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71.
72.
Effective cellular uptake and efflux of thyroid hormone by human monocarboxylate transporter 10 总被引:1,自引:0,他引:1
Friesema EC Jansen J Jachtenberg JW Visser WE Kester MH Visser TJ 《Molecular endocrinology (Baltimore, Md.)》2008,22(6):1357-1369
Cellular entry of thyroid hormone is mediated by plasma membrane transporters, among others a T-type (aromatic) amino acid transporter. Monocarboxylate transporter 10 (MCT10) has been reported to transport aromatic amino acids but not iodothyronines. Within the MCT family, MCT10 is most homologous to MCT8, which is a very important iodothyronine transporter but does not transport amino acids. In view of this paradox, we decided to reinvestigate the possible transport of thyroid hormone by human (h) MCT10 in comparison with hMCT8. Transfection of COS1 cells with hMCT10 cDNA resulted in 1) the production of an approximately 55 kDa protein located to the plasma membrane as shown by immunoblotting and confocal microscopy, 2) a strong increase in the affinity labeling of intracellular type I deiodinase by N-bromoacetyl-[(125)I]T(3), 3) a marked stimulation of cellular T(4) and, particularly, T(3) uptake, 4) a significant inhibition of T(3) uptake by phenylalanine, tyrosine, and tryptophan of 12.5%, 22.2%, and 51.4%, respectively, and 5) a marked increase in the intracellular deiodination of T(4) and T(3) by different deiodinases. Cotransfection studies using the cytosolic thyroid hormone-binding protein micro-crystallin (CRYM) indicated that hMCT10 facilitates both cellular uptake and efflux of T(4) and T(3). In the absence of CRYM, hMCT10 and hMCT8 increased T(3) uptake after 5 min incubation up to 4.0- and 1.9-fold, and in the presence of CRYM up to 6.9- and 5.8-fold, respectively. hMCT10 was less active toward T(4) than hMCT8. These findings establish that hMCT10 is at least as active a thyroid hormone transporter as hMCT8, and that both transporters facilitate iodothyronine uptake as well as efflux. 相似文献
73.
Computer simulations have become an invaluable tool to studythe sometimes counterintuitive temporal dynamics of (bio-)chemicalsystems. In particular, stochastic simulation methods have attractedincreasing interest recently. In contrast to the well-knowndeterministic approach based on ordinary differential equations,they can capture effects that occur due to the underlying discretenessof the systems and random fluctuations in molecular numbers.Numerous stochastic, approximate stochastic and hybrid simulationmethods have been proposed in the literature. In this article,they are systematically reviewed in order to guide the researcherand help her find the appropriate method for a specific problem. 相似文献
74.
Li Ding Maciej Paszkowski-Rogacz Anja Nitzsche Mikolaj Michal Slabicki Anne-Kristin Heninger Ingrid de Vries Ralf Kittler Magno Junqueira Andrej Shevchenko Herbert Schulz Norbert Hubner Michael Xavier Doss Agapios Sachinidis Juergen Hescheler Roberto Iacone Konstantinos Anastassiadis A. Francis Stewart M. Teresa Pisabarro Antonio Caldarelli Ina Poser Frank Buchholz 《Cell Stem Cell》2009,4(5):403-415
75.
de Armas-Ricard M Levicán G Katz A Moser J Jahn D Orellana O 《Biochemical and biophysical research communications》2011,(1):134-139
Prestin, a multipass transmembrane protein whose N- and C-termini are localized to the cytoplasm, must be trafficked to the plasma membrane to fulfill its cellular function as a molecular motor. One challenge in studying prestin sequence-function relationships within living cells is separating the effects of amino acid substitutions on prestin trafficking, plasma membrane localization and function. To develop an approach for directly assessing prestin levels at the plasma membrane, we have investigated whether fusion of prestin to a single pass transmembrane protein results in a functional fusion protein with a surface-exposed N-terminal tag that can be detected in living cells. We find that fusion of the biotin-acceptor peptide (BAP) and transmembrane domain of the platelet-derived growth factor receptor (PDGFR) to the N-terminus of prestin-GFP yields a membrane protein that can be metabolically-labeled with biotin, trafficked to the plasma membrane, and selectively detected at the plasma membrane using fluorescently-tagged streptavidin. Furthermore, we show that the addition of a surface detectable tag and a single-pass transmembrane domain to prestin does not disrupt its voltage-sensitive activity. 相似文献
76.
77.
Dae Hyun Lee Martijn J. C. Dane Bernard M. van den Berg Margien G. S. Boels Jurgen W. van Teeffelen Renée de Mutsert Martin den Heijer Frits R. Rosendaal Johan van der Vlag Anton Jan van Zonneveld Hans Vink Ton J. Rabelink for the NEO study group 《PloS one》2014,9(5)
Changes in endothelial glycocalyx are one of the earliest changes in development of cardiovascular disease. The endothelial glycocalyx is both an important biological modifier of interactions between flowing blood and the vessel wall, and a determinant of organ perfusion. We hypothesize that deeper penetration of erythrocytes into the glycocalyx is associated with reduced microvascular perfusion. The population-based prospective cohort study (the Netherlands Epidemiology of Obesity [NEO] study) includes 6,673 middle-aged individuals (oversampling of overweight and obese individuals). Within this cohort, we have imaged the sublingual microvasculature of 915 participants using sidestream darkfield (SDF) imaging together with a recently developed automated acquisition and analysis approach. Presence of RBC (as a marker of microvascular perfusion) and perfused boundary region (PBR), a marker for endothelial glycocalyx barrier properties for RBC accessibility, were assessed in vessels between 5 and 25 µm RBC column width. A wide range of variability in PBR measurements, with a mean PBR of 2.14 µm (range: 1.43–2.86 µm), was observed. Linear regression analysis showed a marked association between PBR and microvascular perfusion, reflected by RBC filling percentage (regression coefficient β: −0.034; 95% confidence interval: −0.037 to −0.031). We conclude that microvascular beds with a thick (“healthy”) glycocalyx (low PBR), reflects efficient perfusion of the microvascular bed. In contrast, a thin (“risk”) glycocalyx (high PBR) is associated with a less efficient and defective microvascular perfusion. 相似文献
78.
