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111.
112.
The current practice for the design of squeezed branch piles is mainly based on the calculated bearing capacity of circular piles. Insufficient considerations of the load-transfer mechanism, branch effect and failure mechanism, as well as overreliance on pile load tests, have led to conservative designs and limited application. This study performs full-scale field load tests on instrumented squeezed branch piles and shows that the shaft force curves have obvious drop steps at the branch position, indicating that the branches can effectively share the pile top load. The effects of branch position, spacing, number and diameter on the pile bearing capacity are analyzed numerically. The numerical results indicate that the squeezed branch piles have two types of failure mechanisms, i.e. individual branch failure mechanism and cylindrical failure mechanism. Further research should focus on the development of the calculation method to determine the bearing capacities of squeezed branch piles considering these two failure mechanisms. 相似文献
113.
《Soils and Foundations》2022,62(3):101150
The circular helicoid pile (CH pile) is a new type of special-shaped pile that has been developed in Japan and South Korea in the past decade and has been widely used in the fields of construction, transportation, natural energy and agriculture due to its excellent compressive and pullout bearing performances. Consequently, this new type of pile has good engineering application prospects. However, as an innovative engineering structure, the CH pile is not widely known by geotechnical engineers worldwide. The geometric structure of the CH pile is similar to a circular helicoid in differential geometry. Therefore, the pile-soil interaction problem cannot be reduced to a plane strain problem or an axisymmetric problem in theoretical research. In view of this, dry silica sand was used as the model foundation in this study, and a model test device and method that can effectively reflect the installation process and loading-bearing service state of CH piles were developed. Under different installation methods, pile structures and foundation soil conditions, 90 model tests were carried out to evaluate the engineering performances of CH piles during the whole process of installation and bearing, including the installation performances during the installation process, the compressive bearing performances under axial compressive loading and the pullout bearing performances under axial pullout loading. Compared with steel sheet piles and steel pipe piles, CH piles have better engineering performance and more economic benefits from the aspects of installation, construction, recycling, timeliness of engineering application, and the relative relationship between bearing capacity and pile mass. 相似文献
114.
用边界元法分析水润滑扇形瓦推力轴承的润滑性能,将雷诺方程转化为类似泊松方程的形式,采用边界元法求解该方程,研制了一套C++计算程序,得到多组轴瓦参数下的水膜厚度、压力分布和相关润滑性能,可以显著降低代数方程组的阶数,从而减少计算所需时间,并可提高计算精度。研究表明瓦块张角和瓦块倾角对最小水膜厚度、最大水膜压力、摩擦功耗、压力中心位置和进水口流量有不同程度的影响,该研究将有助于合理的设计水润滑扇形瓦推力轴承的轴瓦参数。 相似文献
115.
高速主轴在工作过程中易受热变形影响数控机床加工精度,而角接触球轴承作为高速主轴的支承件发挥着巨大的作用。根据Hertz接触力理论,结合角接触球轴承受力平衡以及位移方程,建立角接触球轴承对主轴位移影响的分析模型,然后通过对比用模型计算的轴套位移值与用位移传感器测得的轴套位移值来进行验证;最后分析计算不同转速下轴承内外圈接触力和轴承刚度的影响,以及不同转速下对轴套和主轴位移产生的影响。利用该模型可以设置合理的预紧载荷以及主轴转速,提高轴系的运动定位精度,为轴承预紧量的施加、工作预紧载荷的调整及预紧装置的设计提供参考,弱化轴承塑性变形导致的热变形,从而降低对高速主轴变形位移产生的影响。 相似文献
116.
Comprehensive results from laboratory model tests on strip footings supported on the geocell and planar reinforced sand beds with the same characteristics of geotextile are presented. The various parameters studied in this testing program include the reinforcement width, the number of planar layers of geotextile and height of the geocell below the footing base. Contrary to other researches, the performance of the geocell and planar reinforcement is investigated at the range of low to medium settlement level, similar to those of interest in practice. The results show that the efficiency of reinforcement was decreased by increasing the number of the planar reinforcement layers, the height of the geocell reinforcement and the reinforcement width. For the same mass of geotextile material used in the tests at the settlement level of 4%, the maximum improvement in bearing capacity (IF) and percentage reduction in footing settlement (PRS) were obtained as 2.73 and 63% with the provision of geocell, respectively, while these values compare with 1.88 and 47% for the equivalent planar reinforcement. On the whole, the results indicate that, for the same quantity of geotextile material, the geocell reinforcement system behaves much stiffer and carries greater loading and settles less than does the equivalent planar reinforcement system. Therefore, a specified improvement in bearing pressure and footing settlement can be achieved using a lesser quantity of geocell material compared to planar geotextile. 相似文献
117.
The paper presents the results of laboratory model tests on bearing capacity behaviour of a strip footing resting on the top of a geogrid reinforced flyash slope. A series of model footing tests covering a wide range of boundary conditions, including unreinforced cases were conducted by varying parameters such as location and depth of embedment of single geogrid layer, number of geogrid layers, location of footing relative to the slope crest, slope angles and width of footing. The results of the investigation indicate that both the pressure–settlement behaviour and the ultimate bearing capacity of footing resting on the top of a flyash slope can be enhanced by the presence of reinforcing layers. However the efficiency of flyash geogrid system increases with the increasing number of geogrid layers and edge distance of footing from the slope. Based on experimental results critical values of geogrid parameters for maximum reinforcing effects are established. Experimental results obtained from a series of model tests have been presented and discussed in the paper. 相似文献
118.
铁路桥梁铅芯橡胶支座桥梁减隔震应用研究 总被引:1,自引:0,他引:1
给出了铅芯橡胶支座滞回特性的等效线性模型以及支座设计参数的计算方法和取值范围,建立了隔震多跨简支梁桥体系的全桥模型,通过改变地震激励、地震动强度和车速等参数,对隔震桥梁在不同激励下的响应规律和特点进行了系统的研究,分析了隔震效果。 相似文献
119.
120.