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51.
Modulatory multiplicity in the feeding mechanism in cichlid fishes, as exemplified by the invertebrate pickers of Lake Tanganyika 总被引:4,自引:0,他引:4
Electromyography, motion analysis, osteology, myology and feeding behaviour of a morphologically specialized monophyletic lineage of cichlids in Lake Tanganyika have revealed that Eretmodus, Spathodus and Tanganicodus possess a feeding apparatus with a more extensive functional repertoire than that of any other teleost studied to date. When collecting a wide range of foods by inertial suction this trophic group can employ two strategies, a preprogrammed cyclical, energy saving pattern, or a modulated mode effected by extensive overlap of the firing patterns of multiple muscles resulting in a precise control of the magnitude and direction of suction. When dislodging sessile prey from the substrate the complexity of electromyographic and kinematic patterns increases. Because upper jaw protrusion can be effected and controlled independently from the complex couplings causing mouth opening and movements of the suspensory apparatus, a new decoupled model of upper jaw protrusion is proposed. The decoupled model predicts that upper jaw protrusion can be effected directly by contraction of epaxial muscles that raise the neurocranium, causing the premaxillae to slide anteroventrally. Upper jaw protrusion can be modulated continuously and directly by balanced cocontractions of antagonistic muscle sets giving the decoupled model an improved function over a very extensive range. The morphologically symmetrical muscular apparatus can function asymmetrically. Very pronounced asymmetrical firings of multiple muscles produce a continuously modulated jaw mechanism with an extensive repertoire. 相似文献
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Charles A. Berdan Karel A. Erion Nathan E. Burritt Barbara E. Corkey Jude T. Deeney 《PloS one》2016,11(2)
Lipid signals derived from lipolysis and membrane phospholipids play an important role in glucose-stimulated insulin secretion (GSIS), though the exact secondary signals remain unclear. Previous reports have documented a stimulatory role of exogenously added mono-acyl-glycerol (MAG) on insulin secretion from cultured β-cells and islets. In this report we have determined effects of increasing intracellular MAG in the β-cell by inhibiting mono-acyl-glycerol lipase (MGL) activity, which catalyzes the final step in triacylglycerol breakdown, namely the hydrolysis of MAG to glycerol and free fatty acid (FA). To determine the role of MGL in GSIS, we used three different pharmacological agents (JZL184, MJN110 and URB602). All three inhibited GSIS and depolarization-induced insulin secretion in INS-1 (832/13). JZL184 significantly inhibited both GSIS and depolarization-induced insulin secretion in rat islets. JZL184 significantly decreased lipolysis and increased both mono- and diacyglycerol species in INS-1 cells. Analysis of the kinetics of GSIS showed that inhibition was greater during the sustained phase of secretion. A similar pattern was observed in the response of Ca2+ to glucose and depolarization but to a lesser degree suggesting that altered Ca2+ handling alone could not explain the reduction in insulin secretion. In addition, a significant reduction in long chain-CoA (LC-CoA) was observed in INS-1 cells at both basal and stimulatory glucose following inhibition of MGL. Our data implicate an important role for MGL in insulin secretion. 相似文献
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Hans J. De Boeck Juliette M. G. Bloor Rien Aerts Michael Bahn Claus Beier Bridget A. Emmett Marc Estiarte Jos M. Grünzweig Aud H. Halbritter Petr Holub Anke Jentsch Karel Klem Juergen Kreyling Gyrgy Krel‐Dulay Klaus Steenberg Larsen Alexandru Milcu Jacques Roy Bjarni D. Sigurdsson Melinda D. Smith Marcelo Sternberg Vigdis Vandvik Thomas Wohlgemuth Ivan Nijs Alan K. Knapp 《Global Change Biology》2020,26(2):e6-e7
56.
