全文获取类型
收费全文 | 1765篇 |
免费 | 44篇 |
国内免费 | 2篇 |
专业分类
林业 | 45篇 |
农学 | 76篇 |
基础科学 | 2篇 |
125篇 | |
综合类 | 950篇 |
农作物 | 28篇 |
水产渔业 | 44篇 |
畜牧兽医 | 461篇 |
园艺 | 11篇 |
植物保护 | 69篇 |
出版年
2023年 | 9篇 |
2021年 | 17篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 64篇 |
2012年 | 48篇 |
2011年 | 56篇 |
2010年 | 34篇 |
2009年 | 26篇 |
2008年 | 52篇 |
2007年 | 48篇 |
2006年 | 68篇 |
2005年 | 59篇 |
2004年 | 45篇 |
2003年 | 55篇 |
2002年 | 61篇 |
2001年 | 66篇 |
2000年 | 60篇 |
1999年 | 38篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1993年 | 33篇 |
1992年 | 37篇 |
1991年 | 45篇 |
1990年 | 44篇 |
1989年 | 54篇 |
1988年 | 47篇 |
1987年 | 50篇 |
1986年 | 54篇 |
1985年 | 35篇 |
1984年 | 41篇 |
1983年 | 53篇 |
1982年 | 56篇 |
1981年 | 66篇 |
1980年 | 44篇 |
1979年 | 63篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1971年 | 11篇 |
1966年 | 5篇 |
排序方式: 共有1811条查询结果,搜索用时 203 毫秒
991.
B.S. Tennent-Brown W.E Pomroy M.P. Reichel P.L. Gray T.S. Marshall P.A. Moffat 《New Zealand veterinary journal》2013,61(5):149-150
dAim:To estimate the prevalence of Neospora infection in a sample of New Zealand beef cattle. dMethods: The prevalence of Neospora caninum infection in New Zealand beef cattle was estimated by collecting blood at slaughter from 499 beef cattle from 40 different farms at 2 slaughter plants in the North Island and 1 in the lower South Island. Sera were tested using an ELISA against Neospora tachyzoite antigen. dResults: The prevalence of seropositive cattle was 2.5% (n=120), 3.6% (n=166) and 2.3% (n=213) at the plants surveyed, the overall prevalence being 2.8%. The serologically positive cattle came from 9 farms, 3 of which had more than 1 positive animal. The highest prevalence recorded amongst animals from 1 farm was 4/13 (31%), in a group of young steers. dConclusion: Neosporosis appears to be present at a lower level in the New Zealand beef cattle population than in the New Zealand dairy cattle population. Nevertheless, from the high seroprevalence evident amongst young cattle on 1 farm, we suggest that Neospora may be a cause of infertility in beef cattle in this country. 相似文献
992.
993.
JS Munday S Marshall NA Thomson M Kiupel RW Heathcott A French 《New Zealand veterinary journal》2013,61(4):219-223
Abstract
CASE HISTORY AND CLINICAL FINDINGS
A 15-year-old neutered male domestic short-haired cat was presented due to multiple 0.5–2?cm-diameter crusting plaques in the left preauricular region, over the bridge of nose, and in the right periocular region. The plaques did not appear to cause discomfort. 相似文献994.
P.L. Carter R.B. Marshall B.V.Sc. Dip.Microbiol. R.D. Jolly B.V.Sc. Ph.D. 《New Zealand veterinary journal》2013,61(11):264-265
Abstract Extract This paper describes the isolation of a haemolytic variant of Actinobacillus equuli from a foal which died from acute septicaemia. Foal deaths due to non-haemolytic A. Equuli (also known as Shigella equirulus) in New Zealand have been described previously by Hutchinson (1956) and Bloomberg (1963). 相似文献
995.
