全文获取类型
收费全文 | 373篇 |
免费 | 51篇 |
专业分类
424篇 |
出版年
2023年 | 2篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 1篇 |
2016年 | 17篇 |
2015年 | 20篇 |
2014年 | 18篇 |
2013年 | 26篇 |
2012年 | 27篇 |
2011年 | 33篇 |
2010年 | 15篇 |
2009年 | 13篇 |
2008年 | 28篇 |
2007年 | 34篇 |
2006年 | 29篇 |
2005年 | 19篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有424条查询结果,搜索用时 15 毫秒
1.
A new fluorescence method to measure viscosity in cell cytosol [Fushimi, K., & Verkman, A. S. (1991) J. Cell Biol. 112, 719-725] has been applied to determine fluid-phase viscosity in sea urchin eggs. Freshly harvested eggs from Lytechinus pictus were loaded with the dyes 2,7-bis(2-carboxyethyl)-5-(and-6-)carboxyfluorescein (BCECF), 6-carboxyfluorescein (6CF), fluorescein, or calcein. Fluorescence lifetimes and anisotropy decay were measured in single eggs by multiharmonic, frequency-domain microfluorometry using a 1-2-micron focused laser spot and 25x air objective. In calibration solutions consisting of glycerol in pH 8 buffered sea water, probe lifetime was single exponential and probe rotation was isotropic with a single correlation time which increased linearly with viscosity in the range 1-3.6 cP. In eggs at 22 degrees C, there were single lifetimes (in nanoseconds) of 3.6 (BCECF), 3.4 (6CF), 3.2 (fluorescein), and 3.3 (calcein). Probe rotation in eggs had two components, a fast component (in picoseconds, mean +/- SE, 10-18 eggs) of 568 +/- 39 (BCECF), 311 +/- 21 (6CF), 313 +/- 15 (fluorescein), and 516 +/- 44 (calcein) and a slow component of 10-40 ns. The fractional amplitude of the fast component, corresponding to unbound dye, was 0.72-0.81. Apparent viscosities of fluid-phase cytoplasm (centipoises) given by the four different probes were in good agreement: 2.3 +/- 0.2 (BCECF), 2.1 +/- 0.1 (6CF), 2.5 +/- 0.1 (fluorescein), and 2.3 +/- 0.2 (calcein). The viscosity in cytosol of sea urchin eggs (2.1-2.5 cP) is thus relatively low, yet significantly greater than that of water (1 cP) or cytosol in cultured fibroblasts (1.2-1.4 cP).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
2.
Fluorescence resonance energy transfer (FRET) microscopy imaging of live cell protein localizations 总被引:13,自引:0,他引:13
The current advances in fluorescence microscopy, coupled with the development of new fluorescent probes, make fluorescence resonance energy transfer (FRET) a powerful technique for studying molecular interactions inside living cells with improved spatial (angstrom) and temporal (nanosecond) resolution, distance range, and sensitivity and a broader range of biological applications. 相似文献
3.
4.
Periasamy Ashok Kumar Vijayaraghavan Kannan 《Nucleosides, nucleotides & nucleic acids》2013,32(1):20-30
An extracellular nuclease from Bacillus firmus VKPACU-1 was multifunctional enzyme, this nuclease hydrolyzed poly U rapidly and more preferentially than the other homopolyribonucleotides. Hydrolysis of RNA this enzyme released mononucleotides in the order 5′UMP > 5′AMP > 5′GMP where as in hydrolysis of DNA the mononucleotides in the order of 5′dAMP > 5′dGMP > 5′dTMP and oligonucleotides. Uridylic linkages in RNA and adenylic linkages in DNA were preferentially cleaved by the nuclease. Nuclease produced oligonucleotides having only 3’ hydroxyl and 5’ phosphate termini. Present nuclease hydrolyzed RNA and DNA released oligonucleotides as major end products and mononucleotides, suggesting an endo mode of action. 相似文献
5.
Harihar Milaganur Mohan Boning Yang Nicole A. Dean Malini Raghavan 《The Journal of biological chemistry》2020,295(49):16754
α1-antitrypsin (AAT) regulates the activity of multiple proteases in the lungs and liver. A mutant of AAT (E342K) called ATZ forms polymers that are present at only low levels in the serum and induce intracellular protein inclusions, causing lung emphysema and liver cirrhosis. An understanding of factors that can reduce the intracellular accumulation of ATZ is of great interest. We now show that calreticulin (CRT), an endoplasmic reticulum (ER) glycoprotein chaperone, promotes the secretory trafficking of ATZ, enhancing the media:cell ratio. This effect is more pronounced for ATZ than with AAT and is only partially dependent on the glycan-binding site of CRT, which is generally relevant to substrate recruitment and folding by CRT. The CRT-related chaperone calnexin does not enhance ATZ secretory trafficking, despite the higher cellular abundance of calnexin-ATZ complexes. CRT deficiency alters the distributions of ATZ-ER chaperone complexes, increasing ATZ-BiP binding and inclusion body formation and reducing ATZ interactions with components required for ER-Golgi trafficking, coincident with reduced levels of the protein transport protein Sec31A in CRT-deficient cells. These findings indicate a novel role for CRT in promoting the secretory trafficking of a protein that forms polymers and large intracellular inclusions. Inefficient secretory trafficking of ATZ in the absence of CRT is coincident with enhanced accumulation of ER-derived ATZ inclusion bodies. Further understanding of the factors that control the secretory trafficking of ATZ and their regulation by CRT could lead to new therapies for lung and liver diseases linked to AAT deficiency. 相似文献
6.
