全文获取类型
收费全文 | 270篇 |
免费 | 17篇 |
国内免费 | 4篇 |
专业分类
291篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 11篇 |
2012年 | 17篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 7篇 |
2007年 | 17篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2001年 | 8篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 6篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1965年 | 4篇 |
1963年 | 3篇 |
1961年 | 2篇 |
1954年 | 4篇 |
1950年 | 3篇 |
排序方式: 共有291条查询结果,搜索用时 0 毫秒
1.
Wolffia arrhiza (L.) Wimm. was grown axenically in the chemostat under white luminescent light (photon fluence rate 23 ujnol m-2 s-1) and phosphate or magnesium limitation (0.075 and 0.01 jxmol 1-1, respectively). Aliquots (1 g fresh mass) were taken from the continuous cultures and were irradiated for 1 h with either
white light (control) or monochromatic blue (453 nm) or red (654 nm) light. The amount of [5-3H]-uridine incorporated into cytosolic and chloroplastic rRNAs during these exposures was estimated and following results
were obtained: In phosphate limited plants rod light considerably reduced and blue light slightly increased label incorporation
as compared with the control. Moreover, in red light, chloroplast incorporation is relatively more slowed down than that in
the cytosolic compartment (34 % as compared to 59 % of the control). In blue light the enhancement is approximately equal
in both compartments. In magnesium limited plants incorporation under both blue and red light is moderately slower as compared
with the control. In both cases also the retardation is slightly greater in the chloroplast than in the cytoplasm. The results
suggest that rRNA metabolism is controlled by light quality as well as by mineral nutrition. 相似文献
2.
Local anesthetic-induced inhibition of collagen secretion in cultured cells under conditions where microtubules are not depolymerized by these agents 总被引:4,自引:0,他引:4 下载免费PDF全文
Tertiary amine local anesthetics previously have been shown to influence some microtubule-dependent cellular functions. Since several cell secretion processes, including secretion of collagen, have been shown to be inhibited by microtubule-disrupting drugs such as colchicine, we determined whether local anesthetics affect collagen secretion. Six local anesthetics inhibited collagen and non-collagen protein secretion (up to 98%) into the extracellular medium of 3T3 cells and human fibroblasts, an effect apparently independent of influences on proline transport and total protein synthesis. A combination of colchicine and cytochalasin B did not duplicate the effects of local anesthetics. The effects of subsaturating concentrations of colchicine and procaine on secretion were additive, suggesting that both drugs act on the secretory pathway at the level of microtubules, but other effects of the two types of drugs were strikingly different. In comparing the mechanisms of action of colchicine and local anesthetics, it was seen that, in contrast to colchicine, radioactive procaine and lidocaine were slowly transported into 3T3 cells, did not bind to the tubulin-containing TCA-insoluble fraction, and did not bind to purified tubulin in vitro. The fraction of cellular tubulin present as microtubules (47% in normal cells) was determined by measuring tubulin in stabilized, sedimentable microtubules compared to total tubulin, using a [3H]colchicine binding assay. Pretreatment of cells in the cold or with colchicine led to depolymerization of microtubules, but pretreatment with five local anesthetics tested did not. Therefore, in contrast to colchicine, local anesthetics in concentrations that inhibit secretion do not directly interact with or depolymerize microtubules. These drugs, however, do affect a microtubule-dependent process and may do so by detaching the microtubular system from the cell membrane. 相似文献
3.
Leaf tissues of Zea mays were examined with a transmission electron microscope and a high-voltage electron microscope. Tubular extensions (invaginations) of the plasmalemma were found in vascular parenchyma cells and thick-walled, lateformed sieve elements of intermediate and small veins, and in epidermal, mesophyll, and sheath cells of all leaves examined. No continuity seems to exist between the tubules and other cellular membranes. 相似文献
4.
M von Eichhorn 《Gegenbaurs morphologisches Jahrbuch》1990,136(1):127-134
Artery loops at the root exit zones of cerebral nerves are regarded as causes of certain diseases, e.g. trigeminal neuralgia or hemifacial spasm. The factors, which may cause such loops and displacements of arteries, however, are still not known sufficiently. In order to find out more about such causes, 60 corpses were examined. We recorded the variations in the positions of vertebral and basilar arteries and correlated them with the respective age at the time of death. We found that those showing atypical artery positions and loops were generally of older age. We further examined possible influences of blood flow factors on variations of artery positions. Our sample indicated such influence of flow factors on displacements of basilar artery, but they seemed to be of lesser importance than the effect of ageing. 相似文献
5.
6.
7.
Protein Phosphatase type 2A (PP2A) represents a family of holoenzyme complexes with diverse biological activities. Specific holoenzyme complexes are thought to be deregulated during oncogenic transformation and oncogene-induced signaling. Since most studies on the role of this phosphatase family have relied on the use of generic PP2A inhibitors, the contribution of individual PP2A holoenzyme complexes in PP2A-controlled signaling pathways is largely unclear. To gain insight into this, we have constructed a set of shRNA vectors targeting the individual PP2A regulatory subunits for suppression by RNA interference. Here, we identify PR55gamma and PR55delta as inhibitors of c-Jun NH(2)-terminal kinase (JNK) activation by UV irradiation. We show that PR55gamma binds c-SRC and modulates the phosphorylation of serine 12 of c-SRC, a residue we demonstrate to be required for JNK activation by c-SRC. We also find that the physical interaction between PR55gamma and c-SRC is sensitive to UV irradiation. Our data reveal a novel mechanism of c-SRC regulation whereby in response to stress c-SRC activity is regulated, at least in part, through loss of the interaction with its inhibitor, PR55gamma. 相似文献
8.
9.
Renate Reiss Julian Ihssen Michael Richter Eric Eichhorn Boris Schilling Linda Th?ny-Meyer 《PloS one》2013,8(6)
Laccases (EC 1.10.3.2) are multi-copper oxidases that catalyse the one-electron oxidation of a broad range of compounds including substituted phenols, arylamines and aromatic thiols to the corresponding radicals. Owing to their broad substrate range, copper-containing laccases are versatile biocatalysts, capable of oxidizing numerous natural and non-natural industry-relevant compounds, with water as the sole by-product. In the present study, 10 of the 11 multi-copper oxidases, hitherto considered to be laccases, from fungi, plant and bacterial origin were compared. A substrate screen of 91 natural and non-natural compounds was recorded and revealed a fairly broad but distinctive substrate spectrum amongst the enzymes. Even though the enzymes share conserved active site residues we found that the substrate ranges of the individual enzymes varied considerably. The EC classification is based on the type of chemical reaction performed and the actual name of the enzyme often refers to the physiological substrate. However, for the enzymes studied in this work such classification is not feasible, even more so as their prime substrates or natural functions are mainly unknown. The classification of multi-copper oxidases assigned as laccases remains a challenge. For the sake of simplicity we propose to introduce the term “laccase-like multi-copper oxidase” (LMCO) in addition to the term laccase that we use exclusively for the enzyme originally identified from the sap of the lacquer tree Rhus vernicifera. 相似文献
10.