全文获取类型
收费全文 | 82篇 |
免费 | 1篇 |
专业分类
化学 | 36篇 |
数学 | 5篇 |
物理学 | 42篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2018年 | 1篇 |
2016年 | 3篇 |
2013年 | 2篇 |
2012年 | 5篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1984年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有83条查询结果,搜索用时 15 毫秒
21.
With mutation rates smaller than unity, the bitstring model for Monte Carlo simulations of biological ageing is shown to agree reasonably with human mortality in West Germany around 1987. 相似文献
22.
Effects of acoustic overstimulation on spectral and temporal processing in the amphibian auditory nerve 总被引:1,自引:0,他引:1
Activity of isolated auditory-nerve fibers in tree frogs (Eleutherodactylus coqui) exposed to continuous 3-min tones of different intensities at their characteristic frequencies (CFs) was recorded. Period histograms show a retardation in the preferred phase of discharge during and after the cessation of the exposure. Postexposure phase shift is concomitant with an elevation in CF thresholds and related to the level of tone exposure above threshold. Vector strength does not show comparable trends of change; postexposure shifts are related to preexposure CF thresholds. Recovery of phase retardation is rapid; units exposed to successive 3-min tones of the same intensities with intervals of 10-14 min between exposures experienced similar changes in their patterns of temporal discharge. Micromechanical changes affecting stereocilia stiffness or structural alterations in the tectorial membrane of the amphibian papilla may underly the transitory phase shifts observed in traumatized anuran auditory fibers. 相似文献
23.
Perspectives on bioenergy and biotechnology in Brazil 总被引:4,自引:0,他引:4
Adalberto Pessoa-Jr Inêes Conceição Roberto Marcelo Menossi Raphael Revert dos Santos Sylvio Ortega Filho Thereza Christina Vessoni Penna 《Applied biochemistry and biotechnology》2005,121(1-3):59-70
Brazil is one of the world’s largest producers of alcohol from biomass at low cost and is responsible for more than 1 million
direct jobs. In 1973, the Brazilian Program of Alcohol (Proalcool) stimulated the creation of a bioethanol industry that has
led to large economic, social, and scientific improvements. In the year 1984, 94.5% of Brazil’s cars used bioethanol as fuel.
In 2003/2004, 350.3 million of sugarcane produced 24.2 million t of sugar and 14.4 billion L of ethanol for an average 4.3
million cars using ethanol. Since its inception, cumulative investment in Proalcool totals US$11 billion, and Brazil has saved
US$27 billion in oil imports. The ethanol production industry from sugarcane generates 152 times more jobs than would have
been the case if the same amount of fuel was produced from petroleum, and the use of ethanol as a fuel is advantageous for
environmental reasons. In 2003, one of the biggest Brazilian ethanol industries started consuming 50% of the residual sugarcane
bagasse to produce electrical energy (60 MW), a new alternative use of bioenergy for the Brazilian market. Other technologies
for commercial uses of bagasse are in development, such as in the production of natural fibers, sweeteners (glucose and xylitol),
single-cell proteins, lactic acid, microbial enzymes, and many other products based on fermentations (submerged and semisolid).
Furthermore, studies aimed at the increase in the biosynthesis of sucrose and, consequently, ethanol productivity are being
conducted to understand the genetics of sugarcane. Although, at present, there remain technical obstacles to the economic
use of some ethanol industry residues, several research projects have been carried out and useful data generated. Efficient
utilization of ethanol industry residues has created new opportunities for new value-added products, especially in Brazil,
where they are produced in high quantities. 相似文献
24.
Penna Thereza Christina Vessoni Ishii Marina Machoshvili Irene Alexeevna Marques Marcelo 《Applied biochemistry and biotechnology》2002,98(1-9):525-538
Paper strips inoculated with spores of Bacillus stearothermophilus ATCC 7953 were conventionally dried (lot 1) and lyophilized (lot 2); stored in defined environments of 32 and 86% relative
humidity at 10, 25 and 33°C for 210 d; and submitted to moist heat treatments at 121°C. A significant decrease in thermal
resistance from initial starting levels was found for lyophilized bioindicators stored at 86% relative humidity. The respective
average D
121°C values were 1.55 ± 0.05 and 1.37 ± 0.10 min for lyophilized bioindicators stored at 32 and 86% relative humidity; and 1.65±0.15min
and 1.57 ± 0.11 min for dried bioindicators stored in the same environments. 相似文献
25.
