全文获取类型
收费全文 | 46909篇 |
免费 | 5186篇 |
国内免费 | 3003篇 |
专业分类
电工技术 | 1571篇 |
技术理论 | 2篇 |
综合类 | 4104篇 |
化学工业 | 4282篇 |
金属工艺 | 2613篇 |
机械仪表 | 3419篇 |
建筑科学 | 1016篇 |
矿业工程 | 1525篇 |
能源动力 | 569篇 |
轻工业 | 5401篇 |
水利工程 | 727篇 |
石油天然气 | 1504篇 |
武器工业 | 896篇 |
无线电 | 8004篇 |
一般工业技术 | 3616篇 |
冶金工业 | 2050篇 |
原子能技术 | 373篇 |
自动化技术 | 13426篇 |
出版年
2024年 | 98篇 |
2023年 | 664篇 |
2022年 | 1001篇 |
2021年 | 1355篇 |
2020年 | 1343篇 |
2019年 | 1026篇 |
2018年 | 973篇 |
2017年 | 1319篇 |
2016年 | 1464篇 |
2015年 | 1760篇 |
2014年 | 2545篇 |
2013年 | 2562篇 |
2012年 | 3221篇 |
2011年 | 3609篇 |
2010年 | 2675篇 |
2009年 | 2758篇 |
2008年 | 2841篇 |
2007年 | 3387篇 |
2006年 | 2992篇 |
2005年 | 2681篇 |
2004年 | 2253篇 |
2003年 | 2082篇 |
2002年 | 1675篇 |
2001年 | 1332篇 |
2000年 | 1208篇 |
1999年 | 898篇 |
1998年 | 796篇 |
1997年 | 730篇 |
1996年 | 646篇 |
1995年 | 524篇 |
1994年 | 485篇 |
1993年 | 413篇 |
1992年 | 318篇 |
1991年 | 251篇 |
1990年 | 235篇 |
1989年 | 206篇 |
1988年 | 143篇 |
1987年 | 82篇 |
1986年 | 69篇 |
1985年 | 86篇 |
1984年 | 68篇 |
1983年 | 78篇 |
1982年 | 58篇 |
1981年 | 42篇 |
1980年 | 31篇 |
1979年 | 29篇 |
1978年 | 19篇 |
1977年 | 24篇 |
1976年 | 13篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
With the rapid development in business transactions, especially in recent years, it has become necessary to develop different mechanisms to trace business user records in web server log in an efficient way. Online business transactions have increased, especially when the user or customer cannot obtain the required service. For example, with the spread of the epidemic Coronavirus (COVID-19) throughout the world, there is a dire need to rely more on online business processes. In order to improve the efficiency and performance of E-business structure, a web server log must be well utilized to have the ability to trace and record infinite user transactions. This paper proposes an event stream mechanism based on formula patterns to enhance business processes and record all user activities in a structured log file. Each user activity is recorded with a set of tracing parameters that can predict the behavior of the user in business operations. The experimental results are conducted by applying clustering-based classification algorithms on two different datasets; namely, Online Shoppers Purchasing Intention and Instacart Market Basket Analysis. The clustering process is used to group related objects into the same cluster, then the classification process measures the predicted classes of clustered objects. The experimental results record provable accuracy in predicting user preferences on both datasets. 相似文献
52.
53.
为研究加工方式对玉筋鱼干风味的影响,实验按加工方式分为加盐煮制冷风干燥(boiling in salt solution followed by cold air drying,SCC)组和冷风干燥(cold air drying,CD)组。采用电子鼻技术、气相离子迁移谱(gas chromatography-ion mobility spectroscopy,GC-IMS)技术、氨基酸自动分析技术、高效液相色谱技术测定玉筋鱼干中的风味成分。结果表明,不同加工方式制作的玉筋鱼干在气味、滋味方面存在显著差异。电子鼻、GC-IMS技术均能区分不同工艺制作的玉筋鱼干气味,采用GC-IMS技术共分析出68 种挥发性成分,庚醛、戊醛、3-甲基丁醛对玉筋鱼干独特风味的形成有重要影响,其中3-甲基丁醛源自CD工艺,其区别于SCC工艺气味的关键物质。玉筋鱼干中的主要鲜味氨基酸是Glu,主要呈味核苷酸是肌苷酸;CD组玉筋鱼干中的鲜味氨基酸和甜味氨基酸含量占总游离氨基酸的比重高于SCC组,同时CD组滋味活性值、味精当量值均高于SCC组,所以仅采用CD工艺制作的玉筋鱼干滋味优于加盐煮制后CD工艺制作的玉筋鱼干。 相似文献
54.
