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1.
To prepare high‐performance clean fracturing fluids, cationic surfactants with a Gemini structure were synthesized as thickening agents. Distinct elastic characteristics at a sweep frequency of 0.1–10 Hz and shear resistance at high temperature were shown. Viscosity remained at about 150 mPa s after shearing for 60 min at 140 °C and 170 s?1. Stability investigation on cationic Gemini surfactant solution revealed that both viscosity and viscoelasticity were greatly affected by the surfactant concentration, temperature, and the amount of inorganic salt (potassium chloride). Complete formulation of a surfactant micelle structure in an aqueous solution requires a certain amount of time.  相似文献   
2.
现有减震设计方法需进行繁琐的迭代,其效率有待提高。基于剪力比的概念,采用黏弹性阻尼腋撑,设置罕遇地震下腋撑与框架结构的耗能比,提出了基于剪力比的黏弹性阻尼腋撑-RC框架结构抗震设计方法。选取7条地震动记录,根据不同剪力比 α 对6层、9层、12层模型设置不同参数的腋撑,进行罕遇地震下弹塑性动力时程分析。研究了腋撑耗能占地震输入结构总能量的关系,并将各模型最大层间位移角与GB 50011—2010《建筑抗震设计规范》的规定值进行了对比。从层间位移角、层剪力、顶层最大位移值、顶层峰值加速度等方面比较了结构的减震效果。研究结果表明:对于高40m以下的框架结构,耗能比为0.6时,剪力比 α 的合理取值范围在0.10~0.20之间;剪力比α取0.15时,RC框架结构的最大层间位移角、顶层最大位移值均减少34%~45%,层剪力、顶层加速度峰值均减少19%~23%。  相似文献   
3.
抵抗地震荷载时实现“强节点弱构件”的破坏模式是框架结构可发挥其良好抗震性能的前提条件,为确保“强节点弱构件”破坏模式的实现提出了加装扇形铅黏弹阻尼器(SLVD)保护节点区的消能减震技术方案。为研究加装SLVD对框架节点区的保护效果及对整体结构抗震性能的影响,设计并制作尺寸、材料及配筋完全相同的二层二跨普通现浇混凝土框架试件和加装SLVD的现浇混凝土消能减震框架试件各一榀。通过拟静力试验,对比分析两种框架的破坏模式、滞回性能、骨架曲线、强度和刚度退化、耗能特性等变化情况。试验结果表明:普通现浇框架的节点区发生严重剪切破坏,现浇混凝土消能减震框架节点区没有发生严重破坏;SLVD起到良好的耗能保护作用,延缓并控制了节点核心区裂缝的出现与开展,减轻了整体结构的损伤;SLVD在框架中起到“耗能腋撑”作用,提高了框架结构的承载能力、抗侧刚度和耗能能力;加装SLVD改变了框架结构节点区附近的内力分布及传力路径,减小了传递到节点区的剪力与弯矩,但同时改变了梁柱构件的内力分布,在消能减震子结构设计时应予以考虑。节点区加装SLVD有利于框架结构“强节点弱构件”抗震设计理念的实现,现浇混凝土消能减震框架的抗震性能优于普通现浇混凝土框架。  相似文献   
4.
为了解决黏弹性人工边界在实际应用过程中前处理时间长、不易实现等不足之处,提出了基于薄层单元的黏弹性人工边界的模拟方法。利用单元矩阵等效原理,采用薄层单元构造了等效黏弹性边界单元,并通过在大型通用有限元软件MSC Marc中设置等效黏弹性边界单元的参数属性,实现了黏弹性人工边界的模拟。三维均匀弹性半空间算例和某混凝土重力坝工程实例结果表明:采用等效黏弹性边界单元得到的计算结果与理论解、基于黏弹性人工边界的计算值非常相近,相对误差不超过1%。因此,采用薄层单元的模拟的黏弹性人工边界具有足够的精度,且施加方便,这为实际工程进行抗震分析提供了简便且精确的方法。  相似文献   
5.
In this study, the analysis of nonlinear stability with viscoelastic ferromagnetic fluids as working media is performed by finite-amplitude perturbations. The solution of the resulting nonautonomous system of the Lorenz model (generalized Khayat–Lorenz model of four modes) is obtained numerically to measure the amount of heat transport. The effects of elastic parameters, Prandtl number, modulation parameters, buoyancy magnetic parameter, and nonbuoyancy magnetic parameter on heat transport are studied. Heat transport is quantified through the average Nusselt number, which is determined by solving the scaled Lorenz model. As limiting cases of the study, the results of Newtonian, Maxwell, Rivlin–Ericksen fluids are determined. The results obtained have been presented graphically.  相似文献   
6.
商峰  周虎 《建筑材料学报》2022,25(2):214-220
从早龄期开始采用超声波对大尺寸自密实混凝土和堆石混凝土进行了对比测试,并基于黏弹性介质波动理论从纵波波速测量结果中分离出材料的黏性特征参数,用于分析堆石混凝土的浇筑状态,评价堆石混凝土的施工质量.结果表明:由于堆石混凝土内部结构复杂,仅依靠代表性体积单元的超声波速均值和变异系数难以对堆石混凝土的浇筑质量做出可靠的评价,因而需要进行高密度的分层检测;应用材料的黏性特征参数进行分析判断时,有可能采用较少的测线完成检测,这在工程实践中是更具有应用价值的方法.应用早龄期超声测试的方法有助于克服由于代表性单元尺寸过大给堆石混凝土工程质量评价带来的困难.  相似文献   
7.