Claudiu Niculaes Kris Morreel Hoon Kim Fachuang Lu Lauren S. McKee Bart Ivens Jurgen Haustraete Bartel Vanholme Riet De Rycke Magnus Hertzberg Jorg Fromm Vincent Bulone Andrea Polle John Ralph Wout Boerjan 《The Plant cell》2014,26(9):3775-3791
Phenylcoumaran benzylic ether reductase (PCBER) is one of the most abundant proteins in poplar (Populus spp) xylem, but its biological role has remained obscure. In this work, metabolite profiling of transgenic poplar trees downregulated in PCBER revealed both the in vivo substrate and product of PCBER. Based on mass spectrometry and NMR data, the substrate was identified as a hexosylated 8–5-coupling product between sinapyl alcohol and guaiacylglycerol, and the product was identified as its benzyl-reduced form. This activity was confirmed in vitro using a purified recombinant PCBER expressed in Escherichia coli. Assays performed on 20 synthetic substrate analogs revealed the enzyme specificity. In addition, the xylem of PCBER-downregulated trees accumulated over 2000-fold higher levels of cysteine adducts of monolignol dimers. These compounds could be generated in vitro by simple oxidative coupling assays involving monolignols and cysteine. Altogether, our data suggest that the function of PCBER is to reduce phenylpropanoid dimers in planta to form antioxidants that protect the plant against oxidative damage. In addition to describing the catalytic activity of one of the most abundant enzymes in wood, we provide experimental evidence for the antioxidant role of a phenylpropanoid coupling product in planta. 相似文献
79.
Mapping nutrient resorption efficiencies of subarctic cryptogams and seed plants onto the Tree of Life 下载免费PDF全文
Simone I. Lang Rien Aerts Richard S. P. van Logtestijn Wenka Schweikert Thorsten Klahn Helen M. Quested Jurgen R. van Hal Johannes H. C. Cornelissen 《Ecology and evolution》2014,4(11):2217-2227
Nutrient resorption from senescing photosynthetic organs is a powerful mechanism for conserving nitrogen (N) and phosphorus (P) in infertile environments. Evolution has resulted in enhanced differentiation of conducting tissues to facilitate transport of photosynthate to other plant parts, ultimately leading to phloem. Such tissues may also serve to translocate N and P to other plant parts upon their senescence. Therefore, we hypothesize that nutrient resorption efficiency (RE, % of nutrient pool exported) should correspond with the degree of specialization of these conducting tissues across the autotrophic branches of the Tree of Life. To test this hypothesis, we had to compare members of different plant clades and lichens within a climatic region, to minimize confounding effects of climatic drivers on nutrient resorption. Thus, we compared RE among wide‐ranging basal clades from the principally N‐limited subarctic region, employing a novel method to correct for mass loss during senescence. Even with the limited numbers of species available for certain clades in this region, we found some consistent patterns. Mosses, lichens, and lycophytes generally showed low REN (<20%), liverworts and conifers intermediate (40%) and monilophytes, eudicots, and monocots high (>70%). REP appeared higher in eudicots and liverworts than in mosses. Within mosses, taxa with more efficient conductance also showed higher REN. The differences in REN among clades broadly matched the degree of specialization of conducting tissues. This novel mapping of a physiological process onto the Tree of Life broadly supports the idea that the evolution of conducting tissues toward specialized phloem has aided land plants to optimize their internal nitrogen recycling. The generality of evolutionary lines in conducting tissues and nutrient resorption efficiency needs to be tested across different floras in different climatic regions with different levels of N versus P availability. 相似文献
80.
Elizabeth W. Maas Jurgen Thiele Caryn Thompson Rebecca M. Latter Heather J.L. Brooks 《Journal of applied phycology》2000,12(1):95-98
In order to study saxitoxin (STX) production bymicro-algae in the laboratory, a defined algal culture medium which supports
optimum growth over a longtime-period is a requirement. In the development of such a medium, a number of modifications were
made to a standard algal culture medium (GP) and growth of a STX-producing isolate of Alexandrium minutum in the different formulations was assessed by measuring maximum cell densities and mean generation times (MGT). All experiments
were carried out under controlled conditions in an aerobic atmosphere with increased CO2. Whilst maximum cell densities in the different modifications were similar, the MGT was significantly shortened by the addition
of Tris buffer and the trace metals strontium, selenium and molybdenum. Replacement of natural with artificial seawater and
removal of soil extract did not adversely affect algal growth. Five of the six media formulations supported the growth of
A. minutumover a 9-month period.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献