全文获取类型
收费全文 | 365篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 17篇 |
理论与方法论 | 1篇 |
现状及发展 | 52篇 |
研究方法 | 32篇 |
综合类 | 244篇 |
自然研究 | 21篇 |
出版年
2022年 | 2篇 |
2020年 | 2篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 20篇 |
2011年 | 39篇 |
2010年 | 7篇 |
2008年 | 20篇 |
2007年 | 18篇 |
2006年 | 23篇 |
2005年 | 16篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 9篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1992年 | 8篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1971年 | 4篇 |
1970年 | 12篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 4篇 |
1966年 | 6篇 |
1965年 | 5篇 |
1963年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有367条查询结果,搜索用时 15 毫秒
111.
Peripheral vascular effects of histamine administered into the cerebral ventricles of anaesthetized cats 总被引:1,自引:0,他引:1
T White 《Experientia》1965,21(3):132-133
112.
11,12-Dihydroxy-7-methyl-4,5,6,7,7a,8-hexahydrophenanthro[10,1-b,c]-azepine (2), a homologue of apomorphine (1), has been found to be devoid of dopaminergic effects. The biological differences between apomorphine and this homologue are explained in terms of differences in conformation of the two molecules. 相似文献
113.
IFNgamma and lymphocytes prevent primary tumour development and shape tumour immunogenicity 总被引:51,自引:0,他引:51
Shankaran V Ikeda H Bruce AT White JM Swanson PE Old LJ Schreiber RD 《Nature》2001,410(6832):1107-1111
Lymphocytes were originally thought to form the basis of a 'cancer immunosurveillance' process that protects immunocompetent hosts against primary tumour development, but this idea was largely abandoned when no differences in primary tumour development were found between athymic nude mice and syngeneic wild-type mice. However, subsequent observations that nude mice do not completely lack functional T cells and that two components of the immune system-IFNgamma and perforin-help to prevent tumour formation in mice have led to renewed interest in a tumour-suppressor role for the immune response. Here we show that lymphocytes and IFNgamma collaborate to protect against development of carcinogen-induced sarcomas and spontaneous epithelial carcinomas and also to select for tumour cells with reduced immunogenicity. The immune response thus functions as an effective extrinsic tumour-suppressor system. However, this process also leads to the immunoselection of tumour cells that are more capable of surviving in an immunocompetent host, which explains the apparent paradox of tumour formation in immunologically intact individuals. 相似文献
114.
Humans in space 总被引:7,自引:0,他引:7
Many successful space missions over the past 40 years have highlighted the advantages and necessity of humans in the exploration of space. But as space travel becomes ever more feasible in the twenty-first century, the health and safety of future space explorers will be paramount. In particular, understanding the risks posed by exposure to radiation and extended weightlessness will be crucial if humans are to travel far from Earth. 相似文献
115.
116.
117.
卵巢癌是较常见的妇女肿瘤,其生存率较低,因此,控制此病的重点应该是预防。实验室研究显示绿茶具有预防作用,但人群调查则结果不一。茶是我国居民最常用的饮品,如果其预防卵巢癌的作用是确实的,饮茶将是一个较好的预防途径。本研究的目的在于调查常用饮品对卵巢癌的影响,以便为此病的预防提供依据。 相似文献
118.
Preliminary observations of a bacteriophage infecting Xenorhabdus luminescens (Enterobacteriaceae) 总被引:4,自引:0,他引:4
A bacteriophage infective to Xenorhabdus luminescens, a bacterial symbiont of heterorhabditid nematodes, was recovered from insects that supported poor nematode development. Plaque tests showed the phage particles to be infective only to primary and not secondary colonies of X. luminescens. The phage was not infective to X. nematophilus primaries or secondaries. The bacteriophage particles ranged 80-90 nm in length, with the head ranging from 40 to 50 nm in diameter. Restriction analysis was performed on isolated bacteriophage DNA. This first report of a bacteriophage from Xenorhabdus species has practical implications since it could be detrimental to cultures of Heterorhabditis nematodes that are being produced throughout the world for the biological control of insects. 相似文献
119.
The 3-A structure of DNA-binding protein II, which exhibits histone-like properties in bacteria, has been determined. The molecule is dimeric and appears to bind to the phosphate backbone of DNA through two symmetry-related arms. A mechanism by which the protein induces DNA supercoiling is proposed. 相似文献
120.
R. B. Chronister J. J. Bernstein S. F. Zornetzer L. E. White Jr. 《Cellular and molecular life sciences : CMLS》1973,29(5):588-589
Zusammenfassung Erstmaliger morphometrischer Nachweis bei 2 Gruppen reifer, altersunterschiedlicher Ratten, dass die Zahl der Synapsen im Hippocampus mit dem Alter zunimmt, wobei die effektive Steigerungsrate auch mit Umwelteinflüssen zusammenhängen könnte.
This work was supported by grants from the U.S. National Institutes of Health to JJB (No. NS-06164) and to LEW,Jr., (No. NS-09358) and funds from the Center for Neurobiological Sciences of the University of Florida (No. NIH-MH-10320). 相似文献
This work was supported by grants from the U.S. National Institutes of Health to JJB (No. NS-06164) and to LEW,Jr., (No. NS-09358) and funds from the Center for Neurobiological Sciences of the University of Florida (No. NIH-MH-10320). 相似文献