全文获取类型
收费全文 | 377篇 |
免费 | 19篇 |
专业分类
林业 | 41篇 |
农学 | 5篇 |
基础科学 | 1篇 |
85篇 | |
综合类 | 34篇 |
农作物 | 14篇 |
水产渔业 | 45篇 |
畜牧兽医 | 138篇 |
园艺 | 17篇 |
植物保护 | 16篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 10篇 |
2014年 | 22篇 |
2013年 | 28篇 |
2012年 | 32篇 |
2011年 | 29篇 |
2010年 | 16篇 |
2009年 | 11篇 |
2008年 | 25篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 27篇 |
2003年 | 17篇 |
2002年 | 23篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1991年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1930年 | 2篇 |
1928年 | 1篇 |
排序方式: 共有396条查询结果,搜索用时 0 毫秒
391.
To estimate the extent of the third carpal bone (C3) visible for evaluation in the dorsoproximal-dorsodistal oblique projection of the distal row of carpal bones, 13 forelimbs collected at post mortem from 7 horses were examined radiographically. The limbs were frozen with the carpal joints flexed then radiographed using fixed beam-cassette angles of 15 degrees to 45 degrees, at 5 degree intervals. The influence of beam-cassette angle on; the depth of the proximal articular surface examined, the radiographic appearance of C3 and the assessment of subchondral sclerosis was evaluated. Beam-cassette angles of 25 degrees to 40 degrees produced subjectively acceptable radiographs and did not appear to influence assessments of sclerosis. The mean depth of the examined proximal articular surface of the C3 increased significantly with each 5 degree increase in beam-cassette angle up to 40 degrees. The use of beam-cassette angles >35 degrees is recommended for the DPr-DDiO projection. 相似文献
392.
Proesmans Willem Bonte Dries Smagghe Guy Meeus Ivan Decocq Guillaume Spicher Fabien Kolb Annette Lemke Isgard Diekmann Martin Bruun Hans Henrik Wulf Monika Van Den Berge Sanne Verheyen Kris 《Landscape Ecology》2019,34(3):487-501
Landscape Ecology - Small forest fragments are often the most abundant type of semi-natural habitat in intensive agricultural landscapes. Wild pollinators can use these forest patches as nesting or... 相似文献
393.
Biodegradation of [ring-14C] mecoprop (2-(4-chloro-2-methylphenoxy)propionic acid) was determined in surface and sub-surface soil at concentrations of 0·0005, 0·05, 0·5, 5, 50, 500, 5000 and 25000 mg kg-1. The kinetics of mineralisation were evaluated from the mineralisation rates as a function of time and by non-linear regression analysis. In the sub-surface soil, degradation was 6–8 times slower than in surface soil, but the shape of the curves was the same in both layers. At concentrations between 0·0005 and 0·5 mg kg-1, in both surface and sub-surface soil, degradation was initially zero-order followed by first-order kinetics. At 5 to 500 mg kg-1 in surface soil and 5 to 50 mg kg-1 in sub-surface soil the degradation rate was initially either constant or decreasing followed by exponential degradation indicating increasing populations of mecoprop decomposers in the soil. At 5000 and 25000 mg kg-1 in the surface soil and at 500, 5000 and 25000 mg kg-1 in the sub-surface soil, the degradation was negligible, as determined by the percentage [14C] carbon dioxide evolved. By non-linear regression, the three-half order model was found to describe the mineralisation. © 1998 SCI 相似文献
394.
We studied the effects of habitat fragmentation, measured as forest stand size and isolation, on the distribution of Eurasian red squirrels (Sciurus vulgaris). Squirrel density was surveyed during four years in 46 forest stands (0.1–500 ha) in a forest landscape in south-central Sweden. The only factor that significantly influenced a density index was the proportion of spruce within a habitat fragment. Neither fragment size nor degree of isolation were significant. Furthermore, none of the interactions with year were significant, suggesting the same pattern in all four years. Thus, the effect of habitat fragmentation in this study seems to be only pure habitat loss, i.e. halving the proportion of preferred habitat in the landscape should result in a halving of the red squirrel population. Therefore, the landscape can be viewed as functionally continuous for the squirrels, although the preferred habitat was divided into fragments. The most likely explanation for the difference between this study and other studies on squirrels that found effects due to habitat fragmentation is a combination of shorter distances and less hostile surroundings in our study area. To identify landscape effects requires multiple studies because single studies usually consider only one landscape. 相似文献
395.
396.
Henrik Hesselmann 《Forstwissenschaftliches Centralblatt》1930,52(7-8):223-229
Ohne Zusammenfassung 相似文献