全文获取类型
收费全文 | 979篇 |
免费 | 61篇 |
国内免费 | 14篇 |
专业分类
林业 | 120篇 |
农学 | 29篇 |
基础科学 | 6篇 |
110篇 | |
综合类 | 123篇 |
农作物 | 54篇 |
水产渔业 | 85篇 |
畜牧兽医 | 449篇 |
园艺 | 24篇 |
植物保护 | 54篇 |
出版年
2024年 | 2篇 |
2022年 | 16篇 |
2021年 | 30篇 |
2020年 | 15篇 |
2019年 | 14篇 |
2018年 | 28篇 |
2017年 | 30篇 |
2016年 | 31篇 |
2015年 | 33篇 |
2014年 | 40篇 |
2013年 | 64篇 |
2012年 | 68篇 |
2011年 | 78篇 |
2010年 | 38篇 |
2009年 | 45篇 |
2008年 | 47篇 |
2007年 | 53篇 |
2006年 | 74篇 |
2005年 | 66篇 |
2004年 | 55篇 |
2003年 | 45篇 |
2002年 | 51篇 |
2001年 | 17篇 |
2000年 | 18篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1054条查询结果,搜索用时 15 毫秒
71.
72.
Sergio Hernández-Verdugo Ramón G. Guevara-González Rafael F. Rivera-Bustamante Ken Oyama 《Euphytica》2001,122(1):31-36
Plants collected in thirteen wild populations of Capsicum annuum from Northwest Mexico were tested for resistance to the pepper huasteco begomovirus (formerly subgroup III) (PHV) that is
transmitted by the white fly Bemisia tabaci Genadius. Plants were inoculated using both grafting and biolistic methods. Presence of viral DNA was detected by dot blot
hybridization and densitometry. Populations varied in their resistance to PHV. Plants of only two of the populations either
did not develop disease symptoms or showed very light symptoms after inoculation. In some cases, symptoms appeared several
days after inoculation. In plants of these populations viral DNA was detected by dot-blot hybridization assays but they appear
to be a good source of resistance (symptomless) for use in breeding programmes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
73.
Variation in diosgenin levels among 10 accessions of fenugreek seeds produced in western Canada 总被引:1,自引:0,他引:1
Taylor WG Zulyniak HJ Richards KW Acharya SN Bittman S Elder JL 《Journal of agricultural and food chemistry》2002,50(21):5994-5997
A collection of 10 accessions of fenugreek (Trigonella foenum-graecum L.), an annual legume, was grown during two summers at three plot locations in western Canada to assess whether genetic (accession) and environmental factors (site and year of production) influenced levels of diosgenin, a steroidal sapogenin. The 60 harvested seed samples, each analyzed by single determinations on three subsamples of defatted and dried seed material, were hydrolyzed by a microscale procedure in water containing 2-propanol (70%) and sulfuric acid (1 M). The extracts were analyzed by capillary gas chromatography with 6-methyldiosgenin as internal standard. Diosgenin levels from mature seeds ranged from 0.28 to 0.92% (28-92 microg/10 mg). Analysis of variance on combined diosgenin levels from the three sites and two years revealed that accession, accession x year, and site x year effects were significant for diosgenin content, whereas site, year, and site x accession effects were not. Four accessions, CN 19062, CN 19067, CN 19070, and CN 19071, were identified with high levels of diosgenin on the basis of the 2-year data set. In these accessions, mean levels of diosgenin plus yamogenin from seven site years were estimated at 0.70, 0.98, 0.84, and 0.87%, respectively. 相似文献
74.
