全文获取类型
收费全文 | 3678篇 |
免费 | 90篇 |
国内免费 | 1篇 |
专业分类
林业 | 2263篇 |
农学 | 23篇 |
基础科学 | 5篇 |
170篇 | |
综合类 | 13篇 |
农作物 | 176篇 |
水产渔业 | 54篇 |
畜牧兽医 | 840篇 |
园艺 | 40篇 |
植物保护 | 185篇 |
出版年
2014年 | 34篇 |
2013年 | 110篇 |
2012年 | 29篇 |
2010年 | 43篇 |
2009年 | 48篇 |
2008年 | 33篇 |
2006年 | 34篇 |
2005年 | 78篇 |
2004年 | 79篇 |
2003年 | 56篇 |
2002年 | 48篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1997年 | 48篇 |
1996年 | 75篇 |
1995年 | 52篇 |
1994年 | 54篇 |
1993年 | 64篇 |
1992年 | 70篇 |
1991年 | 51篇 |
1990年 | 41篇 |
1989年 | 37篇 |
1988年 | 43篇 |
1987年 | 38篇 |
1986年 | 48篇 |
1985年 | 32篇 |
1984年 | 48篇 |
1983年 | 51篇 |
1982年 | 60篇 |
1981年 | 106篇 |
1980年 | 52篇 |
1979年 | 81篇 |
1978年 | 43篇 |
1954年 | 36篇 |
1953年 | 61篇 |
1938年 | 58篇 |
1937年 | 47篇 |
1936年 | 49篇 |
1935年 | 49篇 |
1934年 | 48篇 |
1933年 | 53篇 |
1932年 | 48篇 |
1931年 | 38篇 |
1930年 | 37篇 |
1929年 | 31篇 |
1928年 | 33篇 |
1927年 | 44篇 |
1926年 | 75篇 |
1925年 | 57篇 |
1898年 | 34篇 |
排序方式: 共有3769条查询结果,搜索用时 187 毫秒
41.
Clinicopathological Phenotype of Autosomal Recessive Cholesterol Deficiency in Holstein Cattle 下载免费PDF全文
42.
M. Ryan Smith DVM DACVECC Virginie A. Wurlod MS Dr vet med DACVECC DECVECC Chin-Chi Liu MS MApStat PhD 《Journal of Veterinary Emergency and Critical Care》2023,33(6):648-655
Objective
To describe hemostatic derangements associated with canine anaphylaxis and to assess for association with syndrome severity.Design
Prospective observational study.Setting
University teaching hospital.Animals
Twenty-seven client-owned dogs, recruited from November 2018 to January 2022, diagnosed with anaphylaxis of varying severity were included. Study inclusion required presentation <6 hours after initiation of clinical signs, no medications or history of illness within the prior 2 weeks, lack of comorbidities expected to affect hemostasis, and lack of a disease state that could alternatively explain the clinical presentation.Interventions
Blood samples were collected within the first hour of presentation for CBC, serum biochemistry, prothrombin time (PT), activated partial thromboplastin time (aPTT), and viscoelastic coagulation testing for use with a cartridge-based point-of-care device.Measurements and main results
Clotting time and clot formation time were prolonged, alpha angle and maximum clot firmness were decreased, PT and aPTT were prolonged, and platelet counts were lower in severe cases compared to mild and moderate cases. There were no differences for any parameter between mild and moderate cases. The presence or absence of abdominal effusion was not associated with hemostatic status.Conclusions
Global hemostatic derangements consistent with hypocoagulability are a prominent feature of severe anaphylaxis in dogs and should be considered for routine evaluation. 相似文献43.
Dr. Keit T. Ingram 《Agricultural Water Management》1992,20(4):341-342
44.
即使是最有进取心的养猪生产者也会忽视水质对猪生产性能的影响。尽管水质检验表明猪场水质仍在可接受的范围内,但水管内积聚起的水藻、细 相似文献
45.
Dr Uwe Schindler Joerg Steidl Lothar Mueller 《Archives of Agronomy and Soil Science》2013,59(1):63-73
Abstract The influence of regional soil distribution and land use on discharge formation in the “Stettiner Haff” catchment (8,456 km2) was investigated. The model ABIMO was used to calculate mean discharge for a long period (1961 – 1990) in consideration of regional differences in hydrological site conditions and soil heterogeneity. The highest discharge was found on settlement areas (276 mm a?1), on devastated plots (319 mm a?1) and on the non-hydromorphic agriculturally used sandy soils (214 mm a?1). Due to their small size these sub-areas were found to influence regional discharge for a limited extent only. On loam and clay soils only about 100 mm a?1 of discharge was formed. However, this share proved to be most important for the height of regional discharge because of the high area proportion in the region. Mineral soils of comparable parent material produce lower discharge under hydromorphic conditions than under non-hydromorphic conditions. With increasing clay content of the soils these differences decreased. The agriculturally used areas were found to be most important for the region's water discharge. They accounted for 83% of the discharge, i.e. they originated 119 mm a?1 on average. At forest sites, the discharge height was about 52 mm a?1. Sites close to groundwater table (groundwater level <1 m) proved to act as depletive areas. 相似文献
46.
Impact of land‐use intensity on the relationships between vegetation indices,photosynthesis and biomass of intensively and extensively managed grassland fens 下载免费PDF全文
C. M. H. Metzger J. Heinichen T. Eickenscheidt M. Drösler 《Grass and Forage Science》2017,72(1):50-63
Vegetation indices are widely used as model inputs and for non‐destructive estimation of biomass and photosynthesis, but there have been few validation studies of the underlying relationships. To test their applicability on temperate fens and the impact of management intensity, we investigated the relationships between normalized difference vegetation index (NDVI), leaf area index (LAI), brown and green above‐ground biomass and photosynthesis potential (PP). Only the linear relationship between NDVI and PP was management independent (R2 = 0·53). LAI to PP was described by a site‐specific and negative logarithmic function (R2 = 0·07–0·68). The hyperbolic relationship of LAI versus NDVI showed a high residual standard error (s.e.) of 1·71–1·84 and differed between extensive and intensive meadows. Biomass and LAI correlated poorly (R2 = 0·30), with high species‐specific variability. Intensive meadows had a higher ratio of LAI to biomass than extensive grasslands. The fraction of green to total biomass versus NDVI showed considerable noise (s.e. = 0·13). These relationships were relatively weak compared with results from other ecosystems. A likely explanation could be the high amount of standing litter, which was unevenly distributed within the vegetation canopy depending on the season and on the timing of cutting events. Our results show there is high uncertainty in the application of the relationships on temperate fen meadows. For reliable estimations, management intensity needs to be taken into account and several direct measurements throughout the year are required for site‐specific correction of the relationships, especially under extensive management. Using NDVI instead of LAI could reduce uncertainty in photosynthesis models. 相似文献
47.
Bon Dr. Jul Rekler 《European Journal of Forest Research》1861,5(1):41-53
Ohne Zusammenfassung 相似文献
48.
49.
50.