We analyze the time decay of small amplitude density perturbations in systems of highly packed Brownian hard rods, relaxing towards a uniform density distribution. The results of Brownian dynamics simulations and those of the deterministic dynamic density functional (DDF) theory, are contrasted with a new theoretical approach beyond the DDF assumptions. We characterize dynamical correlation modes which, having the lowest relaxation time, determine the late time evolution of the system. The spectrum of possible time decays has a continuous band structure, with pockets of discrete values, near the minima of the DDF results, where the validity of that theory appears to be well established. 相似文献
26.
Thereza Christina Vessoni Penna Angela Faustino Jozala Thomas Rodolfo Gentille Adalberto Pessoa Jr. Olivia Cholewa 《Applied biochemistry and biotechnology》2006,129(1-3):334-346
Nisin, a bacteriocin produced during the exponential growth phase of Lactococcus lactis ATCC 11454, inhibits the growth of a broad range of Grampositive bacteria. Gram-negative bacteria can also be inhibited by nisin with EDTA. In this study, nisin production was assayed by the agar diffusion method using Lactobacillus sake ATCC 15521 and a recombinant Escherichia coli DH5-α expressing the recombinant green fluorescent protein as the nisin-susceptible test organisms. The titers of nisin expressed and released in culture media were quantified and expressed in arbitrary units (AU/mL of medium) and converted to standard nisin concentration (Nisaplin®, 25 mg of pure nisin with an activity of 1×106 AU/mL). The expression and release of nisin by L. lactis in skimmed milk (9.09% total solids) with Man Rugosa Shepeer-Bacto Lactobacilli broth (1∶1) was monitored in a 5 L New Brunswick fermentor. Combining EDTA with nisin increased the bactericidal effect of nisin on the bacteria examined. The presence of EDTA was necessary to inhibit E. coli growth with nisin. L. sake was shown to be a good indicator for the evaluation of nisin release in the culture media, including with the addition of EDTA. 相似文献
27.
Penna Thereza Christina Vessoni Chiarini Eb Machoshvili Irene Alexeevna Ishii Marina Pessoa Adalberto 《Applied biochemistry and biotechnology》2002,98(1-9):791-802
The recombinant green fluorescent protein (gfp
uv
) was expressed by Escherichia coli DH5-α cells transformed with the plasmid pGFPuv. The gfp
uv
was selectively permeabilized from the cells in buffer solution (25 mM Tris-HCl, pH 8.0), after freezing (−70°C for 15 h), by four freeze (−20°C)/thaw cycles interlaid by sonication. The average
content of released gfp
uv
(experiment 2) was 7.76, 34.58, 39.38, 12.90, and 5.38%, for the initial freezing (−70°C) and the first, second, third and
fourth freeze/thaw cycles, respectively. Superfusion on freezing was observed between −11°C and −14°C, after which it reached
−20°C at 0.83°C/min. 相似文献
28.
We analyze thoroughly the mean-field dynamics of a linear chain of three coupled Bose-Einstein condensates, where both the tunneling and the central-well relative depth are adjustable parameters. Owing to its nonintegrability, entailing a complex dynamics with chaos occurrence, this system is a paradigm for longer arrays whose simplicity still allows a thorough analytical study. We identify the set of dynamics fixed points, along with the associated proper modes, and establish their stability character depending on the significant parameters. As an example of the remarkable operational value of our analysis, we point out some macroscopic effects that seem viable to experiments. 相似文献
29.
Anomalous leveling of the A1(Z) polaritons of ferroelectric LiTaO3 was observed below certain wavevectors on approaching the Curie temperature. The saturation is attributed to the destruction of the polaritons propagation length due to the crystal domain variations, which is interpreted as a new phase transition model. The almost linear dependence of the propagation length does indicate the Curie temperature to be 873 K. 相似文献
30.