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排序方式: 共有1271条查询结果,搜索用时 78 毫秒
81.
82.
By employing a calibrated and tested computer model, simulations of ceiling heat transfer in typical residential attics located in 12 locations across the United States were obtained to study the sensitivity of attic radiant barrier performance to local climate parameters. For each location, the net ceiling heat flux over the summer cooling season was computed for an attic with and for an attic without an installed radiant barrier. The net reduction of heat flux induced by the radiant barrier was computed and then related to climate variables. Among the local environmental parameters, the local ambient air temperature, local ambient humidity, and latitude had significant effects on the performance of radiant barriers. It was concluded that the installation of radiant barriers would be most beneficial in regions with high outdoor air temperatures and high relative humidity. 相似文献
83.
Kenneth S. Kaminsky 《技术计量学》2013,55(2):251-254
We construct confidence intervals for the ratio of two exponential scale parameters and present a test of hypothesis concerning these parameters. The procedures are based on the selection of subsets of two independent ordered samples from exponential populations. The discussion centers around the distribution of the ratio of the BLUE's (the ABLE's in large samples) of these parameters, and a simple approximation to that distribution. Optimal selection of the data is discussed. In an example, the power function of the proposed test is compared with the power function of the same test based on complete samples. 相似文献
84.
R. G. Krutchkoff 《技术计量学》2013,55(3):425-439
The Classical and Inverse least squares methods of linear calibration are compared by Monte Carlo methods. The Inverse approach is found to be superior to the Classical approach from a mean squared error point of view. 相似文献
85.
Zihong Liu Tommy E. Cousins John J. Lesko Elisa D. Sotelino 《Canadian Metallurgical Quarterly》2008,12(6):660-668
No appropriate provisions from either AASHTO Standard (2002) or AASHTO LRFD (2004) bridge design specifications are available for the design of fiber-reinforced polymer (FRP)-deck-on-steel-superstructure bridges. In this research, a parametric study using the finite-element method (FEM) is conducted to examine two design issues concerning the design of FRP-deck-on-steel-superstructure bridges, namely deck relative deflection and load distribution factor (LDF). Results show that the strip method specified in AASHTO LRFD specification as an approximate method of analysis, can also be applied to FRP decks as a practical method. However, different strip width equations have to be determined by either FEM or experimental methods for different types of FRP decks. In this study, one such equation has been derived for the Strongwell deck. In addition, both FEM results and experimental measurements show that the AASHTO LDF equations for glued laminated timber decks on steel stringers provide good estimations of LDF for FRP-deck-on-steel-superstructure bridges. Finally, it is found that the lever rule can be used as an appropriately conservative design method to predict the LDF of FRP-deck-on-steel-superstructure bridges. 相似文献
86.
An investigation on stiffened isotropic and composite plates has been conducted to determine the geometric and material parameters for the plate, as well as the stiffener from experimental modal data and finite element predictions using a genetic algorithm (GA). The problem is formulated as a global minimization of the error function defined by the difference in undamped eigenvalues and eigenvectors, as predicted from the finite-element modeling to that obtained experimentally. The parameter estimation problem is solved using a GA implementing selection, crossover, and mutation operators to obtain the global minimum solution. Because stiffeners contribute substantially to the overall rigidity of the plate assembly, their position, physical properties, and orientation create considerable variation of the modal properties, as compared to the bare plate with similar construction. This makes each of the stiffened plate identification problems rather unique. GAs have been the subject of considerable interest in providing a robust search procedure for a global optimum solution for such difficult minimization problems. The method is demonstrated on a few simulated examples on stiffened plates to investigate the uniqueness and convergence of results. The methodology, although slow in execution, is found to be very robust, even in the presence of noise, for isolating interesting zones of the search space. Unlike many traditional optimization techniques, it does not get stuck at a particular local minimum due to its parallelism. 相似文献
87.
Chantal Seignez Anna Atti Nevenka Adler Paul Péringer 《Canadian Metallurgical Quarterly》2002,128(4):360-366
In this paper the effect of operating parameters on biotrickling filter performance degrading chlorobenzene and o-dichlorobenzene mixture were studied. The large laboratory scale biofilter, total volume 40 L, filled with inert packing material was used. The biomass adaptation and cultivation were performed in a batch fermentor and were used to inoculate the biotrickling filter. After a starting period, the influence of the substrate load increase, liquid recirculation flow rate, and empty bed retention time on elimination capacity and removal efficiency were found. The most important recirculation liquid parameters were analyzed every day, that is: concentration of metabolites, dissolved organic carbon, nitrate, chloride, and biomass. A good correlation was found between intermediate concentration and the removal efficiency of the biotrickling filter. The measurements of the absorbance, very easy and rapid, can be used as a control parameter of the biofiltration efficiency. 相似文献
88.
89.
基于Kriging代理模型的注塑件残余应力优化分析 总被引:1,自引:0,他引:1
以注塑成型制品中脱模后的最大Mises-Hencky残余应力为目标函数,运用基于Kriging代理模型及EI加点准则的序列优化方法,对聚碳酸酯材料制品进行了工艺参数(包括熔体温度、模具温度、注射速率、保压压力及保压时间)优化。算例结果表明,所提出方法可以有效地降低注塑件内的最大Mises-Hencky残余应力。在此基础上对充填阶段进行深入分析,用贝塞尔曲线控制方式代替常规的常速率充填控制方式,进一步降低了制件内的残余应力。 相似文献
90.
通过室内物理模拟实验,研究了注入方式对采收率的影响。研究表明,从注聚开始到调剖剂注入结束,含水率明显下降,在聚驱阶段采收率提高幅度较大,为7.27个百分点;总的提高幅度为16.36%,最终采收率为65.71%,与前置调剖实验相比,两者的水驱采收率分别为49.35%和50.68%两者相差不大,但是总提高幅度比前置调剖要低0.9个百分点,最终采收率相差2.23个百分点。说明前置调剖更有利于提高采收率。从综合成本及经济效益因素来考虑,最佳注入方式选用前置调剖段塞0.05 PV。最佳候凝时间为7~10 d。 相似文献