Anne Gabrielle Mathot Florence Postollec Ivan Leguerinel 《Comprehensive Reviews in Food Science and Food Safety》2021,20(1):840-862
Production and world consumption of spices are constantly increasing. Although the antimicrobial properties of some spices are well documented, their use in the agri-food industry is also responsible for microbial contamination and spoilage. Bacterial spores introduced by spices can withstand different preparation processes, particularly thermal treatments, leading to food alterations during storage. This review brings together data from the literature about the prevalence and concentrations of spore-forming bacteria in all commercially available spices. The sporeformers found in spices belong mainly to the genera Bacillus and Clostridium. Such contaminations are very common and sometimes reach high levels, as in pepper and turmeric. Bacillus licheniformis and Bacillus cereus are the most frequently detected species. Studying the harvesting, processing, and storage procedures for spices provides elements to explain why high prevalence and concentrations are observed. Spices are mostly produced in developing countries on small farms using traditional production methods. Spices become contaminated by bacterial spores in two main ways: by contact with soil during harvesting or drying, as for pepper, or by cross-contamination during the water-cooking step, as for turmeric. From these observations, we propose some recommendations. Different methods that can be used to eliminate bacterial spores from spices are presented indicating their efficiency and the limitations of their use. 相似文献
55.
J. Vinodhini J. Mayandi R. Atchudan P. Jayabal V. Sasirekha J.M. Pearce 《Ceramics International》2019,45(4):4667-4673
Titanium dioxide (TiO2) nanostructures (nanorods and nanoparticles) were prepared using a low-cost microwave irradiation method from a polyol medium of glycerol. Titanium glycerolate and TiO2 powders were obtained in the glycerol medium for the first time with four different power densities (240?W, 480?W, 720?W, 960?W) of irradiation using a domestic microwave oven of 2.45?GHz, to understand the impact of power on morphology tuning. The structural and morphological features of the titanium glycerolate and TiO2 powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Raman spectra analysis. The TiO2 was successfully used in the fabrication of photovoltaic devices and as a proof-of-concept binder free paste was prepared and successfully employed for photo-anode using screen printing on the fluorine-doped tin oxide substrate. 相似文献
56.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
57.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object. 相似文献
58.
The enormous magnitude and variety of microwave applications in household, commercial and industrial food processing creates a strong motivation for improving the energy efficiency and hence, sustainability of the process. This review critically assesses key energy issues associated with microwave food processing, focusing on previous energy performance studies, energy performance metrics, standards and regulations. Factors affecting energy-efficiency are categorised into source, load and source-load matching factors. This highlights the need for highly-flexible and controllable power sources capable of receiving real-time feedback on load properties, and effecting rapid control actions to minimise reflections, heating non-uniformities and other imperfections that lead to energy losses. A case is made for the use of solid-state amplifiers as alternatives to conventional power sources, magnetrons. By a full-scale techno-economic analysis, including energy aspects, it is shown that the use of solid-state amplifiers as replacements to magnetrons is promising, not only from an energy and overall technical perspective, but also in terms of economics. 相似文献
59.
60.
Modelling flow phenomena and their related weathering effects is often cumbersome due their dependence on the environment, materials and geometric properties of objects in the scene. Example‐based modelling provides many advantages for reproducing real textures, but little effort has been devoted to reproducing and transferring complex phenomena. In order to produce realistic flow effects, it is possible to take advantage of the widespread availability of flow images on the Internet, which can be used to gather key information about the flow. In this paper, we present a technique that allows the transfer of flow phenomena between photographs, adapting the flow to the target image and giving the user flexibility and control through specifically tailored parameters. This is done through two types of control curves: a fitted theoretical curve to control the mass of deposited material, and an extended colour map for properly adapting to the target appearance. In addition, our method filters and warps the input flow in order to account for the geometric details of the target surface. This leads to a fast and intuitive approach to easily transfer phenomena between images, providing a set of simple and intuitive parameters to control the process. 相似文献