全文获取类型
收费全文 | 56篇 |
免费 | 4篇 |
国内免费 | 1篇 |
出版年
2021年 | 1篇 |
2019年 | 2篇 |
2016年 | 1篇 |
2015年 | 7篇 |
2013年 | 1篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 4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 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有61条查询结果,搜索用时 15 毫秒
1.
2.
Alexander I. Roitbak Elijah V. Ocherashvili Peter R. Laming Tamara A. Roitbak 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(3):327-333
Summary In 17 frogs (Rana esculenta var ridibunda) immobilised with succinyl choline the optic tectal surface was stimulated by trains of electrical pulses or by a flash to the contralateral eye. Sustained potential shifts (SPSs) and changes in extracellular potassium concentration ( [K+]0) were simultaneously recorded.In response to electrical stimulation SPSs of maximal amplitudes (1.19±0.1 mV) were recorded between 50 and 200 m in depth and maximal [K+]0 (0.69 ±0.08 mM) between 100 and 350 m. The changes of SPS and [K+]0 showed a close similarity in experiments with changes in voltage, pulse duration and frequency of stimuli within a train. The induced SPS had a duration of 28±1.54 s, the [K+]0 of 32±1.23 s.The flash stimulus induced an SPS and [K+]0 of maximal amplitudes between 50 and 200 m in depth with values of 0.57±0.1 mV and 0.29±0.03 mM respectively. An additional wave with a latency of ca 1 s and a duration of ca 3 s arose on the background of the SPS to a flash stimulus, associated with an additional increase in [K+]0.It is considered that the accumulation of K+ in extra-cellular space, with neuronal activity, results in depolarization of radial processes of ependymal glia. This is reflected in the neuropil of the upper layers of the optic tectum as an SPS.We would like to dedicate this article to the memory of Alexander Roitbak who died as a result of a tragic accident while this paper was in press. He will be remembered fondly especially for his contributions to understanding of the functions of Neuroglia. E.V.O., P.R.L., T.A.R. 相似文献
3.
The fusarium mycotoxin zearalenone was transformed in cell suspension cultures of Zea mays giving α- and β-zearalenol and the β-D-glu cos ides of zearalenone and α- and β-zearalenol. The structure of zearalenone-4-β-D-glucopyranoside was determined by liquid — chromatography-mass spectrometry and specific hydrolysis with β-glucosidase. α- and β-zearalenol and their glucosides were identified by co chromatography using tic and HPLC and glucosidase — treatment Up to 50% of the mycotoxin added was bound to a non extractable or “bound” residue fraction. After treating this residue by a sequential cell wall fractionation procedure, zearalenone was found to be bound mainly to starch, hemicellulose, and lignin fractions. 相似文献
4.
Gene transfer is a major factor in bacterial evolution 总被引:17,自引:3,他引:14
Lateral gene transfer in four strains of Salmonella enterica has been
assessed using genomic subtraction. Strain LT2 (subspecies I serovar
Typhimurium) chromosomal DNA was used as target and subtracted by three
subspecies I strains of serovars Typhimurium (S21), Muenchen (S71), Typhi
(M229), and a subspecies V strain (M321). Data from probing random cosmids
of LT2 DNA with preparations of the residual LT2 DNA after subtraction were
used to estimate the amounts of LT2 DNA not able to hybridize to strains
S21, S71, M229, and M321 to be in the range of 84-106, 191-355, 305-629,
and 778-1,286 kb, respectively. Several lines of evidence indicate that
most of this DNA is from genes not present in strain M321 and not from
genes that have diverged in sequence. The amounts correlate with the
divergence of the four strains as revealed by multilocus enzyme
electrophoresis and sequence variation of housekeeping genes. Sequence of
39 of the fragments from the M321 subtracted residual LT2 DNA revealed only
six inserts of known gene function with evidence of both gain and loss of
genes during the development of S. enterica clones. Sixteen of the 39
segments have 45% or lower G+C content, below the species average, but over
half are within the normal range for the species. We conclude that even
within a species, clones may differ by up to 20% of chromosomal DNA,
indicating a major role for lateral transfer, and that on the basis of G+C
content, a significant proportion of the DNA is from distantly related
species.
相似文献
5.
Peter Richard Laming Jörg -Peter Ewert 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1984,154(1):89-101
Summary Visual unit activity, EEG changes and sustained potential shifts (SPS) were recorded from the toad tectum whilst the animal was presented with a visual stimulus. Telencephalic EEGs were also recorded.On the surface of the tectum, retinal unit activity preceded a sustained negative shift in potential and an increase in the amplitude and dominant frequency of the EEG. In deeper layers of the tectum, T5 units with configurational selectivity for wormlike stimuli were found. The activity of these units followed a pronounced SPS and EEG change.Visual unit activity was most pronounced during the negative-going phase of the synchronised EEG, when there was also a small decrease in amplitude of neuronal spikes. Similarities between the latencies and durations of EEGs and SPSs, and their response decrements, on repeated stimulus presentation, implies a close relationship between them not shared by the visual units studied. The specific activity of tectal units is discussed in relation to the correlated EEG and SPS changes, which may form part of an adaptive sensitizing mechanism.Abbreviations
EEG
electroencephalogram
-
ERF
excitatory receptive field
-
SPS
sustained potential shift
-
T4, T5
tectal neurons 相似文献
6.
7.
