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101.
102.
The attentional demands of automatic and controlled processing were investigated in a dual task paradigm. Ss performed consistent and varied mapping versions of an S. Sternberg (see record 1966-10810-001) memory search task, both separately and together with a recognition running-memory task. In different conditions, Ss were instructed to maximize their performance on either the Sternberg or running memory tasks or to emphasize the tasks equally. Processing priority and memory load had large effects on performance when the variably mapped version of the Sternberg task was paired with the running memory task. Performance decrements in these conditions were accompanied by trade-offs in the amplitude of the P300 component of the event-related brain potential, presumably reflecting the distribution of attention between the tasks. Performance in the consistently mapped version of the Sternberg task was relatively unaffected by memory load or dual task demands. Large P300s, which were insensitive to manipulations of memory load and priority, were elicited in the consistently mapped conditions. These P300s appear to reflect the obligatory allocation of attention to task-relevant events during automatic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
S Engelender AH Sharp V Colomer MK Tokito A Lanahan P Worley EL Holzbaur CA Ross 《Canadian Metallurgical Quarterly》1997,6(13):2205-2212
Huntington's disease (HD) is an inherited neurodegenerative disease caused by expansion of a polyglutamine repeat in the HD protein huntingtin. Huntingtin's localization within the cell includes an association with cytoskeletal elements and vesicles. We previously identified a protein (HAP1) which binds to huntingtin in a glutamine repeat length-dependent manner. We now report that HAP1 interacts with cytoskeletal proteins, namely the p150 Glued subunit of dynactin and the pericentriolar protein PCM-1. Structural predictions indicate that both HAP1 and the interacting proteins have a high probability of forming coiled coils. We examined the interaction of HAP1 with p150 Glued . Binding of HAP1 to p150 Glued (amino acids 879-1150) was confirmed in vitro by binding of p150 Glued to a HAP1-GST fusion protein immobilized on glutathione-Sepharose beads. Also, HAP1 co-immunoprecipitated with p150 Glued from brain extracts, indicating that the interaction occurs in vivo . Like HAP1, p150 Glued is highly expressed in neurons in brain and both proteins are enriched in a nerve terminal vesicle-rich fraction. Double label immunofluorescence experiments in NGF-treated PC12 cells using confocal microscopy revealed that HAP1 and p150 Glued partially co-localize. These results suggest that HAP1 might function as an adaptor protein using coiled coils to mediate interactions among cytoskeletal, vesicular and motor proteins. Thus, HAP1 and huntingtin may play a role in vesicle trafficking within the cell and disruption of this function could contribute to the neuronal dysfunction and death seen in HD. 相似文献
104.
105.
Porins are trimeric channel-forming proteins of the outer membrane of
Escherichia coli. Each subunit contains 16 beta-strands forming a
transmembrane beta-barrel whose pore is constricted by the third
extracellular loop (L3). We investigated the effects of site-directed
mutations at two critical regions of the OmpC porin: (i) the D315A mutation
targets a key component of a putative hydrogen bond network linking the L3
loop to the adjacent barrel wall and (ii) the D118Q, R174Q and R92Q
mutations target putative salt bridges at the root of the L3 loop. We
purified the outer membrane fractions obtained from each mutant and
reconstituted them in liposomes suitable for electrophysiology. Patch clamp
experiments showed that the frequency of spontaneous transitions between
open and closed states is increased in the D315A, D118Q and R92Q mutants
but unchanged in the R174Q mutant. These transitions are not driven by
transmembrane voltage changes and represent the thermal oscillations
between functionally distinct conformations. The asymmetric
voltage-dependent inactivation of the channels is not affected by the
mutations, however, suggesting different molecular mechanisms for the
spontaneous and voltage- dependent gating processes. We propose that the
positioning or flexibility of the L3 loop across the pore, as governed by
the putative hydrogen-bond network and a salt bridge, play a role in
determining the frequency of spontaneous channel gating.
相似文献
106.
