全文获取类型
收费全文 | 271篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
教育与普及 | 3篇 |
理论与方法论 | 2篇 |
现状及发展 | 72篇 |
研究方法 | 25篇 |
综合类 | 159篇 |
自然研究 | 12篇 |
出版年
2021年 | 1篇 |
2013年 | 3篇 |
2012年 | 24篇 |
2011年 | 20篇 |
2010年 | 4篇 |
2009年 | 1篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1983年 | 6篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1971年 | 6篇 |
1970年 | 8篇 |
1969年 | 10篇 |
1968年 | 3篇 |
1967年 | 14篇 |
1966年 | 4篇 |
1965年 | 1篇 |
1964年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 15 毫秒
191.
Kazantsev A Walker HA Slepko N Bear JE Preisinger E Steffan JS Zhu YZ Gertler FB Housman DE Marsh JL Thompson LM 《Nature genetics》2002,30(4):367-376
Huntington disease is caused by the expansion of a polyglutamine repeat in the Huntingtin protein (Htt) that leads to degeneration of neurons in the central nervous system and the appearance of visible aggregates within neurons. We have developed and tested suppressor polypeptides that bind mutant Htt and interfere with the process of aggregation in cell culture. In a Drosophila model, the most potent suppressor inhibits both adult lethality and photoreceptor neuron degeneration. The appearance of aggregates in photoreceptor neurons correlates strongly with the occurrence of pathology, and expression of suppressor polypeptides delays and limits the appearance of aggregates and protects photoreceptor neurons. These results suggest that targeting the protein interactions leading to aggregate formation may be beneficial for the design and development of therapeutic agents for Huntington disease. 相似文献
192.
Atom-molecule coherence in a Bose-Einstein condensate 总被引:2,自引:0,他引:2
Recent advances in the precise control of ultracold atomic systems have led to the realisation of Bose Einstein condensates (BECs) and degenerate Fermi gases. An important challenge is to extend this level of control to more complicated molecular systems. One route for producing ultracold molecules is to form them from the atoms in a BEC. For example, a two-photon stimulated Raman transition in a (87)Rb BEC has been used to produce (87)Rb(2) molecules in a single rotational-vibrational state, and ultracold molecules have also been formed through photoassociation of a sodium BEC. Although the coherence properties of such systems have not hitherto been probed, the prospect of creating a superposition of atomic and molecular condensates has initiated much theoretical work. Here we make use of a time-varying magnetic field near a Feshbach resonance to produce coherent coupling between atoms and molecules in a (85)Rb BEC. A mixture of atomic and molecular states is created and probed by sudden changes in the magnetic field, which lead to oscillations in the number of atoms that remain in the condensate. The oscillation frequency, measured over a large range of magnetic fields, is in excellent agreement with the theoretical molecular binding energy, indicating that we have created a quantum superposition of atoms and diatomic molecules two chemically different species. 相似文献
193.
194.
Lagged effects of ocean climate change on fulmar population dynamics 总被引:15,自引:0,他引:15
Environmental variation reflected by the North Atlantic Oscillation affects breeding and survival in terrestrial vertebrates, and climate change is predicted to have an impact on population dynamics by influencing food quality or availability. The North Atlantic Oscillation also affects the abundance of marine fish and zooplankton, but it is unclear whether this filters up trophic levels to long-lived marine top predators. Here we show by analysis of data from a 50-year study of the fulmar that two different indices of ocean climate variation may have lagged effects on population dynamics in this procellariiform seabird. Annual variability in breeding performance is influenced by the North Atlantic Oscillation, whereas cohort differences in recruitment are related to temperature changes in the summer growing season in the year of birth. Because fulmars exhibit delayed reproduction, there is a 5-year lag in the population's response to these effects of environmental change. These data show how interactions between different climatic factors result in complex dynamics, and that the effects of climate change may take many years to become apparent in long-lived marine top predators. 相似文献
195.
196.
Sister chromatid exchange as an indicator of mutagenesis 总被引:14,自引:0,他引:14
197.
Interleukin-1 receptor antagonist activity of a human interleukin-1 inhibitor 总被引:113,自引:0,他引:113
C H Hannum C J Wilcox W P Arend F G Joslin D J Dripps P L Heimdal L G Armes A Sommer S P Eisenberg R C Thompson 《Nature》1990,343(6256):336-340
Three interleukin-1 inhibitors have been purified to homogeneity from medium conditioned by human monocytes. Partial sequence analysis and digestion with N-glycanase indicate that these are glycosylation forms of a single protein. The protein binds to the interleukin-1 receptor but has no interleukin-1-like activity, even at very high concentrations, and is therefore a pure receptor antagonist. 相似文献
198.
199.
G E Thompson 《Nature》1967,215(5102):748-749
200.