Maud N. Vissers Peter L. Zock Rianne Leenen Annet J.C. Roodenburg Karel P.A.M. Van Putte Martijn B. Katan 《Free radical research》2013,47(5):619-629
A high intake of olive oil has been proposed as an explanation for the low incidence of coronary heart disease in Mediterranean countries, but it is unclear whether olive oil offers specific benefits beyond a low content of saturated fat. Some types of extra virgin olive oil are rich in non-polar phenols, which might be taken up by plasma LDL particles and protect these from becoming atherogenic by oxidative modification. In a pilot study we found that consumption of 47 g fortified olive oil containing 31 mg phenols significantly increased the lag time of LDL oxidation from 112 ± 5 min before to 130 ± 7 min 2h after the meal. However, this study was not controlled, and in the current study we therefore investigated whether olive oil phenols increase the lag time of LDL oxidation in postprandial samples when compared with a control group.Twelve healthy men and women consumed four different olive oil supplements with a meal on four separate occasions: one similar to the supplement in the pilot study (positive control); one containing mainly non-polar olive oil phenols; one containing mainly polar olive oil phenols; and one without phenols (placebo). Lag time significantly increased 2 h after the meals with the positive control (8 ± 2 min), the polar phenols (8 ± 2 min), and the placebo (8 ± 2 min), but not after the non-polar phenols (-0.4 ± 3 min). Increases were not statistically different between supplements.These results indicate that the lag time of LDL-oxidation is increased after consumption of a meal. This increase is probably due to non-specific meal or time effects and not to phenols from olives or olive oil. Furthermore, these findings stress the need for adequate controlled studies to avoid misinterpretations of the data. 相似文献
57.
Mohamed I. Elzagheid Mikko Oivanen Karel D. Klika Bryan C. N. M. Jones Richard Cosstick Harri Lönnberg 《Nucleosides, nucleotides & nucleic acids》2013,32(9):2093-2108
Abstract The course of hydrolysis of 3′-deoxy-3′-thioinosylyl-(3′ → 5′)-uridine (IspU) has been followed by HPLC over a wide pH-range. Two reactions of the internucleosidic thiophosphate linkage compete: (i) cleavage yielding thioinosine monophosphates and uridine, and (ii) isomerization to the 2′,5′-isomer of IspU. Under very acidic conditions, even acid-catalyzed depurination of the inosine moiety is observed. The stability of the thiophosphate linkage and the mechanisms of its rupture are discussed. 相似文献
58.
Karel Pomeisl Květoslava Horská Radek Pohl Jiří Blažek Marcela Krečmerová 《Nucleosides, nucleotides & nucleic acids》2013,32(3):159-171
A series of new monophosphates of 1-[2-(phosphonomethoxy)alkyl]thymines, such as PMPTp, 3-MeO-PMPTp, HPMPTp, and FPMPTp, were synthesized and tested for their ability to inhibit human thymidine phosphorylase. Kinetic measurements of enzyme activity were performed using thymidine and inorganic phosphate as the substrates. The data show that some monophosphates provide a considerable increase of the multisubstrate inhibitory effect. The highest inhibitory potency was found with (R)-FPMPTp 4c (K i dT = 4.09 ± 0.47 μM, K i(Pi) = 2.13 ± 0.29 μM) and (R) 3-MeO-PMPTp 4d (K i dT = 5.78 ± 0.71 μM, K i(Pi) = 2.71 ± 0.37 μM). 相似文献
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60.
Carlos Oscar Sánchez Sorzano Alberto Pascual-Montano Ainhoa Sánchez de Diego Carlos Martínez-A Karel H.M. van Wely 《Cell cycle (Georgetown, Tex.)》2013,12(13):2016-2023
The acquisition of massive but localized chromosome translocations, a phenomenon termed chromothripsis, has received widespread attention since its discovery over a year ago. Until recently, chromothripsis was believed to originate from a single catastrophic event, but the molecular mechanisms leading to this event are yet to be uncovered. Because a thorough interpretation of the data are missing, the phenomenon itself has wrongly acquired the status of a mechanism used to justify many kinds of complex rearrangements. Although the assumption that all translocations in chromothripsis originate from a single event has met with criticism, satisfactory explanations for the intense but localized nature of this phenomenon are still missing. Here, we show why the data used to describe massive catastrophic rearrangements are incompatible with a model comprising a single event only and propose a molecular mechanism in which a combination of known cellular pathways accounts for chromothripsis. Instead of a single traumatic event, the protection of undamaged chromosomes by telomeres can limit repetitive breakage-fusion-bridge events to a single chromosome arm. Ultimately, common properties of chromosomal instability, such as aneuploidy and centromere fission, might establish the complex genetic pattern observed in this genomic state. 相似文献