全文获取类型
收费全文 | 257篇 |
免费 | 0篇 |
专业分类
系统科学 | 3篇 |
教育与普及 | 1篇 |
理论与方法论 | 1篇 |
现状及发展 | 42篇 |
研究方法 | 26篇 |
综合类 | 172篇 |
自然研究 | 12篇 |
出版年
2018年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 13篇 |
2011年 | 27篇 |
2010年 | 4篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 11篇 |
2005年 | 15篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 29篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 7篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1958年 | 3篇 |
排序方式: 共有257条查询结果,搜索用时 15 毫秒
41.
C. Nations R. G. Allen K. J. Farmer P. L. Toy R. S. Sohal 《Cellular and molecular life sciences : CMLS》1986,42(1):64-66
Summary Superoxide dismutase activity was slow throughout the cell cycle of surface cultures ofPhysarum polycephalum. This activity increased markedly when the organism was induced to spherulate. Glutathione (GSH) and hydrogen peroxide (H2O2) concentrations changed very little during the cell cycle. During spherulation GSH decreased; H2O2 and the cyanide-resistant respiration of plasmodial homogenates increased. 相似文献
42.
Non-random X chromosome expression in female mules and hinnies 总被引:3,自引:0,他引:3
43.
T Arendt Y Allen J Sinden M M Schugens R M Marchbanks P L Lantos J A Gray 《Nature》1988,332(6163):448-450
Alcohol-induced memory impairment in man has been attributed to deficiencies in subcortical noradrenergic and cholinergic systems, as well as to damage in midbrain structures. Korsakoff's psychosis, a disease in which alcohol poisoning causes apparently irreversible memory defects, is characterized by lesions in cholinergic and noradrenergic nuclei and by a decrease in the activity of choline acetyltransferase (ChAT) and the content of noradrenaline (NA) in forebrain areas such as cerebral cortex and hippocampus, innervated by these nuclei. Prolonged intake of ethanol in rodents similarly produces signs of noradrenergic and cholinergic deafferentation in the cortex and hippocampus, as well as persistent memory deficits. To test whether alcohol-induced memory impairments depend on cholinergic deafferentation, we transplanted cholinergic-rich fetal basal forebrain cell suspensions into the cortex and hippocampus of alcohol-treated rats. The substantial and persistent memory losses produced in our rats by ethanol intake were associated with an impairment of cholinergic function, and were reversed by cholinergic-rich transplants into cortex and hippocampus. 相似文献
44.
Phosphonopeptides, a new class of synthetic antibacterial agents 总被引:18,自引:0,他引:18
J G Allen F R Atherton M J Hall C H Hassall S W Holmes R W Lambert L J Nisbet P S Ringrose 《Nature》1978,272(5648):56-58
45.
J. J. Chart H. Sheppard M. J. Allen W. L. Bencze R. Gaunt 《Cellular and molecular life sciences : CMLS》1958,14(4):151-152
Zusammenfassung 2-Methyl-1,2-bis-(3-pyridyl)-1-propanon (Su 4885) hemmt beim Hund die Ausscheidung von 17-OH-Steroiden aus den Nebennieren und hemmtin vitro ähnlich wie Amphenon den ACTH-Effekt auf Ratten-, Meerschweinchen-und Hunde-Nebennieren.In situ bei der Ratte hat es jedoch keine Amphenon-Wirkung, von dem es sich auch sonst unterscheidet. 相似文献
46.
47.
Thermochemical structures beneath Africa and the Pacific Ocean 总被引:2,自引:0,他引:2
Large low-velocity seismic anomalies have been detected in the Earth's lower mantle beneath Africa and the Pacific Ocean that are not easily explained by temperature variations alone. The African anomaly has been interpreted to be a northwest-southeast-trending structure with a sharp-edged linear, ridge-like morphology. The Pacific anomaly, on the other hand, appears to be more rounded in shape. Mantle models with heterogeneous composition have related these structures to dense thermochemical piles or superplumes. It has not been shown, however, that such models can lead to thermochemical structures that satisfy the geometrical constraints, as inferred from seismological observations. Here we present numerical models of thermochemical convection in a three-dimensional spherical geometry using plate velocities inferred for the past 119 million years. We show that Earth's subduction history can lead to thermochemical structures similar in shape to the observed large, lower-mantle velocity anomalies. We find that subduction history tends to focus dense material into a ridge-like pile beneath Africa and a relatively more-rounded pile under the Pacific Ocean, consistent with seismic observations. 相似文献
48.
49.
50.