全文获取类型
收费全文 | 19493篇 |
免费 | 778篇 |
国内免费 | 838篇 |
专业分类
电工技术 | 516篇 |
技术理论 | 14篇 |
综合类 | 1917篇 |
化学工业 | 4969篇 |
金属工艺 | 871篇 |
机械仪表 | 849篇 |
建筑科学 | 1867篇 |
矿业工程 | 1108篇 |
能源动力 | 694篇 |
轻工业 | 2462篇 |
水利工程 | 156篇 |
石油天然气 | 573篇 |
武器工业 | 25篇 |
无线电 | 739篇 |
一般工业技术 | 1476篇 |
冶金工业 | 1755篇 |
原子能技术 | 73篇 |
自动化技术 | 1045篇 |
出版年
2024年 | 44篇 |
2023年 | 215篇 |
2022年 | 442篇 |
2021年 | 520篇 |
2020年 | 540篇 |
2019年 | 365篇 |
2018年 | 318篇 |
2017年 | 420篇 |
2016年 | 457篇 |
2015年 | 443篇 |
2014年 | 1110篇 |
2013年 | 1020篇 |
2012年 | 1181篇 |
2011年 | 1294篇 |
2010年 | 1189篇 |
2009年 | 1046篇 |
2008年 | 889篇 |
2007年 | 1262篇 |
2006年 | 1368篇 |
2005年 | 1174篇 |
2004年 | 986篇 |
2003年 | 948篇 |
2002年 | 806篇 |
2001年 | 671篇 |
2000年 | 540篇 |
1999年 | 414篇 |
1998年 | 357篇 |
1997年 | 258篇 |
1996年 | 179篇 |
1995年 | 173篇 |
1994年 | 108篇 |
1993年 | 84篇 |
1992年 | 60篇 |
1991年 | 43篇 |
1990年 | 33篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 21篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1959年 | 4篇 |
1957年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
《Journal of the European Ceramic Society》2020,40(14):4792-4798
The multilayer ceramic composites (MLC) consist of two ceramic materials insoluble in each other and sequentially piled in a symmetric manner whereas they can be divided into two groups: multilayer composites with weak interfaces and composites with strong interfaces. The graphene added multilayer ceramic sandwich (GMCS) composite was developed. The multilayer stack of Si3N4 with 5 and 30 wt% graphene addition were stratified in sandwich structure. So formed multilayer stacks with 5 and 7 layers were sintered by hot issostatic pressing (HIP). The homogenity of graphene addition, the effect of layered structures and the position of layers with lower and higher graphene content on the final properties were studied. 相似文献
13.
The development of a sustainable energy system throughout an enterprise is a complex task, which requires an agile holistic approach. Such an approach needs to include a variety of objectives including energy strategy formation and strategic decision-making, which are directly related to the analysis and management of the main areas of sustainable development:The economic, technological, environmental, and social. These multidimensional requirements of sustainability are often difficult to achieve within the enterprise, because these aspects are interrelated and influenced by various internal and external environment factors. This paper first reviews the main challenges for an energy system, and then demonstrates how a strategic agile enterprise architecture driven approach could effectively guide the sustainable energy system development. The study presented in this paper provides a holistic approach that contributes to the advancement and usage of literature dealing with issues of sustainable energy system development and agile enterprise architecture, which has not been discussed before to any great extent. 相似文献
14.
The results of formation of the high density effective scintillation ceramics consisting of two compounds of the cubic symmetry, LuAG:Ce and Lu2O3 (LuAG:Ce + Lu2O3), are described. Powders of a novel material LuAG:Ce + Lu2O3 were synthesized by co-precipitation method. The introduction of Lu2O3 into LuAG:Ce was shown to increase the density of the ceramics obtained and modify its scintillation properties. 相似文献
15.
