全文获取类型
收费全文 | 10493篇 |
免费 | 544篇 |
国内免费 | 13篇 |
专业分类
林业 | 657篇 |
农学 | 336篇 |
基础科学 | 76篇 |
1632篇 | |
综合类 | 1662篇 |
农作物 | 610篇 |
水产渔业 | 726篇 |
畜牧兽医 | 4335篇 |
园艺 | 249篇 |
植物保护 | 767篇 |
出版年
2023年 | 59篇 |
2022年 | 79篇 |
2021年 | 154篇 |
2020年 | 176篇 |
2019年 | 203篇 |
2018年 | 188篇 |
2017年 | 180篇 |
2016年 | 212篇 |
2015年 | 153篇 |
2014年 | 227篇 |
2013年 | 436篇 |
2012年 | 498篇 |
2011年 | 642篇 |
2010年 | 377篇 |
2009年 | 360篇 |
2008年 | 646篇 |
2007年 | 573篇 |
2006年 | 582篇 |
2005年 | 612篇 |
2004年 | 518篇 |
2003年 | 566篇 |
2002年 | 484篇 |
2001年 | 170篇 |
2000年 | 152篇 |
1999年 | 159篇 |
1998年 | 106篇 |
1997年 | 94篇 |
1996年 | 85篇 |
1995年 | 105篇 |
1994年 | 102篇 |
1993年 | 97篇 |
1992年 | 115篇 |
1991年 | 110篇 |
1990年 | 115篇 |
1989年 | 73篇 |
1988年 | 93篇 |
1987年 | 77篇 |
1986年 | 101篇 |
1985年 | 103篇 |
1984年 | 81篇 |
1983年 | 74篇 |
1982年 | 48篇 |
1980年 | 47篇 |
1979年 | 63篇 |
1978年 | 54篇 |
1977年 | 55篇 |
1976年 | 58篇 |
1975年 | 59篇 |
1974年 | 46篇 |
1973年 | 51篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Caecal intussusceptions and typhlocolitis in horses with severe Gastrodiscus aegyptiacus infestation
下载免费PDF全文
![点击此处可从《Equine Veterinary Education》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Z. Gratwick C. Donnellan P. C. Page A. Viljoen J. Williams C. H. Lyle 《Equine Veterinary Education》2018,30(5):247-254
The intestinal trematode Gastrodiscus aegyptiacus (G. aegyptiacus) has been recognised in equids around the world for many years, but its pathogenicity is yet to be confirmed. This report describes seven cases of severe G. aegyptiacus infestation, including six cases of caecal intussusception. 相似文献
52.
Perumalraja Kirthika Sungwoo Park Vijayakumar Jawalagatti John Hwa Lee 《Journal of veterinary science (Suw?n-si, Korea)》2022,23(3)
BackgroundProliferative enteritis caused by Lawsonia intracellularis undermines the economic stability of the swine industry worldwide. The development of cost-effective animal models to study the pathophysiology of the disease will help develop strategies to counter this bacterium.ObjectivesThis study focused on establishing a model of gastrointestinal (GI) infection of L. intracellularis in C57BL/6 mice to evaluate the disease progression and lesions of proliferative enteropathy (PE) in murine GI tissue.MethodsWe assessed the murine mucosal and cell-mediated immune responses generated in response to inoculation with L. intracellularis.ResultsThe mice developed characteristic lesions of the disease and shed L. intracellularis in the feces following oral inoculation with 5 × l07 bacteria. An increase in L. intracellularis 16s rRNA and groEL copies in the intestine of infected mice indicated intestinal dissemination of the bacteria. The C57BL/6 mice appeared capable of modulating humoral and cell-mediated immune responses to L. intracellularis infection. Notably, the expression of genes for the vitamin B12 receptor and for secreted and membrane-bound mucins were downregulated in L. intracellularis -infected mice. Furthermore, L. intracellularis colonization of the mouse intestine was confirmed by the immunohistochemistry and western blot analyses.ConclusionsThis is the first study demonstrating the contributions of bacterial chaperonin and host nutrient genes to PE using an immunocompetent mouse model. This mouse infection model may serve as a platform from which to study L. intracellularis infection and develop potential vaccination and therapeutic strategies to treat PE. 相似文献
53.
