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101.
102.
Electrical and adaptive properties of rod photoreceptors in bufo marinus. I. Effects of altered extracellular Ca(2+) levels 下载免费PDF全文
The effects of altering extracellular Ca(2+) levels on the electrical and adaptive properties of toad rods have been examined. The retina was continually superfused in control (1.6 mM Ca(2+)) or test ringer’s solutions, and rod electrical activity was recorded intracellularly. Low-calcium ringer’s (10(-9)M Ca(2+)) superfused for up to 6 min caused a substantial depolarization of the resting membrane potential, an increase in light-evoked response amplitudes, and a change in the waveform of the light-evoked responses. High Ca(2+) ringer’s (3.2 mM) hyperpolarized the cell membrane and decreased response amplitudes. However, under conditions of either low or high Ca(2+) superfusion for up to 6 min, in both dark-adapted and partially light-adapted states, receptor sensitivity was virtually unaffected; i.e., the V-log I curve for the receptor potential was always located on the intensity scale at a position predicted by the prevailing light level, not by Ca(2+) concentration. Thus, we speculate that cytosol Ca(2+) concentration is capable of regulating membrane potential levels and light-evoked response amplitudes, but not the major component of rod sensitivity. Low Ca(2+) ringer’s also shortened the period of receptor response saturation after a bright but nonbleaching light flash, hence accelerating the onset of both membrane potential and sensitivity recovery during dark adaptation.
Exposure of the retina to low Ca(2+) (10(-9)M) ringer’s for long periods (7-15 min) caused dark-adapted rods to lose responsiveness. Response amplitudes gradually decreased, and the rods became desensitized. These severe conditions of low Ca(2+) caused changes in the dark-adapted rod that mimic those observed in rods during light adaptation. We suggest that loss of receptor sensitivity during prolonged exposure to low Ca(2+) ringer’s results from a decrease of intracellular (intradisk) stores of Ca(2+); i.e., less Ca(2+) is thereby released per quantum catch.
相似文献103.
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Mario Bronzati Roger B.J. Benson Serjoscha W. Evers Martín D. Ezcurra Sergio F. Cabreira Jonah Choiniere Kathleen N. Dollman Ariana Paulina-Carabajal Viktor J. Radermacher Lucio Roberto-da-Silva Gabriela Sobral Michelle R. Stocker Lawrence M. Witmer Max C. Langer Sterling J. Nesbitt 《Current biology : CB》2021,31(12):2520-2529.e6
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105.
From the 1820s pith became a familiar material in Europe, under the name of rice‐paper, as a raw material for artificial flowers, and as a medium for export paintings from China. The structure of pith sheets was early recognised as different to that of paper, but it was not until 1852 that William Jackson Hooker was able to describe the source plant, as Aralia papyrifera Hook., now Tetrapanax papyrifer (Hook.) K. Koch. Using his consular contacts, Hooker was able to build up a remarkable collection of pith, as raw materials, artificial flowers and Chinese paintings. Many are described and illustrated in this article, in the context of recent work on the history and conservation of pith paintings. 相似文献
106.
A system of nomenclature for band patterns of mouse chromosomes 总被引:40,自引:0,他引:40
Mouse chromosomes banded by quinacrine mustard staining, by the ASG technique, or by Giemsa staining following trypsinization or chymotrypsinization are described in detail. Three hundred and twelve regions within the mouse karyotype can be distinguished and a simple system of nomenclature is proposed for naming these regions. This nomenclature is applied to discussion of the locations of the breakpoints of twenty translocations and of many specific gene loci.Dedicated to the memory of Dr. Stanley W. Wright, in gratitude for his support of, and interest in, our work.Supported by Cancer Research Funds of the University of California and USPHS Grant HD 04608. 相似文献
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Sascha C. Hughan Christopher M. Spring Simone M. Schoenwaelder Sharelle Sturgeon Imala Alwis Yuping Yuan James D. McFadyen Erik Westein Duncan Goddard Akiko Ono Yuji Yamanashi Warwick S. Nesbitt Shaun P. Jackson 《The Journal of biological chemistry》2014,289(8):5051-5060
The Dok proteins are a family of adaptor molecules that have a well defined role in regulating cellular migration, immune responses, and tumor progression. Previous studies have demonstrated that Doks-1 to 3 are expressed in platelets and that Dok-2 is tyrosine-phosphorylated downstream of integrin αIIbβ3, raising the possibility that it participates in integrin αIIbβ3 outside-in signaling. We demonstrate that Dok-2 in platelets is primarily phosphorylated by Lyn kinase. Moreover, deficiency of Dok-2 leads to dysregulated integrin αIIbβ3-dependent cytosolic calcium flux and phosphatidylinositol(3,4)P2 accumulation. Although agonist-induced integrin αIIbβ3 affinity regulation was unaltered in Dok-2−/− platelets, Dok-2 deficiency was associated with a shear-dependent increase in integrin αIIbβ3 adhesive function, resulting in enhanced platelet-fibrinogen and platelet-platelet adhesive interactions under flow. This increase in adhesion was restricted to discoid platelets and involved the shear-dependent regulation of membrane tethers. Dok-2 deficiency was associated with an increased rate of platelet aggregate formation on thrombogenic surfaces, leading to accelerated thrombus growth in vivo. Overall, this study defines an important role for Dok-2 in regulating biomechanical adhesive function of discoid platelets. Moreover, they define a previously unrecognized prothrombotic mechanism that is not detected by conventional platelet function assays. 相似文献
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