全文获取类型
收费全文 | 234篇 |
免费 | 18篇 |
专业分类
252篇 |
出版年
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 5篇 |
2010年 | 7篇 |
2009年 | 3篇 |
2008年 | 10篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1966年 | 2篇 |
1964年 | 3篇 |
1959年 | 1篇 |
1954年 | 1篇 |
1927年 | 1篇 |
排序方式: 共有252条查询结果,搜索用时 0 毫秒
141.
Polyanichko A. M. Chikhirzhina E. V. Andrushchenko V. V. Kostyleva E. I. Wieser H. Vorob'ev V. I. 《Molecular Biology》2004,38(4):590-600
The analysis of absorption and circular dichroism spectra in UV and IR regions showed that Ca2+ ions interact with the phosphate groups of DNA and the HMGB1 protein. Not only the negatively charged C-terminal part of the protein molecule, but also its DNA-binding domains participate in the interaction with metal ions. The latter leads to a change in the mode of protein–DNA interaction. The presence of Ca2+ ions prevents the formation of ordered supramolecular structures specific for the HMGB1–DNA complexes but promotes intermolecular aggregation. The structure of DNA complexes with the HMGB1 protein lacking the C-terminal tail appeared to be the most sensitive to the presence of Ca2+ ions. These data indicate that Ca2+ ions play no structural role in the HMGB1–DNA complexes, and their presence is not necessary for DNA compaction in such systems. 相似文献
142.
The energetics of starvation and growth after refeeding in juveniles of three cyprinid species 总被引:12,自引:0,他引:12
Wolfgang Wieser Gerhard Krumschnabel Julius P. Ojwang-Okwor 《Environmental Biology of Fishes》1992,33(1-2):63-71
Synopsis Experiments were conducted to monitor changes in body mass and metabolic energy expenditure before, during, and after periods of starvation in juveniles of three species of cyprinids: Leuciscus cephalus, Chalcalburnus chalcoides mento, and Scardinius erythrophthalmus. During the starvation period all fish lost weight at about the same rate and the total amount of oxygen consumed during an experimental period of 20 h was about 40% lower in the starved than in the fed groups. Upon refeeding, both mass specific maintenance; and routine rates of metabolism as well as relative growth rates increased rapidly, the peaks of these increases being directly proportional to the length of the starvation period. Maximum compensatory growth was observed after four weeks of starvation in C. chalcoides and S. erythrophthalmus, with relative growth rates reaching 30% d-1 during the first measuring interval after refeeding. The pattern of time-dependent compensatory growth displayed by these fish is similar to the responses of a colonial hydroid in which the rate of catch-up growth increased with the amount of stress to which the animals had been exposed. The exact cost of compensatory growth cannot be calculated because oxygen consumption and growth were not measured simultaneously. However, on the basis of data and calculations reported by Wieser & Medgyesy (1990) it appears that compensatory growth, if fuelled by the metabolic power indicated by our measurements of oxygen consumption, would have to be about twice as efficient as normal growth in the related species Rutilus rutilus. 相似文献
143.
N.?A.?El-FaramawyEmail author I.?El-Somany A.?Mansour A.?M.?Maghraby H.?Eissa A.?Wieser 《Radiation and environmental biophysics》2018,57(1):63-68
Tooth enamel samples from molar teeth of camel were prepared using a combined procedure of mechanical and chemical tooth treatment. Based on electron paramagnetic resonance (EPR) spectroscopy, the dose response of tooth enamel samples was examined and compared to that of human enamel. The EPR dose response of the tooth enamel samples was obtained through irradiation to gamma doses from 1 Gy up to 100 kGy. It was found that the radiation-induced EPR signal increased linearly with gamma dose for all studied tooth enamel samples, up to about 15 kGy. At higher doses, the dose response curve leveled off. The results revealed that the location of the native signal of camel tooth enamel was similar to that of enamel from human molars at 2.00644, but different from that of enamel from cows and goats. In addition, the peak-to-peak width (ΔH pp) for human and camel molar teeth was similar. It was also found that the response of camel enamel to gamma radiation was 36% lower than that of human enamel. In conclusion, the results indicate the suitability of camel teeth for retrospective gamma dosimetry. 相似文献
144.
