全文获取类型
收费全文 | 143篇 |
免费 | 6篇 |
专业分类
149篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有149条查询结果,搜索用时 13 毫秒
1.
The rate of electron transfer through Photosystem I (reduced 2,6-dichlorophenol indophenol (DCIPH2 → methylviologen) in a low-salt thylakoid suspension is inhibited by Mg2+ both under light-limited and the light-saturated conditions, the magnitude of inhibition being the same. The 2,6-dichlorophenol indophenol (DCIP) concentration dependence of the light-saturated rate in the presence and in the absence of Mg2+ shows that the overall rate constant of the photoreaction is not altered by Mg2+. With N,N,N′,N′-tetramethyl-p-phenylenediamine or 2,3,5,6-tetramethylphenylenediamine as electron donor only the light-limited rate, not the light-saturated rate, is inhibited by Mg2+ and the magnitude of inhibition is the same as with DCIP as donor. The results are interpreted in terms of heterogeneous Photosystem I, consisting of two types, PS I-A and PS I-B, where PS I-A is involved in cation-regulation of excitation energy distribution and becomes unavailable for DCIPH2 → methyl viologen photoelectron transfer in the presence of Mg2+. 相似文献
2.
K S Ramanujam S Seetharam B Seetharam 《Biochemical and biophysical research communications》1991,179(1):543-550
Opossum kidney epithelial cells synthesize and secrete two Cobalamin (Cbl) binding proteins of Mr 66,000 and 43,000. When grown on culture inserts, the apical medium contained both these proteins while the basolateral medium contained only the 43 kDa Cbl binder. Colchicine, a microtubule disruptive drug, increased two fold the apical but not the basolateral secretion of the Cbl binding proteins. Although the opossum Cbl binders did not cross react with anti-serum raised to Cbl binders from other species, the identity based on Cbl binding and size suggest that the 66 kDa and 43 kDa proteins are haptocorrin and transcobalamin II. 相似文献
3.
Renal brush border membrane bound intrinsic factor 总被引:1,自引:0,他引:1
K S Ramanujam S Seetharam M Ramasamy B Seetharam 《Biochimica et biophysica acta》1990,1030(1):157-164
A highly active receptor for intrinsic factor (IF)-cobalamin (Cbl) complex has been detected and reported in mammalian kidney earlier (Seetharam, B., et al. (1988) J. Biol. Chem. 263, 4443-4449). The physiological role of this receptor in normal Cbl homeostasis is not known. In addition to binding of exogenously added IF-[57Co]Cbl, the renal apical membranes contain endogenous IF or IF-Cbl. Washing with pH 5/EDTA buffer enhanced the binding of exogenously added IF-[57Co]Cbl to renal apical but not basolateral membranes. The pH 5/EDTA extract from renal apical membranes bound [57Co]Cbl. The complex also bound to rat ileal brush border membrane and promoted ileal transport of [57Co]Cbl. On immunoblots using monospecific antiserum to IF a 62 kDa protein was identified in renal and intestinal apical membranes, serum and in tissue extracts of unperfused rat liver, kidney and heart. The 62 kDa band was eliminated from the renal apical membranes following pH 5/EDTA wash. Rat urine demonstrated unsaturated [57Co]Cbl binding (0.2 to 0.4 pmol/day) of which only 30-40% was immunoprecipitated with anti IF and could be identified on immunoblots. The identification of IF in rat renal apical membranes (160-200 ng/mg protein) and secretion of only traces of IF in urine suggest that the renal IF-Cbl receptor may play a role in sequestering IF/IF-Cbl and prevent urinary loss of Cbl. 相似文献
4.
E. coli nucleoside diphosphate kinase (EcoNDK) is an important cellular enzyme required to maintain balanced nucleotide pools in the cells. Recently, it was reported that EcoNDK is also a multifunctional base excision repair enzyme, possessing uracil-DNA glycosylase (UDG) and AP-DNA processing activities. We investigated for the presence of such activities in M. tuberculosis NDK (MtuNDK), which shares 45.2% identity, and 52.6% similarity with EcoNDK. In contrast to the robust uracil excision activity reported for EcoNDK, MtuNDK preparation exhibited very poor excision of uracil from DNA. However, this activity was undetectable when MtuNDK was purified from an ung(-) strain of E. coli, or when the assays were performed in the presence of extremely low amounts of a highly specific proteinaceous inhibitor, Ugi which forms an extremely tight complex with the host Ung (UDG), showing that MtuNDK preparation was contaminated with UDG. Reinvestigation of uracil processing activity of EcoNDK, showed that even this protein lacked UDG activity. All preparations of NDK were shown to be active by their autophosphorylation activity. Ugi neither displayed a physical interaction with EcoNDK nor did it affect autophosphorylation of NDKs. Further, neither of the NDK preparations processed the AP-DNA generated by UDG treatment of the uracil containing DNA duplexes. However, partially purified preparations of NDK did process such DNA substrates. 相似文献
5.
