全文获取类型
收费全文 | 704篇 |
免费 | 79篇 |
专业分类
783篇 |
出版年
2016年 | 6篇 |
2015年 | 15篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 20篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 17篇 |
2007年 | 28篇 |
2006年 | 21篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 20篇 |
2001年 | 20篇 |
2000年 | 14篇 |
1999年 | 20篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1993年 | 14篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 24篇 |
1985年 | 14篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1975年 | 16篇 |
1974年 | 23篇 |
1973年 | 6篇 |
1972年 | 17篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 8篇 |
1968年 | 6篇 |
1967年 | 7篇 |
1966年 | 6篇 |
排序方式: 共有783条查询结果,搜索用时 0 毫秒
41.
From genomic libraries of the purple non-sulfur bacteria Rhodospirillum rubrum Ha and Rhodobacter sphaeroides ATCC 17023 in the broad-host range cosmid pVK100, we cloned a 15- and a 14-kbp HindIII restriction fragment, respectively. Each of these fragments restored the ability to accumulate poly(3-hydroxybutyrate) (PHB), in the PHB-negative mutant Alcaligenes eutrophus PHB-4. These hybrid cosmids also complemented PHB-negative mutants derived from wild-type R. rubrum or R. sphaeroides. Both fragments hybridized with the PHB synthase structural gene of A. eutrophus H16 and conferred the ability to express PHB synthase activity. Only the 15-kbp HindIII fragment from R. rubrum conferred on the mutant PHB-4 the ability to form large PHB granules (length up to 3.5 microns). 相似文献
42.
43.
44.
Premature expression of cyclin B sensitizes human HT1080 cells to caffeine-induced premature mitosis
Eukaryotic cells do not normally initiate mitosis when DNA replication is blocked. This cell cycle checkpoint can be bypassed in some cells, however, by treatment with caffeine and certain other chemicals. Although S-phase arrested hamster cells undergo mitosis-specific events such as premature chromosome condensation (PCC) and nuclear envelope disassembly when exposed to caffeine, human cells show little response under the same conditions. To further investigate the molecular basis of this cell type specificity, a panel of hamster/human whole cell hybrids was created. The frequency of caffeine-induced PCC and the level of cyclin B-associated H1 kinase activity in the various hybrids were directly correlated with the extent of cyclin B synthesis during S-phase arrest. To determine whether expression of cyclin B alone could sensitize human cells to caffeine, cyclin B1 was transiently overexpressed in S-phase arrested HT1080 cells. The transfected cell population displayed a 5-fold increase in the frequency of caffeine-induced PCC when compared with normal HT1080 cells, roughly equivalent to the frequency of cells expressing exogenous epitope-tagged cyclin B1. In addition, immunofluorescent microscopy showed that individual cells overexpressing cyclin B1 during S phase arrest underwent PCC when exposed to caffeine. These results provide direct evidence that premature expression of cyclin B1 can make cells more vulnerable to chemically-induced uncoupling of mitosis from the completion of DNA replication. © 1995 Wiley-Liss, Inc. 相似文献
45.
46.
47.
Heme histidine ligands within gp91(phox) modulate proton conduction by the phagocyte NADPH oxidase 总被引:4,自引:0,他引:4
Maturana A Arnaudeau S Ryser S Banfi B Hossle JP Schlegel W Krause KH Demaurex N 《The Journal of biological chemistry》2001,276(32):30277-30284
The membrane subunit of the phagocyte NADPH oxidase, gp91(phox), possesses a H(+) channel motif formed by membrane-spanning histidines postulated to coordinate the two heme groups forming the redox center of the flavocytochrome. To study the role of heme-binding histidines on proton conduction, we stably expressed the gp91(phox) cytochrome in human embryonic kidney 293 cells and measured proton currents with the patch clamp technique. Similar to its shorter homologue, NADPH oxidase homologue 1, which is predicted not to bind heme, gp91(phox) generated voltage-activated, pH-dependent, H(+)-selective currents that were reversibly blocked by Zn(2+). The gp91(phox) currents, however, activated faster, deactivated more slowly, and were markedly affected by the inhibition of heme synthesis. Upon heme removal, the currents had larger amplitude, activated faster and at lower voltages, and became sensitive to the histidine reagent diethylpyrocarbonate. Mutation of the His-115 residue to leucine abolished both the gp91(phox) characteristic 558-nm absorbance peak and voltage-activated currents, indicating that His-115 is involved in both heme ligation and proton conduction. These results indicate that the gp91(phox) proton channel is activated upon release of heme from its His-115 ligand. During activation of the oxidase complex, changes in heme coordination within the cytochrome might increase the mobility of histidine ligands, thereby coupling electron and proton transport. 相似文献
48.
U. Schmidt P. Schlegel H. Schweizer G. Neuweiler 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(1):45-51
1. | Within the tonotopic organization of the inferior colliculus two frequency ranges are well represented: a frequency range within that of the echolocation signals from 50 to 100 kHz, and a frequency band below that of the echolocation sounds, from 10 to 35 kHz. The frequency range between these two bands, from about 40 to 50 kHz is distinctly underrepresented (Fig. 3B). |
2. | Units with BFs in the lower frequency range (10–25 kHz) were most sensitive with thresholds of -5 to -11 dB SPL, and units with BFs within the frequency range of the echolocation signals had minimal thresholds around 0 dB SPL (Fig. 1). |
3. | In the medial part of the rostral inferior colliculus units were encountered which preferentially or exclusively responded to noise stimuli. — Seven neurons were found which were only excited by human breathing noises and not by pure tones, frequency modulated signals or various noise bands. These neurons were considered as a subspeciality of the larger sample of noise-sensitive neurons. — The maximal auditory sensitivity in the frequency range below that of echolocation, and the conspicuous existence of noise and breathing-noise sensitive units in the inferior colliculus are discussed in context with the foraging behavior of vampire bats. |
49.
Daniela Klein Alexandra Mendes-Madeira Patrice Schlegel Fabienne Rolling Birgit Lorenz Silke Haverkamp Knut Stieger 《PloS one》2014,9(1)
Mutations in the RPE65 gene are associated with autosomal recessive early onset severe retinal dystrophy. Morphological and functional studies indicate early and dramatic loss of rod photoreceptors and early loss of S-cone function, while L and M cones remain initially functional. The Swedish Briard dog is a naturally occurring animal model for this disease. Detailed information about rod and cone reaction to RPE65 deficiency in this model with regard to their location within the retina remains limited. The aim of this study was to analyze morphological parameters of cone and rod viability in young adult RPE65 deficient dogs in different parts of the retina in order to shed light on local disparities in this disease. In retinae of affected dogs, sprouting of rod bipolar cell dendrites and horizontal cell processes was dramatically increased in the inferior peripheral part of affected retinae, while central inferior and both superior parts did not display significantly increased sprouting. This observation was correlated with photoreceptor cell layer thickness. Interestingly, while L/M cone opsin expression was uniformly reduced both in the superior and inferior part of the retina, S-cone opsin expression loss was less severe in the inferior part of the retina. In summary, in retinae of young adult RPE65 deficient dogs, the degree of rod bipolar and horizontal cell sprouting as well as of S-cone opsin expression depends on the location. As the human retinal pigment epithelium (RPE) is pigmented similar to the RPE in the inferior part of the canine retina, and the kinetics of photoreceptor degeneration in humans seems to be similar to what has been observed in the inferior peripheral retina in dogs, this area should be studied in future gene therapy experiments in this model. 相似文献
50.