Growth and habitat separation in eight cohorts of three species of cyprinids in a subalpine lake 总被引:1,自引:0,他引:1
Veronika Rheinberger Rudolf Hofer Wolfgang Wieser 《Environmental Biology of Fishes》1987,18(3):209-217
Synopsis Distribution and growth of the embryos, larvae and juveniles of Rutilus rutilus (roach), Scardinius erythrophthalmus (rudd) and Leuciscus cephalus (chub) from an oligotrophic subalpine lake in Tyrol, Austria, were studied during the first three to four months after hatching. R. rutilus was the first to spawn, a single cohort hatching around May 23rd. Four cohorts of S. erythrophthalmus hatched between June 19 and August 1. Three cohorts of L. cephalus hatched between July 3 and 25. The length/weight relationship of all species changed at a length of approximately 15–16 mm. R. rutilus, hatching at the lowest temperature, also showed the lowest growth rate during early life (maximum 10.4 per cent fresh body weight day–1). In the other two species relative growth rates up to 20% day–1) were measured. Rudd and chub remained in the shallow littoral during the whole period of observation, whereas roach left the littoral a few weeks after hatching and migrated into deeper water. A subtle shift in vertical distribution was observed for the first cohort of rudd which moved into slightly deeper water when the second cohort made its appearance.To whom correspondence should be addressed 相似文献
145.
V. Andrushchenko Yu Blagoi J. H. van de Sande H. Wieser 《Journal of biomolecular structure & dynamics》2013,31(5):889-906
Abstract Phase transitions were studied of the sodium salt of poly(rA) ?poly(rU) induced by elevated temperature without Ni2+ and with Ni2+ in 0.07 M concentration in D2O (~0.4 [Ni]/[P]). The temperature was varied from 20° C to 90° C. The double-stranded conformation of poly(rA)?poly(rU) was observed at room temperature (20° C—23° C) with and without Ni2+ ions. In the absence of Ni2+ ions, partial double- to triple-strand transition of poly(rA) ?poly(rU) occurred at 58° C, whereas only single-stranded molecules existed at 70° C. While poly(rU) did not display significant helical structure, poly(rA) still maintained some helicity at this temperature. Ni2+ ions significantly stabilized the triple-helical structure. The temperature range of the stable triple-helix was between 45° C and 70° C with maximum stability around 53° C. Triple-to single-stranded transition of poly(rA) ?poly(rU) occurred around 72° C with loss of base stacking in single-stranded molecules. Stacked or aggregated structures of poly(rA) formed around 86° C. Hysteresis took place in the presence of Ni2+ during the reverse transition from the triple-stranded to the double-stranded form upon cooling. Reverse Hoogsteen type of hydrogen-bonding of the third strand in the triplex was suggested to be the most probable model for the triple-helical structure. VCD spectroscopy demonstrated significant advantages over infrared absorption or the related electronic CD spectroscopy. 相似文献
146.
Secreted microvesicular miR‐31 inhibits osteogenic differentiation of mesenchymal stem cells 下载免费PDF全文
Sylvia Weilner Elisabeth Schraml Matthias Wieser Paul Messner Karl Schneider Klemens Wassermann Lucia Micutkova Klaus Fortschegger Andrea B. Maier Rudi Westendorp Heinrich Resch Susanne Wolbank Heinz Redl Pidder Jansen‐Dürr Peter Pietschmann Regina Grillari‐Voglauer Johannes Grillari 《Aging cell》2016,15(4):744-754
Damage to cells and tissues is one of the driving forces of aging and age‐related diseases. Various repair systems are in place to counteract this functional decline. In particular, the property of adult stem cells to self‐renew and differentiate is essential for tissue homeostasis and regeneration. However, their functionality declines with age (Rando, 2006). One organ that is notably affected by the reduced differentiation capacity of stem cells with age is the skeleton. Here, we found that circulating microvesicles impact on the osteogenic differentiation capacity of mesenchymal stem cells in a donor‐age‐dependent way. While searching for factors mediating the inhibitory effect of elderly derived microvesicles on osteogenesis, we identified miR‐31 as a crucial component. We demonstrated that miR‐31 is present at elevated levels in the plasma of elderly and of osteoporosis patients. As a potential source of its secretion, we identified senescent endothelial cells, which are known to increase during aging in vivo (Erusalimsky, 2009). Endothelial miR‐31 is secreted within senescent cell‐derived microvesicles and taken up by mesenchymal stem cells where it inhibits osteogenic differentiation by knocking down its target Frizzled‐3. Therefore, we suggest that microvesicular miR‐31 in the plasma of elderly might play a role in the pathogenesis of age‐related impaired bone formation and that miR‐31 might be a valuable plasma‐based biomarker for aging and for a systemic environment that does not favor cell‐based therapies whenever osteogenesis is a limiting factor. 相似文献
147.
