全文获取类型
收费全文 | 11649篇 |
免费 | 703篇 |
国内免费 | 677篇 |
专业分类
电工技术 | 600篇 |
技术理论 | 5篇 |
综合类 | 1307篇 |
化学工业 | 1299篇 |
金属工艺 | 355篇 |
机械仪表 | 560篇 |
建筑科学 | 1309篇 |
矿业工程 | 529篇 |
能源动力 | 339篇 |
轻工业 | 436篇 |
水利工程 | 329篇 |
石油天然气 | 377篇 |
武器工业 | 161篇 |
无线电 | 740篇 |
一般工业技术 | 1266篇 |
冶金工业 | 469篇 |
原子能技术 | 145篇 |
自动化技术 | 2803篇 |
出版年
2024年 | 24篇 |
2023年 | 152篇 |
2022年 | 416篇 |
2021年 | 445篇 |
2020年 | 301篇 |
2019年 | 273篇 |
2018年 | 262篇 |
2017年 | 305篇 |
2016年 | 335篇 |
2015年 | 333篇 |
2014年 | 390篇 |
2013年 | 734篇 |
2012年 | 470篇 |
2011年 | 747篇 |
2010年 | 469篇 |
2009年 | 610篇 |
2008年 | 711篇 |
2007年 | 685篇 |
2006年 | 590篇 |
2005年 | 466篇 |
2004年 | 421篇 |
2003年 | 501篇 |
2002年 | 730篇 |
2001年 | 659篇 |
2000年 | 785篇 |
1999年 | 212篇 |
1998年 | 166篇 |
1997年 | 133篇 |
1996年 | 145篇 |
1995年 | 105篇 |
1994年 | 114篇 |
1993年 | 42篇 |
1992年 | 61篇 |
1991年 | 40篇 |
1990年 | 38篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1960年 | 3篇 |
1958年 | 3篇 |
1957年 | 6篇 |
1955年 | 4篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Hydrogel-based nanofibers or vice versa are a relatively new class of nanomaterials, in which hydrogels are structured in nanofibrous form. Structure and size of the material directly governs its functionality, therefore, in hydrogel science, the nanofibrous form of hydrogels enables its usage in targeted applications. Hydrogel nanofiber system combines the desirable properties of both hydrogel and nanofiber like flexibility, soft consistency, elasticity, and biocompatibility due to high water content, large surface area to volume ratio, low density, small pore size and interconnected pores, high stiffness, tensile strength, and surface functionality. Swelling behavior is a critical property of hydrogels that is significantly increased in hydrogel nanofibers due to their small size. Electrospinning is the most popular method to fabricate “hydrogel nanofibers,” while other processes like self-assembly, solution blowing and template synthesis also exist. Merging the characteristics of both hydrogels and nanofibers in one system allows applications in drug delivery, tissue engineering, actuation, wound dressing, photoluminescence, light-addressable potentiometric sensor (LAPS), waterproof breathable membranes, and enzymatic immobilization. Treatment of wastewater, detection, and adsorption of metal ions are also emerging applications. In this review paper, we intend to summarize in detail about electrospun “hydrogel nanofiber” in relation to its synthesis, properties, and applications. 相似文献
2.
This paper introduces a simultaneous process optimization and heat integration approach, which can be used directly with the rigorous models in process simulators. In this approach, the overall process is optimized utilizing external derivative-free optimizers, which interact directly with the process simulation. The heat integration subproblem is formulated as an LP model and solved simultaneously during optimization of the flowsheet to update the minimum utility and heat exchanger area targets. A piecewise linear approximation for the composite curve is applied to obtain more accurate heat integration results. This paper describes the application of this simultaneous approach for three cases: a recycle process, a separation process and a power plant with carbon capture. Case study results indicate that this simultaneous approach is relatively easy to implement and achieves higher profit and lower operating cost and, in the case of the power plant example, higher net efficiency than the sequential approach. 相似文献
3.
In different computer models, shape is represented using different methodologies, to varying degrees of precision. This paper examines two approaches to shape representation, and their effects on accuracy in the context of cylindrical particle packing. Two discrete element method (DEM) based software packages are used. A X-ray CT scan of a packed bed provides the experimental measurements for comparison. Eight sphere-composite representations of the same cylindrical pellet were tested. Two of these gave results that quantitatively follow experimental measurements. A range of factors that in theory could affect accuracy of the simulation results are examined, including edge roundedness, surface roughness and restitutional behaviour as a function of sphere-composite representations. The conclusion is that, for packing at least, matching the object's overall shape and dimensions is not enough. Only when a high enough resolution is applied to corners and edges, could the sphere-composite approach possibly match the experimental data quantitatively. 相似文献
4.
The separation of azeotropes has substantial energy and investment costs, and the available methods require high capital costs for reconstruction of process plants. As an alternative, a semicontinuous configuration that utilizes an existing plant with minor modifications has been explored. In this paper, a semicontinuous, heterogeneous azeotropic distillation process is proposed and acetic acid dehydration process is used as a case study. To carry out the simulation work, Aspen HYSYS® simulation software is used along with MATLAB® and an interface program to handle the mode-transition of the semicontinuous process. Sensitivity analyses on operating parameters are performed to identify the process limits. Comparisons are made to conventional heterogeneous azeotropic distillation, and dividing-wall distillation column on the annual cost. The results proved that the semicontinuous system is the best setup in terms of total annual costs and energy requirements. 相似文献
5.
In this paper, we introduce an optimization strategy in order to comprehensively quantify the impact of availability and maintenance notions during the early stages of synthesis and design of a new natural gas combined cycle power plant. A detailed state-space approach is thoroughly discussed, where influence of maintenance funds on each component's repair rate is directly assessed.In this context, analysis of the reliability characteristics of the system is centered at two designer-adopted parameters, which largely influence the obtained results: the number of components which may fail independently at the same time, and the number of simultaneous failure/repair events.Then, optimal solutions are evaluated as the availability-related parameters and the amount of resources assigned for maintenance actions are varied across a wide range of feasible values, which enable obtaining more accurate and detailed estimations of the expected economic performance for the project when compared with traditional economic evaluation approaches. 相似文献
6.
7.
ABSTRACTThis paper proposes the multiple-hypotheses image segmentation and feed-forward neural network classifier for food recognition to improve the performance. Initially, the food or meal image is given as input. Then, the segmentation is applied to identify the regions, where a particular food item is located using salient region detection, multi-scale segmentation, and fast rejection. Then, the features of every food item are extracted by the global feature and local feature extraction. After the features are obtained, the classification is performed for each segmented region using a feed-forward neural network model. Finally, the calorie value is computed with the aid of (i) food volume and (ii) calorie and nutrition measure based on mass value. The experimental results and performance evaluation are validated. The outcome of the proposed method attains 0.947 for Macro Average Accuracy (MAA) and 0.959 for Standard Accuracy (SA), which provides better classification performance. 相似文献
8.
加工高酸油品加氢反应进料加热炉炉管的选材 总被引:1,自引:0,他引:1
许妍冰 《石油化工设备技术》2006,27(3):44-47
论述了加氢装置反应进料加热炉炉管经常出现的晶间腐蚀的形成原因、控制方法以及近年来油品中出现的环烷酸对炉管的腐蚀影响,并结合工程实例,讨论了综合考虑强度和防止这两种腐蚀的炉管选材的问题。 相似文献
9.
10.