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61.
The teleost Fundulus heteroclitus (L.) possesses two loci, Gpi-A and Gpi-B,
for the glycolytic enzyme, glucose-phosphate isomerase (GPI; D-
glucose-6-phosphate ketol-isomerase; E.C. 5.3.1.9). The Gpi-B locus is
polymorphic in Fundulus, with two common alleles, Gpi-Bb and Gpi-Bc,
distributed in a clinal manner in populations along the east coast of North
America. Since this clinal distribution is strongly correlated with a
temperature gradient, we asked whether the GPI-B2 allozymes were
functionally adapted to the thermal environment in which a given phenotype
predominated. The two major GPI-B2 allozymes were purified to homogeneity
and were characterized as to molecular weight, isoelectric pH, thermal
denaturation, and kinetic parameters. Both GPI-Bb2 and GPI- Bc2 allozymes
have molecular masses of 110 kD, and they have isoelectric pHs of 6.4 and
6.6, respectively. The GPI-Bb2 allozyme was more stable to thermal
denaturation than was the GPI-Bc2 enzyme. Kinetic properties of the allelic
isozymes were investigated both as a function of pH and as a function of
temperature. At 25 degrees C, over the pH range considered, there were no
significant differences between allozymes, either in Km for
fructose-6-phosphate or in Ki for 6- phosphogluconate, but apparent Vmax
values differed between pH 7.5 and pH 8.5. All steady-state kinetic
parameters showed strong temperature dependence, but the allozymes differed
only in the Ki for 6- phosphogluconate at temperatures greater than 30
degrees C. On the basis of the observed structural and functional
differences alluded to above, the hypothesis that the major allelic
isozymes of the Gpi-B locus were functionally equivalent was rejected.
However, it is not yet known whether these structural and functional
differences have any significance at higher levels of biological
organization.
相似文献
62.
The relative orientation of the pigments of reaction centers from Rhodopseudomonas sphaeroides has been studied by the photoselection technique.A high value (+0.45) of ) is obtained when exciting and observing within the 870 nm band which is contradictory to the results of Mar and Gingras (Mar, T. and Gingras, G. (1976) Biochim. Biophys. Acta 440, 609–621) and Shuvalov et al. (Shuvalov, V.A., Asadov, A.A. and Krakhmaleva, I.N. (1977) FEBS Lett. 76, 240–245). It is shown that the low values of p obtained by both groups were erroneous due to excitation conditions.Analysis of the polarization of light-induced changes when exciting with polarized light in single transitions (spheroiden band and bacteriopheophytin Qx bands) enable us to propose a possible arrangement of the pigments within the reaction center. It is concluded that the 870 nm band corresponds to a single transition and is one of the two bands of the primary electron donor (P-870). The second band of the bacteriochlorophyll dimer is centred at 805 nm. The Qy transitions of the molecules constituting the bacteriochlorophyll dimer are nearly parallel (angle less than 25°).The two bacteriopheophytin molecules present slightly different absorption spectra in the near infra-red. Both bacteriopheophytin absorption bands are subject to a small shift under illumination. The angle between the Qy bacteriopheophytin transitions is 55° or 125°. Both Qy transitions are nearly perpendicular to the 870 nm absorption band. Finally, the carotenoid molecules makes an angle greater than 70° with the 870 nm band and the other bacteriochlorophyll molecules. 相似文献
63.
Andrew RJ Mitchell Philip Roberts Jonas Eichhöfer Jonathan Timperley Oliver JM Ormerod 《Cardiovascular ultrasound》2004,2(1):1-4
Percutaneous coronary intervention can be associated with distal embolization of thrombotic material causing myocardial necrosis and infarction. We discuss the role of intravascular imaging to guide the use of a distal protection device by describing the outcome of a young woman presenting with non-ST elevation myocardial infarction. Coronary angiography demonstrated an isolated minor stenosis in the proximal left anterior descending coronary artery with slight haziness beyond the lesion. Intravascular ultrasound confirmed an extensive thrombus overlying a bulky atherosclerotic plaque. A distal filter wire was therefore successfully used to reduce the risk of distal embolization. The use of intravascular ultrasound in patients presenting with acute coronary syndrome may reveal large thrombi that are difficult to image using conventional angiographic techniques. Intravascular ultrasound can therefore be used as a tool to select lesions requiring distal protection. 相似文献
64.
65.
Kondo M Nakamura Y Fujii K Nagata M Suemori Y Dewa T Iida K Gardiner AT Cogdell RJ Nango M 《Biomacromolecules》2007,8(8):2457-2463
Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodoseudomonas palustris were self-assembled on a gold electrode modified with self-assembled monolayers (SAMs) of the alkanethiols NH2(CH2)nSH, n = 2, 6, 8, 11; HOOC(CH2)7SH; and CH3(CH2)7SH, respectively. Adsorption of the LH1-RC complexes on the SAMs depended on the terminating group of the alkanethiols, where the adsoption increased in the following order for the terminating groups: amino groups > carboxylic acid groups > methyl groups. Further, the adsorption on a gold electrode modified with SAMs of NH2(CH2)nSH, n = 2, 6, 8, 11, depended on the methylene chain length, where the adsorption increased with increasing the methylene chain length. The presence of the well-known light-harvesting and reaction center peaks of the near infrared (NIR) absorption spectra of the LH1-RC complexes indicated that these complexes were only fully stable on the SAM gold electrodes modified with the amino group. In the case of modification with the carboxyl group, the complexes were partially stable, while in the presence of the terminal methyl group the complexes were extensively denatured. An efficient photocurrent response of these complexes on the SAMs of NH2(CH2)nSH, n = 2, 6, 8, 11, was observed upon illumination at 880 nm. The photocurrent depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 6, which corresponds to a distance between the amino terminal group in NH2(CH2)6SH and the gold surface of 1.0 nm. 相似文献
66.