Assessment of Biogas use as an Energy Source from Anaerobic Digestion of Brewery Wastewater 总被引:1,自引:0,他引:1
Bahar Kasapgil Ince Orhan Ince G. Ken Anderson Semiha Arayici 《Water, air, and soil pollution》2001,126(3-4):239-251
Energy recovery from a crossflow ultrafiltration (UF) membraneunit employed in order to improve the performance of an anaerobic contact digester for the treatment of brewery wastewater was assessed. The performance of the pilot-scale anaerobic UF membrane system was studied for over 15 months. At steady-state conditions, an organic loading rate of 28.5 kg COD m-3 d-1, a hydraulic retention time of 4.2 days and overall COD and BOD removal efficiencies of 99% and almost 100% were achieved, respectively. Percent methane in biogas was found to be in a range of 67–79% with the corresponding methane yield of 0.28–0.35 m3 CH4 kg-1 CODremoved. The potential energy recovery from the system treating brewery wastewater at an OLR of 28.5 kg COD m-3 d-1 was 87 MJ d-1 which would enable to maintain all energy requirements of the feed pump, mixing and heating of the reactor contents. In addition to this, 71% of the energy requirement for recirculating the reactor content through the membranes would also be recovered. 相似文献
75.
Samuel Adjei-Nsiah Cees Leeuwis Ken E. Giller Thom W. Kuyper 《Agriculture and Human Values》2008,25(3):389-403
This study reports on action research efforts that were aimed at developing institutional arrangements beneficial for soil
fertility improvement. Three stages of action research are described and analyzed. We initially began by bringing stakeholders
together in a platform to engage in a collaborative design of new arrangements. However, this effort was stymied mainly because
conditions conducive for learning and negotiation were lacking. We then proceeded to support experimentation with alternative
arrangements initiated by individual landowners and migrant farmers. The implementation of these arrangements too ran into
difficulties due to intra-family dynamics and ambiguities regarding land tenure. Further investigations to find out how ambiguities
could be tackled revealed that the local actors themselves had taken initiatives towards developing institutional innovations
to reduce ambiguities. However, there is still considerable scope for further development of these self-organized innovations.
The article ends with a reflection on inter-disciplinary action research, where it is argued that making “mistakes” is an
inherent and necessary characteristic in action research that aims to address complex social issues.
相似文献
Samuel Adjei-NsiahEmail: |
76.
中国东方蜜蜂的形态学及生物地理学研究 总被引:13,自引:2,他引:13
用形态学研究方法对中国的东方蜜蜂(Apis cerana)的形态特征进行研究。东方蜜蜂的标本从中国大陆的34个样点采集而来,这些样点代表了东方蜜蜂在中国大陆不同气候带或地理区域分布的不同类型。 34个点共采集了220群蜜蜂的样,每群蜂测定分析15只工蜂,形态的测定特征参照Ruttner 1988年提出的测定标准进行。每只蜂总共有38个测定的形态特征。测定的性状特征的数据进行因素分析,集合分析和区辨分析;形态性状与生态环境因子相关性分析;并与周边国家东方蜜蜂的相关数据进行比较,发现:生活在吉林长白山温带阔叶林的东方蜜蜂个体较大、体色较黑,与日本、韩国的东方蜜蜂较为相似;来自亚热带常绿阔叶林的东方蜜蜂(甘肃天水、湖北和湖南)与云南北部、北京、尼泊尔的东方蜜蜂聚集为一类;而居住在南方热带季雨林如:福建、广东、广西和云南部分南方的东方蜜蜂与低海拔亚热带常绿阔叶林的东方蜜蜂(越南、中国四川和安徽黄山)聚集为另一类; 云南南方如:景洪、思茅、河口、镇康、元江、屏边、蒙自草坝和开远的东方蜜蜂形成独特的一个分枝,与泰国和缅甸的东方蜜蜂非常接近,同时与亚热带常绿阔叶林的东方蜜蜂相邻;值得关注的是,来自高寒湿地的东方蜜蜂(甘肃岷县)是目前在亚洲已经发现的东方蜜蜂中,其个体最大、颜色最深。在因素分析和集合分析里,它具有独特的位置。 相似文献
77.
78.
79.
Garber K 《Science (New York, N.Y.)》2002,295(5555):612-613
80.
The photolysis of methyl iodide on a porous glass surface has been studied by electron paramagnetic resonance. A large number of methyl radicals can be stabilized over a wide range of temperature. The surface of porous Vycor glass is an excellent host for trapping free radicals. 相似文献