This paper reviews the breeding distribution and numerical status of selected species of seabirds at 23 oceanic island groups in the Southern Ocean (between latitudes 35 and 70°S), based on census data and population estimates which have become available through increased scientific endeavour in the region during the last 15 years or so. The paper focuses on the avifauna of the Prince Edward islands, in the southern Indian Ocean, and points to the importance of these islands as a breeding station and sanctuary for seabirds. Only one oceanic island group, the Crozets, contains more species of breeding seabirds than the Prince Edward islands. Substantial segements (about 10% and greater) of the world breeding populations of the king and macaroni penguins, and the wandering, grey-headed, yellow-nosed and sooty albatrosses are based at the Prince Edward group. We recommend that Prince Edward Island (sensu stricto) should be a wilderness area, and that development at Marion Island should be kept to an absolute minimum. 相似文献
54.
The grey squirrel is recognised as a pest species of economic importance but the justification of the view appears to be founded on local areas of severe damage. Despite evidence that damage may not be alleviated by squirrel population destruction, Warfarin poisoning was introduced as an alternative to trapping.The utilisation by wildlife of a poison hopper designed for grey squirrel control was investigated by automatic photography. Results confirmed that a number of species may feed from the grain presented via the hopper. However, the majority of the bait was removed during the hours of darkness when grey squirrels were not active. It is a conservative estimate that between 55 and 65% of the grain entered the environment via animals other than squirrels.In addition, the removalof bait by night visitors resulted in the accumulation of large quantities of bait at and around the entrance to the hopper tunnel. This increased accessibility to the potentially poisoned bait by animals other than squirrels.Until such time as evidence is produced to show these results as exceptional, it can only be concluded that fears expressed over the lack of specificity of this method of control are justified. 相似文献
55.
The Shad fisheries of the Chesapeake Bay in Maryland have been declining since an 1897 peak of 7860 × 103kg. No periods of stability have been recorded. Data are presented to trace the decline not only as a function of specific areas within the Northern Chesapeake Bay but also in terms of environmental problems and recruitment overfishing.The problem is related to improving the commercial fishing yield. An estimation of a maximum effort of 200,000 man-hours is suggested if a stable yield is to be approached. Methods for obtaining this goal include alternating of closed fishing areas, adoption of rest days, enforcement of fisheries regulations and reduction of the number of metres of gill net used per fisherman. 相似文献
56.
Acidophilic actinomycetes, growing between pH 3.5 and 6.5, were isolated from 17 natural soils and mine wastes. Most isolates were Streptomyces spp. and selected ones were compared with some established neutrophilic species by assessment of overall similarity. Acidophilic and neutrophilic strains clustered separately, differing in a number of cultural and physiological characters, in addition to pH requirements. The possible importance of acidophilic actinomycetes in soil is discussed. 相似文献
57.
A method tor direct visual or photomicrographic enumeration of soil propagules in soil-agar films and soil smears, stained with a mixture ofeuropium(III) ttienoyltrifluoroacetonate and the disodium salt of 4,41-bis(4-anilino-6-bis(2-hydroxyethyl)amino-S-triazin-2-ylamino)2,21-stilbene disulphonic acid, abbreviated to Eu(TTA)3 and fluorescent brightener (FB), respectively, is described.Soil-agar suspensions at 55–60°C were introduced into haemocytometer sample chambers of 100 μm and 20 μm depth which gave soil-agar film thicknesses of 25 μm and 12 μm, respectively, after air-drying. Soil smears air-dried on 1.25 cm2 and 1.0 cm2 areas of glass slide were 5.2–6.0 μm and 6.0–8.0 μm thick, respectively.The Eu(TTA)3 is best formulated in 50% (v/v) ethanol. The best concentrations of Eu(TTA)3 and FB for staining soil propagules were 2 mM and 25 μM. respectively. A staining period of 18 h for soil-agar films and 90–120 min for soil smears was found to be optimal. The optimum volumes of 50% ethanol for rinsing soil-agar films and soil smears were found to be 12.5 and 5.0 ml. respectively.Lack of in-depth focusing on agar films 25 μm thick resulted in 15–17 per cent error in enumerations. The 12 μm agar films and soil smears required little in-depth focusing and were acceptable for photomicrographic recording of numbers of soil propagules. It is concluded that incident u.v. photomicrographic recording of soil propagule numbers in thin agar films or soil smears is a practical solution to operator fatigue likely to occur during direct microscopy. 相似文献
58.
59.
60.