全文获取类型
收费全文 | 763篇 |
免费 | 42篇 |
国内免费 | 1篇 |
专业分类
林业 | 27篇 |
农学 | 11篇 |
基础科学 | 13篇 |
87篇 | |
综合类 | 121篇 |
农作物 | 20篇 |
水产渔业 | 30篇 |
畜牧兽医 | 464篇 |
园艺 | 9篇 |
植物保护 | 24篇 |
出版年
2023年 | 6篇 |
2021年 | 11篇 |
2020年 | 18篇 |
2019年 | 17篇 |
2018年 | 11篇 |
2017年 | 21篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 29篇 |
2012年 | 27篇 |
2011年 | 28篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 30篇 |
2007年 | 26篇 |
2006年 | 27篇 |
2005年 | 25篇 |
2004年 | 27篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 22篇 |
2000年 | 18篇 |
1999年 | 22篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1972年 | 5篇 |
1970年 | 6篇 |
1966年 | 8篇 |
1941年 | 6篇 |
1940年 | 7篇 |
1927年 | 5篇 |
排序方式: 共有806条查询结果,搜索用时 46 毫秒
791.
Relation between the major histocompatibility (B) locus and autoimmune thyroiditis in obese chickens 总被引:5,自引:0,他引:5
Obese strain chickens develop circulating autoantibodies to thyroglobulin and lymphocytic infiltration of their thyroids during aging. Two alleles, B(1) and B(4), are found with high gene frequency at the major histocompatibility (B) locus. Greater pathology and higher antibody titers are observed in B(1)B(1) and B(1)B(4) birds than in their B(4)B(4) siblings. 相似文献
792.
Tilling RI Rubin M Sigurdsson H Carey S Duffield WA Rose WI 《Science (New York, N.Y.)》1984,224(4650):747-749
Geologic and radiometric-age data indicate that El Chichón was frequently and violently active during the Holocene, including eruptive episodes about 600, 1250, and 1700 years ago and several undated, older eruptions. These episodes, involving explosive eruptions of sulfur-rich magma and associated dome-growth processes, were apparently separated by intervals of approximately 350 to 650 years. Some of El Chichón's eruptions may correlate with unusual atmospheric phenomena around A.D. 1300 and possibly A.D. 623. 相似文献
793.
Individuals of two migratory races of white-crowned sparrows (Zonotrichia leucophrys) caged under an open sky showed a pronounced orientation in their night restlessness during normal periods of migration for the species. In August and September 1958 most birds showed a southerly orientation at night; daytime activity was random to somewhat northerly. In April and May 1959 most birds showed a strong northerly orientation at night; daytime activity was random to somewhat southerly (1). 相似文献
794.
795.
796.
797.
798.
M Bockrath DH Cobden PL McEuen NG Chopra A Zettl A Thess RE Smalley 《Science (New York, N.Y.)》1997,275(5308):1922-1925
The electrical properties of individual bundles, or "ropes," of single-walled carbon nanotubes have been measured. Below about 10 kelvin, the low-bias conductance was suppressed for voltages less than a few millivolts. In addition, dramatic peaks were observed in the conductance as a function of a gate voltage that modulated the number of electrons in the rope. These results are interpreted in terms of single-electron charging and resonant tunneling through the quantized energy levels of the nanotubes composing the rope. 相似文献
799.
Neonatal thymectomy increases the incidence of spontaneous and methylcholanthrene-enhanced thyroiditis in rats 总被引:7,自引:0,他引:7
At 16 weeks of age, 13 percent of untreated Buffalo strain rats showed evidence of autoimmune thyroiditis. Feeding methylcholanthrene increased the incidence to 42 percent. Neonatal thymectomy significantly raised the incidence of disease so that almost all (87 percent) untreated and all methylcholanthrene-treated animals developed severe disease. It is proposed that the thymus exerts a regulatory effect on autosensitization. 相似文献
800.
Ecological forecasts: an emerging imperative 总被引:1,自引:0,他引:1
Clark JS Carpenter SR Barber M Collins S Dobson A Foley JA Lodge DM Pascual M Pielke R Pizer W Pringle C Reid WV Rose KA Sala O Schlesinger WH Wall DH Wear D 《Science (New York, N.Y.)》2001,293(5530):657-660
Planning and decision-making can be improved by access to reliable forecasts of ecosystem state, ecosystem services, and natural capital. Availability of new data sets, together with progress in computation and statistics, will increase our ability to forecast ecosystem change. An agenda that would lead toward a capacity to produce, evaluate, and communicate forecasts of critical ecosystem services requires a process that engages scientists and decision-makers. Interdisciplinary linkages are necessary because of the climate and societal controls on ecosystems, the feedbacks involving social change, and the decision-making relevance of forecasts. 相似文献