全文获取类型
收费全文 | 439篇 |
免费 | 77篇 |
专业分类
林业 | 9篇 |
农学 | 3篇 |
19篇 | |
综合类 | 60篇 |
农作物 | 9篇 |
水产渔业 | 21篇 |
畜牧兽医 | 384篇 |
园艺 | 2篇 |
植物保护 | 9篇 |
出版年
2022年 | 4篇 |
2020年 | 12篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 17篇 |
2013年 | 21篇 |
2012年 | 30篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 19篇 |
2008年 | 22篇 |
2007年 | 17篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 13篇 |
2003年 | 18篇 |
2002年 | 11篇 |
2001年 | 5篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 9篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1972年 | 6篇 |
1967年 | 6篇 |
1966年 | 4篇 |
排序方式: 共有516条查询结果,搜索用时 31 毫秒
41.
Storey M Mahoney JJ Saunders AD Duncan RA Kelley SP Coffin MF 《Science (New York, N.Y.)》1995,267(5199):852-855
Widespread basalts and rhyolites were erupted in Madagascar during the Late Cretaceous. These are considered to be related to the Marion hot spot and the breakup of Madagascar and Greater India. Seventeen argon-40/argon-39 age determinations reveal that volcanic rocks and dikes from the 1500-kilometer-long rifted eastern margin of Madagascar were emplaced rapidly (mean age = 87.6 +/- 0.6 million years ago) and that the entire duration of Cretaceous volcanism on the island was no more than 6 million years. The evidence suggests that the thick lava pile at Volcan de l'Androy in the south of the island marks the focal point of the Marion hot spot at approximately 88 million years ago and that this mantle plume was instrumental in causing continental breakup. 相似文献
42.
Primary in vitro synthesis of antibody has been achieved with a mouse spleen-thymus organ culture system 54 hours after it was incubated for 18 hours with coliphage R17. 相似文献
43.
Head JW Campbell DB Elachi C Guest JE McKenzie DP Saunders RS Schaber GG Schubert G 《Science (New York, N.Y.)》1991,252(5003):276-288
Magellan images confirm that volcanism is widespread and has been fimdamentally important in the formation and evolution of the crust of Venus. High-resolution imaging data reveal evidence for intrusion (dike formation and cryptodomes) and extrusion (a wide range of lava flows). Also observed are thousands of small shield volcanoes, larger edifices up to several hundred kilometers in diameter, massive outpourings of lavas, and local pyroclastic deposits. Although most features are consistent with basaltic compositions, a number of large pancake-like domes are morphologically similar to rhyolite-dacite domes on Earth. Flows and sinuous channels with lengths of many hundreds of kilometers suggest that extremely high effusion rates or very fluid magmas (perhaps komatiites) may be present. Volcanism is evident in various tectonic settings (coronae, linear extensional and compressional zones, mountain belts, upland rises, highland plateaus, and tesserae). Volcanic resurfacing rates appear to be low (less than 2 Km(3)/yr) but the significance of dike formation and intrusions, and the mode of crustal formation and loss remain to be established. 相似文献
44.
Two-dimensional helium-3 (3He) provides a simple model for the experimental investigation of the emergence of quantum complexity in a strongly correlated Fermi system. We have observed two-dimensional, two-band heavy-fermion behavior in bilayer films of 3He atoms when adsorbed on the surface of graphite preplated by a solid bilayer of 4He. Thermodynamic measurements on this system showed that the relevant control parameter is the total density of the 3He film. The 3He bilayer system can be driven toward a quantum critical point at which the effective mass appears to diverge, interband coupling vanishes, and a local-moment state appears. It opens a new testing ground for theories of quantum criticality in heavy-fermion materials. 相似文献
45.
46.
47.
Diethylhydroxylamine (DEHA) reacts with gas-phase hydroxyl radicals on every third collision, whereas the corresponding reaction in aqueous solution is considerably slower. The high gas-phase reactivity explains the predicted inhibitory effect of DEHA in atmospheric smog processes. Results from the studies in the aqueous phase are helpful in predicting the mechanism of the reaction of DEHA with hydroxyl radicals. 相似文献
48.
Quintyne NJ Reing JE Hoffelder DR Gollin SM Saunders WS 《Science (New York, N.Y.)》2005,307(5706):127-129
Most tumor cells are characterized by increased genomic instability and chromosome segregational defects, often associated with hyperamplification of the centrosome and the formation of multipolar spindles. However, extra centrosomes do not always lead to multipolarity. Here, we describe a process of centrosomal clustering that prevented the formation of multipolar spindles in noncancer cells. Noncancer cells needed to overcome this clustering mechanism to allow multipolar spindles to form at a high frequency. The microtubule motor cytoplasmic dynein was a critical part of this coalescing machinery, and in some tumor cells overexpression of the spindle protein NuMA interfered with dynein localization, promoting multipolarity. 相似文献
49.
Long-term movement of up to 150 kilometers in 332 days by tagged, living Nautilus, and postmortem shell drift of 1000 kilometers in 138 days, corroborate and explain the cosmopolitan distribution of many fossil shelled cephalopods. 相似文献
50.
Genome maps 1991 [wall chart 总被引:1,自引:0,他引:1
M Chipperfield M Maidek P Pearson M Ashburner D M Glover R D Saunders I Duncan D Hartl J Merriam G Lee 《Science (New York, N.Y.)》1991,254(5029):247-262