全文获取类型
收费全文 | 230篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
系统科学 | 1篇 |
现状及发展 | 100篇 |
研究方法 | 25篇 |
综合类 | 110篇 |
自然研究 | 5篇 |
出版年
2019年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 11篇 |
2011年 | 17篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 7篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 4篇 |
1967年 | 10篇 |
1966年 | 1篇 |
1965年 | 5篇 |
1964年 | 4篇 |
1955年 | 1篇 |
排序方式: 共有241条查询结果,搜索用时 15 毫秒
181.
182.
B. D. Tilak K. G. Das H. M. El-Namaky 《Cellular and molecular life sciences : CMLS》1967,23(8):609-609
Zusammenfassung Es wird gezeigt, dass bei geeigneten Verbindungen die Ausstossung der Methylengruppe im Massenspektrum eine bevorzugte Reaktionsweise darstellt. Diese Reaktionsweise gleicht derjenigen der Abgabe von Kohlenmonoxyd aus cyclischen Ketonen oder Chinonen. 相似文献
183.
Adaptation to seasonal change is a crucial component of an organism's survival strategy. To monitor seasonal variation, organisms have developed the capacity to measure day length (photoperiodism). Day-length assessment involves the photoperiodic control of flowering in Arabidopsis thaliana, whereby the coincidence of light and high expression of CONSTANS (CO) induces the expression of FLOWERING LOCUS T (FT), leading to flowering in long-day conditions. Although controlling CO expression is clearly a key step in day-length discrimination, the mechanism that generates day-length-dependent CO expression remains unknown. Here we show that the clock-controlled FLAVIN-BINDING, KELCH REPEAT, F-BOX (FKF1) protein has an essential role in generating the diurnal CO peak and that this function is dependent on light. We show that a recombinant FKF1 LIGHT, OXYGEN OR VOLTAGE (LOV) domain binds the chromophore flavin mononucleotide and undergoes light-induced photochemistry, indicating that FKF1 may function as a photoperiodic blue-light receptor. It is likely that the circadian control of FKF1 expression and the light regulation of FKF1 function coincide to control the daytime CO waveform precisely, which in turn is crucial for day-length discrimination by Arabidopsis. 相似文献
184.
185.
In heterochronic mutants the relative timing of developmental events is altered compared with the wild type. This generally results in a disordered embryo, though heterochronic mutations may also be an important source of evolutionary variation. In the rapidly developing (rde) mutants of Dictyostelium, stalk and spore cells differentiate before morphogenesis is complete. We have traced the lesion in one class of these mutants to the regulatory subunit of cyclic AMP-dependent protein kinase (pk-A). Inactivation of this protein results in the unrestrained activity of the catalytic subunit, so prematurely triggering terminal cell differentiation. 相似文献
186.
Summary Cytogenetic analyses of bone marrow and meiotic cells in an apparently normal male mouse clearly revealed the presence of an extra Y chromosome leading to 2n=41, XYY. During meiosis the sex chromosomes formed all possible types of combinations (XYY, XY/Y, YY/X and X/Y/Y). Compared to 40, XY normal mice, the sperm count was significantly less, but the incidence of sperm head abnormality was at the normal level.Acknowledgment. The authors are grateful to Prof. G. K. Manna, Department of Zoology, Kalyani University, for his valuable comments and Prof. M. C. Dash, School of Life Sciences, Sambalpur University for providing necessary facilities. Thankful acknowledgment to CSIR, India for a SRF awarded to RNK. 相似文献
187.
188.
Summary The free energy transfer (G
t
0
) enthalpy of transfer (H
t
0
) and entropy of transfer (S
t
0
) of NaBrO3 and NaIO3 from water to 10, 20 and 30% dioxane-water mixtures have been studied using conductance measurements. The chemical and electrical parts of these transfers of thermodynamic parameters have been estimated.To whom reprint requests should be addressed. 相似文献
189.
Tannins occur naturally in relatively abundant amounts in fruits, herbal medicines and common beverages. Thus an understanding of how these polyphenols affect peptide hormone action is of importance. We report here that tannic acid (a hydrolysable tannin) inhibits insulin-stimulated lipogenesis in rat adipose tissue in vitro, with an IC50 estimated to be about 350 M. However, its monomer, gallic acid, did not show a similar inhibitory effect at concentrations up to 1 mM. The inhibition by tannic acid was less evident with higher concentrations of bovine serum albumin in the incubation buffer. This was attributed to the formation of a tannin-protein complex between bovine serum albumin and tannic acid. In a binding assay, it was observed that the specific binding of insulin to its receptor was not inhibited by tannic acid in the concentration range 0–200 M. However, insulin-stimulated autophosphorylation of the insulin receptor, and receptor-associated tyrosine kinase phosphorylation of RR-SRC peptide, were inhibited by tannic acid at concentrations as low as 25 M. Our data do not support the current speculation that tannins affect the activity of peptide hormones by binding to them. Therefore, our finding opens up a new perspective in the understanding of the mode of action of tannins on such hormones. 相似文献
190.
The machinery used by the cell to perform essential biological processes is made up of large molecular assemblies. One such complex, the proteasome, is the central molecular machine for removal of damaged and misfolded proteins from the cell. Here we show that for the 670-kilodalton 20S proteasome core particle it is possible to overcome the molecular weight limitations that have traditionally hampered quantitative nuclear magnetic resonance (NMR) spectroscopy studies of such large systems. This is achieved by using an isotope labelling scheme where isoleucine, leucine and valine methyls are protonated in an otherwise highly deuterated background in concert with experiments that preserve the lifetimes of the resulting NMR signals. The methodology has been applied to the 20S core particle to reveal functionally important motions and interactions by recording spectra on complexes with molecular weights of up to a megadalton. Our results establish that NMR spectroscopy can provide detailed insight into supra-molecular structures over an order of magnitude larger than those routinely studied using methodology that is generally applicable. 相似文献