全文获取类型
收费全文 | 2201篇 |
免费 | 109篇 |
国内免费 | 1篇 |
专业分类
林业 | 59篇 |
农学 | 52篇 |
基础科学 | 5篇 |
252篇 | |
综合类 | 487篇 |
农作物 | 56篇 |
水产渔业 | 101篇 |
畜牧兽医 | 1188篇 |
园艺 | 23篇 |
植物保护 | 88篇 |
出版年
2021年 | 23篇 |
2020年 | 27篇 |
2019年 | 32篇 |
2018年 | 27篇 |
2017年 | 24篇 |
2016年 | 21篇 |
2015年 | 28篇 |
2014年 | 35篇 |
2013年 | 80篇 |
2012年 | 59篇 |
2011年 | 97篇 |
2010年 | 43篇 |
2009年 | 42篇 |
2008年 | 77篇 |
2007年 | 61篇 |
2006年 | 78篇 |
2005年 | 63篇 |
2004年 | 75篇 |
2003年 | 64篇 |
2002年 | 50篇 |
2001年 | 48篇 |
2000年 | 64篇 |
1999年 | 48篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1994年 | 35篇 |
1993年 | 55篇 |
1992年 | 49篇 |
1991年 | 55篇 |
1990年 | 56篇 |
1989年 | 55篇 |
1988年 | 48篇 |
1987年 | 40篇 |
1986年 | 55篇 |
1985年 | 40篇 |
1984年 | 30篇 |
1983年 | 28篇 |
1982年 | 21篇 |
1981年 | 30篇 |
1979年 | 38篇 |
1978年 | 23篇 |
1977年 | 18篇 |
1975年 | 25篇 |
1974年 | 19篇 |
1973年 | 26篇 |
1972年 | 29篇 |
1971年 | 37篇 |
1970年 | 26篇 |
1969年 | 30篇 |
排序方式: 共有2311条查询结果,搜索用时 0 毫秒
151.
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
152.
153.
Anderson DL 《Science (New York, N.Y.)》1993,261(5118):170-176
Helium-3 in hotspot magmas has been used as unambiguous evidence for the existence of a primordial, undegassed reservoir deep in the Earth's mantle. However, a large amount of helium-3 is delivered to the Earth's surface by interplanetary dust particles (IDPs). Recycling of deep-sea sediments containing these particles to the mantle, and eventual incorporation in magma, can explain the high helium-3/helium-4 ratios of hotspot magmas. Basafts with high helium-3/helium-4 ratios may represent degassing of helium introduced by ancient (probably 1.5 to 2.0 billion years old) pelagic sediments rather than degassing of primordial lower mantle material brought to the surface in plumes. Influx of IDPs can also explain the neon and siderophile compositions of mantle samples. 相似文献
154.
Earthquakes and the rotation of the Earth 总被引:1,自引:0,他引:1
Anderson DL 《Science (New York, N.Y.)》1974,186(4158):49-50
A correlation exists between long-term variations in the length of the day, Chandler wobble amplitudes, and global seismic activity. These variations may be partially due to climatic changes and ultimately to explosive volcanic activity. 相似文献
155.
156.
Mitton-Fry RM Anderson EM Hughes TR Lundblad V Wuttke DS 《Science (New York, N.Y.)》2002,296(5565):145-147
The essential Cdc13 protein in the yeast Saccharomyces cerevisiae is a single-stranded telomeric DNA binding protein required for chromosome end protection and telomere replication. Here we report the solution structure of the Cdc13 DNA binding domain in complex with telomeric DNA. The structure reveals the use of a single OB (oligonucleotide/oligosaccharide binding) fold augmented by an unusually large loop for DNA recognition. This OB fold is structurally similar to OB folds found in the ciliated protozoan telomere end-binding protein, although no sequence similarity is apparent between them. The common usage of an OB fold for telomeric DNA interaction demonstrates conservation of end-protection mechanisms among eukaryotes. 相似文献
157.
Anderson HR 《Science (New York, N.Y.)》1963,139(3549):42-45
158.
159.
160.
Anderson OL 《Science (New York, N.Y.)》1981,213(4503):76-82
A major component of the Inter-Union Commission on Geodynamics Project, labeled "Internal Properties and Processes," included certain experimental and theoretical research in tectonophysics, seismology, geochemistry, petrology, volcanology, and planetology. This review focuses on a few research areas in which there have been surprises and reversals. In particular, attention is given to the attempts to quantify the thermal profile in the earth's interior and the material properties of the earth's interior. 相似文献