时态具有传达和强调信息“时-空”的重要作用。在英文摘要中巧妙应用不同的时态可以清晰、准确地表达作者的研究活动之间的先后次序以及相互之间的影响与逻辑关系。然而。有些论文的英文摘要存在着时态运用不恰当，甚至“混乱”的问题，在一定程度上会成为编辑部拒稿的一个理由，或造成其他学者（读者）对论文的“误解”。

学术论文的英文摘要常用“一般现在时”、“一般过去时”、“现在完成时”等三种时态，其分别适用于以下三种不同场合：

一、“一般现在时”通常用来阐述研究的背景、目的、内容、方法以及研究结果等。

例1: Many surface or underground coal fires are believed to exist worldwide. They keep burning and extend the area for many years more. The main objective of the study is to gain fundamental understanding of coal fire thermal characteristics and to design the thermal evolution model (Teuku Andika Rama Putra. Thermal Characteristics and Evolution Model of Coal Fire at Surface and Underground Coal Mine. Procedia Chemistry, Volume 19, 2016, Pages 687).

例2：This study demonstrates that DDR can improve the classification accuracy and allows the classification of gesture patterns with incomplete data, i.e., with the initial 25%, 50% or 75% of data representing a given dynamic gesture (DG) - time series of positional and hand shape data.... Experimental tests indicate that the use of PCA-based features result in a classification accuracy that is higher with 25% of gesture data (93% accuracy) than with 100% of gesture data (82% accuracy) (Miguel Simão, et al. Using data dimensionality reduction for recognition of incomplete dynamic gestures. Pattern Recognition Letters, Available online 6 January 2017).

例3：The new tested laser cladding design is capable of producing a sound coating with tunable hardness (from 360–430 HBN). This is possible through a new heat treatment procedure carried using a propane torch or induction heating at temperatures between 400 and 500°C and cooling rates below 3°C/s. The microstructure shows that the rail after laser cladding is fully pearlitic (F.C. Robles Hernández, et al. Laser cladding: The alternative for field thermite welds life extension. Materials & Design, Volume 111, 5 December 2016, Pages 165).

例4：Experimental results on different traffic scenes in practice demonstrate that this method has good robustness in complex traffic. Moreover, the proposed method performs better compared with some other methods (Xuan Wang, et al. Pedestrian abnormal event detection based on multi-feature fusion in traffic video. Optik - International Journal for Light and Electron Optics, Volume 154, February 2018, Pages 22).

二、“一般过去时”通常用来说明过去，特别是论文撰写之前某一时间的发现、实验过程、研究途径等。

例1: As part of the study described in this paper, investigations concerning the application of artificial intelligence methods for the identification of the aforementioned characteristics were carried out. The methods in question were used to identify the maceral groups of coal, i.e. vitrinite, inertinite, and liptinite. Additionally, an attempt was made to identify some non-organic minerals. The analyses were performed using pattern recognition techniques (NN, kNN), as well as artificial neural network techniques (a multilayer perceptron–MLP). The classification process was carried out using microscopy images of polished sections of coals. A multidimensional feature space was defined, which made it possible to classify the discussed structures automatically, based on the methods of pattern recognition and algorithms of the artificial neural networks. Also, from the study we assessed the impact of the parameters for which the applied methods proved effective upon the final outcome of the classification procedure (Mariusz Mlynarczuk, et al. The application of artificial intelligence for the identification of the maceral groups and mineral components of coal. Computers & Geosciences, Volume 103, June 2017, Pages 133).

例2：The laser cladding coatings were used in the past for rails but its life was terminated in their infancy (after approximately 3–4 MGT) due to the presence of un-tempered martensite that negatively affected the rail toughness (F.C. Robles Hernández, et al. Laser cladding: The alternative for field thermite welds life extension. Materials & Design, Volume 111, 5 December 2016, Pages 165).

例3: We examined the reclamation bonds for all coal mines in West Virginia and found that West Virginia faces significant gaps between counties and watershed for the amount of the secured funding for site-specific reclamation.... We also found that the areas most impacted by the amount of coal mining and reduced site-specific bonding are in the areas with the worst health outcomes (Sarah J., et al. Disparate impacts of coal mining and reclamation concerns for West Virginia and central Appalachia. Resources Policy, Volume 54, December 2017, Pages 1).

例4: In the last five years, more than 40 articles investigating adsorption of different classes of OCs by graphene and GO were published in peer-reviewed journals. Adsorption mechanisms were controlled by molecular properties of OCs (e.g., aromatic vs aliphatic, molecular size and hydrophobicity), characteristics of adsorbents (e.g., surface area, pore size distribution, and surface functional groups), and background solution properties (e.g., pH, ionic strength, surfactants, NOM, and temperature)(Gamze Ersan, et al. Adsorption of organic contaminants by graphene nanosheets: A review.Water Research, Volume 126, 1 December 2017, Pages 385).

三、“现在完成时”用来介绍已经完成的试验和研究，并强调其对现在（或将来）的影响。

例1：In the Appalachian region, coal mining has impacted 600,000 ha historically. While a return to forest would be a preferable postmining land use, due to the difficulty and higher costs of reforestation, many sites are reclaimed into non-native grasslands (R.M. Swab, et al. Native vegetation in reclamation: Improving habitat and ecosystem function through using prairie species in mine land reclamation. Ecological Engineering, Available online 24 June 2017).

例2: The international coal mining industry has experienced serious recent downturns, particularly in the electricity generating market, with steady declines projected into the future. In the United States, increased production from the natural gas sector has made coal-fired power production less competitive, and natural gas power plants are replacing aging coal-fired plants (Sarah J., et al. Disparate impacts of coal mining and reclamation concerns for West Virginia and central Appalachia. Resources Policy, Volume 54, December 2017, Pages 1).

例3: Graphene nanosheets (GNS) such as graphenes and graphene oxides (GOs) have been widely investigated as next-generation adsorbents in both water and wastewater treatment processes due to their unique physicochemical properties and their affinity towards different classes of organic contaminants (OCs) (Gamze Ersan, et al. Adsorption of organic contaminants by graphene nanosheets: A review. Water Research, Volume 126, 1 December 2017, Pages 385).