Yokoi K Egger NG Ramanujam VM Alcock NW Dayal HH Penland JG Sandstead HH 《American journal of physiology. Endocrinology and metabolism》2003,285(5):E1010-E1020
The objective of this study was to measure relationships between plasma zinc (Zn) concentrations and Zn kinetic parameters and to measure relationships of Zn status with taste acuity, food frequency, and hair Zn in humans. The subjects were 33 premenopausal women not taking oral contraceptives and dietary supplements containing iron and Zn. Main outcomes were plasma Zn concentrations, Zn kinetic parameters based on the three-compartment mammillary model using 67Zn as a tracer, electrical taste detection thresholds, and food frequencies. Lower plasma Zn was significantly (P < 0.01) associated with smaller sizes of the central and the lesser peripheral Zn pools, faster disappearance of tracer from plasma, and higher transfer rate constants from the lesser peripheral pool to the central pool and from the central pool to the greater peripheral pool. The break points in the plasma Zn-Zn kinetics relationship were found between 9.94 and 11.5 micromol/l plasma Zn. Smaller size of the lesser peripheral pool was associated with lower frequency of beef consumption and higher frequency of bran breakfast cereal consumption. Hypozincemic women with plasma Zn <10.7 micromol/l or 700 ng/ml had decreased thresholds of electrical stimulation for gustatory nerves. Our results based on Zn kinetics support the conventional cutoff value of plasma Zn (10.7 micromol/l or 700 ng/ml) between normal and low Zn status. 相似文献
6.
Christopher T. Lam Marlee S. Krieger Jennifer E. Gallagher Betsy Asma Lisa C. Muasher John W. Schmitt Nimmi Ramanujam 《PloS one》2015,10(9)
Introduction
Current guidelines by WHO for cervical cancer screening in low- and middle-income countries involves visual inspection with acetic acid (VIA) of the cervix, followed by treatment during the same visit or a subsequent visit with cryotherapy if a suspicious lesion is found. Implementation of these guidelines is hampered by a lack of: trained health workers, reliable technology, and access to screening facilities. A low cost ultra-portable Point of Care Tampon based digital colposcope (POCkeT Colposcope) for use at the community level setting, which has the unique form factor of a tampon, can be inserted into the vagina to capture images of the cervix, which are on par with that of a state of the art colposcope, at a fraction of the cost. A repository of images to be compiled that can be used to empower front line workers to become more effective through virtual dynamic training. By task shifting to the community setting, this technology could potentially provide significantly greater cervical screening access to where the most vulnerable women live. The POCkeT Colposcope’s concentric LED ring provides comparable white and green field illumination at a fraction of the electrical power required in commercial colposcopes. Evaluation with standard optical imaging targets to assess the POCkeT Colposcope against the state of the art digital colposcope and other VIAM technologies.Results
Our POCkeT Colposcope has comparable resolving power, color reproduction accuracy, minimal lens distortion, and illumination when compared to commercially available colposcopes. In vitro and pilot in vivo imaging results are promising with our POCkeT Colposcope capturing comparable quality images to commercial systems.Conclusion
The POCkeT Colposcope is capable of capturing images suitable for cervical lesion analysis. Our portable low cost system could potentially increase access to cervical cancer screening in limited resource settings through task shifting to community health workers. 相似文献7.