The next-generation systems are expected to be largely cyber–physical systems (CPSs) that autonomously control physical processes, through sensors and actuators typically in real-time feedback and cooperative control loops distributed among physical and cyber environments. The rapid technological advancements enhance the smartness of these CPSs, pushing their boundaries of performance and efficiency by embedding new information and communication technologies. However, to what extent CPSs should be smarter so that they do not compromise safety and security of safety critical systems? is an open research question. Towards this goal, the purpose of this study is to establish a grounded theory to analyse what makes these systems smart? and eventually, how to find a balance between smartness and safety risks? In this precinct, this article aims to develop a conceptual framework, define the dimensions and derive the characteristics that make CPSs smart. The proposed approach combines an automated informetric and systematic analysis of literature pertinent to the topic of smartness across anthropology, science, engineering and technology. The analysis of a case study building and the discussions presented herein support the connection between the existing understanding of CPSs and smartness offered by the building design approach in urban environment. 相似文献
16.
The Indian telephony industry is a diverse platform for product and service in customer value perception. The present study organizes and synthesizes the varied research streams for developing a customer value delight (CVD) framework for marketing decisions like segmentation and targeting. The conceptual framework is developed by using ten-value predictor variables and customer delight through divergent viewpoints identified from previous studies. The significance of the segregation proposition is tested through discriminant analysis in three different dimension runs i.e. delight, gender, and marital category. The scholarship behind the study provides insight into an imperative issue of segregating customer delight by perceived value predictors in categories. The perceptual mapping and vector magnitude analysis of value predictors were performed to club customers in two categories of Mid-Town (low/moderate delight) and Extremes (high delight). The analysis rigorously supports the discriminating power of perceived price, perceived benefit, and self-congruity. The salience of study unlocks psychographic and demographic perceptual maps of customer delight with its perceived value predictors for strategic and tactful planning in the mobile industry. 相似文献
17.
《Ceramics International》2022,48(17):24953-24964
18.
《Ceramics International》2022,48(8):10506-10515
The search for materials and methods capable of reducing human impacts on the environment is of utmost importance nowadays. This study's primary purpose was to analyze the technical feasibility of ceramic composites production utilizing Fundão Dam's Iron Ore Tailings (IOT), Blast Furnace Slag (BFS) from charcoal, and Foundry Sand (FS) as partial substitutes for the traditional raw materials – sand and clay – for application in building industry materials. The composites were molded in rectangular specimens and fired at temperatures of 900, 950, 1000, 1050, and 1200 °C. The developed materials were analyzed and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TGA), and Differential Thermal Analysis (DTA). The obtained materials had flexural strength modulus of up to 12.19 MPa, water absorption ranging from 2 to 22%, linear shrinkage ranging from 0.02 to 6.50%, and apparent density ranging from 2.03 to 1.63 g/cm3. The study of the internal structure formation process revealed the formation of amorphous structures in the composites. The results demonstrated that these waste materials may be jointly used in construction materials, contributing to the reduction of natural resource extraction, besides enabling their correct disposal, minimizing environmental impacts, and improving the life quality of the surrounding communities. 相似文献
19.
Pressure-assisted infiltration was used to synthesize SiC/Al 6061 composites containing high weight percentages of SiC. A combination of PEG and glass water was used to fabricate SiC preforms and the effect of the presence of glass water on the microstructure and mechanical properties of the preforms was evaluated by performing compression tests on the preforms. Also, the compressive strength and the hardness of the SiC/Al composites were investigated. The results revealed that the glass water improved the compressive strength of the preforms by about five times. The microstructural characterization of the composites showed that the penetration of the aluminum melt into the preforms was completed and almost no porosity could be seen in the microstructures of the composites. Moreover, the composite containing 75 wt% SiC exhibited the highest compressive strength as well as the maximum hardness. The results of the wear tests showed that increasing the SiC content reduces the wear rate so that the Al-75 wt% SiC composite has a lower wear rate and a lower coefficient of friction than those of Al-67 wt% SiC composite. This indicated higher wear resistance in these composites than the Al alloy due to the formation of a tribological layer on the surface of the composites. 相似文献
20.