and neonatal outcomes.[Methods]A tota... 相似文献