全文获取类型
收费全文 | 18240篇 |
免费 | 130篇 |
国内免费 | 2篇 |
专业分类
林业 | 3762篇 |
农学 | 1323篇 |
基础科学 | 152篇 |
3071篇 | |
综合类 | 1027篇 |
农作物 | 2148篇 |
水产渔业 | 1920篇 |
畜牧兽医 | 1827篇 |
园艺 | 1157篇 |
植物保护 | 1985篇 |
出版年
2024年 | 3篇 |
2023年 | 17篇 |
2022年 | 27篇 |
2021年 | 54篇 |
2020年 | 56篇 |
2019年 | 78篇 |
2018年 | 2787篇 |
2017年 | 2749篇 |
2016年 | 1232篇 |
2015年 | 111篇 |
2014年 | 77篇 |
2013年 | 89篇 |
2012年 | 932篇 |
2011年 | 2291篇 |
2010年 | 2180篇 |
2009年 | 1305篇 |
2008年 | 1447篇 |
2007年 | 1681篇 |
2006年 | 171篇 |
2005年 | 213篇 |
2004年 | 202篇 |
2003年 | 263篇 |
2002年 | 148篇 |
2001年 | 15篇 |
2000年 | 58篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 12篇 |
1996年 | 4篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1968年 | 4篇 |
1957年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
1.
2.
Mark D. Rawling Nicola Pontefract Ana Rodiles Ilektra Anagnostara Eric Leclercq Marion Schiavone Mathieu Castex Daniel L. Merrifield 《Journal of the World Aquaculture Society》2019,50(6):1108-1122
Fish were fed a single‐strain yeast fraction (SsYF; 2 g/kg) or a multistrain yeast fraction (MsYF; 0.8 g/kg) for 10 weeks. The results demonstrated significant (p ≤ 0.03) elevations in weight gain, specific growth rate, protein efficiency ratio, and feed conversion ratio in fish fed the yeast fraction‐supplemented diets. In the distal intestine, a significant elevation in microvilli density was observed after 5 and 10 weeks of dietary supplementation with MsYF and SsYF, respectively, compared to control fed fish (p < 0.001). A significant elevation (p = 0.02) in the perimeter ratio was observed in fish fed diets supplemented with the yeast fractions. After 10 weeks of feeding on the experimental diets, Rt‐qPCR demonstrated a significant downregulation (p < 0.05) in the stress response genes, heat‐shock protein 70 (hsp70) and proliferating cell nuclear antigen (pcna), in fish fed diets supplemented with the yeast fractions. Significant (p < 0.05) elevations in interleukin 1‐beta (il1β) and interleukin‐10 (il10) gene expression were observed in fish fed diets supplemented with the MsYF compared to the other dietary groups. These findings suggest that feeding an MsYF specifically at a lower incorporation rate < 1 g/kg, compared to a commercial SsYF at 2 g/kg, is effective in improving the intestinal health status and growth performance of European seabass. 相似文献
3.
4.
Rural depopulation and recent landscape changes in a Mediterranean region: Consequences to the breeding avifauna 总被引:8,自引:0,他引:8
We studied the vegetational and avifaunistic changes following rural depopulation in an area covering 2,600 ha north of Montpellier
(Southern France). The study area is covered by a mosaic of Mediterranean habitats that includes cultivation, grasslands,
shrublands, and woodlands and is representative of the natural features present and of the human usage practiced so far in
this part of the Mediterranean.
We sampled the vegetation and the bird fauna in the same 193 census plots in 1978 and in 1992. At both the habitat and landscape
scales the cover of woody plants increased significantly. Open habitats tend to disappear. As a consequence the abundance
of open-habitat bird species decreased significantly whereas the abundance of forest birds increased significantly. These
changes favor a pool of forest species widespread in western Europe and reduce habitat availability for open habitat and shrubland
species. Many of the latter are Mediterranean species whose distribution in Western Europe could become reduced under current
landscape dynamics. Our observation of more woodlands and their typical birds and of less open habitats and their associated
avifauna is not consistent with the traditional worry shown by the public and the managers about the regression of forests
and woodlands in the Northern Mediterranean as a consequence of fire. 相似文献
5.
6.