PR Marcelino MS Aoki AFS Arruda CG Freitas A Mendez-Villanueva A Moreira 《Biology of sport / Institute of Sport》2016,33(1):37-42
The purpose of this study was to investigate the effect of court size on physiological responses and physical performance of young elite basketball players. Twelve male basketball players (18.6 ± 0.5 years; 88.8 ± 14.5 kg; 192.6 ± 6.5 cm) from an under-19 team performed two small-sided games (matches) with different court areas (28x15 m and 28x9 m; 28x15 and 28x9 protocols). The number of players (3x3) was kept the same in each protocol. The players performed a repeated-sprint ability (RSA) test before and after each match. Blood lactate concentration was collected before (pre) and after (post) the matches, and the session rating of perceived exertion (session-RPE) was determined 30 minutes after the match. Best and mean time in the RSA test were not different between the 28x15 and the 28x9 match protocols (p > 0.05). A significant difference was observed for lactate concentration from pre- to post-match (p < 0.05) in both protocols (28x15 and 28x9); however, there was no significant interaction between protocols. A similar session-RPE mean score (28x15: 7.2 ± 1.4 and 28x9: 6.6 ± 1.4) was detected for both protocols (p > 0.05, ES=0.41). In summary, the results of the current study suggest that the different court areas induced similar responses. Although there was no significant difference in effort perception, players tended to perceive a greater effort in the larger court size. 相似文献
8.
9.
Francine Z Marques Simon PR Romaine Matthew Denniff James Eales John Dormer Ingrid M Garrelds Lukasz Wojnar Katarzyna Musialik Barbara Duda-Raszewska Bartlomiej Kiszka Magdalena Duda Brian J Morris Nilesh J Samani AH Jan Danser Pawel Bogdanski Ewa Zukowska-Szczechowska Fadi J Charchar Maciej Tomaszewski 《Molecular medicine (Cambridge, Mass.)》2015,21(1):739-748
MicroRNA-181a binds to the 3′ untranslated region of messenger RNA (mRNA) for renin, a rate-limiting enzyme of the renin-angiotensin system. Our objective was to determine whether this molecular interaction translates into a clinically meaningful effect on blood pressure and whether circulating miR-181a is a measurable proxy of blood pressure. In 200 human kidneys from the TRANScriptome of renaL humAn TissuE (TRANSLATE) study, renal miR-181a was the sole negative predictor of renin mRNA and a strong correlate of circulating miR-181a. Elevated miR-181a levels correlated positively with systolic and diastolic blood pressure in TRANSLATE, and this association was independent of circulating renin. The association between serum miR-181a and systolic blood pressure was replicated in 199 subjects from the Genetic Regulation of Arterial Pressure of Humans In the Community (GRAPHIC) study. Renal immunohistochemistry and in situ hybridization showed that colocalization of miR-181a and renin was most prominent in collecting ducts where renin is not released into the systemic circulation. Analysis of 69 human kidneys characterized by RNA sequencing revealed that miR-181a was associated with downregulation of four mitochondrial pathways and upregulation of 41 signaling cascades of adaptive immunity and inflammation. We conclude that renal miR-181a has pleiotropic effects on pathways relevant to blood pressure regulation and that circulating levels of miR-181a are both a measurable proxy of renal miR-181a expression and a novel biochemical correlate of blood pressure. 相似文献
10.
Kouki?HikosakaEmail author Yusuke?Onoda Toshihiko?Kinugasa Hisae?Nagashima Niels?PR?Anten Tadaki?Hirose 《Ecological Research》2005,20(3):243-253
Elevated CO2 enhances photosynthesis and growth of plants, but the enhancement is strongly influenced by the availability of nitrogen. In this article, we summarise our studies on plant responses to elevated CO2. The photosynthetic capacity of leaves depends not only on leaf nitrogen content but also on nitrogen partitioning within a leaf. In Polygonum cuspidatum, nitrogen partitioning among the photosynthetic components was not influenced by elevated CO2 but changed between seasons. Since the alteration in nitrogen partitioning resulted in different CO2-dependence of photosynthetic rates, enhancement of photosynthesis by elevated CO2 was greater in autumn than in summer. Leaf mass per unit area (LMA) increases in plants grown at elevated CO2. This increase was considered to have resulted from the accumulation of carbohydrates not used for plant growth. With a sensitive analysis of a growth model, however, we suggested that the increase in LMA is advantageous for growth at elevated CO2 by compensating for the reduction in leaf nitrogen concentration per unit mass. Enhancement of reproductive yield by elevated CO2 is often smaller than that expected from vegetative growth. In Xanthium canadense, elevated CO2 did not increase seed production, though the vegetative growth increased by 53%. As nitrogen concentration of seeds remained constant at different CO2 levels, we suggest that the availability of nitrogen limited seed production at elevated CO2 levels. We found that leaf area development of plant canopy was strongly constrained by the availability of nitrogen rather than by CO2. In a rice field cultivated at free-air CO2 enrichment, the leaf area index (LAI) increased with an increase in nitrogen availability but did not change with CO2 elevation. We determined optimal LAI to maximise canopy photosynthesis and demonstrated that enhancement of canopy photosynthesis by elevated CO2 was larger at high than at low nitrogen availability. We also studied competitive asymmetry among individuals in an even-aged, monospecific stand at elevated CO2. Light acquisition (acquired light per unit aboveground mass) and utilisation (photosynthesis per unit acquired light) were calculated for each individual in the stand. Elevated CO2 enhanced photosynthesis and growth of tall dominants, which reduced the light availability for shorter subordinates and consequently increased size inequality in the stand. 相似文献