全文获取类型
收费全文 | 117篇 |
免费 | 6篇 |
专业分类
林业 | 5篇 |
农学 | 5篇 |
基础科学 | 1篇 |
30篇 | |
综合类 | 19篇 |
农作物 | 34篇 |
水产渔业 | 8篇 |
畜牧兽医 | 13篇 |
园艺 | 2篇 |
植物保护 | 6篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 18篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 10篇 |
2013年 | 4篇 |
2012年 | 5篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 1篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1997年 | 1篇 |
排序方式: 共有123条查询结果,搜索用时 15 毫秒
111.
Actinomycetes from sediments in the Trondheim fjord, Norway: diversity and biological activity 总被引:1,自引:0,他引:1 下载免费PDF全文
The marine environment represents a largely untapped source for isolation of new microorganisms with potential to produce biologically active secondary metabolites. Among such microorganisms, Gram-positive actinomycete bacteria are of special interest, since they are known to produce chemically diverse compounds with a wide range of biological activities. We have set out to isolate and characterize actinomycete bacteria from the sediments in one of the largest Norwegian fjords, the Trondheim fjord, with respect to diversity and antibiotic-producing potential. Approximately 3,200 actinomycete bacteria were isolated using four different agar media from the sediment samples collected at different locations and depths (4.5 to 450 m). Grouping of the isolates first according to the morphology followed by characterization of isolates chosen as group representatives by molecular taxonomy revealed that Micromonospora was the dominating actinomycete genus isolated from the sediments. The deep water sediments contained a higher relative amount of Micromonospora compared to the shallow water samples. Nine percent of the isolates clearly required sea water for normal growth, suggesting that these strains represent obligate marine organisms. Extensive screening of the extracts from all collected isolates for antibacterial and antifungal activities revealed strong antibiotic-producing potential among them. The latter implies that actinomycetes from marine sediments in Norwegian fjords can be potential sources for the discovery of novel anti-infective agents. 相似文献
112.
Sigrid Hakv?g Espen Fj?rvik Geir Klinkenberg Sven Even F. Borgos Kjell D. Josefsen Trond E. Ellingsen Sergey B. Zotchev 《Marine drugs》2009,7(4):576-588
A new strain belonging to the genus Collimonas was isolated from the sea surface microlayer off the coast of Trøndelag, Norway. The bacterium, designated Collimonas CT, produced an antibacterial compound active against Micrococcus luteus. Subsequent studies using LC-MS identified this antibacterial compound as violacein, known to be produced by several marine-derived bacteria. Fragments of the violacein biosynthesis genes vioA and vioB were amplified by PCR from the Collimonas CT genome and sequenced. Phylogenetic analysis of these sequences demonstrated close relatedness of the Collimonas CT violacein biosynthetic gene cluster to those in Janthinobacterium lividum and Duganella sp., suggesting relatively recent horizontal gene transfer. Considering diverse biological activities of violacein, Collimonas CT shall be further studied as a potential producer of this compound. 相似文献
113.
On a large swine operation, necropsy revealed that 39 of 146 (27%) pigs during one week in April and 37 of 137 (27%) pigs during one week in June died from hemorrhage due to gastric ulceration. Contributory factors may have been feed withdrawal one day per week and feeding finely ground pellets. 相似文献
114.
林翠香 宋龙飞 Sergey Garkusha 宋丰顺 Zhanna Mukhina 滕斌 甘泉 Victor Kovalyov 余海兵 Lubov Yesaulova 倪大虎 《中国农学通报》2021,37(23):1-7
为获得具有优良直播特性的种质,以俄罗斯引进的10份水稻资源为材料,研究中胚轴长度、低温发芽能力和淹水条件下发芽率等与水稻直播相关的特性。结果表明:‘LIDER’、‘ATLANT’和‘OLIMP’低温条件下萌发速度最快,‘LIDER’、‘OLIMP’、‘ATLANT’、‘NATASHA’、‘ISTOK’和‘PARTNER’具有较好的低温发芽能力;‘ATLANT’、‘ISTOK’、‘RAPANZ’、‘GAMMA’、‘OLIMP’和‘SONET’的中胚轴长度与‘绿香粳28’在5%水平上达显著差异;在缺氧条件下,所有的品种间的发芽率均达极显著差异,但俄罗斯品种均优于对照。在所有引进的俄罗斯10品种中,‘ATLANT’与直播相关的综合性状最为突出,中胚轴长度、低温发芽能力和淹水条件下发芽率均极显著优于对照品种。 相似文献
115.
Piletska EV Burns R Terry LA Piletsky SA 《Journal of agricultural and food chemistry》2012,60(1):95-99
A molecularly imprinted polymer (MIP) for the purification of N(1),N(12)-bis(dihydrocaffeoyl)spermine (kukoamine A) was computationally designed and tested. The properties of the polymer were characterized. The protocol of the solid phase extraction (SPE) of kukoamine A from potato peels was optimized. A HPLC-MS method for the quantification of kukoamine A was developed and used for all optimization studies. The capacity of the MIP in relation to kukoamine A from the potato peels extract was estimated at 54 mg/g of the polymer. The kukoamine A purified from potato extract using MIP was exceptionally pure (≈ 90%). Although the corresponding blank polymer was less selective than the MIP for the extraction of kukoamine A from the potato extract, it was shown that the blank polymer could be effectively used for the purification of the crude synthetic kukoamine (polymer capacity = 80 mg of kukoamine A/g of the adsorbent, kukoamine A purity ≈ 86%). Therefore, selective adsorbents could be computationally designed for other plant products, allowing their purification in quantities that would be sufficient for more detailed studies and potential practical applications. 相似文献
116.
