全文获取类型
收费全文 | 534篇 |
免费 | 25篇 |
专业分类
林业 | 59篇 |
农学 | 23篇 |
基础科学 | 2篇 |
85篇 | |
综合类 | 85篇 |
农作物 | 30篇 |
水产渔业 | 17篇 |
畜牧兽医 | 225篇 |
园艺 | 1篇 |
植物保护 | 32篇 |
出版年
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 19篇 |
2012年 | 22篇 |
2011年 | 27篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 20篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 20篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 16篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 15篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 8篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 8篇 |
1970年 | 9篇 |
1969年 | 8篇 |
1968年 | 9篇 |
1966年 | 6篇 |
1913年 | 3篇 |
排序方式: 共有559条查询结果,搜索用时 0 毫秒
51.
Keller LP Bajt S Baratta GA Borg J Bradley JP Brownlee DE Busemann H Brucato JR Burchell M Colangeli L d'Hendecourt L Djouadi Z Ferrini G Flynn G Franchi IA Fries M Grady MM Graham GA Grossemy F Kearsley A Matrajt G Nakamura-Messenger K Mennella V Nittler L Palumbo ME Stadermann FJ Tsou P Rotundi A Sandford SA Snead C Steele A Wooden D Zolensky M 《Science (New York, N.Y.)》2006,314(5806):1728-1731
Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust. 相似文献
52.
W. G. Sturny P. Weisskopf E. R. Keller F. Schwendimann 《Journal of Agronomy and Crop Science》1989,162(4):268-282
Impact of crop rotation, fertilizer treatments and herbicidal applications on the long term maintenance of soil fertility
V. Comparative studies regarding chemical and physical factors of the yield potential of a soil over a ten year experimental period
In order to examine the influence of different crop management practices such as crop rotation, fertilizer treatments and herbicide applications on the yield potential of a soil, the Crop Science Department of the Swiss Federal Institute of Technology (ETH Zurich) conducted a long term field experiment commencing 1973. The experimental location was at the Swiss Federal Research Station for Farm Management and Agricultural Engeneering at Tanikon/TG (northeastern Switzerland).
After the ten year period, chemical and physical soil properties were not found to be substantially affected by the various experimental treatments. Organic carbon and total nitrogen were more influenced by fertilizer treatments than by crop rotation and herbicide applications. Both cation exchange capacity and pH proved to be fairly stable values.
Aggregate stability and organic matter exhibited similar profiles, although soil bulk density was affected by crop rotation. The volume of large and medium sized pores was similarly affected in that the corn-dominated crop rotation resulted in a quantifiable impact upon soil compaction.
Depending upon weed control efficiency, the grain yields of the winter wheat test crop clearly exhibited the effects of crop rotation whereas the lowest yields resulted from the corn-dominated crop rotation. 相似文献
V. Comparative studies regarding chemical and physical factors of the yield potential of a soil over a ten year experimental period
In order to examine the influence of different crop management practices such as crop rotation, fertilizer treatments and herbicide applications on the yield potential of a soil, the Crop Science Department of the Swiss Federal Institute of Technology (ETH Zurich) conducted a long term field experiment commencing 1973. The experimental location was at the Swiss Federal Research Station for Farm Management and Agricultural Engeneering at Tanikon/TG (northeastern Switzerland).
After the ten year period, chemical and physical soil properties were not found to be substantially affected by the various experimental treatments. Organic carbon and total nitrogen were more influenced by fertilizer treatments than by crop rotation and herbicide applications. Both cation exchange capacity and pH proved to be fairly stable values.
Aggregate stability and organic matter exhibited similar profiles, although soil bulk density was affected by crop rotation. The volume of large and medium sized pores was similarly affected in that the corn-dominated crop rotation resulted in a quantifiable impact upon soil compaction.
Depending upon weed control efficiency, the grain yields of the winter wheat test crop clearly exhibited the effects of crop rotation whereas the lowest yields resulted from the corn-dominated crop rotation. 相似文献
53.
Tarsal radiographs of 134 trotters were made prior to training. Radiographs were evaluated for changes commonly associated with spavin. Spavin, if present, was graded as mild, moderate, or severe. Sone of the 134 horses were radiographed annually for one, two, or three years. Radiographs of the 134 horses were compared with radiographs of 141 additional horses in which spavin had been diagnosed clinically. Only 66 of the 134 trotters (50.4%) had normal tarsal radiographs at the time of initial examination; the other 65 had some radiographic evidence of spavin. The incidence and severity of radiographic changes identified in a group of horses in which spavin was diagnosed clinically. Thus, the present results suggest that tarsal radiography is of little value in establishing the diagnosis and prognosis of spavin in trotters. 相似文献
54.
55.
56.
57.
58.
Hans?Keller Rikus?Pomp Jaap?Bakker Arjen?SchotsEmail author 《European journal of plant pathology / European Foundation for Plant Pathology》2005,111(4):391-397
A phage library containing 2.7 × 109 randomly expressed peptides was used to determine the epitopes of three monoclonal antibodies that bind to the coat protein of potato virus Y. Construction of the consensus sequences for the peptides obtained after three selection rounds indicated that each antibody recognized a different epitope located within the first 50 N-terminal amino acids of the coat protein. The location of the epitopes was confirmed by heterologous expression of the N-terminal part of the coat protein in Escherichia coli, and, subsequently, by performing an immunological test with the three antibodies. The accuracy of the phage library was demonstrated by predicting in silico the cross-reactivity of the three antibodies with other potyvirus family members. ELISA and in silico predictions revealed the same results in almost every case. The potential of peptide phage libraries to optimize the use of antibodies in plant virology is discussed. 相似文献
59.
60.