Brandon S. Nichols Christine E. Schindler Jonathon Q. Brown Lee G. Wilke Christine S. Mulvey Marlee S. Krieger Jennifer Gallagher Joseph Geradts Rachel A. Greenup Jesko A. Von Windheim Nirmala Ramanujam 《PloS one》2015,10(6)
In an ongoing effort to address the clear clinical unmet needs surrounding breast conserving surgery (BCS), our group has developed a next-generation multiplexed optical-fiber-based tool to assess breast tumor margin status during initial surgeries. Specifically detailed in this work is the performance and clinical validation of a research-grade intra-operative tool for margin assessment based on diffuse optical spectroscopy. Previous work published by our group has illustrated the proof-of-concept generations of this device; here we incorporate a highly optimized quantitative diffuse reflectance imaging (QDRI) system utilizing a wide-field (imaging area = 17cm2) 49-channel multiplexed fiber optic probe, a custom raster-scanning imaging platform, a custom dual-channel white LED source, and an astronomy grade imaging CCD and spectrograph. The system signal to noise ratio (SNR) was found to be greater than 40dB for all channels. Optical property estimation error was found to be less than 10%, on average, over a wide range of absorption (μa = 0–8.9cm-1) and scattering (μs’ = 7.0–9.7cm-1) coefficients. Very low inter-channel and CCD crosstalk was observed (2% max) when used on turbid media (including breast tissue). A raster-scanning mechanism was developed to achieve sub-pixel resolution and was found to be optimally performed at an upsample factor of 8, affording 0.75mm spatially resolved diffuse reflectance images (λ = 450–600nm) of an entire margin (area = 17cm2) in 13.8 minutes (1.23cm2/min). Moreover, controlled pressure application at the probe-tissue interface afforded by the imaging platform reduces repeated scan variability, providing <1% variation across repeated scans of clinical specimens. We demonstrate the clinical utility of this device through a pilot 20-patient study of high-resolution optical parameter maps of the ratio of the β-carotene concentration to the reduced scattering coefficient. An empirical cumulative distribution function (eCDF) analysis is used to reduce optical property maps to quantitative distributions representing the morphological landscape of breast tumor margins. The optimizations presented in this work provide an avenue to rapidly survey large tissue areas on intra-operative time scales with improved sensitivity to regions of focal disease that may otherwise be overlooked. 相似文献
8.
Fadee G Mondalek Sivapriya Ponnurangam Janita Govind Courtney Houchen Shrikant Anant Panayotis Pantazis Rama P Ramanujam 《Journal of nanobiotechnology》2010,8(1):17
Background
The redox dye, DCPIP, has recently shown to exhibit anti-melanoma activity in vitro and in vivo. On the other hand, there is increasing evidence that synthetic nanoparticles can serve as highly efficient carriers of drugs and vaccines for treatment of various diseases. These nanoparticles have shown to serve as potent tools that can increase the bioavailability of the drug/vaccine by facilitating absorption or conferring sustained and improved release. Here, we describe results on the effects of free- and nanoparticle-enclosed DCPIP as anti-angiogenesis and anti-inflammation agents in a human colon cancer HCT116 cell line in vitro, and in induced angiogenesis in ovo. 相似文献9.
Vani Pande Nivedita Mitra Saket Rahul Bagde Ramanujam Srinivasan Pananghat Gayathri 《The Journal of cell biology》2022,221(5)
MreB, the bacterial ancestor of eukaryotic actin, is responsible for shape in most rod-shaped bacteria. Despite belonging to the actin family, the relevance of nucleotide-driven polymerization dynamics for MreB function is unclear. Here, we provide insights into the effect of nucleotide state on membrane binding of Spiroplasma citri MreB5 (ScMreB5). Filaments of ScMreB5WT and an ATPase-deficient mutant, ScMreB5E134A, assemble independently of the nucleotide state. However, capture of the filament dynamics revealed that efficient filament formation and organization through lateral interactions are affected in ScMreB5E134A. Hence, the catalytic glutamate functions as a switch, (a) by sensing the ATP-bound state for filament assembly and (b) by assisting hydrolysis, thereby potentially triggering disassembly, as observed in other actins. Glu134 mutation and the bound nucleotide exhibit an allosteric effect on membrane binding, as observed from the differential liposome binding. We suggest that the conserved ATP-dependent polymerization and disassembly upon ATP hydrolysis among actins has been repurposed in MreBs for modulating filament organization on the membrane. 相似文献
10.
Supply of aqueous solution of triadimefon (20 mg dm−3) to unstressed green gram plants increased the contents of soluble proteins, amino acids, nitrate and nitrite, and the activity
of nitrate reductase in the leaves and nitrate reductase in nodules. The nitrogenase activity in nodules and roots was also
increased. Number and fresh mass of nodules and their nitrate and nitrite contents were also higher than those of the controls.
In contrast, the UV-B stress (12.2 kJ m−2 d−1) suppressed nodulation and nitrogen metabolism in leaves and roots compared to plants under natural UV-B (10 kJ m−2 d−1). Triadimefon-treated plants did not show such severe inhibitions after exposure to elevated UV-B. Thus triadimefon increased
their tolerance to UV-B stress. 相似文献