全文获取类型
收费全文 | 2146篇 |
免费 | 130篇 |
国内免费 | 1篇 |
专业分类
林业 | 135篇 |
农学 | 74篇 |
基础科学 | 12篇 |
315篇 | |
综合类 | 345篇 |
农作物 | 70篇 |
水产渔业 | 227篇 |
畜牧兽医 | 893篇 |
园艺 | 70篇 |
植物保护 | 136篇 |
出版年
2023年 | 17篇 |
2022年 | 10篇 |
2021年 | 41篇 |
2020年 | 57篇 |
2019年 | 58篇 |
2018年 | 64篇 |
2017年 | 56篇 |
2016年 | 43篇 |
2015年 | 45篇 |
2014年 | 63篇 |
2013年 | 83篇 |
2012年 | 121篇 |
2011年 | 161篇 |
2010年 | 80篇 |
2009年 | 75篇 |
2008年 | 126篇 |
2007年 | 124篇 |
2006年 | 117篇 |
2005年 | 113篇 |
2004年 | 122篇 |
2003年 | 121篇 |
2002年 | 91篇 |
2001年 | 33篇 |
2000年 | 27篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 20篇 |
1996年 | 11篇 |
1995年 | 21篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1984年 | 18篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1975年 | 11篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1971年 | 8篇 |
1970年 | 11篇 |
1969年 | 7篇 |
排序方式: 共有2277条查询结果,搜索用时 203 毫秒
991.
Kricket A. Konrade Alison B. Clode Tammy M. Michau Simon C. Roe Brian J. Trumpatori William V. Krug Brian C. Gilger 《Veterinary ophthalmology》2009,12(2):119-124
A grossly displaced segmental zygomatic arch fracture with marked ventro-lateral deviation of the left globe was diagnosed in a 3-month-old male German Shepherd dog following a bite injury. The fracture was approached via a modified lateral orbitotomy and a fragment of the lacrimal bone removed. The rostral portion of the fracture was stabilized with a 5-hole 2.0 dynamic compression plate bone plate. The surgical correction achieved sufficient skeletal fixation for proper anatomical reduction of the globe and excellent cosmetic and functional outcomes. 相似文献
992.
Jason Elliott Horgan DVM ; Brian Keith Roberts DVM DACVECC Thomas Schermerhorn VMD DACVIM 《Journal of Veterinary Emergency and Critical Care》2009,19(3):254-261
Objective – To describe the patient population, disease severity, and outcome in dogs with immune-mediated hemolytic anemia (IMHA) that underwent splenectomy. To compare presurgical and postsurgical data.
Design – Retrospective case series.
Setting – Emergency clinic/referral hospital.
Animals – Ten dogs diagnosed with IMHA.
Interventions – Splenectomy in addition to standard medical management for IMHA.
Measurements – Medical records of 10 dogs with IMHA, in which a splenectomy was performed were reviewed. The population was analyzed with regards to physical and clinicopathologic data, severity, treatment, and outcome. Outcome was defined as survival at 30 days, percentage of dogs on medications at 30 days, and number of relapses documented by 30 days. The presurgical and postsurgical PCV and transfusion requirements were documented and compared for each dog.
Results – Nine of 10 dogs survived to 30 days. Four of the 9 that survived were not on any immunosuppressive medications. There were no relapses during the 30 days. The 3-day postsplenectomy PCVs were significantly higher than presplenectomy. The number of transfusions administered postsplenectomy was significantly less than those administered presplenectomy.
Conclusion – The use of splenectomy may be associated with an improved outcome in dogs with IMHA. 相似文献
Design – Retrospective case series.
Setting – Emergency clinic/referral hospital.
Animals – Ten dogs diagnosed with IMHA.
Interventions – Splenectomy in addition to standard medical management for IMHA.
Measurements – Medical records of 10 dogs with IMHA, in which a splenectomy was performed were reviewed. The population was analyzed with regards to physical and clinicopathologic data, severity, treatment, and outcome. Outcome was defined as survival at 30 days, percentage of dogs on medications at 30 days, and number of relapses documented by 30 days. The presurgical and postsurgical PCV and transfusion requirements were documented and compared for each dog.
Results – Nine of 10 dogs survived to 30 days. Four of the 9 that survived were not on any immunosuppressive medications. There were no relapses during the 30 days. The 3-day postsplenectomy PCVs were significantly higher than presplenectomy. The number of transfusions administered postsplenectomy was significantly less than those administered presplenectomy.
Conclusion – The use of splenectomy may be associated with an improved outcome in dogs with IMHA. 相似文献
993.
James S. Hughes Fenton Khan Stephanie A. Liss Ryan A. Harnish Gary E. Johnson Brian B. Bellgraph Katherine R. Znotinas 《Fisheries Management and Ecology》2021,28(3):241-252
Downstream passage for juvenile Chinook salmon Oncorhynchus tshawytscha (Walbaum) and steelhead Oncorhynchus mykiss (Walbaum) through the fish weir at Foster Dam, Oregon, was evaluated to assess the weir's efficacy as a long-term passage solution. Radio telemetry was used to estimate survival, passage and effectiveness for the fish weir, spillway and turbines. Survival of Chinook salmon through the fish weir varied by season and reservoir elevation (66%–87%), and passage proportions were low (8%–20%). Fish weir effectiveness was low to moderate (0.39–2.09). Steelhead survival was lower (57%–77%) but passed the fish weir in higher proportions (77%), and weir effectiveness was consistently high (2.96–5.49). The results indicate the existing fish weir will not be a suitable long-term passage solution for all species. However, because of the high passage proportions and effectiveness observed for steelhead, further development of the surface-flow concept appears to be promising for safely passing downstream-migrating fishes. 相似文献
994.