FIRE: flexible intra-AS routing environment 总被引:2,自引:0,他引:2
Partridge C. Snoeren A.C. Strayer W.T. Schwartz B. Condell M. Castineyra I. 《Selected Areas in Communications, IEEE Journal on》2001,19(3):410-425
Current routing protocols are monolithic, specifying the algorithm used to construct forwarding tables, the metric used by the algorithm (generally some form of hop count), and the protocol used to distribute these metrics as an integrated package. The flexible intra-AS routing environment (FIRE) is a link-state, intradomain routing protocol that decouples these components. FIRE supports run-time-programmable algorithms and metrics over a secure link-state distribution protocol. By allowing the network operator to dynamically reprogram both the properties being advertised and the routing algorithms used to construct forwarding tables, FIRE enables the development and deployment of novel routing algorithms without the need for a new protocol to distribute state. FIRE supports multiple concurrent routing algorithms and metrics, each constructing separate forwarding tables. By using operator-specified packet filters, separate classes of traffic may be routed using completely different routing algorithms, all supported by a single routing protocol. This paper presents an overview of FIRE, focusing particularly on FIRE's novel aspects with respect to traditional routing protocols. We consider deploying several current unicast and multicast routing algorithms in FIRE, and describe our Java-based implementation 相似文献
107.
108.
Juvenile rats are more susceptible to the acute toxicity of the phosphorothionate insecticides parathion and chlorpyrifos than are adult rats. Developmental changes in brain acetylcholinesterase and hepatic aliesterase (carboxylesterase), cytochrome P450, and the P450-mediated metabolism of these two phosphorothionate insecticides were investigated in male Sprague-Dawley rats. Specific activities of acetylcholinesterase in cerebral cortex, but not medulla oblongata, and of liver aliesterases increased with age, indicating the presence of both more target esterases and more protective esterases, respectively, in the adult compared to the juvenile animal. Sensitivity of the brain acetylcholinesterase to inhibition by paraoxon and chlorpyrifosoxon, as measured by IC50 values, did not change significantly with age, whereas the hepatic aliesterase sensitivity to inhibition decreased with age. Progressive increases in activities of P450-mediated activation (desulfuration) (6- to 14-fold) and detoxication (dearylation) (2- to 4-fold), as well as concentrations of P450 (7-fold) and protein (2-fold), were observed between neonate and adult hepatic microsomes. Microsomal pentoxyresorufin O-dealkylase activity followed a developmental pattern similar to desulfuration and dearylation, displaying a 16-fold increase between neonates and adults. However, microsomal ethoxyresorufin O-deethylase activity increased until 21 days of age, displaying a 16-fold increase, then decreased in adulthood to a level 10-fold higher than neonates. These results indicate that target enzyme sensitivity is not responsible for age-related toxicity differences, nor is the potential for hepatic bioactivation, whereas lower levels of hepatic aliesterase-mediated protection and P450-mediated dearylation probably contribute significantly to the greater sensitivity of juveniles to phosphorothionate toxicity. 相似文献
109.
110.
PURPOSE: To evaluate and compare the microleakage of amalgam restorations lined with four different liners. MATERIALS AND METHODS: Cylindrical occlusal cavities were prepared in extracted human molars and the teeth were then divided into four groups and lined with one of four liners: Amalcoden, AM (glass-metal ionomer), FujiDuet, FD (glass ionomer), Amalgambond, AB (adhesive resin), or copal varnish, CV. Each cavity was then restored with a high-copper amalgam alloy and aged for 7 days in 37 degrees C distilled water. The specimens were then thermocycled for 300 cycles followed by immersion in 0.5% basic fuchsin dye solution for 24 hours. The teeth were then embedded in resin, sectioned, and dye penetration at the tooth/amalgam interface evaluated microscopically at x 100 and scored from 0 to 4 (0 = no leakage and 4 = greatest leakage). RESULTS: The median values were: AM = 1.0; FD = 0.5; AB = 1.1; and CV = 4.0. Statistical analysis using Kruskal-Wallis and Mann-Whitney U indicated no significant differences between AM and AB or FD and AB. CV was however, significantly worse at P < 0.01. 相似文献