全文获取类型
收费全文 | 79279篇 |
免费 | 5683篇 |
国内免费 | 7058篇 |
出版年
2024年 | 281篇 |
2023年 | 1565篇 |
2022年 | 2115篇 |
2021年 | 2728篇 |
2020年 | 2641篇 |
2019年 | 3647篇 |
2018年 | 2964篇 |
2017年 | 2324篇 |
2016年 | 2371篇 |
2015年 | 2665篇 |
2014年 | 4149篇 |
2013年 | 5626篇 |
2012年 | 3127篇 |
2011年 | 3821篇 |
2010年 | 2880篇 |
2009年 | 3563篇 |
2008年 | 3599篇 |
2007年 | 3836篇 |
2006年 | 3401篇 |
2005年 | 3189篇 |
2004年 | 2769篇 |
2003年 | 2492篇 |
2002年 | 2410篇 |
2001年 | 1919篇 |
2000年 | 1654篇 |
1999年 | 1509篇 |
1998年 | 1449篇 |
1997年 | 1316篇 |
1996年 | 1187篇 |
1995年 | 1125篇 |
1994年 | 1084篇 |
1993年 | 979篇 |
1992年 | 936篇 |
1991年 | 924篇 |
1990年 | 699篇 |
1989年 | 700篇 |
1988年 | 663篇 |
1987年 | 545篇 |
1986年 | 527篇 |
1985年 | 771篇 |
1984年 | 971篇 |
1983年 | 536篇 |
1982年 | 732篇 |
1981年 | 724篇 |
1980年 | 612篇 |
1979年 | 486篇 |
1978年 | 356篇 |
1977年 | 330篇 |
1976年 | 318篇 |
1973年 | 219篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Plant somatic cells have the capability to switch their cell fates from differentiated to undifferentiated status under proper
culture conditions, which is designated as totipotency. As a result, plant cells can easily regenerate new tissues or organs
from a wide variety of explants. However, the mechanism by which plant cells have such remarkable regeneration ability is
still largely unknown. In this study, we used a set of meristem-specific marker genes to analyze the patterns of stem cell
differentiation in the processes of somatic embryogenesis as well as shoot or root organogenesis in vitro. Our studies furnish preliminary and important information on the patterns of the de novo stem cell differentiation during various types of in vitro organogenesis. 相似文献
2.
J.G. Roddick 《Phytochemistry》1974,13(1):9-25
The literature relating to chemical, biochemical and biological aspects of the steroidal glycoalkaloid, α-tomatine, is reviewed. The alkaloid, which can be used as a starting compound for the synthesis of steroidal hormones, is toxic to a wide range of living organisms. The significance of tomatine to plants which elaborate it is discussed and some possible uses of the compound are mentioned. 相似文献
3.
4.
5.
《Cell reports》2020,30(1):112-123.e4
- Download : Download high-res image (131KB)
- Download : Download full-size image
6.
7.
In this work, incorporation of plasmid DNA, pre-complexed with PEI, into polyelectrolyte multilayers has been studied to further develop platforms for local gene delivery. Polyplex embedding in synthetic and naturally degradable architectures was efficient for transfection of human hepato-cellular carcinoma cells. 相似文献
8.
Papers on the mechanisms of translation initiation in mammals studied by reconstruction of initiation complexes from individual components are reviewed. The author points to the constraints of this approach and to the pitfalls ignoring which one might come to erroneous conclusions and even artifacts. In addition, some methods employed in the field as well as some technical problems are discussed in the paper, together with the means of obviating them. The review could be a guidebook for newcomers into this quite labor-consuming field. 相似文献
9.
Complementarity of regulation for the two glutamine synthetases from Bacillus caldolyticus, an extreme thermophile 总被引:1,自引:0,他引:1
F C Wedler D S Shreve K E Fisher D J Merkler 《Archives of biochemistry and biophysics》1981,211(1):276-287
Chromatophores from Rhodopseudomonas capsulata cells grown semiaerobically in the dark oxidize NADH, succinate, and dichlorophenolindophenol. In the presence of N3? these activities are inhibited, but light induces oxidation of dichlorophenolindophenol with O2 as a terminal electron acceptor. Cyanide also inhibits electron transport but much higher concentrations are required to inhibit the photooxidation than the dark oxidation. The photooxidation was studied in a mutant strain of Rhodopseudomonas capsulata (YIV) which cannot grow anaerobically in the light, but similarly to the wild type, grows in the presence of oxygen. Chromatophores from YIV mutant catalyze photophosphorylation and dark oxidation activities with the same properties as those of the wild type. However, the rate of photooxidation in the mutant is only one-third that of the wild type. Based on the differential inhibitor sensitivity and on the mutation it is suggested that the photooxidase is different from the two respiratory oxidases and that this photooxidation activity might be essential for growth of the cells under anaerobic conditions in the light. 相似文献
10.
Monica Driscoll 《Developmental neurobiology》1992,23(9):1327-1351
In C. elegans, cell death can be readily studied at the cellular, genetic, and molecular levels. Two types of death have been characterized in this nematode: (1) programmed cell death, which occurs as a normal component in development; and (2) pathological cell death which occurs aberrantly as a consequence of mutation. Analysis of mutations that disrupt programmed cell death in various ways has defined a genetic pathway for programmed cell death which includes genes that perform such functions as the determination of which cells die, the execution of cell death, the engulfment of cell corpses, and the digestion of DNA from dead cells. Molecular analysis is providing insightinto the nature of the molecules that function in these aspects of programmed cell death. Characterization of some genes that mutate to induce abnormal cell death has defined a novel gene family called degenerins that encode putative membrane proteins. Dominant alleles of at least two degenerin genes, mec-4 and deg-1, can cause cellular swelling and late onset neurodegeneration of specific groups of cells. © 1992 John Wiley & Sons, Inc. 相似文献