全文获取类型
收费全文 | 364篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
林业 | 36篇 |
农学 | 3篇 |
基础科学 | 4篇 |
45篇 | |
综合类 | 88篇 |
农作物 | 16篇 |
水产渔业 | 39篇 |
畜牧兽医 | 129篇 |
园艺 | 16篇 |
植物保护 | 23篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 14篇 |
2020年 | 16篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 19篇 |
2016年 | 10篇 |
2015年 | 4篇 |
2014年 | 19篇 |
2013年 | 15篇 |
2012年 | 31篇 |
2011年 | 38篇 |
2010年 | 22篇 |
2009年 | 18篇 |
2008年 | 25篇 |
2007年 | 30篇 |
2006年 | 21篇 |
2005年 | 21篇 |
2004年 | 24篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有399条查询结果,搜索用时 734 毫秒
351.
352.
Tracking shifts in Atlantic mackerel (Scomber scombrus) larval habitat suitability on the Northeast U.S. Continental Shelf
下载免费PDF全文
![点击此处可从《Fisheries Oceanography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. Conor McManus Jonathan A. Hare David E. Richardson Jeremy S. Collie 《Fisheries Oceanography》2018,27(1):49-62
Climate change has altered the oceanographic environment and subsequently the habitats of marine species. Fish and invertebrate populations’ responses to habitat include movement with latitude and depth to remain within their fundamental niches. The northwest Atlantic mackerel (Scomber scombrus) population has fluctuated over the last century due in part to changes in the environment. We used species distribution models to understand the influence of the physical (temperature) and biological (zooplankton) environment on mackerel larval abundance, and how such relations have determined larval habitat suitability in the Northeast U.S. Shelf. Atlantic mackerel larval presence and abundance correlated with sea temperature and copepod abundances, suggesting that larval survival may be sensitive to specific temperatures and zooplankton prey. Predicted abundances were spatially interpolated to estimate Atlantic mackerel larval suitable habitat. Metrics for habitat quality indicate that the Mid‐Atlantic Bight has become less suitable over time. Since the 1970s, the proportion of Northeast U.S. Shelf suitable habitat located in the Mid‐Atlantic Bight has decreased, as southern New England and the western Gulf of Maine regions have become more suitable. Habitat suitability within the Northeast U.S. Shelf has shifted northeast: from the Mid‐Atlantic Bight‐southern New England border towards the northeast portion of southern New England. While total Northeast U.S. Shelf habitat suitability has decreased since the 1970s, the decline in the time series trend was not statistically significant. Thus, while select ecoregions have decreased in habitat suitability, larval habitat does not appear to be the only contributor to decreases in the U.S. Atlantic mackerel contingent. 相似文献
353.
Beau J Mahid N Burda WN Harrington L Shaw LN Mutka T Kyle DE Barisic B van Olphen A Baker BJ 《Marine drugs》2012,10(4):762-774
Recent genomic studies have demonstrated that fungi can possess gene clusters encoding for the production of previously unobserved secondary metabolites. Activation of these attenuated or silenced genes to obtain either improved titers of known compounds or new ones altogether has been a subject of considerable interest. In our efforts to discover new chemotypes that are effective against infectious diseases, including malaria and methicillin-resistant Staphylococcus aureus (MRSA), we have isolated a strain of marine fungus, Leucostoma persoonii, that produces bioactive cytosporones. Epigenetic modifiers employed to activate secondary metabolite genes resulted in enhanced production of known cytosporones B (1, 360%), C (2, 580%) and E (3, 890%), as well as the production of the previously undescribed cytosporone R (4). Cytosporone E was the most bioactive, displaying an IC(90) of 13 μM toward Plasmodium falciparum, with A549 cytotoxicity IC(90) of 437 μM, representing a 90% inhibition therapeutic index (TI(90) = IC(90) A459/IC(90)P. falciparum) of 33. In addition, cytosporone E was active against MRSA with a minimal inhibitory concentration (MIC) of 72 μM and inhibition of MRSA biofilm at roughly half that value (minimum biofilm eradication counts, MBEC90, was found to be 39 μM). 相似文献
354.