Matthias Hackl Stefan Brunner Klaus Fortschegger Carina Schreiner Lucia Micutkova Christoph Mück Gerhard T. Laschober Günter Lepperdinger Natalie Sampson Peter Berger Dietmar Herndler‐Brandstetter Matthias Wieser Harald Kühnel Alois Strasser Mark Rinnerthaler Michael Breitenbach Michael Mildner Leopold Eckhart Erwin Tschachler Andrea Trost Johann W. Bauer Christine Papak Zlatko Trajanoski Marcel Scheideler Regina Grillari‐Voglauer Beatrix Grubeck‐Loebenstein Pidder Jansen‐Dürr Johannes Grillari 《Aging cell》2010,9(2):291-296
148.
A. Wieser E. Vasilenko E. Aladova P. Fattibene N. Semiochkina M. Smetanin 《Radiation and environmental biophysics》2014,53(2):321-333
In 1945, within the frame of the Uranium Project for the production of nuclear weapons, the Mayak nuclear facilities were constructed at the Lake Irtyash in the Southern Urals, Russia. The nuclear workers of the Mayak Production Association (MPA), who lived in the city of Ozyorsk, are the focus of epidemiological studies for the assessment of health risks due to protracted exposure to ionising radiation. Electron paramagnetic resonance measurements of absorbed dose in tooth enamel have already been used in the past, in an effort to validate occupational external doses that were evaluated in the Mayak Worker Dosimetry System. In the present study, 229 teeth of Ozyorsk citizens not employed at MPA were investigated for the assessment of external background exposure in Ozyorsk. The annually absorbed dose in tooth enamel from natural background radiation was estimated to be (0.7 ± 0.3) mGy. For citizens living in Ozyorsk during the time of routine noble gas releases of the MPA, which peaked in 1953, the average excess absorbed dose in enamel above natural background was (36 ± 29) mGy, which is consistent with the gamma dose obtained by model calculations. In addition, there were indications of possible accidental gaseous MPA releases that affected the population of Ozyorsk, during the early and late MPA operation periods, before 1951 and after 1960. 相似文献
149.
Weghuber J Aichinger MC Brameshuber M Wieser S Ruprecht V Plochberger B Madl J Horner A Reipert S Lohner K Henics T Schütz GJ 《Biochimica et biophysica acta》2011,1808(10):2581-2590
Cationic antimicrobial peptides (CAMPs) selectively target bacterial membranes by electrostatic interactions with negatively charged lipids. It turned out that for inhibition of microbial growth a high CAMP membrane concentration is required, which can be realized by the incorporation of hydrophobic groups within the peptide. Increasing hydrophobicity, however, reduces the CAMP selectivity for bacterial over eukaryotic host membranes, thereby causing the risk of detrimental side-effects. In this study we addressed how cationic amphipathic peptides-in particular a CAMP with Lysine-Leucine-Lysine repeats (termed KLK)-affect the localization and dynamics of molecules in eukaryotic membranes. We found KLK to selectively inhibit the endocytosis of a subgroup of membrane proteins and lipids by electrostatically interacting with negatively charged sialic acid moieties. Ultrastructural characterization revealed the formation of membrane invaginations representing fission or fusion intermediates, in which the sialylated proteins and lipids were immobilized. Experiments on structurally different cationic amphipathic peptides (KLK, 6-MO-LF11-322 and NK14-2) indicated a cooperation of electrostatic and hydrophobic forces that selectively arrest sialylated membrane constituents. 相似文献
150.
Loetscher Y Wieser A Lengefeld J Kaiser P Schubert S Heikenwalder M Hardt WD Stecher B 《PloS one》2012,7(4):e34812