Allyson D. Groth Steven R. Hollingsworth Ron Ofri Philip H. Kass Zoe Reed Christopher J. Murphy 《Veterinary ophthalmology》2013,16(5):319-323
Objective To compare the Welch Allyn SureSight? wavefront autorefractor with retinoscopy in normal dogs. Animals studied Fifty privately owned dogs (100 eyes) of 20 breeds, free of ocular disease. Mean ± SD age: 5.7 ± 3.25 years (range: 6 months–13 years). Procedures The refractive error was determined in each eye by two experienced retinoscopists using streak retinoscopy as well as by an autorefractor operated by two different examiners. Measurements were performed before and approximately 30–45 min after cycloplegia was induced by cyclopentolate 0.5% and tropicamide 0.5% ophthalmic solutions. Results Mean ± SD noncyclopleged retinoscopy net sphere was ?0.55 ± 1.14 (range: ?3.75 to 3.5) diopters (D). Mean cyclopleged retinoscopy net sphere was ?0.52 ± 1.18 (range: ?4.25 to 2) D. Mean ± SD noncyclopleged autorefractor spherical equivalent (SE) was ?0.42 ± 1.13 D (range: ?3.36 to 2.73) D. Mean cyclopleged autorefractor SE was 0.10 ± 1.47 (range: ?5.62 to 3.19) D. Noncyclopleged autorefraction results were not significantly different from streak retinoscopy (whether noncyclopleged or cyclopleged, P = 0.80 and P = 0.26, respectively). Cyclopleged autorefraction results were significantly different from noncyclopleged or cyclopleged streak retinoscopy (P < 0.0001 in both states). There was no significant difference between noncyclopleged and cyclopleged streak retinoscopy (P = 0.97). Conclusions Noncyclopleged autorefraction shows good agreement with streak retinoscopy in dogs and may be a useful clinical technique. Cycloplegia does not significantly affect streak retinoscopy results in dogs. 相似文献
996.
José M. García del Barrio Francisco Auñón David Sánchez de Ron Ricardo Alía 《New Forests》2013,44(4):559-576
The relationship between current and potential distribution in 34 main Spanish forest tree species (data from the Third Spanish Forest Inventory) was determined using a Maximum Entropy functional approximation with climatic data as predictive variables. A method for detecting regional species pools at two different scales: biogeoclimatic classes (CLATERES classification), and forest landscape types (WWF classification) has been proposed. Then, the Absence percentage for a species (i.e. the proportion of landscapes types or biogeoclimatic classes in which the species is included in the regional species pool but is actually not present) was determined. Results show higher figures of Potential Species Richness in the Pyrenees and the Cantabrian Range, while inland or coastal Mediterranean semiarid landscapes have lower figures. Using a classification based on biogeoclimatic variables (CLATERES) improves precision when estimating Absent Species Richness. Absence percentage is zero or close to zero for five species (Pinus uncinata, Quercus robur, Quercus ilex, Quercus humilis and Juniperus communis), while for other six species (Acer pseudoplatanus, Fraxinus angustifolia, Alnus glutinosa, Populus alba, Sorbus aucuparia and Pinus pinea) the figures are higher than 0.6, which means the species is absent in more than 60 % of the landscapes or biogeoclimatic classes that it could inhabit. The relationships between tree life traits and the absence of species from the ecosystems studied is slight but non-dominant species, species not subjected to forest management, or zonal species are less widely distributed that their climatic potentiality indicates. 相似文献
997.
Wireworms in Florida are primarily a pest in newly planted sugarcane, and growers usually apply a soil insecticide at planting to protect germinating seedpieces from wireworm damage. However, studies have suggested that this application in many cases may not be necessary. The objective of this research was to test a sequential sampling method to determine the need for soil insecticide at sugarcane planting. Testing was conducted on fields located on King Ranch near South Bay, Florida. Wireworm samples were taken in a transect across the length of each field. We used an economic injury level of nine or more wireworms per 25 samples. Sugarcane yield parameters for each whole field were obtained through standard commercial harvesting procedures. Using our sampling method, 38 fields were judged as not needing insecticide application. There was no significant difference in yield in these fields with versus those without insecticide application. 相似文献
998.
