全文获取类型
收费全文 | 8131篇 |
免费 | 458篇 |
国内免费 | 48篇 |
专业分类
电工技术 | 141篇 |
综合类 | 54篇 |
化学工业 | 2085篇 |
金属工艺 | 178篇 |
机械仪表 | 177篇 |
建筑科学 | 371篇 |
矿业工程 | 34篇 |
能源动力 | 313篇 |
轻工业 | 1193篇 |
水利工程 | 103篇 |
石油天然气 | 89篇 |
武器工业 | 12篇 |
无线电 | 490篇 |
一般工业技术 | 1110篇 |
冶金工业 | 788篇 |
原子能技术 | 55篇 |
自动化技术 | 1444篇 |
出版年
2024年 | 13篇 |
2023年 | 75篇 |
2022年 | 255篇 |
2021年 | 323篇 |
2020年 | 228篇 |
2019年 | 222篇 |
2018年 | 266篇 |
2017年 | 256篇 |
2016年 | 281篇 |
2015年 | 246篇 |
2014年 | 331篇 |
2013年 | 611篇 |
2012年 | 490篇 |
2011年 | 655篇 |
2010年 | 430篇 |
2009年 | 390篇 |
2008年 | 395篇 |
2007年 | 364篇 |
2006年 | 290篇 |
2005年 | 216篇 |
2004年 | 241篇 |
2003年 | 243篇 |
2002年 | 252篇 |
2001年 | 143篇 |
2000年 | 131篇 |
1999年 | 127篇 |
1998年 | 240篇 |
1997年 | 165篇 |
1996年 | 101篇 |
1995年 | 89篇 |
1994年 | 85篇 |
1993年 | 70篇 |
1992年 | 35篇 |
1991年 | 30篇 |
1990年 | 34篇 |
1989年 | 32篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 31篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 25篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1978年 | 6篇 |
1977年 | 14篇 |
1976年 | 28篇 |
1975年 | 9篇 |
1974年 | 8篇 |
排序方式: 共有8637条查询结果,搜索用时 15 毫秒
111.
Alper Sarıoğlan Ömer Tunç Savaşçı Ayşe Erdem-Şenatalar Vu Thu Ha Gilbert Sapaly Younès Ben Taârit 《Catalysis Letters》2007,118(1-2):123-128
MFI type inorganic carrier was used in two different cationic forms, hydrogen and calcium respectively. MFI-supported molybdenum
and rhenium catalysts were prepared. The activities of the catalysts were compared for the aromatization reaction of methane.
Higher activity values were attained with the catalysts supported on HZSM-5. Aromatics were also observed with the catalysts
supported on CaZSM-5, despite their deficiency in acid sites. Highly dispersed rhenium is expected to be formed with the use
of the inorganic carrier in calcium form. On the other hand, lower reaction rates were observed with rhenium supported on
CaZSM-5, in spite of the improved dispersion of the active rhenium species on this catalyst. This was interpreted in terms
of the critical role of the acid sites in the conversion of methane to aromatics, compared to the improved dispersion of the
active metal. 相似文献
112.
Talita da Cunha Mattos Flávia Maria Santoro Kate Revoredo Vanessa Tavares Nunes 《Computers in Industry》2014
A business process is a set of activities performed in a coordinated manner within an organizational and technical environment that is aimed toward a business goal. The flexibility of a process is related to an understanding of the unexpected events that occur when people, systems and resources interact and require adjustments. Thus, business processes must be designed to respond to information about different events and their specificity. This information defines what the literature calls “context”. To broaden the perception of context in the case of a business process, this work proposes an approach to characterize the context of a business process activity in a given domain through conceptual models structured in layers. A case study was conducted to evaluate the proposal, which provided evidence of the applicability of the model. 相似文献
113.
114.
