全文获取类型
收费全文 | 510篇 |
免费 | 28篇 |
专业分类
林业 | 100篇 |
农学 | 13篇 |
基础科学 | 2篇 |
76篇 | |
综合类 | 92篇 |
农作物 | 18篇 |
水产渔业 | 33篇 |
畜牧兽医 | 175篇 |
园艺 | 8篇 |
植物保护 | 21篇 |
出版年
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 11篇 |
2013年 | 12篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 25篇 |
2007年 | 18篇 |
2006年 | 18篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1993年 | 6篇 |
1988年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1973年 | 5篇 |
1972年 | 16篇 |
1970年 | 5篇 |
1969年 | 7篇 |
1967年 | 6篇 |
1966年 | 12篇 |
1965年 | 6篇 |
1964年 | 7篇 |
1963年 | 5篇 |
1962年 | 5篇 |
1957年 | 7篇 |
1955年 | 6篇 |
排序方式: 共有538条查询结果,搜索用时 15 毫秒
31.
Hannes Mayer 《European Journal of Forest Research》1969,88(1):378-379
Ohne Zusammenfassung 相似文献
32.
v. Pechmann L. Fabricius Zwölfer E. Rohmeder Mägdefrau W. Issel H. Mayer und Ronde 《Forstwissenschaftliches Centralblatt》1955,74(7-8):249-256
Ohne Zusammenfassung 相似文献
33.
von Pechmann Attenberger E. Rohmeder Backmund und H. Mayer 《Forstwissenschaftliches Centralblatt》1955,74(5-6):186-192
Ohne Zusammenfassung 相似文献
34.
Thomas?HolstEmail author Helmut?Mayer Dirk?Schindler 《European Journal of Forest Research》2004,123(1):13-28
Within the framework of an interdisciplinary project on the effects of climate and forest management on beech-dominated deciduous forests (Swabian Jura, south-western Germany), forest meteorological investigations are carried out to analyse the influences of exposure and canopy density on the microclimate within various beech stands (Fagus sylvatica L.). This second paper of the series Microclimate within beech stands focuses on the thermal conditions that exist mainly in the near-surface layer at different test plots. They were analysed by air temperature, Ta, (at 1.5 m a.g.l) and soil temperature, Ts, at six depths measured continuously in the period 1999–2003. The main results can be summarized as follows. (1) The thermal situation within the beech stands described by Ta depended primarily on the turbulent air-mass exchange conditions which were based on the slope-specific energy balance of the forest floor and advective heat fluxes. (2) The thermal situation within the soil described by Ts at 3 and 20 cm depth was governed by the molecular heat transport. Therefore, the heating and cooling rates of Ts were always lower than for Ta. Higher Ta and Ts values for the test plots on the SW slope showed that the thermal conditions within the beech stands depended primarily on the exposure. (3) Based on slope-specific differences of daily extremes of Ta and Ts at 3 cm depth between the silviculturally treated and control plots, the influence of the more pronounced height growth of the understorey vegetation under the near-surface thermal conditions could be clearly verified for the NE slope.Abbreviations PAR Photosynthetically active radiation - PAI Plant area index - LAI Leaf area index 相似文献
35.
Huber Bernhart M. postner Rudolf Mayer H. Mayer und Ernst 《Forstwissenschaftliches Centralblatt》1959,78(3-4):122-128
Ohne Zusammenfassung 相似文献
36.
Mägdefrau Attenberger E. Rohmeder H. Mayer Rohmeder und Rössler 《Forstwissenschaftliches Centralblatt》1954,73(5-6):185-192
Ohne Zusammenfassung 相似文献
37.
38.
39.
K. Sjstrand G. Wess I. Ljungvall J. Hggstrm A‐C. Merveille M. Wiberg V. Gouni J. Lundgren Willesen S. Hans A‐S. Lequarr L. Mejer Srensen J. Wolf L. Tiret M. Kierczak S. Forsberg K. McEntee G. Battaille E. Seppl K. Lindblad‐Toh M. Georges Hannes Lohi V. Chetboul M. Fredholm K. Hglund 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2014,28(2):451-457
Background
Measurement of plasma concentration of natriuretic peptides (NPs) is suggested to be of value in diagnosis of cardiac disease in dogs, but many factors other than cardiac status may influence their concentrations. Dog breed potentially is 1 such factor.Objective
To investigate breed variation in plasma concentrations of pro‐atrial natriuretic peptide 31‐67 (proANP 31‐67) and N‐terminal B‐type natriuretic peptide (NT‐proBNP) in healthy dogs.Animals
535 healthy, privately owned dogs of 9 breeds were examined at 5 centers as part of the European Union (EU) LUPA project.Methods
Absence of cardiovascular disease or other clinically relevant organ‐related or systemic disease was ensured by thorough clinical investigation. Plasma concentrations of proANP 31‐67 and NT‐proBNP were measured by commercially available ELISA assays.Results
Overall significant breed differences were found in proANP 31‐67 (P < .0001) and NT‐proBNP (P < .0001) concentrations. Pair‐wise comparisons between breeds differed in approximately 50% of comparisons for proANP 31‐67 as well as NT‐proBNP concentrations, both when including all centers and within each center. Interquartile range was large for many breeds, especially for NT‐proBNP. Among included breeds, Labrador Retrievers and Newfoundlands had highest median NT‐proBNP concentrations with concentrations 3 times as high as those of Dachshunds. German Shepherds and Cavalier King Charles Spaniels had the highest median proANP 31‐67 concentrations, twice the median concentration in Doberman Pinschers.Conclusions and Clinical Importance
Considerable interbreed variation in plasma NP concentrations was found in healthy dogs. Intrabreed variation was large in several breeds, especially for NT‐proBNP. Additional studies are needed to establish breed‐specific reference ranges. 相似文献40.
Three-spined stickleback Gasterosteus aculeatus, males were implanted with Silastic capsules filled with different aromatase
inhibitors; 1,4,6-androstatriene-3,17-dione or the non-steroidal CGS16949 A, 4-(5,6,7,8-tetrahydrimidazol [1,5-a]pyridin-5-yl)
benzonitrile monohydrochloride or empty capsules. The fish were then exposed to long or short photoperiod. Under the long
photoperiod most fish in all treatments displayed a hypertrophied kidney (a secondary sexual character in sticklebacks) and
completed, quiescent spermatogenesis, similar as in the natural spawning period. Under the short photoperiod the controls
had unstimulated kidneys and an active spermatogenesis, whereas the males implanted with both aromatase inhibitors had stimulated
kidneys, though not to the extent as in the long photoperiod, and completed, quiescent spermatogenesis. These findings suggest
that aromatization is of importance for the inhibitory effects of short photoperiod on reproduction in the stickleback.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献