Fujii R Kita M Iinuma Y Oka N Takaesu Y Taira T Iha M Cogdell RJ Hashimoto H 《Photosynthesis research》2012,111(1-2):157-163
A chlorophyll c binding membrane intrinsic light-harvesting complex, the fucoxanthin-chlorophyll a/c protein (FCP), was isolated from cultured discoid germilings of an edible Japanese brown alga, Cladosiphon (C.) okamuranus TOKIDA (Okinawa Mozuku in Japanese). The discoid germiling is an ideal source of brown algal photosynthetic pigment-protein complexes in terms of its size and easiness of cultivation on a large scale. Ion-exchange chromatography was crucial for the purification of FCP from solubilized thylakoid proteins. The molecular weight of the purified FCP assembly was estimated to be ~56?kDa using blue native-PAGE. Further subunit analyses using 2D-PAGE revealed that the FCP assembled as a trimer consisting of two distinguishable subunits having molecular weights of 18.2 (H) and 17.5 (L)?kDa. Fluorescence and fluorescence-excitation spectra confirmed that the purified FCP assembly was functionally intact. 相似文献
67.
Spectral trends in the fluorescence of single bacterial light-harvesting complexes: experiments and modified redfield simulations 下载免费PDF全文
Rutkauskas D Novoderezhkin V Gall A Olsen J Cogdell RJ Hunter CN van Grondelle R 《Biophysical journal》2006,90(7):2475-2485
In this work we present and discuss the single-molecule fluorescence spectra of a variety of species of light-harvesting complexes: LH2 of Rhodopseudomonas acidophila, Rhodobacter sphaeroides, and Rhodospirillum molischianum and LH1 of Rhodobacter sphaeroides. The emission spectrum of these complexes varies as a function of time as was described in earlier work. For each type of complex, we observe a pronounced and well-reproducible characteristic relationship between the fluorescence spectral parameters of the peak wavelength, width, and asymmetry. This dependence for the LH2 complexes can be quantitatively explained on the basis of a disordered exciton model by varying the static disorder and phonon coupling parameters. In addition, a correlation of the pigment site energies has to be assumed to interpret the behavior of the LH1 complex. 相似文献
68.
69.
Pathway alterations during glioma progression revealed by reverse phase protein lysate arrays 总被引:2,自引:0,他引:2
Jiang R Mircean C Shmulevich I Cogdell D Jia Y Tabus I Aldape K Sawaya R Bruner JM Fuller GN Zhang W 《Proteomics》2006,6(10):2964-2971
The progression of gliomas has been extensively studied at the genomic level using cDNA microarrays. However, systematic examinations at the protein translational and post-translational levels are far more limited. We constructed a glioma protein lysate array from 82 different primary glioma tissues, and surveyed the expression and phosphorylation of 46 different proteins involved in signaling pathways of cell proliferation, cell survival, apoptosis, angiogenesis, and cell invasion. An analysis algorithm was employed to robustly estimate the protein expressions in these samples. When ranked by their discriminating power to separate 37 glioblastomas (high-grade gliomas) from 45 lower-grade gliomas, the following 12 proteins were identified as the most powerful discriminators: IBalpha, EGFRpTyr845, AKTpThr308, phosphatidylinositol 3-kinase (PI3K), BadpSer136, insulin-like growth factor binding protein (IGFBP) 2, IGFBP5, matrix metalloproteinase 9 (MMP9), vascular endothelial growth factor (VEGF), phosphorylated retinoblastoma protein (pRB), Bcl-2, and c-Abl. Clustering analysis showed a close link between PI3K and AKTpThr308, IGFBP5 and IGFBP2, and IBalpha and EGFRpTyr845. Another cluster includes MMP9, Bcl-2, VEGF, and pRB. These clustering patterns may suggest functional relationships, which warrant further investigation. The marked association of phosphorylation of AKT at Thr308, but not Ser473, with glioblastoma suggests a specific event of PI3K pathway activation in glioma progression. 相似文献
70.
In vitro self-assembly of the light harvesting pigment-protein LH2 revealed by ultrafast spectroscopy and electron microscopy 下载免费PDF全文
Schubert A Stenstam A Beenken WJ Herek JL Cogdell R Pullerits T Sundström V 《Biophysical journal》2004,86(4):2363-2373
Controlled ensemble formation of protein-surfactant systems provides a fundamental concept for the realization of nanoscale devices with self-organizing capability. In this context, spectroscopic monitoring of pigment-containing proteins yields detailed structural information. Here we have studied the association behavior of the bacterial light-harvesting protein LH2 from Rhodobacter spheroides in an n,n-dimethyldodecylamine-n-oxide/water environment. Time-resolved studies of the excitation annihilation yielded information about aggregate sizes and packing of the protein complexes therein. The results are compared to transmission electron microscopy images of instantaneously frozen samples. Our data indicate the manifestation of different phases, which are discussed with respect to the thermodynamic equilibrium in ternary protein-surfactant-water systems. Accordingly, by varying the concentration the formation of different types of aggregates can be controlled. Conditions for the appearance of isolated LH2 complexes are defined. 相似文献