A topology optimization procedure is presented as a tool for determining the distribution of external strengthening of concrete slabs, using Carbon Fiber Reinforced Polymer (CFRP). Although the procedure is applied to slabs in this work, the technique can be used in any concrete structure to be reinforced. Numerical simulations are performed using the Finite Element Method, in combination with the automated topology optimization procedure, to indicate the optimal region for placement of the reinforcement. The influence of some aspects of the slab’s structural behavior on the optimization results is presented: concrete cracking, boundary conditions and reinforcement rate. A brief discussion is given of the similarity between the topology optimization results obtained by the maximum stiffness and ultimate strength criteria. Gains are found in the stiffness and strength of reinforced parts. A comparison with conventional reinforcement techniques demonstrates that topology optimization can be a useful tool for defining the region of reinforcement, allowing for material cost savings. 相似文献
115.
Antonio J. Jara Pablo Lopez David Fernandez Jose F. Castillo Miguel A. Zamora Antonio F. Skarmeta 《Personal and Ubiquitous Computing》2014,18(2):323-338
The application of Internet-enabled devices in the real world for the development of Smart Cities, environmental monitoring, bus tracking, and parking requires scalability, extensibility, and integration of emerging resources to reach a suitable ecosystem for data acquisition and interaction with citizens. Internet of things needs to offer efficient support for global communications and access to services and information. It needs to enable homogeneous and seamless machine-to-machine communication for different solutions and applications. This work presents an homogeneous and suitable mechanism for global resource discovery, device access for deployed smart objects in different scenarios, and sensors and devices from end users (participative sensing). The integration of legacy and sensors already available from smart buildings and smart objects is presented. For this purpose, a resolution infrastructure called “digcovery” is defined for maximizing efficiency and sustainability of deployments. Digcovery architecture offers the framework to allow users to register/include their own sensors into a common infrastructure and access/discover the available resources through mobile digcovery. Mobile digcovery exploits the context-awareness, geo-location, and identification technologies available in mobile platforms such as smartphones to discover, interact, and access the resources through its ElasticSearch engine. 相似文献
116.
Olivier Renoult Jean-Pierre Boilot Frédéric Chaput Renée Papiernik Liliane G. Hubert-Pfalzgraf Martine Lejeune 《Journal of the American Ceramic Society》1992,75(12):3337-3340
The sol–gel method has been developed for the preparation of pure Ba(Mg1/3 Ta2/3 )O3 ceramics. This involves the reaction of the heterometallic alkoxide Ta2 Mg(OEt)12 with hydrated barium hydroxide Ba(OH)2 ·8H2 O. Complete crystallization of the sol–gel-derived powder is achieved at 600°C, leading to a cubic perovskite type phase. After sintering at 1400°C (2–5 h), a trigonal cell arises from Mg–Ta ordering (the degree of order is greater than 0.9), and about 98.5% of the theoretical density is obtained. Preliminary microwave dielectric measurements show that the dielectric constant and the unloaded Q u of the ceramics are 24.2 and 6750, respectively, at 7.7 GHz. 相似文献
117.
118.
119.
120.
Jose Brisson 《Polymer Engineering and Science》2004,44(2):241-251
A review of past and present studies on orientation, rheology, and FTIR investigations on a hydrogen bond–forming polymer, poly(vinyl phenol) (PVPh), and its blends with polyethylene oxide (PEO), poly(methyl methacrylate) (PMMA), and poly(vinyl methyl ether) (PVME) is presented. Orientation is analyzed on the basis of deformation‐induced orientation and relaxation. For deformation, it is proposed from recent molecular modeling studies that orientation is similar for flexible backbone polymers of the types studied. To investigate relaxation, dynamical rheology analysis was performed previously on PVPh/PEO blends and global molecular weight between entanglement, Me, and chain friction ζ were estimated. Me remained close to that of the polymer forming the dominant network, a discontinuity being observed near 50 mole percent. Friction coefficient exhibited a maximum near that of the orientation function of this system. Near‐infrared measurements also showed a maximum in the number of interchain hydrogen bonds at this concentration, although broader than that of orientation or of the friction coefficient. For strongly interacting blends, it is proposed that a break in orientation behavior would be associated with the dominant network present, and therefore to Me, whereas ζ will dictate whether orientation decreases or increases in a given network domain. 相似文献