全文获取类型
收费全文 | 1200篇 |
免费 | 131篇 |
国内免费 | 2篇 |
专业分类
林业 | 62篇 |
农学 | 24篇 |
基础科学 | 13篇 |
181篇 | |
综合类 | 142篇 |
农作物 | 70篇 |
水产渔业 | 70篇 |
畜牧兽医 | 690篇 |
园艺 | 27篇 |
植物保护 | 54篇 |
出版年
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 27篇 |
2020年 | 24篇 |
2019年 | 27篇 |
2018年 | 29篇 |
2017年 | 37篇 |
2016年 | 38篇 |
2015年 | 42篇 |
2014年 | 54篇 |
2013年 | 57篇 |
2012年 | 71篇 |
2011年 | 74篇 |
2010年 | 60篇 |
2009年 | 54篇 |
2008年 | 94篇 |
2007年 | 77篇 |
2006年 | 68篇 |
2005年 | 51篇 |
2004年 | 62篇 |
2003年 | 55篇 |
2002年 | 46篇 |
2001年 | 18篇 |
2000年 | 23篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 17篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1970年 | 8篇 |
1968年 | 3篇 |
1966年 | 3篇 |
1963年 | 4篇 |
排序方式: 共有1333条查询结果,搜索用时 15 毫秒
1.
Spatiotemporal patterns of mountain whitefish (Prosopium williamsoni) in response to a restoration of longitudinal connectivity
下载免费PDF全文
![点击此处可从《Ecology of Freshwater Fish》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Peter M. Kiffney Ben Cram Paul L. Faulds Karl Burton Michele Koehler Thomas P. Quinn 《Ecology of Freshwater Fish》2018,27(4):1037-1053
To examine the role of longitudinal connectivity on the spatial and temporal dynamics of mountain whitefish (Prosopium williamsoni), we quantified movement and population dynamics following installation of the Landsburg Dam fishway, Cedar River, WA, USA. Mountain whitefish is widely distributed, poorly studied and not the focus of restoration. Before the fishway, mountain whitefish were not observed above the dam. Here, we focus on snorkel counts collected at reach and mesohabitat (e.g. pools) scales over 11 summers on the 20‐km above‐dam segment following restoration. A camera within the ladder provided number, size and movement timing, thereby informing on behaviour and recolonisation. Segment‐scale abundance increased following fish passage reaching an asymptote in 7 years, and mountain whitefish were detected throughout the main stem in 10 years. Annual movement through the ladder increased over time and was positively correlated with instream abundance and discharge, but negatively correlated with water temperature. About 60% of fish movements occurred in spring and early summer, potentially for foraging opportunities. Reach‐scale abundance peaked between 7 and 10 km from the dam; deep, cool (~10.6 to 11.6°C) conditions characterised these reaches. At the mesohabitat scale, mountain whitefish detection increased with depth and velocity after accounting for distance from the dam. Our results show how restoring longitudinal connectivity allowed this nontarget species to colonise newly available habitat. Their response supports the critical roles of longitudinal connectivity and environmental conditions, that manifest at different spatial scales, in dictating how freshwater fish respond to habitat disturbance. 相似文献
2.
Tim J Evans 《Veterinary Clinics of North America: Equine Practice》2002,18(2):371-8, viii
Ergopeptine alkaloid exposure is common in pregnant mares. Many mares live in geographic areas where Neotyphodium coenophialum-infected tall fescue is the dominant grass in pastures and hay. A variety of grasses and cereal grains can be infected by Claviceps purpurea, and fungal sclerotia can contaminate forage and especially ground and pelleted feed. An understanding of the endocrine alterations associated with ergopeptine alkaloid exposure during pregnancy is necessary for the diagnosis of potential exposure to these compounds and for eective prophylaxis and therapy. 相似文献
3.
4.
Marie Engel David W. Hird Tim E. Carpenter Martin Wierup 《Preventive veterinary medicine》1995,24(4):245-252
A cohort of 53 swine seronegative to Aujeszky's disease virus (ADV) was monitored in a 1 year study of a chronically infected commercial Swedish weaner pig producing herd. Serum samples were acquired from all 134 adult swine and analyzed by enzyme-linked immmunosorbent assay (ELISA). Animals testing negative, along with introduced replacement gilts, were followed serologically every second month. Movements of animals were recorded for 319 days and exposure to seropositive animals was calculated for each seronegative pig in the cohort. The accumulated daily pig contact between the 53 ADV-non-infected swine and 43 infected swine was 35 660 days and the median number of days in contact for the non-infected swine with infected was 222. Despite the frequent contact with seropositive pigs, no seronegative animals seroconverted during the first 11 months of observation. Forty-six of 53 pigs seroconverted after a clinical outbreak during the twelfth month of observation. 相似文献
5.
Tim J Cutler 《Veterinary Clinics of North America: Equine Practice》2004,20(2):319-43, vi
This article reviews conditions that primarily affect the corneal epithelium as distinct from corneal stromal diseases. Corneal ulceration is discussed elsewhere in this issue. The other corneal conditions include a variety of more subtle epithelial disease,which might colloquially be termed epitheliopathies, as well as uninfected indolent superficial ulcerations, corneal neoplasia, and eosinophilic keratitis. The fungal plaque is an unusual and somewhat chronic form of epithelial infection. Although less common than corneal ulcers, this collection of lesions may present uniquely challenging obstacles to diagnosis and identification of a cure. Newer therapies and surgical strategies are discussed. 相似文献
6.
7.
Navid Adnani Emmanuel Vazquez-Rivera Srikar N. Adibhatla Gregory A. Ellis Doug R. Braun Tim S. Bugni 《Marine drugs》2015,13(10):6082-6098
With respect to bacterial natural products, a significant outcome of the genomic era was that the biosynthetic potential in many microorganisms surpassed the number of compounds isolated under standard laboratory growth conditions, particularly among certain members in the phylum Actinobacteria. Our group, as well as others, investigated interspecies interactions, via co-culture, as a technique to coax bacteria to produce novel natural products. While co-culture provides new opportunities, challenges exist and questions surrounding these methods remain unanswered. In marine bacteria, for example, how prevalent are interspecies interactions and how commonly do interactions result in novel natural products? In an attempt to begin to answer basic questions surrounding co-culture of marine microorganisms, we have tested both antibiotic activity-based and LC/MS-based methods to evaluate Micromonosporaceae secondary metabolite production in co-culture. Overall, our investigation of 65 Micromonosporaceae led to the identification of 12 Micromonosporaceae across three genera that produced unique metabolites in co-culture. Our results suggest that interspecies interactions were prevalent between marine Micromonosporaceae and marine mycolic acid-containing bacteria. Furthermore, our approach highlights a sensitive and rapid method for investigating interspecies interactions in search of novel antibiotics, secondary metabolites, and genes. 相似文献
8.
9.
10.