Guoping Li Hongqiang Feng Jeremy N. McNeil Bing Liu Peiyu Chen Feng Qiu 《Crop Protection》2011,30(12):1573-1578
Transgenic Bt (Bacillus thuringiensis) cotton has been effectively used to control the cotton bollworm, Helicoverpa armigera (Hübner) in China. However, in recent years, following the wide commercialization of Bt cotton in northern China there have been frequent outbreaks of the non-target pest Apolygus lucorum (Meyer-Dür). To clarify how transgenic cotton contributes to these outbreaks, a four-year field investigation of population dynamics and laboratory life table studies were carried out from 2007 to 2010 to evaluate the impact of two transgenic cotton cultivars (SGK321 expressing Cry1Ac + CpTI and GK12 expressing Cry1Ac) and their corresponding parental non-transgenic lines (Shiyuan321 and Simian3) on A. lucorum. There were no significant differences in the population densities of A. lucorum found in Bt cotton and non-Bt cotton plots, whether one compared those that had received insecticide treatments or those that had not. However, population densities of A. lucorum were significantly lower in pesticide treated plots than in controls. Furthermore, there were no significant differences in the net reproductive rates, generation times or intrinsic rates of increase of A. lucorum when reared on either Bt or non-Bt cotton cultivars. These results suggest that Bt cotton has no direct positive or negative effects on the biology of A. lucorum, so the most logical explanation for the observed outbreaks is the decrease in pesticide applications following the commercial release of Bt cotton. 相似文献
355.
Gerstein MB Lu ZJ Van Nostrand EL Cheng C Arshinoff BI Liu T Yip KY Robilotto R Rechtsteiner A Ikegami K Alves P Chateigner A Perry M Morris M Auerbach RK Feng X Leng J Vielle A Niu W Rhrissorrakrai K Agarwal A Alexander RP Barber G Brdlik CM Brennan J Brouillet JJ Carr A Cheung MS Clawson H Contrino S Dannenberg LO Dernburg AF Desai A Dick L Dosé AC Du J Egelhofer T Ercan S Euskirchen G Ewing B Feingold EA Gassmann R Good PJ Green P Gullier F Gutwein M Guyer MS Habegger L Han T Henikoff JG 《Science (New York, N.Y.)》2010,330(6012):1775-1787
356.
357.
358.
359.
Patrick J Crowley Dr Clemens Lamberth Urs Müller Sebastian Wendeborn Kurt Nebel John Williams Olivia‐A Sageot Neil Carter Tanya Mathie Hans‐Joachim Kempf Jeremy Godwin Peter Schneiter Markus R Dobler 《Pest management science》2010,66(2):178-185
BACKGROUND: The excellent fungicidal activity of [1,2,4]triazolo[1,5‐a]pyrimidines suggested the search for further analogues with improved properties. RESULTS: A series of novel trisubstituted pyrido[2,3‐b]pyrazines has been designed and prepared as 6,6‐biheterocyclic analogues of related 5,6‐bicyclic [1,2,4]triazolo[1,5‐a]pyrimidines. Their fungicidal activity was evaluated against the plant pathogens Puccinia recondita Rob. ex Desm. f. sp. tritici (Eriks.) CO Johnston (wheat brown rust), Mycosphaerella graminicola (Fuckel) Schroter (Septoria tritici Rob., leaf spot of wheat) and Magnaporthe grisea (Hebert) Barr (Pyricularia oryzae Cav., rice blast). Structure–activity relationship studies revealed the advantage of a fluoro substituent in position 6 and of a secondary amine in position 8. CONCLUSION: 8‐Amino‐7‐aryl‐6‐halogen‐substituted pyrido[2,3‐b]pyrazines have been prepared as 6,6‐biheterocyclic analogues of similarly substituted triazolopyrimidine fungicides. A concise four‐step synthesis route has been worked out to prepare these novel compounds from commercially available starting materials. [(R)‐(1,2‐Dimethylpropyl)]‐[6‐fluoro‐7‐(2,4,6‐trifluorophenyl)pyrido[2,3‐b]pyrazin‐8‐yl]amine showed excellent activity against three economically important phytopathogens. Copyright © 2009 Society of Chemical Industry 相似文献
360.
The strobilurin fungicides 总被引:5,自引:0,他引:5
Bartlett DW Clough JM Godwin JR Hall AA Hamer M Parr-Dobrzanski B 《Pest management science》2002,58(7):649-662
Strobilurins are one of the most important classes of agricultural fungicide. Their invention was inspired by a group of fungicidally active natural products. The outstanding benefits they deliver are currently being utilised in a wide range of crops throughout the world. First launched in 1996, the strobilurins now include the world's biggest selling fungicide, azoxystrobin. By 2002 there will be six strobilurin active ingredients commercially available for agricultural use. This review describes in detail the properties of these active ingredients--their synthesis, biochemical mode of action, biokinetics, fungicidal activity, yield and quality benefits, resistance risk and human and environmental safety. It also describes the clear technical differences that exist between these active ingredients, particularly in the areas of fungicidal activity and biokinetics. 相似文献