In this paper, analytical estimation of energy dissipations, such as viscous, Joulian, and Darcy dissipation of viscoelastic flow phenomena over a deformable surface has been presented. This supplement to the study of many transport processes, which occur in nature, and various experimental setups that are driven or modified by the composition of the various flow characteristics and material or phase constitution. These processes are very important and have received considerable attention in the literature. The estimation of dissipative energy in the process of transport energy is an important phenomenon to investigate. The present analysis is carried out on steady MHD viscoelastic liquid due to deformable domains. Moreover, the impact of internal heat sources and prescribed thermal conditions, such as surface temperature and heat flux, are carefully studied. Analytical solutions to governing equations are obtained with the help of Kummer's function. The solutions are presented graphically as well as in tables to estimate the energy losses and their effects on transport processes, which serve as the salient features of the current analysis. The outcomes serve as a guideline due to the process of transport properties as per the design requirements. Looking into the current scenario, dissipative heat energies have several applications in industries and technological processes, such as electric heaters, fuses, food processing, and several others.  相似文献   
8.
A Gemini zwitterionic viscoelastic surfactant named self diverting acid - gemini sulfonated surfactant (SDA-GS), which has double quaternary ammonium groups, double sulfonate groups, and two hydrophobic tails, was synthesized from oleylamidopropyl dimethylamine, 1,3-propanesultone, and 2, 2-bis(bromomethyl)propane-1, 3-diol. The viscosity of an SDA-GS aqueous solution varies with acid and calcium chloride concentrations. With a decrease in the HCl concentration, the viscosity of the acid solution prepared with SDA-GS increases to a maximum value, followed by a decrease, which results from the aggregation of the surfactant into wormlike micelles and the following disaggregation. Calcium ions generated by the reaction of acid and calcium carbonate can enhance the aggregation of the surfactant to increase the peak viscosity of the acid solution. The peak viscosity of the acid solution prepared by 5 wt.% SDA-GS without calcium ions could only reach 73.2 mPa.s when the HCl concentration was 4 wt.%, but that of the acid solution with calcium carbonate powder added could reach over 200 mPa.s when the HCl concentration was consumed to 4 wt.% and the calcium chloride concentration 21.6 wt.%. The viscoelastic measurements proved that calcium ions can drive the growth of the wormlike micelle. The acid and Ca2+ response of SDA-GS can be applied in self-diverting acid to improve the acid displacement in the heterogeneous reservoir. Experimental evaluation showed that the acid solution prepared by SDA-GS and the selected corrosion inhibitor showed a good corrosion inhibition performance and a viscosity variation that makes it an efficient self-diverting acid. The spent acid (21.6 wt.%) with 4 wt.% HCl retained high viscosity over 80 mPa.s at a 170 s−1 shearing rate and at 120°C after 90 min. The parallel core flood tests to simulate in situ application of SDA-GS acid showed that the permeability improvement ratios (K1/K0) of the cores could reach 182.3 and 278.4 at 60 and 90°C, respectively.  相似文献   
9.
The interrelation between crosslinking and morphology is investigated for an immiscible blend of polylactic acid (PLA) and acrylic rubber (ACM). The blends are prepared by solution mixing and static crosslinking is used to avoid the simultaneous effect of the flow field that occurs in dynamic vulcanization. It is carried out at different temperatures, times, and curing agent contents. Scanning force microscopy (SFM) and polarized optical microscopy are used to determine the morphology of the blends. The chemical interactions and viscoelastic properties of the blends after crosslinking are also studied using infrared spectroscopy and rheological tests, respectively. Before crosslinking, SFM shows matrix‐droplet morphology for the samples that it is retained after that for the blend with 30 wt% ACM; however, it is changed to cocontinuous one in the blend with 50 wt% ACM. Partially, grafting of PLA on the crosslinked ACM is confirmed by Fourier transform infrared spectroscopy. The rheological results show that the incorporation of ACM to the PLA slows down the chain relaxation and vulcanization intensifies this effect. A model is proposed to explain the morphology evolution during static crosslinking of an immiscible blend.  相似文献   
10.
为研究玻璃纤维增强环氧树脂基复合材料的非线性粘弹性响应,采用Schapery模型描述复合材料的非线性粘弹性,并在不同应力水平下分别对[90]16横向试样和[±45]4S面内剪切试样开展拉伸蠕变-回复试验. 根据试验观察到的残余粘塑性应变现象,在Schapery模型中引入粘塑性应变分量,提出一种基于解析法的非线性参数辨识方法,获得了Schapery非线性参数g0, g1, g2和aσ随应力的变化规律. 结果表明:当施加的横向拉伸应力大于横向拉伸强度的53%,面内剪切应力大于剪切强度的31%时,玻纤/环氧复合材料表现出明显的非线性粘弹性;横向上,非线性参数g0T和g2T与应力无关,g1T随应力线性增加,aσT随应力线性降低;面内剪切方向上,非线性参数g0S和g2S随应力呈指数增加,g1S随应力线性增加,aσS则随应力线性降低. 与传统的非线性参数辨识方法相比,所提出的参数辨识方法能方便准确地获取非线性参数随应力的变化规律.   相似文献   
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