Villegas JE Savel'ev S Nori F Gonzalez EM Anguita JV García R Vicent JL 《Science (New York, N.Y.)》2003,302(5648):1188-1191
We fabricated a device that controls the motion of flux quanta in a niobium superconducting film grown on an array of nanoscale triangular pinning potentials. The controllable rectification of the vortex motion is due to the asymmetry of the fabricated magnetic pinning centers. The reversal in the direction of the vortex flow is explained by the interaction between the vortices trapped on the magnetic nanostructures and the interstitial vortices. The applied magnetic field and input current strength can tune both the polarity and magnitude of the rectified vortex flow. Our ratchet system is explained and modeled theoretically, taking the interactions between particles into consideration. 相似文献
117.
Sergey Hegay Mulatu Geleta Tomas Bryngelsson Abdybek Asanaliev Larisa Garkava-Gustavsson Helena Persson Hovmalm Rodomiro Ortiz 《Genetic Resources and Crop Evolution》2014,61(3):555-566
Common bean (Phaseolus vulgaris) is an important export crop in Kyrgyzstan since the end of the twentieth century. Genetic diversity analysis of common bean populations is useful for breeding programs, as it helps to select genetic material to be used for further crossing. Twenty-seven common bean accessions were analyzed using 13 qualitative morphological traits. In some cases, obtained morphological data were combined with previously published results based on microsatellite markers. The similarity matrices generated from the molecular and morphological data were significantly correlated (r = 0.49, P < 0.01). Cluster analyses based on Dice’s similarity coefficient were constructed based on morphological data and the combined data set of morphology and microsatellite, and both grouped the 27 accessions according to their origin: 15 belonged to the Andean and 12 to the Mesoamerican gene pool. On average, the Andean accessions were less diverse than the Mesoamerican accessions. The average diversity based on the Shannon diversity index for the 13 qualitative morphological traits was 0.05. Overall, this study revealed that qualitative morphological markers are efficient in assigning modern cultivars to their gene pools of origin. 相似文献
118.
Dulub O Batzilln M Solovev S Loginova E Alchagirov A Madey TE Diebold U 《Science (New York, N.Y.)》2007,317(5841):1052-1056
When low-energy electrons strike a titanium dioxide surface, they may cause the desorption of surface oxygen. Oxygen vacancies that result from irradiating a TiO2(011)-2x1 surface with electrons with an energy of 300 electron volts were analyzed by scanning tunneling microscopy. The cross section for desorbing oxygen from the pristine surface was found to be 9 (+/-6) x 10(-17) square centimeters, which means that the initial electronic excitation was converted into atomic motion with a probability near unity. Once an O vacancy had formed, the desorption cross sections for its nearest and next-nearest oxygen neighbors were reduced by factors of 100 and 10, respectively. This site-specific desorption probability resulted in one-dimensional arrays of oxygen vacancies. 相似文献
119.
Sergey A. Dyshlovoy 《Marine drugs》2021,19(10)
The natural compounds derived from marine organisms often exhibit unique chemical structures and potent biological activities. Cancer-preventive activity is one of the rather new activities that has emerged and been extensively studied over the last decades. This review summarizes the recent updates on the marine chemopreventive compounds covering the relevant literature published in 2013–2021 and following the previous comprehensive review by Stonik and Fedorov (Marine Drugs 2014, 12, 636–671). In the current article, only the molecules having an effect on malignant transformation (or related pathway and molecules), cancer stem cells, or carcinogen-induced in vivo tumor development were considered to be “true” cancer-preventive compounds and were, therefore, reviewed. Additionally, particular attention has been given to the molecular mechanisms of chemoprevention, executed by the reported marine compounds. 相似文献
120.
Jung Eun Seol Sang Woo Ahn Bomin Seol Hyeong Rok Yun Nammi Park Hyoung Kyu Kim Elena A. Vasileva Natalia P. Mishchenko Sergey A. Fedoreyev Valentin A. Stonik Jin Han 《Marine drugs》2021,19(10)
Echinochrome A (Ech A, 7-ethyl-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone) has been known to exhibit anti-oxidative and anti-inflammatory effects. However, no study has been carried out on the efficacy of Ech A against skin photoaging; this process is largely mediated by oxidative stress. Six-week-old male SKH-1 hairless mice (n = 36) were divided into five groups. Except for a group that were not treated (n = 4), all mice underwent ultraviolet-B (UVB) exposure for 8 weeks while applying phosphate-buffered saline or Ech A through intraperitoneal injection. UVB impaired skin barrier function, showing increased transepidermal water loss and decreased stratum corneum hydration. UVB induced dermal collagen degeneration and mast cell infiltration. Ech A injection was found to significantly lower transepidermal water loss while attenuating tissue inflammatory changes and collagen degeneration compared to the control. Furthermore, Ech A was found to decrease the relative expression of matrix metalloproteinase, tryptase, and chymase. Taken together, these results suggest that Ech A protects against UVB-induced photoaging in both functional and histologic aspects, causing a lowering of collagen degradation and inflammatory cell infiltration. 相似文献