J. C. Stark S. L. Love B. A. King J. M. Marshall W. H. Bohl T. Salaiz 《American Journal of Potato Research》2013,90(3):207-216
The ability to minimize potato yield and quality losses due to drought can be greatly improved by understanding the relative responses of different cultivars to seasonal variations in water supply. To address this need, we initiated a 2 year field experiment to determine the responses of the six potato cultivars to different seasonal drought patterns, including 1) full season irrigation at 100 % ET, 2) irrigation at 100 % ET terminated during late bulking , 3) full season irrigation at 70 % ET , 4) irrigation at 70 % ET terminated during late bulking , and 5) a gradual reduction in irrigation from 100 % ET during tuber initiation through early bulking, to 70 % ET during mid-bulking, and 50 % ET through late bulking. GemStar Russet and Ranger Russet, two medium-late maturing cultivars, generally produced the highest yields across the range of drought treatments, but both were fairly sensitive to changes in drought severity. Alturas, a late maturing cultivar, produced relatively high yields with full irrigation, but exhibited the greatest sensitivity to increasing drought severity, particularly when severe late-season water deficits were imposed. Yields for the early maturing cultivar Russet Norkotah were relatively low overall, but it was the least sensitive to changes in drought severity, particularly when late season drought was imposed. Russet Burbank produced comparatively high total yields across the range of drought treatments, but U.S. No. 1 yields were substantially reduced by each seasonal drought pattern. However, it was less sensitive to changes in drought severity than GemStar Russet, Ranger Russet and Alturas. Total and U.S. No. 1 yields for Summit Russet were low for each drought treatment and it exhibited intermediate sensitivity to changes in drought severity. GemStar Russet had the highest water use efficiency based on U.S. No. 1 yield. 相似文献
999.
Background
One of the major challenges in evolutionary biology is identifying rare species and devising management plans to protect them while also sustaining their genetic diversity. However, in attempting a broad understanding of rarity, single-species studies provide limited insights because they do not reveal whether the factors that affect rare species differ from those that affect more common species. To illustrate this important concept and to arrive at a better understanding of the form of rarity characterizing the rare Gerbillus henleyi, we explored its population genetic structure alongside that of the locally common Gerbillus andersoni allenbyi. We trapped gerbils in several locations in Israel's western and inner Negev sand dunes. We then extracted DNA from ear samples, and amplified two mitochondrial sequences: the control region (CR) and the cytochrome oxidase 2 gene (CO2). 相似文献1000.
Angela E Gradish Cynthia D Scott‐Dupree Les Shipp C Ron Harris Gillian Ferguson 《Pest management science》2010,66(2):142-146
BACKGROUND: Bumble bees [Bombus impatiens (Cresson)] are widely used for supplemental pollination of greenhouse vegetables and are at risk of pesticide exposure while foraging. The objective of this study was to determine the lethal and sub‐lethal effects of four insecticides (imidacloprid, abamectin, metaflumizone and chlorantraniliprole) and three fungicides (myclobutanil, potassium bicarbonate and cyprodinil + fludioxonil) used or with potential for use in Ontario greenhouse vegetable production to B. impatiens. RESULTS: Imidacloprid, abamectin, and metaflumizone were harmful to worker bees following direct contact, while chlorantraniliprole and all fungicides tested were harmless. Worker bees fed imidacloprid‐contaminated pollen had shortened life spans and were unable to produce brood. Worker bees consumed less pollen contaminated with abamectin. Metaflumizone, chlorantraniliprole and all fungicides tested caused no sub‐lethal effects in bumble bee micro‐colonies. CONCLUSION: We conclude that the new reduced risk insecticides metaflumizone and chlorantraniliprole and the fungicides myclobutanil, potassium bicarbonate and cyprodinil + fludioxonil are safe for greenhouse use in the presence of bumble bees. This information can be used preserve greenhouse pollination programs while maintaining acceptable pest management. Copyright © 2009 Society of Chemical Industry 相似文献