995.
996.
van der Heide T Govers LL de Fouw J Olff H van der Geest M van Katwijk MM Piersma T van de Koppel J Silliman BR Smolders AJ van Gils JA 《Science (New York, N.Y.)》2012,336(6087):1432-1434
Seagrasses evolved from terrestrial plants into marine foundation species around 100 million years ago. Their ecological success, however, remains a mystery because natural organic matter accumulation within the beds should result in toxic sediment sulfide levels. Using a meta-analysis, a field study, and a laboratory experiment, we reveal how an ancient three-stage symbiosis between seagrass, lucinid bivalves, and their sulfide-oxidizing gill bacteria reduces sulfide stress for seagrasses. We found that the bivalve-sulfide-oxidizer symbiosis reduced sulfide levels and enhanced seagrass production as measured in biomass. In turn, the bivalves and their endosymbionts profit from organic matter accumulation and radial oxygen release from the seagrass roots. These findings elucidate the long-term success of seagrasses in warm waters and offer new prospects for seagrass ecosystem conservation. 相似文献
997.
Meiotic recombination in budding yeast requires two RecA-related proteins, Rad51 and Dmc1, both of which form filaments on DNA capable of directing homology search and catalyzing formation of homologous joint molecules (JMs) and strand exchange. With use of a separation-of-function mutant form of Rad51 that retains filament-forming but not JM-forming activity, we show that the JM activity of Rad51 is fully dispensable for meiotic recombination. The corresponding mutation in Dmc1 causes a profound recombination defect, demonstrating Dmc1's JM activity alone is responsible for meiotic recombination. We further provide biochemical evidence that Rad51 acts with Mei5-Sae3 as a Dmc1 accessory factor. Thus, Rad51 is a multifunctional protein that catalyzes recombination directly in mitosis and indirectly, via Dmc1, during meiosis. 相似文献
998.
Z. L. Frogbrook J. Bell R. I. Bradley C. Evans R. M. Lark B. Reynolds P. Smith & W. Towers 《Soil Use and Management》2009,25(3):320-332
Intensive field surveys were undertaken in two upland catchments in the UK, Plynlimon in mid-Wales and Glensaugh in North East Scotland. The survey was to examine the spatial variation across the area and to assess the accuracy of the database underpinning the soil carbon map for the UK. In each area three 1-km2 squares were sampled on a 200-m grid, with samples taken from both the organic and mineral horizons. Carbon stock was estimated, from the sample data, for each 1-km2 square and compared with values from the UK database for that square. The results showed large differences between some squares, particularly for Plynlimon. In this area, the overall discrepancy between field and database values was 45%, compared with 8% for Glensaugh. Various sources of uncertainty were examined, including bulk density, organic horizon depth, and the proportion of different soil types within a square. The value for bulk density, assumed to determine carbon stock, had a significant effect on the estimates. In both catchments the organic layer showed a gradual decrease in bulk density with depth, resulting in a large proportion of the carbon being stored in the top part of the profile. The soil types, mapped during the survey, also showed large differences from those previously identified for each 1-km2 square. This would have a considerable effect on the estimates of carbon stock within the UK database. It highlights that caution needs to be used when interpreting the UK soil map at this spatial scale. 相似文献
999.
Anthea L. Mitchell Richard M. Lucas Brian E. Donnelly Kirrilly Pfitzner Anthony K. Milne Max Finlayson 《水产资源保护:海洋与淡水生态系统》2007,17(5):446-467
- 1. Using colour aerial photography, a set of fine (~1 m) spatial resolution orthomosaics and accompanying Digital Elevation Models (DEMs) were generated for the majority of mangroves in Kakadu National Park, Northern Australia, from which their extent and canopy height have been mapped.
- 2. The orthomosaics and DEMs, which were based on 68 stereo pairs acquired in 1991, cover an area of approximately 742 km2 and a coastal distance of 86 km. The DEMs have a height resolution of approximately ± 1 m.
- 3. The entire mosaic represents a key historical baseline data set of the extent and height of mangroves within the Park against which to observe and quantify changes in response to, for example, sea‐level rise.
- 4. The data sets will be available to assist management of the coastal environment and also to provide a unique insight into the distribution, dynamics and condition of mangroves. The techniques used are applicable to mangroves and other forested wetlands in other regions of Australia and elsewhere.
1000.
Wendy K. Michaud J. Brian Dempson James D. Reist Michael Power 《Ecology of Freshwater Fish》2013,22(4):520-529
Temporal diet changes can be detected by comparing δ13C and δ15N values between tissues with different isotopic turnover times. However, other factors contribute to disparities in δ13C and δ15N signatures between tissues and could confound the interpretation of stable isotope data. We examined the effects of ecological factors on differences in muscle and liver δ13C and δ15N signatures of Arctic charr [Salvelinus alpinus, (L.)] to determine whether their effects were large enough to influence studies of diet change. In addition, we examined whether differences in lipid content accounted for a significant portion of the differences in δ13C values between tissues. Results indicated that life history, diet, reproductive status and gender had significant effects on the differences in δ13C values between tissues, while gender and diet significantly affected differences in δ15N values. Differences in % lipid content between tissues also explained approximately 74% of the observed variation in the difference in δ13C values between tissues. The differences in δ13C values observed between muscle and liver tissues may be partially explained by physiological differences in lipid storage and use between tissues associated with ecological factor effects. These results demonstrate that ecological factors other than a change in diet can influence the differences in δ13C and δ15N signatures between muscle and liver tissues. However, the impact of ecological factors on studies of diet change depends on how the magnitude of the factor effects compared with a biologically meaningful change in diet. 相似文献