全文获取类型
收费全文 | 5425篇 |
免费 | 614篇 |
国内免费 | 1篇 |
出版年
2021年 | 55篇 |
2020年 | 44篇 |
2019年 | 56篇 |
2018年 | 73篇 |
2017年 | 53篇 |
2016年 | 79篇 |
2015年 | 151篇 |
2014年 | 171篇 |
2013年 | 223篇 |
2012年 | 279篇 |
2011年 | 281篇 |
2010年 | 180篇 |
2009年 | 160篇 |
2008年 | 227篇 |
2007年 | 212篇 |
2006年 | 196篇 |
2005年 | 211篇 |
2004年 | 191篇 |
2003年 | 192篇 |
2002年 | 211篇 |
2001年 | 194篇 |
2000年 | 177篇 |
1999年 | 149篇 |
1998年 | 78篇 |
1997年 | 61篇 |
1996年 | 59篇 |
1995年 | 45篇 |
1994年 | 56篇 |
1993年 | 49篇 |
1992年 | 111篇 |
1991年 | 106篇 |
1990年 | 84篇 |
1989年 | 110篇 |
1988年 | 90篇 |
1987年 | 95篇 |
1986年 | 75篇 |
1985年 | 91篇 |
1984年 | 59篇 |
1983年 | 65篇 |
1982年 | 56篇 |
1981年 | 49篇 |
1980年 | 54篇 |
1979年 | 68篇 |
1978年 | 49篇 |
1977年 | 71篇 |
1976年 | 50篇 |
1975年 | 50篇 |
1974年 | 42篇 |
1973年 | 42篇 |
1971年 | 39篇 |
排序方式: 共有6040条查询结果,搜索用时 15 毫秒
61.
62.
Paul H. Gumerlock Benjamin F. Edwards Arline D. Deitch Frederick J. Meyers 《In vitro cellular & developmental biology. Plant》1988,24(5):429-434
Summary A human cell line has been established from a renal adenocarcinoma rib metastasis of a 58-y-old male. This cell line has been
maintained in continuous culture for 20 mo. through more than 50 passages. It displays simulataneous expression of the intermediate
filaments cytokeratin and vimentin. Flow cytometric analysis of DNA content reveals a major hyperdiploid population.
This work was supported in part by a grant from Triton Biosciences, Inc. 相似文献
63.
The electrochemical properties of three nitroimidazoles, a nitropyrazole, a nitrofuran and three nitroben-zenoid compounds have been extensively investigated in a range of solvents. The reduction pathway for the nitro group is independent of the cyclic function to which it is attached, but is strongly influenced by the nature of the solvent. In aqueous media, generally, a single, irreversible 4-electron reduction occurs to give the hydroxylamine. In aprotic media (dimethylformamide, methylene chloride or dimethylsulphoxide), a reversible one-electron reduction takes place to form a stable nitro radical anion. At more negative values, a further 3-electron reduction occurs, irreversibly to give the hydroxylamine. In mixed aqueous-organic systems, intermediate behaviour is found, with the reversibility of the RNO2/RNO2- couple increasing with addition of organic medium. The control of the reduction pathway, by changing the electrolytic medium is discussed in relation to the biological activities of the drugs and identification of the short-lived reduction intermediate responsible for DNA damage. 相似文献
64.
Homosexual mounting in apes and prosimians is rare. Male-male mounting was observed between an adult male white-handed gibbon
and an adolescent male in the same group. The behaviour is discussed in terms of the gibbon group's social structure and the
development of the adolescent. It is suggested that this behaviour provides reassurance for the adolescent gibbon. 相似文献
65.
66.
Pea lectin is correctly processed,stable and active in leaves of transgenic potato plants 总被引:5,自引:0,他引:5
Glyn A. Edwards Andrew Hepher Stephen P. Clerk Donald Boulter 《Plant molecular biology》1991,17(1):89-100
A gene encoding the preproprotein of the pea (Pisum sativum) lectin was expressed in transgenic potato plants using a cauliflower mosaic virus (CaMV) 35S promoter or a tobacco ribulose bisphosphate carboxylase small subunit (ssRubisco) promoter. Presence of the pea lectin to levels greater than 1% of total soluble leaf protein was detected by radioimmunoassay (RIA). The pattern of expression derived from the two promoters was established using both RIA and a squash-blot immunolocalisation technique. Western blotting demonstrated that the preproprotein was correctly processed, generating and subunits that assembled to give an isolectin form observed in pea seeds and roots. It was also found that the haemagglutination activity and specificity of pea lectin synthesised in transgenic potato leaves was comparable to purified lectin from pea cotyledons. 相似文献
67.
Body size plays an important role in the outcome of aggressive encounters between males of the symbiotic freshwater miteUnionicola formosa. Since intruding males displace resident males as often as resident males successfully defend their territory (mantle cavity of a mussel), resident males do not hold a competitive advantage during male-male aggressive encounters. Larger male size probably enhances a male's success when competing for receptive females. 相似文献
68.
Thin cardiac slices (100-200 microns) from newborn (1-14 days old) rat heart ventricles were used for patch clamp recordings. High resistance seals (10-50 GOhms) between patch-clamp pipettes and the membrane of cardiac cells as well as classical patch-clamp configurations can be achieved on this preparation without any enzymatic treatment of tissue. Resisting potential for cardiac cells measured in whole-cell configuration ranged between -30 and -65 mV. Averaged sodium currents and single inward rectifying potassium elementary currents recorded in cell-attached mode displayed basic features similar to those previously reported for isolated rat ventricular cells. Application of the method described here in cardiac electrophysiology will allow patch-clamp studies on heart cells without the complicated procedures of cell isolation. In addition, the uncertainty associated with enzyme treatment can be avoided. In future, this technique could be a new tool for studying electrophysiological properties of heart cells in situ. 相似文献
69.
70.