Jennifer E. Sanner Lorraine Frazier Malini Udtha 《The Yale journal of biology and medicine》2013,86(1):5-13
Platelet serotonin has been associated with depression and coronary artery
disease. Understanding the association between platelet serotonin and depressive
symptoms during acute coronary syndrome (ACS) may explain some of the ACS events
seen in depressed individuals. The objectives were to evaluate whether levels of
platelet serotonin during an ACS event differ between individuals who screen
positive or negative for depressive symptoms and to determine if a linear
relationship exists. In this cross-sectional study, data were collected on 51
patients with ACS. Multiple linear regression models were examined. Platelet
serotonin levels were not significantly different between the depressed and
non-depressed groups (β = -4.093 and p = .293); a linear relationship was not
found (β = -.254 and p = .250). In conclusion, a relationship between platelet
serotonin and depressive symptoms was not found. It remains unclear if an
association exists between platelet serotonin levels and depressive symptoms
during hospitalization for ACS. 相似文献
7.
Amanda P. Waller Michael George Anuradha Kalyanasundaram Chen Kang Muthu Periasamy Keli Hu Véronique A. Lacombe 《生物化学与生物物理学报:疾病的分子基础》2013,1832(1):121-127
Glucose uptake from the bloodstream is the rate-limiting step in whole body glucose utilization, and is regulated by a family of membrane proteins called glucose transporters (GLUTs). Although GLUT4 is the predominant isoform in insulin-sensitive tissues, there is recent evidence that GLUT12 could be a novel second insulin-sensitive GLUT. However, its physiological role in the heart is not elucidated and the regulation of insulin-stimulated myocardial GLUT12 translocation is unknown. In addition, the role of GLUT12 has not been investigated in the diabetic myocardium. Thus, we hypothesized that, as for GLUT4, insulin regulates GLUT12 translocation to the myocardial cell surface, which is impaired during diabetes. Active cell surface GLUT (-4 and -12) content was quantified (before and after insulin stimulation) by a biotinylated photolabeled assay in both intact perfused myocardium and isolated cardiac myocytes of healthy and type 1 diabetic rodents. GLUT localization was confirmed by immunofluorescent confocal microscopy, and total GLUT protein expression was measured by Western blotting. Insulin stimulation increased translocation of GLUT-4, but not -12, in the healthy myocardium. Total GLUT4 content of the heart was decreased during diabetes, while there was no difference in total GLUT12. Active cell surface GLUT12 content was increased in the diabetic myocardium, potentially as a compensatory mechanism for the observed downregulation of GLUT4. Collectively, our data suggest that, in contrast to GLUT4, insulin does not mediate GLUT12 translocation, which may function as a basal GLUT located primarily at the cell surface in the myocardium. 相似文献
8.
Seyedeh Maryam Banihashemian Vengadesh Periasamy Goh Boon Tong Saadah Abdul Rahman 《PloS one》2016,11(3)
Studying the effect of a magnetic field on oligonucleotide DNA can provide a novel DNA manipulation technique for potential application in bioengineering and medicine. In this work, the optical and electrochemical response of a 100 bases oligonucleotides DNA, cytosine-guanine (CG100), is investigated via exposure to different magnetic fields (250, 500, 750, and 1000 mT). As a result of the optical response of CG100 to the magnetic field, the ultra-violet-visible spectrum indicated a slight variation in the band gap of CG100 of about 0.3 eV. Raman spectroscopy showed a significant deviation in hydrogen and phosphate bonds’ vibration after exposure to the magnetic field. Oligonucleotide DNA mobility was investigated in the external electric field using the gel electrophoresis technique, which revealed a small decrease in the migration of CG100 after exposure to the magnetic field. 相似文献
9.
10.
The biochemical aspects of the initiation of DNA replication in Mycobacterium avium are unknown. As a first step towards understanding this process, M. avium DnaA protein, the counterpart of Escherichia coli replication initiator protein, was overproduced in E. coli with an N-terminal histidine tag and purified to homogeneity on a nickel affinity column. The recombinant DnaA protein bound both ATP and ADP with high affinity and showed a weak ATPase activity. ADP, following the hydrolysis of ATP, remained bound to the protein strongly and the exchange of ATP for bound ADP was found to be weak. Acidic phospholipids such as phosphatidylinositol, phosphatidylglycerol, and cardiolipin, promoted the dissociation of ADP from the DnaA protein, whereas the neutral phospholipid, phosphatidylethanolamine, did not. The phospholipid promoted dissociation of ADP from DnaA protein was stimulated in the presence of the M. avium origin of replication. We suggest that the initiation of DNA replication in M. avium involves an interplay among DnaA, adenine nucleotides and phospholipids. 相似文献