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101.
Microfluidic devices have been established as useful platforms for cell culture for a broad range of applications, but challenges associated with controlling gradients of oxygen and other soluble factors and hemodynamic shear forces in small, confined channels have emerged. For instance, simple microfluidic constructs comprising a single cell culture compartment in a dynamic flow condition must handle tradeoffs between sustaining oxygen delivery and limiting hemodynamic shear forces imparted to the cells. These tradeoffs present significant difficulties in the culture of mesenchymal stem cells (MSCs), where shear is known to regulate signaling, proliferation, and expression. Several approaches designed to shield cells in microfluidic devices from excessive shear while maintaining sufficient oxygen concentrations and transport have been reported. Here we present the relationship between oxygen transport and shear in a "membrane bilayer" microfluidic device, in which soluble factors are delivered to a cell population by means of flow through a proximate channel separated from the culture channel by a membrane. We present an analytical model that describes the characteristics of this device and its ability to independently modulate oxygen delivery and hemodynamic shear imparted to the cultured cells. This bilayer configuration provides a more uniform oxygen concentration profile that is possible in a single-channel system, and it enables independent tuning of oxygen transport and shear parameters to meet requirements for MSCs and other cells known to be sensitive to hemodynamic shear stresses. 相似文献
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Guided by social cognitive theory (SCT), we investigated whether exercise self-regulatory efficacy beliefs can be activated nonconsciously in individuals experienced and inexperienced in exercise self-regulation, and whether these beliefs are automatically associated with exercise self-regulation processes. The study used a 2 (Exercise Self-Regulation Experience Group) × 3 (Prime Condition) between-subjects design in which individuals experienced and inexperienced in exercise self-regulation were randomly assigned to receive subliminal, supraliminal, or no priming of exercise self-regulatory efficacy beliefs. Participants completed hypothetical diary entries, which were assessed for exercise self-regulatory efficacy and self-regulation expressions using content analyses with a SCT coding system and the Linguistic Inquiry and Word Count (LIWC) text analysis program. For both exercise self-regulation experience groups, self-efficacy priming led to more expressions of low exercise self-regulatory efficacy and dysfunctional exercise self-regulation strategies compared with the control prime. For participants experienced in exercise self-regulation, supraliminal priming (vs. control priming) led to more expressions of high exercise self-regulatory efficacy and functional exercise self-regulation strategies. For the experienced groups, priming led to automaticity of exercise expressions compared with the control condition. For inexperienced participants in the subliminal prime condition, priming led to automaticity of self-regulatory efficacy beliefs and work-related goals compared with the control condition. Automatic activation of exercise self-regulatory efficacy and exercise self-regulation processes suggests that self-regulation of exercise behavior can occur nonconsciously. 相似文献
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Michael J. Lichtenstein Steven V. Owen Cheryl L. Blalock Yan Liu Kacy A. Ramirez Linda A. Pruski Carolyn E. Marshall Mary Anne Toepperwein 《科学教学研究杂志》2008,45(5):600-616
The central purposes of this study were to review the development and evolution of the Scientific Attitude Inventory (SAI) and then reevaluate the psychometric properties of the revised form of the SAI, the Scientific Attitude Inventory II (SAI‐II). The SAI‐II was administered to a convenience sample of 543 middle and high school students from five teachers in four schools in four school districts in San Antonio, Texas, at the beginning of the 2004–2005 school year. Confirmatory factor analysis on the full data set failed to support the existence of a 12‐factor structure (as proposed by the scale developers) or a one‐factor structure. The data were then randomly divided into exploratory [exploratory factor analysis (EFA)] validation and confirmatory [confirmatory factor analysis (CFA)] cross‐validation sets. Exploratory and confirmatory models yielded a three‐factor solution that did not fit the data well [χ2 (321) = 646, p < .001; RMSEA = .061 (.90 CI = .054–.068); and CFI = .81]. The three factors were labeled “Science is About Understanding and Explaining” (13 items), “Science is Rigid” (6 items), and “I Want to Be a Scientist” (8 items). The α‐coefficients for these three factors ranged from 0.59 to 0.85. Whether these identified subscales are valid will require independent investigation. In this sample, and consistent with prior publications, the SAI‐II in its current form did not have satisfactory psychometric properties and cannot be recommended for further use. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 600–616, 2008 相似文献
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