A. Schots J. De Boer A. Schouten J. Roosien J. F. Zil Verentant H. Pomp L. Bouwman-Smits H. Overmars F. J. Gommers B. Visser W. J. Stiekema J. Bakker 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(2):183-191
Engineering resistance against various diseases and pests is hampered by the lack of suitable genes. To overcome this problem we started a research program aimed at obtaining resistance by transfecting plants with genes encoding monoclonal antibodies against pathogen specific proteins. The idea is that monoclonal antibodies will inhibit the biological activity of molecules that are essential for the pathogenesis. Potato cyst nematodes are chosen as a model and it is thought that monoclonal antibodies are able to block the function of the saliva proteins of this parasite. These proteins are, among others, responsible for the induction of multinucleate transfer cells upon which the nematode feeds. It is well documented that the ability of antibodies to bind molecules is sufficient to inactivate the function of an antigen and in view of the potential of animals to synthesize antibodies to almost any molecular structure, this strategy should be feasible for a wide range of diseases and pests.Antibodies have several desirable features with regard to protein engineering. The antibody (IgG) is a Y-shaped molecule, in which the domains forming the tips of the arms bind to antigen and those forming the stem are responsible for triggering effector functions (Fc fragments) that eliminate the antigen from the animal. Domains carrying the antigen-binding loops (Fv and Fab fragments) can be used separately from the Fc fragments without loss of affinity. The antigen-binding domains can also be endowed with new properties by fusing them to toxins or enzymes. Antibody engineering is also facilitated by the Polymerase Chain Reaction (PCR). A systematic comparison of the nucleotide sequence of more than 100 antibodies revealed that not only the 3′-ends, but also the 5′-ends of the antibody genes are relatively conserved. We were able to design a small set of primers with restriction sites for forced cloning, which allowed the amplification of genes encoding antibodies specific for the saliva proteins ofGlobodera rostochiensis. Complete heavy and light chain genes as well as single chain Fv fragments (scFv), in which the variable parts of the light (VL) and heavy chain (VH) are linked by a peptide, will be transferred to potato plants. A major challenge will be to establish a correct expression of the antibody genes with regard to three dimensional folding, assembly and intracellular location. 相似文献
7.
Nicolas Rose Alain Abhervé-Guéguen Gérald Le Diguerher Eric Eveno Jean-Pierre Jolly Philippe Blanchard Aurélie Oger André Jestin François Madec 《Livestock Production Science》2005,95(3):177-186
The aim of this study was to determine the potential risk factors for PMWS at the individual pig level and assess the effect of the Pietrain paternal genetic background of the animals in a cohort study. The survey was set up in four PMWS-affected farms with 2 repetitions (batches) per farm. A representative sample of 60 pigs per batch, stratified according to the paternal genetic background (Pietrain: yes vs. no), was randomly selected after farrowing. The representative cohort was divided into 8 batches and the pigs were individually monitored from birth to slaughter. Survival analysis was used to determine the factors related to the time to PMWS. The litter-cluster effect was taken into account using the marginal Cox model (robust estimation of the covariance matrix) and the gamma shared frailty model which were compared.No protective effect of the Pietrain breed on the time to PMWS and the proportion of affected pigs in the offspring was found in this study. Piglets showing low circovirus type 2 (PCV2) titres at 7 weeks-old with no subsequent seroconversion and piglets from PCV2 negative sows were most likely to be affected by PMWS (HR=7.0 and 2.8, respectively). Active infection of the pregnant dams with parvovirus was related to an increased risk of PMWS in the offspring (HR=2.3). Neck injuries due to poorly performed injections in the dams were associated with an increased risk of PMWS with the marginal model (HR=2.1). Oxytocin injection (dams) during farrowing was protective against PMWS in the offspring (HR=0.6). 相似文献
8.
9.
Shohei MATSUURA Shigeru HOSHINO Hideaki HAYASHI Tetsuyuki KOHGUCHI Kyoji HAGIWARA Toshihiro OMURA 《Journal of General Plant Pathology》2002,68(1):99-102
DAS-ELISA proved to be reliable enough to detect a latent infection by Tomato spotted wilt virus (TSWV) in asymptomatic stock plants of chrysanthemum. A high density of Frankliniella occidentalis, the predominant vector, in the presence of latently infected stock plants resulted in a high incidence of disease in the chrysanthemum
production field. The incidence of disease was low when the vector thrips were not abundant in spite of the presence of latently
infected stock plants. These results suggest that an infestation of the vector thrips causes severe secondary spread of TSWV
originating from latently infected stock plants in chrysanthemum production fields.
Received 27 July 2001/ Accepted in revised form 27 November 2001 相似文献
10.