全文获取类型
收费全文 | 347篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
丛书文集 | 54篇 |
现状及发展 | 78篇 |
研究方法 | 25篇 |
综合类 | 185篇 |
自然研究 | 6篇 |
出版年
2017年 | 3篇 |
2016年 | 3篇 |
2013年 | 3篇 |
2012年 | 17篇 |
2011年 | 24篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 9篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1967年 | 5篇 |
1966年 | 9篇 |
1965年 | 3篇 |
1960年 | 1篇 |
1959年 | 16篇 |
1958年 | 30篇 |
1957年 | 22篇 |
1956年 | 10篇 |
1955年 | 15篇 |
1954年 | 23篇 |
1948年 | 7篇 |
1947年 | 3篇 |
排序方式: 共有349条查询结果,搜索用时 108 毫秒
31.
The space environments--or magnetospheres--of magnetized planets emit copious quantities of energetic neutral atoms (ENAs) at energies between tens of electron volts to hundreds of kiloelectron volts (keV). These energetic atoms result from charge exchange between magnetically trapped energetic ions and cold neutral atoms, and they carry significant amounts of energy and mass from the magnetospheres. Imaging their distribution allows us to investigate the structure of planetary magnetospheres. Here we report the analysis of 50-80 keV ENA images of Jupiter's magnetosphere, where two distinct emission regions dominate: the upper atmosphere of Jupiter itself, and a torus of emission residing just outside the orbit of Jupiter's satellite Europa. The trans-Europa component shows that, unexpectedly, Europa generates a gas cloud comparable in gas content to that associated with the volcanic moon Io. The quantity of gas found indicates that Europa has a much greater impact than hitherto believed on the structure of, and the energy flow within, Jupiter's magnetosphere. 相似文献
32.
33.
34.
对藏药波棱瓜花药材的质量标准进行初步研究.根据2010年版《中国药典》附录IX相关方法,对波棱瓜花药材的水分、总灰分、酸不溶性灰分、醇溶性浸出物进行测定;并对该药材的性状、显微特征进行描述;采用薄层色谱(TLC)法进行定性鉴别.初步明确了波棱瓜花药材性状、显微和薄层鉴别方法,并确立了波棱瓜花药材水分、总灰分、酸不溶性灰分、浸出物的限量.本研究为波棱瓜花的质量标准的的制定提供参考依据. 相似文献
35.
S M Sisodiya S L Free K A Williamson T N Mitchell C Willis J M Stevens B E Kendall S D Shorvon I M Hanson A T Moore V van Heyningen 《Nature genetics》2001,28(3):214-216
PAX6 is widely expressed in the central nervous system. Heterozygous PAX6 mutations in human aniridia cause defects that would seem to be confined to the eye. Magnetic resonance imaging (MRI) and smell testing reveal the absence or hypoplasia of the anterior commissure and reduced olfaction in a large proportion of aniridia cases, which shows that PAX6 haploinsuffiency causes more widespread human neuro developmental anomalies. 相似文献
36.
37.
38.
39.
40.
T-cell epitope of the autoantigen myelin basic protein that induces encephalomyelitis 总被引:29,自引:0,他引:29
Chronic relapsing paralysis and demyelination within the central nervous system (CNS), features associated with the human disease multiple sclerosis (MS), develop in mice after injection of murine T-cell clones specific for the autoantigen myelin basic protein (MBP). We examined the fine specificity of three independently derived encephalitogenic T-cell clones using synthetic polypeptides derived from portions of the N-terminal sequence of MBP. These clones appear functionally identical; they all respond to an epitope in the N-terminal nine amino acid residues in association with the same class II (I-A) molecules of the major histocompatibility complex (MHC). Both the N-terminal acetyl moiety and the first residue (Ala) are necessary for recognition. Only N-terminal MBP peptides recognized by these clones were found to cause encephalomyelitis (EAE) in vivo. These results show that the N-terminal MBP-specific T lymphocytes that mediate autoimmune encephalomyelitis are a small population with a limited repertoire; they all recognise the same combination of MHC and target. 相似文献