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61.
A. Draguhn G. Börner R. Beckmann K. Buchner U. Heinemann F. Hucho 《The Journal of membrane biology》1997,158(2):159-166
Eucaryotic nuclei are surrounded by a double-membrane system enclosing a central cisterna which is continuous with the endoplasmic
reticulum and serves as a calcium store for intracellular signaling. The envelope regulates protein and nucleic acid traffic
between the nucleus and the cytoplasm via nuclear pores. These protein tunnels cross through both nuclear membranes and are
permeable for large molecules. Surprisingly, patch clamp recordings from isolated nuclei of different cell species have revealed
a high resistance of the envelope, enabling tight seals and the resolution of single ion channel activity. Here we present
for the first time single-channel recordings from nuclei prepared from neuronal tissue. Nuclei isolated from rat cerebral
cortex displayed spontaneous long-lasting large conductances in the nucleus-attached mode as well as in excised patches. The
open times are in the range of seconds and channel activity increases with depolarization. The single-channel conductance
in symmetrical K+ is 166 pS. The channels are selective for cations with P
K/P
Na= 2. They are neither permeable to, nor gated by Ca2+. Thus, neuronal tissue nuclei contain a large conductance ion channel selective for monovalent cations which may contribute
to ionic homeostasis in the complex compartments surrounding these organelles.
Received: 12 November 1996/Revised: 18 February 1997 相似文献
62.
No Abstract Available 相似文献
63.
The physiological effects of social rank were examined in three different experiments with Neolamprologus pulcher a cooperatively breeding cichlid, endemic to Lake Tanganyika, East Africa. The effects of rank on physiology between pairs of dominant and subordinate size‐matched fish (experiment 1) and among groups of four size‐matched fish (experiment 2) were examined. A third experiment mimicked the natural social structure in the wild; pairs were observed with other group members including breeders. The effect of social position was investigated on growth rates, liver concentrations of adenosine triphospate (ATP), lipids, proteins, creatine phosphate (CrP), glucose and glycogen as well as plasma cortisol. In naturalistic group settings, dominants displayed higher levels of liver protein and plasma cortisol. In the absence of breeders, dominant individuals (of helper pairs) had higher liver glycogen levels and dominant fish (held in groups of four) grew most. These results support previous cooperatively breeding mammal studies and suggest that dominant individuals experience higher cortisol levels as well as higher growth rates. 相似文献
64.
Hans Buchner 《Development genes and evolution》1942,141(2):154-158
Zusammenfassung Mit Hilfe der Verpflanzung aus dem Teich in Laboratoriumsbedingungen können amiktisch sich vermehrende Weibchen einer heterogonen Rädertierart zur Erzeugung miktischer Töchter gezwungen werden. Der Milieuwechsel kann die Fortpflanzungsart der bereits aus dem Ei geschlüpften Weibchen nicht mehr verändern. Er ist auch wirkungslos, wenn er Eier trifft, welche aus dem Geschlechtsapparat der Mutter bereits ausgetreten sind oder kurz davor stehen. Die Determination der Fortpflanzungsart erfolgt auf einem früheren Entwicklungsstadium des Eies. Die Resultate stimmen bei allen geprüften Arten überein.Mit Unterstützung der Basler Stiftung für experimentelle Zoologie. 相似文献
65.
The planar motion of the human knee joint is modeled, involving the relative motion of the geometry of the contacting surface between the tibia and the femur. The pure gliding motion and the pure rolling motion are formulated including the holonomic and nonholonomic constraints that must be satisfied. A control strategy with two classes of inputs: muscle forces that stabilize and bring about the motion and the ligament forces that maintain the constraints is presented. Finally, the effectiveness of this control structure is demonstrated via digital computer simulations in the pure gliding motion and the pure rolling motion of the knee. 相似文献
66.
67.
Previous studies sought to test for the existence of a “cheater-detection module” by testing for enhanced memory for the faces of cheaters, but past results have been inconclusive. Here, we present four experiments showing that old–new discrimination was not affected by whether a face was associated with a history of cheating, trustworthy or irrelevant behavior. In contrast, source memory for faces associated with a history of cheating (i.e., memory for the cheating context in which the face was encountered) was consistently better than source memory for other types of faces. This pattern held under a variety of conditions, including different types of judgments participants made about the stimulus persons (attractiveness in Experiment 1; likeability in Experiments 2–4), different retention intervals (a few minutes in Experiments 1, 2 and 4; 1 week in Experiment 3), whether the behaviors were exceptional or ordinary (Experiments 1–3) and whether the social status of the characters was low or high (Experiment 4). Given no differences in old–new discrimination, enhanced source memory for faces of cheaters may be useful for avoiding cheaters in future interactions. 相似文献
68.
Reconstitution of a heat shock effect in vitro: influence of GroE on the thermal aggregation of alpha-glucosidase from yeast. 总被引:10,自引:0,他引:10
alpha-Glucosidase from yeast is inactivated rapidly at temperatures above 42 degrees C. The thermal inactivation is accompanied by aggregation. The molecular chaperone GroEL suppresses the formation of aggregates by binding the thermally inactivated alpha-glucosidase. Spectroscopic studies suggest that GroEL binds alpha-glucosidase in an intermediately folded state. The complex between alpha-glucosidase and GroEL can be dissolved by MgATP. GroES accelerates the MgATP-dependent dissociation of the alpha-glucosidase-GroEL complex. At elevated temperatures this release leads to the formation of aggregates, while at lower temperatures native, enzymatically active molecules are formed. 相似文献
69.
70.