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Danielle D. Kleinhans John J. Myers Antonio Nanni 《Canadian Metallurgical Quarterly》2007,11(5):545-552
A primary means of demonstrating the feasibility and effectiveness of fiber-reinforced polymer (FRP) composite bridge materials is via in situ bridge load testing. For this study, the prescribed or assumed design factors for each of the study bridges were compared to those exhibited by the performance of the bridge. Specifically, the wheel load distribution factors and impact factors as defined by AASHTO were considered in order to assess the load transfer and distribution in structures utilizing FRP panels. The in situ testing configurations for the study bridges are outlined, including the truck and instrumentation placement to obtain the desired information. Furthermore, comparisons were drawn between the design values for deflection and those experienced by the structures during testing. It was found that although the deflections exhibited by the bridges were well within the design limits, further research is needed to be able to prescribe bridge design factors for FRP panels. 相似文献
995.
To identify the transition from continuous to discontinuous modes in the failure evolution of quasibrittle materials under impact, a coupled rate-dependent damage and plasticity model is developed within the thermodynamics framework. Due to the simplicity in model formulation, a continuum tangent stiffness tensor could be obtained for discontinuous bifurcation analysis, and the model parameters could be calibrated from split Hopkins pressure bar experimental data available. The coupled rate-dependent model could describe not only the pressure-dependent hardening/softening response but also the degradation of material stiffness under impact. A geometric criterion with a corresponding solution scheme is presented to explore the rate-dependent transition from continuous to discontinuous failure modes in the Mohr coordinates. The uniaxial compressive loading path is considered to illustrate the loading rate effect on the critical localization orientation and hardening parameters. It appears from the preliminary results that the coupled rate-dependent local continuum model might be combined with a decohesion model via discontinuous bifurcation analysis so that large-scale simulation of failure evolution could be performed without invoking higher-order spatial terms in the stress-strain space. 相似文献
996.
When localized transverse loading is applied to a sandwich structure, the facesheet locally deflects and the core crushes. A residual dent induced by the core crushing significantly degrades the mechanical properties of the sandwich structure. In a previous paper, the authors established a “segment-wise model” for theoretical simulation of barely visible indentation damage in honeycomb sandwich beams with composite facesheets. Honeycomb sandwich beam was divided into many segments based on the periodic shape of the honeycomb and complicated through-thickness characteristics of the core were integrated into each segment. In this paper, the new model is validated by experiments using specimens with different types of honeycomb cores. In addition, the damage growth mechanism under indentation load was clarified from the viewpoint of the reaction force from the core to the facesheet. The applicability of the model to other types of core materials is also discussed. 相似文献
997.
Campbell Susan B.; Matestic Patricia; von Stauffenberg Camilla; Mohan Roli; Kirchner Thomas 《Canadian Metallurgical Quarterly》2007,43(5):1202
Using data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development, the authors modeled trajectories of maternal depressive symptoms from infant age 1 month to 7 years. The authors identified 6 trajectories of maternal depressive symptoms: high-chronic, moderate-increasing, high-decreasing, intermittent, moderate-stable, and low-stable. Women on these depression trajectories varied in sociodemographic risk and in changes in observed maternal sensitivity over time. Maternal sensitivity was generally higher and increased when depressive symptoms were low; sensitivity was lower and decreased when depressive symptoms were either high or increasing. Child outcomes at 1st grade were examined by trajectory group. The authors discuss the complexity of disentangling maternal symptoms from maternal sensitivity and sociodemographic risk when predicting children's functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
Taylor Steven; Zvolensky Michael J.; Cox Brian J.; Deacon Brett; Heimberg Richard G.; Ledley Deborah Roth; Abramowitz Jonathan S.; Holaway Robert M.; Sandin Bonifacio; Stewart Sherry H.; Coles Meredith; Eng Winnie; Daly Erin S.; Arrindell Willem A.; Bouvard Martine; Cardenas Samuel Jurado 《Canadian Metallurgical Quarterly》2007,19(2):176
Accumulating evidence suggests that anxiety sensitivity (fear of arousal-related sensations) plays an important role in many clinical conditions, particularly anxiety disorders. Research has increasingly focused on how the basic dimensions of anxiety sensitivity are related to various forms of psychopathology. Such work has been hampered because the original measure--the Anxiety Sensitivity Index (ASI)--was not designed to be multidimensional. Subsequently developed multidimensional measures have unstable factor structures or measure only a subset of the most widely replicated factors. Therefore, the authors developed, via factor analysis of responses from U.S. and Canadian nonclinical participants (n = 2,361), an 18-item measure, the ASI-3, which assesses the 3 factors best replicated in previous research: Physical, Cognitive, and Social Concerns. Factorial validity of the ASI-3 was supported by confirmatory factor analyses of 6 replication samples, including nonclinical samples from the United States and Canada, France, Mexico, the Netherlands, and Spain (n = 4,494) and a clinical sample from the United States and Canada (n = 390). The ASI-3 displayed generally good performance on other indices of reliability and validity, along with evidence of improved psychometric properties over the original ASI. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
Harrison Emily L. R.; Marczinski Cecile A.; Fillmore Mark T. 《Canadian Metallurgical Quarterly》2007,15(6):588
[Correction Notice: An erratum for this article was reported in Vol 16(2) of Experimental and Clinical Psychopharmacology (see record 2008-03846-009). The correct title of the article should read "Driver training conditions affect sensitivity to the impairing effects of alcohol on a simulated driving test".] Research shows that prior behavioral training in a challenging environment reduces alcohol-induced impairment on simple psychomotor tasks. However, no studies have examined if this relationship generalizes to driving performance. The present study examined simulated driving performance and tested the hypothesis that a challenging training history would protect against the impairing effects of alcohol on driving performance. The challenging training history involved driving in a visually-impoverished environment. Thirty adults were randomly assigned to one of three groups. Two groups were tested under alcohol (0.65 g/kg) after prior experience performing the task under either a visually-impoverished environment or a normal visual environment. The remaining group served as a control and was trained and tested under the visually-impoverished condition environment. Results showed that individuals trained in the impoverished environment displayed sober levels of performance when their performance was subsequently tested under alcohol. By contrast, volunteers trained in a normal environment showed impairment under alcohol. The findings suggest that differences in driving training history can affect a driver's sensitivity to the impairing effects of alcohol. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.
提出一种设计永磁型核磁共振磁体磁极形状的优化方法,该方法用水平集函数隐式地描述材料界面,通过连续性形状灵敏度分析,可得到隐式描述的材料界面上各点的演化速度,而水平集的演化由哈密尔顿-雅可比方程控制,该方程可通过有限差分法求解。设计结果表明了该优化算法的有效性。 相似文献